Coilguns and EM launchers
Dez Akin
fly up fuel, raw material, and volitiles aren't floated more. It seems
like logistically its easier to set up an earth based mass driver that
fires off every couple of minutes a new compliment of fuel or water up
to some orbital rendezvous site than to try to fly everything up there
with a rocket.
I mean, at 1000G plus, you can't fly people or anything fragile, but
it seems like it would still make sense for a lot of stuff we're
flying up there.
So what are the technical problems with coilguns as launchers? Can you
just make the series of coils longer or does switching speed become a
problem?
And would the economics of such an infrastructure add up or is it dead
in the water?
Ian Stirling
> I was wondering why the idea of earth based mass drivers as a way to
> fly up fuel, raw material, and volitiles aren't floated more. It seems
> like logistically its easier to set up an earth based mass driver that
> fires off every couple of minutes a new compliment of fuel or water up
> to some orbital rendezvous site than to try to fly everything up there
> with a rocket.
>
> I mean, at 1000G plus, you can't fly people or anything fragile, but
> it seems like it would still make sense for a lot of stuff we're
> flying up there.
>
> So what are the technical problems with coilguns as launchers? Can you
> just make the series of coils longer or does switching speed become a
> problem?
Everything becomes a problem.
Sectional density is a problem, you'r going to need a density of well over
10000Kg/m^2 to get to space with anything close to the exit speed.
With a density of 1, this is 10m long.
With a L/D ratio of 5:1, this is a volume of some 30 cubic meters, and maybe
40 tonnes.
Assuming 1000G, that's 4*10^7N, and if the exit speed was 10Km/s, that's
4*10^11W, 400Gw.
Lot of power.
And then you have the hypersonic shockwave from the bow of the projectile.
And you then need a kick motor to circularise the orbit, and keep it in
space, a guidance system, a rendevous/docking system, ...
Then you've got the awkward fact that you can't fire along one bearing
every few minutes and get into the same orbit, as the earth turns.
Swiveling and raising a 5Km long gun is going to be really interesting.
And even if you can point and aim the gun, as well as varying the speed,
it only helps a bit.
It seems like such a nice idea, but then the numbers start getting
in the way.
You can make things a lot easier by only launching at mach 5 or so, but
then the awkward question arises of why you'r doing this, when the rocket
has now to make up 80% of the velocity of its own, and now also has to
be braced to take several-many times the G it normally does.
Ross A. Finlayson
Hi,
Coilgun launch systems actually seem to many to be a feasible idea.
NASA calls the technology "tested".
The biggest issue against seems to be the sonic boom that it emits.
I remember being a little kid and hearing a sonic boom, oh, every
couple of days or month or so, then you look into the sky for the
contrail, or sometimes you can see the contrail before the boom.
Anyways it was enjoyable to hear sonic booms.
There are vast expanses of land even in America that would allow
something that size to be physically remote from communities by tens
of miles, for example federal reservations currently used for target
practice. That way the sonic boom would be minimal to people that can
hear it.
There have been animal habitats examined near sources of regular loud
noises, the animals quickly learn to not associate the sound with
danger and return to their normal patterns. That doesn't mean
high-powered sonar doesn't deafen whales and drive them to beach
themselves, it just means deer and bunnies don't flinch when cannons
go off regularly.
A mass driver big enough to launch something bigger than an atomic
nucleus is a big installation. We've been talking about one in the
thread "Moon Base baby steps", and a working idea of one is six miles
long, and about fifteen or twenty feet wide, for hundreds of G's.
Also, searching sci.space.* will result in many other discussions of
Earth based mass drivers.
The cost of launching ten thousand metric tons to orbit and beyond
with the coilgun is orders of magnitude less than orders of magnitude
less than current rocketry methods.
You seem to have addressed the major technical point of whether the
coilgun can switch fast enough, that is claimed by one source of
hundreds that I have browsed on the Internet these past few days.
This is using the coilgun and not the moving field. I don't know the
answer to that. This is using the coils to emulate the Lorentz field.
http://www.padrak.com/ine/NEWELBOOK.html (<- Nonsense?)
I think electromagnetic launch systems are actually a critical part of
an adequate space program. As a new endeavor, they would offer the
benefits of increased research into the field of those applicable
technologies, including electromotive force, high-G electronics,
hypersonic ballistics, and as a working system would offer a realistic
expectation of success in a moon base.
Support the Earth to Orbit Mass Driver!
Ross F.
gideon0223
gun scaled up could do the job; there are many web references on
this.
The problem seems to be the fixed orbit inclanation of such
a system, be it coil or gas based. Also I believe that both types of
systems need an orbital kick stage to insert them into a circular
orbit. The costs of building a gun that achieves near orbital
velocites at the muzzle just isnt effective economically.
Although there are at least one company actively researching the use
of gun launching to orbit:
http://www.columbiad.ca/industrial/
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G EddieA95
>something that size to be physically remote from communities by tens
>of miles, for example federal reservations currently used for target
>practice. That way the sonic boom would be minimal to people that can
>hear it.
But what is downrange of these locales? You have to launch out to sea to be
safe in casr a coil blows and Ve is not reached, yet most of these "open
spaces" are well over 2000Km west of the coastline.
G EddieA95
>fly up fuel, raw material, and volitiles aren't floated more.
Because the capital investment of such a gun is huge, and up to now there has
been no demand for bulk delivery into LEO. Raw material is needed only if you
are building lots of stuff from scratch; we aren't. Fuel is useful if you've
got ships in orbit to burn it; we don't.
Ross A. Finlayson
> Dez Akin <dez...@usa.net> wrote:
> > ...
Hi,
Hey, that's interesting. I'm trying to figure out what you mean by
that, I'm not sure I understand.
Abou the sectional density, you seem to be describing how dense the
payload pod has to be to overcome air resistance on its way out
without appreciable deformation as the air pressure on the leading
edges would be extremely high and deceleration from wind resistance.
The air pressure there, with the Pv=nrt, is part of the problems, the
temperature rapidly rises until the payload gets really hot until
melting or exploding point.
Is there any difference between a hypersonic shockwave and a regular
supersonic shockwave? Presumably there is, escape velocity is greater
than Mach 20. Hypersonic is greater than Mach 5, supersonic greater
than Mach 1: 770 mph at sea level.
The pod is designed for the minimal aerodynamic profile at launch, it
doesn't have to a lifting body, the drag coefficient should be able to
go to some 0.05, although that number is meaningless to me, the point
is that it can be designed to have a minimal aerodynamic profile.
Two tonnes, ten tonnes, forty tonnes (metric tons), the pod has to be
heavy to slice through the atmosphere.
You bring the point that the Earth is flying through the Universe at
fantastic speeds and thus any launch would be different than any
other. This can be mitigaated somewhat by launching, say, at the same
time each day. If the pod is launched at dusk, northwards from the
northern hemisphere, Earth's solar rotatation would help carry it away
from the pod. As well, the same thing is true for rocket launches,
each is different, what with a new rocket each time or the space
shuttle once a year, if that. The extra-orbital electromagnetic
launcher is a large, fixed emplacement.
I agree that the pod would need control systems and avionics to be any
good once past Earth's gravity well, but these can probably be
hardened to survive some hundreds of G's. Artillery hardened
electronics and explosive fuses already survive hundreds and thousands
of G's, to explode. Mass produced, they may be economically
preferable to conventional launch methods, for hardened or inert
payloads. The payload flexibility allows special use control systems,
ones that may be able to operate out beyond Earth's gravity well, a
major computational simplification compared to escaping Earth's
gravity.
Four hundred gigawatts is a lot of power. Some of the power processed
by the EM launcher may be recycleable. Reuse, reduce, recycle. It
definitely takes power to launch things into space. Power is force
over time.
Assume you're tasked with solving the problems you mention. How are
those problems solved?
Ross F.
Pete Lynn
news:20040201230804...@mb-m29.aol.com...
There is an argument that either way, you need CATS for people and low
acceleration tolerant freight, and if you have that, then you have it
for raw materials in general, and so earth based high acceleration mass
launchers are to some extent, superfluous. Besides, extra terrestrial
raw material sources have far greater long term potential at far lower
cost and would soon follow CATS, making the original earth mass driver
uneconomic.
Pete.
Ross A. Finlayson
> You dont' have to use a rail or coil gun at all a "simple" light gas
> gun scaled up could do the job; there are many web references on
> this.
>
> The problem seems to be the fixed orbit inclanation of such
> a system, be it coil or gas based. Also I believe that both types of
> systems need an orbital kick stage to insert them into a circular
> orbit. The costs of building a gun that achieves near orbital
> velocites at the muzzle just isnt effective economically.
>
> Although there are at least one company actively researching the use
> of gun launching to orbit:
>
>
> http://www.columbiad.ca/industrial/
>
The space-tech mailing list, the backbone of sci.space.tech, has a
wealth of discussion of Earth to orbit railgun and coilgun technology.
One marked proponent of the railgun or coilgun from at least the late
'80's is one Paul F. Dietz.
http://www-2.cs.cmu.edu/afs/cs.cmu.edu/user/mnr/st/std026
A lot of this discussion has already taken place. Discover magazine
had articles about it, the railgun to space, in 1989. The above
reference quotes 300 million and 7 year design/build timeframe, with
1000 kg projectiles, back in the late '80's.
http://www.google.com/search?q=+railgun+OR+coilgun+site%3Awww-2.cs.cmu.edu
Henry Spencer there, back then, rightly promotes multiple launch
technology development tracks. Support ram charger, hydrogen/gas
cannon, S/HARP, laser, and other launch systems that don't depend on
antigravity, nanotechnology, or skyhooks. Their development costs are
nominal compared to deploying boondoggles. Where one pans out, it
scales right to offer the necessary item for the use of space: cheap,
reliable, access to space.
We might consider the "augmented railgun" instead of the coilgun.
That's about the coil switching issue. Back in 1989, Dietz suggests
one use explosive switches or quenched superconductors, for some 60
millisecond discharge interval timing in discussion of the paper of
Palmer and Dabiri, from January 1989 IEEE Trans. on Magnetics. Also
there is said to be much information about railguns in other
odd-numbered year'ed IEEE Trans. on Magnetics.
http://ieeexplore.ieee.org/xpl/toc_print.jsp?isNumber=897&page=4
That listing leads to consider the ARDEC electromagnetic launch
facility, the Army small-bore hypervelocity electromagnetic launcher
research facility. The military has a variety of funded research
projects on electromagnetic launching of stuff, such as EMALS, part of
some multi-billion dollar program to replace steam catapults on
aircraft carriers with electromagnetic catapults.
http://www.utexas.edu/research/cem/programs/pulsed_ac.html
Anyways that's a somewhat different context than launching cargo pods
to the moon from Earth, but it is apparent that the concepts under
electromagnetic launch are under institutional development and
refinement and much expertise exists to be tapped.
"Boom!" "What was that?" "Forty thousand kilograms en route to the
Moon." "Boom!" "Oh."
Rocketry is great, it has it uses. So does an Earth-to-orbital mass
driver.
It was the train that opened America to coast-to-coast development and
expansion, at a large initial investment. A hundred some years later,
more commerce takes place on the roads via fleets of cargo containers
on 18 wheels, and the trains still run.
The Earth to orbital mass driver could cost _less_ in initial
investment than new rocket systems. It's good the Atlas blueprints
are not lost.
Say the Moonbase needs 2000 (metric) tons of materials, a year (or
month or day). That's only a hundred twenty-ton rocket launches. It
would take two hundred launches of a ten ton mass driver, or a
thousand launches of a two ton mass driver or two ton payload rocket.
If the rocket launches cost fifty million apiece, twenty ton payloads
out of Earth's gravity well, that's five billion for launch. Some
1-2% of the highest reliability current rocket launches fail.
People have been saying "Moonbase 2020, Mars 2030" since the 70's.
Those goals are old hat.
Wiki has an entry for mass driver:
http://en.wikipedia.org/wiki/Mass_driver
That describes two sections of the mass driver, a maximum acceleration
section and a constant acceleration section. In the maximum
acceleration sections the coils are equidistant and in the constant
acceleration section the coils are spaced further apart to continue to
apply the constant acceleration.
One design issue is how much curvature could be on the track.
Basically, the idea here is to consider after the track is laid with
its initial start position on essentially level ground, to simply add
track and coils and reprogram the timing system to simply add a few
extra kilometers of tracks, coils, and energizers to enable lower
acceleration launches.
Ross F.
Ross A. Finlayson
It's better to be thousands of feet above sea level to get out of the
atmosphere.
The probability of a coil failing could be minimized. A lot of this
is solid state electronics that doesn't have much to go wrong with it.
(No faulty solid rockets.)
I totally agree that failure would be bad. Say the pod halfway
through the launcher sharply impacts one of the coils (of the coilgun)
at Mach 15. The launcher would be almost completely ruined. Repair
would entail tearing up that ruined section of the track, determining
the cause of the failure and eliminating it, placing new coils, and
turning the lights back on.
If the pod went short, instead of escape velocity it might orbit back
to Earth. Here the idea is that the standard launch barely escapes
Earth's gravity well. The pod has a kick motor that can help it on
its way out. If it falls back to Earth, it might not have much more
than terminal velocity, and as oceans cover more than 2/3 of the
Earth's surface, it would probably land harmlessly in the water.
Airplanes fly coast-to-coast over densely inhabited areas. The last
time a large one accidentally crashed here in the States was in Queens
in 2001 a month or so after the 9/11 crimes. It landed in a
neighborhood and destroyed a city block and killed several, when the
tail fin fell off the plane. In Bhopal, India, a Union carbide plant
went wrong and thousands died, thousands more were permanently
injured, it was an industrial accident. Chernobyl lead to the death
of thousands. Yearly automobile fatalities tally around 40000 per
year on U.S. roads. The Space Shuttle has claimed fourteen.
It's certainly possible that rocketry costs could be lowered by
economies of scale for increased use of rocket launches, but that only
goes so far. Their reliability may increase, but they are very
complex mechanisms.
If you have CATS, cheap access to space, at less than three G's for
soft payloads, congratulations. What is it? What are some numbers of
it?
Discarding fantastic claims of nanotechnology for self-assemblers
launched in 2 kilogram payloads to the moon, the only way to construct
a Moon economy is to send lots of stuff to jumpstart it directly from
Earth, and Moon is not contributing for some thirty or forty years.
The Moon economy is the asteroid economy.
The capital investment for an actual Earth to space mass driver may
well be less than that of a fleet of expendables, with less
environmental impact, greater reliability, and a higher probability of
mission success.
There'll always be a market for less expensive access to space.
Consider the comparison of the Concorde to a supertanker. The
Concorde flew over the Atlantic at Mach 2+. A supertanker carries
millions of kilograms and takes six weeks to get there. Passenger
traffic often uses aircraft to cross oceans, and nobody would buy a
first class seat for a sack of onions, except insane people.
The problem with the coilgun is what happens when the hypersonic
projectile passes the plasma curtain over the launch tube into the
atmosphere and impacts high-altitude air at Mach 30. The compressed
air by the Ideal Gas Law is increased in pressure and as a result
temperature as it is displaced from the path of the pod. This can be
somewhat ameliorated by shaping the pod so that front edge pressure is
minimized, while maintaining linear flight. As well, heat shields may
protect the pod contents from the heat.
http://scienceworld.wolfram.com/physics/IdealGasLaw.html
Another issue with the beginning of the atmospheric phase or stage of
launch is the sudden decelerative shock. What I have in mind is some
kind of phase array that clears a path to cause a lower density of air
in the path of the pod, for example antennae some hundreds of meters
long past the snout that are polarized to attract ionized air
molecules in the path, contributing to the lightshow.
The control systems (standardized orbit kick booster, ion engine, or
sail array) have to survive launch along with the avionics and
communications, integrity heatshield, modular connect shell, payload,
and ballast. As they often do, then they guide the pod to the moon, a
relatively large target in the sky compared to "within a meter of the
Zvesta ISS module", where the pods deorbit and land in the pod
recovery field. There, the robotic multipurpose rovers and astronauts
on the moon collect their contents and add onto the Moon base and its
support, supply, and testbed facilities.
If it works right, then another is built, with an extended track, like
a stretch of bullet train track, but straight to the stars at 3 G's.
Getting back requires space planes. Splashdown is only for the hardy.
Ross F.
Ian Stirling
> Ian Stirling <ro...@mauve.demon.co.uk> wrote in message news:<ycfTb.1851$7j4.1...@wards.force9.net>...
>> Dez Akin <dez...@usa.net> wrote:
>> > ...
>> > So what are the technical problems with coilguns as launchers? Can you
>> > just make the series of coils longer or does switching speed become a
>> > problem?
>>
>> Everything becomes a problem.
>> Sectional density is a problem, you'r going to need a density of well over
>> 10000Kg/m^2 to get to space with anything close to the exit speed.
>> With a density of 1, this is 10m long.
> Hey, that's interesting. I'm trying to figure out what you mean by
> that, I'm not sure I understand.
>
> Abou the sectional density, you seem to be describing how dense the
> payload pod has to be to overcome air resistance on its way out
> without appreciable deformation as the air pressure on the leading
> edges would be extremely high and deceleration from wind resistance.
Not really.
Broadly speaking, if the projectile pushes through more air than
it weighs, then it'll be slowed lots.
This means that you probably can't make something that carries water
in a few kilo package, you need to send tonnes.
<snip>
> Is there any difference between a hypersonic shockwave and a regular
> supersonic shockwave? Presumably there is, escape velocity is greater
> than Mach 20. Hypersonic is greater than Mach 5, supersonic greater
More like mach 30.
> than Mach 1: 770 mph at sea level.
There is a hell of a lot more energy in it basically.
>
> The pod is designed for the minimal aerodynamic profile at launch, it
> doesn't have to a lifting body, the drag coefficient should be able to
> go to some 0.05, although that number is meaningless to me, the point
> is that it can be designed to have a minimal aerodynamic profile.
Unfortunately, hypersonic drag does not get that low, it does
not work like subsonic.
<snip>
> You bring the point that the Earth is flying through the Universe at
> fantastic speeds and thus any launch would be different than any
> other. This can be mitigaated somewhat by launching, say, at the same
Not quite.
The important fact is that the earth rotates, so that the orbit passes
over a different path over earth each day, only passing the same direction
going the same way once per day (roughly).
<snip>
> I agree that the pod would need control systems and avionics to be any
> good once past Earth's gravity well, but these can probably be
> hardened to survive some hundreds of G's. Artillery hardened
> electronics and explosive fuses already survive hundreds and thousands
> of G's, to explode. Mass produced, they may be economically
I was more referring to the structure.
The structure needs to be very heavy to take 1000G.
<snip>
> Four hundred gigawatts is a lot of power. Some of the power processed
> by the EM launcher may be recycleable. Reuse, reduce, recycle. It
> definitely takes power to launch things into space. Power is force
> over time.
None of it is recyclable.
That was the absolute minimum figure for the power used at the end of the
track, and all goes into the projectile at 100% efficiancy.
Lower efficiancy will increase power needs.
>
> Assume you're tasked with solving the problems you mention. How are
> those problems solved?
The easiest way is to go with another launch method.
This thing would cost many tens of billions to make.
It would only make sense if you have a need for a few hundred tons to
orbit a day of bulk materials.
This is quite a way from the current demand.
Kaido Kert
> fly up fuel, raw material, and volitiles aren't floated more.
If there were demonstrated sufficient demand for such on LEO, with
established prices, mass produced expendables or high flight rate RLVs
would pop up fast and probably put the mass driver guys out of
business even before it would be built.
If you happen to be a oddball billionare, please do put a obrital
staging facility up there, and announce that you are buying water,
heatshields, and kerosene in large quantities. You'd be doing a great
favor to many.
-kert
G EddieA95
>through the launcher sharply impacts one of the coils (of the coilgun)
>at Mach 15. The launcher would be almost completely ruined.
Worse still, if your 40T cannister plows into Houston at mach 10.
Ross A. Finlayson
Hi,
Okay, so you're saying the cost would be the problem.
The demand will meet supply.
The SAIC in the '80's said it would cost 300 million and take seven
years, before I heard that I thought it would take 500 million and
eight years, and you are saying it would take 10 billion (thousand
million) dollars. I suppose the SAIC, Science Applications
International Corp., is known to exaggerate and even lie, yet the
quote did say that their study said it would cost 300 million.
About the orbits, an orbit is a path of an Earth satellite, an item
whose inertial reference frame is dominated by the gravity of Earth
that does not contact the Earth. There's free software from
Analytical Graphics, stk.com, Satellite Toolkit, that allows some
amateur study of orbits and launch paths, there are also many
publishers of satellite tracking software. Study of how every solar
body "orbits" every other is called celestial mechanics, or orbital
mechanics, mathematical solution of the inertial behavior of multiple
objects from the effects of gravity is called an example of an n-body
problem. Keppler observed that planetary orbits are elliptical about
the Sun.
The structure is hardened, the coils are mounted on sectional plates
attached to pilings emplanted firmly in the bedrock.
http://www.google.com/search?q=%221000+G%27s%22+force
Power can be stored in flywheels to charge the magnets, except their
energy transfer rate is slow. The magnets don't need capacitors to
energize them, they are energized in sections long before they are to
affect the payload, then the payload is floated at constant velocity
into the range of the first bank of coils, then the timing device's
role is to deenergize the magnets as the pod reaches the coil. The
force between each coil and the payload is not impulsive, except for
when the field is released.
There are many issues with the hypersonic pod. Is it so that at those
velocities the gaseous medium reacts as a liquid medium? I guess that
would be hypervelocity aerodynamics.
The costing issue appears to be the problem. An Earth to orbit mass
driver has not yet been built, its costs are uncertain. Figures kited
around range from less than the cost of a shuttle launch to some
five-seven percent of NASA's budget for design and build over ten
years. Assuming it would work, upon completion it would offer launch
costs for hard payloads being hundreds or thousands times less than
rocketry. Let's examine these costs in light of NASA's mandate to
establish a viable human presence on the moon.
Say ground was broken for the mass drivers tomorrow, launches
commenced in eight years, and weekly payloads to the moon of two to
forty metric tonnes were stockpiled on the moon. These might include
hardened landers of various capacities, or as well hardened satellites
to orbit the moon, Mars, Europa, Io, Titan, Triton, Phobos, Deimos,
Mercury, Venus, etcetera. They also can include fuel and equipment
for Moon lander style return systems for human passengers.
Mission planners are meanwhile hard at work on the logistics and
technical demands of getting people to the moon, with the task of
setting up a moonbase. Launch systems are designed and retrofit. The
mission planners can design with the possibility of there being
hundred of tons of prepared supplies on the moon.
That is getting a little off-topic, this thread subject is "Coilguns
and EM launchers."
It's worth it so the Moon 'nauts can have eighty kph dunebuggies,
spare tires, and an operating room. It's worth it so we can get
massive orbiters in the hundreds for hundreds of times less than their
rocket launch. It's worth it so we can pelt that smirking Saturn with
discarded sardine tins. It's worth it because of the lightshow.
it's worth it because it's research would help drive low altitude
hypervelocity and high powered electromagnetics.
It's worth it because it's the cheapest way to space.
What are the costs and schedules of an Earth to orbit mass driver?
What's its product number?
Ross F.
Ian Stirling
> Ian Stirling <ro...@mauve.demon.co.uk> wrote in message news:<QtsTb.1942$7j4.1...@wards.force9.net>...
>> Ross A. Finlayson <r...@tiki-lounge.com> wrote:
>
>> >
>> > Assume you're tasked with solving the problems you mention. How are
>> > those problems solved?
>>
>> The easiest way is to go with another launch method.
>> This thing would cost many tens of billions to make.
>>
>> It would only make sense if you have a need for a few hundred tons to
>> orbit a day of bulk materials.
>> This is quite a way from the current demand.
>
> Hi,
>
> Okay, so you're saying the cost would be the problem.
>
> The demand will meet supply.
That'll be why I've got a string of supermodels craving my hot loving
standing outside waiting for me to answer the door then.
> The SAIC in the '80's said it would cost 300 million and take seven
> years, before I heard that I thought it would take 500 million and
> eight years, and you are saying it would take 10 billion (thousand
> million) dollars. I suppose the SAIC, Science Applications
From the little I can find online with those details, it seems to be
a much lower velocity one, that's largely rocket based.
<snip>
> There are many issues with the hypersonic pod. Is it so that at those
> velocities the gaseous medium reacts as a liquid medium? I guess that
> would be hypervelocity aerodynamics.
Not really.
It's just that things are different.
Take a glider for example.
The wind coming from its wings will have a temperature of some
thousandth of a degree higher (once it's all converted into heat).
This is at M0.15 or so.
At mach 30, it tends to come out several thousand degrees hotter.
<snip>
> Say ground was broken for the mass drivers tomorrow, launches
> commenced in eight years, and weekly payloads to the moon of two to
> forty metric tonnes were stockpiled on the moon. These might include
> hardened landers of various capacities, or as well hardened satellites
You've now got ot make a lander capable of some 2000m/s, capable of landing
the payload, and that can take 1000G at launch time, as well as some
tens of thousands of kelvin heat at launch.
> to orbit the moon, Mars, Europa, Io, Titan, Triton, Phobos, Deimos,
> Mercury, Venus, etcetera. They also can include fuel and equipment
> for Moon lander style return systems for human passengers.
<snip>
> It's worth it because it's the cheapest way to space.
Debatable.
I think a tether is probably cheaper.
Ross A. Finlayson
> Ross A. Finlayson <r...@tiki-lounge.com> wrote:
> >
> > The demand will meet supply.
>
> That'll be why I've got a string of supermodels craving my hot loving
> standing outside waiting for me to answer the door then.
>
> ...
>
> It's just that things are different.
> Take a glider for example.
> The wind coming from its wings will have a temperature of some
> thousandth of a degree higher (once it's all converted into heat).
> This is at M0.15 or so.
> At mach 30, it tends to come out several thousand degrees hotter.
>
> You've now got ot make a lander capable of some 2000m/s, capable of landing
> the payload, and that can take 1000G at launch time, as well as some
> tens of thousands of kelvin heat at launch.
>
>
> Debatable.
> I think a tether is probably cheaper.
When the pods land on the moon, keep in mind that they're hardened to
handle hundreds or thousands of G's, the launch track is 10
kilometers. So, they don't have to land particularly softly. The pod
plows into a pillow of dust in the lunar recovery field, the cloud of
which falls immediately back to the moon's surface.
The front side of the pod takes most of the heat. There is some
induction, but the front side of the pod is the heat shield. The heat
shield may be an ablative fairing, insulating the pod as it dissolves
away, and some figures I read somewhere on the Internet put it at 10%
of the pod's mass. I wonder if that's the correct figure. Maybe
that's where the SEDS guy came up with 90%. I think it would be
closer to ten percent.
Would you please explain how you arrived at your figure? Cursory
research tells me 10000 K is the heat of a metal-halide lamp element,
that doesn't oxidize because its bulb is evacuated, nor does it melt.
It's the air that gets to that temperature.
The heat would still cause problems for the liquid fuel kick motor,
ion motor or sail array, gyros or motion compensators, and other
control systems, comms and avionics, and also the payload. Tens of
thousands of Kelvins is an incredibly high temperature. At a speed of
some 12 km/s, the pod is out of the stratosphere in approximately five
seconds, and leaves the ionosphere in sixty seconds. The atmospheric
heating at the pressure front is highest immediately after launch and
decreases as the pod rises out of the atmosphere.
The heat would be the most immediate danger for the pressurized
liquids and gases, and from state change and the ideal gas law
rupturing those vessels upon heat shield failure, and shortly
dissolving the rest of the pod. A possible solid fuel insertion or
landing booster risks ignition.
The whole pod could be a heatshield with explosive separation. Then
there'd be the issue of dealing with the heatshield and pod contents
separately.
I come across a search engine of NASA technical reports.
That's pretty.
http://www.tech-db.ru/istc/db/pra.nsf/we/3070
http://www.aiaa.org/Participate/Uploads/2000%20HyTASP%20Hypersonic%20Technologies%20Report.PDF
Those might have information about high temperature heatshields.
Another problem with the whole atmosphere thing, assuming the
theoretical projectile exiting an evacuated tube at Mach 30, is that
it then hits the air. The behavior of the pod hitting the ground
level atmosphere at 8+ miles per second may be as one post put it just
like hitting a brick wall, yet, that is conjecture. The sudden
impulse G forces might be much more than those of the launch
apparatus. That leads into considerations of how to lower the air
density at the launch tube / free air interface.
The launch tube could have air in it, but the coils would be fighting
it and suffering from the heat. That still might be preferable to
sudden deceleration. The air pressure in the launch tube could be
variable.
The vacuum/air interface encounter might cause a large explosion
there, ruining a section of the track, the egress vacuum freeflight
zone, and some of the coils.
There might be radical heatshield designs which perhaps cause some
form of gaseous cavitation, decreasing drag, although drag seems not
the problem of pressure gradients. The ideal shape may simply be
pointed at the front end, the penetrator. While that may be the case,
the "sectional density" consideration has the ideal shape for that
consideration being a sphere. The pod may have fins, but it should
look more like a lozenge or a "Star Trek" torpedo.
The pod may be an active source of energy to discharge into its
immediate path power to shove the air molecules aside before it gets
there. If it could fly in a tunnel of vacuum to outer space
everything would be fine. Most means of decreasing air density in its
path would help, eg, the plasma sheath. At 12 km/s, more than 36000
feet per second, there's not much time to move the air molecules out
of its way.
So it seems the problem is with launching from our dense atmosphere.
Within that problem are problems: the ground level vacuum/air
interface and compressive atmospheric heat, and as well possible
unknowns of hypersonic "fluidity". I think the problem is the
air/vacuum interface, the camera shutter/plasma curtain.
There could be a series of increasingly dense/pressurized freeflight
zones/sections before the pod hit the open air.
So, we should build the Earth to orbit mass driver in miniature, and
launch test pods to see what happens.
What do you think about the pod being a sphere? How is remotely
affected air pressure? What happens when 10000 kg at 12 km/s goes
from near vacuum to 600 millibars, at 300K?
You say a tether would be cheaper. You get a discount on
"unobtainium"?
Good luck, have fun,
Ross F.
Ross A. Finlayson
like there may already be a facility to test items exposed to a Mach
30 shock wave, the Large Energy National Shock (LENS) tunnel.
http://www.cubrc.org/aerospace/aerospace_facility.html
That might work pretty well for testing the aerodynamic profile of the
pod at Mach 30, but I don't know if it also would help understand the
vacuum/air interface behavior. More specialized experimental testing
systems could be developed.
It seems clear that a hypothetical Earth to orbit mass driver for
cargo would offer some benefits. The launch costs would approach air
freight. Thousands of previously uneconomical extraorbital missions
would become worthwhile. As a ground based launch system, maintenance
and repair are greatly simplified. As a complement to rocketry launch
for soft payloads, the rocket launch facilities could concentrate on
safety and reliability of manned access to space. A realistic moon
base and as well any other requirement of large amounts of bulk,
refined materials from Earth, such as food, water, air, bouncy
castles, airlock components, rovers, landers, or fuel would be made
much more easily. As a working model of an Earth to orbit mass
driver, it would provide necessary research for eventually
constructing one with a longer, lower acceleration track and massier
payloads for high volume access to space from Earth.
The pod design may serve as a reasonable standard payload for rocket
based launch systems. Boost a pod with a rocket, it's already
designed to handle the launch forces, making for modularity and the
reuse of pod designs for various systems, and is built with
repurposeable control systems (cadmium ion engines, liquid fuel
rockets, solar sails) for sending the pods to the many points in the
solar system worthy a close-up view.
The costs are less than developing the rocket launch system with that
capacity. A mass driver with 2 tonne payloads about matches a rocket
with a two tonne payload, except you need only one mass driver
compared to a thousand rockets to put 2000 tonnes on the moon. Earth
rocket launch rates are currently more along the line of fifteen-fifty
per year, if that.
The capacity of a mass driver system may be much higher than rocket
systems. Assuming the pods are mass produced, where the pod is the
guidance/control system once past orbit, the mass driver could launch
thousands of times a month., and perhaps every twenty seconds.
The technical difficulties of the mass driver are not insurmountable,
hopefully. There is much research in hypervelocity and heat shielding
for the payloads. The systems of equations exactly defining the force
put on the payload by the coils is not only existant but also near
thresholds of new breakthrough. The constituent elements of the mass
driver are interchangeable components of materials available in large
supply.
The timeframe of construction of a mass driver is years, not decades.
Imagine you're an astronaut living on the moon. You live in a cramped
lander with four others. You're happy that there are hundreds of
tons of building supplies a few kilometers away, and food, water, and
air, and a hundred robotic electric carts to move it around for you,
and a nuclear power station, and extra fuel to return to Earth.
Imagine you're an astronaut living on the moon. You live in a cramped
lander. Four body bags sit outside. The lights grow dim and the cold
of space lulls you to sleep.
Ross F.
Ross A. Finlayson
Yes, that would be bad. Safeguards would have to be in place, and the
system would have to be sufficiently engineered that underwriters
would accept that risk.
If the Earth to orbit mass driver enables human presence in space,
including improved abilities to find and move the asteroid that would
do that, its cost avantages alone would make that icing.
I use Google to search NASA web pages for "coilgun".
http://lifesci3.arc.nasa.gov/SpaceSettlement/Nowicki/SPBI112.HTM
The above has not much bad to say about the coilgun. It says the
electrical equipment would cost a billion for a tonne of payload.
http://lifesci3.arc.nasa.gov/SpaceSettlement/spaceresvol2/electromag.html
The above discusses EML more in the context of lunar based systems,
and also offers some history on electromagnetic launch devices, saying
Birkeland in Oslo tested an electromagnetic launch device in 1901.
Northrup at Princeton in 1937 brought forth the idea of energizing
only sections of the launch track, and magnetic levitation of the
payload. He envisioned using an EML to launch people to Luna. In the
40's electromagnetic catapults were used in experiments to help launch
aircraft. Thom and Norwood from NASA Langley in 1961 proposed a
coilgun as a lunar launcher. EML systems continued development in the
70's as part of maglev trains. O'Neill at Princeton in 1974
conceptualized the lunar mass driver, and mass driver study continued
at NASA, and working prototypes were built.
"The energy storage capacitors in the mass driver dominate its mass
and cost. And, because capacitors have a low energy density, they are
especially unsuitable for an electromagnetic launcher of lunar oxygen,
facing the requirements of a larger payload mass at a lower launch
rate."
That's about it, online NASA coilgun information. Each of those
documents references further information.
A search of NASA NTRS for "coilgun" returns this entry:
"Air-Cored Linear Induction Motor for Earth-to-Orbit Systems
Zabar, Zivan (Polytechnic Univ., Six MotorTech Center. Brooklyn, NY
United States); Levi, Enrico (Polytechnic Univ., Six MotorTech Center.
Brooklyn, NY United States); Birenbaum, Leo (Polytechnic Univ., Six
MotorTech Center. Brooklyn, NY United States)
NASA Center for AeroSpace Information (CASI)
1996
The need for lowering the cost of Earth-to-Orbit (ETO) launches has
prompted consideration of electromagnetic launchers. A preliminary
design based on the experience gained in an advanced type of coilgun
and on innovative ideas shows that such a launcher is technically
feasible with almost off-the-shelf components.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08 "
I think that quote from the abstract is great. "A preliminary design
based on the experience gained in an advanced type of coilgun and on
innovative ideas shows that such a launcher is technically feasible
with almost off-the-shelf components."
The price code is A03: $27.50.
Sandia had a project called SERAPHIM in the 80's.
http://www.sandia.gov/seraphim/News/FAQ
"A four meter long "coilgun" using this technology has launched
projectiles at over 1 km/sec, exerting enough force to have
accomplished the earth-to-orbit mission were the gun sufficiently
long."
A coilgun is so good, it probably exists already. So where's the f'in
Earth to orbit mass driver?
http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumber=100986
Some more results from NTRS, "NASA Technical Reports Server":
Direct launch using the electric rail gun
Barber, J. P. (IAP Research, Inc., Dayton, OH, United States)
NASA Center for AeroSpace Information (CASI)
1983
The concept explored involves using a large single stage electric rail
gun to achieve orbital velocities. Exit aerodynamics, launch package
design and size, interior ballistics, system and component sizing and
design concepts are treated. Technology development status and
development requirements are identified and described. The expense of
placing payloads in Earth orbit using conventional chemical rockets is
considerable. Chemical rockets are very inefficient in converting
chemical energy into payload kinetic energy. A rocket motor is
relatively expensive and is usually expended on each launch. In
addition specialized and expensive forms of fuel are required. Gun
launching payloads directly to orbit from the Earth's surface is a
possible alternative. Guns are much more energy efficient than
rockets. The high capital cost of the gun installation can be
recovered by reusing it over and over again. Finally, relatively
inexpensive fuel and large quantities of energy are readily available
to a fixed installation on the Earth's surface.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08
Preliminary feasibility assessment for Earth-to-space electromagnetic
(Railgun) launchers
Rice, E. E. (Battelle Columbus Labs., OH, United States); Miller, L.
A. (Battelle Columbus Labs., OH, United States); Earhart, R. W.
(Battelle Columbus Labs., OH, United States)
NASA Center for AeroSpace Information (CASI)
NASA-CR-167886 , 1982
An Earth to space electromagnetic (railgun) launcher (ESRL) for
launching material into space was studied. Potential ESRL applications
were identified and initially assessed to formulate preliminary system
requirements. The potential applications included nuclear waste
disposal in space, Earth orbital applications, deep space probe
launchers, atmospheric research, and boost of chemical rockets. The
ESRL system concept consisted of two separate railgun launcher tubes
(one at 20 deg from the horizontal for Earth orbital missions, the
other vertical for solar system escape disposal missions) powered by a
common power plant. Each 2040 m launcher tube is surrounded by 10,200
homopolar generator/inductor units to transmit the power to the walls.
Projectile masses are 6500 kg for Earth orbital missions and 2055 kg
for nuclear waste disposal missions. For the Earth orbital missions,
the projectile requires a propulsion system, leaving an estimated
payload mass of 650 kg. For the nuclear waste disposal in space
mission, the high level waste mass was estimated at 250 kg. This
preliminary assessment included technical, environmental, and economic
analyses.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08
http://www.google.com/search?q=%22Earth-to-space%22+gun
http://members.aol.com/oscarcombs/moondust.htm
"It turned out that one reason for the state of pessimism regarding
mass drivers was the unfulfilled promises of a coil gun developed by
Bill Cowan at Sandia Labs. The goal had been an Earth-to-space
launcher, but the velocities predicted by computer models turned out
to be elusive. It was generally agreed that this failure "poisoned the
well" for additional funding of high speed launchers based on similar
(and sometimes dissimilar) technologies."
The Sandia SLINGSHOT software offers some simulation of coilguns. The
University of Texas currently launches small masses (<1kg) at escape
velocity, plus.
I wonder what that means exactly. I looked around for some more
background information of that project, and I'm wondering what is
meant when saying the velocities were elusive.
http://home.adelphia.net/~gsj/railgun.html
Hey, great, I was looking for that. "I have heard rough estimates of
$0.28 per pound to orbit!" That's less than one thirty-thousandth
some current launch methods.
Gun launch, GTLS, electromagnetic launch, EML, Earth-to-space,
Earth-to-orbit, Earth based mass drivers, coilguns, etcetera offer
improvements in cost, efficiency, safety, and reliability in access to
space.
We'll see a lot more applications of EMF, electromotive force, in
future years, and the Earth-to-Orbit mass driver should be one of
them.
Conjecture: the Earth-to-orbit mass driver is a requisite of a moon
base. An ETOMD slices, dices, and is dishwasher safe. It cures what
ails you. An ETOMD may disrupt local radio spectrum communications.
An ETOMD can put stuff into orbit for magnitudes less, saving money
for worthy causes on Earth. Many people leaving Earth for space in
the 21'st century will use an ETOMD. Support an Earth to Orbit Mass
Driver.
Ross F.
Ian Stirling
in this one.
Dust on the moon does not behave like dust on earth.
It is not fluffy, as there is no air in between it.
The pods will be impacting at a minimum of around 2000m/s.
To put this into context, this is slightly faster than the state
of the art tank guns projectiles go at.
When a pod impacts the dust, the dust cannot get out of the way.
Due to the low speed of sound in the dust, and the lack of air,
it simply cannot get out of the way. (I'm estimating that it's a third
the speed of sound in solid rock of the same sort)
The shockwave in the dust does not move faster than the incoming pod,
so you don't get the dust smoothly moving out of the way, but it
piles up in front.
It's also not compressible like gasses are, so it can't get out of the
way like gasses are by being squashed to the sides.
The damage will be essentially the same as impacting a solid surface.
Even neglecting this, the forces will be strongly assymetric, and will
cause the pod to be ripped apart.
<snip>
> Would you please explain how you arrived at your figure? Cursory
> research tells me 10000 K is the heat of a metal-halide lamp element,
> that doesn't oxidize because its bulb is evacuated, nor does it melt.
> It's the air that gets to that temperature.
The heat flow is so much higher than in a bulb, as in the bulb, the
walls are insulated by a boundary layer, and remain relatively cool.
(400C?)
<snip>
> The heat would be the most immediate danger for the pressurized
> liquids and gases, and from state change and the ideal gas law
> rupturing those vessels upon heat shield failure, and shortly
> dissolving the rest of the pod. A possible solid fuel insertion or
> landing booster risks ignition.
The heat almost isn't a problem.
The heat pulse is so brief, that the more important thing is ablation
and stress loads.
<snip>
> Another problem with the whole atmosphere thing, assuming the
> theoretical projectile exiting an evacuated tube at Mach 30, is that
> it then hits the air. The behavior of the pod hitting the ground
> level atmosphere at 8+ miles per second may be as one post put it just
> like hitting a brick wall, yet, that is conjecture. The sudden
> impulse G forces might be much more than those of the launch
> apparatus. That leads into considerations of how to lower the air
> density at the launch tube / free air interface.
This is why sectional density/drag is important, and why small launchers
are impossible.
>
> The launch tube could have air in it, but the coils would be fighting
> it and suffering from the heat. That still might be preferable to
> sudden deceleration. The air pressure in the launch tube could be
> variable.
That's not worthwhile.
About the only issue with sudden onset of atmospheric drag is ringing
and shock loads.
>
> The vacuum/air interface encounter might cause a large explosion
> there, ruining a section of the track, the egress vacuum freeflight
> zone, and some of the coils.
Not really, air rushing in is not that bad, the simplest solution would
be to have the last few hundred meters of the tunnel reinforced,
and a membrane at the end.
A few milliseconds before egress, the membrane is explosively pierced and
pushed back against the walls by the airflow.
Explosively driven barriers then close some few hundred meters back,
to keep most of the tunnel closed.
>
> There might be radical heatshield designs which perhaps cause some
> form of gaseous cavitation, decreasing drag, although drag seems not
> the problem of pressure gradients. The ideal shape may simply be
> pointed at the front end, the penetrator. While that may be the case,
> the "sectional density" consideration has the ideal shape for that
> consideration being a sphere. The pod may have fins, but it should
> look more like a lozenge or a "Star Trek" torpedo.
Not quite.
The sphere is the ideal shape if you'r looking for minimal surface area
to volume.
For aerodynamics, the side areas are almost irrelevant, especially at
hypersonic velocity, so the ideal shape is a cylinder with a nose.
<snip>
> What do you think about the pod being a sphere? How is remotely
> affected air pressure? What happens when 10000 kg at 12 km/s goes
> from near vacuum to 600 millibars, at 300K?
>
> You say a tether would be cheaper. You get a discount on
> "unobtainium"?
A tether is not quite made of unobtanium.
Small quantities of adequate material have been made in the lab.
Converting from nanograms to tens of tons, and making it work in a
large scale structure is hard.
Ian Stirling
> The timeframe of construction of a mass driver is years, not decades.
And the cost will be at the least billions.
Look at the costs of the channel tunnel.
Now explain why a mass driver should be cheaper per unit length.
Especially if you want to construct it in an out of the way place several
kilometers above sea level.
Mike Combs
news:3c6b9c1e.04020...@posting.google.com...
>
> http://members.aol.com/oscarcombs/moondust.htm
>
> "It turned out that one reason for the state of pessimism regarding
> mass drivers was the unfulfilled promises of a coil gun developed by
> Bill Cowan at Sandia Labs. The goal had been an Earth-to-space
> launcher, but the velocities predicted by computer models turned out
> to be elusive. It was generally agreed that this failure "poisoned the
> well" for additional funding of high speed launchers based on similar
> (and sometimes dissimilar) technologies."
>
>
> I wonder what that means exactly. I looked around for some more
> background information of that project, and I'm wondering what is
> meant when saying the velocities were elusive.
Author of the quoted article here.
It could well be that my article is a bit out of date now. If, as you say
earlier, a 4 meter coil gun is launching at >1 km/sec (sounds like about 1/3
lunar escape speed), then it sounds like what some people at the time were
arguing to me was flat-out impossible is now being done.
--
Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."
Gerard O'Neill - "The High Frontier"
Andrew Higgins
> "Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
> news:3c6b9c1e.04020...@posting.google.com...
> >
> > http://members.aol.com/oscarcombs/moondust.htm
> >
> > "It turned out that one reason for the state of pessimism regarding
> > mass drivers was the unfulfilled promises of a coil gun developed by
> > Bill Cowan at Sandia Labs. The goal had been an Earth-to-space
> > launcher, but the velocities predicted by computer models turned out
> > to be elusive. It was generally agreed that this failure "poisoned the
> > well" for additional funding of high speed launchers based on similar
> > (and sometimes dissimilar) technologies."
> >
> snip
> >
> > I wonder what that means exactly. I looked around for some more
> > background information of that project, and I'm wondering what is
> > meant when saying the velocities were elusive.
>
> Author of the quoted article here.
>
> It could well be that my article is a bit out of date now. If, as you say
> earlier, a 4 meter coil gun is launching at >1 km/sec (sounds like about 1/3
> lunar escape speed), then it sounds like what some people at the time were
> arguing to me was flat-out impossible is now being done.
>
What is out of date? SSI built a mass driver in the late 70's that
demonstrated 2000 g's and reached several hundred m/s, as I recall.
Reaching 1 km/s in 4 m is an average acceleration of 12500 g. After
more the 20 years of research, I'd hope for gains more impressive than
that! Especially since we are talking about a baseline design cobbled
together by MIT grad students out of spare parts!
Regarding the Sandia coilgun program, I am not aware of any
developments in the last 10 years to alter the conclusion that
developing a coil gun that can reach 6+ km/s is severely problematic
or board line unfeasible altogether.
One last time: the fact that a coil gun can demonstrate 10,000's of
g's in going from 0 to 1 km/s does *NOT* mean you can string them
together, one after the other, and reach direct space-launch
velocities (6+ km/s). Read up on pulsed-power switching, and you can
begin to appreciate the technical challenges here. Here is a link to
get you started: http://en.wikipedia.org/wiki/Coilgun
--
Andrew J. Higgins Mechanical Engineering Dept.
Assistant Professor McGill University
Shock Wave Physics Group Montreal, Quebec CANADA
http://www.mcgill.ca/mecheng/staff/academic/higgins/
Mike Combs
news:8d344380.0402...@posting.google.com...
>
> What is out of date? SSI built a mass driver in the late 70's that
> demonstrated 2000 g's and reached several hundred m/s, as I recall.
> Reaching 1 km/s in 4 m is an average acceleration of 12500 g.
I take your point. Thinking back now, I think the pessimism I was hearing
was to the effect that you could get up to 1 km/sec alright, but never
beyond it no matter how much longer you extended the mass driver. Les
Snively made me feel a little bit better about this issue, though.
> Regarding the Sandia coilgun program, I am not aware of any
> developments in the last 10 years to alter the conclusion that
> developing a coil gun that can reach 6+ km/s is severely problematic
> or board line unfeasible altogether.
I don't hold out much hope for the Earth to LEO launcher. I have not yet
surrendered the 3.4 km/sec lunar mass driver, though. It seems to me that
operating in a vacuum and at a much smaller scale than what's more commonly
discussed today in term of space launchers ought to be a lot easier.
> One last time: the fact that a coil gun can demonstrate 10,000's of
> g's in going from 0 to 1 km/s does *NOT* mean you can string them
> together, one after the other, and reach direct space-launch
> velocities (6+ km/s).
Understood. Or even the 3.4 km/sec lunar mass driver. It must be confessed
that nothing will prove such accellerations are possible short of actually
achieving them. Which means you have to build the full-up launcher.
(Rats!)
> Read up on pulsed-power switching, and you can
> begin to appreciate the technical challenges here. Here is a link to
> get you started: http://en.wikipedia.org/wiki/Coilgun
Thanks for the link. I was particularly interested in the discussion of
quench guns, since I just read an article saying that they would be much
more economical to use than mass-drivers. Nice, lucid description of the
principle.
Andrew Higgins
"Mike Combs" <mike...@nospam.com_chg_nospam_2_ti> wrote in message
>"Andrew Higgins" <andrew....@mcgill.ca> wrote in message
>news:8d344380.0402...@posting.google.com...
>>
>> What is out of date? SSI built a mass driver in the late 70's that
>> demonstrated 2000 g's and reached several hundred m/s, as I recall.
>> Reaching 1 km/s in 4 m is an average acceleration of 12500 g.
>
>I take your point. Thinking back now, I think the pessimism I was hearing
>was to the effect that you could get up to 1 km/sec alright, but never
>beyond it no matter how much longer you extended the mass driver. Les
>Snively made me feel a little bit better about this issue, though.
>
>> Regarding the Sandia coilgun program, I am not aware of any
>> developments in the last 10 years to alter the conclusion that
>> developing a coil gun that can reach 6+ km/s is severely problematic
>> or board line unfeasible altogether.
>
>I don't hold out much hope for the Earth to LEO launcher. I have not yet
>surrendered the 3.4 km/sec lunar mass driver, though.
>
The original SSI mass driver concept is probably sound. Reaching lunar
escape with a low acceleration system is quite feasible. Note that lunar
escape is only 2.4 km/s, by the way, not 3.4 km/s. If you want a 100 km
apolune orbit in order to throw mass up to your catcher, you only need 1.7
km/s on the surface. This is entirely feasible for mass driver.
Having said that, I think a better way to throw bulk mass off the surface of
the moon is to use Baker & Zubrin's sling-launcher:
Baker, D., Zubrin, R., "Lunar and Mars Mission Architecture
Utilizing Tether-Launched LLOX," AIAA-90-2109, 26th Joint
Propulsion Conference, July 16-18, Orlando, FL.
Note this is a tether based on the lunar *surface* (not in orbit) that uses
a 7-km-long tether whirled like a sling on top of a modest (50 m tall)
tower. You have two weeks of steady solar power to slowly spin the thing
up. Kevlar would suffice for the tether; nothing more fancy required.
The baseline Baker & Zubrin design was for launching 10 tons. Actually, you
are throwing *two* 10 ton masses on end of two tethers, to keep the system
balanced, but the second mass can just be a bag of regolith that is released
simultaneously with the payload at the other end, and impacts the lunar
surface in someone else's backyard.
The total mass of the system (tower, tether, etc.) is about 100 tons, so the
system can launch more than its own mass over the course of a year. This
seems to be a much more feasible system (i.e., much lower initial investment
costs, lower initial mass to bring to lunar surface, etc.) than the mass
driver concept.
Ross A. Finlayson
> What is out of date? SSI built a mass driver in the late 70's that
> demonstrated 2000 g's and reached several hundred m/s, as I recall.
> Reaching 1 km/s in 4 m is an average acceleration of 12500 g. After
> more the 20 years of research, I'd hope for gains more impressive than
> that! Especially since we are talking about a baseline design cobbled
> together by MIT grad students out of spare parts!
>
> Regarding the Sandia coilgun program, I am not aware of any
> developments in the last 10 years to alter the conclusion that
> developing a coil gun that can reach 6+ km/s is severely problematic
> or board line unfeasible altogether.
>
> One last time: the fact that a coil gun can demonstrate 10,000's of
> g's in going from 0 to 1 km/s does *NOT* mean you can string them
> together, one after the other, and reach direct space-launch
> velocities (6+ km/s). Read up on pulsed-power switching, and you can
> begin to appreciate the technical challenges here. Here is a link to
> get you started: http://en.wikipedia.org/wiki/Coilgun
Is the study of hysterisis like chaos theory?
Non-linear analysis has come a long way in the past three decades.
What do you mean by "board line infeasible"?
http://www.google.com/search?q=hysteris+chaos
http://www.google.com/search?q=hysterisis+chaos
http://www.google.com/search?q=pulsed-phase
http://205.243.100.155/frames/pasley.html
That's interesting, it has some pictures of Sandia's Z-Pinch. One of
Sandia's Cowan's is recently moved to Nevada where they have a larger
installation of that kind of device.
http://www.google.com/search?q=Cowan+%22Z-Pinch%22
The proceedings of the IEEE pulsed power conference would have much
information about studies into the pulsed-power questions.
http://ppc97-www.nrl.navy.mil/ppctoc/ppctoc.html
http://www.pulsedpowerinc.com/
http://www.eece.unm.edu/ppst/ppst/
One example might be "Application of Superconductivity to Pulse Power
Problems", Proc. IEEE Pulsed Power 1983.
Besides researching "pulsed-power", it is also "pulse power."
http://www.google.com/search?q=%22pulsed-power+switching%22+coil
http://www.google.com/search?q=%22pulse power+switching%22+coil
Where's Tesla? Tesla's been dead a hundred years.
You don't seem to imply that the switching problem is a theoretical
barrier, but is more of a technical barrier.
What about UT researchers sending payloads of a few grams faster than
escape velocity already, using a coilgun?
How about two switches on the coils, one connects to the coil and
energizes it, the other low resistance/impedance switch connects the
coil to a power sink and de-energizes it, perhaps through to a matched
coil of opposite polarity?
Where pulse power switching is not a theoretical barrier, the
Earth-to-orbit mass driver is still way more cost efficient and the
perhaps best near term option for cheap, and reliable, access to
space.
A technical challenge is great. We're not operating in a vacuum here,
technical advances are for more than space exploration. There are a
lot of technical advances waiting to be used.
Ross F.
Ross A. Finlayson
> developments in the last 10 years to alter the conclusion that
> developing a coil gun that can reach 6+ km/s is severely problematic
> or board line unfeasible altogether.
Hi,
I try to understand the switch timing question of the magnetic coils.
I'm quite ignorant about E&M, electricity and magnetism. If I'm going
to say the coilgun can launch faster than 11 km/s I should have some
basic understanding of its function.
The coil of the coilgun is a wire or other conductor, it looks like a
clothespin spring. electricity is applied to one end of the wire to
form a circuit and the shape and density of the coils of wire form a
magnetic field, it's a coil. When the circuit is broken, the field
immediately diminishes.
I think of current as a flow of electrons, going upstream, Escherian.
The amperage is the pressure. The resistance is the diameter and
length of the pipe. The voltage is the viscosity. Is that not
ridiculous? Please explain it in those terms. I study, the amperage
is the flow rate of coulombs per second, one amp, 6.3 * 10^18 electron
charges/s, voltage is the pressure, resistance the diameter of the
pipe. What's the viscosity? There are terms like inductance,
impedance, capacitance, dielectric ratio, among a wide variety of
words I could not correctly use to explain electrical phenomena.
http://scienceworld.wolfram.com/physics/topics/Electromagnetism.html
Then again, I think the universe is infinite, and dark matter is just
so far away that its photons are drawn more towards other unseen
visible universes, with our visible universe being a huge black hole
in a spherical packing of universes, with each invisible to the other.
I'm not a cosmologist, neither a rocket scientist. The question is
not "where's the mass" but rather "where's the energy."
Anyways I'm trying to understand how a coilgun works. Basically my
conception is that the energized coil's Lorentz force will draw a
metallic item within a cone from an end of the coil. The force
sharply increases to a point within the cone where it lessens until
the pod is within the coil. The idea with the coilgun is to remove
the Lorentz (Lorentz or Lorenz?) force when the pod has entered the
coil so the force would not draw it back into the coil, as inertia and
momentum have been imparted to the pod.
http://scienceworld.wolfram.com/physics/LorenzRelation.html
The issue seems to be that removing the power to the coil doesn't
cause the field to disappear immediately, there is a residual field,
the hysterisis effect. Thus when the pod is leaving the coil, the
magnet is still deenergizing.
"Upon deenergizing the coil, the collapasing magnetic field induces a
reverse voltage (also known as back EMF) which tends to maintain
current flow in the coil." -
http://www.leachintl2.com/english/english1/vol0/properties/USN007.pdf
There my idea is to flush all the amperage into another coil, or other
electrical component, the power sink. I can't say how or why that
would work.
Dang, there sure are a lot of dimensionless units in this electricity.
So anyways the idea is to denergize the coil so that it is not drawing
back the pod on its passage, yet still keep it energized to draw on
the pod from when it reaches the point where the full current field of
the magnet effects nonnominal force on the pod, where the pod is
accelerating from 0 to Mach 30 in two seconds.
The pods can be energized and set there for a minute or so, levelling
out, the key function of the switching equipment is that as the pod is
introduced to the entry of the launch tube, or its brake is released,
then in coordination with the brake release the coils in succession
must deenergize, basically before the pod reaches the coil.
On a separate issue, the magnetic forces uopn the pod and its contents
is also a question. The pods will have upon them several oersteds or
maxwells or something in cgs magnetic fields. Besides acceleration
hardening and a heat shield, the pod cargo may have to be magnetically
shielded.
I would think mks units are to be used instead of cgs, except instead
mgs, SI units.
Anyways, back to the coilgun proper, I don't have much idea how it
works. The rocket: the liquid or solid fuel oxidizes into gas
exothermically and expels itself from the rocket chamber, a simplified
understanding. Perhaps you could explain the benefits and methodology
of pulse detonation. I was looking at the papers on your web page and
using the shockwave in the liquid explosives has similar applications
to that, it would seem.
http://www.popsci.com/popsci/aviation/article/0,12543,473272-1,00.html
Maybe it could run piezos! Excuse me, that's cryptic. Pulse
detonation rocket engines would be good for the pods, not to mention
heavy lift.
http://spaceflightnow.com/news/0002/28pulsedetonate/
There are two aspects of the simple electromagnetic system: the field
and the flux. The flux is the line in the field.
Here's a discussion of EMALS, the aircraft carrier electromagnetic
catapult:
http://www.globalsecurity.org/military/systems/ship/systems/emals.htm
It says it uses the pulsed disks, then there are the pulsed drums in
other systems. There are probably also other methods. The disks are
flywheels, storing power. The disk stores power and releases it over
some time. (True, false?)
In discussing electromagnetic versus steam pressure launch:
"On the other hand, there are drawbacks to the EMALS. One of these is
that high power electromagnetic motors create electromagnetic
interference (EMI) with electronic equipment. As in the case of an
electromagnetic launcher, there would be sensitive aircraft equipment
sitting directly above the launch motor. Along with the aircraft
equipment is the ship's own equipment, which may be affected by the
electromagnetic emissions. Through proper EMC design and a
"magnetically closed" motor design, EMI will be minimized.
Another drawback of an electromagnetic launcher is the high speed
rotating machinery associated with pulsed power applications. The disk
alternator rotors are spinning at 6400 rpm, each storing 121 MJ, for a
total of 484 MJ. In a laboratory, this is not a problem, but put these
rotors on a heaving, jarring platform and it becomes more complicated.
In order to ensure safe operation, the flywheel and bearings are to be
a stiffer design than conventional."
Flywheel components of an Earth based coilgun would not be subject to
much motion except for earthquakes, magnetic fields are very localized
sources of radio frequency interference.
Tesla, Nikolai Tesla, didn't pass away until 1943, sixty years ago
instead of a hundred.
With warm regards,
Ross F.
Andrew Higgins
"Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
news:3c6b9c1e.04020...@posting.google.com...
news:<8d344380.0402...@posting.google.com>...
>
>escape velocity already, using a coilgun?
>
References, please. I am not aware of any coilgun ever exceeding 1 km/s.
Perhaps you are thinking of railguns, which have achieved velocities of 6
km/s.
Mike Combs
>
> The original SSI mass driver concept is probably sound. Reaching lunar
> escape with a low acceleration system is quite feasible. Note that lunar
> escape is only 2.4 km/s, by the way, not 3.4 km/s.
Thanks for the correction.
> If you want a 100 km
> apolune orbit in order to throw mass up to your catcher, you only need 1.7
> km/s on the surface. This is entirely feasible for mass driver.
>
> Having said that, I think a better way to throw bulk mass off the surface
of
> the moon is to use Baker & Zubrin's sling-launcher:
Sounds promising. I've also heard that a lunar elevator, while needing to
be a good deal longer than the Earthly variety, lies inside the bounds of
current material strengths.
Indeed, there's more than one way to skin a cat. Or a moon...
Ross A. Finlayson
> "Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
> news:3c6b9c1e.04020...@posting.google.com...
> > andrew....@mcgill.ca (Andrew Higgins) wrote in message
> news:<8d344380.0402...@posting.google.com>...
> >
> >What about UT researchers sending payloads of a few grams faster than
> >escape velocity already, using a coilgun?
> >
>
> References, please. I am not aware of any coilgun ever exceeding 1 km/s.
>
> Perhaps you are thinking of railguns, which have achieved velocities of 6
> km/s.
Hi,
I saw it on a webpage about the coilguns. It had some other
information that was flawed, yet also information I had not seen that
is not. I'll look for it again. It might have been an augmented
railgun, but I remember pretty surely that it was a coilgun.
The description was something along the lines of accelerating a small
magnet and having it turn to plasma with at least escape velocity,
V_e, or perhaps that was elsewhere.
If you go to the UT Austin web pages and browse their information
there you can see that they are big into designing coilguns and
railguns for the military. Basically that's talk about tank cannon
with electromagnetic launch. They got a big contract a couple years
ago to develop them. They use either the disk or drum, or both, I
forget. They've launched hypervelocity shells (> Mach 5). The UT
system appears to be fielding the brunt of Army's electromagnetic
launcher development, although I think it's a Lockheed deal.
Electromagnetic launchers are pretty cheap to make. Then again, a
cannon is just a metal tube closed at one end.
I don't think it would take too much to determine a method to switch
the coils to scale the launcher to microsecond times and km/s speeds.
I say that having not breadboarded much. I'm not even very good at
soldering. I took apart a broken Compaq PC-140 and put it back
together one time, it still doesn't work. (Advice appreciated.) The
only thing I test with the multimeter is the car battery. Spark plug
wires are high resistance. I put together an Estes igniter switch
kit. That's about it.
What's the problem with pulsed power switching on coilguns? How is it
resolved in the implementation of a sufficiently large coilgun to
accelerate ten metric tons to escape velocity?
What other problems would exist in the construction of an Earth to
Orbit mass driver or several of them? How much would it cost and why?
With warm regards,
Ross F.
--
Ross A. Finlayson
Finlayson Consulting / Apex Internet Software
http://www.tiki-lounge.com/~raf/
"It's always one more."
Andrew Higgins
"Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
news:3c6b9c1e.04020...@posting.google.com...
news:8d344380.0402...@posting.google.com...
>>
>>g's in going from 0 to 1 km/s does *NOT* mean you can string them
>>together, one after the other, and reach direct space-launch
>>velocities (6+ km/s). Read up on pulsed-power switching, and you can
>>begin to appreciate the technical challenges here. Here is a link to
>>get you started: http://en.wikipedia.org/wiki/Coilgun
>
> Is the study of hysterisis like chaos theory?
>
No.
>
> What do you mean by "board line infeasible"?
>
Meaning: beyond what is presently technically possible, but does not
violate known laws of physics.
When people with deep pockets (SDI) worked on this problem in the 80's, here
was the result:
SDI also ran up against manufacturing hurtles
when it commissioned design studies for full-
scale electromagnetic and gas guns. "As I
recall, it took approximately 5 million
kilograms of copper to build the rail gun,
which is something on the order of one percent
of the entire copper capacity in the United
States," says Len Cavney [deputy director for
innovative science and technology, Ballistic
Missile Defense Organization]. "The capacitors
the coil gun needed--there's not enough capacitor
capability in the world to make those. You'd
have to build a whole new manufacturing facility."
Taken from: Kuznik, F., "Battle of the Big Shots," Air&Space, Aug/Sept.
1993, pp. 54-61. This is an excellent article; good popularization overview
of the different direct-launch concepts.
>
>That's interesting, it has some pictures of Sandia's Z-Pinch.
>
The Z-Pinch machine is a pulsed power supply with tremendous capability. It
can, and has, been use to accelerate projectiles:
http://www.sandia.gov/media/NewsRel/NR2001/flyer.htm
(Or, if you have access to an engineering/physics library, and excellent
paper on these experiments just appeared: M. D. Knudson et al.,
"Near-absolute Hugoniot measurements in aluminum to 500 GPa using a
magnetically accelerated flyer plate technique," J. Appl. Phys., 94(7), 01
Oct 2003, pp. 4420-4431.)
Using the Z-machine, projectile velocities of 20 km/s have been now been
realized; this is almost three times the velocity that is required to
achieve earth orbit! The projectile is accelerated without shock,
spallation, or melting. The only catch is that the projectile ("flyer") was
about 0.2 gram in mass.
Scaling this up to a 1000 kg earth-to-LEO payload launcher is left as an
exercise to the reader :-).
>
>How about two switches on the coils, one connects to the coil and
>energizes it, the other low resistance/impedance switch connects the
>coil to a power sink and de-energizes it, perhaps through to a matched
>coil of opposite polarity?
>
High current/high voltage-generated EM fields can not be turned on and off
instantly. This is what "hysterisis" refers to. If you cannot turn of the
field generated by the coil as the projectile passes, you will be
*breaking*, rather than accelerating, the projectile. As the projectile
moves faster and faster, this switching problem becomes more and more
difficult.
>
>Where pulse power switching is not a theoretical barrier, the
>Earth-to-orbit mass driver is still way more cost efficient and the
>perhaps best near term option for cheap, and reliable, access to
>space.
>
No.
Earth-to-orbit mass drivers *may* be a long-term option if putting a lot of
bulk mass in LEO is required (i.e., a massive cis-lunar infrastructure).
This assumes, of course, that carbon nanotube-based space elevators turn out
to be unfeasible, for some as-yet-to-be-identified reason. Of course, if
you can "bootstrap" (i.e., mine the moon or NEA's), it is uncertain why you
would wnat to bring that much mass into LEO in the first place.
>
>A technical challenge is great. We're not operating in a vacuum here,
>technical advances are for more than space exploration. There are a
>lot of technical advances waiting to be used.
>
Alas, a tremendous amount of resources was devoted to these problems in the
1980's by organizations that had very deep pockets at the time. The
anticipated results were not realized, and no significant breakthroughs have
occurred in the decade since then to modify these conclusions.
Andrew Higgins
Higgins" <andrew....@mcgill.ca> wrote in message
news:<aJNUb.16067$2g.1...@charlie.risq.qc.ca>...
>> "Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
>>news:3c6b9c1e.04020...@posting.google.com...
>>> andrew....@mcgill.ca (Andrew Higgins) wrote in message
>> news:<8d344380.0402...@posting.google.com>...
>>>
>>>What about UT researchers sending payloads of a few grams faster than
>>>escape velocity already, using a coilgun?
>>>
>>
>>References, please. I am not aware of any coilgun ever exceeding 1 km/s.
>>
>>Perhaps you are thinking of railguns, which have achieved velocities of 6
>>km/s.
>
>
Yes.
>
>Electromagnetic launchers are pretty cheap to make.
>
No, they are not.
>
> Then again, a
> cannon is just a metal tube closed at one end.
>
No. Cannons are not inexpensive. Ones designed to reach hypervelocity are
anything but inexpensive.
>
>I don't think it would take too much to determine a method to switch
>the coils to scale the launcher to microsecond times and km/s speeds.
>
Some very bright people have spent upwards of $100M on this problem, and
came to a very different conclusion.
Ross A. Finlayson
> "Ross A. Finlayson" <r...@tiki-lounge.com> ...
> >
> > Then again, a
> > cannon is just a metal tube closed at one end.
> >
>
> No. Cannons are not inexpensive. Ones designed to reach hypervelocity are
> anything but inexpensive.
>
> >
> >I don't think it would take too much to determine a method to switch
> >the coils to scale the launcher to microsecond times and km/s speeds.
> >
>
> Some very bright people have spent upwards of $100M on this problem, and
> came to a very different conclusion.
I think we agree that the escape velocity coilgun is not technically
impossible.
Here is a reference to a protoype design, from 1989:
http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumber=22590
"A coilgun was designed to accelerate a 14-kg mass to 6 km/s and, by
adding additional equipment, to accelerate a 10-kg mass to 11 km/s."
They apparently do not consider the concept technically infeasible.
Consider that among the other references advocating Earth-to-orbit
mass drivers, for example the one mentioned that says it is feasible
with almost "off-the-shelf" parts.
The status quo method of launching mass into space is rocketry.
Rocketry works great: it's hideously expensive, the multi-million
dollar rockets are disposable, various ozone-depleting fuels are
injected high into the atmosphere, and they rarely explode with great
force.
Upcoming advances in rocketry such as the pulsed detonation engine may
offer significantly higher efficiency in fuel consumption, decreasing
the 9:1 or worse ratio of fuel to payload in a rocket system to escape
velocity, towards a 13.5:1 fuel/oxidizer ratio.
About the piezo quip, my idea was that reverse-piezoelectric effect
could cause explosive excitative shockwaves in small shaped chambers.
The coilgun would have its flaws: the design on the table can't be
used to lanch people or other "soft" payloads. Another design with
lower acceleration may.
In this discussion we've considered the concept of the cost of such an
item, the numbers range from less than a single shuttle mission to
billions of dollars, less than the cost of five or six shuttle
missions, or building a shuttle. We can each understand that a
constructed ETOMD could launch at costs much, much lower than other
accepted methods.
We've considered some of the environmental effects, with the "sonic
boom" of the hypersonic projectile.
In comparison to concepts such as the space tether, it was discussed
that a theoretical tether system for either the elevator or LEO
catcher may well be impossible with current and expected materials,
and as well that the construction of one would require thousands of
tons of matter put into Earth orbit and for construction to take place
in orbit.
The ETOMD is built on the ground, it's materials are shipped to it on
the ground, it's control systems and access panels are on the ground,
maintenance people can get to it on the ground, tours can be taken of
it on the ground.
The ETOMD is reusable. It uses electricity, quite a large amount of
it, to propel payloads in the ranges of tons with the Earth as a
backstop. Once its fired its payload, which only has to concern
itself with what happens to it once it reaches the edge of Earth's
gravity well, another can be launched within minutes.
Building one would be a technological achievement on the order of a
wonder of the world, for far less than invading a small country.
I think this community, sci.space.policy, etcetera, and its readers
ranging from rocket scientists to third-grade wannabe rocket
scientists, wants to see the opening of space to mankind. We
understand that the Earth, brilliant gem of our solar system and
cradle of life, with everything upon it, is less than 1% of the mass
and energy contained within the Sun's gravity well, and that those
other-than-worldly resources could be cheaper than destroying the
fragile yet resilient ecosystem of Earth.
The Earth to Orbit mass driver, ETOMD, is probably a quite feasible
concept. As you mention, hundreds of millions of dollars have been
put into the research of its fundamental underpinnings, and its study
is rapidly advancing, with limits changing and what was once
considered impossible accepted as normal.
As part of a broader portfolio of space access technologies, the ETOMD
fits an important niche: it could put enough mass from Earth onto the
moon to support a sustained presence there, or on Mars. It puts many
tons out past the draw of Earth's gravity, and those guided payloads
can then direct themselves directly (or, rather, circularly through
the much larger reach of gravity of the Sun) to the Moon, Mars, or
other places in out solar system, to support a human presence anywhere
in our solar system.
It's be pretty cool to see it.
Andrew Higgins
news:3c6b9c1e.04020...@posting.google.com...
news:<BMVUb.18670$2g....@charlie.risq.qc.ca>...
>> "Ross A. Finlayson" <r...@tiki-lounge.com> ...
>>>
>>>the coils to scale the launcher to microsecond times and km/s speeds.
>>>
>>
>>Some very bright people have spent upwards of $100M on this problem, and
>>came to a very different conclusion.
>
>I think we agree that the escape velocity coilgun is not technically
>impossible.
>
>Here is a reference to a protoype design, from 1989:
>
>http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumber=22590
>
>"A coilgun was designed to accelerate a 14-kg mass to 6 km/s and, by
>adding additional equipment, to accelerate a 10-kg mass to 11 km/s."
>
The study you site refers to a theoretical design. When Sandia and others
tested their performance models against *actual* tests of coilguns in the
late 80's and early 90's, they found that the performance did not match
prediction as the velocities approached 1+ km/s. The actual devices
significantly *underperformed* the predictions.
If you want to appreciate this, you have to penetrate the technical
literature. A good place to start is the journal: IEEE Transactions on
Magnetics. Start with Jan. 2003 issue (Vol. 39, Issue. 1):
http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?puNumber=20
...and every January of odd-numbered years before that, all the way back to
1989. You can obtain electronic access to these papers at most engineering
libraries.
Please note that you will *not* find papers entitled: "Why our coilguns
don't work." The technical literature does not work like this (at least,
not for people that want to keep their research funded :-). What you have
to do is read the predictions made based on models ten or fifteen years ago,
then compare with the experimental results demonstrated five years ago, and
then see what problems the *current* investigations are modeling in order to
appreciate the obstacles a given technology has encountered.
Occasionally you do find a researcher honest enough to show their model
predictions, and how their experimental results fall short of their model.
See: Berning, P.R.; Hummer, C.R.; Hollandsworth, C.E., "A coilgun-based
plate launch system," IEEE Transactions on Magnetics, Vol. 35, Issue: 1, Jan
1999, pp. 136-141.
>
>The status quo method of launching mass into space is rocketry.
>Rocketry works great: it's hideously expensive, the multi-million
>dollar rockets are disposable, various ozone-depleting fuels are
>injected high into the atmosphere, and they rarely explode with great
>force.
>
As is discussed regularly on this group, none of these issues are inherent
to the technology of rocketry, but rather historical artifacts that are
residual from the particular path rocket technology has taken to date. None
of these are sufficiently compelling to discard the use of rockets.
>
>Upcoming advances in rocketry such as the pulsed detonation engine may
>offer significantly higher efficiency in fuel consumption, decreasing
>the 9:1 or worse ratio of fuel to payload in a rocket system to escape
>velocity, towards a 13.5:1 fuel/oxidizer ratio.
>
I don't understand where you are getting these numbers.
Pulse detonation engines have yet to demonstrate *any* increase in fuel
efficiency compared to the corresponding rocket or turbojet. They almost
certainly will not be an improvement over conventional rockets for "on-board
propellant systems" (i.e., rockets). Jury on air-breathing PDE's is still
out...
>
>The Earth to Orbit mass driver, ETOMD, is probably a quite feasible
>concept. As you mention, hundreds of millions of dollars have been
>put into the research of its fundamental underpinnings, and its study
>is rapidly advancing, with limits changing and what was once
>considered impossible accepted as normal.
>
No, actually research on coil-based accelerators is pretty much dead at the
moment. See Harry Fair's overview paper in the journal I cited above:
Fair, H.D., "Electric launch science and technology
in the United States," IEEE Transactions on Magnetics,
Vol. 39, Issue. 1, Jan. 2003, pp. 11-17.
There is virtually no coilgun research going on in the U.S. at present (or
the rest of the world, for that matter--see the other papers in this
volume).
Ross A. Finlayson
>
> There is virtually no coilgun research going on in the U.S. at present (or
> the rest of the world, for that matter--see the other papers in this
> volume).
I appreciate that.
We do have the one source from '99 out of Buffalo saying the mass
driver is feasible, with "off the shelf components."
In the early days of rocketry, there were many technical hurdles to be
passed before payloads could safely be taken to space. For example in
the early days of rocketry, it might have been the year 500 A.D., and
Galileo was a millenium later.
We can expect somewhat of a smaller amount of time between the
invention of magnetic launching and using it to launch items to space,
considering it was considered for space launch within years of its
initial development.
I am trying to figure out, as you suggest, how the coilgun or railgun
or augmented railgun or magnetic field effect device works to impart
momentum upon objects, and the required concepts to launch something
to escape velocity.
I may have refound that reference about the escape velocity plus
prototype, except it's stated to be a railgun instead of a coilgun,
and shooting less than a gram of plasma to 39991 m/s.
http://www.totse.com/en/technology/science_technology/railway.html
http://www.google.com/search?q=Texas+plasma+coilgun
I can't vouch for that, except that 40 km/s is somewhat higher than 11
km/s, even back in 1985. Also, that was from a railgun instead of a
coilgun.
I'm interested in your interpretation of Fair's 2003 "Electric launch
science and technology in the United States."
http://ieeexplore.ieee.org/xpl/tocresult.jsp?isNumber=26497&puNumber=20
I must dispute that no research is ongoing because there's a large
body of work in developing electromagnetic launch systems for
ballistic projectiles and aircraft catapults. All those papers from
IEEE Trans. on Magnetics from 2003 and presumably also 2005 about
electromagnetic launch technologies, "electric launch" are discussing
exactly that. I don't have access to that article without driving to
the library, please quote from it relevant statements that support
your assertion "research on coil-based accelerators is pretty much
dead at the moment." Perhaps you are talking about railguns instead
of coilguns. The abstract is as follows, from
http://ieeexplore.ieee.org:80/xpl/abs_free.jsp...:
"For electromagnetic launchers, most of the effort is directed toward
improved computational tools, exploitation of these tools for detailed
understanding of transient electrodynamic phenomena, novel
diagnostics, and experiments to resolve remaining critical issues such
as transition from solid to arc contacts in railguns, improved
computational techniques for pulsed power systems, and application of
these tools to design new high-energy pulsed-power sources. New
methods of testing and determining the critical properties of advanced
materials, such as composites, are being developed to enable these
materials to be evaluated in extreme thermal and electromechanical
environments. Additionally, the U.S. Navy is also in the process of
initiating hypervelocity electromagnetic launch efforts for extremely
long-range artillery systems employing high-G novel projectiles. Other
applications of electric launch technology, such as hypervelocity
powder deposition and electromagnetic gun launch to space, continue to
offer new and interesting opportunities."
Fair states in his abstract that electromagnetic GLTS offers "new and
interesting opportunities."
Now, I guess I'm one of those types of people who has heard of
thirteen types of magnetism, yet, I don't remember what they are.
They go something along the lines of paramagnetism, diamagnetism,
ferromagnetism, antiferromagnetism, (looks), ferrimagnetism,
superparamagnetism, etcetera, then there is this talk of permissivity,
permittivity, and permeability, fields and flux, etcetera, etcetera.
http://www.magnetsales.com/Design/Glossary.htm
Anyways, just going off of the abstracts for part of Jan. 2003 Trans.
on Magnetics, there are some hundred-plus abstracts discussing EML,
electromagnetic launch, with overviews of ongoing researches around
the world, and with much discussion of technical specifics.
Here on sci.space.policy, we're talking about a 10 kilometer track of
a coilgun that accelerates a levitated two to forty tonne pod at
hundreds of G's to reach escape velocity, because it's about the only
thing inexpensive (and perhaps reliable) enough to get enough tonnage
on the moon to support a sustained human presence on the moon.
We can examine past data and use it to get an idea of how fast EML
technologies advance. For example, if in the mid-90's things are done
that in the mid-80's were said to be impossible, technologically and
not theoretically, then we might interpolate that in the near future
the technologies of EML will have further matured and be capable of
supporting the demands of the ETOMD.
Where're the duly diligent NASA statements explaining NASA's stance,
outlook, and developments on coilguns and EML GLTS, electromagnetic
launch gun launch to space?
Electromagnetic launch can decrease the cost of access to space by a
factor of a thousand.
Ross F.
Andrew Higgins
"Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
news:3c6b9c1e.04020...@posting.google.com...
>
> outlook, and developments on coilguns and EML GLTS, electromagnetic
> launch gun launch to space?
>
NASA is certainly aware of direct launch to orbit technologies. Robert
Frisbee at JPL keeps tabs on all of the direct launch concepts (railgun,
coilgun, ram accelerator, etc.), has published a few papers on design
studies for gun-launch to orbit using them, and maintains a database of
Advanced Propulsion Technology concepts:
Other NASA centers have funded these various concepts over the years
(Marshall has been putting some funding into MagLev-assisted launch, Langley
funded some ram accelerator work in the early 90's, etc.).
At this point, it is probably preferable that NASA does *not* issue
"statements explaining NASA's stance, outlook, and developments on coilguns
and EML GLTS, electromagnetic launch gun launch to space."
Any statement on these technologies for gun launch would be premature given
their current embryonic state. Broad "big vision" statements can
arbitrarily cut off funding from promising but underdeveloped concepts and
artificially inflate funding to concepts that happen to have the right "buzz
words" associated with them.
Instead, what is essential is to maintain a low-key but steady stream of
funding to permit the key researchers keep cracking at the difficult
problems.
Alex Terrell
>
> The original SSI mass driver concept is probably sound. Reaching lunar
> escape with a low acceleration system is quite feasible. Note that lunar
> escape is only 2.4 km/s, by the way, not 3.4 km/s. If you want a 100 km
> apolune orbit in order to throw mass up to your catcher, you only need 1.7
> km/s on the surface. This is entirely feasible for mass driver.
There's some interesting discussion here, but I missed:
1. What's the difference between a coil gun and a mass driver
2. For reaching L1 or L2, about 2.4km/s is needed. How long would such
a launcher need to be?
3. How much would it mass (as a multiple of the payload mass).
>
> Having said that, I think a better way to throw bulk mass off the surface of
> the moon is to use Baker & Zubrin's sling-launcher:
>
> Baker, D., Zubrin, R., "Lunar and Mars Mission Architecture
> Utilizing Tether-Launched LLOX," AIAA-90-2109, 26th Joint
> Propulsion Conference, July 16-18, Orlando, FL.
>
> Note this is a tether based on the lunar *surface* (not in orbit) that uses
> a 7-km-long tether whirled like a sling on top of a modest (50 m tall)
> tower. You have two weeks of steady solar power to slowly spin the thing
> up. Kevlar would suffice for the tether; nothing more fancy required.
>
This certainly has the advantage of no capacitors needed. The tip is
at about 80g. Did Baker plan to spin it up with cargo at the end, or
to slowly deploy the cargoS along the tether and release at point?
On the other hand, it would require an exact release time to achieve a
consisitent release direction. The mass driver has the ability to
measure and tune the speed over the last kilometer, so greater
accuracy is possible. That's why a mass driver can deliver a continous
stream of dumb pellets. The sling launcher would launch fewer, larger
loads with some guidance.
> The baseline Baker & Zubrin design was for launching 10 tons. Actually, you
> are throwing *two* 10 ton masses on end of two tethers, to keep the system
> balanced, but the second mass can just be a bag of regolith that is released
> simultaneously with the payload at the other end, and impacts the lunar
> surface in someone else's backyard.
>
That limits the velocity somewhat, and means half the energy is
wasted. Perhaps better to build on a mountain top and a lateral load
80 times the cargo's (Earth) weight.
> The total mass of the system (tower, tether, etc.) is about 100 tons, so the
> system can launch more than its own mass over the course of a year. This
> seems to be a much more feasible system (i.e., much lower initial investment
> costs, lower initial mass to bring to lunar surface, etc.) than the mass
> driver concept.
Sounds to good to be true. Any pointers to more web based info?
Alex
Ross A. Finlayson
> Any statement on these technologies for gun launch would be premature given
> their current embryonic state. Broad "big vision" statements can
> arbitrarily cut off funding from promising but underdeveloped concepts and
> artificially inflate funding to concepts that happen to have the right "buzz
> words" associated with them.
>
> Instead, what is essential is to maintain a low-key but steady stream of
> funding to permit the key researchers keep cracking at the difficult
> problems.
I agree that was an unfair swipe at NASA. It was fair at part of
NASA.
There are lots of politics in research, especially in big science.
That's because there's money in science. As we see from "IEEE
Transactions on Magnetics", there is a lot of worldwide research into
the theory and applications of electromagnetic launch.
I want to identify why the coilgun is preferable to the railgun for
launching cargo to space. The railgun requires a specific projectile
composition and highly energizes the payload. The coilgun imbues a
magnetic field to the payload but it is much weaker. The railgun
requires physical connection between the rails and the payload,
quickly deteriorating the rails, although a plasma arc may be less so.
The coilgun may be contactless between launcher and launchee. The
coilgun is somewhat more efficient and doesn't require a capacitor the
size of a football stadium, where the coilgun requires more
sophisticated power switching equipment, each coil is energized and
deenergized separately.
I still have perhaps the naive misconception that the reverse EMF of
the coil deenergization can be shunted away to decrease hysterisis
effects.
EGLTS, electromagnetic gun launch to space, "eaglets", is a promising
option in terms of cheap, reliable, and scalable access to space. It
is not unrealistic to say that if EGLTS was funded as a high priority
of NASA that it would be launching things into space within a decade.
It's simply not, throwing money at a problem isn't always a feasible
solution, but sometimes it is.
This isn't talk about finding a way around the force of gravity, it's
about extending well-known physical principles to build a large
launcher of cargo safely into space.
One of the major drivers behind its consideration is cost. Realistic
models of an ETOMD offer costs that are a small fraction of current
methods. The current cost of access to space is prohibitive.
Another key aspect of the ETOMD is the scalability. The ETOMD can
launch over and over again, it''s anything but disposable. The pods
may well be disposable ("expendable"), but by the same token they
offer a much larger ratio of payload to fuel/reaction mass, the pod is
launched all the way to outer space, and the next can follow in
minutes instead of months or years.
The issue of reliability is another. With permanent magnets, the pod
never contacts the launch tube. It may be easier to manufacture and
test hundreds or thousands of solid core, single piece construction,
uniform, magnetic coils than solid or liquid fuel rockets, which are
tested by ignition. The smaller requirements of the pods' rocket
motors, in terms of them operating as the kick stage or outside of
Earth's gravity, allow them to be both more uniform and also more
reliable for being smaller explosion chambers.
It's probably out in the desert somewhere.
Let's say there absolutely, positively, has to be eight thousand
metric tonnes of Earthly materials on the moon in ten years. How
could that happen?
EGLTS doesn't have to be "big vision." Its costs could be a small
fraction of the national space budget and be successful. As part of a
bigger picture of utilizing space resources, it's almost a given.
I think on this thread we've established that many questions remain in
EGLTS.
Ross F.
Mike Combs
news:d81e59c9.04020...@posting.google.com...
>
> There's some interesting discussion here, but I missed:
> 1. What's the difference between a coil gun and a mass driver
I think they're pretty much the same thing. Most people, when using the
term "mass driver" are meaning the specific design Gerard O'Neill came up
with.
> 2. For reaching L1 or L2, about 2.4km/s is needed. How long would such
> a launcher need to be?
According to http://www.ssi.org/assets/images/mass_driver_chart.jpg at
http://www.ssi.org/slideshow.html, only 160 meters.
> 3. How much would it mass (as a multiple of the payload mass).
This I'm not sure about. I remember O'Neill commenting that the components
for the driver portion of the system would fit into a single Space Shuttle
cargo bay, but I think the power supply (solar panels) was several times the
mass of the driver itself.
Henry Spencer
Alex Terrell <alext...@yahoo.com> wrote:
>1. What's the difference between a coil gun and a mass driver
Properly, a mass driver is an electromagnetic catapult of some type --
perhaps a coilgun -- with recirculating payload carriers ("buckets") which
are decelerated and reused, so that the payloads don't have to incorporate
any special structures (e.g. coils) to interact with the gun.
(Gerard O'Neill, who invented the concept, also coined the term. It is
*not* a generic synonym for "electromagnetic catapult".)
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. | he...@spsystems.net
Ross A. Finlayson
I'm hoping someone can help me understand some of the design issues of
a coilgun.
The coilgun is at it's simplest an energized coil, where when it's
energized it means it has an electrical current running through it.
You slide an item along a track through the coil, and the coil's
magnetic field draws the projectile into the coil. The coil's current
is then switched off, and the projectile moves on through the coil
with the velocity imparted to it by the coil.
If you line up a bunch of coils, and make a long track through them,
then each energized coil draws the projectile, each adding velocity to
the projectile.
My questions are about that and scaling up the coilgun to launch ten
tons into the air at Earth escape velocity, 11 km/s.
People are telling me the hysterisis effects on the coils don't allow
the field to drain away quick enough. The projectile is flying
through so quickly that by the time it is to be in the draw of the
field the field is to be shut off, in the context of swirl and eddy
and perhaps of the skin effect: the highest flow in a pipe of liquid
is at the center, the highest flow of current in a wire is at the
edges.
The railgun, a different method of electromagnetic launch, has
launched items to more than 40 km/s, but the "barrels" (rails) quicky
degrade to be worthless, the required power is hooge.
I'm interested in learning about the coilgun because it can be
designed to be contactless between coils and projectile, and is
otherwise low maintenance and high lifetime.
People toss around numbers like 80 gigajoules per launch to space.
I don't have very much electrical background. I'm hoping that you can
help explain to me how a coilgun works and issues in having an eight
or ten mile long coilgun to accelerate 10000 kilograms at hundreds of
G's to Mach 30, about 11 km/s, escape velocity.
If you would, please outline the very basics of the operations of such
a thing. Explain what a magnetic field is, what types of fields there
are, and how an electrical current ran through a coil of conducting
wire forms a magnetic field. What aspects of the coil windings,
armature, and power supply affect the magnetic field?
I do some research and have about a 3% better understanding of the
hysterisis or hysteresis effect. Now what I want to do to the coil is
when the projectile is a third of the way through the coil, apply
twice the power in the opposite direction of the current. This is
with having DC, direct current, through the coil. So there are two
current sources. The pod is inserted at constant velocity, and then
the half current charges the first coil for it to enter. As it
enters, the half current goes to the second coil and the full current
to the first coil. Here I want the action of the pod upon the
magnetic field of the coil to flip the electromechanical switch at the
speed of light.
Why one third of the length of the coil? I think the point mass
moving through the coil reaches a plateau a third of the way through.
Yet, while that might be the case in my near-junk science
understanding, what if it was 1/e or 1/pi?
The pod hits the plateau, affecting the field and thus current and its
applying electronics to switch it.
The "air" core, in this case vacuum, of the coil prevents
"saturation".
I get this for searching for information about the words "coilgun
winding coil winder magnet wire" and learning some of the use of words
like "remance/remanance, reluctance, and resonance" but not yet
"roentgens".
I guess it'd be a holistic study, hopefully holonomic.
Ross F.
Alex Terrell
> In article <d81e59c9.04020...@posting.google.com>,
> Alex Terrell <alext...@yahoo.com> wrote:
> >1. What's the difference between a coil gun and a mass driver
>
> Properly, a mass driver is an electromagnetic catapult of some type --
> perhaps a coilgun -- with recirculating payload carriers ("buckets") which
> are decelerated and reused, so that the payloads don't have to incorporate
> any special structures (e.g. coils) to interact with the gun.
>
> (Gerard O'Neill, who invented the concept, also coined the term. It is
> *not* a generic synonym for "electromagnetic catapult".)
Thanks.
Do you or Mike know what the latest thinking is on where such a
catapult would need to be stationed? where would it fire to? (L1?) and
whether a stream of small particles or larger guided cargos are
preferred?
Any recent papers?
Mike Combs
>
> Do you or Mike know what the latest thinking is on where such a
> catapult would need to be stationed?
Somewhere on the near side.
> where would it fire to? (L1?)
Seems like in the studies, L2 was preferred. Maybe only because an
installation on the near side was considered preferable to one on the far
side.
>and
> whether a stream of small particles or larger guided cargos are
> preferred?
It seems to me that a "mass pipeline" of small particles (about the size of
a softball is what the studies assumed) streaming into a mass-catcher at L2
is preferable to larger guided cargos for the simple reason that in the
latter case, we'd have to be talking a much, much bigger diameter mass
driver (perhaps a longer length too), and hence greater start-up costs.
Mike Combs
> the field to drain away quick enough.
I got an E-mail from Les Snively who worked on mass-drivers with O'Neill.
He mentioned that one solution they had to this effect was to transition at
the later, higher speed portions of the mass driver to greater numbers of
single-turn coils. I talk about this a bit in an article here:
http://members.aol.com/oscarcombs/moondust.htm
But I should comment that Snively and O'Neill were working the much easier
problem of achieving lunar escape (2.4 km/s) in a vacuum.
SpaceSavant
> You dont' have to use a rail or coil gun at all a "simple" light gas
> gun scaled up could do the job; there are many web references on
> this.
>
> The problem seems to be the fixed orbit inclanation of such
> a system, be it coil or gas based. Also I believe that both types of
> systems need an orbital kick stage to insert them into a circular
> orbit. The costs of building a gun that achieves near orbital
> velocites at the muzzle just isnt effective economically.
>
> Although there are at least one company actively researching the use
> of gun launching to orbit:
>
>
> http://www.columbiad.ca/industrial/
>
You may want to also try and find some papers written by someone
called G.V Bull. I have collected some portion of spanish versions,
mainly related to proposals for small satillites up to 1000kg to be
fired using gas guns. The only paper portion I have appears to be
proposing using aerodynamic heating to provide basically a hot gas
thrustering capability for maneuvering into low orbits.
However, the more complete versions appear to be magically
unavailable. Note: The man was assisinated by the US and Isreal when
his research took a turn in what they considered a uncomfortable
direction.
Alex Terrell
> Somewhere on the near side.
>
> > where would it fire to? (L1?)
>
> Seems like in the studies, L2 was preferred. Maybe only because an
> installation on the near side was considered preferable to one on the far
> side.
I've been thinking about this, and have a question on orbital
mechanics, so I hope Henry reads this as well.
If you want to fire to L2, then L2 would be the pellet's/cargo's
orbital apogee (or is it apolune?). If the launcher fires flat, then
the launcher will be at the cargo's perigee (or is it perilune?) For a
first approximation (2 body problem) these two points are opposite
each other, which means that the launcher must be at the moon's
equator, directly under L1!
That rather limits the possible sites. We would also want the launcher
to be to the lee of some mountains, so if the cargo misses the
catcher, it doesn't come round again and hit the launcher.
Two a second order, we need to consider the coriolis forces of the
moons rotation around the Earth. But this still means that the
launcher needs to be at a fixed location on the equator.
Also, if cargo passes through the L2 point with a velocity of about
70m/s, and it misses the catcher, then it would probably go into Earth
orbit and constitute a hazard. Can you reach L2 with sub orbital
velocity?
Solutions:
1. The launcher can be inclined. This enables control of the perigee.
The extreme version of this, for a short 160m launcher, would be to
put it under L1 and fire almost vertically. (I say almost, it would
need to adapt for coriolis forces.)
2. To fire at sub-lunar escape velocity, suspend the catcher below L1
or L2, say 100 km. Any cargos that miss would fall back to the moon.
Combined with (1), they could be fired to have the apex (apolune?)
100km below L1, hitting the catcher at a velocity of close to zero.
They could then be hauled up to L1 from where they could be dispatched
to L4 and L5.
Would this work?
Alex Terrell
> "Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
> >
> > People are telling me the hysterisis effects on the coils don't allow
> > the field to drain away quick enough.
>
> I got an E-mail from Les Snively who worked on mass-drivers with O'Neill.
> He mentioned that one solution they had to this effect was to transition at
> the later, higher speed portions of the mass driver to greater numbers of
> single-turn coils. I talk about this a bit in an article here:
>
> http://members.aol.com/oscarcombs/moondust.htm
>
> But I should comment that Snively and O'Neill were working the much easier
> problem of achieving lunar escape (2.4 km/s) in a vacuum.
>
real mass driver, perhaps 160m long, that can accelrate particles at
2.4km/s (in air). For NASA's budget it would be a rounding error.
Ross A. Finlayson
>
> It seems to me that a "mass pipeline" of small particles (about the size of
> a softball is what the studies assumed) streaming into a mass-catcher at L2
> is preferable to larger guided cargos for the simple reason that in the
> latter case, we'd have to be talking a much, much bigger diameter mass
> driver (perhaps a longer length too), and hence greater start-up costs.
>
If there's a "mass catcher", and it "catches" mass, then it would have
the mass' momentum imparted to it, and would be knocked out of its
orbit. The only way for it to preserve its orbit would be to direct
some of its mass in the same direction as it received it.
That's like the mass catcher being a little gnome in a spacesuit in
orbit with a large mitt. If he catches ten kilograms shooting off of
the moon and tosses it into a near circular (low) lunar orbit, he
would be pushed out of the way.
If the gnome could hang his suit's coatloop on a "skyhook", he would
be in great shape, but there is no such thing.
We don't have the luxury of gravity sinks, skyhooks, nor the use of
sailing into a high-powered laser beam from Luna, tacking into the
solar breeze. Newton tells us that for each action there is an equal
and opposite reaction.
The "mass catcher" in the ETOMD concept is the moon itself, as well,
the pods have their own control systems to expel part of their own
mass as reaction mass, to circularize their orbits for getting the pod
into a stable Earth orbit, or to accelerate the pod, free of Earth's
gravity well, towards Mars, the moon, or other points.
The lunar O'neillian mass driver launches around 10kg of regolith
aggregate at a fixed azimuth into lunar orbit. It is to be a low
lunar orbit or the nearby planet Earth's gravity well would strongly
interact with it. Then, without some control system on the payload,
the aggregate falls back to the moon.
If a space station in LLO, low lunar orbit, was hit a few times with
tens of kilograms of aggregate at hundreds or thousands of meters per
second, it would be moved.
What are the design considerations of keeping the "mass catcher" on
station? If it's out at the L2 points, hovering around an equilibrium
between Earth and moon's tidal fringes, far removed from the lines
conecting their centers, it would have to cast away as much as it kept
to stay there, as if it did not catch it.
How about the solar wind constantly pushing on sails which charges
universal inertia stores, molecular level vibrating inertial stores?
Such nanomachines are somewhat unfeasible currently, but perhaps
macroscale prototypes could be considered.
Building a huge edifice on the moon is more than unloading a dumptruck
full of the components there.
Warm regards,
Ross F.
Mike Combs
news:d81e59c9.04021...@posting.google.com...
> If you want to fire to L2, then L2 would be the pellet's/cargo's
> orbital apogee (or is it apolune?). If the launcher fires flat, then
> the launcher will be at the cargo's perigee (or is it perilune?) For a
> first approximation (2 body problem) these two points are opposite
> each other, which means that the launcher must be at the moon's
> equator, directly under L1!
>
> That rather limits the possible sites.
Here's an illustration of a recommended site for the lunar mass driver -
http://ssi.org/assets/images/Ch08p162.gif, from
http://ssi.org/Don_Davis_Artshow.html
Looks to be somewhere between 0 and 2 degrees north.
The mass-stream path coming up from the moon -
http://ssi.org/assets/images/Ch08p150.gif
Mike Combs
> If there's a "mass catcher", and it "catches" mass, then it would have
> the mass' momentum imparted to it, and would be knocked out of its
> orbit. The only way for it to preserve its orbit would be to direct
> some of its mass in the same direction as it received it.
The plan was to "throw" to the L-2 point. The L-2 point is unstable on one
axis, but stable on two, and one of those two is the axis in question here.
The force of the impacting pellets will make the catcher displace slightly
from the L-2 point, but it will maintain position. When the pellet stream
ceases, the catcher will shift back to the L-point. Think of a bead on a
string.
> That's like the mass catcher being a little gnome in a spacesuit in
> orbit with a large mitt. If he catches ten kilograms shooting off of
> the moon and tosses it into a near circular (low) lunar orbit, he
> would be pushed out of the way.
The error is in thinking that the payloads are being sent into a circular
low lunar orbit. They're being sent to the L-2 point.
> The lunar O'neillian mass driver launches around 10kg of regolith
> aggregate at a fixed azimuth into lunar orbit.
Nope, L-2. Go back and have another look.
> What are the design considerations of keeping the "mass catcher" on
> station? If it's out at the L2 points, hovering around an equilibrium
> between Earth and moon's tidal fringes, far removed from the lines
> conecting their centers, it would have to cast away as much as it kept
> to stay there, as if it did not catch it.
There is a need for some station-keeping thrusts due to influences from the
sun, etc. There's a rotary pellet launcher on the catcher provided for this
purpose (as well as for providing propulsion when it's time to slip off of
the L-point and head for the refinery in HEO). But note that the pellet
launcher is NOT needed to balance the force of the impacts from the moon.
The scenario design capitalizes on the specific properties of the L-2 point.
Ross A. Finlayson
>
> > The lunar O'neillian mass driver launches around 10kg of regolith
> > aggregate at a fixed azimuth into lunar orbit.
>
> Nope, L-2. Go back and have another look.
>
I think we are confused about the LaGrange points. For the
Earth-Moon-Gnome 3 body system, there are the five Earth-Moon LaGrange
points L1, L2, L3, L4, and L5. L1 is directly between Earth and Moon,
or rather slightly ahead of Moon's path, much nearer the moon than
Earth, where it is held back by Moon's gravity in its orbit around the
Earth to match the moon's angular velocity. The L2 point is past the
moon and slightly behind the moon and as well objects at that point
(with nominal mass compared to Earth or Moon) orbit the Earth with the
same angular velocity as the moon. The L3 point is on the other side
of Earth than the moon in the same orbital path, and is not very much
affected by the moon's pull of gravity. The L4 and L5 point are as
well on the moon's orbital path, almost, yet they are also affected by
the moon's gravity in that the L4 and L5 points are those where they
are the "libration" or semi-accumulator points. So, the gnome would
hang out at the Earth-Moon L4 or L5 point.
The gnome's position is more stable at the L4 or L5 point, except the
solar system is more than a 3-body system, there are hundreds of items
with significant mass around our sun, Sol, but still stopping mass
moving through there would affect his momentum. Consider that enough
force to put him there would be plenty to take him out.
Kepler observed orbits are elliptical, not circular, we don't have any
two body systems, surrounded by an infinitely distant spherical
boundary of infinite mass. The LaGrange points are a simplification.
Our intrepid gnome is Earth bound until there is safe, cheap, and
reliable access to space, from Earth. As a casual and naive observer,
my opinion is that EGLTS, Electric Gun Launch to Space, is where it's
at.
If over sixty years Americans can build hundred of thousands of miles
of interstate road system, then they can build a two hundred mile
mag-lev tunnel to the stars that offers comfortable 2-G acceleration
to space for a ticket of hundreds of dollars, one way.
In the meantime until one is constructed and launched regularly, a
shorter prototype can launch ten ton payloads at dollars on the pound
directly out of Earth's gravity well, and such a system is a
cornerstone of any rational, forward-thinking space exploitation
policy.
The study of n-body systems is a wide and varied one, with many
excellent methods.
Warm regards,
Ross F.
Alex Terrell
> "Alex Terrell" <alext...@yahoo.com> wrote in message
> news:d81e59c9.04021...@posting.google.com...
>
> > If you want to fire to L2, then L2 would be the pellet's/cargo's
> > orbital apogee (or is it apolune?). If the launcher fires flat, then
> > the launcher will be at the cargo's perigee (or is it perilune?) For a
> > first approximation (2 body problem) these two points are opposite
> > each other, which means that the launcher must be at the moon's
> > equator, directly under L1!
> >
> > That rather limits the possible sites.
>
> Here's an illustration of a recommended site for the lunar mass driver -
> http://ssi.org/assets/images/Ch08p162.gif, from
> http://ssi.org/Don_Davis_Artshow.html
> Looks to be somewhere between 0 and 2 degrees north.
>
> The mass-stream path coming up from the moon -
> http://ssi.org/assets/images/Ch08p150.gif
>
1. To be in the correct plane, the launcher is near the equator
2. If the pellet were to miss the catcher, it would leave lunar orbit
and go into an Earth orbit, which isn't ideal.
I think these orbits were calculated before they got the length down
to 160m, and they needed a horizontal launch. I think it's worth
exploring a vertical launch to just below L1.
Ross A. Finlayson
twelvth.
There is not a 1 km/s barrier, even SERAPHIM achieved greater than 1
km/s.
One benefit of the coilgun is that it's variable. There are some
issues with efficiency and saturation, but the same coil, designed for
variability, could launch a pod the size of a schoolbus, telephone
pole, or claw-footed tub, variously ten feet or the limits of the
power supply.
Hey check out this guy, he builds coilguns for fun:
http://www.powerlabs.org/coilgun.htm
This kind of study for large devices falls under the High Voltage (HV)
category of electrical devices.
Mentioned are the single coils, one thing that leads me to consider is
the coil where the wire is essentially a large block of rolled iron,
bent into a cylinder, the solid state coil.
Hey about the mass driver, if the payload doesn't have control systems
then it is difficult to catch it and stay in one place without
ejecting reaction mass. Maybe one way that could work is to have
millions of tons of tether-class unobtainium and make a ring around
the moon, it could electrically dewobble after it absorbed the impact
of catching something, with the gnome having a lifeline to the tether.
The current satellites at the Sun-Earth L1 and L2 points require
adjustments very often, even if only to deal with solar wind. (The
Ringworld is unstable.)
If the Lunar mass driver shotguns ten kilograms of processed regolith
to the Earth-Moon L2, on the far side of the moon, then if it falls
short it would fall back to the moon, if overshot it would enter solar
orbit.
The Earth to Orbit, or rather, I guess Earth to Space, Mass Driver,
ETSMD, would have as its task putting the payload at the extremis of
Earth's gravity well at near zero velocity, where the pod with its
liquid rocket motors could easily nudge it into a high, slow, Earth
orbit. Oftentimes the moon would be there in the way, the moon is
within the edge of Earth's gravity well, then the pod could adjust to
a circularized lunar orbit, or use the moon's gravity as a
"slingshot", with the pod safely away from the Earth.
I search for the term "Earth-to-Space" and am presented with "Space
Elevator" concepts, and that "carbon nanotubes" will offer the
necessary material. The Coriolis would snap the cable, or crack it
like a 200 km whip onto Earth, were such a thing as hundreds of
thousands of tons of a spool of carbon nanotube launched to GEO and
counterweighted down to Earth.
The Space Elevator from Earth is somewhat of a ridiculous concept.
The quoted prices for access are as well orders of magnitude more than
from the mass driver. A failure would be catastrophic and
irrecoverable. Maybe I'm just smug about the assumed superiority of
the mass driver to other launch methods within contemporarily accepted
theoretical limits. Can anyone provide some real numbers on the
tensile strength, mass, and other properties of a "Space Elevator"
cable?
"What is the timetable?
The timetable is 50 years after everyone stops laughing. " -
http://c2.com/cgi/wiki?SpaceElevator
"The NIAC proposed "initial cable" design is roughly 100 000 km long,
1 um (1e-9 m) thick, and tapering from 0.115 m wide in the middle to
0.05 m wide at the ends. That gives it a volume of less than 11.5 m^3.
It should fit on a spool with an inside diameter of 1.1 m, outside
diameter of 2.2 m, and a width of 1.1 m. The "initial cable" has a
mass of 19 800 kg, slightly less than a Russian geosynchronous
communication satellite."
So the idea with the space elevator is to get a process going to make
a continuous cable three or more times the Earth's circumference in
length, wind it perfectly so it unrolls from a large spool of some
kind, in space, to have a needle rocket threaded with the end of it
shoot from space to a pincushion at the equatorial anchor without
snagging the line, and then running more of those 100 000 km threads
up that cable somehow forming a cohesive braided structure, or the
needle misses and the whole thing flies off into space, or the spool
fouls and is snapped out of GEO and lands forthwith back on Earth.
Then rockets are supposed to clip onto it and scale.
Compare that to the concept of the mass driver: plant coils in line
on foundation, insert electricity and payload: the payload is in
space in under a minute. There's somewhat less mumbo-jumbo, or rather
distracting complexity: design issues. As well, the estimated cost
is orders of magnitude less than orders of magnitude less.
Electromagnetic propulsion is used on rollercoasters today, I guess
similarly tethers are used on some amusement rides. Anyways, that's
enough lighthearted mockery of space elevators. I should figure out
some better information on justifying the drive towards the
Earth-to-Space Mass Driver, the ETSMD, the big brother of the ETOMD.
I try to read Baylis' "Electrodynamics: A Modern Geometric Approach."
He is telling me the paravector quaternion representation is better
because it avoids the tensorial indices and the covariant equations
are simpler. He explains some of the difference between
electromagnetic cgs (Gaussian), mks (Heaviside-Lorentz), and SI
(systeme internationale) units, or MKSA, and how there is a ready
transliteration among the units, except where some of the units in one
of the systems are dimensionless in the others. I am disturbed that
kilogram is used instead of gram. He discusses how 3^., 3 with a dot
over it, is the speed of light in meters per second divided by 10^8,
and is around 2.99724958. "The constant 4pi epsilon_0 relates the
fields to the charges that generate them." I have gotten about that
far in that book, page three. "In any case, caution is still needed
when dealing with the macroscopic fields D and H, which have the same
dimensions as the microscopic fields E and B in Gaussian units, but
which are expressed in terms of the sources instead of the forces in
SI units." He mentions the "photonic boom" of Cerenkov radiation, the
shockwave of the medium, tachyons are imaginary. I turn to the index
looking for "coil", there is no entry, I guess then I should look to
Faraday and his fields. Here, "electromagnetic field, of accelerating
charge", page 253: he notes the equation of the field of the
accelerating charge. Baylis' treatment is relativistic, where one of
the stated advantages of the geometric approach is the built-in use of
Minkowskian (non-Euclidean, complex) derivates. He talks about the
Lienard-Wiechert field, of a uniformly accelerating charge. He
presents what is known as the Larmor power formula and explains that
in a covariant form that it is a Lorentz scalar, in the context of the
metric tensor.
Anyways I'm sure it's quite fascinating I might be able to understand
some aspects of its paravectorization vis-a-vis Schaum's Tensor
Calculus handbook.
In section 10.4.1, Thomson scattering, it is noted "The agent that
accelerates a charge is usually the electromagnetic field, and for
non-relativistic motion, the acceleration is a= e/m E."
Unfortunately the book is not a technical design and construction
manual for an Earth-to-Space Mass Driver using commercial
off-the-shelf components: CATS through COTS.
In terms of CATS, what is required is not just cheap access to space,
but rather, safe, cheap, reliable access to space: SCRATS.
Support the Earth to Orbit Mass Driver, the Earth to Space Mass
Driver, and the Earth to Space Mass Transit Systems.
Ross F.
Joe Strout
r...@tiki-lounge.com (Ross A. Finlayson) wrote:
> The Earth to Orbit, or rather, I guess Earth to Space, Mass Driver,
> ETSMD, would have as its task putting the payload at the extremis of
> Earth's gravity well at near zero velocity, where the pod with its
> liquid rocket motors could easily nudge it into a high, slow, Earth
> orbit.
Um, no. Trying to shoot a projectile all the way to GEO (which of
course is the slightly more sensible version of your plan above) is
much, much harder than just shooting it into LEO -- which is already too
hard for a practical earth-to-orbit mass driver.
> I search for the term "Earth-to-Space" and am presented with "Space
> Elevator" concepts, and that "carbon nanotubes" will offer the
> necessary material. The Coriolis would snap the cable, or crack it
> like a 200 km whip onto Earth, were such a thing as hundreds of
> thousands of tons of a spool of carbon nanotube launched to GEO and
> counterweighted down to Earth.
Oh would it now? There are a number of physicists and engineers who
will be greatly interested in your results, since their calculations
produce very different ones. You must have some new math that will
revolutionize orbital mechanics. Where are you submitting your paper,
and when do you expect it to appear?
> The Space Elevator from Earth is somewhat of a ridiculous concept.
With your "new math" yes. In the real world, no -- assuming we can get
those nanotube fibers (which is a matter of chemistry).
> The quoted prices for access are as well orders of magnitude more than
> from the mass driver.
Orders of magnitude more than floating into orbit on fairy dust, too.
So what?
> A failure would be catastrophic and irrecoverable.
All right, I've run out of patience even for mocking you. You clearly
haven't read even the briefest summaries of studies on space tethers,
yet you see no problem with going around claiming things about them that
you are patently unqualified to know. Please just go away and come back
when you've either gotten an education, or at least a genuine interest
in learning things.
,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| j...@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'
Andrew Higgins
>
> There is not a 1 km/s barrier, even SERAPHIM achieved greater than 1
> km/s.
>
There is no 1 km/s barrier, as in, "At 1 km/s, coilguns mysteriously stop
working."
However, no coil has ever demonstarted velocities much greater than 1 km/s.
Certainly not 2 km/s.
By "SERAPHIM", I assume you are refering to Sandia's coilgun in the 1980's.
It did not exceed velocities much above 1 km/s either.
>
> I search for the term "Earth-to-Space" and am presented with "Space
> Elevator" concepts, and that "carbon nanotubes" will offer the
> necessary material. The Coriolis would snap the cable, or crack it
> like a 200 km whip onto Earth, were such a thing as hundreds of
> thousands of tons of a spool of carbon nanotube launched to GEO and
> counterweighted down to Earth.
>
> The Space Elevator from Earth is somewhat of a ridiculous concept.
>
Do yourself a favor and read this book:
http://www.amazon.com/exec/obidos/tg/detail/-/0974651710
or this report:
http://www.isr.us/Downloads/niac_pdf/contents.html
...and you will likely come to a different conclusion.
Andrew Higgins
"Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
news:3c6b9c1e.04021...@posting.google.com...
>
>
References, please.
--
Andrew J. Higgins
andrew....@mcgill.ca
Dr John Stockton
in news:sci.space.policy, Ross A. Finlayson <r...@tiki-lounge.com> posted
at Fri, 13 Feb 2004 20:12:26 :-
>I think we are confused about the LaGrange points. For the
>Earth-Moon-Gnome 3 body system, there are the five Earth-Moon LaGrange
>points L1, L2, L3, L4, and L5. L1 is directly between Earth and Moon,
>or rather slightly ahead of Moon's path, much nearer the moon than
>Earth, where it is held back by Moon's gravity in its orbit around the
>Earth to match the moon's angular velocity. The L2 point is past the
>moon and slightly behind the moon and as well objects at that point
>(with nominal mass compared to Earth or Moon) orbit the Earth with the
>same angular velocity as the moon. The L3 point is on the other side
>of Earth than the moon in the same orbital path, and is not very much
>affected by the moon's pull of gravity.
L3, Earth, L1, the Moon, and L2 are in a straight line, taking the Moon
to be in a circular orbit around the Earth and everything else as
negligible.
--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME. ©
Web <URL:http://www.merlyn.demon.co.uk/> - FAQqish topics, acronyms & links;
some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.
Dez Akin
> "Ross A. Finlayson" <r...@tiki-lounge.com> wrote in message
> news:3c6b9c1e.04021...@posting.google.com...
> >
> > There is not a 1 km/s barrier, even SERAPHIM achieved greater than 1
> > km/s.
> >
>
> There is no 1 km/s barrier, as in, "At 1 km/s, coilguns mysteriously stop
> working."
>
> However, no coil has ever demonstarted velocities much greater than 1 km/s.
> Certainly not 2 km/s.
Not much work is being done on high speed coilguns either. The
challenges in ramping up coilgun velocities, while definately
legitimate, are hardly insurmountable.
> >
> > The Space Elevator from Earth is somewhat of a ridiculous concept.
> >
>
> Do yourself a favor and read this book:
>
> http://www.amazon.com/exec/obidos/tg/detail/-/0974651710
>
> or this report:
>
> http://www.isr.us/Downloads/niac_pdf/contents.html
>
> ...and you will likely come to a different conclusion.
Cursory examination of these works are entheusiasm that dream away
details, such as relative economic cost of viable alternatives, the
sheer magnitude of the project, and notoriously bad failure modes. The
challenge of building a space elevator is far higher than making an
electromagnetic launch system, and I'd bet after the day is done,
using big dumb chemical rockets are more economical than a space
elevator; By the time we can afford such a monstrosoty it will be a
moot point.
Ross A. Finlayson
oscillations and a few others of those presentations about the Space
Elevator. I don't actually discard the concept as theoretically
impossible, I don't know enough to say that, but the Space Elevator
concept does entail many more unknowns than the Mass Driver concept.
Here's one point: it's unknown how to produce hundreds of thousands
of kilometers of continuous, flawless, "carbon nanotube" fiber. Its
costs are as well unknown. The costing presentation had an item for
the purchase of a factory to build the cables, at a very precise 1.02
billion dollars. They even figured out how big the spool would be,
somehow.
There are some worthwhile considerations of the dynamics of the cable,
the "Space Elevator" is a convenient thought experiment.
The Space Elevator would be a great thing to have, primarily because
it offers some method to bring things back from space down the
elevator. By the same token, the Mass Driver would be better for
sending some items to space, because the cost would be orders of
magnitude less than orders of magnitude less, where some probably
liberal estimators of mass driver cost claim 28 cents per pound to
orbit.
That c2 Wiki on the space elevator is a pretty good examination of the
concepts of the Space Elevator. It was Clarke himself who said the
space elevator might come into being fifty years after everyone
stopped laughing. It has links directly to the isr.us web
presentations about "Space Elevators".
What are failure modes of a "Space Elevator"? A mischievous child
with sharp scissors clips the line and the whole thing flies off into
space. Sympathetic oscillatory motion (Tacoma Narrows Bridge) makes
it unusable and destroys it. Space debris might impact it as it is in
space. Repair techniques of carbon nanotube fibers are nascent:
maintenance would suffer logistical problems, lack of maintenance:
catastrophic failure. If there are twenty cars on the line and the
cable snaps the cars would fall gently to the ground, or be lost in
space.
There's been two space elevator conferences, and eleven EML
symposiums.
The eminent professor with the chalkboard full of equations with "here
a miracle happens" is a cartoon, it's humorous. It's like the South
Park underpants gnomes, they know that cheap access to space is
profitable.
I'm skeptical of a "Space Elevator", but not dismissive. That is
quite skeptical.
Even I could build a toy coilgun.
The mass driver, electric gun launch to space, has its own adherents.
Its own mathematical simulations have been run and its own academic
papers have been written. Working models of electromagnetic launch
are quite involved in practical application.
I looked at several of those presentations about the Space Elevators,
thanks for suggesting that as I had already done so, each had at some
point the equivalent of "here be dragons."
EML has already been used to accelerate an item to several times the
speed of sound where rocketry then enabled the payload to achieve
orbit, in Australia. EML has already launched admittedly very small
masses to 39991 meters/second, more than thrice Earth's escape
velocity.
The megastructure is a grand concept. The mass driver perhaps would
not qualify. Name one thing on Earth that is 134 000 kilometers in
length.
Have you ever worked with cabling? Cables break under stress. On a
bridge there are thousands of redundant cables.
Anyways that's enough of my dismissal of the space elevator in favor
of the mass driver.
The Earth to Space Mass Driver doesn't launch to only GEO, it launches
past it, to the fringe of where an item will orbit the Earth and not
fall off to a solar orbit. The issue with that is that the moon
occupies Earth orbit.
I hope that you would be a little more positive on your claims on my
person. I've even learned new things since starting writing to the
sci.space newsgroups. (...)
Anyways, this thread is titled "Coilguns and EM Launchers", on the
newsgroup sci.space.policy, to be about discussions of policy and
technical issues directly pertaining to space exploration, here this
tangent has been about space elevators, hopefully we can further
outline the issues of coilguns and EM launchers, and keep the
discussions within the stated realm of the chartered interests of the
participants. I think it's appropriate if you want to advocate space
elevators or what-have-you.
Warm regards,
Ross F.
Joe Strout
dez...@usa.net (Dez Akin) wrote:
> > Do yourself a favor and read this book:
> >
> > http://www.amazon.com/exec/obidos/tg/detail/-/0974651710
> >
> > or this report:
> >
> > http://www.isr.us/Downloads/niac_pdf/contents.html
> >
> > ...and you will likely come to a different conclusion.
>
> Cursory examination of these works are entheusiasm that dream away
> details, such as relative economic cost of viable alternatives, the
> sheer magnitude of the project, and notoriously bad failure modes.
Clearly you need to do more than a cursory examination. Your
description is starkly at odds with the reality.
Dez Akin
> In article <dd43b4da.04021...@posting.google.com>,
> dez...@usa.net (Dez Akin) wrote:
>
> > > Do yourself a favor and read this book:
> > >
> > > http://www.amazon.com/exec/obidos/tg/detail/-/0974651710
> > >
> > > or this report:
> > >
> > > http://www.isr.us/Downloads/niac_pdf/contents.html
> > >
> > > ...and you will likely come to a different conclusion.
> >
> > Cursory examination of these works are entheusiasm that dream away
> > details, such as relative economic cost of viable alternatives, the
> > sheer magnitude of the project, and notoriously bad failure modes.
>
> Clearly you need to do more than a cursory examination. Your
> description is starkly at odds with the reality.
The one you make in your head? Existing launch technologies outperform
the cost of such a massive infrastructure project on an economic
basis; There are very few scenarios that drop the cost of creating a
magic space elevator with unobtainium without dropping the cost of
other alternatives faster. The proposal is to build a structure
several thousand times longer than the largest structure on earth with
chemicals that don't really exist yet, and thats supposed to be
competitive with other alternatives?
Its a neat concept, sure. Just get on the elevator to spaceland, whee.
And it works for small planetoids I'm sure, but it doesn't scale up. I
doubt the entire global output of 30 terabucks a year would pay for it
in less than a half century, and once we establish this great ziggurat
to the heavans, this great phallic monument to the tragedy of ignoring
opportunity cost, we can then dribble out occassional pebbles to the
sky?
Alex Terrell
> Anyways, this thread is titled "Coilguns and EM Launchers", on the
> newsgroup sci.space.policy, to be about discussions of policy and
> technical issues directly pertaining to space exploration, here this
> tangent has been about space elevators, hopefully we can further
> outline the issues of coilguns and EM launchers, and keep the
> discussions within the stated realm of the chartered interests of the
> participants. I think it's appropriate if you want to advocate space
> elevators or what-have-you.
>
Hmm - I think you forgot that you brought up the topic of earth to
orbit space elevators in some ramble answering to my question on moon
to orbit mass drivers.
Selective memory?
E.R.
Nice rhetoric. Too bad it bears only a passing resemblence to
reality. It's clear you've not troubled yourself to _read_ the
reference posted, which is a shame. If you're as smart as you claim,
you can devour the NIAC study in an evening, or less.
*CNT material is not unobtanium - it's gone from theory to kilograms a
day in the lab in under five years.
*Various sources claim it can be done between 6 - 20 billion dollars.
That's _doable_.
You do write an entertaining screed however. Don't let reality muddle
up your facts.
~er
Ross A. Finlayson
"ziggurat."
Space elevators aside, while they may be an intriguing concept, wth
"skyhooks" and even "wrecking balls from the sky", constructed of
"hundreds of millions of yards of perfect continuous carbon nanotubes"
what we want to accomplish in this discussion is the establishment of
the merit of the mass driver concept.
You raise a very important issue with the costs. While the government
arguably malfeasantly wastes billions of dollars a year of not their
money, it's difficult to assume what efforts of the private and public
sectors could decrease rocket launch costs. The "space shuttle" was
touted as offering $500 per pound to orbit, that value was mistaken,
hopefully, if not untrue, by about 500 times. Even the Soviet and
Chinese rocket launch systems cost thousands of dollars per pound to
orbit, and more for a pound to outer space. The Soviets (Russians)
have arguably the most efficient rocket systems.
Another critical issue is the technological capability.
The space elevator proponents claim that carbon nanotubes, single
walled carbon nanotubes with covalent bonds between each element of
the cylindrical "polymer", would be available in continuous process in
the hundreds of kilometers. They also assume that the tensile
strength is something about "130 Gigapascals", where that is not yet
actually realized in tests of the millimeter and centimeter length
carbon nanotubes which are some byproduct of arcing electricity
through a carbonaceous substance, as discovered by a Japanese fellow
in 1991. The tested as opposed to simulated strengths are somewhat
less than half of 130.
http://www.thespacereview.com/article/48/1
The railgun, as opposed to coilgun, is theoretically possible, it just
takes huge capacitor banks.
The coilgun has its issues of switching. Even though the electrons of
electricity flow at near the speed of light, there are issues of
energizing and then deenergizing the coils. People have happily
designed the coilguns, there are some technical issues.
The actual power used in the coilgun is not an appreciable issue, the
electricity costs for a launch of thousands of kilograms would be only
a few thousand dollars, less than the cost of the pod and its cargo.
The coilgun is only good for launching things, for items to return to
Earth from space they should be the aerospace plane, that has its own
huge liquid fuel tanks, boosts itself altogether to orbit, unloads and
loads and lands with the fuel tanks full of stuff and the cockpit full
of people.
Some microsatellites were launched by a jet flying straight up into
the air and launching a wing mounted rocket.
Anyways what would be good here is for a die-hard coilgun proponent
researching field applications of coilguns to step up and outline some
of more practical issues with regards to Earth to space coilgun
implementation. We've covered some of the issues here but speaking
for myself I'm not a coilgun scientist.
The reason I advocate coilgun launch to space is because it offers
costs that would make access to space feasible and an outpost on the
moon realistic, as well as the capacity to put a pair of satellites
around every body greater than a half a quadrillion kilograms in the
solar system. It's a challenge: design a feasible Earth to space
coilgun, and illustrate how its costs would revolutionize space
access.
Design an Earth to space coilgun. Sketch it on paper. Calculate the
numbers. Here a baseline for our discussion could be the 10 km
coilgun with exit speeds of greater than 11 km/s for 2, 4, 10, and 40
000 kilogram payload pods. The Earth is about 6 000 000 000 000 000
000 000 000 kilograms.
Support EGLTS.
Ross F.
Dez Akin
> > > description is starkly at odds with the reality.
> >
> > The one you make in your head? Existing launch technologies outperform
> > the cost of such a massive infrastructure project on an economic
> > basis; There are very few scenarios that drop the cost of creating a
> > magic space elevator with unobtainium without dropping the cost of
> > other alternatives faster. The proposal is to build a structure
> > several thousand times longer than the largest structure on earth with
> > chemicals that don't really exist yet, and thats supposed to be
> > competitive with other alternatives?
> >
> > Its a neat concept, sure. Just get on the elevator to spaceland, whee.
> > And it works for small planetoids I'm sure, but it doesn't scale up. I
> > doubt the entire global output of 30 terabucks a year would pay for it
> > in less than a half century, and once we establish this great ziggurat
> > to the heavans, this great phallic monument to the tragedy of ignoring
> > opportunity cost, we can then dribble out occassional pebbles to the
> > sky?
>
> Nice rhetoric. Too bad it bears only a passing resemblence to
> reality. It's clear you've not troubled yourself to _read_ the
> reference posted, which is a shame. If you're as smart as you claim,
> you can devour the NIAC study in an evening, or less.
Only the parts where they managed to gloss over the interesting bits,
like how to actually construct or finance such a project with real
world logistics. You don't need to read the whole report to see its
bullshit.
> *CNT material is not unobtanium - it's gone from theory to kilograms a
> day in the lab in under five years.
Thats a far cry from a building material. Artificial diamond went from
theory to kilogram in less than five years also. We're not making dams
or skyscrapers out of it. We're certainly not cranking out hundreds of
kilometers of it either for highway construction or any other
megaengineering project that has far more financial incentive for
earthbound interests.
> *Various sources claim it can be done between 6 - 20 billion dollars.
> That's _doable_.
Sure, if those claims were remotely in touch with reality. Natural gas
and oil pipelines of distances of only a few hundred kilometers cost
about that much, with access to far more desireable logistics and real
world building materials. These claims are in fantasyland. If the
price for the beanstalk actually plummeted by some magic to this
estimated cost, the economics that allowed that to happen are surely
just as likely to drop the cost of other launch techniques, such as
coilgun and light gas gun launchers.
> You do write an entertaining screed however. Don't let reality muddle
> up your facts.
Well, though my primary aim is to highlight the questionable economics
and engineering logistics, to draw questions, I suppose entertaining
those who dismiss such skeptisism is at least better than disgust.
E.R.
> economic...@yahoo.com (E.R.) wrote in message news:<a11b144e.04021...@posting.google.com>...
> > dez...@usa.net (Dez Akin) wrote in message news:<dd43b4da.04021...@posting.google.com>...
> >
> > reality. It's clear you've not troubled yourself to _read_ the
> > reference posted, which is a shame. If you're as smart as you claim,
> > you can devour the NIAC study in an evening, or less.
>
> Only the parts where they managed to gloss over the interesting bits,
> like how to actually construct or finance such a project with real
> world logistics. You don't need to read the whole report to see its
> bullshit.
Dr. Edward's study was an engineering study, not a prospectus or
blueprint on _how_ to build one. It _did_ have a chapter on how to
deploy an elevator - although the bits on how to construct the ribbon
material are of course not written yet.
>
> > *CNT material is not unobtanium - it's gone from theory to kilograms a
> > day in the lab in under five years.
>
> Thats a far cry from a building material. Artificial diamond went from
> theory to kilogram in less than five years also. We're not making dams
> or skyscrapers out of it. We're certainly not cranking out hundreds of
> kilometers of it either for highway construction or any other
> megaengineering project that has far more financial incentive for
> earthbound interests.
If CNT can be made economnically, it will be - it's too promising as
material for it not to be. I don't recall if Rice gave a breakdown
for how much it cost, but a recent experiment there spun hundreds of
meters of the stuff in only a few hours.
Which is a far cry from the amounts needed (let alone the amount
needed for prosaic applicatoins like body armour and building
materials.
>
> > *Various sources claim it can be done between 6 - 20 billion dollars.
> > That's _doable_.
>
> Sure, if those claims were remotely in touch with reality. Natural gas
> and oil pipelines of distances of only a few hundred kilometers cost
> about that much, with access to far more desireable logistics and real
> world building materials.
Unh, that's like comparing apples and dump trucks.
> > You do write an entertaining screed however. Don't let reality muddle
> > up your facts.
>
> Well, though my primary aim is to highlight the questionable economics
> and engineering logistics, to draw questions, I suppose entertaining
> those who dismiss such skeptisism is at least better than disgust.
I'm not dismissing, I'm pointing out some facts and opinions that I
have. Takes all kids of people to make the world go round.
~er
Mike Combs
> Earth-Moon-Gnome 3 body system, there are the five Earth-Moon LaGrange
> points L1, L2, L3, L4, and L5. L1 is directly between Earth and Moon,
> or rather slightly ahead of Moon's path, much nearer the moon than
> Earth, where it is held back by Moon's gravity in its orbit around the
> Earth to match the moon's angular velocity. The L2 point is past the
> moon and slightly behind the moon and as well objects at that point
> (with nominal mass compared to Earth or Moon) orbit the Earth with the
> same angular velocity as the moon.
Sounds like we're assuming the same coordinate system.
> So, the gnome would
> hang out at the Earth-Moon L4 or L5 point.
>
> The gnome's position is more stable at the L4 or L5 point, except the
Sounds like you're designing your own lunar catapult plan. I'm not a
physicist, so I can only discuss the specific plan which was arrived at
during detailed NASA-funded studies, and was published for peer-review.
> If over sixty years Americans can build hundred of thousands of miles
> of interstate road system, then they can build a two hundred mile
> mag-lev tunnel to the stars that offers comfortable 2-G acceleration
> to space for a ticket of hundreds of dollars, one way.
I'd be perfectly happy with one that could do it with 10 G's. Most
reasonably healthy people ought to be able to tolerate that briefly, and the
launcher would only cost roughly 1/5 as much.
Mike Combs
news:d81e59c9.04021...@posting.google.com...
> 2. If the pellet were to miss the catcher, it would leave lunar orbit
> and go into an Earth orbit, which isn't ideal.
If I recall correctly (been a few years), O'Neill said that the payloads
would enter a temporary lunar orbit which would soon impact the lunar
surface.
Joe Strout
> > Nice rhetoric. Too bad it bears only a passing resemblence to
> > reality. It's clear you've not troubled yourself to _read_ the
> > reference posted, which is a shame. If you're as smart as you claim,
> > you can devour the NIAC study in an evening, or less.
>
> Only the parts where they managed to gloss over the interesting bits,
> like how to actually construct or finance such a project with real
> world logistics. You don't need to read the whole report to see its
> bullshit.
Yes, with eyes closed and fingers in your ears you won't have to face
anything that contradicts your preconceived notions. A classic ostrich
defense against reality.
But hey, it's your world, you can choose to live in it or not.
Fortunately it really doesn't matter what you think. Things will
develop according to reality, and those who couldn't be bothered to
study a subject before forming an opinion will simply be left behind.
>plonk<
Marvin
You sure sound like him
Ross A. Finlayson
> > of interstate road system, then they can build a two hundred mile
> > mag-lev tunnel to the stars that offers comfortable 2-G acceleration
> > to space for a ticket of hundreds of dollars, one way.
>
> I'd be perfectly happy with one that could do it with 10 G's. Most
> reasonably healthy people ought to be able to tolerate that briefly, and the
> launcher would only cost roughly 1/5 as much.
>
> --
Hi,
I'm not High Voltage but I have some questions about electromagnets.
I'd like to know more about how a coilgun works, particularly a
coilgun of sufficient dimensions to launch several thousand kilograms
to space from Earth.
http://groups.google.com/groups?selm=963n1v%24gmc%241%40flotsam.uits.indiana.edu
http://www.es2.ecs.toyama-u.ac.jp/masugata/masugata.html
Masugata proffers a design for a 10 km/s coilgun.
The pod is apparently supposed to have its back end, the base of the
projectile, be a superconducting, or other extremely conductive
material, armature to exploit the Meissner effect.
I continue typing "coilgun" and searching for coilgun information,
probably should also look for "coil gun".
http://groups.google.com/groups?selm=5q2i7k%249dm%40news.scruz.net
http://groups.google.com/groups?selm=3rscah%24bs5%40news.rain.org
http://groups.google.com/groups?selm=D501sp.Dw3%40ranger.daytonoh.ncr.com
http://groups.google.com/groups?selm=21477%40crg5.UUCP
http://home.adelphia.net/~gsj/abstract.txt
http://groups.google.com/groups?selm=ee5t7soveskdlqqfe2cm9cktdjum8r101m%404ax.com
http://groups.google.com/groups?selm=higgins-2011982011470001%40132.206.200.31
http://yarchive.net/space/exotic/mass_drivers.html
So anyways I look to my introductory electronics material here,
"electronics one-seven", revised 2'nd ed., Mileaf(ed.), 1978, to get a
grasp on a parts list of a toy coilgun. I think I intend to run it
from wall current, alternating current at 60 Hz and 115 Volts, but I
plan to use direct current to power the coils. I figure from this
reading that I need to build a full wave and a bridge wave rectifier
with the choke inductor regulators to get some 110 and 220 Volt
sources of positive and negative polarity direct current, 110 Volts to
charge the coil and 220 Volts to reverse each coil. I think many
smaller coils is better than one large coil, using perhaps 10 gauge
magnet wire. Then, I need to switch the power to the coils, I might
be looking to thyristor tetrodes or triacs or silicon controlled
rectifiers, SCRs, or thyratrons, tube electronics, for handling the
power load switching, probably not IGBT. I figure the coils should go
on mountings that can be clamped variously at different locations,
distances, about the launch tube, perhaps a glass tube, to allow
constant timing to affect the variably space coils. for fixed size
projectiles. This would be in lieu of some understanding of how to
switch the coils from the actual physical effect of the projectile
entering the coil. Then, I should be able to pour BBs or bearings
into a hopper and have them ejected forthwith.
I go to a supply house and radio shack and talk to them and look at
their products and catalogs. I might be able to aquire some tubes,
thyratrons.
What I need to figure out is how to have the current go from one coil
to the next. I think I can get 100 amps or more out of wall current.
It might be smarter to just use a 12/13.8 Volt battery.
Hey, here's an educational website: http://www.allaboutcircuits.com/
. I still can't correctly use many of these words from the
electromagnetic domain, but progress occurs.
I'm still under the possible misconception that I can apply DC of one
polarity to the coil to draw the projectile into the coil, and of the
opposite polarity to propel the projectile from the coil.
So anyways I figure I'll get some magnet wire, and then I only want to
have one row per coil, eight or nine turns per coil, so the ends go
into some connector to mains wire, so it is simple to patch each of
the coils into the circuit. Then, I need to use the SCR or other
electronic switch to guide the power into the coils, with various
bleeder resisters and diodes to prevent back EMF. The coils go around
sleeves of metal piping the size of the coil to resist coil
contraction. These slide over a glass or plastic tube. For some
reason I don't think I have to use capacitors except in the regulator,
using plain current. Timing is to be constant rate with sliding the
coils. It should have LEDs to illustrate the energized coils and
their polarity. Each coil could be positively energized and then
negatively energized as the projectile enters the coil, a pull-push
design.
It seems like there are hundreds of illustrated coil gun projects on
the web.
The tube electronics can handle a lot of power.
The pod can be designed to have most any magnetic characteristic.
Support EGLTS. Support parallel and alternative launch tracks.
Ross F.
George William Herbert
>> *CNT material is not unobtanium - it's gone from theory to kilograms a
>> day in the lab in under five years.
>
>Thats a far cry from a building material.
The specific claim... that carbon nanotubes are not 'here yet',
is unarguably true. I can't buy kilometers of it on spools like
I can with spectra or Toray T1000 or the like.
The general claim... that carbon nanotubes are not going to get
to being viable, is by no means certainly true.
The theory predicts behaviour that is adequate for the
required engineering usage in terms of tensile strength.
The manufacturing capabilities have gone from several orders
of magnitude too small volume and length to roughly one order
of magnitude too short and too low volume, per production site.
There is no clear barrier in the way of continuing to develop
them into adequate materials for space elevators.
The odds that some new unforseen problem will come up that
prevents them being converted into useful engineering products
are non-zero but also not defensibly overwhelming.
>Artificial diamond went from
>theory to kilogram in less than five years also. We're not making dams
>or skyscrapers out of it.
If we could produce artificial diamond in infinite quantities,
at its current prices and material properties, it would still
not be a major construction material. The role of composites
and bending behaviour in engineering materials is underrated
in naive analysies.
>We're certainly not cranking out hundreds of
>kilometers of it either for highway construction or any other
>megaengineering project that has far more financial incentive for
>earthbound interests.
None of which it would have any engineering utility for anyways.
Diamond isn't just not being used because it's too expensive.
It's not being used because it's not a good engineering material
in bulk either.
Certain specific applications? Sure. Road surfaces, building
columns or floors? Please pay more attention to detail.
-george william herbert
gher...@retro.com
Ross A. Finlayson
space offers primarily one benefit over rocketry: cost efficiency.
Rocketry enjoys a special place in space technology: that being the
only current method to launch mass from Earth to space. As well it is
stamped upon the imagination of many with such concepts as "countdown"
and "liftoff".
We can look forward to the use of rocketry, particularly within space,
albeit perhaps ion motor "rocketry", or for fusion rocketry, for a
long time, but it will always be the case that a less expensive launch
method would allow increased access to space.
It is a point well made that diverting some of the resources used in,
for example, the space shuttle or International Space Station towards
research in escape velocity electromagnetic cargo launchers would
offer much more ready advances in that study than in the saturated
field of rocketry, rocketry is in many ways a mature technology where
breakthrough results, although welcomed, are not to be expected and
theoretical and technological limits of rocket efficiency are already
reached. The diminishing marginal returns of reliance on rocket
launch, uneconomically, diminish.
That is not to say that economies of scale and mass production might
not lower some costs of rocketry applications, but it still would hold
that electric or other gun launch to space, the "train to space",
combined with or muchly separate from rocketry, offers increased
returns on investment, and some capabilities which don't exist.
The EGLTS installations should not necessarily have ground broken
tomorrow, there are unknowns in how to build a pure EGLTS system,
although there are not hypothetical limits and bees can't fly. What
there should be are more dedicated resources to the promise and
problems of EGLTS, because the probable reward of such a system is
high.
Imagine if it only cost ten dollars per pound to launch
acceleration-resistant cargo to the moon, hundreds of thousands of
kilometers away. We, as a species, could then realistically afford to
install life on the moon, that could almost support itself, and easily
could.
Various researchers in the field make sweeping claims about EGLTS: it
could be built, today, with almost off the shelf components, it could
put two thousand tons a year, or more, on the moon, and amortized
launch costs could be less than a dollar a pound.
If we take the example of the Space Shuttle Orbiter's "$500", where it
costs "$25,000", then if the EGLTS system, functional, cost _five
hundred times_ as much as predicted, it would cost less than "$500".
The day after an EGLTS installation was fixed in design and began, a
new field effect result might make its design, if not concept,
obsolete. If that were the case it would affect a lot of things, but
EGLTS would still offer a reduction in orders of magnitude of the cost
of largescale access to space.
Imagine eight or ten EGLTS installations spread over a few hundred
square kilometers in the middle of the desert somewhere, with the
people mover track terminus in a suburban area some hundreds of
kilometers west. Fantastic?
I think rocketry is great, and even inspiring, although perhaps fat
and complacent.
Earth is a tiny pock in the solar system, and the brilliant jewel and
cradle of life. The vast expanses surrounding it contain millions of
times the raw materials than could ever be extracted from our planet
without destroying its resilient yet fragile ecosystem, supporting
life on the planet. We _could_ have thousands upon thousands of
people happily working and living in space, _in our time_, but we have
to get there first.
There are economic, cosmological, and Darwinian/Malthusian imperatives
to colonize space. It will happen, and it could start.
Why electromagnetic "gun launch" to space? It would be cheaper! It
might also be faster, better, and safer. Those would be
justificational notions for "new and improved" rocketry methods, a
"space elevator", "teleporters", "antigravity", "ether drive", or any
other imagined method to improve the ability of getting stuff off of
the planet. They are justifications for EGLTS because it is actually
not beyond rationality.
Support alternate tracks. Promote EGLTS.
Ross F.
George William Herbert
Please stop yammering on about coilguns until you have
actually read the references which have been pointed
out to you which show why they are having serious problems
scaling up much past a kilometer per second of muzzle velocity.
They don't work to orbital velocities.
They are not physically proven to never be possible to work,
but, they don't work at this time, and we do not have in hand
technical approaches expected to solve that problem.
Just because a technology seems sexy on first inspection does
not mean that it holds up under detailed engineering and
science analysis. The difference between pointless enthusiasm
and serious, useful contribution to advancing exploration of
space is that serious, useful contributors either have figured
out how to do the math and engineering and physics and do so
to independently crosscheck things, or pay a lot more detailed
attention to people who do work the numbers out.
In trying to advocate the use of a technology that is known
to not work, you are in fact impeding progress towards real
viable solutions.
I know you mean well. But you need to move beyond your
infatuation and start to learn technology and math.
If you like "gun" launch then look towards the methods
that are known to work, even with some disadvantages.
Various Laser schemes, railguns, multistage light gas
guns are getting up there.
Railguns can do the required velocity now, the only issues are
cost of scaling up the pulse power and rail erosion. But in the
end, rail erosion can be managed by replacement if that's necessary.
Various laser schemes could be demonstrated on small scale
reasonably quickly and seem technically low risk.
-george william herbert
gher...@retro.com
Ross A. Finlayson
applied acceleration can be lower and otherwise more stricly
controlled, and the coil is lower maintenance and in ways higher
reliability than degrading rails, or other non-contactless methods,
and besides the railgun none of the other gun launch techniques have
achieved necessary velocity parameters of 12 km/s.
As I continue to "yammer", a fine verb, about coilguns, you'll notice
that I'm actually interested in the technical shortcomings of the
coilgun approach. We've even covered on this thread, albeit casually
and superficially, a broad survey of the study of coilguns and EML,
including items like the late-90's "coilguns are feasible with almost
off the shelf parts" and Masugata's 10 km/s design.
I want to harsh upon the "1 km/s" barrier of the coilgun, and I'd be
happy to harsh upon the "3 km/s" barrier, keeping in mind that 200
years ago it was common knowledge that anything going faster than a
mile a minute would explode. A hundred years ago coilguns or "linear
induction motors" were barely known to be, seventy some years ago the
coilgun was considered for launch to space, thirty-some years ago
students were accelerating at 1000's of G's, fifteen years ago as part
of "SDI" a national laboratory "poisoned the well", and today coilguns
launch hypervelocity tank rounds from mobile platforms.
We are working the numbers out: a ten kilometer, or perhaps extended
coilgun with micro-, nano-, and pico-second switching, available in
three dollar chips from "Radio Shack", accelerates a 10000 kg
projectile at 100 G's using some 80 gigajoules. Those are estimates,
I will bust out a slide rule on numbers. I'll agree that I am quite
ignorant about the physics of the coilgun, in fact it was upon this
thread that I have learned much of this information, as you can
determine from the progress of the thread, from sectional density to
pulsed power and hysteresis to alternatives to g-nomes.
http://www.google.com/search?q=Landau-Lifshitz-Gilbert
Consider Apollo, a huge program from the sixties and seventies.
Before it began, it was unknown how to launch anything to the moon,
and it was done. Skylab then was an orbital station at thousandths
the expense of ISS.
George, you're a space enthusiast, and moderator of sci.space.tech, if
there had to be 200 000 tonnes of Earth materials, building supplies,
fuel, rations, and other hard cargo, on the moon in ten years, how
could it be done?
I ask myself that question, for wanting to contribute to the moon base
discussions, and the answer is a launch method that doesn't require
90% of the mass that leaves the Earth to be fuel, in a giant,
wasted/expended, booster rocket, scaling in quantity to display its
quality error rate. It's a launch method the machinery of which
exists largely on the ground, easily reparable and monitorable. It's
a launch method that uses electricity instead of volatile, explosive,
and often poisonous fuels, except for the pods' hardened control
systems.
We continue to discuss coilgun mechanics heartily in this thread,
about coilguns and EM launch, and we have addressed not only some
aspects of the state of the art, but also problem areas, and concepts
for new direction, and how to build a toy one out of easily available
parts. We've even seen that some of the popular misconceptions about
coilguns have been debunked, and some very real current technical
limits are not what they once were.
Rocketry, the current launch method, has its advantages, but we don't
have any near-term breakthroughs in the art and science of rocket
propulsion that are going to increase their safety and reliability and
lower their costs.
I'm not a coilgun fanatic, I'm a space enthusiast, the escape velocity
coilgun, when its technical kinks are ironed, offers a new avenue to
space.
I think I can use the 556 integrated circuits with high tolerance
resistors to emit constant rate timing pulses in the microseconds,
perhaps with op-amps to battle hysteresis with power. That might
allow a toy coilgun with measurable velocity from twenty dollars of
parts. I fully expect that the pulsed-power problems of the escape
velocity coilgun wil be solved.
We're not especially unrealistic here: we're taking a hard look at
coilgun technology to launch stuff into space.
Ross F.
Alex Terrell
> "Alex Terrell" <alext...@yahoo.com> wrote in message
> news:d81e59c9.04021...@posting.google.com...
>
> > 2. If the pellet were to miss the catcher, it would leave lunar orbit
> > and go into an Earth orbit, which isn't ideal.
>
> If I recall correctly (been a few years), O'Neill said that the payloads
> would enter a temporary lunar orbit which would soon impact the lunar
> surface.
>
is then in an Earth orbit. Granted, it will be a moon crossing Earth
orbit, and will likely impact the moon after a while. But could it
equally impact the colonies at L4 / L5?
Mike Combs
> "Mike Combs" <mike...@nospam.com_chg_nospam_2_ti> wrote in message
news:<c0tofk$66f$1...@home.itg.ti.com>...
> >
> > would enter a temporary lunar orbit which would soon impact the lunar
> > surface.
> >
> I don't see how it could enter a lunar orbit if it goes through L2. It
> is then in an Earth orbit. Granted, it will be a moon crossing Earth
> orbit, and will likely impact the moon after a while. But could it
> equally impact the colonies at L4 / L5?
I'll go back and have another look tonight, and post what I find tomorrow.
John Savard
<mike...@nospam.com_chg_nospam_2_ti> wrote, in part:
>"Alex Terrell" <alext...@yahoo.com> wrote in message
>news:d81e59c9.04022...@posting.google.com...
>> "Mike Combs" <mike...@nospam.com_chg_nospam_2_ti> wrote in message
>news:<c0tofk$66f$1...@home.itg.ti.com>...
>> > If I recall correctly (been a few years), O'Neill said that the payloads
>> > would enter a temporary lunar orbit which would soon impact the lunar
>> > surface.
>> I don't see how it could enter a lunar orbit if it goes through L2. It
>> is then in an Earth orbit.
Why? L2 is an *unstable* equilibrium point. So, depending on the
velocity of a body passing through it, such a body can certainly fall
to the ground of the Moon - or the Earth.
Even with L4 and L5, the stable equilibrium points, orbits around
those points are only possible with a limited range of velocities -
even planets have escape velocities.
>I'll go back and have another look tonight, and post what I find tomorrow.
John Savard
http://home.ecn.ab.ca/~jsavard/index.html
gbaikie
It could have a chance of traveling to any of the Sun/Earth/Moon L
points [or even anywhere in the solar system's super highway- and
therefore any planetary orbit or solar orbit], but it won't have a
very fast velocity [much less than speed of a bullet]. And it wouldn't
add a significant a threat- there are billions of objects pellet size
or larger in the solar system. And if you consider that any L-point is
a very huge volume of space it's unlikely that one of these pellets
passing through a L-point would hit a station or colony.
Though it's possible in transiting between say Sun/Earth L-2 and L-1
near Earth say around GEO, the pellet could have a higher velocity. Or
it's on trajectory to say impact Earth or the Moon it would have a
fast velocity relative to things in low orbits.
Mike Combs
"Mike Combs" <mike...@nospam.com_chg_nospam_2_ti> wrote in message
payloads
> > > would enter a temporary lunar orbit which would soon impact the lunar
> > > surface.
> > >
> > I don't see how it could enter a lunar orbit if it goes through L2. It
> > is then in an Earth orbit. Granted, it will be a moon crossing Earth
> > orbit, and will likely impact the moon after a while. But could it
> > equally impact the colonies at L4 / L5?
>
> I'll go back and have another look tonight, and post what I find tomorrow.
Alex, you are exactly right. What I had recalled reading was some
Congressional testimony O'Neill had given. A Senator had asked him what
happens if the catcher misses, and he said that the payload would orbit and
then eventually re-impact the lunar surface in a 1,000 years or so. So he
definitely meant Earth (and not lunar) orbit.