Gun lanched space craft
Mark Harrison
do know that Geared Bull (?) once worked with the Canadians and the US
(HARPS Project) towards that goal.
Javier
You mean the man that was bold enough to defy the Mossad? He tried
sub-orbital probes with refurbished naval long-range guns. But the results
were disappointing, the money run out, or both...
Javier
BeforeThe name is --I'm not sure, anyway-- "Gerard Bull"
Mark Harrison escribió en mensaje <71lg44$ijd$1...@news.ipa.net>...
Nicholas Landau
>Anyone have any info on the use of guns to launch Satellites into orbit. I
>do know that Geared Bull (?) once worked with the Canadians and the US
>(HARPS Project) towards that goal.
It is not a new idea by any means. Did you ever read Verne's "From the
Earth to the Moon?" Our heroes are fired from a giant cannon located
in Florida and reach the moon and a ballistic course. I don't remember
how they cushioned their landing in that book.
Heilein has a neat description of ballistic travel in an otherwise
miserable book, _Friday._ He had passenger projectiles being fired
from one side of the world to another, although never into permanent
orbit as you mentioned above.
I heard that some "Canadian artillary genius" had devised a plan
to fire satellites into orbit from the ground. I don't know any
more than that, however.
M. James
ran during the late '60s (if I recall correctly). He used a modified 16"
naval gun, somewhere in the Caribean. The project was cancelled before a
satellite was launched - lack of funds. The scheme was to send a
projectile straight up into space (that part was done several times). To
get it into orbit, the projectile would have a rocket engine which would
fire near the apogee of the trajectory.
Mike James
Mark Harrison <bgc...@ipa.net> wrote in article
<71lg44$ijd$1...@news.ipa.net>...
bja...@ea.com
ballistics testing, using three welded-together US Navy WW I naval cannons
bobbyu
> Gerald Bull was a prof at McGill University (Montreal). The HARP project
> ran during the late '60s (if I recall correctly). He used a modified 16"
> naval gun, somewhere in the Caribean.
If I remember right, he used two guns welded end-to-end. "Launch" site was
Bermuda.
> The project was cancelled before a
> satellite was launched - lack of funds. The scheme was to send a
> projectile straight up into space (that part was done several times). To
> get it into orbit, the projectile would have a rocket engine which would
> fire near the apogee of the trajectory.
There was a made-for-cable movie about him a while back. Frank Langella
played Bull.
> Mike James
bobbyu
Hiram Berry
>
> Bull also had built a very big gun at North Hatfield, Quebec, for
> ballistics testing, using three welded-together US Navy WW I naval > cannons
I'd think that such a system could be useful for delivering bulk raw
material to orbit, but because of the G forces involved in accelerating
down the barrel probably not applicable to launching entire operational
spacecraft. If the method really works it seems like it might be a very
cheap way of shooting blocks of solid H2 into a high energy trajectory
for orbital rendezvous.
So has anyone done any analysis to see whether the method is really
feasible? Specifically, are the engineering requirements for the
projectile reasonably attainable-- eg., can the thermal stresses
inherent, even for a short period of time, in firing a shell through
standard atmospheric density at 8 km/sec be handled by known active
ablatives? And just how much projectile kinetic energy will be lost to
atmospheric drag for a typical shell geometry-- small enough to still
make the method economically advantageous over rockets?
-- Hiram Berry
Jim Cobban
Nicholas Landau <nla...@eden.rutgers.edu> wrote:
>"Mark Harrison" <bgc...@ipa.net> writes:
>
>>Anyone have any info on the use of guns to launch Satellites into orbit. I
>>do know that Geared Bull (?) once worked with the Canadians and the US
>>(HARPS Project) towards that goal.
>
>Earth to the Moon?" Our heroes are fired from a giant cannon located
>in Florida and reach the moon and a ballistic course. I don't remember
>how they cushioned their landing in that book.
One of the amazing things about Verne's book (written almost exactly 100
years before the actual flight) is that he rigorously limited himself to
scientifically provable elements, even if they restricted what could happen
in the story. As a result he was unable to land his astronauts on the moon,
since they could not carry enough rockets to cushion their landing on the
Moon, although the spacecraft did include rockets intended for course
correction. Verne's rigor meant that his book (actually two short books
published a year apart) is BY FAR the most accurate representation of the
first flight to the moon written by ANY fiction writer at any time right up
to the public announcement by NASA of the details of their plans. I cannot
recall all of the details which Verne got right in 1870, but the following
are some:
1) The first flight to the Moon would be launched by the USA. Bear in
mind that at the time he made this prediction the USA was not by a long
stretch a world power either politically or economically or
scientifically.
2) The first flight to the Moon would be launched from central Florida.
Verne has a long analysis of why this would be, including a prescient
analysis of American politics. He picked a spot near Orlando less than
100 miles from KSC.
3) The crew would comprise three men.
4) The spacecraft would be manufactured principally of aluminum, a metal
which at the time had only been available in volume quantities for
about 10 years.
5) The dimensions and shape of the spacecraft in his novel are within 20%
of those of the Apollo.
6) The flight to the Moon would take about 4 days. Despite the fact that
this is forced by the laws of physics, it is amazing how many fiction
writers failed to include this.
7) The spacecraft uses rockets for mid-course corrections. Verne did not
think to use rockets for the initial propulsion, but then he was
writing almost a quarter century before Tsiolkovsky.
8) The first flight to the Moon would not land! Despite the enormous
temptations, which no other fiction writer in the following century
could resist, Verne determined that there was no feasible way to
achieve a landing using the available technology and therefore he did
not have them land. Note that Apollo 8, the first manned flight to the
Moon, DID NOT LAND!
9) The first flight to the Moon would use a free-return trajectory. This
was NASA's plan up until the delays caused by the Apollo 1 fire forced
them to skip this step. In Verne's case it was forced by the lack of
sufficient delta V in the on-board rocket engine.
10) The spacecraft would return for a water landing in the Pacific Ocean!
Again Verne could not see a feasible technology for reducing the return
speed to the point where a safe landing could be made. I have seen it
claimed that not only did he predict the return in the Pacific, but
that he specified the correct location in the Pacific to within less
than 200 miles of the splashdown site of Apollo 8, the first real-life
flight to the Moon! In the novel Verne explains the calculations which
result in the specified longitude and latitude. They return to the same
latitude from which they departed and the longitude is due to the
amount of rotation of the Earth since their departure. This is indeed
the same laws of physics which compelled the Apollo 8 to land in the
same location.
Unfortunately the gun technique which he employed is unfeasable because a
gun cannot propell a projectile to a greater velocity than the gas particles
of the explosion, about 2.5 km/s, no matter how much explosive you pile up.
Also, of course, the water baffles which he used to protect the astronauts
from the explosion would do nothing to prevent them being turned into a thin
layer of jam in the bottom of the spacecraft. He also failed to accurately
understand weightlessness. Only objects expelled from the spacecraft
through the airlock are weightless. Objects inside the spacecraft carry
weight in the novel except at the L1 point where the gravity of the Earth
and Moon cancel out.
--
Jim Cobban | jco...@nortel.ca | Phone: (613) 763-8013
Nortel Networks (MED) | FAX: (613) 763-5199
harmon_...@my-dejanews.com
I'm not sure, but I was reading where Lawrence Livermore is experimenting
with a gas gun that can accelerate stuff to mach 8, and using it to work with
scramjet designs. I think the theory of using a big gun to start out a
scramjet/rocket to shoot bulk material to orbit is great. One of the major
limiting factors of large living areas in space is just plain water. It
doesn't make sense to send up bulk water on the shuttle. If you had a gun
shooting a couple of tons up once or twice a day, that would ease that
difficulty considerably.
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
Bill Bonde
>
> Unfortunately the gun technique which he employed is unfeasable because a
> gun cannot propell a projectile to a greater velocity than the gas particles
> of the explosion, about 2.5 km/s, no matter how much explosive you pile up.
>
from a balloon? A canon attached brought to 100,000 feet by a hydrogen
balloon would fire a projectile at, say 2.5 km/s. This would, I think,
have to be straight up due to the weight of the canon itself determining
the aim. Then at some higher altitude to be determined, a shaped charge
would fire the object being inserted into orbit East. Perhaps ganged
shaped charges could even be used to further accelerate the projectile.
Andrew Higgins
> bja...@ea.com wrote:
> >
> > Bull also had built a very big gun at North Hatfield, Quebec, for
> > ballistics testing, using three welded-together US Navy WW I naval > cannons
>
> I'd think that such a system could be useful for delivering bulk raw
> material to orbit, but because of the G forces involved in accelerating
> down the barrel probably not applicable to launching entire operational
> spacecraft.
You might tell that to the U.S. Navy. They just introduced a new
gun-launched rocket (ERGM--Extended Range Guided Munition) which will be
fired from standard naval 5-inch guns. Each shell carries a GPS receiver
and a fiber-optic laser gyroscope. The laser gyros used are going to be
commercially available gyros developed for the automobile industry and
cost about $25 a piece. Apparently, no special modifications are required
to withstand the 10,000 g's of gun-launch.
>
> Specifically, are the engineering requirements for the
> projectile reasonably attainable-- eg., can the thermal stresses
> inherent, even for a short period of time, in firing a shell through
> standard atmospheric density at 8 km/sec be handled by known active
> ablatives?
>
In a word, "yes." Quite a few people have looked at this for a variety of
gun-launch-to-orbit concepts (railgun, coilgun, gas gun, ram accelerator,
etc.) and the answer is that standard ablatives are good enough for the
job. Of course, you might not need ablatives at all. Take a look at:
http://asm.arc.nasa.gov/projects/sharp/sharp.shtml
>
> And just how much projectile kinetic energy will be lost to
> atmospheric drag for a typical shell geometry-- small enough to still
> make the method economically advantageous over rockets?
>
For a muzzle velocity of 8-10 km/s, the vehicle looses 1-2 km/s due to
drag during atmospheric transit.
As for "economically advantageous", sounding rocket packages gun-launched
by Project HARP in the 1960's were at least an order of magnitude cheaper
than competing sounding rockets.
--
Andrew J. Higgins Department of Mechanical Eng.
Shock Wave Physics Group McGill University
hig...@mecheng.mcgill.ca Montreal, Quebec
Allen Thomson
>In article <3651DABF...@burningbridges.com>,
>burn...@burningbridges.com wrote:
>
>> bja...@ea.com wrote:
>> >
>> > Bull also had built a very big gun at North Hatfield, Quebec, for
>> > ballistics testing, using three welded-together US Navy WW I naval > cannons
>>
>> I'd think that such a system could be useful for delivering bulk raw
>> material to orbit, but because of the G forces involved in accelerating
>> down the barrel probably not applicable to launching entire operational
>> spacecraft.
>
>You might tell that to the U.S. Navy. They just introduced a new
>gun-launched rocket (ERGM--Extended Range Guided Munition) which will be
>fired from standard naval 5-inch guns. Each shell carries a GPS receiver
>and a fiber-optic laser gyroscope. The laser gyros used are going to be
>commercially available gyros developed for the automobile industry and
>cost about $25 a piece. Apparently, no special modifications are required
>to withstand the 10,000 g's of gun-launch.
[snip]
When this question was asked at a program review of the LLNL gas-gun
project a few years ago, the answer was that electronics and other
components good to 30,000 g were off-the-shelf items, and there
was little doubt that 100,000 g could be done if needed.
Jens Lerch
> 10) The spacecraft would return for a water landing in the Pacific Ocean!
> Again Verne could not see a feasible technology for reducing the return
> speed to the point where a safe landing could be made. I have seen it
> claimed that not only did he predict the return in the Pacific, but
> that he specified the correct location in the Pacific to within less
> than 200 miles of the splashdown site of Apollo 8, the first real-life
> flight to the Moon!
Jules Verne's book is on-line at
http://www.inform.umd.edu/EdRes/ReadingRoom/Fiction/Verne/TripAround/
In chapter 20 the splashdown is said to be both at 27°07'N, 41°37'W
(i.e. in the middle of the Atlantic) and 200 miles off the Californian
Peninsula. Either Verne made a mistake or he used a different prime
Meridian.
Apollo 8 landed at 8°N, 165°W, about 800 miles South of Hawaii, which
is way off from both the Californian Peninsula and the Atlantic.
> In the novel Verne explains the calculations which
> result in the specified longitude and latitude. They return to the same
> latitude from which they departed and the longitude is due to the
> amount of rotation of the Earth since their departure. This is indeed
> the same laws of physics which compelled the Apollo 8 to land in the
> same location.
Apollo 8 spent about a day in lunar orbit, thus Verne's calculations
aren't applicable.
--
Jens Lerch
jle...@geocities.com
http://www.geocities.com/CapeCanaveral/2221
Richard Kaiser
A gun launch is only 20% of the solution.
The gun would place the playload into an orbit that would include the gun if
the earth were not rotating. In other words, the payload would return to
earth. Turning this ballistic trajectory into an orbit requires a delta-V
burn in orbit that is four times bigger than the delta-V imparted by the
gun.
Richard Kaiser
Rick
> burn in orbit that is four times bigger than the delta-V imparted by the
> gun.
Richard Kaiser
Maybe my head is screwed on wrong but at 100miles up, isn't gravity
and resistence from air less? Why would a second burn be 4X bigger?
Please keep the answer simple, I'm no rocket scientist.
How often would a station cross a fixed spot? Could you build this
gun site on a mountain, near the equator and have a booster,of sorts,
straped to the back of the payload?
Rick Keenan
--
I once crashed a plane just to watch it die.
bil...@pacbell.net
your feedback as to workability. 1. I saw an experiment that showed that
living things can live in a very high magnetic field. ( a grasshopper in this
case suspended in a field high enough for it to be weightless). 2. Taking
the idea of the Panama canal of using natural resources in sort of perpetual
motion to power something. 3. The advent of super conductors to create
magnetic fields. 4. the location in the upper Amazon where one has a lot of
water resources, high mountains and high desert is fairly close area. This
area is close to the equator of the earth, which I understand is the best
place to launch for orbit of the earth. 5. the area is lightly populated,
and the population needs a way to get into the 21st century with industry and
education. My idea is to dam the river one of its deep canyons in in the
mountains, for almost unlimited electrical power. Build a 'gun' up the side
of one of the high mountains, consisting of super conductor magnetic fields
to lift a pay load to high speed and then rocket the rest of the way into
orbit as needed. For lanking their are large high desart areas to form a
space port for landing a Delta 5 rocket or a shuttle type craft. One of the
mountains may be hollowed out for living spaces and climate controll. It
seems to me this would create a very cost effective world space port.
What-do-ya-think? Bill L.
--
As I get older and older
and totter toward the tomb,
I care less and less
Who goes to bed with wh
kabam...@earthlink.net
"Mark Harrison" <bgc...@ipa.net> wrote:
> Anyone have any info on the use of guns to launch Satellites into orbit. I
> do know that Geared Bull (?) once worked with the Canadians and the US
> (HARPS Project) towards that goal.
There is a project presently being funded for the "Jules Verne Launcher" - I
believe somewhere in Florida. I think it is a DARPA or DOD funded project.
Another option being investigated by a gentleman named Darrick Tidman of
Tidman and Associates is that of a large hoop launcher. Basically, a 1 km
diamter "hoola-hoop" tube. Every 20 meters is a rotary station that rotates
the whole hoop only ~3 meters. A projectile inside the hollow tube is then
accelerated much like a hoola-hoop.
There are some very limiting issues: 1) The speed is such that the tube has
to be maintained at vacuum or with Helium gas to avoid shock waves. 2) The
acceleration is so great (>20 g's) that no lifeforms can make it. However, it
is being "advertised" as a way to send up supplies. 3) Getting the projectile
out of the hoop is very VERY tricky. In that last leg (before reaching a
velocity of ~7 km/sec) the projectile laps the whole tube in less than a
second. The tube has to open that thing up fast. 4) The projetile has to be
levitated electromagnetically to avoid friction buildup. 5) The system has to
be built with an ejection tube that angles up correctly for launch. For
prime launch, it would have to be located close to the equator - I believe
Mexico is "proposed" so the launch takes place over the Gulf of Mexico.
The advantage of this system is that, when done, the projectile is launched
with purely electrical power. A few power stations are needed for this - but
the costs are way down (~$100 per lb for 5 launchs per month). However, the
upfront cost is GIGANTIC.
Right now, a 1 meter diameter hoop has been built and tested with a
magnetically levitated ball bearing up to about 500 m/sec.
I know there was an article on this in some magazine (Popular Science or
something). It had the cover. As a graduate student at the University of
Illinois about 5 years ago, I worked on a proposed design of such a system as
a project. I'm unsure where further information could be obtained. Perhaps
a web search on Tidman. Also, Dr. Rodney L. Burton at the University of
Illinois (an old friend of Dr. Tidman's) knows about it. Dr. Burton worked
on gun launch systems in the 1970s and 1980s, so he's an expert on the
subject.
Interesting idea, eh? Unfortunately, even if the funds were available and the
engineering effort could be done it probably would not survive the attack of
people saying its a weapon of mass destruc
Richard Kaiser
>In article <BrU62.258$iK1....@wormhole.dimensional.com>,
> rka...@dim.com (Richard Kaiser) wrote:
>>
>>
>> A gun launch is only 20% of the solution.
> Turning this ballistic trajectory into an orbit requires a delta-V
>> burn in orbit that is four times bigger than the delta-V imparted by the
>> gun.
>
> Richard Kaiser
> Maybe my head is screwed on wrong but at 100miles up, isn't gravity
>and resistence from air less? Why would a second burn be 4X bigger?
>Please keep the answer simple, I'm no rocket scientist.
> How often would a station cross a fixed spot? Could you build this
>gun site on a mountain, near the equator and have a booster,of sorts,
>straped to the back of the payload?
> Rick Keenan
First, you have to get up there. A gun may be able to do this.
Then, you have to get moving to orbital velocity or you will fall back
down.
At any point in a orbit you have PE (potential energy=m*g*h) and KE
(kinetic energy=0.5*m*v^2). In a circular orbit these are constant, otherwise
one increases while the other decreases. For an orbit without
energy losses PE + KE is a constant. PE is calculated from the orbit
altitude. (Note that the PE equation has to solved by integration as
g decreases with altitude.)
To stay in orbit the velocity needs to be g(r) = v^2/r. g(r) is the gravity
in the orbit and is from the equation g = GM / r^2. v is the velocity
required for a circular orbit. Solve these for a low earth orbit and
KE is about four time the size of PE.
If your orbit enters the atmosphere you will resemble a shooting start. If
your orbit intersects the earth you will burn up on reentry or you will know
how a bug hit by a windsheald feels.
Richard "rocket scientist in training" Kaiser
Hiram Berry
[...]
>
> First, you have to get up there. A gun may be able to do this.
A gun may be able to deliver much more than this; that's why Andrew's
answer about the survivable acceleration for electronics really got my
attention. At the 30000g limit he suggests, a gun somewhat over 100m
long could give a projectile a total energy equivalent to LEO.
> Then, you have to get moving to orbital velocity or you will fall back
> down.
>
[...]
> To stay in orbit the velocity needs to be g(r) = v^2/r. g(r) is the gravity
> in the orbit and is from the equation g = GM / r^2. v is the velocity
> required for a circular orbit. Solve these for a low earth orbit and
> KE is about four time the size of PE.
I wondered where you came up with that ratio. Of course it's only
applicable for that particular case (LEO). Maybe we're being too
restrictive in assuming that-- the natural application for gun-lauched
payloads may be deep space. A few quick calculations show why. Assume a
far hypersonic gun, aimed straight up, from say 30deg latitude, which
gives the projectile a net (with air resistance losses deducted) 8000
m/s upward.
Earth's rotation gives an eastward boost of about 400 m/s, for a net
velocity of 8010 m/s. The total energy (per mass) is:
E = v^2/2 - G*M/r = -3.044 * 10^7 J/Kg (M = mass of Earth)
and angular momentum (per mass) is
P = v(angular) * r = 2.55 * 10^9 m^2/s
With E and P, we know the shape of the orbit; that gives an apogee of
1.309*10^7 m from the center of the Earth, or an altitude of about 6711
Km, and a calculated perigee of about 8 Km, so your point about
providing delta-v to give it some angular velocity is well taken. How
much does the projectile need to be "kicked" at apogee to result in a
viable orbit? Well, to start, v(apogee) = P / r(apogee) = 195 m/s.
There are convenient formulae simply relating apogee/perigee radii to
their velocities at those points:
v[a] = sqrt( 2 * G *M * r[p] / (r[a] * (r[a] + r[p]) ) )
Suppose we want the final orbit to have a perigee of 200 Km altitude,
then use r[p] = 6.576 * 10^6 m and find that the final v[a] of the burn
must be about 4513 m/s, or a delta-v of 4318 m/s to get a viable orbit.
This is a little more than half that imparted by the gun itself,
certainly a far cry from the previously mentioned factor of four. It
is, however, a great penalty in terms of mass fraction, probably too
great to be worth doing. Suppose, though, that the muzzle velocity of
the hypersonic gun could be extended a little bit, to a net velocity of
10300 m/s. Now you have an interesting case, with the apogee at
geosynchronous range. The apogial velocity will be negligible, around
60 m/s, but the delta-v needed for a sustainable orbit is now only about
1535 m/s, a reasonable task for a solid fuel booster (to inject into GEO
is about double that).
For many purposes there's a much better place to apply the delta-v,
though-- if that 1535 m/s were added just as the craft left the
atmosphere, the added boost done while still in the gravity well of the
Earth puts it at a little more than escape velocity (or use less and
slingshot around the moon). Because most of the work has been done by
the gun, the booster can be low-thrust to minimize mass penalty, and
designed for expansion to vacuum to maximize Isp.
There is another alternative, if LEO is the goal, that Andrew Higgins
suggested via one of the references he gave. That is the possibility
that the projectile could be aerodynamically active rather than just
ballistic. If high-temperature thermally conductive ceramics enable the
use of sharp leading edges on the projectile, then active control
surfaces can let the projectile turn in the upper atmosphere,
efficiently converting most of the upward velocity into the angular
direction. Very little delta-v will be needed to set a stable orbit.
All in all I think the concept of a hypersonic gun looks very promising;
I guess the next thing that needs to be considered is the mechanics of
detonating the propellant charges to get the best acceleration profile
for the projectile, and minimizing the bursting pressure generated at
any point on the barrel.
-- Hiram Berry
Andrew Higgins
>
> A gun launch is only 20% of the solution.
>
> the earth were not rotating. In other words, the payload would return to
> burn in orbit that is four times bigger than the delta-V imparted by the
> gun.
Calculations, please.
Some gun launch concepts have muzzle velocities of 7 to 9 km/s. The
burn required to circularize the orbit once above the atmosphere can
be as small at 0.5 km/s.
Jonathan Stone
|>
|> Some gun launch concepts have muzzle velocities of 7 to 9 km/s. The
|> burn required to circularize the orbit once above the atmosphere can
|> be as small at 0.5 km/s.
That's 0.5 km/s is even after negative delta-v (E_k losses) to punch
through the sensible atmosphere? At what angle of attack? And what
kind of payload? A kinetic interceptor, okay, but a `spacecraft'?
Richard Kaiser
>
>Richard Kaiser wrote:
>>
>> A gun launch is only 20% of the solution.
>>
>> The gun would place the playload into an orbit that would include the gun if
>> the earth were not rotating. In other words, the payload would return to
>> earth. Turning this ballistic trajectory into an orbit requires a delta-V
>> burn in orbit that is four times bigger than the delta-V imparted by the
>> gun.
>
>Calculations, please.
>
>burn required to circularize the orbit once above the atmosphere can
>be as small at 0.5 km/s.
I don't have time to redo these calculations now. If you are really
interested get youself a copy of "Fundamentals of Astrodynamics"
by Bate, Mueller and White. Its ISBN0-486-60061-0 and its only
about $11. If you want to be taken serious in astro know this book.
The big problem with guns is they can never get the velocity direction
correctly. In a simplified launch, 20% of the delta V is converted to
potential energy to get into space. Once in space the remaining
delta V is required to reach orbital velocity.
The critical part of the of an orbit is the velocity vector is roughly
perpendicular to the position vector. You can't do this with a gun
as it can only apply one delta V. No, shooting the gun at an angle
doesn't help as you still are not generating a velocity vector
that is close to perpendicular to position vector.
Once free of the earths surface (even a fraction of an inch) an object
is in orbit. Using the first approximation, that orbit will allways include
the point it started from (ie the gun) if no additional energy in applied.
Unfortunately, if the atmosphere isn't bad enought, these is this
really thick stuff call earth that prevents the object from completing
its orbit if the orbit isn't high enough.
To change an orbit requires changing the velocity of the object. The
really tricky part is when you fire a rocket engine to change an orbit
its the rest of the orbit that changes, but the point where the rocket was
fired is still a point on the new orbit.
To change to an orbit that does not include the original point requires two
rocket burns (or one gun firing and one rocket burn). And I cannot picture
any rocket of significant power that can survive being fired from a gun.
Richard Kaiser
je...@computer.com
space exert a force away from the earch if you apply electricity to the
tether, and the tether moves towards the earth if you pull electricity out
of the tether. Is this only for tethers that are moving in a fast orbit?
I am wondering what the effect would be on a gun-launched object if it
unrealed a long tether as it went further into space - is there any way
that could keep it up there?
Second quetion: what if you had a system of tethers up in space, arranged
in some kind of conical shape - to create, in effect, a conical EM field -
I am making this up as I go (actually I posted about this a year ago) -
now, you shoot the gun so that the object passes into the beginning of the
conical field - is there any way that this could 'catch' the object? Or
provide some acceleration? It is magnetism just like with levitating
trains or partical accelerators - the object does not touch the tethers,
but the EM field there would grab the object. The conical system is what
is in orbit, so it 'catches' the object and pulls it along. You would
have to have a very precise shot from the gun launcher. Lasers on the
ground could provide some fine-tuning of the trajectory.
Jeff
Roger Carbol
> The critical part of the of an orbit is the velocity vector is roughly
> perpendicular to the position vector. You can't do this with a gun
> as it can only apply one delta V. No, shooting the gun at an angle
> doesn't help as you still are not generating a velocity vector
> that is close to perpendicular to position vector.
There are some companies working on artillery rounds that have
aelirons, and can be steered (to some degree) after they've
been fired.
While the projectile is in the atmosphere, I think a similar
system could be used for launching payloads. Building a system
that would survive the acceleration is challenging, but I don't
believe it's out of the reach of current technology.
.. Roger Carbol .. r...@shaw.wave.ca .. better a sword
Andrew Higgins
>
> In article <3661FE...@mecheng.mcgill.ca>, Andrew Higgins <hig...@mecheng.mcgill.ca> writes:
> |>
> |> burn required to circularize the orbit once above the atmosphere can
> |> be as small at 0.5 km/s.
>
> through the sensible atmosphere?
>
Yes, that is taking into account the velocity lost during atmospheric
transit (which is only 1-2 km/s).
>
>At what angle of attack?
>
Zero degree.
>
>And what kind of payload? A kinetic interceptor, okay, but a `spacecraft'?
>
Most gun-launch-to-orbit studies (the ones form which I'm citing
numbers)
use projectiles which are 1-2 ton. Typical packages are a 10-m long by
1-m
diameter aeroshell, housing the kick motor and payload which occupy
roughly
equal volume.
Andrew Higgins
>
> In article <3661FE...@mecheng.mcgill.ca>, hig...@mecheng.mcgill.ca wrote:
> >
> >Richard Kaiser wrote:
> >>
> >> A gun launch is only 20% of the solution.
> >>
> >> The gun would place the playload into an orbit that would include the gun if
> >> the earth were not rotating. In other words, the payload would return to
> >> earth. Turning this ballistic trajectory into an orbit requires a delta-V
> >> burn in orbit that is four times bigger than the delta-V imparted by the
> >> gun.
> >
> >Calculations, please.
> >
> >burn required to circularize the orbit once above the atmosphere can
> >be as small at 0.5 km/s.
>
> interested get youself a copy of "Fundamentals of Astrodynamics"
> by Bate, Mueller and White. Its ISBN0-486-60061-0 and its only
> about $11. If you want to be taken serious in astro know this book.
>
Yes, and with Bate, Mueller, and White, you get what you pay for.
>
> The big problem with guns is they can never get the velocity direction
> correctly. In a simplified launch, 20% of the delta V is converted to
> potential energy to get into space. Once in space the remaining
> delta V is required to reach orbital velocity.
>
This is simply incorrect. No one who has seriously studied gun launch
to
orbit using the advanced high-velocity launcher concepts available today
suggests launching straight up. While determining the optimal launch
angle is not a straightforward calculation, most design studies for gun
launch to orbit have selected a launch angle of about 20 deg. With such
a launch angle, and a muzzle velocity of 5 km/s or greater, it is
possible
to get above the atmosphere with a significant velocity component in the
correct direction (perpendicular to the position vector).
With some clever techniques, like apogee burns and aerobreaking, it is
possible to circularize the orbit with a modest expenditure of
propellant.
For example, if you gun-launch to an altitude of several thousand
kilometers, then perform a small delta V burn to raise the perigee to
50 or 70 km, you can aerobrake to lower the apogee as needed. When the
apogee is lowered to the desired orbital altitude (say, 500 km), a final
small delta V burn circularizes the orbit. The *total* delta V required
for this technique can be keep to under 500 m/s.
For the details, look at a design study produced by my old research
group
at the University of Washington, Seattle:
Kaloupis, P., Bruckner, A.P., "The Ram Accelerator: A Chemically
Driven Mass Launcher," AIAA 88-2968, AIAA/ASME/SAE/ASEE 24th Joint
Propulsion Conference, July 11-13, Boston, MA, 1988.
..available in any good engineering library
Andrew Higgins
>
> And I cannot picture
> any rocket of significant power that can survive being fired from a gun.
>
You might tell that to some of my colleagues here at McGill, who were
gun-
launching rockets to an altitude of 200 km more than 35 years ago.
Craig Berry
: Second quetion: what if you had a system of tethers up in space, arranged
: in some kind of conical shape - to create, in effect, a conical EM field -
: I am making this up as I go (actually I posted about this a year ago) -
: now, you shoot the gun so that the object passes into the beginning of the
: conical field - is there any way that this could 'catch' the object? Or
: provide some acceleration? It is magnetism just like with levitating
: trains or partical accelerators - the object does not touch the tethers,
: but the EM field there would grab the object. The conical system is what
: is in orbit, so it 'catches' the object and pulls it along. You would
: have to have a very precise shot from the gun launcher. Lasers on the
: ground could provide some fine-tuning of the trajectory.
This is one of a category of "momentum bank" proposals. Basically, upward
payloads are launched vertically from Earth, timed to hit apogee just as
the mouth of a magnetic accelerator sweeps over them. The accelerator --
effectively a railgun running in reverse -- decelerates the payloads in
its own frame, thus accelerating them in the Earth's rest frame. The much
more massive accelerator station only slows down slightly.
Meanwhile, capsules full of orbitally-manufactured goodies are accelerated
out the "back" of the railgun, killing their orbital velocity and causing
them to drop straight down, for retrieval on Earth. Kicking these out the
back boosts the station just as much as catching incoming payloads slows
it down, so the net effect on the station is zero.
Note that you can use any scheme you want to loft the payload to the
station's altitude, but doing that is much easier in delta-v terms than
achieving circular orbit at that altitude (especially for LEO). Note also
that for any reasonable station length, the payloads must be able to
survive serious acceleration -- not as much as a gun launch, but still
into hundreds of gees.
--
| Craig Berry - cbe...@cinenet.net
--*-- Home Page: http://www.cinenet.net/users/cberry/home.html
| "The hills were burning, and the wind was raging; and there
was no more room in the Garden of Allah."
Dr John Stockton
13:25:30 in news:sci.space.science, Roger Carbol <r...@shaw.wave.ca>
wrote:
>There are some companies working on artillery rounds that have
>aelirons, and can be steered (to some degree) after they've
>been fired.
>
>While the projectile is in the atmosphere, I think a similar
>system could be used for launching payloads. Building a system
>that would survive the acceleration is challenging, but I don't
>believe it's out of the reach of current technology.
We are assuming that propulsion and control equipment can be designed to
survive such a launch - launch and propel the rounds to rendezvous with
ISS or an associated collector.
With ISS up, there's a considerable quantity of payload needed that
should easily stand such a launch.
After all, Shuttle delivered to Mir a large amount of water (hard to
damage, that stuff); air (if loaded at 4K) might remain condensed until
it could be delivered to better storage; some fuels; many constituents
of food : (not eggs, but yolk & white), flour, salt; maybe minced meat,
mashed potato, ...
--
John Stockton, Surrey, UK. j...@merlyn.demon.co.uk Turnpike v4.00 MIME.
Web <URL: http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
by zrtps008
> To stay in orbit the velocity needs to be g(r) = v^2/r. g(r) is the gravity
> in the orbit and is from the equation g = GM / r^2. v is the velocity
> required for a circular orbit. Solve these for a low earth orbit and
> KE is about four time the size of PE.
>
> If your orbit enters the atmosphere you will resemble a shooting start. If
> your orbit intersects the earth you will burn up on reentry or you will know
> how a bug hit by a windsheald feels.
OK. Low earth orbit is out- how about much higher?
How about swinging round off the moon? wouldn't that be a lot closer to
an orbit?
1/2 ;-)
> Richard "rocket scientist in training" Kaiser
--
-Ian (wo...@nortel.nojunkmail.co.uk)
2 Secrets to success: 1. Don't tell everyone what you know.
Allen Thomson
[ker-snip]
>This is one of a category of "momentum bank" proposals. Basically, upward
>payloads are launched vertically from Earth, timed to hit apogee just as
>the mouth of a magnetic accelerator sweeps over them.
Wouldn't there be a guidance problem in getting the payload to just the
right place at just the right time?
Togetherin
}
The 20G forces you suggest and the time for launch are compatible with life if
cushioning is employed in the vehicle. It would depend upon the launch time.
We cushion shipments against momentary 100G's all the time.
Craig Berry
: In article <7409br$5lo$1...@marina.cinenet.net> cbe...@cinenet.net (Craig Berry) writes:
: >This is one of a category of "momentum bank" proposals. Basically, upward
: >payloads are launched vertically from Earth, timed to hit apogee just as
: >the mouth of a magnetic accelerator sweeps over them.
:
: Wouldn't there be a guidance problem in getting the payload to just the
: right place at just the right time?
Yes, there would be. But not an insurmountable one, given tiny
positioning thrusters on the incoming capsules. In fact, I would design
the system so that the free path of the capsules missed the station
entirely, requiring a small amount of active thrusting to get on the entry
path. This would stop 'dud' capsules from slamming into the edge of the
railgun entry tube (well, the reverse, really) at orbital speeds.
RBynum3965
Why not use a catapult to launch satelittes? A 1 km arm with a 1/10 sec
90degree swing will accelerate a satellite somewhere in the ballpark of 15
km/sec. Now with enough styrofoam peanuts we might be able to send people up.
Robert Bynum
RBynum3965
The future is here it is just not evenly distributed -- William Gibson
Wherever you go there you are -- Buckaroo Banzai
Andrew Higgins
rbynu...@aol.com (RBynum3965) wrote:
>
> Why not use a catapult to launch satelittes? A 1 km arm with a 1/10 sec
> 90degree swing will accelerate a satellite somewhere in the ballpark of 15
> km/sec. Now with enough styrofoam peanuts we might be able to send people up.
> Robert Bynum
>
This idea has been suggested before, notably by Robert Zubrin and David Baker:
Baker, D., Zubrin, R., "Lunar and Mars Mission Architecture
Utilizing Tether-Launched LLOX," AIAA Paper 90-2109, 26th
Joint Propulsion Conference, Orlando, FL, July 16-18, 1990.
Unfortunately, the problem is that the tension in the catapult arm exceeds
the tensile strength of the arm itself, and the arm will tear itself into
pieces. Even for the very best materials, you cannot have a tip velocity
much in excess of 1 km/s, unless you happen to have some lengths of
buckytube robe hanging around. [See detailed calculations below.]
Tapering the arm (which would more likely be a tether, rather than an
rigid catapult) can help overcome this material limit somewhat. For
example, the Baker and Zubrin design I cited above used a Kevlar tether 7
km long, which tapered from 18 cm at the base to 10 cm at the tip, which
would spin at 2-3 rpm. This is sufficient to launch a payload from the
lunar surface to low lunar orbit.
Another problem would be aerodynamic drag on the tether. Baker and Zubrin
solve this problem by basing the launcher on the moon.
The material limitation is what leads to Derek Tidman's "Slingatron" idea,
mentioned earlier in this thread. Rather than *pull* the payload in a
circular path by using tension in a sling, why not *push* the payload
along a circular track? The track makes a "Hula-Hoop" motion synchronized
with the payload as it travels around the track, always pushing inwards.
By this technique, you can by-pass the material limit of sling-type
launchers.
This is the same mechanism by which you can accelerate a marble rolling
around the bottom of a bucket to very high speed by gyrating the bucket
with a small-amplitude circular motion.
Tidman's latest versions of the "Slingatron" dispenses with
electromagnetic levitation of the vehicle and instead relies on a
gasdynamic bearing or on evaporation/ablation of the underside of the
vehicle to maintain a nearly frictionless contact between vehicle and
track:
Tidman, D., "Slingatron Mass Launchers," Journal of Propulsion
and Power, Vol. 14, No. 4, July-August 1998, pp. 537-544.
The numbers on this concept appear quite promising, but just how low the
friction between vehicle and track can be kept is probably the biggest
unknown and is very difficult to estimate.
Appendix: What is the fastest speed a sling-launcher can obtain?
=================================================================
Consider a sling-arm of length "R", cross-sectional area "A", and density
"rho". Neglect the payload mass on the end of the tether (tether mass
ends up being much greater than the payload mass in most designs anyway).
The tension created by an increment of mass on a sling in constant angular
motion is given by:
T = dm V^2 / r
Where "dm" is the incremental mass, "V" the velocity of the mass, and "r"
the radius of its circular motion. Thus, the total tension in the tether
is given by the integral over the tether length:
Ttotal = Integral[rho A (omega r)^2 dr/r, from 0 to R]
(where we've used rho*A*dr for the incremental mass dm)
where "omega" is the angular velocity (a constant) and "r" is the distance
along the tether. Integrating, we get:
Ttotal = (rho A omega^2 R^2) / 2
Since omega*R is the tip velocity (Vtip) we can substitute:
Ttotal = (rho A Vtip^2)/2
Notice we could also have gotten this answer by dispensing with the
calculus and simply treating the tether as a point of mass rho*A*R
traveling at velocity Vtip/2 about a radius of R/2.
So, now that we know the total tension on the tether, we can solve for the
tip radius as a function of tension:
Vtip = Sqrt[2 Ttotal/(A rho)]
Total tension divided by area is tensile stress. The best tether material
on the market today is Spectra 2000, with a tensile strength of 3.25 GPa
and a density of 0.97 g/cc. Putting those values into the equation, we
get:
Vtip = 2.59 km/s.
So, the maximum velocity we can obtain is 2.59 km/s. Any higher tip
velocity and the tether will tear itself to pieces. Notice that this
result is independent of the tether length or angular velocity.
An interesting possibility is using buckytube cable, with a (theoretical)
tensile strength of 150 GPa and a density of 1.3 g/cc. That would give a
tip velocity of 15 km/s!
Finally, tapering the tether can improve the situation somewhat, but this
is the basic limitation you have to deal with.