"Rockets not carrying fuel" and the space tower.
Robert Clark
provided by a highly pressurized fluid piped up from the ground [you
may need to use a fixed-width font such as Courier New to properly view
the diagram.]
A key aspect of the proposal as desccribed below is that the material
forming the pipeline does not have to be especially strong as for
example to support its own weight. The force for supporting each
portion of the pipeline is provided by the thrust produced by
pressurized fluid vented along the entire length of the pipeline.
Note that this also would provide a means of producing a space tower
or space elevator (to low Earth orbit). You really wouldn't need to
attach a rocket to the end of the rocket itself. You would use the
pipeline to *slowly* raise the payload to the required altitude for
LEO. Then you could use a rocket attached to the payload only to give
the payload the required tangential orbital velocity. Note that the
fuel and rocket that would need to be attached to the payload would be
significantly less since this fuel would not be used for getting it up
to altitude.
You could have this "space fountain" raised only when you wanted to
launch a payload, or you could have it permanently raised in the air.
This would work if you located the fountain next to a large permanently
flowing source of water such as a river. Then for example a ram pump,
which requires no moving parts, could be used to raise the water in the
fountain:
Contents for the pulser pump section of Gaiatech.
http://members.tripod.com/~nxt wave/gaiatech/pulser/index.htm
Designing a Hydraulic Ram Pump.
http://www.lifewater.org/resources/rws4/rws4d5.htm
Bob Clark
**********************************************************************************
Newsgroups: sci.astro, sci.physics, sci.mech.fluids, sci.engr.mech,
sci.space.policy
From: rgregorycl...@yahoo.com (Robert Clark)
Date: 20 Nov 2004 17:04:01 -0800
Local: Sat, Nov 20 2004 5:04 pm
Subject: Re: "Rockets not carrying fuel" for orbital transfer.
"George Dishman" <george.dish...@clara.co.uk> wrote in message
<news:11005508...@damia.uk.clara.net>...
> "Robert Clark" <rgregorycl...@yahoo.com> wrote in message
> news:832ea96d.04111...@posting.google.com...
> >...
> > I came up with two other ideas for reducing the weight of the fluid
> > that had to be supported by the rocket as the tube trails behind
the
> > rocket.
> > Firstly, I wanted to investigate both the possibilities of using
> > gaseous hydrogen or liquid hydrogen for the fluid carried by the
tube.
> That drops the density so you need much higher
> speeds for the same flow rate so makes everything
> more difficult.
> > However, the liquid hydrogen scenario just gave too much weight.
But
> > suppose the rocket didn't have to provide the propulsion for the
fluid
> > in the tube? This is what I envision:
> <Snip pictures>
> All you have done is use a compound engine. The
> same mass is being accelerated to the same speed
> so will need the same fuel. You are forgetting
> the engines not only lift the craft but also the
> fuel needed to lift themselves. In fact with more
> engines, you have greatly increased the mass and
> the fuel needed, and all these schemes create a
> huge drag with air friction on the tube which also
> needs more fuel.
> Instead, imagine using a nearly rigid pipe as the
> arm of a trebuchet to pump fuel only over the first
> few seconds. That might be practical though the
> risks during disconnection are significant.
> George
I'm also investigating the possibility of using a rigid structure to
reach into LEO. However, I think the efficiency of the tube method is
better than you suggest.
Let's go back to the case of launch from Earth to LEO. I'm still
considering here that you're not using engines to combust fuel but are
only conducting a high pressure fluid up the tube to provide
propulsion. So the weight of the exhaust ports is quite small, not
that of a full blown engine.
Let's estimate the the size of these exhaust ports.
^
|
|
Towards the rocket.
| |
| |<----Fluid carrying tube.
| |
| |
| |
|___ ___|
/__ | | __\
// || || \\
//| |\\
// | | \\
| |
| |
| |
| |
| |
| |
|___ ___|
/__ | | __\
// || || \\
//| |\\<---Exhaust ports directed aft.
// | | \\
| |
| |
| |
| |
| |
| |
|___ ___|
/__ | | __\
// || || \\
//| |\\
// | | \\
| |
| |
| |
Let's say you put a pair of these ports every 100 meters. Then each
pair of ports would only have to provide the thrust to support the
weight of 100 meters of the tube and fluid. Let's use liquid hydrogen
now. Its density is 71 kg/m^3. The volume of a 100 m tube, .3m wide is
Pi*(.15)^2*100 = 7.07 m^3. So the mass is 71 kg/m^3 times this or
about 502 kg, 1104 lbs.
We're still using the presumption that we can communicate, say, a
pressure like the 6400 psi pressure produced by the shuttle liquid
hydrogen turbopumps up the tube. (Whatever type of pumps we use would
be located on the ground not the rocket so can be quite large.) Now we
want two exhaust ports to support 1104 lbs., or 552 lbs. each. So 552
lbs = (pressure)*(square area of ports) = 6400 * Pi * (1/4)*(diameter
of ports)^2 . We get a diameter of .33 in or 8 millimeters. Actually
they might even be smaller than this by using convergent-divergent
type nozzles used with rockets.
Now remember the entire tubes weight is supported by these exhaust
ports so the great majority of the fluid that reaches the rocket will
be driving only the payload and rocket. For a .3m = 12in wide tube
this could be a thrust of 6400 * Pi * 6^2 = 723,824 lbs. that is
solely used to loft the payload and (engineless) rocket, and again we
can probably do better than this using the nozzles normally used on
rockets.
Note that we can get even more thrust from the exhaust ports by
making them wider or by using more than 2 at each level. This is
important since we can also solve the hypersonic drag problem. These
exhaust ports are not engines but it would be a simple (and light
weight matter) to give them directional ability. Then you could have
them automatically direct their thrust to counteract the drag caused
by each portion of the tube.
Bob Clark
**********************************************************************************
Uncle Al
>
> I copied below a proposal for space access where the propulsion is
> provided by a highly pressurized fluid piped up from the ground [you
> may need to use a fixed-width font such as Courier New to properly view
> the diagram.]
> A key aspect of the proposal as desccribed below is that the material
> forming the pipeline does not have to be especially strong as for
> example to support its own weight. The force for supporting each
> portion of the pipeline is provided by the thrust produced by
> pressurized fluid vented along the entire length of the pipeline.
What percentage of the inflow makes it to the top, git? What is the
weight of a 50-mile depth of liquid oxygen, git?
> Bob Clark
so sad.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
Don A. Gilmore
news:42487FF4...@hate.spam.net...
> Robert Clark wrote:
> >
> > I copied below a proposal for space access where the propulsion is
> > provided by a highly pressurized fluid piped up from the ground [you
> > may need to use a fixed-width font such as Courier New to properly view
> > the diagram.]
> > A key aspect of the proposal as desccribed below is that the material
> > forming the pipeline does not have to be especially strong as for
> > example to support its own weight. The force for supporting each
> > portion of the pipeline is provided by the thrust produced by
> > pressurized fluid vented along the entire length of the pipeline.
> [snip]
>
> What percentage of the inflow makes it to the top, git? What is the
> weight of a 50-mile depth of liquid oxygen, git?
Not to mention pressure.
Don
Kansas City
redneckj
"Don A. Gilmore" <eromlig...@kc.rr.com> wrote in message
news:3are8cF...@individual.net...
> Don
> Kansas City
>
>
Uncle Al
I did - that is the weight of the column/area. Gonna cost ya dear in
mgh, PV, cone fittings, and foot-thick walled piping at the bottom.
Cryogenic metal loses strength. Vacuum insulation does poorly in
(1 cm)(1 cm)(50 miles)(5280 feet/mile)(12 in/ft)(2.54 cm/in)(1.14
g/cm^3)(0.0022046 pounds/gram)(6.4516 cm^2/in^2) = 130,473 psi plus
static compression of the liquid.
high pressure environments. And you have to fill the pipe before
anything in becomes something out. Not only is it a stooopid idea, it
is a stooopid Fermi idea.
Mike Rhino
laser. In that case, the rocket would still need fuel, but it wouldn't need
anything that burns. The fuel tank would contain ammonia and nothing else.
The back of the rocket would have a concave mirror that concentrates the
laser light on one spot. Ammonia would be sent to that spot, heat up, and
be ejected as exhaust.
mme...@cars3.uchicago.edu
than saying "I'm high tech, I'm using a laser":-)
Mati Meron | "When you argue with a fool,
me...@cars.uchicago.edu | chances are he is doing just the same"
bz
news:NC12e.19$45....@news.uchicago.edu:
> In article <ky12e.60128$xX3....@twister.socal.rr.com>, "Mike Rhino"
> <octob...@alexanderpics.com> writes:
>>If you wanted to send energy to a rocket, you would be better off with a
>>laser. In that case, the rocket would still need fuel, but it wouldn't
>>need anything that burns. The fuel tank would contain ammonia and
>>nothing else. The back of the rocket would have a concave mirror that
>>concentrates the laser light on one spot. Ammonia would be sent to that
>>spot, heat up, and be ejected as exhaust.
>>
> And the advantage over "something that burns" would be? I mean other
> than saying "I'm high tech, I'm using a laser":-)
>
The energy to orbit a vehicle can be generated on earth and beamed to the
vehicle, rather than trying to carry all that energy(mass) with you.
You don't even need to carry fuel. Heated Air can act as a pulse jet.
If you want to carry a reaction mass, why not water?
http://www.space.com/businesstechnology/technology/laser_propulsion_
000705.html
Google for
"laser powered" spacecraft launch
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz...@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
Mike
"Robert Clark" <rgrego...@yahoo.com> wrote in message
news:1112043120....@f14g2000cwb.googlegroups.com...
> I copied below a proposal for space access where the propulsion is
> provided by a highly pressurized fluid piped up from the ground
>Bob Clark
>
Hello,
It seems you are presenting a proposal that appears in essence an attempt at
solving some of the dilemmas associated with the desire to achieve safe and
efficient interstellar space travel.
Have you considered the ethical dilemmas of such a proposal?
Projecting our malignant, unrefined, chaotic microcosm into something on a
galactic scale would create a condition of unfathomable horror.
For instance, say you are now allowed to go zipping around the galaxy like
something akin to star trek. The first reason of necessity why one would
find the need to branch out according to the conditions of our present
malignancy would be economic. Simply put, for our condition to strengthen
and prosper we need to find more raw materials to convert into goods and
services; this means raw materials and resources of all kinds including new
living space.
So let's say after several months of searching you find a planet with
resources available for conversion and consumption. The only ethical dilemma
is, there happens to be some life forms inhabiting your newfound planet that
are at some intermediate stage along their higher evolutionary process.
Would you find it ethical to brush these indigenous life forms aside and
start tapping the planet for resources? By doing so you would be aborting
the planets higher evolutionary processes. Think if that planet was this
planet in prehistoric times invaded and consumed along with the evolutionary
progress of the entire human race.
Rather than searching for that "needle in a haystack" in this galaxy by
attempting to increase the "velocity side" of the equation. One needs to
look at the possibility of reducing the "travel time" side of the equation.
What will better cure this planet are not more cheep resources but that
instead a massive dose of synergy.
Kirk Gordon
> "Robert Clark" <rgrego...@yahoo.com> wrote in message
> news:1112043120....@f14g2000cwb.googlegroups.com...
>
>
>>I copied below a proposal for space access where the propulsion is
>>provided by a highly pressurized fluid piped up from the ground
>
Good grief!
He's not doing any interstellar travel, Mike. In fact, if the
hydrogen pipe thingy is the best he can come up with, he won't even get
above the treetops. The big problem with spreading humans around the
galaxy isn't that we'll do terrible harm; but that we'll embarrass
ourselves when other sapient critters find out how goofy we can be.
And the main, long-term, fundamental reason for going into space
isn't to get rich. It's to stay alive. As Heinlein said: The
dinosaours are extinct because they didn't have a space program. And we
don't have one either, in any sense that'll serve our survival needs
when ANOTHER major asteroid or comet decides to pay a visit.
WE'RE the lifeforms who are likely to be "swept aside" if we're
foolish enough to think that we can live forever on one fragile little rock.
KG
Matt
on a
galactic scale would create a condition of unfathomable horror."
Well Mike, I guess the only thing you can do is to act for good in your
own life; take the first step for a better universe, and GO CHOKE
YOURSELF! We've hardly made it off the planet! We probably won't have
boots on the ground anywhere outside the solar system for hundreds of
years!
As for fuelless rockets, why didn't the mass driver ever go anywhere.
Granted anything you launch in it has to be able to withstand seriously
extreme acceleration, but we could keep some rockets for the sensitive
stuff and launch all the bulk into orbit with the mass driver. I
wouldn't even think it would be terribly expensive to build compared to
say your average space "total waste of money, should've been retired
years ago" shuttle launch.
Matt
a bit further away to avoid any nearby nova, supernova, x-ray burst,
etc. or even an especially bad solar flare from our own sun.
Mike
this solar system and no further, I guess it would be ok.
I doubt there would be few if any ethical issues.
Mike
I was talking about ethics you dumb fuck!
"Matt" <mam...@gmail.com> wrote in message
news:1112078175....@z14g2000cwz.googlegroups.com...
Morituri-|-Max
"Mike" <M....@verizon.net> wrote in message
news:rI72e.33814$mq2.12588@trnddc08...
> Oh...well then, if Mr. Clark was only wanting to explore the planets
> within
> this solar system and no further, I guess it would be ok.
> I doubt there would be few if any ethical issues.
Whew.. good thing we have your permission.. man, for a second there I
thought our future was in jeaporady.
What is ethical about ensuring mankind becomes extinct because you decide we
can't leave our planet? If there are so many beings out there we could
harm, why haven't they gotten together with us yet to work out a good plan
for how we will spread into the galaxy when we finally can?
Morituri-|-Max
> Non sequitur and flame off.
> I was talking about ethics you dumb fuck!
Hmmm, after reviewing his post below, I find it strange that someone talking
about ethics (you) resorts to the f-word right off the bat, when the poster
below didn't use any vulgar words to attack you. Is this how all your
"debates" go?
Don A. Gilmore
news:Ij82e.55397$8D....@tornado.texas.rr.com...
You kids have been watching way too much TV.
Don
Kansas City
Uncle Al
Stupid idea. Energy interception scales as the square of dimension,
rocket mass scales as the cube. Only good for corrupt demos.
Morituri-|-Max
> You kids have been watching way too much TV.
I was being sarcastic. 8 )
Henry Spencer
<mme...@cars3.uchicago.edu> wrote:
>>If you wanted to send energy to a rocket, you would be better off with a
>>The back of the rocket would have a concave mirror that concentrates the
>>laser light on one spot. Ammonia would be sent to that spot, heat up, and
>>be ejected as exhaust.
>
>And the advantage over "something that burns" would be? I mean other
>than saying "I'm high tech, I'm using a laser":-)
1. You can raise the exhaust gas to higher temperatures -- giving more
energy to be converted into exhaust kinetic energy -- if you aren't
limited by the energy content of chemical fuels.
2. You can choose exhaust gases with better gas properties -- which
convert heat more efficiently into kinetic energy -- if the gases don't
have to be combustion products. Ammonia in particular, when you get it
hot, breaks down into nitrogen and a lot of hydrogen, giving really
excellent gas properties.
Depending on design approach, the flying hardware may also be simpler.
(The laser is complicated, but it's on the ground, where mass doesn't
matter and maintenance is easy.)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert | he...@spsystems.net
Henry Spencer
bz <bz...@ch100-5.chem.lsu.edu> wrote:
>You don't even need to carry fuel. Heated Air can act as a pulse jet.
Only briefly. Practical vehicles want to do most of their accelerating
up above the atmosphere, where there's no drag or aerodynamic heating.
Whether it's worth trying to exploit air on the way up is debatable, but
certainly much of the accelerating has to be done as a rocket, if you
want manageable engineering.
>If you want to carry a reaction mass, why not water?
Water is stubbornly stable, and when you do get it hot enough to break
down into hydrogen and oxygen, it soaks up a lot of energy doing so, and
keeps trying to recombine. Ammonia breaks down much more easily, and
stays broken down.
Henry Spencer
Matt <mam...@gmail.com> wrote:
>As for fuelless rockets, why didn't the mass driver ever go anywhere.
>Granted anything you launch in it has to be able to withstand seriously
>extreme acceleration, but we could keep some rockets for the sensitive
The idea isn't ridiculous, but it's tricky to make it work well on Earth's
surface, where payloads have to punch out through the atmosphere. The
engineering is challenging, and building one would be a big expensive
project. And there is basically no money for developing new unorthodox
launch systems; there is little money even for new orthodox ones.
>wouldn't even think it would be terribly expensive to build compared to
>say your average space "total waste of money, should've been retired
>years ago" shuttle launch.
Remember, the cost of the shuttle is almost all "standing army" -- it's
mostly the cost of maintaining the facilities and operations teams. You
don't save anything much by canceling one launch. (The shuttle budget has
been higher than ever for the last two years, with the launch rate zero
because the shuttle is grounded.) To see major savings, you have to close
down the whole program, and preferably mothball the VAB and LC-39.
Henry Spencer
Uncle Al <Uncl...@hate.spam.net> wrote:
>> If you wanted to send energy to a rocket, you would be better off with a
>> laser. In that case, the rocket would still need fuel, but it wouldn't need
>
>Stupid idea. Energy interception scales as the square of dimension,
>rocket mass scales as the cube.
So? This just means that laser launchers work better with small vehicles.
But that's true anyway. The dominant cost is the cost of the laser, and
that is pretty much directly proportional to vehicle size -- you need very
roughly a megawatt of laser per kilogram of payload -- and almost totally
independent of launch rate. So laser launchers, like guns, catapults,
etc., want to launch lots of little payloads rather than a few big ones,
holding the capital investment down and keeping the expensive hardware
busy. They're conveyor belts rather than pickup trucks.
Alain Fournier
Henry Spencer wrote:
> In article <NC12e.19$45....@news.uchicago.edu>,
> <mme...@cars3.uchicago.edu> wrote:
>
>>>If you wanted to send energy to a rocket, you would be better off with a
>>>laser. ... The fuel tank would contain ammonia and nothing else.
>>>The back of the rocket would have a concave mirror that concentrates the
>>>laser light on one spot. Ammonia would be sent to that spot, heat up, and
>>>be ejected as exhaust.
>>
>>And the advantage over "something that burns" would be? I mean other
>>than saying "I'm high tech, I'm using a laser":-)
>
>
> 1. You can raise the exhaust gas to higher temperatures -- giving more
> energy to be converted into exhaust kinetic energy -- if you aren't
> limited by the energy content of chemical fuels.
Avoiding engine meltdown is already a problem with chemical fuel
rockets. Does this mean that laser rockets would have to have
either exhaust temperatures similar to chemical rockets, or
have very low thrust à la ion engine rockets?
Alain Fournier
vonroach
wrote:
>>>If you wanted to send energy to a rocket, you would be better off with a
>>>laser.
No, a well designed solar panel.
mme...@cars3.uchicago.edu
>In article <NC12e.19$45....@news.uchicago.edu>,
> <mme...@cars3.uchicago.edu> wrote:
>>>If you wanted to send energy to a rocket, you would be better off with a
>>>laser. ... The fuel tank would contain ammonia and nothing else.
>>>The back of the rocket would have a concave mirror that concentrates the
>>>laser light on one spot. Ammonia would be sent to that spot, heat up, and
>>>be ejected as exhaust.
>>
>>And the advantage over "something that burns" would be? I mean other
>>than saying "I'm high tech, I'm using a laser":-)
>
>1. You can raise the exhaust gas to higher temperatures -- giving more
>energy to be converted into exhaust kinetic energy -- if you aren't
>limited by the energy content of chemical fuels.
You can raise the exhaust gas to higher temperature if you can deliver
more energy than this present in fuel carried on board. I posted
elsewhere the numbers required. As of now, you're short by many
orders of magnitude.
>
>2. You can choose exhaust gases with better gas properties -- which
>convert heat more efficiently into kinetic energy -- if the gases don't
>have to be combustion products. Ammonia in particular, when you get it
>hot, breaks down into nitrogen and a lot of hydrogen, giving really
>excellent gas properties.
>
>Depending on design approach, the flying hardware may also be simpler.
>(The laser is complicated, but it's on the ground, where mass doesn't
>matter and maintenance is easy.)
This is all lovely, once you've operational multi GW lasers, and the
means to power them, and the means to dissipate the waste heat
generated. Way to go.
Mike Rhino
> Ditto, but while Mars would save us from an asteroid, we'll have to be
> a bit further away to avoid any nearby nova, supernova, x-ray burst,
> etc. or even an especially bad solar flare from our own sun.
Would hiding inside an asteroid protect you from those?
Diginomics
> can't leave our planet?
Precisely. It is illogical from the historical point of view to enter
into the atomic age with the belief that the speed of light is a true
law, if you wish to be around for long as a living planet. The
argument must then hinge on whether because of wartime secrecy, did we
enter the atomic age off-balance? Is not the counter-balance to the
MAD doctrine, this contrived and deliberately slanted "theoretical
relativity" against all that is interstellar? After-all in the MAD
political climate, a way-out to the stars would undermine such a
doctrine if one side's leaders could take refuge in the stars while
each side fought it out to the end. Also the MAD doctrine required all
atomic materials to be dedicated to the production of deterrent, and
not reserved for space propulsion experiments. The NASA comment on
Dyson's history of Project Orion even acknowledges such uses would now
be quite convenient for using up the now no longer required atomic
assemblies. Even more I would say, for if reaching the stars were a
rampant success, the H assemblies would be dismantled to release the A
assemblies as much needed propulsion propellants. Then we could get to
the sensible stage in atomics where the very assembly of an H would be
an act of war-like aggression. Still wouldn't stop an errant space
pilot captain dropping a propulsion pellet on top of an unfriendly
city, but mankind would have progressed beyond the very dangerous
"all-or-nothing" mentality towards world peace we still are locked
into. Orion of course needs revised. Ground launches are unacceptable
and belong to the project period when standard chemical based payload
launches were in their infancy. Pusher-plates even if they were not a
technical fantasy, are also unacceptable outside of the project period
where billion dollar satellite systems were non-existent and hence not
a prohibitive cost to absorb in collateral damages. America perhaps
need to have a long look at what happened to the Chinese empire
hundreds of years ago when it failed to champion containment of
gunpowder. Coca-cola need not really provide technical insight for
such project innovations, when 1,100 years of human history have been
about containing explosions within a hollow cylinder closed at one end
with a pusher-plate. Known by the "non-techs" as the cannon or firing
tube! It does not need re-inventing this wheel! No sir! As for
relativity. If we had had the luck to enter the atomic age in a period
of peace with less fear and secrecy, perhaps relativity would have a
different more positive slant. If you wish to slant F=MA to advocate
interstellar travel, think to make "Acceleration" relative to
planetary gravities. That is to say it is not good enough to say there
is no light speed barrier (or that the barrier is found at C squared
or C to the power of another C). Rather that "relatively" acceleration
diminishes as an effect on the human body at C+ speeds when outside
the real "pull acceleration" of natural planetary gravities. Our
observation that 1 G acceleration in a rocket leaving earth is felt as
2G on the body, should not be automatically assumed to be the same as
2G acceleration in a gravity-less space environment. String theory
might help, but basically slanting relativity away from the concerns
of MAD is to say artificial accelerations are relative to planetary.
Anyone care to come up with a top G "lovingly endured" reaching a 20
light year distant planet, travelling at a maxium speed of 10C. That
is to say accelerating at a constant until reaching a peak speed
half-way of 10C and then de-accelerating the remainder to arrive
static.
If you wish for a further look at my proposed Orion revision, seek out
the ACCTOPE design on www.tide2000.com/feedback
"Morituri-|-Max" <new...@sendarico.net> wrote in message news:<Ij82e.55397$8D....@tornado.texas.rr.com>...
Matt
You were discussing ethics in a physics forum, which would be quite
understandable if the ethics you were discussing will have something to
do with decisions being made by scientists in the next hundred years or
so. If you believe this is the case with respect to your point then I
would dare say you're not very bright. If you didn't believe that your
point was relevant, then you should expect ridicule when you knowingly
post in an inappropriate forum.
If the point you were making is that we should abandon scientific
funding of space research in favor of increased funding on social
spending, or generic international cooperation, then I would say that I
disagree with you (and this should be discussed in a political forum).
If you are an agitator, as I assumed, then I do not apologize for
insulting you.
If you are just not very bright, then I'm very sorry and I wish you all
the best in your studies.
dlzc1 D:cox T:net@nospam.com N:dlzc D:aol T:com (dlzc)
"Mike Rhino" <octob...@alexanderpics.com> wrote in message
news:cap2e.694$e06...@twister.socal.rr.com...
Who wants to live as a mole? How many generations will you hide?
David A. Smith
Earl Colby Pottinger
No, depending on the design a laser heated engine can have temperature well
above that of chemical rockets because there is no combustion.
In a chemical rocket the entire volume of the combustion chamber is pretty
much all the same temperature - hot combustion gasses touch the walls of the
rocket engine and cooling the walls like you say can be a problem if there is
any mistakes in the design.
In a laser heated rocket the flux of the laser while high can be still low
enough to handle and then is focused to heat the gasses away from the
material walls of the rocket. The relative cooler gasses near the walls can
still be within material/design limits.
Another possible design would be to heat the entire rocket engine but use as
your reaction gas a very light weight fuel (example hydrogen, helium
ammonia). Normally you would need to burn an oxidzer with a fuel resulting
with a heavier molecular weight in your exhaust at a given temperature -
ofcourse you can burn helium.
So let's say as an example 3000 degree K is a hard limit in hot we can run a
rocket engine.
From the kinetic energy formula we find: v_{rms}^2 = 24,940 T / molecular
mass with v in m/s and T in kelvins.
For standard temperature 0C or 273K the root mean square speeds are:
* hydrogen 1846 m/s
* nitrogen 493 m/s
* oxygen 461 m/s
At 3000K I get
* hydrogen 6116 m/s which is a good exhaust speed above that of most
chemical rocket designs.
Earl colby Pottinger
PS. I thought STP was at 25C but www.answers.com uses 0C as STP.
--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp
Henry Spencer
<mme...@cars3.uchicago.edu> wrote:
>You can raise the exhaust gas to higher temperature if you can deliver
>more energy than this present in fuel carried on board. I posted
>elsewhere the numbers required. As of now, you're short by many
>orders of magnitude.
A more precise reference than "elsewhere" would be of interest, since
this doesn't agree with the numbers I've seen.
>>Depending on design approach, the flying hardware may also be simpler.
>>(The laser is complicated, but it's on the ground, where mass doesn't
>>matter and maintenance is easy.)
>
>This is all lovely, once you've operational multi GW lasers...
There is no requirement for them. You are, to borrow one of Bob Zubrin's
better phrases, "fantasizing about interplanetary battle cruisers". The
requirement is roughly a megawatt per kilogram of payload. You can get a
stream of payloads of practical size with 50-100MW, which would be costly
but shouldn't pose major development challenges.
A laser-launcher system which can carry *people* probably does need
GW-range lasers. But people, and other payloads which can't be subdivided
into small pieces, are a very small fraction of what we need to launch.
Henry Spencer
Alain Fournier <alai...@sympatico.ca> wrote:
>> 1. You can raise the exhaust gas to higher temperatures -- giving more
>> energy to be converted into exhaust kinetic energy -- if you aren't
>> limited by the energy content of chemical fuels.
>
>Avoiding engine meltdown is already a problem with chemical fuel
>rockets. Does this mean that laser rockets would have to have
>either exhaust temperatures similar to chemical rockets, or
>have very low thrust à la ion engine rockets?
Or designs quite different from those of chemical rockets. In one quite
appealing concept (alas, making it work well is challenging), the propellant
is just a slab of some convenient plastic. A small laser pulse vaporizes
a surface layer, and a much larger laser pulse following hot on the small
one's heels superheats the sheet of vapor. Because the expanding vapor
starts as a thin sheet on the solid surface, it inherently expands at
right angles to the surface, and no nozzle is required. Repeat briskly.
Setting aside that sort of innovation, more conventional near-term laser
rockets would probably rely mostly on better gas properties, and would not
try to get the gas a *lot* hotter. So they could be fuel-cooled in much
the same way as chemical rockets; ammonia and liquid hydrogen -- the two
obvious choices of propellant -- are both excellent coolants.
mme...@cars3.uchicago.edu
>In article <ZUk2e.7556$w63.6...@news20.bellglobal.com>,
>Alain Fournier <alai...@sympatico.ca> wrote:
>>> 1. You can raise the exhaust gas to higher temperatures -- giving more
>>> energy to be converted into exhaust kinetic energy -- if you aren't
>>> limited by the energy content of chemical fuels.
>>
>>Avoiding engine meltdown is already a problem with chemical fuel
>>rockets. Does this mean that laser rockets would have to have
>>either exhaust temperatures similar to chemical rockets, or
>>have very low thrust à la ion engine rockets?
>
>Or designs quite different from those of chemical rockets. In one quite
>appealing concept (alas, making it work well is challenging), the propellant
>is just a slab of some convenient plastic. A small laser pulse vaporizes
>a surface layer, and a much larger laser pulse following hot on the small
>one's heels superheats the sheet of vapor. Because the expanding vapor
>starts as a thin sheet on the solid surface, it inherently expands at
>right angles to the surface, and no nozzle is required. Repeat briskly.
>
direction but to cool them, as well. Basically, when you look at the
hot cloud of gas propagating down the combustion chamber, its energy
is a sum, E = E_cm + E_th, where E_cm is the energy of the center of
mass motion and E_th is the thermal energy. The first of the two
contributes to the thrust, the second doesn't. The purpose of a good
nozzle is transfer as much energy as possible from E_th + E_cm (thus,
effectively, cooling the exhaust). Without this big part of the
theoretically achievable thrust is wasted.
mme...@cars3.uchicago.edu
>In article <xUm2e.40$45....@news.uchicago.edu>,
> <mme...@cars3.uchicago.edu> wrote:
>>You can raise the exhaust gas to higher temperature if you can deliver
>>more energy than this present in fuel carried on board. I posted
>>elsewhere the numbers required. As of now, you're short by many
>>orders of magnitude.
>
>A more precise reference than "elsewhere" would be of interest, since
>this doesn't agree with the numbers I've seen.
Did you try to calculate numbers, not just "see" them?
>
>>>Depending on design approach, the flying hardware may also be simpler.
>>>(The laser is complicated, but it's on the ground, where mass doesn't
>>>matter and maintenance is easy.)
>>
>>This is all lovely, once you've operational multi GW lasers...
>
>There is no requirement for them. You are, to borrow one of Bob Zubrin's
>better phrases, "fantasizing about interplanetary battle cruisers".
No, just one of the smaller rockets used to launch satellites
nowadays. Check out the power output of these rocket engines.
> The requirement is roughly a megawatt per kilogram of payload.
Quite optimistic:-)
> You can get a
>stream of payloads of practical size with 50-100MW, which would be costly
>but shouldn't pose major development challenges.
>
Unless you plan for maneuvering and assembly in orbit, most payloads
are quite larger than this.
bz
news:oKGdnWBjp4n...@look.ca:
> For standard temperature 0C or 273K the root mean square speeds are:
> * hydrogen 1846 m/s
> * nitrogen 493 m/s
> * oxygen 461 m/s
>
> At 3000K I get
> * hydrogen 6116 m/s which is a good exhaust speed above that of most
> chemical rocket designs.
Nitrogen might be a good 'non poluting' reaction mass.
>
> Earl colby Pottinger
>
> PS. I thought STP was at 25C but www.answers.com uses 0C as STP.
Different groups use different STPs.
>
--
bz
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.
bz...@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
jmfb...@aol.com
Have you ever tried to hit the broad side of a moving barn?
With your implementation what happens when you miss?
/BAH
Subtract a hundred and four for e-mail.
Earl Colby Pottinger
> This is all lovely, once you've operational multi GW lasers,
Yes, that is a problem.
> and the means to power them,
??? There are this things called power plants, and they do put out power in
the gigawatt range already. Ofcourse there are other energy storage system
like batteries and capicitors with a nice external power source called the
national grid. I don't see the problem if you have the type of money already
needed to build the lasers.
> and the means to dissipate the waste heat generated.
There are these things called bodies of water. If you don't have one they
are easy to make, getting rid of the heat is standard engineering too.
To me the only valid objection were the lasers. You just can't order ones
that large right now. But there is nothing to say that they can't be made if
enough research money is spent first.
Earl Colby Pottinger
Quantum Mirror
resources available for conversion and consumption. The only ethical
dilemma
is, there happens to be some life forms inhabiting your newfound planet
that
are at some intermediate stage along their higher evolutionary process]
You live in a fantasy world. The ability to travel space is a problem
of immense proportion. It will be 50 to 100 years to even reach mars.
That is in our own back yard. The nearest star is a problem that will
never be achieved in these fragile bodies. We will need to become
mechanical for that trip to ever take place! We are talking centuries
before such an attempt will even be made. I am sure our malignant,
unrefined, chaotic microcosm will have evolved by then.
Mike
"Quantum Mirror" <jun...@pgrb.com> wrote in message
news:1112204010.5...@g14g2000cwa.googlegroups.com...
>
> You live in a fantasy world. The ability to travel space is a problem
> of immense proportion. It will be 50 to 100 years to even reach mars.
> That is in our own back yard. The nearest star is a problem that will
> never be achieved in these fragile bodies. We will need to become
> mechanical for that trip to ever take place! We are talking centuries
> before such an attempt will even be made. I am sure our malignant,
> unrefined, chaotic microcosm will have evolved by then.
I agree with you, and so does everyone else that the ability to travel in
space is a problem of immense proportion. Let alone the desire for
interstellar space travel. Many people including myself have important ideas
and proposals on improving the situation.
Some of these proposals involve huge expenditures and engineering
breakthroughs.
See August 2003 edition of Discovery magazine. Robert Frisbee is the chief
engineer who directs the advanced propulsion concept studies at JPL.
Still all is not lost! There are alternatives to this dilemma. Let's take a
look at the amoeba.
Now this one celled organism has no brain to speak of; it can't think, it
has no dexterity, and no accumulated technology. Though when it finds itself
in a hopeless situation such as a slightly too acidic or alkaline
environment what does it do? It migrates! It attempts to move itself to more
suitable environment.
Rather than attempting to increase the velocity of the spaceship. There
might be a better result by changing the environment the spaceship is
travelling in. Hence the concept of "planetary migration"
I am not an anarchist; this plan does not violate Einstein's laws.
Theoretically a spaceship travelling at 7 miles per second can appear to be
travelling many more times the speed of light. If the spaceship is
travelling in an environment where travel time has been compressed. Those
conditions do not exist in this universe. Therefore it becomes necessary to
migrate.
Is anyone else on the same page as me with this concept? Perhaps a very
bright (but unknown) cosmologist located
in some obscure part of England? Or Australia? Ireland or Italy? Germany?
Japan?...... Canada?
bz
> Have you ever tried to hit the broad side of a moving barn?
> With your implementation what happens when you miss?
>
when you are at the train station and you are shooting at the back of a
departing train it makes it a bit easier to hit.
It is NOT like trying to intercept an incoming missle to knock it out with a
laser.
And 'if you miss' the thrust drops until you get back on target.
You keep adjusting your active adaptive focus mirror array and tracking the
rocket, so misses are not as likely as a poorly focused pulse.
Mike
"Morituri-|-Max" <new...@sendarico.net> wrote in message
news:Ij82e.55397$8D....@tornado.texas.rr.com...
>
> harm, why haven't they gotten together with us yet to work out a good plan
> for how we will spread into the galaxy when we finally can?
.Probably because they're having the same difficulties we're having getting
from point A to point B
an excessive ammount of travel time is required.
Russell Wallace
> Stupid idea. Energy interception scales as the square of dimension,
> rocket mass scales as the cube. Only good for corrupt demos.
I'd have thought the cube-square law applied to all engines? Don't the
flow rate of rocket engines, the strength of their mountings etc all
scale as the square of dimensions, or am I missing something?
(Not that I can see the point of paying for gigawatts of lasers just to
use ammonia instead of kerosene+lox combustion products as reaction
mass, nor a market for 50-kg payloads, but I wouldn't have thought
energy interception was a problem.)
--
"Always look on the bright side of life."
To reply by email, replace no.spam with my last name.
Robert Clark
are doable with currently available tech.
You could for example use shuttle or Saturn V type engines on the
ground and direct the exhaust through the tubes upwards. These engines
have exhaust velocities in the range of 4000m/s. A particle sent upward
at this initial speed (ignoring atmosphere) could reach 800 km. At 100
km it would have a speed above 3700m/s, though the tube of course
induces frictional effects which will reduce this speed somewhat. To
resist the high temperatures you could coat the inside of the tube with
high temperature alloys such as:
tantalum hafnium carbide.
"The alloy tantalum hafnium carbide (Ta4HfC5), with a melting point of
4,215 C (7,619 F), is one of the most refractory substances known."
http://www.britannica.com/nobel/micro/254_6.html
You could instead have plasma engines provide the high velocity fluid
on the ground. Plasma engines can have exhaust velocities at hundreds
of thousands of meters per second:
Plasma Rockets
"High exhaust velocity can be achieved by the use of a plasma, where
the atoms of the gas have been stripped of some of their electrons,
making it a soup of charged particles. The temperature of a plasma
starts at about 11,000° C. But present day laboratory plasmas can be a
thousand times hotter. Particles in such plasmas move at velocities of
300,000 m/sec. These temperatures are comparable to those in the
interior of our Sun. No known material could survive direct contact
with such a plasma. Fortunately, a plasma responds well to the presence
of electric and magnetic fields. A magnetic channel can be constructed
to both heat and guide a plasma, without ever touching material walls."
http://t2spflnasa.r3h.net/shuttle/support/researching/aspl/propulsion.html
Since the plasma is sent through a tube you could have the electrical
power sent up with the tube to create the E/M fields required to keep
the plasma away from the sides of the tube. Since the engines and
electrical generating power will be on the ground you could create
quite large plasmas and E/M fields.
You could even use nuclear engines since they will stay on the ground
as long as you use the type that does not radiate the fuel.
You could send up just hydrogen gas or liquid and ignite it on exiting
the vents.
Or you could use the idea of just the fluid pressure alone providing
the propulsive force.
Bob Clark
Robert Clark wrote:
> I copied below a proposal for space access where the propulsion is
> provided by a highly pressurized fluid piped up from the ground [you
> may need to use a fixed-width font such as Courier New to properly
view
> the diagram.]
> A key aspect of the proposal as desccribed below is that the
material
> forming the pipeline does not have to be especially strong as for
> example to support its own weight. The force for supporting each
> portion of the pipeline is provided by the thrust produced by
> pressurized fluid vented along the entire length of the pipeline.
> Note that this also would provide a means of producing a space tower
> or space elevator (to low Earth orbit). You really wouldn't need to
> attach a rocket to the end of the rocket itself. You would use the
> pipeline to *slowly* raise the payload to the required altitude for
> LEO. Then you could use a rocket attached to the payload only to give
> the payload the required tangential orbital velocity. Note that the
> fuel and rocket that would need to be attached to the payload would
be
> significantly less since this fuel would not be used for getting it
up
> to altitude.
> You could have this "space fountain" raised only when you wanted to
> launch a payload, or you could have it permanently raised in the air.
> This would work if you located the fountain next to a large
permanently
> flowing source of water such as a river. Then for example a ram pump,
> which requires no moving parts, could be used to raise the water in
the
> fountain:
>
> Contents for the pulser pump section of Gaiatech.
> http://members.tripod.com/~nxt wave/gaiatech/pulser/index.htm
>
> Designing a Hydraulic Ram Pump.
> http://www.lifewater.org/resources/rws4/rws4d5.htm
>
>
> Bob Clark
>
>
>
**********************************************************************************
> Newsgroups: sci.astro, sci.physics, sci.mech.fluids, sci.engr.mech,
> sci.space.policy
> From: rgregorycl...@yahoo.com (Robert Clark)
> Date: 20 Nov 2004 17:04:01 -0800
> Local: Sat, Nov 20 2004 5:04 pm
> Subject: Re: "Rockets not carrying fuel" for orbital transfer.
>
>
>
> "George Dishman" <george.dish...@clara.co.uk> wrote in message
> <news:11005508...@damia.uk.clara.net>...
> > "Robert Clark" <rgregorycl...@yahoo.com> wrote in message
> > news:832ea96d.04111...@posting.google.com...
> > >...
>
>
> > > I came up with two other ideas for reducing the weight of the
fluid
>
> > > that had to be supported by the rocket as the tube trails behind
> the
> > > rocket.
> > > Firstly, I wanted to investigate both the possibilities of using
> > > gaseous hydrogen or liquid hydrogen for the fluid carried by the
> tube.
>
>
> > That drops the density so you need much higher
> > speeds for the same flow rate so makes everything
> > more difficult.
>
>
> > > However, the liquid hydrogen scenario just gave too much weight.
> But
> > > suppose the rocket didn't have to provide the propulsion for the
> fluid
> > > in the tube? This is what I envision:
>
>
> > <Snip pictures>
>
>
> > All you have done is use a compound engine. The
> > same mass is being accelerated to the same speed
> > so will need the same fuel. You are forgetting
> > the engines not only lift the craft but also the
> > fuel needed to lift themselves. In fact with more
> > engines, you have greatly increased the mass and
> > the fuel needed, and all these schemes create a
> > huge drag with air friction on the tube which also
> > needs more fuel.
>
>
> > Instead, imagine using a nearly rigid pipe as the
> > arm of a trebuchet to pump fuel only over the first
> > few seconds. That might be practical though the
> > risks during disconnection are significant.
>
>
> > George
>
> I'm also investigating the possibility of using a rigid structure to
> reach into LEO. However, I think the efficiency of the tube method is
> better than you suggest.
> Let's go back to the case of launch from Earth to LEO. I'm still
> considering here that you're not using engines to combust fuel but
are
> only conducting a high pressure fluid up the tube to provide
> propulsion. So the weight of the exhaust ports is quite small, not
> that of a full blown engine.
> Let's estimate the the size of these exhaust ports.
>
>
> ^
> |
> |
> Towards the rocket.
>
>
> | |
> | |<----Fluid carrying tube.
> | |
> | |
> | |
> |___ ___|
> /__ | | __\
> // || || \\
> //| |\\
> // | | \\
> | |
> | |
> | |
> | |
> | |
> | |
> |___ ___|
> /__ | | __\
> // || || \\
> //| |\\<---Exhaust ports directed aft.
> // | | \\
> | |
> | |
> | |
> | |
> | |
> | |
> |___ ___|
> /__ | | __\
> // || || \\
> //| |\\
> // | | \\
> | |
> | |
> | |
>
>
> Let's say you put a pair of these ports every 100 meters. Then each
> pair of ports would only have to provide the thrust to support the
> weight of 100 meters of the tube and fluid. Let's use liquid hydrogen
> now. Its density is 71 kg/m^3. The volume of a 100 m tube, .3m wide
is
> Pi*(.15)^2*100 = 7.07 m^3. So the mass is 71 kg/m^3 times this or
> about 502 kg, 1104 lbs.
> We're still using the presumption that we can communicate, say, a
> pressure like the 6400 psi pressure produced by the shuttle liquid
> hydrogen turbopumps up the tube. (Whatever type of pumps we use would
> be located on the ground not the rocket so can be quite large.) Now
we
> want two exhaust ports to support 1104 lbs., or 552 lbs. each. So 552
> lbs = (pressure)*(square area of ports) = 6400 * Pi * (1/4)*(diameter
> of ports)^2 . We get a diameter of .33 in or 8 millimeters. Actually
> they might even be smaller than this by using convergent-divergent
> type nozzles used with rockets.
> Now remember the entire tubes weight is supported by these exhaust
> ports so the great majority of the fluid that reaches the rocket will
> be driving only the payload and rocket. For a .3m = 12in wide tube
> this could be a thrust of 6400 * Pi * 6^2 = 723,824 lbs. that is
> solely used to loft the payload and (engineless) rocket, and again we
> can probably do better than this using the nozzles normally used on
> rockets.
> Note that we can get even more thrust from the exhaust ports by
> making them wider or by using more than 2 at each level. This is
> important since we can also solve the hypersonic drag problem. These
> exhaust ports are not engines but it would be a simple (and light
> weight matter) to give them directional ability. Then you could have
> them automatically direct their thrust to counteract the drag caused
> by each portion of the tube.
>
>
> Bob Clark
>
**********************************************************************************
Don A. Gilmore
news:1112250636....@o13g2000cwo.googlegroups.com...
It's remarkable the number of ways this can be implemented, and all
are doable with currently available tech.
You could for example use shuttle or Saturn V type engines on the
ground and direct the exhaust through the tubes upwards. These engines
have exhaust velocities in the range of 4000m/s. A particle sent upward
at this initial speed (ignoring atmosphere) could reach 800 km.
At 100 km it would have a speed above 3700m/s, though the tube of course
induces frictional effects which will reduce this speed somewhat.
--
Whoa! You're going to have to show your math on that one.
Don
Kansas City
Ian Stirling
> Earl Colby Pottinger <ear...@idirect.com> wrote in
> news:oKGdnWBjp4n...@look.ca:
>
>> For standard temperature 0C or 273K the root mean square speeds are:
>> * hydrogen 1846 m/s
>> * nitrogen 493 m/s
>> * oxygen 461 m/s
>>
>> At 3000K I get
>> * hydrogen 6116 m/s which is a good exhaust speed above that of most
>> chemical rocket designs.
>
> Nitrogen might be a good 'non poluting' reaction mass.
Not really.
Lousy atomic mass, diatomic, so you waste energy splitting it, and you
get nitrogen oxides when it hits the atmosphere at Km/s.