Un- conventional ways to LEO

cjchandler · 2006-09-16 17:58:32

I've seen a lot of ideas involving bigger chemical launchers, two stage chemical rockets, and single stage to orbit in this site, but those probably aren't going to get us the prices low enough for a significant number of people to colonize mars. What pet scheme do you have to drastically reduce launch costs? I'd like to hear everyone's no matter how hair brained. Hey, one of them might actually work. Here is mine to start off: A wave rider with a fabric wing that can change shape to optimize to any speed that is covered with thin film solar cells. Then at the rear it has a propeller that consists of smaller wave rider kites on Kevlar or spectra cords spinning about the hub to produce thrust, and spun by electric motors. The craft slowly climbs and accelerates so that the air density goes down to limit heating. To make up for the reduced air density the propeller/kite cords are unwound further so as to increase the propeller disk area. Feel free to criticize and please share your own ideas.

noosfractal · 2006-09-16 19:57:18

How about ...

http://en.wikipedia.org/wiki/Laser_propulsion

( although MX Tethers totally rock! Oh yes they do. Space elevator motivated research into CNT tethers just bring them closer. Muhahaha. )

unitx · 2006-09-16 20:57:18

http://www.newscientist.com/channel/fun … heels.html

noosfractal · 2006-09-16 21:44:19

http://www.newscientist.com/channel/fun … heels.html

No, please, this one is just bullshit ...

http://groups.google.com/group/sci.phys … 26b30b14f2

cjchandler · 2006-09-17 09:07:56

I like the laser propulsion ideas, except for that the laser has to be so powerful and therefore expensive. If you are goign to need that much reaserch and infrastructure for a laser facility you might as well use the MX tether system, whihc I agree sounds really good, except that I wouldn't use a airbeathing first stage, something like the a SSTO with a better payload fraction would probably be more feasible. NASA should use the ISS for something useful and use it as the counterweight on the MX transfer to LEO program. As for the relitivity drive I don't think it's worth my 4 bucks to read the article, sorry, any one who has an earth shattering break through will not need to charge people to learn about it.

noosfractal · 2006-09-23 15:30:30

I like the laser propulsion ideas, except for that the laser has to be so powerful and therefore expensive.

Why are lasers so expensive? Is it just the (probably nuclear) power supply? Is the (probably adaptive) optics? What would make them cheap? More SDI research?

GCNRevenger · 2006-09-23 17:16:45

A massive laser is difficult because of the size of the components, the power storage systems (capacitors, flywheels), and directing optics.

The problem with a laser is three fold:

First the launch vehicle still needs some kind of reaction mass thus limiting specific impulse to ~1000sec for Hydrogen, and kind of defeating the purpose. Maybe a little higher with an ablator.

The beam itself will be absorbed and scatterd by the atmosphere that will make accurate/efficient transmission difficult, you can probably hit the vehicle, but you want to heat only the collector and not the whole thing.

And finally the time that a vehicle will be overhead of the laser site will be short, which nessesitates extremely high (>10G) acceleration rates to get to orbital velocity before the vehicle goes over the horizon. This also really magnifies the power requirements of the laser to extreme levels.

Oh, and the ISS would make a terrible counterweight for a momentum exchange tether, its all the wrong shape for it and is in the wrong orbit.

noosfractal · 2006-09-23 18:24:40

A massive laser is difficult because of the size of the components, the power storage systems (capacitors, flywheels), and directing optics.

I'm assuming a launch system would have a dedicated nuclear power plant. I know the optics get harder when you get larger, but I've got to believe that experience with segmented telescopes makes it easier

First the launch vehicle still needs some kind of reaction mass thus limiting specific impulse to ~1000sec for Hydrogen, and kind of defeating the purpose. Maybe a little higher with an ablator.

One proposal I saw had a dimpled plate while in the atmosphere - which gives good thrust from heated air - then the plate is jettisoned to expose an ablative plate once you're out of the atmosphere.

The beam itself will be absorbed and scatterd by the atmosphere that will make accurate/efficient transmission difficult, you can probably hit the vehicle, but you want to heat only the collector and not the whole thing.

Again, I'm thinking that adaptive optics like the astronomers use to correct for atmospheric effects can be helpful here. It does make the system more expensive, but one costing I saw quoted +20% (and not +200% or anything).

And finally the time that a vehicle will be overhead of the laser site will be short, which nessesitates extremely high (>10G) acceleration rates to get to orbital velocity before the vehicle goes over the horizon. This also really magnifies the power requirements of the laser to extreme levels.

Yeah, cargo only, probably looking at 20 ton payloads. $/kg looks nice though. And we need most of the tech for the space elevator anyway - to power the climbers.

Oh, and the ISS would make a terrible counterweight for a momentum exchange tether, its all the wrong shape for it and is in the wrong orbit.

That's a great idea! I knew you'd come around

cjchandler · 2006-09-24 12:09:12

Ablative laser propulsion can give specific impulses up to 20000 with carbon http://pakhomov.uah.edu/Minigrant.pdf#s … sion%20%22, but really I don't know why you'd want to go that high, since there's no engine weight just a block of propellent exposed to the air, you can go lower to save on the energy requirments. I like tin, the link shows a graph of specific impulses, it's dense so you can easilly carry a really heavy block of it and the sepecific impulse allows for a more reasonable laser. What makes the laser more expensive for this is that it has to be able to do many high power femo-second pulses. I don't think even fusion laser experiments do pulses that short and quickly. On a side note Pakhomov has used the ablative laser propusion to make a demonstration rocket in the lab, but it weighed something like 2 kg and hopped only about a cm up.

noosfractal · 2006-09-24 17:27:10

Sweet graph, thanks!

GCNRevenger · 2006-09-24 22:32:30

No a nuclear reactor would be an awful choice, those are best suited to long periods of continuous, moderate output and not rapid power up/power down. It would be a terrible cost for the thing to sit there and idle between firings.

About the laser, I say that a laser of that magnetude will be hard to build period reguardless how you intend to aim it. It will be bigger than anything that has ever been done before by far.

Adaptive optics have a problem too, that the mirror that does the adapting has to be fairly small around, and if you are focusing that much energy on it even if its 99.9% reflective, that last 0.1% of such a powerful laser will be enough to wreck the mirror, or at least the delicate components that operate it. Both refrigerating and flexing the AO mirror may not be practical at all.

Using ambient air for reaction mass probably won't do either, you need enough air to cool the vehicle and keep it from melting under the beam you know, and I doubt you'll achieve thrusts high enough to be worth the trouble. Remember, you have to accelerate as soon as possible so you reach orbital velocity before going over the horizon from the laser.

Superhigh G-forces on the vehicle I think is likely a show-stopper, that it isn't practical to build something that flies repeatedly and cheaply that can withstand that sort of force, nor could delicate cargo withstand it. You have to go from sub or low supersonic up to orbital velocity in the scant minutes you are over the laser site.

I disagree that you "need most of the elevator tech," the cable is still the number one technology, everything else is comparitively simple. The lasers needed for climbers are a whole different beast, orders of magnetude smaller and no complicated and accurate tracking system, plus would be tailored for long low firings instead of short high power ones.

SpaceNut · 2006-09-25 09:49:43

No a nuclear reactor would be an awful choice, those are best suited to long periods of continuous, moderate output and not rapid power up/power down. It would be a terrible cost for the thing to sit there and idle between firings.
About the laser, I say that a laser of that magnetude will be hard to build period reguardless how you intend to aim it. It will be bigger than anything that has ever been done before by far.
Adaptive optics have a problem too, that the mirror that does the adapting has to be fairly small around, and if you are focusing that much energy on it even if its 99.9% reflective, that last 0.1% of such a powerful laser will be enough to wreck the mirror, or at least the delicate components that operate it. Both refrigerating and flexing the AO mirror may not be practical at all.

Do not focus the beam to a point but allow it to cover the entire mirror surface each mirror can have its own laser of much less power. Focus the beams at the end lense before aiming at the target ship.

Using ambient air for reaction mass probably won't do either, you need enough air to cool the vehicle and keep it from melting under the beam you know, and I doubt you'll achieve thrusts high enough to be worth the trouble. Remember, you have to accelerate as soon as possible so you reach orbital velocity before going over the horizon from the laser.
Superhigh G-forces on the vehicle I think is likely a show-stopper, that it isn't practical to build something that flies repeatedly and cheaply that can withstand that sort of force, nor could delicate cargo withstand it. You have to go from sub or low supersonic up to orbital velocity in the scant minutes you are over the laser site.

I am wondering if a tile system would withstand the temperature...

I disagree that you "need most of the elevator tech," the cable is still the number one technology, everything else is comparitively simple. The lasers needed for climbers are a whole different beast, orders of magnetude smaller and no complicated and accurate tracking system, plus would be tailored for long low firings instead of short high power ones.

Yup agreed that this is a differant animal as for what is still needed.

edit all the differance a little / makes for the quoting boxes

GCNRevenger · 2006-09-25 10:07:12

I think you might not know how AO telescopes are designed:

Take a regular reflector telescope, which has a big primary mirror and a small secondary one. Light enters the telescope, reflects off the main mirror, then the secondary, and into the eyepiece or camera.

A laser this size would use such a telescope but in reverse, bouncing the laser off the secondary to the primary and then out of the scope'.

The trouble is two fold, first of all you need a small secondary mirror to avoid obtructing too much of the primary, every bit its wider is one that blocks more of the effective radius of the telescope.

The second and big problem is that its hard to make large AO mirrors, the mirror has to be flexible and has an array of tiny servos under it to bend the mirror. Making a very large one would be extremely hard, since the mirror would have to bend and stretch more, and the servos would have a difficult time moving quickly enough to account for atmospheric effects.

C M Edwards · 2006-09-25 14:36:41

When it comes to "pet" launch technologies, my personal favorite is the Airship-To-Orbit scheme proposed by JP Aerospace.

I even scratched out a New Mars wiki article about it.

Theoretically, it could work with a wide range of engine types.

cjchandler · 2006-09-25 15:48:16

I love the idea of airship to orbit, like accelerating slowly and climbing, but I don't think it will be practical. Ion engins are not going to move a lot of air since their frontal area is low and the air density is so low and therefore must push it faster, and I'm not sure the solar panels are going to be able to provide that much power. The real big question for me though is, this air ship is going to be encountering supersonic flow most of it's flight, but though the is a pronounced wing sweep it's no where near the mach angle and a regular airfoil isn't going to work well then any way. I don't think that supersonic flows disapear at low densities, so I haven't much faith in the idea because of that aspect. Maybe a waverider shaped balloon...

C M Edwards · 2006-09-26 07:10:24

I have to repeat:

Theoretically, it could work with a wide range of engine types.

This scheme would not be limited to ion rocket propulsion.

As for the whole waverider thing, yes, I agree that hypersonic aerodynamics are an important consideration even in rarefied gases, and nothing released by JP Aerospace or their competitors indicates that they plan to use a variable wing configuration to keep the wings pulled inside the Mach angle all the way up. But keeping everything behind the leading shock is merely the optimum condition for hypersonic flight, not the only possible condition.

Also, I actually got curious enough to try to model this thing once, and I have to ask: What makes you think they aren't trying for a waverider?

PS - *GASP!* You just tried to kick my pet!

cjchandler · 2006-09-28 15:27:03

Well, because of the shock angle and lack of concave undersurfaces, I'd say that it's not supposed to be a wave rider, plus the fact that on JP's website there are pictures (in the videos) that look like traditional wave riders, suggesting that they have not come up with an amazing new way to build wave riders. The problem with the engine in my mind is that unless they can figure out a way to accelerate all the air that passes over the craft, the are going to push the little bit of air they do have very quickly, and no matter what the method used is, that is going to be energy intensive. Not to say it can't ever work, they probably have a few tricks up their sleeve. I think something similar, using thin plastic mirrors instead of solar panels would work better, (thin large mirrors are defiantly my pet favorites no matter where they're used ) if some sort of rarified gas scramjet could be designed that used concentrated light instead of fuel as a heat source.

cIclops · 2006-10-03 14:16:38

A new study funded by the USAF says a superconducting ring of magnets can launch satellities to LEO

The satellite, encased in an aerodynamic, cone-shaped shell that would protect it from the intense heat of launch, would be attached to a sled designed to respond to the forces from the superconducting magnets.
When the sled had been accelerated to its top speed of 10 kilometres per second, laser and pyrotechnic devices would be used to separate the cone from the sled. Then, the cone would skid into a side tunnel, losing some speed due to friction with the tunnel's walls.
The tunnel would direct the cone to a ramp angled at 30° to the horizon, where the cone would launch towards space at about 8 kilometres per second, or more than 23 times the speed of sound. A rocket at the back end of the cone would be used to adjust its trajectory and place it in a proper orbit.

Feasible, nutz or supernutz?

GCNRevenger · 2006-10-03 17:12:27

The G-forces and payload dimension/mass restrictions will probably doom this idea.

The USAF is desperate for some way to "cheat;" they really need to suck it up and dedicate themselevs to building Shuttle-2.0 instead, or at least a high-performance reuseable "fly back" booster.

Addendum:

This sounds like a pretty weak idea now that I have read it...

-Satelites would have to endure two thousand G for extended periods. Things like silicon solar pannels or satelite optics would have to survive this plus the thermal rigors of space.
-Max payload ~10kg? Whoop-T-doo
-Claim about it supporting manned spaceflight. Frankly, thats BS, because they would all lack last-mile guidence, and collecting 100MT of rocket fuel 0.010MT at a time is just not practical.
-"None of these challenges are trivial at all." = Really expensive. How much more would just building Shuttle-II cost?

cjchandler · 2006-10-03 19:07:27

Agreed. IMO anything that can't lift at least 2000 kg is pretty much useless. Sounds like a bad investment when you consider the cost of superconducting track and the tiny payload. My guess is that these would have to be type I superconductors because of the high magnetic fields and currents, which require very expensive cyrocoolers.

cjchandler · 2006-10-04 16:55:16

Getting back to the airship to orbit idea, I've been thinking, how can one move more air to lower the energy requirments, without adding too much to drag or frontal area. Perphaps something akin to a massive MHD thruster could be used with superconducting magnets to provide the large magnetic field and the thin air ionized to become the working fluid. The main question I have is how much electrical resistance will the ionized air have and how will many volts will it take to ionize the air in the first place over a significant distance, like 10 m, at low densities. Does any one know how such a thing could be calculated?

cIclops · 2006-10-20 05:25:35

How about this one, it's unconvential and ought to cause uncontrolled laughter:

Aerovator

cjchandler · 2006-10-20 09:05:24

Well, it might work... I don't really understand how the ribbon holds the cargo up though when it's the ribbon is horizontal, wouldn't the ribbon sag and then quickly slow down due to drag? Probably worth watching though IMO since the structural materials are close to what is comercially avaliable today.

C M Edwards · 2006-10-20 14:10:38

Watch, nothing! Get out your calculator, pencil and paper. It's time to crunch numbers.

I want to know if this thing could work.

GCNRevenger · 2006-10-20 15:42:59

If you have to crunch numbers to figure out if it will work or not, chances are it won't.

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#1 2006-09-16 17:58:32

Re: Un- conventional ways to LEO

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Re: Un- conventional ways to LEO

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Re: Un- conventional ways to LEO

#4 2006-09-16 21:44:19

Re: Un- conventional ways to LEO

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Re: Un- conventional ways to LEO

#6 2006-09-23 15:30:30

Re: Un- conventional ways to LEO

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Re: Un- conventional ways to LEO

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Re: Un- conventional ways to LEO

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Re: Un- conventional ways to LEO

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Re: Un- conventional ways to LEO

#11 2006-09-24 22:32:30

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#12 2006-09-25 09:49:43

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#14 2006-09-25 14:36:41

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#15 2006-09-25 15:48:16

Re: Un- conventional ways to LEO

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#17 2006-09-28 15:27:03

Re: Un- conventional ways to LEO

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