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Gigantic Air Gun To Blast Cargo Into Orbit
Hugh Pickens writes: "The New Scientist reports that with a hat tip to Jules Verne's From the Earth to the Moon , physicist John Hunter has outlined the design of a gigantic gun that could slash the cost of putting cargo into orbit. At the Space Investment Summit in Boston last week, Hunter described the design for a 1.1-kilometer-long gun that he says could launch 450-kilogram payloads at 6 kilometers per second. A small rocket engine would then boost the projectile into low-Earth orbit. The gun would cost $500 million to build, says Hunter, but individual launch costs would be lower than current methods. 'We think it's at least a factor of 10 cheaper than anything else,' Hunter says. The gun is based on the SHARP (Super High Altitude Research Project) light gas gun Hunter helped to build in the 1990s while at the Lawrence Livermore National Laboratory (LLNL) in California. With a barrel 47 meters long, it used compressed hydrogen gas to fire projectiles weighing a few kilograms at speeds of up to 3 kilometers per second."
If you RTA (yes I know, not likely), you'll see that they acknowledge this issue, their intent is to use this for robust cargo only (rocket fuel is given as an example, not e.g. satellites or humans)
Send up consumables, for sure. Fuel, water, compressed air, freeze-dried food, etc. Even if just used for that, this is not a bad plan. There's no rule that says you have to use only ONE method to get stuff off-planet.
what's the difference between a catapult and a trebuchet? if you exerted all the energy required to carry an object to orbit all at once ala a cannon wouldn't you just destroy the object?
The one I read about in the seventies had optics in it but there were no specifics about what it homed in on. Later I heard about one that homed on a laser target designator but I don't know if it was the same device. I would expect them to be using GPS now.
What is interesting is that the electronics were not potted. They simply used thick boards supported all the way around the edge and made sure all the parts were installed in contact with the board (i.e., not standing up on their leads). This was the seventies so the parts were DIPs, discrete transistors, quarter watt resistors, etc. Modern surface mount parts should be more robust yet.
I see no major problem shipping most stuff that the station needs via this gun. Some equipment might need to be more robust than usual, but so what? The reason for making such things as light as possible is to save on launch costs. If this thing is 1/10 the cost of conventional rockets you can double the weight of your experiment to make it tough enough to survive the gun and still come out way ahead.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
You work with what you have.
Why don't you just say what you really mean: "Waaahhh! Our laws of physics SUCK! I don't believe in them."
Actually, I'm probably confusing you with another poster who spams about his free-energy fantasies. If you're just talking about beanstalks and solar sails, well, maybe, but I think "fuel" and "reaction mass" are going to be the central part of our intra-system arsenal for quite a long time.
I've got one question. How much air are we moving to launch something?
My suspicion is something in the range or Cubic Kilometers per Second instead of CFM and if we're talking that much, what impact on our weather is there going to be with such a large fan running all the time?
What I'd suggest instead is use the tube and combine it with maglev. Allows much better control of the thrust (more accurate) and might remove the solid rocket booster stage for orbit. You also get income from the reactors excess power (when its not charging caps or launching something) and it helps reduce greenhouse gases.
Mod me up/Mod me down: I wont frown as I've no crown
1. In round numbers:
. ~9.5 km/sec to LEO (given, approximate)
. ~6.0 km/sec from gas gun (FTA)
. ~0.5 km/sec atmospheric drag (FTA)
= ~4.0 km/sec needed from projectile rocket
. 350s ISP for projectile rocket (assumed, optimistic)
= 0.69 propellant fraction
. 450Kg projectile (FTA)
= 310Kg projectile rocket propellant
= 140Kg projectile non-propellant
. ???Kg projectile structure, motor, etc.
= ???Kg net cargo to LEO (in any case, 140Kg)
2. Assuming you want to rondezvous with something in an established orbit (e.g., the ISS), any significant orbital maneuvering is out of the question; in paticular an orbital plane change--whether by the projectile or the target--as it's too expensive.
That limits the number of launch windows. You can't simply launch projectiles into orbit as fast as the gun can fire, otherwise you'll end up with them scattered in various orbits that you have to chase down (again, very expensive).
E.g., there are nominally 2 launch windows/day for Shuttle flights from KSC to the ISS. (Due to various rules, in practice it's limited to 1/day, but we'll ignore that.)
3. Even with optimal launch parameters, orbital rondezvous is still non-trivial, and one reason why even unmanned ISS resuplly vehicles are much more than simply a dumb ballistic container, and have, e.g., OMS and RCS motors, propellant and the weight/complexity/cost penalties that come with them.
Which is why larger, more infrequent and expensive missions will remain the norm for the foreseeable future--with or without a space gun or its ilk.
4. In short, we need an orbital infrastructure that can handle smaller/dumber vehicles. That doesn't exist, and few if any of these proposals account for it. With, e.g., a group of ion/electric tugs it may make more sense. That is, something that can cost-effectively collect those smaller/dumber vehicles and bring them to where they're needed.
You'll need conventional lift to get the tools up into space to build an orbital mining facility. This air-gun can be used to lift all the materials that those tools will use to build the mining facility and fuel for the crafts that will go get the asteroids and coax them back. But once that's done, we ought not need the air gun nearly as much or at all.
Depends on what you're planning, really. If your goal is to actually spread the human race out from Earth, this could be used long-term. Just keep sending up loads of water and compressed air, etc., for however long you can afford to do so. Keep the stuff in a stable orbit and just leave it there for however long you need (years, no problem, really). Once you're ready to use it (in LEO, at a Lagrange point, on the Moon, Mars, etc), move it to where you need it, as the most costly part of getting it into orbit has already been done.
That's one of the biggest problems with the U.S. space programs, the lack of long-term thinking and planning (and funding for a long-term strategy).
I've heard it argued by folks who sounded like they knew their stuff that it's much cheaper to do it by dragging in asteroids (maybe one with a cubic mile of ice in it) than to shoot it up from earth. I admit, I haven't seen the numbers.
Considering we just hit the Moon to try to figure out how much water ice is there, it seems unlikely that we have any good ideas on which asteroids have water ice in them, much less the ability to bring them to where we need them (yet). That's more the type of project I'd expect a few decades _after_ we do what this project is talking about. All in good time, my friend...