Space, Technology and Society

Unconventional Space Access

67 Comments

I’m doing a piece for Popular Mechanics on alternatives to rockets, and I was going to cover rail guns, gas guns, space elevators, sky hooks, and perhaps the launch loop. Does anyone have any other suggestions?

[Update a while later]

Folks, when I say alternatives to rockets, I am including all vehicles that employ chemical rocket engines, including airbreathers. As I said, unconventional.

[Update a few minutes later]

OK, I’m thinking of three categories: cannons (whether EM, chemical, whatever), external energy (laser, Orion), and momentum exchange (tethers, space elevators, compression towers). I know the latter isn’t really momentum exchange, but it fits sort of. The former don’t work well for passengers, but are well suited to bulk delivery of low-cost stuff (e.g., propellants), and the latter require very high up-front capital costs, in general. With a lot of tech risk.

67 thoughts on “Unconventional Space Access”

  6. Dare I say it? Combined cycle propulsion. Generally with a strong rocket component of course, so that may fall outside your definition.

  9. I agree with MPM. Combined cycle may be part rocket, but still deserves mention–especially with Skylon under review. It’s definitely “unconventional space access.”

  14. Geoffrey Landis’s space tower concept – a compressive tower that extends into space (~100km height or so). Using it as a launch platform of some sort.

  15. Folks, when I say alternatives to rockets, I am including all vehicles that employ chemical rocket engines, including airbreathers. As I said, unconventional.

    In that case, I second the mention of JP Aerospace’s airship-to-orbit concept. It eliminates the need for heat shields during reentry, since reentry is reduced to a very gradual process.

  17. JP Aerospace’s airship-to-orbit concept.

    Have they said anything about this recently? The limitations on hypersonic L/D ratios (particularly in a molecular flow regime) made the entire concept seem very dubious.

  19. JP Aerospace’s airship-to-orbit concept.

    Have they said anything about this recently? The limitations on hypersonic L/D ratios (particularly in a molecular flow regime) made the entire concept seem very dubious.

    A little OT – my calculations way back inferred that it needed an L/D of something like 100:1 (not really a straight aerodynamic possibility at that speed). I wondered about maybe some type of levitation based on charging the skin and interacting with the ionosphere – but I have no idea.

  22. Jut make sure and warn people if you are going to build a giant space cannon, taking a job for an anti Israeli middle easter country could be bad for your health.

    Gerald Bull could confirm this if you have a good medium to contact the other side.

  24. We are talking about launching from the surface of the Earth right? In that case I would go for the following long term research:

    – beamed propulsion (laser, microwave)
    – pulse detonation engines (Orion)

    If we are talking about near space travelling (Earth, Moon, Mars) it would be:

    – solar thermal propulsion
    – nuclear thermal propulsion with LOX afterburning
    – mass drivers

    For deeper space exploration:
    – solar sails

    Things I did not see mentioned here:
    – anti-matter catalyzed nuclear pulse propulsion.
    – nuclear thermal using a lightweight reactor (e.g. Dumbo or Timberwind). Is the T/W ratio for a stage larger than 1?

  25. Have been doing quite a lot of work on the concept of a magnetic catapult. OK for Aircraft, but there are too many intractable problems with acceleration to very high, let alone orbital, speeds in the lower reaches of the atmosphere.

    Best we can do right now is use the system to cover the steering losses associated with pulling a horizontally launched vehicle to near vertical before using more conventional propulsion techniques.

    As you may guess vertical launch is a much better solution!

    Have other thoughts to explore and perhaps build experimental hardware for test etc.

  28. How about orbital EM rails that boost sub-orbital vehicles into LOE and/or sell delta V to satellites? (Momentum exchange without the fiddly 100 km long rotating parts)

    And of course with hall effect thrusters to re-accumulate it’s own velocity.

  29. Well, all the good stuff’s been mentioned already. Except … how about Yogic Levitation – either clustered, or multi-stage? 😉

  33. At least no one has mentioned Polywell fusion. 🙂

    Hah! Pathetic pitiful technology compared to Lifters, EmDrive, or the magnificent Infinite Improbability Drive. 😀

  34. My personal favorite is the Texas Tower. It’s my personal favorite because I created it….

    It’s an artificial mountain built in Texas, completely bisecting the state from west to east, and standing 100 km high at its highest point. From the north or south, it looks like a great big rectangle with a gravity turn cut out of it.

    On top is a track, with a linear induction motor to accelerate payloads to orbital speed. The power source would be solar panels on the sides, above 100,000 feet so as never to be obscured by clouds.

    At the maximum height, it would be about 300 miles wide at the base. But it’s feasible with available materials in the right configuration.

    Best of all, it buries the Texas Board of Education…

  35. If you want unconventional…

    Nuclear ramjet SLAM-derived airbreathing first stage, nuclear thermal upper stage.

  36. I wonder if the big mistake we make is liquefying the gases? Imagine the equivalent liquid mass of hydrogen and oxygen as gas in bags taking the vehicle up as high as they can. Then winch them into pre-combustion pressurized chambers to be fed into the rocket engines.

    I know it’s a wacky idea, but could it be made to work? I know oxygen is slightly heavier than nitrogen, but hydrogen should more than make up for that. Can the balloons be pumped into the engines fast enough?

    I’m too ignorant to know what might or might not work… it’s a tremendous advantage when I do hit the target.

  40. How about Gregory Benford’s Pinwheel from “Beyond Infinity”?
    imagine a structure several hundred kilometers long rotating in orbit such that the ends dip down through the atmosphere nearly to ground level, with the rotational velocity canceling the orbital velocity. The end of the structure momentarily hangs motionless over a spot on the earth, at which point you grab onto it. At the top of the cycle you let go and it flings you away into space. That would be quite a rush.

  42. The Inventions of Daedalus is a collection of columns of humorous, semi-plausible schemes from The New Scientist. One of them (Sep 20 1973) is for a long, narrow balloon (miles long, meters wide) filled with hydrogen and oxygen, separated by a thin, combustible barrier. The combination is lighter than air, so the tube should be able to float. The orbiter is effectively a ram jet that rides inside the balloon, gathering the gasses and burning them for combustion. The nice thing about this scheme is that the orbiter doesn’t have to carry its fuel or oxidizer–it’s just engine, guidance, and payload.

    I probably don’t need to point out the problems.

  45. All this fiddling around looking for different way to do the job is a waste of time. Chemical rockets are more than good enough to provide economical orbital access without looking for some new magic technology.

  46. john hare Says:

    Time, we have that to waste.

    Chemical rockets? “We’ve been there already, Buzz has been there.”

    Sorry. It had to be said.

  47. Tarhack Says:
    September 24th, 2010 at 4:02 pm

    That’s the “spaceport” from Don Kingsbury’s “The Moon Goddess and the Son” I believe. The spelling of Son is correct too. Fun story.

  48. I remember that novel for the summing up of bleeding heart leftist views by one character “the democrats would feed the seed corn to the hungry children”. All you need to know in one short sentence.

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