18 thoughts on “A New Space Race”

  1. One would think from first principles that solar powered directed surface volatilization would be a far more efficient and easier accomplished method of performing small delta V changes in asteroids and comets.

  2. So they are going to use the gravitational attraction between the spacecraft and the asteroid. Interesting that the thrusters would have to do the same amount of work as if they had a physical connection. You could get more traction with a piece of thread.

  3. Interesting that the thrusters would have to do the same amount of work as if they had a physical connection.

    There’s this cool concept called Conservation of Energy you may want to look into sometime.

    One would think from first principles that solar powered directed surface volatilization would be a far more efficient and easier accomplished method

    Only if one has forgotten that (1) asteroids have already been exposed to solar radiation for umpty million years. If anything was thus vaporizable, it’s vaporized long ago; and (2) if you mean to boost the photon energy — the usual sci-fi solar-powered lasers yadda yadda — then you need to factor in the appalling thermodynamic energy losses involved in going so steeply up the entropy gradient. Ordinary lasers, for example, convert about 1% of their input energy to output photons.

  4. That and another problem with solar powered directed surface volatilization is that most of these asteroids have a significant rotation rate. That would make getting a consistent outgassing in a desired direction difficult.

  5. if you mean to boost the photon energy — the usual sci-fi solar-powered lasers yadda yadda — then you need to factor in the appalling thermodynamic energy losses involved in going so steeply up the entropy gradient. Ordinary lasers, for example, convert about 1% of their input energy to output photons.

    Actually, I was thinking more along the lines of static concentration with lightweight metallic concentrating reflecting mirrors a few microns thick.

    But if you want to beat your brains out with industrial scale hydrocarbon combustion for mere heating and ground transportation, and then force the world to your idiotic worldview with ever more guns and bombs, in order to obtain more oil and gas, when vastly more simple and elegant solutions exist, be my guest. I’m certainly not going to try and stop you.

  6. That and another problem with solar powered directed surface volatilization is that most of these asteroids have a significant rotation rate. That would make getting a consistent outgassing in a desired direction difficult.

    The asteroid rotation is irrelevant when the out gassing is unidirectional.

  7. You are, Key? Hmm. Coupla’ problems come to mind. The most obvious is larry’s point, which is that your asteroid is rotating. So the surface is going to move under the hot spot at the focal point of your mirrors. Are you going to heat the entire surface? That won’t give you a rocket effect, of course. You’d have to simply vaporize the entire asteroid. You are talking big mirrors, I take it?

    If you manage to synchronize your mirror to the asteroid’s rotation, which presumably requires a fairly close orbit, now you’ve got a jet of iron vapor pointed at your mirror. Seems problematic, both from the point of preserving your mirror’s integrity and compensating for the momentum transfer. Conservation laws suggest you’ll use up more fuel station-keeping than you’d need to move the asteroid directly.

    when vastly more simple and elegant solutions exist,

    Well, simple and elegant solutions always exist in the mind. The real trick is making them exist out here in the real world.

  8. Are you going to heat the entire surface?

    No, just a single spot at the optical caustic. One can assume that the directed energy is decomposing and vaporizing material and not ejecting actual particulate matter. The fact that the spot is moving across the surface of the asteroid due to rotation is irrelevant.

    Let’s do another though experiment. Let’s say this large light solar concentrator is station keeping above one side of the asteroid. That requires thrusting directed at the center of the asteroid. Clearly that thrust is going to also impinge upon the asteroid on one side only. One also must then argue that the solar concentrator is a gravity tractor. I haven’t performed any analytical calculations quantifying the magnitude of the opposing forces involved, these are just though provoking ideas. For instance, if the solar concentrator is in orbit about the asteroid, one could direct solar energy at the surface during a short period of orbit. Again, the rotation of the asteroid itself is irrelevant to the thrusting.

    I can only assume that the gravity tractor enthusiasts have considered all the competing methods of asteroid deflection, no? Or perhaps not.

    Well, simple and elegant solutions always exist in the mind.

    That’s why I’m engaging in thought experiments considering a credible alternative to gravitational tractors, which also only occurs in the mind.

    Solar irradiance, solar energy conversion, solar thermal and solar concentration, and liquid cryogens also exist in reality, so I have no problems exercising thought experiments which incorporate them.

    With respect to heating and cooling, insulation is a well known concept.

  9. But if you want to beat your brains out with industrial scale hydrocarbon combustion for mere heating and ground transportation, and then force the world to your idiotic worldview with ever more guns and bombs, in order to obtain more oil and gas, when vastly more simple and elegant solutions exist, be my guest.

    o_O

  10. I guess you consider energy conversion and momentum transfer and change to be off topic. I suppose you have thought that through, right?

    Think it through, you can do it!

  11. I always liked the idea of painting the NEO and letting the difference in light pressure do the rest. It would be interesting to test it on a NEO to see just how effective it is.

  12. I always liked the idea of painting the NEO and letting the difference in light pressure do the rest. It would be interesting to test it on a NEO to see just how effective it is.

    That’s a good idea. These kinds of thought experiments do have some value. It would be interesting just to cover half an asteroid or comet (in your simulated mind of course) and then compare the change in outgassing from one side to another, and then compare that with your proposed albedo change. In other words, what are the magnitude of YORP effect forces, as opposed to the forces of actual albedo induced outgassing, and minimizing the effects of outgassing by simply covering part of the asteroid or comet with a simple vapor barrier. It seems to me that lots of different approaches would be viable over a wide variety of time scales, and that these kinds of directed energy ideas would also be applicable to our now severe near earth orbital debris problems too.

  13. Thomas that was my thought too. I’d like to see a comparison betwen paint and plausible gravity tractors.

    I wonder if the paint would weigh so much that you’d be better off keeping it in its container and using it as a gravity tractor…

  14. The 11-ton “gravity tractor” would have to launch 15 years before a predicted collision between an asteroid and Earth, according to the BBC.

    15 years? Wow, that sounds very useful.

  15. I guess you consider energy conversion and momentum transfer and change to be off topic.

    Your NO WAR FOR OOOOIIIILLLLL” tirade was about momentum transfer?

    Sorry, I don’t speak loon.

  16. Your NO WAR FOR OOOOIIIILLLLL” tirade was about momentum transfer?

    No, it was about energy conversion, using technology that is now well over one hundred years old, when many alternative techniques exist.

    Sorry, I don’t speak loon.

    You should, you might be able to see and thus think out of your narrow box of religious, media and parental dogma, and thus accomplish something of actual scientific or technological significance in your life, beyond lolspeak on your ipod.

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