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by nagrom 4980 days ago
A lot of comments on the SE site make the same point: it's clear that such a person needs to wear a space suit of some type. And it's clear that it is possible to do with an elaborate vehicle. So the question really just depends on how elaborate you allow the suit to be.

If you allow active propulsion systems, then the answer is certainly yes - but your suit now becomes a vehicle and that's probably not in the spirit of the question.

If your constraint is "No (active) propulsion system", then you can redefine the question:

"Is it possible to build a passive wing system to make a (slow, 30ms^-2?) controlled descent into the upper reaches of the atmosphere for a mass of approx. 200kg (man+suit) and, if so, what is the minimum temperature that the exterior of such a construction will reach during its deceleration phase? Are there man-made materials that can withstand such a temperature?"

My feelings are a) yes, b) way too high and c) no. The precise answer is left as an exercise to the reader ;=)

2 comments

I do not think it matters, but there is an extra (implicit) constraint: you would want the descent to be done in some reasonable timeframe (say a week)

Also, I think your "Is it possible to build a passive wing system" is too restrictive. If I had to design something for this, I would consider wrapping a huge balloon around the astronaut to limit the rate of descent. It could start out uninflated as a gigantic air brake, then work from a compressed air cylinder; at lower altitudes, it might be possible pump in air an/or heat air. 100% safe it would never be, but it might be possible to get something that works sometimes. Braking without melting/burning this thing probably might be a stumbling block, though.

I think your balloon idea has some merit. For much of the early fall, very little gas would be needed to support a very large balloon that would retard the fall and limit terminal velocity. If your velocity stays low from the start, you never have to worry about heat building up. As the descent continued, eventually the atmosphere would thicken to the point that the balloon provided actual buoyancy, and subsequently a controlled descent could be made. Perhaps two balloons would be required, one weak, large one for the initial fall at the edge of the atmosphere and another stronger one for the final descent through ordinary weather conditions. The question is, how big would that first balloon need to be at the altitude of the space station?
I did a little digging, and this question is not easy to answer. There is much material regarding atmospheric drag on satellites, but those calculations require the assumption of hypervelocity. I wonder whether a simple calculation based on particle density and momentum transfer, with the balloon essentially sweeping out a vertical column of atoms as it fell, would yield a good order-of-magnitude estimate on the drag force available.
At the start of the jump you're already going about 27000 km/h (ISS orbital velocity). The falling part of the problem isn't the hard part.
I'm assuming the orbital velocity has already been scrubbed off, and we're talking about a simple fall, which is more in the spirit (if not the letter) of the original question. Could you prevent the velocity from building up with a large drag device such as a balloon in that case?
To me, the question implied that the design of the suit would have to overcome that problem; but I can see it either way.

Check out http://en.wikipedia.org/wiki/Reentry , there is a section on an inflatable heat shield launched on a sounding rocket (so sub-orbital, but lower altitude).

The space shuttle descent was basically unpowered (it made an initial burn in orbit to put it on a path into the atmosphere, then after that it was just using thrusters to control orientation), so it's very much possible.