Paul Kingston, Queensland asked:
If an astronaut is stuck in space, would it be possible for them to project themselves towards Earth and re-enter the atmosphere with only a spacesuit? Could their spacesuit handle the re-entry temperatures?
We put this question to Dr Phil Rosenberg from the Open University, who worked on the Huygens probe:
"OK so our astronaut bails out of his rocket. What would happen then? Assuming heís in orbit around the Earth, actually not a lot! Both the astronaut and the rocket are in orbit around the Earth going at about 11km/s or 24,000m/h. They basically both orbit together. If the atmosphere there was a vacuum, thereís no atmosphere at all then that would mean the astronaut would stay in orbit forever. It happens that thereís a little bit of atmosphere up there. A tiny amount about a thousand, trillion, trillion times thinner atmosphere than there is at the surface of the Earth. That tiny amount of atmosphere will put a tiny bit of drag on the astronaut and as time went on that drag would slow the astronaut down. As he slowed down he would start to descend until eventually the atmosphere is thick enough that he could just fall to Earth.
Unfortunately, itís not great news for the astronaut because the atmosphereís so thin it would take him about a year to get slow enough that he would just fall to Earth. Because the astronautís travelling so quickly, 24,000m/h, as he starts to slow down and go into the thicker atmosphere the friction caused by the drag will heat him up and burn him in the atmosphere. In order to avoid that essentially what youíd have to do is slow yourself down from that 24,000m/h to essentially 0. Even the shuttle canít do that at the moment. The shuttle has a special thermocoating on the underneath it to re-enter the atmosphere. As it enters the atmosphere, itís travelling at 17,000 m/h. Even the shuttle canít slow itself down enough. Having said that, the astronaut is a little bit lighter than the shuttle so a decent sized rocket engine will slow him down enough but unfortunately most astronauts arenít equipped with such devices.
Unfortunately for our stranded astronaut I think itís pretty close to impossible, or at least very difficult in our space suit that we have to survive re-entry. I think our astronautís going to need some sort of escape pod or some sort of space vehicle to get back down form space to earth and survive the really difficult conditions that are involved in that."
"You could do this if youíre only going to 100-110,000 feet, thatís a project that Iím working on right now. Iím not re-entering into the atmosphere. You can freefall from that altitude and youíre going to get up to a speed of 900m/h but you will not feel that speed because the atmosphere is so thin. Youíd only feel maybe 150m/h of actual wind resistance against your body. The outside layers of your suit would only be maybe 200 degrees temperature with the friction that you have in the thin air. So yes, that is possible to do, a parachute jump from that height, but definitely not possible to do a parachute jump or exiting out of a space craft. Youíll never be able to enter back in."
Well, in space if you project yourself in one direction, you keep going that way till you hit something.
Spacesuits have many functions, but i don't think one of them is to survive re-entry or temperatures that high. So i would say it was not possible. paul.fr, Thu, 29th Nov 2007
Didn't the Russians do this with a suit packed with old clothes or other material? Sent it floating towards earth and watched it burn up. paul.fr, Thu, 29th Nov 2007
I think that if the space suit was specially designed for protecting the wearer during re entry into Earths atmosphere, (making the space suit essentially a space craft!), It would work. A suit made for "normal" activity, (like making repairs and stuff outside the space station), would burn up in a most interesting and excruciating way....unless your atmosphere entry speed was controlled to reduce the heat/friction associated with high speed.
i don't think so, the heat shields on the shuttle absorb heat, surely even if the suit did survive some of that heat would transfer to the wearer, and cook him. paul.fr, Fri, 30th Nov 2007
If one is talking about a space suit that follows the contours of the human body, I would have thought the complex airflow over that suit would be fairly difficult to manage if it is happening sufficiently fast to need an ablative coat. Furthermore, if the space diver is travelling that fast, then I would imagine it would not be possible to deploy chutes until there has been sufficient loss of velocity to not burn up the chutes on deployment, but there is still the risk of the space diver (in the absence of stabilising chutes) going into a very dangerous flat spin.
So how fast would someone travel, at peak velocity, falling from space towards Earth? I had heard claims of speeds exceeding 20 miles a second. Obviously you would accelerate to a very high speed due to the thin atmosphere and then decelerate again as the atmosphere increased in density. What does everyone think?
No idea on that one, Chris. But, the fastest freefall to date is 614 mph from 102,800 feet by Joseph Kittinger. paul.fr, Sat, 1st Dec 2007
Ah, I missed your post Dave...sorry about that, and thanks for pointing it out George.
I don't think a space suit on its own could do it but I think a parachutist ought to be able to survive.
I realise that it would need to be a big 'chute- particularly in the outer atmosphere. I was just pointing out that, in principle, it can be done. Bored chemist, Sun, 2nd Dec 2007
ammmm.... i dont think that the astronaut cant travel in space if he got stuck there.
Didn't somebody jump out a balloon from a great hight, a long time ago, and didn't have any problems?
Yes, and it was mentioned in the 8th post in this thread 30/11/07. Bored chemist, Wed, 9th Jan 2008
I think we discussed something like this before.
why do we have to orbit...? cant we just get high enough above to just hang loose in space....then enter very slowly in a straight line? erm....no i guess earth would just zoom off and away right?! :-P haha Paul, Sun, 30th Aug 2015