The bends in Astronauts?

Question

It is well known that divers have to surface slowly to avoid the bends or DCI due to N2 loading of the tissues. The biggest issue is near the surface where the biggest pressure changes occur.

What about astronauts, they go from a 1 atm pressure to 0 atm when going on a space walk. This would also cause N2 to come out of the tissues causing the bends.

What do the space agencies do to prepare astronauts for space walks so that they don't get bent?

Yes there is pressure in the suits but if the pressure was 1 atm I would suspect that the suit would be like a balloon and the astronaut would be unable to perform any tasks.

No my reason for the question was not to say get bent (your mind is obviously sicker than mine). Breathing pure O2 also has its problems as in flamability (particularly around Ti), O2 toxicity and CNS problems). The astonauts would obviously need to breathe high O2 percentages otherwise the PPO2 would be too low and they would lose consciousness

Answer 1

You do realize that astronauts on spacewalks wear pressure suits, don't you? At no time are they exposed to zero atmospheric pressure, as this would be fatal. However, the pressure in their p-suits is lower than in the shuttle, in order to make it easier to bend the suit's arms and legs, so before an EVA they pre-breathe pure oxygen for a time so that they don't get the bends. I somewhat suspect your reason for asking this question was so you could say "get bent".

Answer 2

Firstly the pressure suit. With respect, thinking that pressurising it to 1 atmosphere would cause ballooning is naive. The suit is designed to work with zero pressure outside, so therefore will be designed to take into account the effect of that pressure differential and still be useful. Indeed, a spacesuit includes a restraint layer, which is basically a fabric net over the rubber pressure vessel that prevents excessive expansion under pressure. WHat you see in a photo can often look unpressurised because you are only seeing an overlayer of the suit, loosely fitted over the pressure layer.

As for the bends, in the early space programs (Mercury, Gemini and Apollo) the spacecraft contained a pure oxygen atmosphere at 5psi. To purge the nitrogen from their blood the astronauts pre-breathed pure oxygen for a period before the flight. The spacesuits were only pressurised to about 3.5psi, also pure oxygen. Flammability is dealt with by making the suits out of non-flammable materials, and in zero G at low pressure the flammability issue is not as serious as you may think. Pure oxygen at full atmospheric pressure would be aproblem, as the crew of Apollo 1 found out in 1967.

The shuttle and space stations use a 1atmosphere air supply consisting of oxygen and nitrogen in the same ratios as in Earth's air. The astronauts do not suffer a drop in pressure when they go on spacewalks because the suits are pressurised, therefore no problems with the bends.

Answer 3

There is pressure inside their spacesuits. They are never exposed to vacuum. I am not sure what the pressure inside a suit is kept at, but I would guess that if it is less than what the ship/station they are in is at, there would be a process of getting them out of the suit [once back inside the station of course] that would include re-pressurizing at a safe rate.

Answer 4

The bends aren't a problem--the astronauts spacesuits are pressurized. And if the suits lose pressure, they still won't have to worry about the bends--because they'll be dead from suffocation and explosive decompression.