Running out of air in spacesuit vs removing helmet

[ErinBensen]

If an astronaut is trapped on mars and has no hope of being saved, which would be a better way of going: just waiting until his/her suit ran out of O2, or removing his/her helmet?

Based on this clip: https://m.youtube.com/watch?v=mJoUq3Y6tzY

[schlaugh]

The build up of CO2 in the suit would be highly stressful and cause a lot uncomfortable symptoms. Better to let all the air out at once (but exhale first please lest your lungs rupture); exposure to vacuum brings on unconsciousness within 10 seconds or so, death soon after. For all practical purposes, the air pressure on Mars is almost a vacuum, and is 96% CO2. By way of comparison, Earth sea level pressure is 14.69 PSI, the top of Mount Everest enjoys a relatively cushy 4.89 PSI, but on Mars the average pressure is 0.087 PSI.

From the Geoffrey A. Landis site linked above:

Bioastronautics Data Book, Second edition, NASA SP-3006. This chapter discusses animal studies of decompression to vacuum. It does not mention any human studies.

page 5, (following a general discussion of low pressures and ebullism), the author gives an account of what is to be the expected result of vacuum exposure:


"Some degree of consciousness will probably be retained for 9 to 11 seconds (see chapter 2 under Hypoxia). In rapid sequence thereafter, paralysis will be followed by generalized convulsions and paralysis once again. During this time, water vapor will form rapidly in the soft tissues and somewhat less rapidly in the venous blood. This evolution of water vapor will cause marked swelling of the body to perhaps twice its normal volume unless it is restrained by a pressure suit. (It has been demonstrated that a properly fitted elastic garment can entirely prevent ebullism at pressures as low as 15 mm Hg absolute [Webb, 1969, 1970].) Heart rate may rise initially, but will fall rapidly thereafter. Arterial blood pressure will also fall over a period of 30 to 60 seconds, while venous pressure rises due to distention of the venous system by gas and vapor. Venous pressure will meet or exceed arterial pressure within one minute. There will be virtually no effective circulation of blood. After an initial rush of gas from the lungs during decompression, gas and water vapor will continue to flow outward through the airways. This continual evaporation of water will cool the mouth and nose to near-freezing temperatures; the remainder of the body will also become cooled, but more slowly.

Got a bar bet going?

[ErinBensen]

No, just curious.
Thanks

[Grey]

The build up of CO2 in the suit would be highly stressful and cause a lot uncomfortable symptoms.

Hmm. The way that spacesuits work, though, is that they supply oxygen from compressed tanks, and scrub the carbon dioxide as a separate step. And I'm pretty sure that the canisters used for that scrubbing have a longer operating time than the oxygen supply. So although your oxygen would gradually run out, carbon dioxide levels would remain normal (unlike what would normally happen when breathing in a confined space). My understanding is that in this case, your body won't particularly recognize the problem, and you'll breathe normally until you pass out, without particularly noticing any ill effects. I remember an old TV series, called "The Body in Question", with an episode where the host actually demonstrated this (on himself, but under controlled conditions).

[Grey]

Oh, hey, here it is. The bit with breathing from a limited air supply with and without a carbon dioxide filter to show the difference is at the very end.

[eburacum45]

Jonathan Miller, no less. A true Renaissance man. Luckily he was able to renaiss after that rather eccentric experiment.

[Solfe]

Oh, hey, here it is. The bit with breathing from a limited air supply with and without a carbon dioxide filter to show the difference is at the very end.

Thanks for the link. I total forgot about that show. I'm pretty sure it was on CTV when I was a kid.

[Roger E. Moore]

If an astronaut is trapped on mars and has no hope of being saved, which would be a better way of going: just waiting until his/her suit ran out of O2, or removing his/her helmet?

I would go to work doing research and working to stay alive as long as possible, under the humorous thought that future explorers would name the base for me . I understand the question but do not see the method of dying as relevant. It's not how you die, it's how you live.

[publiusr]

Thanks for the link. I total forgot about that show. I'm pretty sure it was on CTV when I was a kid.

I seem to remember that as well. The scene where he is writing really brought it home.