Running out of air in spacesuit vs removing helmet

[SRB]

I was curious, if an astronaut is stuck on mars with no chance for rescue, would it be better for him/her to wait for the suit to run out of O2, or to just remove the helmet?

How would each feel?

I was inspired by this clip: 

 

 

[Shpaget]

After removing the helmet on Mars, you get about 15 seconds of consciousness. A few minutes later your brain is severely damaged and soon you are dead.

On the other hand, you don't just run out of oxygen in a spacesuit, unless you are experiencing a sudden malfunction or breach. It takes a bit of time for the system to lose the capability to support life.

I'd say there is no circumstance where it would be beneficial to remove the helmet, unless the inside of the suit is on fire and you want a somewhat quicker death.

[mikegarrison]

59 minutes ago, Shpaget said:

I'd say there is no circumstance where it would be beneficial to remove the helmet, unless [...] you want a somewhat quicker death.

I believe that was the point of the discussion.

[SRB]

I meant that if the astronaut ran out of O2 from being in it far longer than planned, which would be better.

Edited April 25, 2019 by ErinBensen

[kerbiloid]

Spoiler

Make an arrow of stones pointing at some landscape detail like a crater, write "NEVER!!!" on it.
Take off the gloves. The left one put near the arrow, the right one take with you and start running away directly to the south (or north, doesn't matter) until fall.

The feelings are same, but the fun is much greater.
Even centuries later they still will be discussing the horrible and mystic accident on the Martian base, and what did these signs mean.

 

Edited April 25, 2019 by kerbiloid

[tomf]

The decompression from removing your helmet is going to cause some expansion injuries which would probably be pretty painful.

However if you suit is out of O2 then the level of oxygen is just going to drop, if it is still able to remove the CO2 then you are just going to fall asleep. People diving on rebreathers sometimes die because they failed to turn their oxygen on. If they had noticed it would have been the work of a second to turn the oxygen valve located right by their right hand.

[Shpaget]

There have also been aircraft accidents (N47BA for example) where pilots fell unconscious due to decompression.

The investigation determined that the emergency checkbook did not have "Put on the oxygen mask" as the very first thing in the check list.

This is a good video showing the effects of oxygen deprivation, but with much more oxygen in the atmosphere then there is on Mars.

If the goal is to live for as long as possible, staying in the suit is the best option, since there will be at least some oxygen for quite a while.

[kerbiloid]

Spoiler

Also think positive and don't be selfish.
Don't spend the air from the suit balloon.
Maybe a year later it will save the life of another spaceman.

 

[Gargamel]

Well, hypoxia is a fairly mundane way to die.  You just kind of 'shut down'.  There would be some panic as you know you are going to die and the stress involved with that.

Or we could open our helmet and add explosive decompression injuries along with some frostbite to the hypoxia.... 

[Bill Phil]

28 minutes ago, Gargamel said:

Or we could open our helmet and add explosive decompression injuries along with some frostbite to the hypoxia.... 

I mean, sure, the atmosphere is cold... but there's not much atmosphere to change your temperature that fast. You're dead in minutes, if not faster, so frostbite wouldn't be a thing.

Basically the low density of the atmosphere is likely to hamper heat exchange processes, similar to vacuum.

[Gargamel]

4 minutes ago, Bill Phil said:

I mean, sure, the atmosphere is cold... but there's not much atmosphere to change your temperature that fast. You're dead in minutes, if not faster, so frostbite wouldn't be a thing. 

The evaporation/sublimation of the moisture in your eyes, cavities, and skin will feel like frostbite.  A piercing coldness.  But yea, the affects of frostbite are at the end of the list of severe problems at the time,  But for choices of how to go, painfully cold is not on my preferred list. 

[Bill Phil]

Just now, Gargamel said:

The evaporation/sublimation of the moisture in your eyes, cavities, and skin will feel like frostbite.  A piercing coldness.  But yea, the affects of frostbite are at the end of the list of severe problems at the time,  But for choices of how to go, painfully cold is not on my preferred list. 

The skin is actually a pretty good membrane for keeping things in. It'll expand, but it'll keep the contents under pressure.

The eyes will certainly be experiencing some serious pain.

[Gargamel]

1 minute ago, Bill Phil said:

The eyes will certainly be experiencing some serious pain.

Yeah, at this point, I really don't care if it's barotrauma or frostbite, I really want to go peacefully, not in pain.

Reminds me of a joke:

When I die, I want to die peacefully in my sleep, just like my grandfather.

Not screaming, like everybody else in the car. 

[mikegarrison]

41 minutes ago, Gargamel said:

Well, hypoxia is a fairly mundane way to die.  You just kind of 'shut down'.  There would be some panic as you know you are going to die and the stress involved with that.

A buildup of CO2 is not as benign (symptom-wise) as just a lack of oxygen. So the exact failure mode matters.

[Gargamel]

Just now, mikegarrison said:

A buildup of CO2 is not as benign (symptom-wise) as just a lack of oxygen. So the exact failure mode matters.

That it does.   Hypoxia will induce some panic as I mentioned (poorly), but hypercapnia will allow you to fall into stupor and then drift away, with some hyperventilation before hand.   

It depends on the exact mechanics of the suit, will the scrubbers get rid of the Co2 and the O2 fail, or will the Co2 buildup first?   If the Co2 builds up first, I'd say there is a design flaw in the suit, as all the extra O2 pumped into your suit would not make a difference.  But the OP said O2 will run out, so...   Either way, I'm not intentionally taking the dang helmet off.   That's gonna hurt.  Panic might drive me there though. 

[kerbiloid]

So, go holotropically.