#exposuretovacuum

[scriptastronomer]

Hi! I was wondering if you knew what would happen in you took your helmet off in space? I'm contemplating having one of my characters do this.

Short answer: Nothing good, then death.Longer answer: Nothing really bad for a few seconds, then nothing good, then death.So, something has gone wrong on your space journey. You have been caught in a bad situation and have to expose yourself to space for a short amount of time. For some reason, you opened your helmet or something happened to it.

First things first: You will not explode, turn inside-out, instantly freeze, or instantly boil. You will not have your eyes bug out and the blood vessels in your face will not all pop.

Sorry, Arnie. You’ll be fine. For a little while.

From the moment you open your helmet and expose yourself to vacuum, you have about thirty seconds without anything really bad happening to you. If you are exposed to unfiltered sunlight, you will probably get a slight sunburn (pure UV rays will do that - the closer you are to the Sun, the worse it will be).

After that, things start to go bad really fast.

After about ten seconds or so, you’ll start to get some swelling of the skin (not a lot and easily survivable) and some dehydration of the eyes. Your ears will probably pop, and you’ll feel your tongue start to dry out. So far, you’re okay and will have no permanent effects - if you get back to pressure before thirty seconds or so passes.

After that, you will start to run out of oxygen, and will probably pass out at around thirty seconds. If you have some warning and are able to take several deep breaths before exposure, you can probably survive slightly longer. DO NOT TRY TO HOLD YOUR BREATH! If you do, the pressure difference will probably damage your lungs. Ask scuba divers about what happens if they hold their breath when ascending. Same thing. At this point, you’ll probably get some permanent damage - extreme sunburn, or lung damage.

After ninety seconds in vacuum, death is probably unavoidable. If you get back to pressure before then, you have a very good chance to recover.

Of course, these are just guesstimates. NASA generally doesn’t go around deliberately exposing their astronauts to vacuum. Generally.

However, it does happen. in 1965, Jim leBlanc was accidentally exposed to total vacuum while testing a moon suit prototype. In the accident, his suit pressure dropped from 3.8 psi to 0.1 psi in 10 seconds (normal atmospheric pressure is about 14.7 psi).

Luckily, it only took just over a minute to restore full atmospheric pressure to the test chamber, but people can survive at a lower pressure than 1 atmosphere. LeBlanc survived with nothing more damaging than an ear ache.Yes, there is footage of the event, and Jim leBlanc tells you himself what it felt like.

So, make sure you check your equipment before you leave your spaceship. 

The life you save may be your own.