Physiological Effects from Exposure to a Vaccum

Vacuum doesn’t have a temperature of its own, so space is not really that cold. It’s a great insulator too, meaning that your core body heat doesn’t get sucked away. Without an atmosphere to transfer heat away, the risk of exposure is somewhat mitigated. The saliva on your tongue may boil off, as it’s not pressurized like your blood is, and you may get some frost on your skin. Sunburn from direct contact with the sun’s ultraviolet rays is a more immediate danger than perishing from cold. You’ll suffocate long before you freeze.

Your body is swelling during all this, too, pinching nerves and aching like hell, so don’t count on a lot of manual dexterity. If your plan for surviving an unpressurized spacewalk involves working a zipper or most portable electronics, you may be fucked. This is another reason why outer-hull control surfaces tend towards large, highly visible buttons.

The most important survival tip for vacuum exposure is not to hold your breath. With no external air pressure, the alveoli holding oxygen in your lungs will burst. This will hurt and may damage your ability to breathe should you get back to an atmosphere. So the very first thing you should do is exhale completely and get those gases out of your body. Realistically, rapid decompression is almost more dangerous than vacuum exposure. You may not have enough time to exhale in a sudden blowout, meaning that your lungs and eardrums may burst, your sinuses and soft tissue areas may be ruptured, and you’re more likely to succumb to hypoxia more quickly.

After your body has pumped the last of its oxygenated blood to your brain, you’ll lose consciousness. With the stress of shock and hypoxia that your body is going through, you’ll have only a limited amount of time before you pass out. For flats, this can be as short as 15 seconds. Morphs with basic biomods can retain consciousness for a minute or more. After you lose consciousness, you’ve got maybe another minute or two in a typical morph before you’re well and truly dying.

A good description.