When You Lose Air in Space, Your Body Suffers an Ungodly Death

Space is fraught with potential disaster scenarios — chief among them is the possibility that a spacecraft could lose air pressure and oxygen and suddenly become a death trap. That scenario actually manifests several times during the new film Passengers, in which Chris Pratt’s and Jennifer Lawrence’s characters must contend with a loss of air pressure several times. And each time, they manage to live.

Naturally, there are Hollywood liberties taken when portraying such an event in Passengers, and in any other science fiction film for that matter. What happens when you actually lose air pressure and oxygen in a spacecraft? It really depends on how quickly of a drop we’re talking about.

For instance, the real Apollo 13 mission experienced a blown oxygen tank, and the other was also leaking fast. The crew wasn’t instantly in danger of being unable to breathe — they had time and were able to stop further leaks, and were able to maintain enough breathable air to make it home.

But what happens in a scenario that’s acting a bit faster? Well, let’s say you’re losing air pressure as fast as possible — as if you’re being thrown into a vacuum almost instantly. You won’t die instantly, but you will black out in about 15 seconds, because in that amount of time, deoxygenated blood will arrive to your brain. With no oxygen available to help in metabolic processes, the brain will shut down pretty fast.

There’s another issue — extremely low pressures will force the gas exchange in your body to start reversing itself. The way your red blood cells pass oxygen back and forth is through hemoglobin — and hemoglobin requires a certain pressure in order to absorb and release oxygen. In a vacuum, the oxygen will get pulled out of your body and thrown into the lungs, where its released out of the body. If you try holding your breath, your lungs will probably rupture.

You’ll still be alive for another two to three minutes or so, but you probably will be fast unconscious before then. But your body will undergo all the symptoms of hypoxia, or oxygen deficiency. You’ll lose vision, you’ll convulse, and your skin will turn blue. In addition, your dermal tissue — the layer just under your skin — will start to swell up since the water in your muscles is rapidly evaporating. This might cause your body to blow up to twice its normal size.

But you’re not beyond saving — at least if no more than 90 seconds have passed. It’s after this point that things start to get really bad. Your blood pressure will also fall, and to a point where it can start to boil. Yes, literally boil. This will wreak havoc on your organs, especially your heart, and potentially put you beyond saving.

There’s a bit of historical data to go by — in 1965, an astronaut in a space suit was exposed to a near-vacuum environment for about 14 seconds after his suit experienced a leak. He lived, but reported that just before he blacked out, he could sense the water on his tongue start to boil. Three Russian cosmonauts aboard in 1971 were exposed to similar conditions as well within an orbital module, when a malfunction caused the spacecraft to lose air pressure within 30 seconds. One member managed to close the valve manually (which takes 60 seconds) but only managed to get it half closed before passing out. All three died.

If you were to lose pressure aboard a spacecraft in a slower fashion, you’d probably have more time to find out what went wrong and fix the issue before you run out of air. But remember the human body generally can’t go more than three minutes without oxygen before experiencing brain damage.