A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

If you were thrown into the vacuum of space with no space suit, would you explode?

March 22, 1991

Dear Cecil:

After considerable debate and several fistfights in which I have been left friendless there remains a great "void" in my mind. What would happen if a person were thrown into the vacuum of space without protective clothing? Some bozos (e.g., my ex-friends) think you (the person thrown into space) would blow up. I however disagree. Please settle this festering wound.

Cecil replies:

You sound like a man with a problem, Juan. Maybe a lot of problems. But this time the facts are on your side. There is such a thing as "explosive decompression," but that merely refers to the sudden loss of pressure in an air- or spacecraft, not the effect on the occupants. Though your chances of surviving such an experience are slim, your body would not explode (although see below). In fact, if you were able to scramble to safety quickly enough (as the helmetless astronaut did in the famous scene from 2001: A Space Odyssey), you might emerge virtually unscathed.

To be sure, there are a few troublemakers who will give Cecil an argument on this. Some flight surgeons at NASA, for instance, say death in a vacuum would be almost instantaneous. They offer the following Technicolor scenario: your blood would boil, your eyeballs would explode, and your lungs would turn to red slush.

But the medical literature suggests this view is exaggerated. For one thing, I have never seen anything indicating your eyeballs would explode (although your eardrumms might burst). It's true that in the absence of ambient pressure your blood and other bodily fluids would boil, in the sense that they would turn to vapor. But that's not as drastic as it sounds. Your soft tissues would swell markedly, but they'd return to normal if you were recompressed within a short time.

It's conceivable your lungs might rupture, since in a vacuum the air in them would greatly expand. But experience suggests this is rare even if decompression is extremely rapid. The chances are much greater if your windpipe is closed, making it impossible for the expanding air to escape.

Death would not be instantaneous. It's believed you'd have 10-15 seconds of "useful consciousness" and it'd be several minutes before you'd die. If you were rescued within that time there's a decent chance you'd survive. Research with chimps and monkeys suggests that if you were exposed to a virtual vacuum for less than 90-120 seconds you might not suffer any permanent damage.

That said, there are circumstances involving explosive decompression in which your body might be torn to bits. This would result not from the exposure to a vacuum per se but from injuries caused by the accompanying air blast. I have here a medical journal article about a case of explosive decompression that killed four divers. (They went from high pressure to normal rather than normal to vacuum, but same idea.)

The bodies of three of the dead men were outwardly normal. The fourth man, however, was forced through a narrow hatch by the rush of escaping air and his body, to be blunt, was reduced to pot roast. Naturally, the authors of the article felt obliged to include pictures, including a close-up of what was left of the face. You might show them to your bozo friends next time they're chattering about blown up bodies.

More on explosive decompression

Dear Cecil:

One of your recent columns dealt with the issue of explosive decompression. Although your information was good, you should have mentioned the case history of near rapid decompression that killed three astronauts in 1971. Below is an excerpt from my 1990 book, Almanac of Soviet Manned Space Flight.

"At 1:35 AM, June 30, the crew fired the Soyuz retro rockets to deorbit and twelve minutes later separated from the orbital and service modules. At this time, the orbital module was normally separated by 12 pyrotechnic devices which were supposed to fire sequentially, but they incorrectly fired simultaneously, and this caused a ball joint in the capsule's pressure equalization valve to unseat, allowing air to escape. The valve normally opens at low altitude to equalize cabin air pressure to the outside air pressure. This caused the cabin to lose all its atmosphere in about 30 seconds while still at a height of 168 km. In seconds, Patsayev realized the problem and unstrapped from his seat to try and cover the valve inlet and shut off the valve but there was little time left. It would take 60 seconds to shut off the valve manually and Patsayev managed to half close it before passing out. Dobrovolsky and Volkov were virtually powerless to help since they were strapped in their seats, with little room to move in the small capsule and no real way to assist Patsayev. The men died shortly after passing out. Fifteen and a half minutes after retrofire, the pressure reached zero in the capsule and remained that way for eleven and a half minutes, at which point the cabin started to fill with air from the upper atmosphere. The rest of the descent was normal and the capsule landed at 2:17 AM. The recovery forces located the capsule and opened the hatch only to find the cosmonauts motionless in their seats. On first glance they appeared to be asleep, but closer examination showed why there was no normal communication from the capsule during descent.

"The Soviets had to give a detailed report on the accident to NASA in preparation for the Apollo-Soyuz Test Project, during which they said that the amount of tissue damage to the cosmonauts' bodies caused by the boiling of their blood during the 11.5 minutes of exposure to vacuum could at first have been misinterpreted as being the result of a catastrophic and instantantaneous decompression. The cause of death was pulmonary embolism."

There has yet to be released any substantial data on the damage to their bodies, but from the descriptions commonly published the damage was not immediately recognizable.

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A Straight Dope Classic by Cecil Adams
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