A recent New Scientist article discussed this issue. It reminded me of a question I received from a writer and included in my book Forensic & Fiction: Clever, Intriguing, and Downright Odd Questions From Crime Writers. Here is the question:
Q: What sort of damage does the human body suffer in the vacuum of space? How long can one survive and what will happen to the person who does survive? (My scenario involves an astronaut whose faceplate blows out, but not before he depressurizes his suit sufficiently to prevent immediate death — if that’s even a threat.)
A; First of all the victim would not explode as in the movie 2010. But some really bad things do happen internally and they happen very quickly. Whether he depressurizes somewhat beforehand or not, his survival would likely be measured in seconds.
Space decompression is similar to that of a scuba diver that rises too rapidly after a prolonged exposure to the pressures of the deep. In this case he is going from excess pressure to normal pressure. In space the victim goes from normal pressure to zero pressure. Same thing physiologically.
Though studies on the effects of exposure to a vacuum have been done on chimpanzees, there are no real data on what happens to humans exposed to zero pressure except for a couple of incidents where an astronaut or a pilot was accidentally exposed. Of course, rapid decompression has caused deaths in both high-altitude flights and in June, 1971 when the Russian spacecraft Soyuz 11 suddenly lost pressure and killed the 3 cosmonauts on board, but survivors are few and far between.
On August 16, 1960, parachutist Joe Kittinger ascended to an altitude of 102,800 feet (19.5 miles) in an open gondola in order to set a world record for high-altitude parachute jumping. He lost pressurization in his right glove but proceeded with his ascent and jump. He experienced pain and loss of function in his hand at high altitude but all returned to normal once he descended via chute to lower altitudes.
In 1965 at NASA’s Manned Spacecraft Center near Houston, TX, a trainee suffered a sudden leak in his spacesuit while in a vacuum chamber. He lost consciousness in 14 seconds, but revived after a few seconds as the chamber was immediately re-pressurized. He suffered no ill effects—due to his very brief exposure—but stated that he could feel water boiling on his tongue. I should point out that in chemical and physical terms boiling simply means the changing of a liquid to a gas. This can be accomplished by adding heat or by lowering the ambient pressure. So in this case it wasn’t that his tongue became hot or anything like that but rather that the pressure was so low the water in his mouth changed to its gaseous phase.
A case of partial, prolonged exposure occurred during an EVA (space walk) in April 1991 on the US space shuttle mission STS-37. One astronaut suffered a 1/8 inch puncture in one glove between the thumb and forefinger. He was unaware of it until later when he noticed a painful red mark on his skin in the exposed area. It appeared that the area bled some but that his blood had clotted and sealed the injury.
So, what happens to a human exposed to zero pressure? Since there is no oxygen in such an environment, loss of consciousness occurs in a matter of seconds. Also, if the victim held his breath (don’t do this during scuba diving when coming up from depths either), the air in his lungs would rapidly expand and his lungs could be damaged, bleed, or rupture. Better to open his mouth and exhale the rapidly expanding gas from the lungs.
Water in his blood stream would immediately begin to “boil.” That is, it would turn to its gaseous state. This is similar to popping the top on a soft drink. With the release of the pressure the carbon dioxide dissolved in the drink immediately begins to turn to its gas form. Same thing happens in the blood at zero pressure. This causes pressure to build in the blood system and the heart stops. Bubbles may appear in the blood stream and these can cause damage to the body’s organs, particularly the brain. As a result, the brain and nerves cease to function. This increased pressure also causes the tissues of the body to swell but they will not explode.
Exposure to heat or cold or radiation might also occur but it will do little harm since the victim would already be dead.
But what if the exposure is brief and the person is rescued? Treatment would be to immediately return him to a pressurized environment and give him 100% oxygen. He may survive unharmed or may have brain and nerve damage which could be permanent.
For your scenario, the victim’s faceplate would rupture and he would begin to exhale air. He would lose consciousness in 10 to 20 seconds and would then die in short order. If he were quickly rescued, he would be returned to the spacecraft, which would be pressurized, and he would be given 100% oxygen via a face mask. He could survive intact or with brain damage. It’s your call. Either way works.