Myth: The instant you’re exposed to the near vacuum of space, you’ll lose consciousness, your blood will start to boil, and you’ll explode. (Other variations on this myth include you freezing near instantly from the extreme “cold” of space.)

In fact, so long as you don’t try to hold your breath, which would result in your lungs rupturing and thus pretty well guaranteed that the incident will be fatal, you’ll likely remain conscious for about 10-15 seconds. After that, you’ll be fine as long as you’re placed back in a pressurized environment within about 90 seconds. It’s even possible that some might be able to survive as much as 3 minutes, as chimpanzees are capable of this without lasting detrimental effect.

These numbers are based on both human accidents that have occurred and on experiments run on animals. For instance, in 1965, researchers at the Brooks Air Force Base in Texas ran a series of experiments on man’s best friend, dogs (dog lovers out there, prepare to be enraged). They exposed the dogs to a near vacuum (1/380th normal atmospheric pressure) for varying amounts of time to see how the animals’ bodies would react. In most cases, the dogs survived without permanent damage, so long as the time frame was less than 90 seconds. Once they pushed it to two minutes, the dogs suffered cardiac arrest and died.

During the experiments, the dogs became unconscious after 10-20 seconds. They also experienced simultaneous urination, projectile vomiting, and defecation, the latter two caused by gas from their digestive tract being rapidly expelled. Many of the dogs also experienced dramatic seizures. Some of the dogs ended up with a thin layer of ice on their tongues as the moisture in their mouths evaporated, cooling the tongue rapidly. Finally, the dogs’ bodies themselves swelled to nearly twice their normal size, so that they looked like “an inflated goatskin bag”.

You might think from this that there would be no way their bodies could recover from this, but in fact, as long as atmospheric pressure was restored before that 90 second mark (while the dog’s heart was still beating), they all survived with no apparent lasting damage. The immediate after effect was simply that they were not able to walk for about 10-15 minutes after normal atmospheric pressure was restored. A few more minutes later and their eyesight returned. Beyond that, the dogs were apparently fine.

So that’s dogs. What about humans? Chimpanzees were chosen here as the guinea pigs. They did much better than the dogs, with most able to survive for up to 3 minutes, with the record being 3.5 minutes. For those under 3 minutes, they not only were fine, but the researchers were able to confirm that their cognitive abilities, with one exception, were not damaged in any way.

We don’t just need to rely on animal tests though. Enough depressurization accidents have happened over the years for us to see that the typical Hollywood version of things isn’t at all accurate. One of the first such accidents was when a technician at the Johnson Space Center in 1965 accidentally depressurized his suit by ripping out a hose. Around the 15 second mark, other technicians started the process of re-pressurizing the chamber, but the process took long enough to get a brief glimpse of how a human would perform in that situation. Specifically, he remained conscious for 14 seconds. During this time, he remembered feeling the water rapidly evaporating off his tongue. He regained consciousness at around the 15,000 ft. atmospheric pressure level, which was about 27 seconds into the ordeal. The only residual effect noted was that he couldn’t taste anything for several days after the accident, though his sense of taste returned back to normal within a week.

In another accident, the person involved wasn’t so lucky. In his case, it took about 3 minutes to re-pressurize the chamber he was in. Once it was re-pressurized, the man gasped a few times, then ceased to breathe and no amount of manual artificial respiration could get him breathing again. So it would appear the 3 minute mark is just a little bit too long.

A worse incident, in that it included three people instead of one, occurred during the Soyuz-11 mission in 1971. During the crew’s decent back to Earth, 12 small explosives that were supposed to fire one at a time to detach the orbital module from the service module ended up firing all at once. The result of this was that the pressure equalization valve, whose function is to equalize the inside pressure of the capsule to the outside when atmospheric pressure reaches appropriate levels, opened and allowed air to escape from the module as they descended from orbit (beginning to lose pressure at 104 miles up).

The three crew members instantly knew what had happened and Viktor Patsayev, being the only one close enough to do anything about it, attempted to close the valve manually. This takes 60 seconds to accomplish and it took 30 seconds for the cabin to completely depressurize (at about the 15 second mark the crew would have only had about 10-15 seconds of useful consciousness). Despite all this, Patsayev almost managed to fix the problem, managing to close the valve half way before passing out.

The three men were exposed to the near vacuum of space for approximately 11 minutes and 30 seconds. The capsule landed without the recovery crew aware that there was anything wrong. When they opened the hatch, they found all three cosmonauts appearing as if they were asleep, showing no real tissue damage at first glance. It wasn’t until they looked closer at them that they noticed some tissue damage, though not any more severe than what often occurs during explosive decompression, despite the extended time in a vacuum.

So now that we have a pretty good idea of roughly how long you could last if your full body was exposed to a near perfect vacuum, what would happen if just one part of your body was exposed to the near vacuum of space, say your hand if you’re trying to plug a hole in your space ship with it? We can actually answer that question because of an equipment malfunction during Joe Kittinger’s record leap from about 19.5 miles up on August 16, 1960. During his ascent, the following happened:

At 43,000 feet, I find out [what can go wrong]. My right hand does not feel normal. I examine the pressure glove; its air bladder is not inflating. The prospect of exposing the hand to the near-vacuum of peak altitude causes me some concern. From my previous experiences, I know that the hand will swell, lose most of its circulation, and cause extreme pain…. I decide to continue the ascent, without notifying ground control of my difficulty… Circulation has almost stopped in my unpressurized right hand, which feels stiff and painful… [Upon landing] Dick looks at the swollen hand with concern. Three hours later the swelling disappeared with no ill effect.

His total ascent took 1 hour and 31 minutes, he stayed at the peak altitude for 12 minutes, and his total decent took 13 minutes and 45 seconds, so his hand was exposed to a near vacuum for quite some time without long term ill effects.

So to sum up, if exposed to the near vacuum of space, as long as you don’t try to hold your breath or impeded its decompression, you’d:

Remain conscious for about 10-15 seconds, during which time you’d feel the water evaporating off your tongue and the moisture on your skin doing the same, such as if you were sweating. (This would make the vacuum feel cold.)

You may or may not projectile vomit and defecate, as the gasses in your stomach and bowels are ejected rapidly (Mental note: might want to avoid chili and Coke before going into space.)

If your Eustachian tubes in your ears are blocked by ear wax or the like, you may have some inner-ear problems that result, but otherwise should be fine there.

Your heart rate will spike up, then steadily fall thereafter, as will your arterial blood pressure. Your venous pressure will steadily rise as gasses form.

Your body will swell up to as much as twice its normal size as your skin stretches, assuming you weren’t wearing a suit that constricted things. According to the Bioastronautics Data Book, with a properly designed and fitted elastic suit, experiments have shown that the formation of gas bubbles in your body fluids can be completely prevented as low as 15 torr (for reference 760 torr is normal atmospheric pressure and atmospheric pressure on the moon is 10 -11 torr. Further, 47 torr is the point at which your blood would normally boil.) The swelling of your body is due to the moisture in your soft tissue turning to a gaseous state. However, your skin is strong enough to hold it in. So you won’t explode, you’ll simply expand.

torr. Further, 47 torr is the point at which your blood would normally boil.) The swelling of your body is due to the moisture in your soft tissue turning to a gaseous state. However, your skin is strong enough to hold it in. So you won’t explode, you’ll simply expand. During this process, your body will continually eject gas and water vapor through your mouth and nose, resulting in these getting colder and colder as the moisture evaporates, possibly even freezing your mouth or tongue.

If you happen to be in direct sunlight, you can expect extreme sunburns without the Earth’s atmosphere or other medium to protect you from the intense UV rays of the Sun.

Your skin will start to turn blue-ish purple from lack of oxygen, a condition known as cyanosis.

Your brain and heart will remain relatively undamaged for a time and your heart will continue to beat until around the 90-180 second mark. As your blood pressure drops, your blood itself will begin to boil once the pressure drops below 47 torr, resulting in your heart stopping beating, among other problems. This doesn’t happen instantly, though, as is depicted in the movies. No animal or human has ever been successfully resuscitated in these instances once the heart stops.

If pressure is restored in time, you’ll find yourself temporarily blind and unable to move, but both of these symptoms will pass. You also apparently will lose your sense of taste for a few days.

On the flip-side, if you hold your breath or otherwise try to impede the rate at which air is exhaled during explosive decompression, the “lungs and thorax will become over-expanded by the excessively high intrapulmonic pressure, causing actual tearing and rupture of the lung tissues and capillaries. The trapped air is forced through the lungs into the thoracic cage, and air can be injected directly into the general circulation by way of the ruptured blood vessels, with massive air bubbles moving throughout the body and lodging in vital organs such as the heart and brain.” This goes for decompression in a commercial airplane at high altitude too, so make sure you don’t try to hold your breath if that ever happens to you on a plane.

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Bonus Facts:

There is a type of amazing animal that is known to be able to survive the near vacuum of space for as many as 10 days with no ill effect, and that includes being able to handle direct exposure to solar radiation during that span. These tiny animals, growing to about 1.5 mm, are called Tardigrades (also “water bears”). “Tardigrades” means “slow walker”. They were originally given the name “little water bear” because the way they walk resembles the gait of a bear.

On the whole, Tardigrades seem to be able to live just about anywhere. Depending on the species, they can be found high in the Himalayas and then down to as much as 13,000 ft under water in the ocean. They also have been found everywhere from the polar regions to the tropical equator. They further can handle temperature swings down near absolute zero and up to 304 degrees Fahrenheit. On top of that, they can take around 1,000 times as much ionizing radiation as most other animals and can live for as much as 10 years without water in a dehydrated state, snapping out of it once water is re-introduced to their environment. They can also survive down to the near vacuum in space all the way up to 6,000 atmospheres of pressure. (I for one welcome our new Tardigrade overlords.)

On airline flights, the reason that they tell you to put your oxygen mask on first before helping anyone else in the case of decompression of the plane cabin is because the time of useful consciousness in complete decompression of the plane is about 10-15 seconds, at which point your cognitive abilities will diminish and you’ll eventually pass out at around 15-20 seconds at 45,000 ft. (This is a major problem if you happen to be on your way or in the bathroom at the time of the decompression.) In the case of explosive decompression, the problem is estimated by some to be much worse due to the fact that the incident will cause your heart rate to skyrocket and adrenaline to surge through your body. So in these cases, the amount of useful consciousness you have is estimated to be closer to 6 seconds, which is probably just enough time to get that mask on.

Space doesn’t actually really have a temperature, per se, as you are insulated from other molecules thanks to the near perfect vacuum. You will, however, likely feel cold when exposed to a vacuum, as illustrated above, due to moisture rapidly evaporating off your skin and in your mouth and nose. Even without the moisture and no external heat source, eventually the heat from your body would all radiate away, but that would take quite a long time.

NASA has had one incident of someone’s space suit getting punctured while the person was space walking. The astronaut didn’t even know it happened until after he got back in the ship. The hole size was 1/8 of an inch, but his skin sealed it. Once he got back in the ship, he saw the red mark on his hand. He didn’t think anything of it, but ground control knew he had punctured his suit. They just hadn’t told him as his adrenaline levels and the like were already quite high from being out in open space.

During explosive decompression, the air may develop fog for a time as it loses its ability to retain as much moisture. The vapor that no longer can be held in the air then turns to fog. In the case of an airline plane, this fog can make it difficult to see throughout the passenger cabin until it dissipates.

While you won’t explode when exposed to the near vacuum of space, as some movies will show, you may end up getting torn to pieces, depending on your environment. This has actually happened before in a decompression chamber. Three of the SCUBA divers in the chamber at the time died from the event, but their bodies otherwise looked normal. The fourth wasn’t so “lucky”. The small hatch that blew in the chamber caused all the air to rush to it and out, along with that diver. His body was forced through the small opening and out. As you might imagine, the results weren’t pretty. With a little Googling you can even see for yourself (I don’t recommend it. If you’re into that sort of thing, though, also try Googling metal lathe accidents. Just remember, some things that have been seen, cannot be unseen. *shudders*)

Joseph Kittinger’s first high altitude jump at 76,400 ft on November 16, 1959, he nearly died. During the fall an equipment problem caused him to lose consciousness thanks to spinning at an extreme rate, resulting in extreme G-forces on his body. Luckily, his automatic parachute deployment system worked and he survived the leap.

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