My kid has been asking me what happens to austronauts if they take their suits off in space. I cant explain it properly since I’m not entirely sure too.
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You body needs a certain amount of outside pressure to stay functional and you also need air to breathe. A spacesuit provides both by being a solid object that holds air inside of it at a safe pressure – basically its a giant balloon that has a person inside of it.
A secondary, but still very important, requirement of spacesuits is temperature regulation. Vacuums, and thus space, are odd in that it is both really hot and really cold at the same time. Without thermal regulation systems, a part of your body in sunlight would cook while the other side in the shade would freeze. To solve this problem, the suit needs the ability to circulate heat around, both cooling down areas in sunlight and heating areas in shade. In many cases during long duration spacewalks, enough of the suit will be in the sun to require the suit to have some way to radiate heat out – the human body should enough heat to keep it warm in the shade. Typically, this is done by having water pumped through the suit.
Some additional things that the suit needs to help deal with:
* Water and food. Spacewalks typically last a long time, and the astronaut will need to drink, and sometimes even eat. They cannot reach their face, so the suit needs tubes they can eat or drink from.
* Sweat. You cannot wipe your face, and the lack of gravity suits are normally operated under means the water won’t drop down. Without some method of handling this, an astronaut would eventually drown in their own sweat. It would also be very problematic if sweat got into their eyes – you’ve probably experienced that, but now imagine not being able to wipe your eyes to help either. Naturally, this would not be an issue if you had no spacesuit on – the sweat would just evaporate very quickly.
* Other body waste. A spacewalk likely lasts hours and it can take 15 minutes or longer to don and doff the suit, so the astronaut needs some way to go to the bathroom inside the suit. This is typically done by using a diaper, though a few other methods have been used but are often not practical. Naturally, this would not be an issue if you had no spacesuit on – the products would float away, and urine would tend to evaporate very quickly.
Not a huge amount is known about what happens if a person is directly exposed to a hard vacuum as doing so is very dangerous, even for short periods, however [an accident](https://www.popularmechanics.com/space/a24127/nasa-vacuum-exposure/) has revealed some information.
A few things of note. mostly from that incident:
* The human skin, eyes, and blood vessels can maintain enough pressure to keep your body intact and properly shaped. You wouldn’t explode or experience severe bleeding.
* You may get a nosebleed as the blood vessels in the nose are small and close to the surface. As with any nosebleed, the blood should clot and stop the bleed reasonably quickly.
* The pressure drop is not enough to cause the [bends](https://en.wikipedia.org/wiki/Decompression_sickness), which is where the tiny nitrogen bubbles that are always in your blood expand and cause major health problems.
* The pressure *will* cause exposed water to boil. This includes the salvia on your tongue and the mucus in your airways. This will *not* cause burning as the water is only at body temperature still.
* Depending on the speed of decompression, hearing damage can occur. In most cases, the pressure drop will be small enough or slow enough to limit this to just a temporary ear ache.
* It is impossible to hold your breathe, though no harm will occur from trying. The vacuum will effectively suck the air out of your lungs despite you best ability to hold it in. When blood passes the air exchange system in your lungs, it will even suck the oxygen out of your blood like it normally sucks the carbon dioxide out. This means you will run out of oxygen much faster than you would from other causes of asphyxiation.
* You will remain conscious for about 15 seconds. Most people will begin to lose function sooner.
* After about 30 seconds, major effects of oxygen starvation occur, including brain damage.
* Death will normally occur after about 90 seconds.
* You would not freeze solid for quite a long time – likely between 12 and 26 hours. The human body contains a lot of heat energy, and is constantly producing heat which would keep you warm until death (and decomposition will produce some heat after), especially when the only way you are losing heat is via infrared radiation – you are surrounded by what is basically the best possible insulator. And that is even without considering the radiation you would absorb from the sun.
Also, as a note, [NASA has a document](https://www.nasa.gov/sites/default/files/atoms/files/dressing-for-altitude-nov-2017.pdf) (PDF warning, and nearly 100 pages) that you may want to read over, which includes some kid-friendly activates you can try relating to space suits and high-altitude suits. Some of the activities can be easily done at home, while others require equipment you probably won’t be able to get cheap enough to be worth it. You can also see if a nearby science museum or school has the equipment.
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