Space, as a background, is a mainstay of sci fi. But space is hazarous, and if you’re to find yourself without air to breathe, that should probably be cause for alarm. Naturally, sci fi characters (much like real life astronauts) go to great lengths to avoid this. “Don’t leave your spacecraft without a protective suit” is generally some rather sound advice. Unfortunately, in many stories, that isn’t always an option.
Caution: This post has mild spoilers for Star Wars VIII: The Last Jedi, Sunshine, Gravity, and episode 7 of Cowboy Bebop.
There are a lot of stories, including a few high profile movies, where characters find themselves in space without a suit. Despite what you might think, this doesn’t always mean certain death – to the point that some audiences start to complain that this is unrealistic.
Turns out, it’s more realistic than you might think. Brief exposure to vacuum will not be pleasant in any way, but it’s certainly survivable.
Unless something like this happens:
There are actually a few different tropes all bundled up here, so I’m going to look at them one by one…
Space will not make you explode
The original version of Total Recall had some pretty grotesque scenes of people being exposed to vacuum (and the surface of Mars isn’t even vacuum!) but nothing that horrific would really happen.
You skin is tougher than you might think. While vacuum exposure would probably cause some swelling, you could manage a drop of one atmosphere without any permanently nasty effects. The thing to be worried about is your lungs – there is a very real possibility of a ruptured lung. This is known technically as pulmonary barotrauma, and is something which deep sea divers need to be careful of. Essentially, this is caused by your lungs expanding faster than they release air.
In other words, if you find yourself in danger of being thrown out of an airlock, don’t hold your breath. Spike Spiegel, in the screenshot to the right, got that part really wrong. It may seem counterintuitive, but releasing all the air from your lungs would increase your chances of survival.
In any case, survivable💀 does not mean pleasant. You’ll probably have several other health issues to contend with. Barotrauma will probably affect other parts of your body, like your eardrums and your gastrointestinal tract. You may be affected by decompression sickness (the bends), altitude sickness, or simple physical injuries. Interestingly, one counterintuitive sounding problem you may have is called hypocapnia – a reduced level of CO₂ in your blood.
Space will suffocate you
The main immediate problem would be hypoxia, or a simple lack of oxygen. This isn’t purely because you have nothing to breathe, either. Low pressure can cause deoxygenation of the blood and, even worse, this happens more rapidly at lower pressures. An average healthy adult would have about 14 seconds of consciousness after being exposed to vacuum. Which might be enough time to do what Spike Spiegel did and fire a gun to propel yourself in the right direction (that part was pretty much spot on).
The biggest problem, perhaps surprisingly, is not a lack of oxygen but ebullism – the formation of bubbles in your body fluids. This is pretty much as nasty as it sounds. The guideline usually given is that you’d have about 90 seconds to be repressurised. Longer than that, and you may not be able to survive.
Shorter vacuum exposure though, would be horrible but would probably have no lasting effects. So Kowalski opening the Soyuz capsule door and depressurising Dr Stone in Gravity would probably go exactly as in the movie, as long as she didn’t hold her breath. Though it would probably have burst both her eardrums. If it wasn’t a hallucination, that is.
We can probably also learn that you shouldn’t go to space with George Clooney, no matter how many amusing stories he has to tell.
Ebullism starts to happen at pressures of around 6.3 kilopascals, and is known as the Armstong limit, which leads me to…
You will not freeze to death in space
It’s a rather pervasive trope that space is cold. And, well, it isn’t. Not in a way that would have any meaning for a human who found themselves in space, anyway.
Freezing solid and then shattering, like in that one scene in Sunshine, won’t happen because there’s no way to cool that rapidly.
Your body heat is lost generally by two mechanisms – conduction and radiation. Radiation involves emitting heat as infrared, and at body temperatures, this is a very inefficient process. Conduction requires air molecules to collide with your skin and carry away excess heat (which is why cold air feels cold). Obviously, there’s no air in space, so conduction shouldn’t be a problem, right? Well, it’s slightly more complicated.
I mentioned the Armstrong Limit before. So the boiling point of any liquid varies with ambient pressure, which is why some people argue that you can’t make a good cup of tea at the summit of Mount Everest, because the boiling point of water is only 71°C up there🍵. The Armstrong limit is defined as the point at which liquids boil at human body temperature of 36.6°C. This happens at a pressure of 0.0618 atmospheres. On Mars, that’s about 10 times the average atmospheric pressure. On Earth, this happens at an altitude of around 18km🛰.
Anyway, needless to say, your blood, sweat, and tears literally boiling away is not good. The biggest concern is that it causes ebullism like I mentioned above. The other thing is that any fluids on the surface of your body will start to boil away. Sweat from your skin. Tears in your eyes. Saliva in your mouth🚀. These fluids boiling away will take heat with them very quickly – from thermodynamics, evaporation causes an increase in entropy, which makes it an endothermic process. In other words, as we all know, evaporating liquids cool things down.
Would this cool your skin enough for frost to form like in Guardians of the Galaxy? Hard to say. Probably not, truthfully, because there wouldn’t be enough water left on your skin to form into frost. You’d probably feel a sudden shock of cold, but you’d have other things to worry about.
Would this cool you enough to freeze you to death? No way. You’d die from hypoxia and ebullism long before you got that cold.
Wait, actually don’t bother. It won’t help.
The day side of the moon, in full sunlight, reaches a temperature of 127°C. It’s also hit by all of the Sun’s raw, unfiltered UV light, not to mention any charged particles which the Sun is streaming out. Seriously, without an atmosphere to protect you, a star is a pretty hazardous thing. If you were to be exposed to unfiltered sunlight without a space suit, all of that solar radiation would redefine sunburn.
If you were to find yourself on the wrong side of an airlock, you should really hope that you’re either in shadow, or a lot further from the Sun. If you were in orbit around Saturn, this would probably not be a problem. If you were in orbit around Mercury, well…
Whether this would be more deadly than everything else going on, I’m not certain. And I’m not sure I really want to do any maths to find out. If you were close enough to the Sun (or any other star) then it probably would be. I’m sure you wouldn’t immediately combust like in Sunshine, but still, I doubt it would be fun.
You can survive space
Provided you could get back into a normally pressurised environment quickly enough, brief exposure to space is something a healthy human can survive. How long you could survive depends on how strong your cardiovascular system is and how much body mass you have, but you’d probably have about 14 seconds of consciousness and 90 seconds before any fatal effects start to occur.
Yes, Peter Quill would be able to survive vacuum exposure like this to save Gamora’s life. Assuming that sequence was shown in real time, it was about 51 seconds of vacuum exposure. Realistically, he’d probably need medical attention, but eh, it’s a comic book movie. Admittedly, Gamora’s out there a lot longer, but she’s not human and also a cyborg death machine, so the usual rules probably don’t apply to her.
And yes, General Leia would be able to survive being briefly blasted into space. In fact, that one scene in The Last Jedi was extremely well done. No superfluous ice or explodey horror. She just used her few seconds of consciousness to save herself and then, obviously, needed proper medical treatment afterwards. I’d say it was arguably the most realistic portrayal I’ve ever seen on screen. Apart from, you know, the whole thing with The Force.
Anyway, while you might not die, I’d still recommend staying on the inside of any airlocks if you ever find yourself in space.
💀 I should note that while explosive decompression from 1 atmosphere to vacuum may be survivable, it can be lethal where higher pressures are involved. There’s documentation of at least one accident involving deep sea divers which is full of absolute nightmare fuel. Seriously, don’t look that stuff up unless you have a strong stomach.
🍵 Personally, I’d argue otherwise, given that a good cup of Japanese green tea is ideally brewed at around 70°C, making the summit of Everest a great place for a tea shop.
🛰 As a side note, we think of the International Space Station (ISS) as being, well, in space. Technically it’s not. It’s in free fall but it’s still actually inside Earth’s atmosphere. There isn’t much atmosphere, but it’s there. The pressure on the outside of the ISS is around 5×10⁻⁹ atmospheres. Which isn’t much use for a human without a space suit,
but it’s apparently enough to make the space station airlocks smell like burnt cookies.
🚀 There’s a story, which may or may not be true, about a NASA astronaut who was unlucky enough to put on a leaky suit once. Thankfully, he survived the ordeal. Apparently, the last thing he remembered before losing consciousness was the sensation of water boiling on his tongue.
A trope is a recurring theme in any narrative which conveys information to the audience. These are snippets of information which have somehow ended up in our collective subconscious as ways in which storytellers have gotten their points across. Overused tropes end up as clichés.
This article includes images from: Star Trek (2009), Cowboy Bebop, Gravity, Guardians of the Galaxy, Sunshine, and Star Wars: The Force Awakens. All images are used here for the purposes of review, criticism, and education in accordance with Fair Use/Fair Dealing policies.