April 26, 2021

Vacuum: a whole lot of nothing

Space, being the final frontier and all, has its fair share of inherent dangers should you choose to visit. One of them being there is not a lot of air to breathe so you have to bring it all with you. This is of course a great thing for science fiction writers to add Danger and Excitement to their work, and they usually get it wrong. Not the "no breathing" thing so much, but everything else. The various egregious errors I have encountered:

  • Explosive decompression, and I do mean explosive, on puncture
  • Instant freezing on puncture (OK, it was opening the helmet but still)

The best I've seen to date was a recent episode of "The Expanse", where a character (a very, very desperate character) launches out of an airlock sans suit to get to a different nearby ship. The writers have her, quite correctly, showing horrific capillary-level rupturing. Black eyes, bleeding in the whites of her eyes. BUT. They also showed her (for drama, of course) screaming as she jumps into the vacuum. And she still has lungs at the other end.

Your lungs are extremely fragile, and designed to have positive pressure inside. If you jump into vacuum with your mouth open, expect to have massive bleeding and trauma that will probably result in your drowning in your own blood. You can survive bloodshot eyes, but lungs must be in working condition. And I really think someone who grew up her entire life dealing with vacuum and outer space would know that...

The explosive decompression dodge was due to overthinking, and comparing vacuum to deep sea diving. Only the difference between sea level and the depths of interstellar space is .... one atmosphere of pressure. At ~300 feet of water, you get 10 atmospheres of pressure which is QUITE a different matter and not to be trifled with. Your skin can handle a change of one atmosphere quite well.

The freezing thing is also overthinking, or not understanding what "temperature" is. Someone probably read the "temperature" of helium atoms in interstellar space is around 3 Kelvin or so, which is Pretty Damn Cold. And it is true, your average He atom is not very excited out there. However, your average He atom is also pretty lonely since there might only be five of them in a cubic meter. It's called vacuum for a reason, folks.

Perception of temperature has to do with heat flow, for humans. If a surface is at a higher temperature than your body, it feels hot. If colder, you'll feel cold. But that is a property of matter and there isn't anything to contact out there in space. And what is it that us Earth-humans use to keep cold things cold and hot things hot? A Thermos, also known as a "vacuum flask". Because it works by having a little contained vacuum to stuff things inside. And the average human body, alive or recently deceased, has a LOT of latent heat. So no instant freezing in space, sorry.