In the future, space travel is common, so common, in fact, that commercial transport is available to most people, like air travel is to us.

As a passenger on a vessel of Galactic Spacelines, half way to your destination, you hear this announcement:

"Attention passengers, this is captain speaking. Due to an emergency, we will be experiencing a loss of pressure in the cabin. Safety equipment is being deployed, please use it in accordance with pre-flight orientation. Ask a steward if you need assistance."

My question is this: What safety equipment is deployed for most of the passengers to survive this event until it ends? (I imagine that at the least this will be airtight oxygen masks for each passenger that completely cover the face, and possibly "space blankets" or clothes to help them retain heat.)

For your choice of equipment, please also answer the following:

  • The cabin may be able to retain some aspects of normal parameters, such as partial pressure. Are there limits to the situations your equipment can handle, such as a minimum pressure under which the safety equipment becomes useless?
  • How much medical attention will the passengers need after this event, using your equipment?

Other notes:

  • Since this is about survival, that is the number one priority; comfort is less important.
  • Also, to reduce complexity and chance for user error, the Spaceline is (ahem) interested in keeping costs as low as possible.
  • You can set some conditions on the cabin, like what pressure and temperature it is reduced to.
  • This question is about a (semi) planned loss in pressure, not a sudden drop to hard vacuum, since that would be very difficult to survive, though solutions that can handle that are welcome. The loss in pressure to emergency levels will be gradual, over no less than 30 seconds.
  • Assume that the ship has enough resources to run emergency equipment until the event ends. (air, energy, etc.)
  • Assume that within 24 hours one of the following happens:
    • The ship has made contact and rescue comes
    • The ship continues and arrives at the destination
    • Repairs can be made to restore normal conditions to the cabin
  • $\begingroup$ And I retracted my close vote. $\endgroup$
    – Mołot
    May 9, 2018 at 8:56
  • $\begingroup$ What research have you done regarding the kinds of things that humans need to survive in space? Apollo 13 is just this kind of scenario (the Command Module was even called a life boat), and is really well documented. $\endgroup$
    – RonJohn
    May 9, 2018 at 12:45
  • $\begingroup$ Yeah, I've examined this sort of thing in the past, and know a bit about decompression, heat problems, and the other dangers of space. But I was curious about what kind of solutions an airline... er, spaceline would want to (or be legally required to) implement to protect it's passengers in the event of emergency. $\endgroup$
    – jpfx1342
    May 9, 2018 at 21:15

4 Answers 4


I'm going to address this question in two parts; the first relates to cabin pressure in the main on a spaceship (because it's pertinent), then I'll get to safety equipment.

Cabin Pressure on Space Vessels

Modern planes are pressurised because of the altitude at which they fly, but what may not be obvious to most people is that they don't pressurise it to 1 ATM (Sea Level Pressure). There's a simple reason for that; the pressure differential would be higher between the inside and the outside, meaning that your plane must be stronger (read as heavier). Also, explosive decompressions (something punching a hole in the side of the plane) would be much more catastrophic if that pressure differential was higher.

If you look at the Apollo missions, you see that they reduced the pressure even further, to the point of having 100% O2 atmosphere inside the modules. Oxygen requirements for humans sit in a band on a spectrum where too little or too much is a bad thing. Pure O2 at 1 ATM will quickly cause oxygen toxicity, and burn out lungs, the throat and even eyes. Too little, and you suffocate. We measure the O2 requirements in terms of partial pressure (PP) because we've found that it's not the ratio of O2 that causes the problem; it's the volume. So, humans can normally operate in around the 0.18 to 0.3 PP of O2 range with no problems.

So; the Apollo modules were pressurised to around 0.3 ATMs and filled with pure O2, and the astronauts were fine.

(I should point out here that no long term tests have been done on this atmospheric model, and long term exposure may be hazardous; we just don't know. But, for the purposes of this answer, we'll assume this is fine for the average spaceship journey)

This of course meant that NASA could build modules with less weight and strength (didn't have to hold 1 ATM of pressure against the vacuum of space) and also, they didn't have to launch all that N2 with the ship as well. This solution meant the astronauts took far less atmosphere with them, as well as lighter ships.

It also means that we seem to be able to withstand around 0.3 ATM alright, provided the atmosphere is pure O2. I don't know what happens if you drop below that, but given NASA didn't (and they researched the daylights out of this) I'd guess it's not healthy even in the short term.

Emergency Equipment

So; your ship is probably going to be running on around 0.3 ATM for the same reason, and going to be running with a pure O2 environment. As for safety equipment, it's going to look a lot like a modern space suit for exactly the same reason; if we could survive with less weight, we wouldn't take that weight up into space in the first place.

Ideally, the one thing you don't need is the bulky backpack and life support. Let's assume that your cabin has vented and you're in vacuum. All the passengers and crew are in their safety suits, they're not going to be planning any EVAs so they don't need to carry their own air supply, propulsion and monitoring around. You can connect them into a central ship's supply of O2 and power by simply plugging a hose into a wall outlet. The passengers in particular just sit in their allocated spaces, plugged into the walls for power and air, waiting for the problem to be resolved.

Because they're not expected to help, you don't even have to make the 'suits' real suits. Give them the top and bottom halves of heavy bags with a ring connector - that way you don't have to have the suit custom fitted, there's only one connector so not all those seals where they might get one wrong, there's no way they can walk anywhere, no arms to touch anything, and no helmet (better off if they can't see what's happening. Include an internal touch screen entertainment system for them and you've taken them out of the equation insofar as they cant' get in the way of the repair crew, and you can communicate with them about when it's safe to come out.

All in all, this is a reusable, one size fits all, simple way to keep people safe and it's more of a 'pod' than a 'suit'. Given your parameters, it should also be enough to get them through the crisis period.

  • 1
    $\begingroup$ I love the "bags" idea! It's modular, cheap, solves lots of problems, and best of all: it's hilarious! I actually had already heard about aircraft and spacecraft being at lower than atmospheric pressure normally, but totally forgot about it when I was thinking about the question. :) $\endgroup$
    – jpfx1342
    May 9, 2018 at 6:03
  • 2
    $\begingroup$ To take the bag idea one step further: if you have gaps between seats then you can put the ring seal on the floor, and the emergency bag can be deployed from the ceiling and fastened to the floor. No need for passengers to leave their seats at all! $\endgroup$
    – Joe Bloggs
    May 9, 2018 at 7:31
  • 1
    $\begingroup$ One addition to this excellent answer: while we are ok with varying pressures, a sudden pressure reduction is potentially lethal. (that´s why deep divers )have to stop on the way up. Slowly lowering the pressure after start and than keeping that same pressure inside of the "safty bags" is therfore crucial. $\endgroup$
    – Daniel
    May 9, 2018 at 8:04
  • 1
    $\begingroup$ NASA did in fact design a rescue ball for the shuttle, though it never flew. $\endgroup$
    – user71659
    May 10, 2018 at 4:09

As already stated in the other answers, you´d need some device to keep some pressured atmosphere. I like the Idea of having some inflatable bag, but I think an even better way would be to make passengers compartments that are easily sealed off.


  • Can automatically be deployed for all passengers, including children, disabled and elderly.
  • There are still several people inside every compartment, so they can help each other.
  • Less connections for life-support, as you only need to supply every compartment, not every bag.
  • Faster application. You´d have 90 seconds max. after decompression occurs. It could also be a safety procedure to make sure there are at least two people/one adult in every occupied compartment at all times (like with emergency-exit seats nowadays)


  • Possibly higher weight (but you save the bag and some life-support connections)
  • If you have a pressure-loss in your cabin, you have a problem. Evacuation procedures of individual cabins would have to be in place.

Here is a little sketch with that principle applied to traditional Airline seating. The seal, in this case, is a roll-down shutter, located where the hand-luggage compartment is normally located. Could also devise something that comes up from the floor.

enter image description here

  • $\begingroup$ Honestly, a well designed spacecraft would probably be as compartmentalized as possible, so this is a pretty good idea. For style, you could even make the compartments look like old style train compartments. :) $\endgroup$
    – jpfx1342
    May 9, 2018 at 21:12

Inflatable hamster balls.

Pass out backpack-sized survival kits that contain some CO$_2$ scrubbing chemicals that will also produce O$_2$. Since we're working at a low-pressure atmosphere here, you don't need to worry about oxygen toxicity and can simply scrub all the carbon dioxide and have them breathe pure oxygen.

They'd be inflated to some degree initially, after which exhalation should balance inhalation and the pressure should remain constant.

The mental image I have is something like a zorb:

enter image description here

Honestly, if Galactic Spacelines plays this right, the passengers wouldn't even need to know that there's an emergency decompression:

*crschk* Attention passengers, this is your captain speaking. Do you know what time it is? It's mandatory bubble time!!! Please proceed to the nearest muster station to receive your personal hamster ball. We'll get started with a variety of games such as soccer, obstacle courses, and water skiing. Thank you for participating in mandatory bubble time, and thank you for flying Galactic Spacelines!


The issues which come with decompression are two:

  1. too low oxygen pressure for the brain to work properly
  2. too low pressure to prevent your body fluids to boil

For 1 one can follow the path of commercial airlines today: they keep a cabin pressure equivalent to few thousands meter above the sea level (3000 if I remember correctly) and in the event of a sudden loss of pressure the oxygen masks provide oxygen only for the time needed to reach that altitude from the original flight altitude, after which one is supposed to be able to breath decently.

For 2 things become more tricky: boiling saliva in your mouth is all but funny, also your blood expanding in your body will be pretty unpleasant and, last but not least, your lungs are not designed to operate in a vacuum.

The safest direction to me seems to have an air tight "bag" around the seat, keeping a pressure equivalent to 3000 m on Earth, with a dedicated oxygen supply.

  • $\begingroup$ there is a lot of conflicting opinions around on whether body fluids would actually boil in space, mainly because there have been no experiments carried out, for obvious reasons. The pro-boil camp work on the assumption that liquid boiling points lower with atmospheric pressure, while the anti-boil camp say the act of boiling uses energy, which would be body heat, so you would end up dying from losing too much bodyheat. $\endgroup$
    – Pinback
    May 9, 2018 at 13:41
  • $\begingroup$ @Pinback, I have read about a pilot who was left exposed to vacuum by an accident: he said that he felt his saliva boiling in his mouth, and his right hand (he had a leak in his right glove) was swollen to twice the original size. $\endgroup$
    – L.Dutch
    May 9, 2018 at 14:04
  • $\begingroup$ do you have a link? I'm not saying I doubt your word - rather I'd like to read the account for myself, I'd never come across the topic until I read your comment so I haven't really got a strong opinion one way or another $\endgroup$
    – Pinback
    May 9, 2018 at 20:30
  • $\begingroup$ @Pinback, check space.stackexchange.com/a/126 and en.wikipedia.org/wiki/Joseph_Kittinger $\endgroup$
    – L.Dutch
    May 10, 2018 at 2:58
  • $\begingroup$ Wikipedia has a good section on it: The human body can briefly survive exposure to the hard vacuum of space unprotected,[2] despite contrary depictions in some popular science fiction. Human skin does not need to be protected from vacuum and is gas-tight by itself. Human flesh expands to about twice its size in such conditions, giving the visual effect of a body builder rather than an overfilled balloon. This can be counteracted through mechanical counter-pressure from a suitably designed garment. $\endgroup$
    – Cort Ammon
    May 10, 2018 at 3:05

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