I'm designing an environment suit for humans to wear while interacting with a benevolent alien species while in alien space. Here's my question:

How much solid oxygen (by mass and volume) it would take to allow for six hours of comfortable, low-stress breathing by an average-sized human?

These are the constraints that I'm working with:

  • The suit the humans are using needs to be closed at a microscopic level, to prevent cross-contamination. While human and alien life relies on the same fundamental structures, due to an ancient artificial panspermia, contact happened recently enough that neither side has an effective immune booster to protect them from the other's microbiology. Therefore I want a closed-circuit system, like a rebreather, to prevent exhaled oxygen from contaminating the alien atmosphere.

  • The environment suits can maintain one atmosphere of pressure against the human wearing them. One of the constraints on scuba divers is that being under more pressure reduces the amount of time that their air supply can sustain them, so assume that the suits can negate the normal differences in pressure their wearers will be exposed to.

  • I see that the unit of measurement for the pressure δ-phase (orange) oxygen forms at is gigapascals, but the aliens have the ability to store and generate energy on vast scales and with vast precision. However, I'll be happy with answers using any of the stages.

  • An answer that results in an oxygen pack capable of going off like a bomb when breached would be preferred.

Also if there's an easier way to supply breathable atmosphere for long periods than just condensing oxygen more, given the assumption of cheap, bulk, energy, then please let me know.

That's my first question here on worldbuilding. If I've made any mistakes with form, or if something needs to be clarified, let me know.

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    $\begingroup$ Solid oxygen forms at about 9 GPa, which is almost 90 000 atmospheres. We would heed a very strong container for this kind of pressure. $\endgroup$
    – Alexander
    Commented Oct 24, 2017 at 18:45
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    $\begingroup$ Emm but what is the actual question? I'm bit lost. $\endgroup$
    – Mołot
    Commented Oct 24, 2017 at 18:48
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    $\begingroup$ @Mołot brings up a good point. Your question doesn't contain a single question mark. $\endgroup$
    – sphennings
    Commented Oct 24, 2017 at 18:54
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    $\begingroup$ How much solid oxygen by volume and mass would it take for 6 hours of breathing. That is the question. $\endgroup$ Commented Oct 24, 2017 at 19:05
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    $\begingroup$ The majority of the question appears to be answered on physics.se. Humans breathe about 4.75 qubic feet of oxygen per 6 hours. What the Physics.se answer suggests is that there's only a moderate benefit to using metallic oxygen. $\endgroup$
    – JBH
    Commented Oct 24, 2017 at 19:06

3 Answers 3


For a closed circuit system, you would probably not want oxygen, but instead would want Lithium Peroxide, or lithium hydroxide. Both are lightweight compounds that absorb significant volumes of carbon dioxide. What kills a human in a space suit is not oxygen deprivation, but carbon dioxide poisoning. When carbon dioxide is present at >5.0%, a human will die within 4 hours, and the concentration really needs to be kept below 1.5% for proper functioning.

These were the chemicals used in the famous scene in Apollo 13. But the peroxide also generates oxygen, so it would be more useful in your scenario. Alternatively, triple point oxygen is what is normally used for current space missions, because it has the highest mass for the given volume of oxygen, while being able to be siphoned off as a gas.

Using triple point oxygen, and the commonly cited data point that a human uses 550 Liters of oxygen at STP (20 C and 1 atmosphere) per day, we would arrive at a mass of 0.715 kg per day, or about 0.3 kg for 6 hours (with reasonable factor of safety for design).

In terms of Lithium Peroxide, this could be generated with as little as 0.86 kg of the salt, or 400 mL of the salt. Triple point oxygen, with a density of 0.04083 mol/cm^3, or 1.307 kg/L, would need a volume of 0.23 L to hold this much oxygen.

  • 1
    $\begingroup$ This answer is excellent, except that it does not answer the OP's question. "I need to know how much solid oxygen (by mass and volume) it would take to allow for six hours of comfortable, low-stress breathing by an average-sized human." Add the "amount needed" component to your answer and it's perfect. $\endgroup$
    – JBH
    Commented Oct 24, 2017 at 19:59
  • $\begingroup$ @JBH - Fixed. Thanks for the update request. $\endgroup$
    – Mark
    Commented Oct 24, 2017 at 21:41
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    $\begingroup$ As an addition to this excellent answer, I'd point out that that 0.3kg is a very small mass compared to the hardware required to create an operational and safe re-breather, so for all intents and purposes you can ignore the fancy oxygen storage mechanisms, and focus on keeping the weight of the hardware down. $\endgroup$
    – Cort Ammon
    Commented Oct 24, 2017 at 21:56
  • $\begingroup$ Thanks, have some rep! And I'm not worried at all about the hardware. Clarkian Magic (being indistinguishable from a sufficiently advanced technology) takes care of it. :-) $\endgroup$
    – JBH
    Commented Oct 24, 2017 at 22:46
  • $\begingroup$ Can you please give more information about triple point oxygen? Oxygen's triple point is at 54.36 K (−218.79 °C), and as far as I know, oxygen is currently shipped to ISS in non-refrigerated tanks. $\endgroup$
    – Alexander
    Commented Oct 25, 2017 at 0:57

99% Hydrogen peroxide

I am going to assume there is a rebreather apparatus to provide appropriate inert gas and scrub the CO2.

http://www.collegesportsscholarships.com/measure-oxygen-consumption.htm average O2 requirement: assume 250 ml/min We will also assume exhaled O2 (we do not use all we inhale) is recirculated; O2 is not expelled or wasted.

How about this excellent reference on hydrogen peroxide? http://moveonstage.excellencegateway.org.uk/ilr_php/hottopics/pe/l1/docs/res/hydrogen%20peroxide%20strengths.pdf

1 ml of 3% H2O2 evolves 10 ml O2 gas
1 ml of 6% H2O2 evolves 20 ml O2 gas
So 1 ml 99% H2O2 evolves 330 ml O2 gas

6 hours has 360 minutes x 250 = 90,000 ml O2 required 90,000 ml / 330 ml = 272 ml H2O2. That is less than the volume of a can of soda.

Can that be right? Checking against liquid oxygen with an expansion ration of 1:860 https://en.wikipedia.org/wiki/Expansion_ratio 90,000 / 860 = 104 ml.

So why not use liquid or solid oxygen?

1: Liquid or solid oxygen must be supercooled / kept under pressure / both. Hydrogen peroxide can be a liquid at room temperature and pressure.

2: Hydrogen peroxide is very reactive and will terminally oxidize anything organic it contacts. So your peroxide supply could serve double duty as a scrubber (probably on a separate circuit). No germs / viruses / phlegm / pollen / stray hairs will make it through. Your peroxide can sterilize incoming or outgoing exhalations.

3: Blowing up. A problem with the supercooled O2 is that very cold stuff is not that reactive. The (most excellent) Periodic Videos series has a couple of videos showing hot charcoal dropped into a vat of liquid O2. It is neat but it does not blow up. https://www.youtube.com/watch?v=7NXfyCezUFk

Pure hydrogen peroxide can be used (with an oxidizable carbon, like kerosene) as rocket fuel. It will rapidly oxidize anything it touches that is oxidizable, meaning those things will burst into flame. Hydrogen peroxide exposed to light can explosively decompose into oxygen gas and superheated steam (the liberation of O2 being exothermic enough to generate the steam). The expanding hot gases will shower everything around with drops of undecomposed pure H2O2, causing those things to burst into flames. Once there are flames the reaction will intensify. Porous or wettable things soaked with H2O2 do not burn from the outside in, like things doused with gas but from the inside out, as the interior is saturated with oxidizer.

So your catastrophic failure would not be like a bomb going off, but rather like a soda bottle exploding, followed by everything in the vicinity burning like mad. Which in my opinion offers more narrative possibility than just a big explosion and then people crawling through the wreckage commenting on the big explosion that happened.


As far as I can tell and reason,

If a container of solid oxygen were breached with a bolt of plasma, the ensuing reaction would be disappointing. Once breeched the solid O2 would just begin to sublimate as it becomes exposed to the heat from the hole. Even a pressure explosion from the compromised integrity of the container seems fairly tame. This is because solid oxygen is stable. The plasma would need to be hot enough to vaporize a great deal of the oxygen ( that is if you are even being shot with it).

Anyways there are other ways to make explosions. If power is cheap and abundant why not have batteries that drive an artificial photosynthesis like reaction converting co2 into o2. Anything that contains that much charge can surely make for a wonderful explosion. Like the cheap lithium ion phone batteries that have managed to bring down planes only much stronger.


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