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At the end of S02E08 of the TV show "For All Mankind", a cosmonaut is shot on the moon and a fire erupts within his suit.

enter image description here

My understanding is that the pressure of pure oxygen within a spacesuit is 4.3 psi - just a little bit higher than the partial pressure of oxygen at sea-level on Earth (3.1 psi). The main difference is the absence of nitrogen. So while the space suit may be a pure oxygen environment, the concentration of oxygen is similar to a 20/80 oxygen/nitrogen environment at a pressure of one earth atmosphere. Therefore, one would expect that it would be only around 1.39 times more flammable.

The interior of Apollo 1, on the other hand, was pure oxygen at 16.7 psi, a bit higher than sea-level pressure of 14.7 psi. Thus the partial pressure of oxygen inside Apollo 1 was 5.39 times higher than the partial pressure of oxygen in Earth's atmosphere at sea-level.

Assuming that somehow a spark inside the suit initiates combustion, is it plausible that a fire could rapidly break out inside a shuttle-era Russian space suit?

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    $\begingroup$ the alternate-history Soviet lunar surface suits might not have the same atmosphere as the shuttle / ISS EVA suits. Kudos for a reference that refers to the "space station era" as being in the future though $\endgroup$
    – Erin Anne
    Feb 14 at 19:27
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    $\begingroup$ should this really be tagged sokol-spacesuit? Isn't that the Soyuz IVA suit? $\endgroup$
    – Erin Anne
    Feb 14 at 23:23
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    $\begingroup$ Information about flammability versus oxygen pressure and concentration: ntrs.nasa.gov/api/citations/20160004937/downloads/… $\endgroup$
    – bobflux
    Feb 15 at 12:48
  • $\begingroup$ @bobflux NASA presentation is a good find! Worthy of being developed into a full answer. $\endgroup$
    – phil1008
    Feb 15 at 19:14
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    $\begingroup$ @phil1008 I'm passing the hot potato to someone else XD $\endgroup$
    – bobflux
    Feb 15 at 19:53

2 Answers 2

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Yes, because a deadly fire has started within a spacesuit. Fortunately no one was inhabiting it at the time (although a nearby person was injured)

burned-out space suit

In 1980 a Shuttle EMU being tested erupted in flames in a JSC lab. The fire started in the secondary oxygen pack (SOP) regulator. No single cause was determined, but all the probable causes were fixed.

There are multiple potential causes for this event, among them are adiabatic compression heating of the Silastic 675 o-seals [8], particle impact ignition of a dead-end aluminum passage [9], adiabatic compression heating of kindling chain contaminants in the dead end passage or compression heating or rupture of a thin aluminum section in the dead-ended passage. Many of the procedures and processes and supporting data that is taken as a standard today came from the study and corrective action from this event. The SOP regulator was completely redesigned:

  • dead-end passages were removed
  • the body was changed from aluminum to monel (non-flammable under these operating pressures)
  • the fast acting upstream shut-off valve was removed (shut-off accomplished via 2nd stage regulator lock-up)
  • many other more subtle changes were made

Source: Shuttle/ISS EMU Failure History and the Impact on Advanced EMU Portable Life Support System (PLSS) Design (see paper for references cited in the quote)

I haven't found the failure investigation report or a document describing the test objectives, but in this video presentation (part of the JSC Spacesuit Knowledge Capture Series) a person who was present at the fire describes the test (starting about 11:30 into the video).

According to the narrative, the suit was pressurized to 4.3 psi above ambient. The objective of the test was to check out the SOP (the SOP is intended to be an emergency, get-you-back-to-the-airlock oxygen supply), so the test would have activated the SOP and then initiated a simulated leak. The fire started when the SOP was activated.

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    $\begingroup$ @phil1008 definition of "deadly": causing or able to cause death - Oxford $\endgroup$ Feb 15 at 13:10
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    $\begingroup$ @phil1008 I don't have any knowledge of space suits in particular but I can tell you that there's no way to tell when all the design flaws are addressed because there can be - and probably are - flaws you don't know about. For the particulars of the TV show, it is plausible that the bullet pierced the SOP regulator and cause some electrical short or other malfunction that led to a fire. I don't know how rapid is rapid enough, but my ignorant self would put it in plausible territory. All my engineering knowledge is ground-based so I would defer to Organic Marble with a space suit profile pic. $\endgroup$ Feb 15 at 15:53
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    $\begingroup$ @OrganicMarble as much as I love SpaceX and their software-oriented approach to spaceflight, I'm afraid we'll end up with an Apollo 1 or something like it at some point. Some times you do have to "waste" time. $\endgroup$ Feb 15 at 16:56
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    $\begingroup$ @phil1008 I don't understand how you don't see this as an infinitely-better and more-fact-supported version of the self-answer you wrote to the question and then deleted. You speculated about the gunshot or the fall causing damage to an oxygen regulator then causing a fire. Organic Marble is saying a suit fire was caused by oxygen regulator issues, with references and pictures. How much more is he supposed to do with a fictional Soviet suit on a not-very-good TV show? $\endgroup$
    – Erin Anne
    Feb 15 at 20:27
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    $\begingroup$ Using real life to show that not only is this possible but it happened? Don't understand why the OP doesn't like this answer...Admittedly this real life example doesn't know why the fire started.. Just a bunch of what ifs... But thats real life for you... Very seldom are the definite answers. $\endgroup$
    – Questor
    Feb 15 at 21:20
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A link to a NASA presentation in a comment from @bobflux provided some very useful information that I think answers this question.

The presentation examines the correlation between the partial pressure of oxygen and the flammability of materials. In other words, is flammability predominantly a function of oxidizer availability, or is there more to it?

The answer is that there is more to it. Flame spread rate testing (Olson and Miller) found that flame spread rate increased with higher $O_2$% despite $O_2$ partial pressure remaining constant.

Burn Rates (Yang, Hamins, and Donneley) found that burn rates increased significantly as $O_2$% was increased (19.9-30 $O_2$%). However, little effect was observed with increased pressures from 50.0–150 kPa (7.25–21.75 psia). So, if a research team attempted to study this effect without using a vacuum chamber, and then extrapolated their findings to sub-one-atm pressures, they might draw incorrect conclusions.

Keeping in mind that the report set out to discover if, from a flammability perspective...

30% $O_2$, 10.2 psi (3.1pp) == 100% $O_2$, 3.1psi (3.1pp),

...the report concludes that the partial pressure of oxygen equivalency does not represent flammability equivalency. Oxygen Concentration % is the primary driver for flammability despite equivalent partial pressure.

So if you start with an earth-like atmosphere and then remove the $N_2$ and Argon from the suit, leaving just the oxygen, this will make the materials inside the suit more flammable.

If the Russian engineers who designed the suit (in the alternate space-race history of "For All Mankind") did not know this, and incorrectly assumed that oxygen equivalency represents flammability equivalency, then might have tested their suits' flammability in an earth-like atmosphere.

They could have incorrectly concluded that the materials they used inside the suits were safe, when in fact they were quite flammable.

At this point, I'd like to take my hat off to the writers of "For All Mankind'. Nice job on getting the technical details right!

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    $\begingroup$ Um, I'm pretty sure the Soviets knew things in an O2 atmosphere are flammable en.wikipedia.org/wiki/Valentin_Bondarenko $\endgroup$ Mar 10 at 23:55
  • $\begingroup$ The article also says that they covered up the story and even airbrushed the astronaut's image out of photos. So, possible that the accident would not have informed the design of the suit. A similar story happened around Chornobyl's fuel rods if I recall. Both demonstrate poor information sharing in the Soviet political system. $\endgroup$
    – phil1008
    Mar 11 at 5:46
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    $\begingroup$ It was covered up outside their space program. $\endgroup$ Mar 11 at 12:36
  • $\begingroup$ Well, if we assume that the suit designers would have known about the incident despite the public cover-up, then perhaps the answer to the question should be "No, it is not plausible that the Soviets would have put a suit into service that would have led to the fire seen in the TV show." $\endgroup$
    – phil1008
    Mar 11 at 15:29

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