Timeline for How will the Polaris Dawn cabin pressure and oxygen partial pressure dovetail with that of their EVA suits? (100% oxygen?)
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 1 at 5:38 | history | edited | TrySCE2AUX | CC BY-SA 4.0 |
Marked the part about fire hazard as hogwash
|
| Sep 30 at 13:16 | comment | added | Steve Pemberton | I have in the past seen statements that flame propagation in zero g is very slow because of the lack of convection, greatly reducing the risk (and was one of the reasons why it was allowed in Apollo missions after the Apollo 1 accident). However I rarely if ever see that mentioned in discussions about the risk of high oxygen concentration in space. Did you come across mention of this in any of your research? | |
| Sep 12 at 13:32 | comment | added | Yakk | "Fire hazard is a function of Partial Pressure." - false. core.ac.uk/download/pdf/42700768.pdf - the non-O2 in the air act as a kind of "insulation" or "buffer". With a pure O2 atmosphere (even at low pressure) the heat has fewer ways to escape without ignition. This is a common error, but you shouldn't spread it. | |
| S Sep 12 at 5:02 | history | suggested | manassehkatz-Moving 2 Codidact | CC BY-SA 4.0 |
correct spelling
|
| Sep 12 at 4:42 | review | Suggested edits | |||
| S Sep 12 at 5:02 | |||||
| Sep 11 at 12:28 | comment | added | Organic Marble | Yeah, I just skimmed it, but on shuttle there was a 28.5% O2 flammability limit, and they do mention an O2 concentration limit. | |
| Sep 11 at 12:06 | comment | added | TrySCE2AUX | @OrganicMarble wow... that linked presentation totally contradicts wht I said about flammability and partial pressure... #@*&~.. | |
| Sep 11 at 12:03 | comment | added | TrySCE2AUX | @OrganicMarble Yes, I'm making it sound easier than it is, for sure. I'm not sure if they have a gas separator in the system that allows them to selectively get rid of N2 or O2 if required or if they just vent cabin atmosphere to space and replenish only oxygen while lowering the pressure. That's a really interesting question! | |
| Sep 11 at 12:00 | comment | added | TrySCE2AUX | @OrganicMarble I had a number of 0.4 bar ppO2 in my head for a kind of point where flammability becomes a concern. But this for sure depends a lot on the materials used. Maybe this helps? "Oxygen Partial Pressure and Oxygen Concentration Flammability: Can They Be Correlated?" ntrs.nasa.gov/api/citations/20160004937/downloads/… (have only skimmed over it right now) | |
| Sep 11 at 11:58 | comment | added | Organic Marble | Also, do they actually get to 100% O2 in the cabin during the depress? How do they selectively get rid of the N2? Again, I think it's more complicated than you're making it sound. On shuttle they had to vent the cabin down, but stop and add N2 if they approached the flammability limit, or stop and add O2 if the ppO2 got too low, then start venting down again. | |
| Sep 11 at 11:57 | history | edited | TrySCE2AUX | CC BY-SA 4.0 |
added the last paragraph
|
| Sep 11 at 11:53 | comment | added | Organic Marble | During the shuttle prebreathes at 10.2 psi there were major flammability concerns and the ppO2 had to be strictly controlled. (They never got to pure O2 in the cabin). I'll have to dig out my stuff on that, but I don't think you can just dismiss it. | |
| Sep 11 at 11:48 | comment | added | TrySCE2AUX | Oh. Good point! Sure, the pressure inside the suit will be the same as the outside pressure as long as the outside pressure is above 5.1 psi. Only when they reduce the preeure in the vessel down to basically zero, the suit will stop at 5.1 psi and keep that pressure. I'll update the answer to address that part. | |
| Sep 11 at 11:45 | comment | added | uhoh | I don't think the suits are rigid negative pressure vessels, are they? If the cabin is 8.65 psi, the inside of the suit will also have to be at least 8.65 psi as well, no? | |
| Sep 11 at 11:42 | history | answered | TrySCE2AUX | CC BY-SA 4.0 |