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We really still sure this whole decompression sickness thing was just a “simulation”? https://www.reuters.com/technology/space/nasa-accidentally-broadcasts-sim

by leoh 2y ago

We really still sure this whole decompression sickness thing was just a “simulation”? https://www.reuters.com/technology/space/nasa-accidentally-broadcasts-simulation-distressed-astronauts-space-station-2024-06-13/ https://www.reuters.com/technology/space/nasa-accidentally-b...

hehdhdjehehegwv 2y ago
I read that article earlier, but it didn’t mention Boeing so I wasn’t questioning it. But where Boeing goes, bad things follow.
everforward 2y ago
I don't think a "leak" would cause decompression sickness. Decompression sickness is caused by bubbles forming when pressure decreases too quickly for the body to expel now-excess nitrogen. A slow, gradual decrease would provide plenty of time to expel excess nitrogen. A leak in a pressure vessel is basically how deep saturation divers re-acclimate to standard pressure, and they're making a much, much larger change in pressure (maximum of 14.5 psi delta on the ISS, ~429.06 for a saturation diver at 1000 ft). It's really a delta P of 10 psi though, since the American space suits are 4.5 psi. There's not really much point in talking about decompression sickness without a space suit; they'd die of lack of O2 or exposure even without DCS. Current recommendations for space walks are a 4 hour denitrogenation period breathing 100% oxygen, and that's pretty cautious. That's based on the denitrogenation rate of the slowest tissues; it could likely be done significantly faster without presenting dramatically increased risks of DCS, and especially so if you only need to avoid type 2 DCS where the bubbles present a risk of dying.
- ethbr1 2y ago
  Also, this is helium from the propulsion system. >> Helium is used in the spacecraft’s thruster systems to allow the thrusters to fire without being combustible or toxic. I'm assuming it's used to backfill tanks as they're emptied?
  - CableNinja 2y ago
    Theres 2 use cases: 1) To keep the fuel/oxidizer pressurized and liquid (by pressure) as the tanks content empties. 2) for RCS thrust, as a cold gas thruster.

by leoh 2y ago

hehdhdjehehegwv 2y ago

I read that article earlier, but it didn’t mention Boeing so I wasn’t questioning it. But where Boeing goes, bad things follow.

everforward 2y ago

I don't think a "leak" would cause decompression sickness. Decompression sickness is caused by bubbles forming when pressure decreases too quickly for the body to expel now-excess nitrogen. A slow, gradual decrease would provide plenty of time to expel excess nitrogen. A leak in a pressure vessel is basically how deep saturation divers re-acclimate to standard pressure, and they're making a much, much larger change in pressure (maximum of 14.5 psi delta on the ISS, ~429.06 for a saturation diver at 1000 ft). It's really a delta P of 10 psi though, since the American space suits are 4.5 psi. There's not really much point in talking about decompression sickness without a space suit; they'd die of lack of O2 or exposure even without DCS. Current recommendations for space walks are a 4 hour denitrogenation period breathing 100% oxygen, and that's pretty cautious. That's based on the denitrogenation rate of the slowest tissues; it could likely be done significantly faster without presenting dramatically increased risks of DCS, and especially so if you only need to avoid type 2 DCS where the bubbles present a risk of dying.

ethbr1 2y ago
Also, this is helium from the propulsion system. >> Helium is used in the spacecraft’s thruster systems to allow the thrusters to fire without being combustible or toxic. I'm assuming it's used to backfill tanks as they're emptied?
- CableNinja 2y ago
  Theres 2 use cases: 1) To keep the fuel/oxidizer pressurized and liquid (by pressure) as the tanks content empties. 2) for RCS thrust, as a cold gas thruster.