Old school: the Apollo O2 tank

[Carlobrand]

The Apollo program used a spherical inconel O2 tank, double walled, 67.4cm outer diameter, 63.66 cm inner diameter, with the space between in vacuum and packed with insulating materials because the O2 was kept in a "supercritical" (semi-liquid, semi-gas) state at about 297 degrees below zero. The tank itself weighed 35.8 kilograms empty and contained 145 kg of oxygen, about 2/3 for the hydrogen fuel cells for power during the trip and a third for the astronauts, presumably some for breathing and some for keeping the pressure up in the command module; command module was 5.9 cubic meters without astronauts in it, so there was oxygen available to refill it if they decided to go on a spacewalk or something . There were two of these tanks until Apollo 13; after that they put one on the other side of the service module as a backup in case the accident repeated.

So, here's this 160 liter cryogenic tank, enough oxygen for one person for - what - 2 to 5 months depending on exertion? O2 of course is not the only issue for life support; there's also scrubbing CO2 and maintaining habitable temperatures. Still, if you need backup for your life support system, or say you want to do a cheap and dirty small craft cabin instead of a full stateroom, LO2 would seem to fit the bill nicely.

 

[Commander Truestar]

Sadly,
We only learned years later the Russians had also learned they had to post a "no sparks or flames" sign if they used LO2.
And, if it were not for the cold war, they might have told us that before the Apollo 1 disaster.

Of course, a NASA investigation told us much the same thing as the Challenger report. The accident was due, in large part, to arrogance.

So, yes, LO2 can be used if you are not foolish enough to believe you were in absolute control.
Especially in the Traveller based universes, where space travel is an every day thing, and no one is nearly as cautious as Grissom, White and Chaffee.

We didn't ask "What could go wrong" and we are much the sadder for it.
Not just the lost astronauts.....but the lost dreams as we scaled back and gave up on some programs.

A song I know begins with the worlds of Maud Muller, "Of all the words of tongue or pen, the saddest are these: It might have been!'"

 

[Carlobrand]

Sadly,
We only learned years later the Russians had also learned they had to post a "no sparks or flames" sign if they used LO2.
And, if it were not for the cold war, they might have told us that before the Apollo 1 disaster.

Of course, a NASA investigation told us much the same thing as the Challenger report. The accident was due, in large part, to arrogance.

So, yes, LO2 can be used if you are not foolish enough to believe you were in absolute control.
Especially in the Traveller based universes, where space travel is an every day thing, and no one is nearly as cautious as Grissom, White and Chaffee.

We didn't ask "What could go wrong" and we are much the sadder for it.
Not just the lost astronauts.....but the lost dreams as we scaled back and gave up on some programs.

A song I know begins with the worlds of Maud Muller, "Of all the words of tongue or pen, the saddest are these: It might have been!'"

A component of the Apollo 1 disaster was the decision to run the test with the cabin pressurized to 2 psi above standard sea level pressure, presumably to keep normal atmosphere out. Since the command module was designed to deliver oxygen to maintain cabin pressure, they pressurized the cabin with pure oxygen, but that was like 3 or 4 times the pressure they'd be using during normal flight conditions. It hadn't occurred to anyone to test the command module for fire risk under pure O2 at that pressure, apparently because they didn't realize the effect that O2 had at that pressure, though there'd been previous incidents in other tests showing the dangers of pure oxygen at sea-level-equivalent pressures. I'd say ignorance and a failure to communicate the details of those previous incidents was at least as great a cause as arrogance.

The challenge here is not a pure O2 atmosphere at normal pressure. The challenge here is delivering pure O2 into an O2/N2 atmosphere at a rate that wouldn't allow O2 levels to fall below safe levels OR rise to dangerous levels since, apart from the fire hazard, people don't do too well if there's too much O2 at standard pressure. It's the same challenge faced by the usual life support system, so clearly it's one they know how to manage. A pure O2 atmosphere at a pressure around 4 psi might be an idea, but transitioning from normal atmosphere to a low pressure O2 atmosphere risks the bends.

 

[Commander Truestar]

@Carlobrand
This comes from the official NASA documents:

"Because the cabin had been filled with a pure oxygen atmosphere at normal pressure for the test and there had been many hours for the oxygen to permeate all the material in the cabin, the fire spread rapidly and the astronauts had no chance to get the hatch open. Nearby technicians tried to get to the hatch but were repeatedly driven back by the heat and smoke. By the time they succeeded in getting the hatch open roughly 5 minutes after the fire started the astronauts had already perished, probably within the first 30 seconds, due to smoke inhalation and burns."

Please note the section that reads "with a pure oxygen atmosphere at normal pressure for the test"

Ironically, I had my portal open because I am tracking Starliner, so I could quickly grab those docs..

 

[kilemall]

I think Starliner is gonna burn up.

 

[whartung]

with a pure oxygen atmosphere at normal pressure for the test

Doesn't mean it wasn't over pressurized. It was. It was over pressurized for the test. They normally over pressurized the cabin to drive out the nitrogen based atmosphere, then, before launch, they bled off the pressure.

Apollo 1 was pressurized too much, for too long, and that was partly responsible for fire.

Apollo 1 did not have explosive bolts on the hatch (which opened inward) because of what happened to Grissom on Mercury. Later investigation found that, indeed, the bolts "just blew" (perhaps to static charge from the helicopter).

All of these different usually minor things conspired to exacerbate the fire and frustrate the rescue attempt.

 

[Condottiere]

 

[Grav_Moped]

On the other hand, merely breaking things is not proof that you're moving fast enough.

 

[Commander Truestar]

Doesn't mean it wasn't over pressurized. It was. It was over pressurized for the test. They normally over pressurized the cabin to drive out the nitrogen based atmosphere, then, before launch, they bled off the pressure.

Apollo 1 was pressurized too much, for too long, and that was partly responsible for fire.

Apollo 1 did not have explosive bolts on the hatch (which opened inward) because of what happened to Grissom on Mercury. Later investigation found that, indeed, the bolts "just blew" (perhaps to static charge from the helicopter).

All of these different usually minor things conspired to exacerbate the fire and frustrate the rescue attempt.

I would think "at normal pressure" would mean it was not over-pressurized.

As for "Apollo 1 was pressurized too much, for too long,", Yes. Oxygen saturation was a key item mentioned in the report.

As for the bolts on Apollo 1, there is no mention of those being an issue except as a conspiracy theory

At the same time, the change in the hatch was also pointed to as a key delay in getting the hatch opened.
BY the time they did reach the capsule and get the hatch open, the report was firm that all three crewmen were already dead.

 

[aramis]

I would think "at normal pressure" would mean it was not over-pressurized.

As for "Apollo 1 was pressurized too much, for too long,", Yes. Oxygen saturation was a key item mentioned in the report.

As for the bolts on Apollo 1, there is no mention of those being an issue except as a conspiracy theory

At the same time, the change in the hatch was also pointed to as a key delay in getting the hatch opened.
BY the time they did reach the capsule and get the hatch open, the report was firm that all three crewmen were already dead.

They overpressured to about 16.7 PSI (vs 14.7 PSI Std Atm), then held there to see if it leaked. For launch, it would have reduced slowly to 5 PSI. Even so, the atmosphere wouldn't have been more tha 90% O2... tho that leaves a full 14.7 PSI Equivalent PPO2.

It was just something they didn't actually realize the risks of. (Tho', if they'd asked USN welders, they might have had a clue.)
Also, the human comfort zone for PPO2 is up to 1.4 bar in dense mix... about 20.5 PSI PPO2 max, and about 1.75 PSI PPO2 minimum sustained, and short durations to about 1 PSI PPO2. They were thinking physiological risks, not fire.

Plus, it was saturation into the capsule's systems. It takes time for infiltration of oxygen into the electronics; the overpressure doesn't help, as it forces an enriched atmosphere in.

It was a blind spot, one whch LtCol Grissom, LtCol White, and LtCdr Chaffee taught us with their lives.

As for the bolts issue? look up Col Grissom's Mercury flight. Specifically the landing. A misfire of the cabin door explosive bolts is why his capsule is in the bottom of the pacific... and not a museum... until its 1999 recovery. While he was accused of triggering them, that's deemed unlikely by NASA, then and now, and he denied it vehemently. So there WAS a real discomfort with explosive bolts, especially for Grissom. (The recovery allowed NASA to verify he'd not triggered them via the switches.)

Keep in mind also: The astronauts had input on capsule design. Distrust of explosive bolts was shared amongst several Apollo and Gemini astronauts. No conspiracy, just design by committee, and a bad outcome none wanted repeated. The risk of losing another crew far outweighed the risk of losing a capsule. (Tho' note: Grissom had claimed he had trouble exiting the sinking Liberty Bell 7, and the frogmen were able to extract him before she sank.)

 

[whartung]

I would think "at normal pressure" would mean it was not over-pressurized.

You misquoted.

"at normal pressure for the test". The test required it to be over pressurized.