191–200 of 283 posts
Earlier quoted context omitted.
I thought it had a pure oxygen atmosphere to prevent the bends? Why is it dangerous?
Apollo I disaster suggests pure oxygen atmospheres are to be avoided.
I found this interesting: NASA RELL (Robotic External Leak Detector) [1]. "NASA’s Robotic External Leak Locator (RELL) is a robotic, remote-controlled tool that helps mission operators detect the location of an external leak and rapidly confirm a successful repair. … Two instruments working in sync give RELL its ammonia-detecting superpowers. … Mass spectrometer & Ion vacuum pressure gauge" [1] (PDF fact sheet from N…
> After multiple inspections and sealant applications, Nasa reported in January that pressure readings suggested a stable configuration had been reached - though there remained uncertainty about whether the leak had truly been sealed or whether air was simply escaping elsewhere. I'm clearly not understanding what they're trying to say here. If _one_ leak was sealed, but the air was "escaping elsewhere", it would stil…
Does someone know if push come to shove, do they have a ready to go escape pod or ship to go back Earth anytime in an emergency? How many backups do they get?
For every human onboard ISS there is always place in the docked spaceship. Exceptions: when spaceships break, replacements are usually sent - like, when Soyuz lost coolant or Starliner was considered too unreliable. While waiting for replacements, those ploblematic spacecrafts still serve as lifeboats, except maybe Crew Dragons can carry more people than those 4 they usually carry...
The contingency for the Starliner astronauts in case of an emergency was to strap them down in the cargo area. Which wouldnt be optimal, but better than certain/likely death onboard the ISS.
Earlier quoted context omitted.
If you count the Soyuz leak, then the Boeing counts too! That was far more serious than anything you listed. Two astronauts stranded for nine months taking the ISIS supplies intended for others. This is after they safely docked, which was considered risky at the time.
You brought it up. I have been talking about structural issues with long term core modules. And that is clearly a Russian issue.
Nothing in the Russian space program in the last few decades have been as dangerous as Boeings little fiasco. Yes, the modules have long term problems, but they're built by the Russians because they have the most experience in space living quarters.
Look at space mission fatalities, the least Soviet/Russian one was in 1971 and that includes the 90s.
Thats 55 years
The US since then has had two shuttle disintegrations, the latest in 2003 when the US gave up launching astronauts for a few decades.
Space is hard.
It's a hot take but I do think the US should be more appreciative of Russia's longstanding contributions to the ISS and other space projects of international cooperation and factor that into sanctions decisions. We do need their help as much as they need ours in space, and the fact that they are still helping us despite our treatment of them speaks volumes about their leaders' character.
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Candles are useful when oxygen has been consumed because of respiration or a fire. They're not useful in a leak. Conservation of mass: if a cubic meter of air escapes, that's 1.25 kg, and you need at least that much in candles. (You actually need 2 kg because the candle isn't solid oxygen) There's ultimately 1.2 t of atmosphere on the ISS. This will also result in a pure oxygen atmosphere, which is dangerous. You nee…
I thought it had a pure oxygen atmosphere to prevent the bends? Why is it dangerous?
Do they have things like Oxygen Candles or can those not be used in space?
Candles are useful when oxygen has been consumed because of respiration or a fire. They're not useful in a leak. Conservation of mass: if a cubic meter of air escapes, that's 1.25 kg, and you need at least that much in candles. (You actually need 2 kg because the candle isn't solid oxygen) There's ultimately 1.2 t of atmosphere on the ISS. This will also result in a pure oxygen atmosphere, which is dangerous. You nee…
1.2t of candles doesn't seem like an unreasonable amount of extra payload if they would really be valuable in an emergency. The ISS weighs 400 tons and a napkin estimate says it has had 1000 tons of resupply missions. The candles have a shelf life of 10+ years.
Earlier quoted context omitted.
Candles are useful when oxygen has been consumed because of respiration or a fire. They're not useful in a leak. Conservation of mass: if a cubic meter of air escapes, that's 1.25 kg, and you need at least that much in candles. (You actually need 2 kg because the candle isn't solid oxygen) There's ultimately 1.2 t of atmosphere on the ISS. This will also result in a pure oxygen atmosphere, which is dangerous. You nee…
I thought it had a pure oxygen atmosphere to prevent the bends? Why is it dangerous?
Why the difference? It's a question of what risks you were most afraid of. Even today, every single spacewalk is done at 0.4atm pure O2- trying to do a spacewalk at 100kPa even the strongest man in the world would have trouble bending his arms- so before a spacewalk the astronauts need to spend several hours pre-breathing pure O2 to get all the nitrogen out of their bloodstream before they can do a spacewalk. The Apollo program thought it was safer if the astronauts could do a spacewalk at literally any point in the mission, so that's what the spacecraft was designed around.
On the other hand, for long duration spaceflight, introducing a different pressure and atmosphere is just another potential source of health problems. Even today, the largest source of information on how human bodies last under 0.4atm pure O2 is the three Skylab missions from 1973-1974. And so the Soviets- who were always more interested in space stations than the moon- and NASA during the Shuttle era went with the atmosphere that seemed like it offered less health risks for people staying on a space station.
Okay, so what about the Apollo 1 fire? To speed up testing, Apollo 1 did two tests at the same time: the Plugs-Out Test, where the astronauts were in the spacecraft with everything running and practicing their countdown, and the Overpressure test where they pressurized the spacecraft to 1.4 atm (to mimic the pressure differential in outer space). And they did it with pure O2. So you had all of these electronics running in an environment at 1.4atm pure O2. And that was incredibly dangerous, in a way that actual spaceflight, a mere 0.4atm O2, was not. But it was just a test, another in a long string of them, and no one involved ever really analyzed it as a potential hazard.
After Apollo 1 a few things were changed: one was that they did the Plugs Out test and the Overpressure test at different times, and a lot of stuff was turned off for the Overpressure test. Another was that the Apollo capsule at takeoff was 1atm 80/20 until a couple of minutes into flight, when it dumped the cabin atmosphere overboard and replaced it with pure O2 at 0.4atm. That's why the astronauts carried little packs in their arms in all the pictures of them getting into the spacecraft, that's the pure O2 tank that they were breathing off of until they could switch to the atmosphere in the cabin after it was replaced.