Quote from: Brovane on 08/24/2016 08:38 pmSo how far off are Dragon and CST-100 from the requested 1 in 270 number? I don't think you're going to find that information publicly available.
So how far off are Dragon and CST-100 from the requested 1 in 270 number?
Quote from: SWGlassPit on 08/25/2016 02:35 pmQuote from: Brovane on 08/24/2016 08:38 pmSo how far off are Dragon and CST-100 from the requested 1 in 270 number? I don't think you're going to find that information publicly available.Why wouldn't it be publicly available?
Quote from: Brovane on 08/26/2016 03:29 amQuote from: SWGlassPit on 08/25/2016 02:35 pmQuote from: Brovane on 08/24/2016 08:38 pmSo how far off are Dragon and CST-100 from the requested 1 in 270 number? I don't think you're going to find that information publicly available.Why wouldn't it be publicly available? Maybe they don't have to.
One word: Proprietary.
Quote from: Robotbeat on 08/26/2016 01:41 amQuote from: srtreadgold on 08/25/2016 09:46 pmQuote from: Robotbeat on 08/25/2016 08:44 pmIf NASA gets uppity about it, say the astronauts have to remain suited the whole time. That'll get approval done for the early missions, then the astronaut corp would get mad and say they don't have to wear the suits.That only protects against LOC from pressure vessel penetration, other factors could also result in LOC that the suits wouldn't help.Another major one is loss of coolant. Why did you edit out the sublimator part?pressure vessel penetration is probably the biggest one, since if that happens, there's not a lot you can do if you're not suited up. With the other things, there are options, provided you're in a somewhat stable orbit (which you will be 99.9% of the time)Pressure vessel penetration is probably not the biggest one. Pressure vessels tend to be well-protected. Other systems not so much. Spacecraft repair in-orbit is difficult.
Quote from: srtreadgold on 08/25/2016 09:46 pmQuote from: Robotbeat on 08/25/2016 08:44 pmIf NASA gets uppity about it, say the astronauts have to remain suited the whole time. That'll get approval done for the early missions, then the astronaut corp would get mad and say they don't have to wear the suits.That only protects against LOC from pressure vessel penetration, other factors could also result in LOC that the suits wouldn't help.Another major one is loss of coolant. Why did you edit out the sublimator part?pressure vessel penetration is probably the biggest one, since if that happens, there's not a lot you can do if you're not suited up. With the other things, there are options, provided you're in a somewhat stable orbit (which you will be 99.9% of the time)
Quote from: Robotbeat on 08/25/2016 08:44 pmIf NASA gets uppity about it, say the astronauts have to remain suited the whole time. That'll get approval done for the early missions, then the astronaut corp would get mad and say they don't have to wear the suits.That only protects against LOC from pressure vessel penetration, other factors could also result in LOC that the suits wouldn't help.
If NASA gets uppity about it, say the astronauts have to remain suited the whole time. That'll get approval done for the early missions, then the astronaut corp would get mad and say they don't have to wear the suits.
This. Commercial crew and cargo are a new world. The companies involved in this aren't going to release technical information publicly unless either they are required to in their contract or they believe it will serve their interests. These aren't the Shuttle days anymore.
Quote from: srtreadgold on 08/26/2016 03:10 amQuote from: Robotbeat on 08/26/2016 01:41 amQuote from: srtreadgold on 08/25/2016 09:46 pmQuote from: Robotbeat on 08/25/2016 08:44 pmIf NASA gets uppity about it, say the astronauts have to remain suited the whole time. That'll get approval done for the early missions, then the astronaut corp would get mad and say they don't have to wear the suits.That only protects against LOC from pressure vessel penetration, other factors could also result in LOC that the suits wouldn't help.Another major one is loss of coolant. Why did you edit out the sublimator part?pressure vessel penetration is probably the biggest one, since if that happens, there's not a lot you can do if you're not suited up. With the other things, there are options, provided you're in a somewhat stable orbit (which you will be 99.9% of the time)Pressure vessel penetration is probably not the biggest one. Pressure vessels tend to be well-protected. Other systems not so much. Spacecraft repair in-orbit is difficult....right, but we're talking loss of crew, not just "oh, my spacecraft is stranded, halp."Please give actual examples not "that's probably not the biggest one."
Quote from: Robotbeat on 08/26/2016 03:01 pmQuote from: srtreadgold on 08/26/2016 03:10 amQuote from: Robotbeat on 08/26/2016 01:41 amQuote from: srtreadgold on 08/25/2016 09:46 pmQuote from: Robotbeat on 08/25/2016 08:44 pmIf NASA gets uppity about it, say the astronauts have to remain suited the whole time. That'll get approval done for the early missions, then the astronaut corp would get mad and say they don't have to wear the suits.That only protects against LOC from pressure vessel penetration, other factors could also result in LOC that the suits wouldn't help.Another major one is loss of coolant. Why did you edit out the sublimator part?pressure vessel penetration is probably the biggest one, since if that happens, there's not a lot you can do if you're not suited up. With the other things, there are options, provided you're in a somewhat stable orbit (which you will be 99.9% of the time)Pressure vessel penetration is probably not the biggest one. Pressure vessels tend to be well-protected. Other systems not so much. Spacecraft repair in-orbit is difficult....right, but we're talking loss of crew, not just "oh, my spacecraft is stranded, halp."Please give actual examples not "that's probably not the biggest one."Damage they might not know about until too late. Columbia comes to mind.
...right, but we're talking loss of crew, not just "oh, my spacecraft is stranded, halp."Please give actual examples not "that's probably not the biggest one."
Quote from: woods170 on 08/26/2016 08:24 amOne word: Proprietary.This. Commercial crew and cargo are a new world. The companies involved in this aren't going to release technical information publicly unless either they are required to in their contract or they believe it will serve their interests. These aren't the Shuttle days anymore.
Okay, so damage to the heatshield. But the heatshield is protected by the trunk. And before departure (but after undocking), Station can take pictures of the rest of the craft to see if there's a major problem.
And to take Soyuz as an example, the capsule lands ~3 hours after undocking. The odds that dozens of Soyuzes have had no life-threatening MMOD after each spent like 6 months in orbit but that a Dragon has a significant chance of getting a life-threatening hit in just 3 hours after undocking seems very small... You're talking like 1/100,000. More like 1:million because something bad enough to severely damage the capsule but remain undetected is even smaller, especially since the trunk protects the heatshield.
This is why I think the main dangers are from things we haven't fully quantified, yet. MMOD LOC not due to pressure vessel rupture or loss of coolant seems remote. But spaceflight is NOT that safe. So the danger is probably something we haven't fully quantified.
Quote from: Robotbeat on 08/26/2016 03:01 pm...right, but we're talking loss of crew, not just "oh, my spacecraft is stranded, halp."Please give actual examples not "that's probably not the biggest one."A few examples, not based on any particular specific vehicles or scenarios:Crew pressure vessel penetrations of sufficient size to prevent successful emergency countermeasures (e.g., donning of pressure suits).
Damage to heat shields that allow sufficient hot gas intrusion during reentry to result in structural failure.
Damage to propulsion systems (including thrusters, propellant tanks, valves, feedlines, and control hardware) that could result in any of the following: inability to deorbit, inability to control attitude during reentry, leakage of thruster exhaust into spacecraft structure, leakage of unreacted propellant into structure (including potential for hypergolic propellants to mix in places they really shouldnt), bursting of propellant tanks.
Damage to reentry power systems (including batteries, cables, and control equipment) that results in any number of failures, including loss of reentry control and loss of recovery systems.
Damage to spacecraft command and data handling hardware that results in loss of control or loss of recovery systems.
Damage to recovery system hardware that prevents initiation of both primary and backup recovery system deployment.
Damage to cooling systems that results in coolant being released into crew pressure vessel, creating a toxic atmosphere.
There are no doubt several others I haven't thought of for this post. Not all of these are immediately detectable. Not all of those that are detectable are correctable after the fact.
Doesn't NASA set the standards for what goes into deriving the LOC number?
Again, heat shield is protected by the trunk and damage could be spotted from Station shortly after undocking, and the odds of getting hit in the few hours between undocking and landing are ridiculously small.
Quote from: Robotbeat on 08/26/2016 04:31 pmAgain, heat shield is protected by the trunk and damage could be spotted from Station shortly after undocking, and the odds of getting hit in the few hours between undocking and landing are ridiculously small.The backshell however is not protected by the trunk/service module and is exposed in a high threat region for long periods of time before reentry, and inspection might not catch the damage.
--snip--Basically they all are detectable. They basically are all correctable (via rescue) as long as you haven't done the deorbit burn yet (in which case you have only minutes of vulnerable time), but still have lots of redundancies even then.Again, this sounds like corner-cases of corner-cases.I sincerely, SINCERELY doubt it'll be MMOD that causes the next space disaster.EDIT:You repeated a lot of the same risks in order to make it sound like a long list. That's why I repeated my responses.
Quote from: Robotbeat on 08/26/2016 04:31 pm--snip--Basically they all are detectable. They basically are all correctable (via rescue) as long as you haven't done the deorbit burn yet (in which case you have only minutes of vulnerable time), but still have lots of redundancies even then.Again, this sounds like corner-cases of corner-cases.I sincerely, SINCERELY doubt it'll be MMOD that causes the next space disaster.EDIT:You repeated a lot of the same risks in order to make it sound like a long list. That's why I repeated my responses.A few points:The base heat shield is not the only heat shield. The backshell heat shield has no protection. Zero. None.
Sufficient penetration of the backshell heat shield is absolutely a LOC event.
That this is easily detected is only your assertion and is not necessarily borne out by facts.
It depends greatly on what structure and infrastructure exists behind the strike.
Not all failures are immediately detectable. This is undisputable fact, despite your assertions to the contrary.
Nobody is saying that MMOD is the cause of the next space disaster; that is a strawman argument.
Your impression that I simply repeated redundant items belies your failure to understand what I wrote and nothing more. The only thing that I repeated was that there was a strike.
The analyses cover as many corner cases as they can, including the likelihood of loss of redundant systems.