Quote from: Joffan on 12/09/2013 05:55 pmPerhaps a separate emergency egress is not needed for astronauts in the capsule. If it is mandated, then the need is moot.
Perhaps a separate emergency egress is not needed for astronauts in the capsule.
Perhaps a separate emergency egress is not needed for astronauts in the capsule. As a discussion* concept, that's could be what the pad abort capability is for.
I was actually wondering, does the F9 use a common bulkhead for both stages? If so is this two flat sheets of metal with insulation between them? Isn't there a high thermal flux between the lox and the kerosene?Or do they use spherical domes to cap of the separate tanks?
Quote from: Joffan on 12/09/2013 05:55 pmPerhaps a separate emergency egress is not needed for astronauts in the capsule. As a discussion* concept, that's could be what the pad abort capability is for.Pad abort is useful for problems with the booster, but what about problems with the spacecraft? It wouldn't be helpful in an Apollo 1 situation.
The issue I could have with using pad abort as the escape mechanism is the loss of diverse options. But emergencies of the sort we're thinking about - where escape of any sort is a practical life-saving option - are so few that the benefit of diverse options looks to be lower than the benefit of simplicity.
It's always possible to imagine a scenario so severe that a particular option would be no good. The question is whether the balance of risks mean that that option is ruled out as a result.
Now there are consequences to a pad abort, of course, but the lowered complexity of reusing an existing system might still mean that slightly increased risks in one phase are worth the reduction in risks across the entire scope of operations.
Quote from: Joffan on 12/10/2013 09:46 pmThe issue I could have with using pad abort as the escape mechanism is the loss of diverse options. But emergencies of the sort we're thinking about - where escape of any sort is a practical life-saving option - are so few that the benefit of diverse options looks to be lower than the benefit of simplicity.I think the general view of American society regarding human spaceflight is that at every point where a crew might face a life-threatening situation, they must have some means which provides them with a plausible chance of survival. This includes situations at and around the pad before launch. Just as an example, what about a potential life-threatening situation that could occur while the ground support personnel were assisting the crew through the open hatchway of the spacecraft? How could any pad abort functionality provide in that type of situation, and for all the ground and flight crew members, a plausible chance of survival?
Quote from: Joffan on 12/10/2013 09:46 pmIt's always possible to imagine a scenario so severe that a particular option would be no good. The question is whether the balance of risks mean that that option is ruled out as a result.An Apollo 1 scenario is a known known, first because it has happened in the past, and second because we have an existing method that will satisfactorily accommodate it: open the door and slide down the chute.
QuoteNow there are consequences to a pad abort, of course, but the lowered complexity of reusing an existing system might still mean that slightly increased risks in one phase are worth the reduction in risks across the entire scope of operations.There is no "lowered complexity" by using the pad abort. It is increased complexity. You are talking about additional time to exit the capsule, additional systems that must work together, and additional opportunities for something to go wrong.
Except that the likelihood of a recurrence of the Apollo 1 tragedy is zero. It has been avoided by the shift away from pure oxygen environments.
I think the general view of American society regarding human spaceflight is that at every point where a crew might face a life-threatening situation, they must have some means which provides them with a plausible chance of survival. This includes situations at and around the pad before launch. Just as an example, what about a potential life-threatening situation that could occur while the ground support personnel were assisting the crew through the open hatchway of the spacecraft? How could any pad abort functionality provide in that type of situation, and for all the ground and flight crew members, a plausible chance of survival?