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Do I hear a MOOSE coming over the horizon?
Seriously, isn't it about time someone gave some serious thought to an ultra-minimal personal re-entry scheme? Would the 'cure' actually work without killing the 'patient' P Earl Colby Pottinger wrote: (Derek Lyons) : There probably isn't a single company in the world that can do the job, nor a consortium of the either. You are seriously delusional as to how complex a 'simple' taxi/lifeboat is. |
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In article ,
Phil Paisley wrote: Do I hear a MOOSE coming over the horizon? Seriously, isn't it about time someone gave some serious thought to an ultra-minimal personal re-entry scheme? Alas for the notion, that's not really what's called for. A lifeboat that can carry at least two or three people is generally superior, not least because it doesn't require donning a spacesuit on short notice (which is all too likely to cause decompression sickness, aka the bends -- not only painful but also deadly dangerous). -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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I wrote:
Seriously, isn't it about time someone gave some serious thought to an ultra-minimal personal re-entry scheme? Alas for the notion, that's not really what's called for. A lifeboat that can carry at least two or three people is generally superior, not least because it doesn't require donning a spacesuit on short notice (which is all too likely to cause decompression sickness... A friend has pointed out, in private mail, that you could do this with a two-step emergency setup: an emergency refuge, which would provide life support for a while and give time for prebreathing procedures, and then a spacesuit-dependent bailout system. While that's feasible, my gut feeling is that you're still better off with a non-spacesuit lifeboat. And it does not strike me as substantially harder to do, not when you deal with all the details. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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Derek Lyons wrote:
It's also possible to design an emergency escape suit *that doesn't require prebreathing*. Get in it, seal it, and pop out the airlock. Prebreathe while dropping the pressure down to a level where you can move the suit, complete the remainder of the escape sequence. Thing is that for an escape pod, you do not need mobility. You're not going to be using some fancy screwdriver to connect cables and pipes and install antennas. You just want to fire a deorbit engine and fall down. Once back in atmosphere, you'd regain mobility as atmospheric pressure increases. An escape pod is more likely to be some pressurized shell. A de-orbit engine on a space suit might burn some of your extremities. |
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In article ,
Derek Lyons wrote: It's also possible to design an emergency escape suit *that doesn't require prebreathing*. Get in it, seal it, and pop out the airlock. Prebreathe while dropping the pressure down to a level where you can move the suit, complete the remainder of the escape sequence. Unfortunately, starting from the station's normal 14.7psi atmosphere, suit prebreathing even on an emergency basis takes about four hours, which is kind of a long time to just float in the suit. (Preplanned spacewalks use less prebreathing time than that because those guys live in reduced pressure, with increased oxygen content, for 12+ hours first.) Guys without current spacewalk training are going to be essentially immobilized until pressure is down to near-normal suit levels; there isn't going to be any useful mobility during the transition. Guys *with* current spacewalk training -- which puts a lot of emphasis on building up hand and arm muscles in particular -- may have some limited mobility late in the transition. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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In sci.space.policy Henry Spencer wrote:
In article , Phil Paisley wrote: Do I hear a MOOSE coming over the horizon? Seriously, isn't it about time someone gave some serious thought to an ultra-minimal personal re-entry scheme? Alas for the notion, that's not really what's called for. A lifeboat that can carry at least two or three people is generally superior, not least because it doesn't require donning a spacesuit on short notice (which is all too likely to cause decompression sickness, aka the bends -- not only painful but also deadly dangerous). And putting on my heretic hat... Does a minimal reentry scheme require a spacesuit? If there is a hole in your reentry vehicle, you'r probably already dead. |
#9
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(Henry Spencer) :
In article , Derek Lyons wrote: It's also possible to design an emergency escape suit *that doesn't require prebreathing*. Get in it, seal it, and pop out the airlock. Prebreathe while dropping the pressure down to a level where you can move the suit, complete the remainder of the escape sequence. Unfortunately, starting from the station's normal 14.7psi atmosphere, suit prebreathing even on an emergency basis takes about four hours, which is kind of a long time to just float in the suit. (Preplanned spacewalks use less prebreathing time than that because those guys live in reduced pressure, with increased oxygen content, for 12+ hours first.) Guys without current spacewalk training are going to be essentially immobilized until pressure is down to near-normal suit levels; there isn't going to be any useful mobility during the transition. Guys *with* current spacewalk training -- which puts a lot of emphasis on building up hand and arm muscles in particular -- may have some limited mobility late in the transition. Why does prebreath take so long? Bubbles? But at the lower pressure tere is not that much gas in the blood, is there? People often dive to 30 to 50 feet and come back up in time measured in minutes not hours. So why so long? And if caution is the main reason for such a long time how much can it be cut back for an emergency? Earl Colby Pottinger -- I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos, SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to the time? http://webhome.idirect.com/~earlcp |
#10
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In article ,
Earl Colby Pottinger wrote: Unfortunately, starting from the station's normal 14.7psi atmosphere, suit prebreathing even on an emergency basis takes about four hours, which is kind of a long time to just float in the suit. (Preplanned spacewalks use less prebreathing time than that because those guys live in reduced pressure, with increased oxygen content, for 12+ hours first.) Why does prebreath take so long? Bubbles? Getting nitrogen flushed out of the body, so it doesn't form bubbles when the pressure is reduced. Unfortunately, it's noticeably soluble in some body materials, so it takes a while to diffuse out. But at the lower pressure tere is not that much gas in the blood, is there? There's enough. In fact, NASA's decompression rules are probably too optimistic: mild unreported cases of the bends -- both in suit operations and in pre-Shuttle low-pressure spacecraft -- are not uncommon. E.g., Michael Collins had trouble in one knee early in both his flights. The U-2 uses similar operations rules, and an anonymous survey showed that 75% of U-2 pilots had had the bends at least once, and 13% had altered or aborted a flight because of it. People often dive to 30 to 50 feet and come back up in time measured in minutes not hours. How long they spend down there matters. Guys who spend a week underwater take the ascent very slowly. if caution is the main reason for such a long time how much can it be cut back for an emergency? Four hours *is* the emergency value, which still incurs some risk of some adverse symptoms. In a life-or-death crisis, you load up on painkillers and do what you have to do... but it may kill you. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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