Can anyone explain to me the following: the report say that the Columbia crew lost consciousness immediately on the decompression, so fast that even the crew members who did complete the suit pressure check before had not time to seal their helmet visors and activate the suit O2 supply. Yet the same report says that this activity takes single seconds. All the sources I checked say that TUC (time of useful consciousness) on rapid decompression to full vacuum is 8-12 seconds (see Wikipedia on "rapid decompression"). This value is supposedly based among others on two cases of accident with pressure suit testing in pressure chambers. It (the 8-12 seconds) also agrees with the time it takes the deoxygenated blood to reach the brain. There are factors which may shorten the TUC (i.e. physical exertion) but it does not look like it happened here. So I do not understand why ALL the crew did not pressurize their suits. Also - the very fact that the NASA procedure was for the crew to descend with visors open indicates that the med authorities were certain the crew will have time to pressurize the suits in the case of decompression. I cannot believe NASA was not basing this procedures on well established knowledge. So what have happened? The pilots may have deliberately proceeded with trying to control the situation and decided NOT to loose time for suit pressurization. It is a separate issue - they might understand that out of control shuttle will mean death anyway and trying to save the crew to the last moment of consciousness. But what about the rest of the crew? It looks like either the TUC is badly understood or something else happened (tumbling intense enough so it was impossible to seal the visors?). I have the feeling that the report does not raise this issue clearly enough, and maybe even contradicts itself (they say that the G forces actually initially decreased upon CE which was - according to report - also simultaneous with decompression). Any comments?
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Can anyone explain to me the following: the report say that the Columbia crew lost consciousness immediately on the decompression, so fast that even the crew members who did complete the suit pressure check before had not time to seal their helmet visors and activate the suit O2 supply. Yet the same report says that this activity takes single seconds. All the sources I checked say that TUC (time of useful consciousness) on rapid decompression to full vacuum is 8-12 seconds (see Wikipedia on "rapid decompression"). This value is supposedly based among others on two cases of accident with pressure suit testing in pressure chambers. It (the 8-12 seconds) also agrees with the time it takes the deoxygenated blood to reach the brain. There are factors which may shorten the TUC (i.e. physical exertion) but it does not look like it happened here. So I do not understand why ALL the crew did not pressurize their suits. Also - the very fact that the NASA procedure was for the crew to descend with visors open indicates that the med authorities were certain the crew will have time to pressurize the suits in the case of decompression. I cannot believe NASA was not basing this procedures on well established knowledge. So what have happened? The pilots may have deliberately proceeded with trying to control the situation and decided NOT to loose time for suit pressurization. It is a separate issue - they might understand that out of control shuttle will mean death anyway and trying to save the crew to the last moment of consciousness. But what about the rest of the crew? It looks like either the TUC is badly understood or something else happened (tumbling intense enough so it was impossible to seal the visors?). I have the feeling that the report does not raise this issue clearly enough, and maybe even contradicts itself (they say that the G forces actually initially decreased upon CE which was - according to report - also simultaneous with decompression). Any comments?