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Post by ka9q on Jul 19, 2010 6:35:37 GMT -4
The one Apollo 13 decision I've always had my doubts about was the decision to keep the SM attached all the way back to earth. I know the stated reason: concern that the heat shield on the bottom of the CM might not survive being exposed to deep space. But I've never been able to find out if that concern was based on an actual test or analysis, or if it was just one of those "well, we just don't know" kinds of things. There were a lot of unknowns during Apollo 13, including whether they'd make it back before their consumables ran out. As it turned out, they did. But they could have made it back a lot faster without that excess dead weight.
I've also wondered about the decisions taken to diagnose the fuel cells immediately after the explosion. It wasn't known at the time that the explosion had shocked the O2 valves closed for FCs 1 and 3; in fact, it wasn't even known for some time that there'd been an explosion. There was no telemetry on the states of those valves, and even the c*ckpit indications were such that the valves appeared open because the H2 valves appeared open. [note added - does this board really censor that two-syllable word for the control area of a spacecraft or airplane? Geez.]
But as I read the blow-by-blow I kept wondering "why didn't it occur to somebody to at least cycle those valves?"
I knew that if you shut down the fuel cells you couldn't restart them, but I had understood the reason to be that you didn't have the power to bring them up to operating temperature in space. Ground power was needed for that.
I recently asked Sy Liebergot about this and learned something new: a loss of pressure in the O2 feed to the fuel cell allowed the KOH electrolyte (which was pressurized) to break out through the anode and damage the fuel cell in under a minute. Suddenly it made sense. Not that it would have made any difference, of course.
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Post by PeterB on Jul 19, 2010 10:28:49 GMT -4
The one Apollo 13 decision I've always had my doubts about was the decision to keep the SM attached all the way back to earth. I know the stated reason: concern that the heat shield on the bottom of the CM might not survive being exposed to deep space. But I've never been able to find out if that concern was based on an actual test or analysis, or if it was just one of those 'well, we just don't know' kinds of things. There were a lot of unknowns during Apollo 13, including whether they'd make it back before their consumables ran out. As it turned out, they did. But they could have made it back a lot faster without that excess dead weight. According to Murray and Cox's "Apollo - The Race to the Moon", "No one had ever tested what would happen to the heat shield if it were exposed to the thermal conditions of outer space for forty hours before it had to work. No one knew how much effect it would have on letting heat out of, or cold into, the command module itself. Deiterich and Reed didn't want to use Apollo 13 to find out." They go on to say that getting back faster wouldn't have been of much use. First, by the time of the PC+2 burn, apparently the engineers were confident they had most of the consumables problems under control. And second, Mission Control needed the time to develop the new re-entry checklist, including the business of powering up the CM. |
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Post by PhantomWolf on Jul 19, 2010 16:43:09 GMT -4
The only consumable they really lacked was the spare LiOH canisters (which were about a foot away outside in the MESA and totally unreachable) and even then they actually still had enough inside the cabin to get them to within about 4 hours of Earth (two large cylinders and three small ones.) The issue was that doing so required them to be running with a high Carbon Dioxide level and that was something they didn't want to do, thus the "fix" of putting a square peg in a round hole.
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Post by ka9q on Jul 19, 2010 18:02:23 GMT -4
The only consumable they really lacked was the spare LiOH canisters (which were about a foot away outside in the MESA and totally unreachable) I wonder if they would ever have considered an EVA to get them. They actually had plenty of oxygen - ironically, given the loss of the O 2 tanks in the SM - and could have afforded a single cabin dump. The EVA could have been done from just one spacecraft with the tunnel hatches closed to save the atmosphere in the other, with the OPS providing backup O2. Just outside on the LEM was another potentially useful item: the plutonium fuel capsule for the SNAP-27. It dissipated about 1.5 kW of heat, enough to have kept them nice and warm instead of freezing on their way back. And it could have been recovered and reused instead of being allowed to re-enter uncontrolled along with Aquarius to drop into the ocean. Contrary to popular belief, radiation would not have been a significant hazard. Plutonium dioxide was chosen specifically because it was a pure alpha emitter with minimal radiological hazards. The real problem would have been ensuring a way to get rid of all that heat at all times during the return, entry and recovery. |
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Post by PhantomWolf on Jul 19, 2010 18:13:06 GMT -4
The only consumable they really lacked was the spare LiOH canisters (which were about a foot away outside in the MESA and totally unreachable) I wonder if they would ever have considered an EVA to get them. They actually had plenty of oxygen - ironically, given the loss of the O 2 tanks in the SM - and could have afforded a single cabin dump. The EVA could have been done from just one spacecraft with the tunnel hatches closed to save the atmosphere in the other, with the OPS providing backup O2. Just outside on the LEM was another potentially useful item: the plutonium fuel capsule for the SNAP-27. It dissipated about 1.5 kW of heat, enough to have kept them nice and warm instead of freezing on their way back. And it could have been recovered and reused instead of being allowed to re-enter uncontrolled along with Aquarius to drop into the ocean. Contrary to popular belief, radiation would not have been a significant hazard. Plutonium dioxide was chosen specifically because it was a pure alpha emitter with minimal radiological hazards. The real problem would have been ensuring a way to get rid of all that heat at all times during the return, entry and recovery. I'm unsure if it was ever considered, it did cross my mind too. I know that during the later missions (15-17) the CMP did a spacewalk to recover the film from the SM cameras, but I have no idea if they could have done a spacewalk to open the MESA in flight, or if they could have even done a spacewalk on 13 at all. I'd suspect that if it was considered, and it likely was, they decided against attempting a never before tried operation when they were already in deep doo-doo. It is possible that had the sqaure peg in a round hole failed, they might have gone for a more drastic and dramatic option. |
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Post by ka9q on Jul 19, 2010 22:42:44 GMT -4
Haise and Lovell, at least, certainly had the ability to do a 0g EVA. All Apollo lunar crews trained for a contingency EVA back to the CSM in the event of a failed LM/CSM redocking after ascent and rendezvous. That's why each crew carried the OPS and LEVAs back to lunar orbit. Missions 15-17 would later make use of one of each during the CMP deep space EVA. But 13 had two perfectly good PLSSes and OPS available, so they wouldn't have been in a hurry as in a contingency transfer using OPS alone.
The tricky part would have been doing it in 0 g, trying to keep everything inside the MESA from floating away when they opened it up.
With today's fast digital links, CCDs and other electronic sensors there probably wouldn't be any need for a deep space EVA in an Apollo J-type mission. It's easy to forget that until fairly recently, high quality space photography required film that had to be physically returned to earth at enormous cost and complexity.
Lunar Orbiter was an innovative hybrid of film and electronic sensing, but the results were still nowhere near the quality of the film physically returned by each Apollo mission.
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Post by banjomd on Jul 20, 2010 5:48:47 GMT -4
Haise and Lovell, at least, certainly had the ability to do a 0g EVA. All Apollo lunar crews trained for a contingency EVA back to the CSM in the event of a failed LM/CSM redocking after ascent and rendezvous. That's why each crew carried the OPS and LEVAs back to lunar orbit. Missions 15-17 would later make use of one of each during the CMP deep space EVA. But 13 had two perfectly good PLSSes and OPS available, so they wouldn't have been in a hurry as in a contingency transfer using OPS alone... Great stuff. Keep "thinking out loud", guys! ;D |
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