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Author
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Topic: Apollo 13: Could have been worse?
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stsmithva
Member Posts: 1940
From: Fairfax, VA, USA
Registered: Feb 2007
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posted 08-18-2010 07:43 PM
   
If you saw the Apollo 13 40th anniversary event at the National Air and Space Museum back in April, you might have heard one of the questions from the audience. Someone who sounded quite knowledgeable, witty, and handsome (OK, it was me) asked: "You've discussed how the astronauts and the ground crew trained for so many scenarios. Was needing to use the lunar module as a lifeboat after the command module became unusable the most dire, dangerous situation you simulated, or was there an even worse possibility that in retrospect you can say "Well, at least that didn't happen"? Kranz said my question was interesting, which was nice to hear from such an interesting person, but his answer didn't quite address my question. He reiterated that they trained for a lot of different things. So I'd be interested to hear what you could tell me. I'm curious to know if there was some other even worse scenario which the astronauts thought about and trained how to survive. Clearly a meteorite instantly destroying the craft was a real nightmare "worst case" possibility -- but not really something they could train for. The LM not being able to lift off on the first attempt would have led to many desperate attempts, and I'm sure they spent a lot of time training with those checklists. This is the "darkest" question I've posed on cS. I'm very thankful these things are appearing only in a "what-if" discussion 40 years later. |
moorouge
Member Posts: 2458
From: U.K.
Registered: Jul 2009
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posted 08-19-2010 11:45 AM
One assumes that you are asking about 'worse than' in what would be a possible surviveable situation. If 'worst' is not surviveable then it seems rather pointless in training for it. |
mjanovec
Member Posts: 3811
From: Midwest, USA
Registered: Jul 2005
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posted 08-19-2010 12:04 PM
I can imagine a scenario where the lunar module limps up into a low, unstable orbit and the command module has to attempt a tricky rendezvous. I don't know if that would qualify as worse than what happened on Apollo 13, but it would certain make for a challenging (if relatively short) malfunction to overcome. And, of course, even worse would be a lunar module stranded on the moon...and the CMP having to take the command module back to earth alone. It may not be a big challenge for the CMP to do so, from a technical standpoint, but it might be a "worst case" scenario that they trained to do. |
garymilgrom
Member Posts: 1966
From: Atlanta, GA
Registered: Feb 2007
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posted 08-19-2010 01:52 PM
Apollo 13 itself could have been worse if the SM explosion had happened at another time - for instance after the LM had left the moon and docked with the CSM it would not have contained the oxygen etc. necessary to support the crew during the return trip to Earth. |
Kite
Member Posts: 855
From: Northampton UK
Registered: Nov 2009
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posted 08-19-2010 04:13 PM
Something I have often wondered about on Apollo 13 is that if the descent stage engine had malfunctioned would it have been possible to jettison it, when still attached to the CSM, and use the ascent engine? Would that have been powerful enough or have sufficient fuel for a successful rescue? |
AP12FAN
New Member Posts:
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posted 08-19-2010 05:09 PM
Some real "could be worse" scenarios that were considered were damage to the heat shield as a result of the explosion. The SM contained an opening up the middle that could have directed explosive debris into the heat shield. Is was also possible that the condensation that built up in the CM while in low power mode could have created a short circuit upon reentry. Apollo One crew discovered the oonsequences of a short in the CM. |
stsmithva
Member Posts: 1940
From: Fairfax, VA, USA
Registered: Feb 2007
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posted 08-19-2010 06:52 PM
quote:
Originally posted by moorouge:
One assumes that you are asking about 'worse than' in what would be a possible surviveable situation. If 'worst' is not surviveable then it seems rather pointless in training for it.
Yes, that's exactly why I described a meteorite strike in the way I did. |
Michael Davis
Member Posts: 530
From: Houston, Texas
Registered: Aug 2002
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posted 08-19-2010 07:16 PM
Well, a failure of the SPS engine to fire on the first attempt at trans-earth injection would have made for a few nasty days. I'm sure that the pressure to find a solution would have been an all consuming national emergency. Kind of like the plot for "Marooned", but in lunar orbit. |
Jay Chladek
Member Posts: 2272
From: Bellevue, NE, USA
Registered: Aug 2007
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posted 08-19-2010 11:24 PM
quote:
Originally posted by Kite:
Something I have often wondered about on Apollo 13 is that if the descent stage engine had malfunctioned would it have been possible to jettison it, when still attached to the CSM, and use the ascent engine? Would that have been powerful enough or have sufficient fuel for a successful rescue?
I seem to recall some contingency plans were drawn up for the ascent stage. Only thing is the descent stage carried the majority of the consumables needed in the LM (additional battery power and of course fuel for the descent stage, possibly some oxygen tankage as well, I'll have to check into that). The ascent engine was designed to thrust at full power for a given time period. Granted I am sure they could have re-programmed the PNGS system for shorter burns, but I don't believe the ascent motor was as robust as the descent one in being able to fire multiple times. A couple problems I see with using the ascent engine though would involve a center of gravity even further out of wack when docked with the dead command module (at least a full LM had more mass to counteract the CSM) and the smaller fuel supply for the ascent stage only would likely get drained faster in trying to do correction burns with the docked stack. I would liken it to a sub-compact trying to tow a multiple horse trailer. Crude analogy, yes, but a LM with a descent stage still attached and its bigger motor and fuel supply has a better shot. I would say it is more likely that if the descent engine had a problem after the firing to get them back on free return and maybe the PC+2 burn to gain speed, then the LM RCS would more likely have been used in an attempt to make correction burns after that. Indeed the last cooridor control burn as I recall was done with the RCS instead of the descent engine. If the descent stage had been cut loose, I doubt the remaining ascent stage would have had the battery power to survive the rest of the trip. |
Kite
Member Posts: 855
From: Northampton UK
Registered: Nov 2009
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posted 08-20-2010 01:04 PM
Thanks Jay. That was a very detailed reply. Much appreciated. I'd always thought of the ascent engine as a useful back up but fortunately it was not needed. |
moorouge
Member Posts: 2458
From: U.K.
Registered: Jul 2009
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posted 08-20-2010 01:37 PM
quote:
Originally posted by Jay Chladek:
A couple problems I see with using the ascent engine though would involve a center of gravity even further out of wack when docked with the dead command module (at least a full LM had more mass to counteract the CSM) and the smaller fuel supply for the ascent stage only would likely get drained faster in trying to do correction burns with the docked stack.
The ascent engine was unable to gimbal, hence this from a NASA report - During the APS burn, upfiring RCS thrusters normally are inhibited to increase the AV capability of the vehicle. Because of this operational mode, the RCS contributes to the thrust acceleration and to the AV experienced by the ascent stage. An additional complication results from the interconnecting of the APS and RCS feed systems. During the APS burn, the interconnect valves between the two feed systems are opened, and the RCS uses APS propellant to maintain attitude control. This mode of operation ensures against the depletion of RCS propellant by a large moynent unbalance in the ascent stage during the ascent burn. Because the RCS operates at a different mixture ratio than does the ascent engine, the mixture ratio of propellant from the APS tanks is not the same as the mixture ratio of the ascent engine. Thus, the effects of the RCS must be known before the APS performance can be calculated. The RCS thrust and flow rates must be used to adjust the vehicle weight and thrust acceleration before meaningful results can be obtained for APS performance. Does this help? |
Max Q
Member Posts: 399
From: Whyalla South Australia
Registered: Mar 2007
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posted 08-21-2010 09:09 AM
Very interesting thread. Raises a question if an Apollo crew was marooned in lunar orbit due to a major malfunction, how long did the realistically have both before the landing and after? |
ilbasso
Member Posts: 1522
From: Greensboro, NC USA
Registered: Feb 2006
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posted 08-21-2010 09:39 PM
How about the actual Apollo 15 instance, where both Scott and Irwin were having heartbeat irregularities after returning from the Moon, Irwin's so bad that he would been treated for a heart attack had he been on Earth? Taking that to worst-case, what would have happened if a crewman died on the way home? |
ilbasso
Member Posts: 1522
From: Greensboro, NC USA
Registered: Feb 2006
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posted 08-21-2010 09:40 PM
How about the actual Apollo 15 instance, where both Scott and Irwin were having heartbeat irregularities after returning from the Moon, Irwin's so bad that he would been treated for a heart attack had he been on Earth? Taking that to worst-case, what would have happened if a crewman died on the way home? |
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