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Author
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Topic: Lunar Module ascent stage and pressurization
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moorouge
Member Posts: 2458
From: U.K.
Registered: Jul 2009
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posted 07-29-2010 08:18 AM
   
Bearing in mind the frail construction of the Apollo Lunar Module, would it have survived lift-off from the lunar surface if the crew had failed to pressurise it after their last EVA? |
kr4mula
Member Posts: 642
From: Cinci, OH
Registered: Mar 2006
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posted 07-29-2010 12:05 PM
I would think they designed it to survive unpressurized as a safety measure in case the LM had a leak, stuck-open hatch, or something similar. Remember, the structure would only be fighting the acceleration of its own mass, not air resistance (keep in mind the lower lunar gravity=lower total accel forces on the structure). I don't know the acceleration rate of the LM ascent off-hand, but given the lack of seats, it couldn't have been too high. |
jasonelam
Member Posts: 691
From: Monticello, KY USA
Registered: Mar 2007
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posted 07-29-2010 12:27 PM
quote:
Originally posted by kr4mula:
I don't know the acceleration rate of the LM ascent off-hand, but given the lack of seats, it couldn't have been too high.
From what I have read, it would have not been much, between .3 and .6G |
Lou Chinal
Member Posts: 1332
From: Staten Island, NY
Registered: Jun 2007
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posted 07-29-2010 05:10 PM
A pressurized LM would have been stiffened not strengthened. Much like the little bend added to the hole in a wing spar. |
Greggy_D
Member Posts: 977
From: Michigan
Registered: Jul 2006
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posted 08-04-2010 08:21 AM
I asked Charlie Duke if the LM liftoff/ascent was a violent maneuver. His reply:"Nah, it wasn't violent. It was real sporty though." |
moorouge
Member Posts: 2458
From: U.K.
Registered: Jul 2009
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posted 08-04-2010 09:46 AM
quote:
Originally posted by Lou Chinal:
A pressurized LM would have been stiffened not strengthened. Much like the little bend added to the hole in a wing spar.
Without the added stiffening provided by pressurization, wouldn't there have been too much flexing of the structure to make guidance a problem? |
SpaceAholic
Member Posts: 4494
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 08-04-2010 10:29 AM
Ascent stage flexture was primarily an issue with the aluminum alloy sheet metal shell, however these were attached to rigid aluminum beams and had integrated machined stiffeners and longrons comprising the inflexible skeleton of the flight vehicle. The IMU responsible for guidance input was anchored to structural members precisely to provide a contiguously stable reference point. Pressurization was relied on to maintain seal integrity in the hatches. |
GACspaceguy
Member Posts: 2516
From: Guyton, GA
Registered: Jan 2006
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posted 08-04-2010 11:33 AM
Take a look at this photo of the LM assent stage showing the internal structure (note that this was an earlier configuration as seen with the round front hatch but the basics are the same).  The skin has a number of structural elements that are referred to as stiffeners attached to the outside of the skin. The construction is the same as aircraft structure and the thickness and fasteners are the same as well. Just as a commercial airline is pressurized (typically with a pressure higher than what was used in the LM) yet does not gain or need any structural benefit from it, neither would the LM. Just for an example, if you have ever flown a Canadair Regional Jet 700 (CRJ) the only thing between you and the open sky is an aluminium skin that is 63 thousands of an inch thick at the places where frames are attached and only 40 thousands of an inch in the open bay areas. As long as the vehicle is designed to dissipate the load that is being applied correctly, it is amazing what it can withstand (plus the built in factors of safety, but that is another story). |
Saturn V
Member Posts: 176
From: Golden, Colorado, USA
Registered: Nov 2006
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posted 08-04-2010 12:27 PM
It really does take a rocket scientist to figure this stuff out.  Very nice photo by the way. |
Lou Chinal
Member Posts: 1332
From: Staten Island, NY
Registered: Jun 2007
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posted 08-15-2010 01:14 AM
This brings up a different question; what if the hatch could not be closed at all? I imagine the IMU could compensate going through all the pitch and roll maneuvers? |
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