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Post by porphyry on Feb 3, 2010 1:07:46 GMT -4
Hi Folks, New poster here. I'm a long-time fan of David McGowan's writings about the American political scene. Dave has posted a new series called "Moondoggie" in which he advocates for the Moon Landing Hoax theory. I think he covers some new ground, that I'd like to discuss here. If anybody wants to read his entire series, it's available at: www.davesweb.cnchost.comReferring to information from a Science Channel TV show "First on the Moon", Dave wrote: Another curious fact that First on the Moon made note of was that, according to Harold Loden, Apollo 11 mission controller, “The skin on the crew cabin [of the lunar module] was very thin, and that was all done because of weight savings.” Another talking-head added that, “If you really took your finger and poked hard at it, you could poke right through the outer skin of the spacecraft. It was about the thickness of two layers of aluminum foil.” Project Manager Thomas Kelly concurred, noting that “the skin, the aluminum alloy skin of the crew compartment was about 12/1000s of an inch thick. That’s equivalent to about three layers of Reynold’s Wrap that you would use in the kitchen." Does anybody know -- is this true that the LEM crew cabin was made from 12 mil aluminum foil? |
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Post by laurel on Feb 3, 2010 2:17:49 GMT -4
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Post by Data Cable on Feb 3, 2010 2:32:21 GMT -4
Greetings, porphyry. “The skin on the crew cabin..." [...] ...you could poke right through the outer skin of the spacecraft. [...] “the skin, the aluminum alloy skin of the crew compartment..." First off, what is actually being described here? The outer skin, that is, the micrometeoroid shield, or the inner pressure hull? The two are not the same. Secondly, how does the reported thickness of the unspecified "skin" indicate a hoax? If this were a fictional spacecraft intended to dupe John Q. Layman, which didn't actually have to land on or launch from the moon, couldn't they have just said the whole thing was made of inch-thick titanium? This sounds like little more than an argument from personal incredulity: "I don't believe a spacecraft made of 'aluminum foil' could have worked, so it must have been a hoax." Though to answer your question, according to p.195 of Virtual LM by Scott P. Sullivan, the inner pressure hull structure was a minimum of .012" of aluminum. That is not to say that the entire skin was that thin, or that any area that thin was located anywhere it would be likely or possible for an astronaut to "poke a finger through it." Mind you, the pressure hull had to contain only 5 psi of oxygen. |
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Post by drewid on Feb 3, 2010 3:22:39 GMT -4
The question you have to ask is this:
How come all the qualified engineers and experienced spacecraft designers around the world have never thought this a problem, but someone who has no qualifications in that area thinks it is.
Do you believe someone who knows what they are talking about and has qualifications to prove it? or someone who is guessing.
The whole series is full of argument from incredulity and other mistakes. Even the extensive BAUT thread doesn't manage to catch all the errors.
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Post by Count Zero on Feb 3, 2010 4:20:56 GMT -4
As this photo shows, the inner pressure vessel was well-supported by exterior ribbing every few inches. Despite its light weight, the LM was a quite rugged design. |
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Post by drewid on Feb 3, 2010 4:54:10 GMT -4
It all comes down to this, how thick does it actually need to be from an engineering point of view? The ribbing takes most of the structural load, along with the supporting framework. The forces associated with the installed equipment are taken by assicoated struts and framework, not by the skin. You would probably want the floor thicker, because of the point loads, but even then not much, it was designed for a low G environment after all. OK inertial mass stays the same, but everything likely to be moving in the cabin is designed to be low mass, apart from Buzz and Neil  , point loads should be minimal, the bracing can handle everything else. The rest of the skin is just to hold low pressure oxygen in place. |
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Al Johnston
"Cheer up!" they said, "It could be worse!" So I did, and it was.
Posts: 1,453
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Post by Al Johnston on Feb 3, 2010 5:09:14 GMT -4
Not to mention that there are considerable differences in composition and heat treatment (and thus of mechanical properties) between the aluminium alloys used in aerospace and what goes into baking foil...
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Post by gwiz on Feb 3, 2010 7:26:39 GMT -4
Does anybody know -- is this true that the LEM crew cabin was made from 12 mil aluminum foil? Strictly speaking, aluminium alloy, the standard material used in the structures of aircraft. It was chemically milled down to the required thickness, 12 mil minimum but thicker where it attached to the ribs and other structural elements. For comparison, a typical military aircraft, designed to withstand high-g manoeuvres, would use 18 gauge alloy, that's about 48 mil. |
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Post by porphyry on Feb 3, 2010 14:10:37 GMT -4
Thanks, everyone, for your replies. There seems to be nearly a consensus that the crew cabin was fabricated from an aerospace-quality aluminum alloy with a minimum thickness of 12 mils. The picture linked by Count Zero is very helpful in establishing that the crew cabin was heavily ribbed, and it looks like it was designed to be a pressure vessel.
Data Cable says the LEM was pressurized with 5psi oxygen. I was a little confused about that: I thought that the pure oxygen in Apollo 1 caused a flammability problem, which was cured by moving to a nitrogen-oxygen mix. But you're implying that was on the launch pad only, and they reverted to pure oxygen at reduced pressure during spaceflight? Makes sense to me.
Going back to Dave's original quote from the TV show, I see a big problem with Project Manager Thomas Kelly's statement: actually, Reynolds Wrap is only about 0.5 mils thick, so the LEM crew compartment walls were equal to 24 thicknesses of household aluminum foil, not three layers.
Also, as Data Cable pointed out, the other "talking head" in the quote was talking about the outer skin of the spacecraft, not the crew cabin. Maybe it would be possible to poke your thumb through 2 mils of foil, but not 12 mils.
Laurel, I did see the discussion at BAUT forum, and I tried to set up a login account and pose my question there. I found myself immediately and permanently banned by some automated script running at their server. I'm sure it's some sort of technological glitch, I think I'm a pretty reasonable guy. But I'm just as happy to be here. Thanks for the warm & helpful welcome.
Drewid, I doubt that "all the qualified engineers... around the world" have carefully studied this design, and ran through all the calculations & tests necessary to verify and certify it.
Dave pointed out in his article, that in the early testing of the LEM a window blew out of this pressure chamber. And then, there was the confusion about finger pokes through the exterior panels (not the crew compartment) and the confusion about the thickness of household aluminum foil. So I think Dave was a pretty smart guy to have raised the question.
But after considering the whole picture, and with the conditional understanding that none of us has actually verified the soundness of the design -- I'm going to score this one for you guys.
Certainly Dave has not met any burden of proof, to show that there is any flaw with this design.
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Post by Data Cable on Feb 3, 2010 14:35:17 GMT -4
I thought that the pure oxygen in Apollo 1 caused a flammability problem Pure oxygen at greater than sea-level air pressure (since they were simulating positive pressure for the test) caused the flammability hazard. 5 psi of pure oxygen is only about the same amount of O 2 as is present in the atmosphere, hence no greater a flammability hazard. Subsequent pressure ground testing was done with nitrox. Nitrox during flight is problematic as it adds weight (more gas to carry and a beefier structure to contain it) while partial-pressure O 2 does just the opposite. |
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Post by JayUtah on Feb 3, 2010 14:44:10 GMT -4
Drewid, I doubt that "all the qualified engineers... around the world" have carefully studied this design, and ran through all the calculations & tests necessary to verify and certify it.Are you an engineer? I am, and David McGowan certainly is not. Apollo engineering is required study in all aeronautical engineering curricula with which I am familiar. I have thoroughly studied the LM design as an expert and I find it to be suitable in all respects for the tasks to which it was put. The LM pressure vessel was constructed of chem-milled skin-and-stringer panels that were welded together over a rather standard spar-and-bulkhead structural design and then wrapped with various layers of relatively pedestrian thermal and micrometeoroid shields. These are common techniques in aerospace. Further, I have had extensive conversations with Frank Pullo, who was in charge of the ascent-stage manufacturing effort, and I am convinced that proper manufacturing methods and standards prevailed. ...with the conditional understanding that none of us has actually verified the soundness of the design...That is a false understanding. I personally can produce drawings and analysis of the LM structural, pressure, and thermal designs from memory. Further, I offered to debate David McGowan directly and personally regarding the validity of his claims. His response to me was childish, dismissive, and vulgar. And McGowan has specifically named me in his writings. I would think that it would be important for him to face directly those whom he has maligned, but McGowan does not think so. He prefers to howl from the confines of his walled garden. Not only am I thoroughly unconvinced that McGowan has any relevant expertise in space engineering, and that he has met any burden of proof, I am thoroughly unconvinced that McGowan desires to meet any burden of proof, nor to conform to any standards of adult discussion. In my opinion he is simply writing entertaining nonsense for the benefit of those who would agree with him no matter what he wrote. In my expert, informed, professional opinion David McGowan does not know what he's talking about.
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Post by echnaton on Feb 3, 2010 15:06:58 GMT -4
Data Cable says the LEM was pressurized with 5psi oxygen. I was a little confused about that: I thought that the pure oxygen in Apollo 1 caused a flammability problem, which was cured by moving to a nitrogen-oxygen mix. But you're implying that was on the launch pad only, and they reverted to pure oxygen at reduced pressure during spaceflight? Makes sense to me. While not being an expert, let me see if I can illuminate this further. Apollo 1 was running a pressure testing in 100% oxygen. To do this the pressure needed to be above the sea level pressure of 15 psi, relative to space. IIRC the pressure inside was 2 psi above sea level, making it a full 17 psi of pure oxygen. Almost many things that we consider to be inflammable will burn in that environment, such as aluminum. While undocked form the CM, the LM was at 3.5 psi (I believe) relative to space, giving a similar partial pressure of oxygen as at sea level on earth. In both environments materials maintain the same flammability characteristics and people can breath equally well. |
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Post by Nowhere Man on Feb 3, 2010 19:45:40 GMT -4
Laurel, I did see the discussion at BAUT forum, and I tried to set up a login account and pose my question there. I found myself immediately and permanently banned by some automated script running at their server. I'm sure it's some sort of technological glitch, I think I'm a pretty reasonable guy. But I'm just as happy to be here. Thanks for the warm & helpful welcome. At the bottom of the BAUT index page, there is a Contact Us link (or you can use that-there link). Explain the situation and odds are they'll let you in. BAUT is pretty aggressive when it comes to spambots and sock puppets, but you're probably neither one. ;D Fred |
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Post by porphyry on Feb 3, 2010 22:47:03 GMT -4
JayUtah,
I missed this post earlier, sorry.
I take it you are Jay Windley? Nice to meet you. I just went through Dave's remarks about you. What do you think about McGowan's comments about Phil Plait? Dave isn't much impressed by James Randi, are you?
Also, with regards to the LEM design. Do we need to rely on your excellent memory, or are the original blueprints still readily available? That is, the actual drawings that were used to fabricate the parts, or any slightly higher level of detail that would allow a serious engineer to evaluate the design?
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Post by porphyry on Feb 3, 2010 22:50:03 GMT -4
Nowhere Man, I did try to follow the contact link and so far nothing has happened. They certainly are aggressive about banning all sorts of people, and not at all polite about it either. But as I said earlier, I'm just as happy to be here. I don't think I have time to take on two forums like this at once.
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