Author Topic: How was LM insulation attached?  (Read 8624 times)

Offline apollo16uvc

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How was LM insulation attached?
« on: January 05, 2018, 10:12:49 AM »
Greetings,

It is pretty common for hoaxers to post the following images:



So my question is, how was the insulation manufactured, put together and attached to the LM? If you could list your sources like documents and oral history that would be great.

Regards,
apollo16uvc

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Offline Jason Thompson

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Re: How was LM insulation attached?
« Reply #1 on: January 05, 2018, 10:22:31 AM »
The Apollo News Reference is an excellent source for summary info about this stuff (what you're after is on pages 7-10), though I always prefer to go down the road of asking the HB to prove that what they are looking at is in fact cardboard, tinfoil and scotch tape, and then ask them why, if NASA wanted to fool us all into thinking it was real, they would actually make something that supposedly looks so fake.
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Offline Glom

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Re: How was LM insulation attached?
« Reply #2 on: January 05, 2018, 12:55:57 PM »
They quoted the photo number. That's uncharacteristically professional for them.

Offline JayUtah

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Re: How was LM insulation attached?
« Reply #3 on: January 05, 2018, 01:08:01 PM »
I also endorse ANR.  Let me also recommend Scott Sullivan's Virtual LM and the always venerable Chariots for Apollo.  But let me also give an answer off the top of my head, from accumulated knowledge.

I also can't endorse Jason's point enough.  All of them.  If you saw a lunar module without its clothes on (and there are plenty of pictures from various sources) you'll see a surprisingly robust aluminum skin-and-stringer construction.  That provides the structural strength -- quite a lot of it.  The thermal and other requirements then get to be satisfied by other materials that don't also have to contribute to the structure.  This is what you get to do when your spacecraft doesn't need to withstand fluid flow against and around its outer skin.  Contrary to lay misconceptions, films, film blankets, and coatings work best for this.  The goal is to save weight.  I'm surprised that people are surprised by film blankets.  Quite a lot of spacecraft at the time and subsequently have outer skins made of blanket or various metalized films.  The LM is not out of the ordinary.

Last part first.  People wonder about the tape.  Yes, it's tape.  But it's not household masking tape or duct tape or anything so pedestrian.  Laymen are always flabbergasted to learn that industrial versions of tape exist.  The most common is "speed tape," thin aluminum sheeting backed with industrial-strength pressure-sensitive adhesive.  What you see on the LM is likely Mylar or Kapton tape.  That too has an industrial-strength pressure-sensitive adhesive.  Adhesives that strong are not routinely sold to the general public because of how the general public generally behaves.  Yes, it can stick ferociously to skin.  Tape is used in high-end engineering for precisely the same reasons it's useful around the house.  It's often the best way to fasten two things together.  Seaming two sections of a blanket or thin sheeting isn't best done with a piercing fastener, as tearout would inevitable result.  Tape spreads the load properly.

Attachment to the LM secondary frame, however, sometimes used properly protected piercing fasteners, usually to a standoff that kept the blanket the proper distance from the inner pressure vessel.  This is nearly identical to the way insulation blankets are laid up on airliners.  Not all of that is visible from the outside of the LM.

The various materials for the film blankets, e.g., aluminized Kapton, come on rolls.  Manufacture is merely a matter of unrolling the materials onto a table to build up the layers (in a properly controlled environment, of course).  Some blankets have layer-contact constraints, which means each layer has to be crinkled randomly so that it doesn't make full contact with its neighbors.  As this was most effectively done by hand, the size of the resulting blanket stock was limited.  This is why the outer skin had to be assembled in patchwork fashion.  You gain nothing by trying to cut patterns in the material before lamination.  It's just as effective -- and far easier -- to custom-cut the finished blanket and then join the patches with tape.

If you examine LM-2 closely, you'll see that its aft equipment bay covers are neatly screwed into the secondary structure via correctly-space overlapping eyelet holes and proper grommets.  That's how you'd design it "properly."  But you see LM-5's AEB covers just taped on.  That's how I'd expect the design to turn out after several passes of design review with attention to manufacturability and weight savings.

The lunar environment is not "hostile" in all the ways the Earth's is and then some.  It's just more hostile in some ways and more forgiving in others.  When you have no air, and you have a piece of material whose only job is to keep the sun from shining on something -- not fend of spear-throwing aliens or giant squids -- then that material should be as gracile and light as possible.  The lunar environment is more forgiving than Earth's in terms of physical weathering.
« Last Edit: January 05, 2018, 01:09:40 PM by JayUtah »
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Offline Glom

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Re: How was LM insulation attached?
« Reply #4 on: January 05, 2018, 01:40:24 PM »
Yes, but how did they know there were no spear throwing aliens?

Offline raven

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Re: How was LM insulation attached?
« Reply #5 on: January 05, 2018, 02:09:32 PM »
Yes, but how did they know there were no spear throwing aliens?
That's what Surveyor was really for.

Offline inconceivable

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Re: How was LM insulation attached?
« Reply #6 on: January 05, 2018, 02:54:26 PM »
Can that flimsy material could have survived an S-1C outboard engine cutoff of 3.439876gs?  diy1
« Last Edit: January 05, 2018, 03:29:36 PM by inconceivable »

Offline Zakalwe

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Re: How was LM insulation attached?
« Reply #7 on: January 05, 2018, 03:05:21 PM »
I'm not sure that flimsy material could have survived an S-1C outboard engine cutoff of 3.439876gs,

Why not?
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Offline Jason Thompson

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Re: How was LM insulation attached?
« Reply #8 on: January 05, 2018, 03:38:38 PM »
I'm not sure that flimsy material could have survived an S-1C outboard engine cutoff of 3.439876gs,

I hold out little hope you'll answer this, since your record of resonding is so abysmally low, but why would a flimsy material not survive? What would cause it to fail? Flimsy is also light, so a 3.5g acceleration doesn't put much stress on it.

Incidentally, 3.5g sounds a lot when you think of its effect on you, suddenly having to bear 3.5 times your own weight on bone and muscle not designed to do so, but you can impart well over 3.5g to some 'flimsy' material just by waving it around.
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Offline apollo16uvc

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Re: How was LM insulation attached?
« Reply #9 on: January 05, 2018, 04:13:29 PM »
I also endorse ANR.  Let me also recommend Scott Sullivan's Virtual LM and the always venerable Chariots for Apollo.  But let me also give an answer off the top of my head, from accumulated knowledge.

I also can't endorse Jason's point enough.  All of them.  If you saw a lunar module without its clothes on (and there are plenty of pictures from various sources) you'll see a surprisingly robust aluminum skin-and-stringer construction.  That provides the structural strength -- quite a lot of it.  The thermal and other requirements then get to be satisfied by other materials that don't also have to contribute to the structure.  This is what you get to do when your spacecraft doesn't need to withstand fluid flow against and around its outer skin.  Contrary to lay misconceptions, films, film blankets, and coatings work best for this.  The goal is to save weight.  I'm surprised that people are surprised by film blankets.  Quite a lot of spacecraft at the time and subsequently have outer skins made of blanket or various metalized films.  The LM is not out of the ordinary.

Last part first.  People wonder about the tape.  Yes, it's tape.  But it's not household masking tape or duct tape or anything so pedestrian.  Laymen are always flabbergasted to learn that industrial versions of tape exist.  The most common is "speed tape," thin aluminum sheeting backed with industrial-strength pressure-sensitive adhesive.  What you see on the LM is likely Mylar or Kapton tape.  That too has an industrial-strength pressure-sensitive adhesive.  Adhesives that strong are not routinely sold to the general public because of how the general public generally behaves.  Yes, it can stick ferociously to skin.  Tape is used in high-end engineering for precisely the same reasons it's useful around the house.  It's often the best way to fasten two things together.  Seaming two sections of a blanket or thin sheeting isn't best done with a piercing fastener, as tearout would inevitable result.  Tape spreads the load properly.

Attachment to the LM secondary frame, however, sometimes used properly protected piercing fasteners, usually to a standoff that kept the blanket the proper distance from the inner pressure vessel.  This is nearly identical to the way insulation blankets are laid up on airliners.  Not all of that is visible from the outside of the LM.

The various materials for the film blankets, e.g., aluminized Kapton, come on rolls.  Manufacture is merely a matter of unrolling the materials onto a table to build up the layers (in a properly controlled environment, of course).  Some blankets have layer-contact constraints, which means each layer has to be crinkled randomly so that it doesn't make full contact with its neighbors.  As this was most effectively done by hand, the size of the resulting blanket stock was limited.  This is why the outer skin had to be assembled in patchwork fashion.  You gain nothing by trying to cut patterns in the material before lamination.  It's just as effective -- and far easier -- to custom-cut the finished blanket and then join the patches with tape.

If you examine LM-2 closely, you'll see that its aft equipment bay covers are neatly screwed into the secondary structure via correctly-space overlapping eyelet holes and proper grommets.  That's how you'd design it "properly."  But you see LM-5's AEB covers just taped on.  That's how I'd expect the design to turn out after several passes of design review with attention to manufacturability and weight savings.

The lunar environment is not "hostile" in all the ways the Earth's is and then some.  It's just more hostile in some ways and more forgiving in others.  When you have no air, and you have a piece of material whose only job is to keep the sun from shining on something -- not fend of spear-throwing aliens or giant squids -- then that material should be as gracile and light as possible.  The lunar environment is more forgiving than Earth's in terms of physical weathering.

Hello JayUtha,

Thank you for a very comprehensive and detailed answer, but I have something that does not entirely agree with you. I'd like your thoughts on it:

From your post: "you'll see a robust aluminum skin-and-stringer construction."

Why did an astronaut say that a screwdriver could be dropped through the floor?
I am talking about the following quote:

“Whenever I saw a model of the lunar module, it had these rigid sides and [it] really looked strong. Turns out that external portions of the lunar module are made up of Mylar and cellophane and it’s put together with Scotch tape and staples. We had to have pads on the floor ‘cause if you dropped a screwdriver, it would go right through the floor.” – Jim Lovell, Astronaut (Gemini 7, Gemini 12, Apollo 8, Apollo 13)

Regards,
apollo16uvc

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Offline Jason Thompson

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Re: How was LM insulation attached?
« Reply #10 on: January 05, 2018, 04:34:31 PM »
From your post: "you'll see a robust aluminum skin-and-stringer construction."

Why did an astronaut say that a screwdriver could be dropped through the floor?

Because dropping a fairly heavy, hard, steel implement with a pointy end on the floor in 1g will impart more force than the metal can withstand if it happens to land point down, but since heavy sharp tools were in limited supply in use in the LM, and since they were never used in 1g anyway, this isn't an issue.

The LM pressure vessel is 'robust' in the sense that it is thicker than any of the outer layers, machined and welded metal, ribbed for structural rigitity, and more than capable of holding an atmosphere within it. In other words, nothing at all like the outer layers you can see in the pictures.
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Offline JayUtah

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Re: How was LM insulation attached?
« Reply #11 on: January 06, 2018, 02:09:29 PM »
I can stab a screwdriver through a B-17 bomber's skin.  The poke test really isn't relevant, but it does tend to impress the public.

The skin portion is very thin, but the combination of skin and stringers -- the stringers in this case being milled integrally as part of the skin -- makes for considerable strength along the stringer dimensions.  The primary structure is two milled bulkheads (similar to the shapers in the space shuttle orbiter) connected by two very robust ventral beams and a large overhead with gussets taking the load from the docking structure.  The LM structure was quite rigid and strong for its mass.
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Offline JayUtah

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Re: How was LM insulation attached?
« Reply #12 on: January 06, 2018, 02:18:18 PM »
Can that flimsy material...

Who said it was flimsy?  Have you ever worked with Kapton?  Have you ever worked with Kapton or Mylar tape?  I can do chin-ups from straps made of that stuff.  Just because it's a film doesn't mean it's not strong.

Quote
...could have survived an S-1C outboard engine cutoff of 3.439876gs?  diy1

Easily, and then some.  The insulation blankets are quite light.  Since the effect of deceleration is largely a function of the masses of the affected bodies, the very lightweight insulation blankets are the least of your problems.  People tend to think of loads arising only from thrust.  You routinely get much higher momentary or periodic g loads during a normal ascent from lateral and longitudinal vibration.
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Offline apollo16uvc

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Re: How was LM insulation attached?
« Reply #13 on: January 06, 2018, 03:32:42 PM »
I can stab a screwdriver through a B-17 bomber's skin.  The poke test really isn't relevant, but it does tend to impress the public.

The skin portion is very thin, but the combination of skin and stringers -- the stringers in this case being milled integrally as part of the skin -- makes for considerable strength along the stringer dimensions.  The primary structure is two milled bulkheads (similar to the shapers in the space shuttle orbiter) connected by two very robust ventral beams and a large overhead with gussets taking the load from the docking structure.  The LM structure was quite rigid and strong for its mass.
If the LM's skin was so thin that a screwdriver could fall through it, how did astronauts ever reside and work in it during the missions? The astronaut talks about the LM pressure shell floor, not the outer insulation.
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Offline Jason Thompson

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Re: How was LM insulation attached?
« Reply #14 on: January 06, 2018, 03:50:45 PM »
If the LM's skin was so thin that a screwdriver could fall through it, how did astronauts ever reside and work in it during the missions? The astronaut talks about the LM pressure shell floor, not the outer insulation.

As Jay (and I, incidentally) said, being able to poke a hole through something with a hard, pointy implement doesn't much indicate its structural strength. I can poke a hole through a plastic coke bottle with a screwdriver, but it can still hold a pressurised carbonated drink and withstand being hit with a hammer, or being dropped on the floor from a few feet.

The main question really is why you (or anyone else) thinks that in normal use anyone or anything is going to poke the inner skin of the LM with enough force to pierce it.
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