ApolloHoax.net

Apollo Discussions => The Hoax Theory => Topic started by: Everett on September 05, 2019, 10:26:10 AM

Title: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Everett on September 05, 2019, 10:26:10 AM
One common argument for the landings being faked is the whole "The LM was made of aluminum foil and tape!" thing. Here's some good counterarguments. "Well, the De Havilland Mosquito (a WWII airplane) was made out of balsa, and could fly at 400 mph. It's as true as the LM being made out of foil." (Posting a picture is good.) (Ironically, it's actually more true than LM was made out of foil bit. The Mosquito was effectively made out of what was in many ways an early version of composite materials, except using wood products, and IIRC, balsa was one of them.) Another good thing to point out is that foil like that is used extensively on satellites and planetary probes.
Even I was surprised to learn they used tape to attach the Kapton? foil. I would have assumed they would have glued it to the underlying structure. But it was explained to me quite well - what is tape, but a piece of material with glue on one side? That pretty much immediately led to an "ah, now I understand" moment. The tape is just a piece of material across a joint was glue on one side. Another thing to bring up is that the "foil" is just an outer covering to keep the sun off, and actually is somewhat flimsy. But then again, with no air resistance, it didn't need to be strong, The actual structure was underneath it, and was plenty strong enough. (Post a picture of a LM under construction without the outer covering attached.) Another point is that the actual cabin the astronauts were in was about the thickness of a beverage can. So, IIRC (I think) was the outside of a B-17.

One final good thing to do would be to turn the question around, and ask a HB what a lunar lander should look like, or how they would design one. Hopefully that would occasionally lead to a bit of thinking,

(PS: About the Kapton tape, would common duct tape have been strong enough for that application? Just something I recently wondered about.)
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: BertieSlack on September 05, 2019, 10:59:05 AM
I think I'm right in saying that the only bits of the pressurised crew cabin that are visible from the outside are the windows and the hatches. What you see is basically thermal insulation and the micrometeoroid shield - which are not necessary for the structural integrity of the vehicle. The frame, substructure and crew cabin were made of titanium and aluminium sheeting, and were strong enough for a vehicle that didn't have to deal with aerodynamic loads. With the layers of insulation stripped off, the LM looked like this:

https://i.stack.imgur.com/o8hnx.jpg

It's also worth remembering that LM was built by Grumman - who also made the F-14 Tomcat.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: bknight on September 05, 2019, 02:22:37 PM
An image is worth a thousand words, and I wish they would have never said you could punch a hole in the LM (insulation) in my mind propagating such hoax beliefs.  Similar to
Mr. Smith video a couple of years back where is describing the task of venturing through the VARB, when Apollo did tha by skirting the less dense parts, but we all know how the CT crowd viewed this video.  A follow up video showing the interior of Orion went a long way to correct the poor language choice in the first.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Mag40 on September 05, 2019, 02:33:19 PM
"The LM was made of aluminum foil and tape!" thing. Here's some good counterarguments.

Here is a better one. No it wasn't.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Allan F on September 05, 2019, 03:44:41 PM
The LM had thicker pressure-bearing walls than a soda can.

A soda can holds 30 psi - the LM had to hold 5 psi.

Also, al commercial airliner has thinner pressure-bearing walls than the LM - and carries greater pressure differential over a much larger area.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: apollo16uvc on September 05, 2019, 04:26:02 PM
The LM had thicker pressure-bearing walls than a soda can.

A soda can holds 30 psi - the LM had to hold 5 psi.

Also, al commercial airliner has thinner pressure-bearing walls than the LM - and carries greater pressure differential over a much larger area.
The sodacan has the benefit of a geometrically strong shape (Cylinder)

The LM does not.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Allan F on September 05, 2019, 05:42:38 PM
No, but the LM had a lot of ribs for structure. More per hull area than an airline. The can has none.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: raven on September 05, 2019, 06:38:52 PM
No, but the LM had a lot of ribs for structure. More per hull area than an airline. The can has none.
It's ribbed for her pressure.  ;)
***
OK, jokes aside, the 'foil and tape' crowd obviously have never looked at many satellites and landers for non-atmospheric objects.
And, I'm not an engineer, but the habitable pressure vessel (https://i.pinimg.com/originals/9a/8e/39/9a8e39280c1d1607c1a3bc2c8cc68d2d.gif) portion of (https://i.pinimg.com/originals/f6/40/7d/f6407df8a63f31bd766575b0041d4ad7.gif) the LM (https://i.pinimg.com/originals/49/f6/65/49f6652a77cb819328bea7f0169c84de.gif) looks fairly cylindrical even so. Not perfectly,  people don't walk very well across curved floors usually, but it's taking advantage of the shape where it can.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Abaddon on September 05, 2019, 11:44:15 PM
There is no way thin fragile flesh could possibly contain all of the messy organs while retaining verticallity, therefore people cannot exist.

Same argument.

Why the crank fraternity are so impressed by it is anyone's guess.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Matt D on September 06, 2019, 02:29:04 PM

Curiously, the "tinfoil LM" crowd never seem to provide a physical description of what a "believable" LM would in fact look like.  I assume they want it to be silver, shiny, and vaguely bullet-shaped - like something out of Buck Rogers - and since the historical LM does not look like that, then the only logical conclusion is that it's fake.   

This line of argumentation also nicely exemplifies the classic hoax believer paradox; namely that NASA is simultaneously 1) capable of faking anything imaginable with their bottomless resources, and 2) hopelessly inept at faking things.

Hoax believer: "Of course the cloud patterns on earth seen in Apollo photos match weather satellites from those same days - with all of the tax dollars that NASA steals, that would be dead simple for them to fake, even in the era of analog film and decades before the advent of Photoshop."

Also the hoax believer: "LOLOLOL, they mock up a trashcan from popsicle sticks and tinfoil and expect us to believe it can land on the moon?  I feel sorry for anybody who falls for this!" 
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 07, 2019, 12:19:46 AM
No, but the LM had a lot of ribs for structure. More per hull area than an airline. The can has none.

Integral stringers, a Grumman innovation. They used a chemical milling process to create them in the curved shapes needed for composing the pressure vessel.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 07, 2019, 12:22:31 AM
Regarding tape, pressure-sensitive adhesives can be amazingly strong.  We just don't produce them for the public for liability reasons.  We use polyamide tape with adhesives that are strong enough to hold my weight.  Engineers use tape for the same reasons non-engineers find tape convenient and appropriate.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Everett on September 07, 2019, 11:03:13 AM
What I meant was that the outer thermal/micrometeorite shield wasn't particularly sturdy, but with no air in space, didn't need to be. The actual structure however was, but you can't see it from the outside, it's under the outer layers. Then  again, everything did need to be stressed for +3 G's to survive loads during launch. (I think.) The picture that BertieSlack posted pretty much counters the "too flimsy" argument all be itself. (Question - was the descent module outer thermal/micrometeorite shield a separate layer away from the structure, or was it right up against/attached to/backed by the structure? I'd assumed the former, but from the picture posed makes me wonder if it was the latter.) And some HB should take a look at what a modern satellite or probe looks like - just like the LM.

I'd also imagine that the typical HB assumes something like a typical Hollywood ship as well. Or alternately, for that matter, perhaps something like the Soviet equivalent to the LM, the somewhat more aerodynamic looking LK:
http://www.astronautix.com/l/lk.html

Also worth noting, don't forget the Grumman earned the nickname the "Grumman ironworks" during WWII for how sturdy its carrier aircraft were. It seems Grumman was the US Navy's preferred aircraft builder. Too bad Northrop Grumman doesn't seem to build planes much any more, or that so few combat aircraft types are produced nowadays there's not room for another contractor. Part of me wonders if letting McDonald Douglass be bought out by Boeing was a mistake. Now any tanker or other airliner derived military aircraft goes to Boeing by default, since heaven forbid that we license-build an Airbus!
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 07, 2019, 11:41:34 AM
The core structure of the LM ascent stage was extremely strong:  fore and aft milled frames connected at the bottom by two ventral beams and at the top by the extremely robust docking structure.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Abaddon on September 07, 2019, 02:00:11 PM
Regarding tape, pressure-sensitive adhesives can be amazingly strong.  We just don't produce them for the public for liability reasons.  We use polyamide tape with adhesives that are strong enough to hold my weight.  Engineers use tape for the same reasons non-engineers find tape convenient and appropriate.
Interestingly, I have twice had occasion to deploy two part epoxy resin this last two months. The sad victims could not fathom why "Superglue" failed, but resin did not.  I could have diverted into a diatribe about evap versus chemical reaction adhesives, but I chose to avoid that madness, "It works, that is all."
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: NthBrick on September 07, 2019, 05:37:51 PM
Regarding tape, pressure-sensitive adhesives can be amazingly strong.  We just don't produce them for the public for liability reasons.  We use polyamide tape with adhesives that are strong enough to hold my weight.  Engineers use tape for the same reasons non-engineers find tape convenient and appropriate.

Just to provide a bit of backstory, I interned at an engineering company for the first 7 months of this year. At that, I pretty regularly worked with materials of (to me, anyways) unexpected strength and durability. Point being, a lot of people don't realize that most materials have an "industrial" version that is far stronger and more expensive than the commercial products they're used to.

For HBs, this sort of ignorance manifests turns what could be a cool question and interesting discussion of how Apollo engineers solved a particular problem into proof of the hoax. There's rarely any desire to actually how understand how or why things were done a certain way. Hence judging the LM by its cover in the most literal sense.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 07, 2019, 05:57:39 PM
Point being, a lot of people don't realize that most materials have an "industrial" version that is far stronger and more expensive than the commercial products they're used to.

And often more dangerous, which is why they aren't available to the public.  There are pressure-sensitive adhesives that will bond to skin strongly enough that it will tear the skin if you try to remove it.  This is by no means limited to "exotic" professions like engineering or high-end manufacturing.  I hired a professional janitorial company to clean one of my rental units that had seen some heavy use.  Even after I applied consumer-grade cleaning products, a large amount of soil, rust, and so forth were still present.  The crew came in and left it spotless.  How?  Because they had access to chemicals that require substantial training to use safely.  Or in other cases, the common chemicals that are sold in much higher concentrations to trained professionals.

But let's not lose Everett's point.  The parts of the LM you see -- generally the insulation blankets -- are not meant to have much if any structural robustness.  And if you saw poor LM-2 before its restoration, you'd agree.  And without an atmosphere, there was little to harm it.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: NthBrick on September 07, 2019, 06:39:48 PM
Point being, a lot of people don't realize that most materials have an "industrial" version that is far stronger and more expensive than the commercial products they're used to.

And often more dangerous, which is why they aren't available to the public.  There are pressure-sensitive adhesives that will bond to skin strongly enough that it will tear the skin if you try to remove it.  This is by no means limited to "exotic" professions like engineering or high-end manufacturing.  I hired a professional janitorial company to clean one of my rental units that had seen some heavy use.  Even after I applied consumer-grade cleaning products, a large amount of soil, rust, and so forth were still present.  The crew came in and left it spotless.  How?  Because they had access to chemicals that require substantial training to use safely.  Or in other cases, the common chemicals that are sold in much higher concentrations to trained professionals.

But let's not lose Everett's point.  The parts of the LM you see -- generally the insulation blankets -- are not meant to have much if any structural robustness.  And if you saw poor LM-2 before its restoration, you'd agree.  And without an atmosphere, there was little to harm it.

Indeed on both points. What Everett is saying has basically been my response to people playing the "aluminum foil and tape" claim. When you take the design of the LM, and place it in the context of the environment that it was designed to operate in (low gravity, vacuum, needing to be light enough to make it there and take off again), it goes from awkward-looking spider-thing to a true testament to the skill of the design engineers. Understanding significantly increases appreciation.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: ka9q on September 08, 2019, 06:03:08 AM
(Question - was the descent module outer thermal/micrometeorite shield a separate layer away from the structure, or was it right up against/attached to/backed by the structure? I'd assumed the former, but from the picture posed makes me wonder if it was the latter.)
According to the manuals, the thermal/micrometeroid shield was mounted on standoffs that kept it at least 0.5 inches away from the structure.

This would have formed a Whipple shield. Wikipedia has a reasonably good article on them.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: AtomicDog on September 08, 2019, 09:09:13 AM
I wish writers would stop using the words "ungainly" and "awkward looking" to describe the Lunar Module. For the environment it was designed to work in, the LM was very elegant, agile, and robust.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: NthBrick on September 09, 2019, 04:23:27 PM
I wish writers would stop using the words "ungainly" and "awkward looking" to describe the Lunar Module. For the environment it was designed to work in, the LM was very elegant, agile, and robust.

That it was well designed for the intended environment really is something that needs to be emphasized better. It's like why aircraft, cars, boats and submarines have different design characteristics, and none would operate well attempting to fill the place of any others.

I'm sure others have already written phenomenal pieces on the subject already, but there's a part of me that thinks researching and writing about the design of the LM with respect to the intended environment would be a lot of fun and could dispel a lot of hoax claims.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Abaddon on September 09, 2019, 04:50:57 PM
Regarding tape, pressure-sensitive adhesives can be amazingly strong.  We just don't produce them for the public for liability reasons.  We use polyamide tape with adhesives that are strong enough to hold my weight.  Engineers use tape for the same reasons non-engineers find tape convenient and appropriate.

Just to provide a bit of backstory, I interned at an engineering company for the first 7 months of this year. At that, I pretty regularly worked with materials of (to me, anyways) unexpected strength and durability. Point being, a lot of people don't realize that most materials have an "industrial" version that is far stronger and more expensive than the commercial products they're used to.

For HBs, this sort of ignorance manifests turns what could be a cool question and interesting discussion of how Apollo engineers solved a particular problem into proof of the hoax. There's rarely any desire to actually how understand how or why things were done a certain way. Hence judging the LM by its cover in the most literal sense.
Hello and welcome.

I have reason to deploy two part epoxy resin from time to time and what is fascinating (scuse pun) is how amazed people are at how such adhesives far out perform any "superglue".

The working model seems to be that if Cyanoacrylate can glue my fingers together, it can glue anything together.

Well, no. Pick the adhesive appropriate to the task at hand. Thus Kapton was appropriate for the thermal blankets. Not rocket science. Or is it?
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: bobdude11 on September 09, 2019, 05:20:04 PM
Regarding tape, pressure-sensitive adhesives can be amazingly strong.  We just don't produce them for the public for liability reasons.  We use polyamide tape with adhesives that are strong enough to hold my weight.  Engineers use tape for the same reasons non-engineers find tape convenient and appropriate.

As Red Green always says:
 "The Handyman's' Secret Helper: Duct Tape"
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: bknight on September 09, 2019, 09:22:57 PM
If you can't fix it with duct tape or bailing wire, it isn't worth having.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 09, 2019, 09:29:15 PM
All this is true, except (as I said) I prefer theatrical gaffer's tape as the fix-all solution.  But keep in mind that the argument was that the LM should have been a carefully designed, carefully manufactured spacecraft.  That parts of it appeared to be taped together, as one would expect from a low-cost, low-effort handyman's solution, seems suspicious to people who can see a pretty obvious parallel.

Yes, we use tape that's not like the tape you buy in hardware stores.  And yes, we use thin films.  All of these have proper engineering explanations.  Tape is better than a piercing fastener when dealing with laid-up blankets, because such a fastener would concentrate any mechanical loads on the fastener points.  That's more acceptable with more robust materials like sheet metal.  But tape is actually the best solution for mounting films in that way.  It spreads out the mechanical load.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: NthBrick on September 09, 2019, 10:00:52 PM
Hello and welcome.

I have reason to deploy two part epoxy resin from time to time and what is fascinating (scuse pun) is how amazed people are at how such adhesives far out perform any "superglue".

The working model seems to be that if Cyanoacrylate can glue my fingers together, it can glue anything together.

Well, no. Pick the adhesive appropriate to the task at hand. Thus Kapton was appropriate for the thermal blankets. Not rocket science. Or is it?
Thank you, I've gotten a lot of good information lurking on this forum, and hope to contribute to some degree (though doubtless the more senior members, degreed engineers in particular, will do most of the heavy lifting).

It's funny that you bring up two-part epoxy, as I spent a lot of time working with it to make fiberglass composite parts for test aircraft. Really nasty stuff to work with, but if you're careful and diligent you can create some very sleek, strong parts. Granted, they probably wouldn't stand up to being hit with a sledge hammer, but there were light-weight and bore the loads they were designed for.

Now that I think about it, the PLSS had a fiberglass micrometeoroid cover, page 1 and paragraph 1 of the right hand column: https://www.hq.nasa.gov/alsj/LM15_Portable_Life_Support_System_ppP1-5.pdf

I'd need to do the math to get a more exact value, but I have no problem believing that a couple layers of fiberglass would provide a serious barrier to micrometeoroids. We used a 7-layer tube to contain a black powder parachute charge multiple times.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 09, 2019, 10:07:03 PM
Indeed, I was focusing on pressure-sensitive adhesives since we were focusing on tape.  But if we widen the field to include all adhesives, there are some scary-strong bonds achievable with binary adhesives, light- and heat-cured adhesives, and some molecular stuff that goes beyond my knowledge of chemistry to explain.  For years and years the wing spars in Boeing airframes were laminated glue-ups.  What's that epoxy they use to bond new concrete to old?  Here in the U.S. it has a designation of the form J-<number>, but I don't recall the details.  I swear that stuff can glue smoke to air.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Abaddon on September 10, 2019, 07:06:47 PM
  I swear that stuff can glue smoke to air.
Hahaha. Brilliant.

I suspect the so-called "layman" has experience of OTC corner store adhesives and their general failings. Likely, they have not much awareness of how much of a pile of variability adhesives actually are, nor which is applicable to what task.

I find it fascinating how people think they can buy a tube of "super-glue" and it will stick anything to anything infallibly. 
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: bknight on September 11, 2019, 10:52:52 AM
All this is true, except (as I said) I prefer theatrical gaffer's tape as the fix-all solution.  But keep in mind that the argument was that the LM should have been a carefully designed, carefully manufactured spacecraft.  That parts of it appeared to be taped together, as one would expect from a low-cost, low-effort handyman's solution, seems suspicious to people who can see a pretty obvious parallel.

Yes, we use tape that's not like the tape you buy in hardware stores.  And yes, we use thin films.  All of these have proper engineering explanations.  Tape is better than a piercing fastener when dealing with laid-up blankets, because such a fastener would concentrate any mechanical loads on the fastener points.  That's more acceptable with more robust materials like sheet metal.  But tape is actually the best solution for mounting films in that way.  It spreads out the mechanical load.

I'm not familiar with gaffer's tape, but you work with all these kinds of tapes and if you recommend it, somebody lurking in the wings should pay attention.  8)
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 11, 2019, 11:08:58 AM
I'm not familiar with gaffer's tape, but you work with all these kinds of tapes and if you recommend it, somebody lurking in the wings should pay attention.  8)

I guarantee you've seen it.  It's the black cloth tape that electricians and other technicians in film and theater ("gaffers") use to tape cables down.  It actually comes in different colors, but black is by far the most common.  The substrate is a cloth duck, so it's very durable.  It can be torn with the fingers.  It's electrically insulating and able to endure quite high heat.  The adhesive releases easily from any surface, but it sticks quite well in the meantime.  The disadvantage is cost.  A large roll of high quality gaffer tape will set you back about $12.  Our theater buys it by the case, so I get a deal.

But as with duct tape and the home handyman, gaffer tape is the go-to way to temporarily repair almost anything in the film and theater world.  Gray gaffer's tape, manufactured by Shurtape, was what was carried on the Apollo missions.  Apollo 13's LiOH canister adapter was rigged using gaffer tape.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: bknight on September 11, 2019, 11:30:42 AM
I'm not familiar with gaffer's tape, but you work with all these kinds of tapes and if you recommend it, somebody lurking in the wings should pay attention.  8)

I guarantee you've seen it.  It's the black cloth tape that electricians and other technicians in film and theater ("gaffers") use to tape cables down.  It actually comes in different colors, but black is by far the most common.  The substrate is a cloth duck, so it's very durable.  It can be torn with the fingers.  It's electrically insulating and able to endure quite high heat.  The adhesive releases easily from any surface, but it sticks quite well in the meantime.  The disadvantage is cost.  A large roll of high quality gaffer tape will set you back about $12.  Our theater buys it by the case, so I get a deal.

But as with duct tape and the home handyman, gaffer tape is the go-to way to temporarily repair almost anything in the film and theater world.  Gray gaffer's tape, manufactured by Shurtape, was what was carried on the Apollo missions.  Apollo 13's LiOH canister adapter was rigged using gaffer tape.

And here I thought it was duct tape, but as per normal I learn something again that I didn't know.  :)
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 11, 2019, 11:36:43 AM
And here I thought it was duct tape, but as per normal I learn something again that I didn't know.  :)

Back in the day, duct tape was closer to gaffer tape than it is now.  The tape I've removed from old ducts (with full PPE, because asbestos) is close enough to gaffer tape to be essentially the same product sold under different names.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: ka9q on September 12, 2019, 11:52:00 AM
Speaking of the tape used to hold the thermal blankets on the LM, it was almost certainly Kapton. That's the DuPont trademark for a polyimide plastic. It has an orange color, the darkness depending on the thickness. Kapton's forte is its ability to withstand a very wide temperature range.

You can readily buy it today. I have a roll of it somewhere that I've used on our high altitude student balloon experiments. It gets very cold up there.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 12, 2019, 01:15:32 PM
Speaking of the tape used to hold the thermal blankets on the LM, it was almost certainly Kapton.

Not almost certainly, definitely certainly.  That was one of the boons of rehabilitating poor LM-2.  Some of its constituent components were still being made and sold -- namely, Kapton tape.  And yes, one can get it in varying degrees of stickiness.  I admit I probably went down the rabbit hole of pressure-sensitive adhesives and their varying availability.  There's no engineering requirement I'm aware of that specified a tape for the LM that was stickier than an over-the-counter version.  You can literally buy this stuff at Home Depot.  That doesn't make it unsuitable for aerospace.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Count Zero on September 15, 2019, 08:47:09 AM
I've always thought that looking at the outside skin of the Lunar Module, and deciding that it's construction is too flimsy was just plain weird.  This makes no sense.  Do they think their shirt is holding them upright in their chair?  No?  What about their skin - is that holding them up?

What is important is what's under the skin, so let's have a look at what's under the LM's skin:

(http://www.hq.nasa.gov/office/pao/History/alsj/misc/apmisc-LM-noID-13.jpg)
Here it is one on the factory floor at Grumman Aviation in Long Island.
To the left is the Descent Stage.  Note that it is not actually octagonal, but rather is five box structures welded together, with vertical reinforcements rather like a wine box.  This provided fantastic vertical strength for the mass of material used; allowing it to support the weight of the Ascent Stage during Saturn V liftoff, and also for it to serve as a launch pad for the AS when it takes off.

To the right is the Ascent Stage.  You can see that the inner skin of the pressurized crew cabin is supported by closely-spaced ribs for maximum strength at minimum weight.  One of the ascent fuel tanks is visible to the right.

(http://www.hq.nasa.gov/office/pao/History/alsj/misc/apmisc-LM-noID-16.jpg)
Here is the Ascent Stage of the LM,viewed from the right-rear.  To the right (partially obscured) is the drum-like crew compartment.  To the left is the aft electronics bay.  You can see the thin stringers from which the outer skin will hang, but don't get them confused with the much sturdier structural framework underneath that you can see supporting the AEB and oxidizer tank.

(http://www.hq.nasa.gov/office/pao/History/alsj/misc/apmisc-LM-noID-06.jpg)
Here's another view of the Descent Stage, showing its rugged construction.  The descent fuel & oxidizer tanks are inside the boxes.  The triangular sections between the outer boxes were storage areas for auxiliary tanks and equipment the astronauts would need on the Moon, including tools, science packages and, on the later missions, the folded-up lunar rover.

Grumman, whose proud engineers (http://www.ehartwell.com/LM//index.htm) built the Lunar Module, also built the best and most durable naval aircraft ever - they didn't do flimsy.

(http://www.hq.nasa.gov/office/pao/History/alsj/misc/apmisc-LM-noID-19.jpg)
When I first saw pictures like this, I thought that they had formed the skin to the right shape, and then added the ribs, or that they built the rib framework and the attached the inner skin to it, like you would build a ship.

The reality is far more interesting and clever (and stronger):  The skin & ribs are a single block of aluminum!  They milled-down the sections between the ribs to the desired skin thickness.  They did this for each section of hull, then welded the sections together at strong edges.

Here are pictures of the pieces coming together (http://www.longislandaerospacehistory.com/Select/SCAT/slide2.htm) (click on the little blue arrow on the right to page through each pic).

Grumman went onto use the same technique to build the F-14 Tomcat.

Hope this helps

 8)
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 15, 2019, 01:20:17 PM
What is important is what's under the skin, so let's have a look at what's under the LM's skin:

This is why any LM fan needs to make a pilgrimage to Hutchinson, Kansas.  They have a LM ascent stage pressure hull you can inspect relatively up close.

Sadly none of these photos reveal the real structural design of the ascent stage.  This page is instructive.  http://heroicrelics.org/info/lm/lm-structural.html  Scroll to the Ascent Stage Midsection drawings, SK 17-31-18 (3 sheets).  These describe the central structural core of the ascent stage.  It's built very much like the wing box of a large airliner's airframe -- the thing that takes the brunt of aerodynamic loads in several directions.  The fore and aft frames of this box are machined frames.  You start with a slab of aluminum and machine away everything that's not a structural load path, leaving behind only a thin webbing between the bosses.  This is why aerospace is so expensive.  You start with a chunk of rather expensive metal and throw away 80 percent of it.  But the result is as light and strong as a frame can be.  The fore and aft frames are connected with a ventral beam assembly

See figure R-123 in the ANR:  https://www.hq.nasa.gov/alsj/LM19_LM_Manufacturing_ppB10-17.pdf

What's in this part of the LM?  Mostly the ascent engine and the environment equipment and controls.  The crew cabin is cantilevered out front of this structure, so that the crew and flight instruments balance the AEB to provide inherent pitch stability.

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To the left is the Descent Stage.  Note that it is not actually octagonal, but rather is five box structures welded together, with vertical reinforcements rather like a wine box.

We still build spacecraft chassis like this, where possible.  That is, we design them presuming they'll be made of a honeycomb sheet or other such material.  This is the aerospace equivalent of corrugated cardboard.  We can cut it into shapes, then we weld, glue, or bolt the shapes together, oriented in different cardinal directions, to build up the desired shape.  Not the outer boundary of the shape, but an internal wine-box  arrangement.  The electronics, propulsion, tankage, and what-not to support the spacecraft's mission are attached to these pieces.  Then the outer skin goes over that, which may or may not contribute to the overall structural design.

Grumman was well ahead of its time.

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To the right is the Ascent Stage.  You can see that the inner skin of the pressurized crew cabin is supported by closely-spaced ribs for maximum strength at minimum weight.

The skin-and-stringer method of building lightweight structures is no secret.  Everyone uses it.  The corrugated parts of the Saturn V show the interstage portions, where the skin is not being stiffened by pressurized propellant.  The stringers there were on the outside.  In the airplane designs of the time (and earlier), the stringers were on the inside.  Normally you assemble these out of sheet metal.  You cut strips of metal, bend them in a press brake, and then weld, rivet, or glue them to the skin (often made from the same material as the stringers).  It behaves like corrugated cardboard with one of the facing sheets removed.  it will bend very easily at right angles to the stringers, but remains exceptionally strong in the other direction.

For airplanes, the stringers are attached to the formers first, and then the skin is riveted or screwed on, usually from the outside.  In advanced expressions of this standard method, the skin takes a lot of the structural load.  So temporary fasteners called clecos are inserted in the rivet holes until the permanent rivets are installed.  Building an airliner is surprisingly like building a ship.  You lay a ship's keel.  You also lay an airliner's keelspar.  To the ship's keel you attach frames at intervals along the keel's length  These frames describe the shape of the ship as if it had been sliced at intervals moving fore and aft.  The shapers in an airliner's structure perform the same function.  Then between the frames/shapers you attach the stringers at intervals, and onto this, the skin.  The lunar module's longerons and stringers go every which way because there is very little other structure besides the skin and stringers at that point.  Internal structure of the cabin was more concerned with those blasted windows.

When you see the complicated shapes that the ascent stage had to achieve, you see that the typical skin-and-stringer assembly methods wouldn't really work anyway.  The stringers would have to attach at odd angles  There would be tight corners where rivet guns couldn't reach.  You could weld the skin together, but aluminum sheets that are thick enough to weld would be too heavy.  Enter chem-milling.  That's a process whereby you mask off certain parts of a sheet of material, then dip it in acid that eats away the unmasked portions to a carefully controlled depth.  So you cut a sheet of aluminum into the right shape, like a dress pattern.  Then you form if (if necessary) by rolling.  Then you chem-mill away the parts that don't need to be thick enough to weld, or to attach stringers to.  What you have is a thin plate of aluminum that is thick enough to weld or rivet, but only in exactly the places where it needs to be that thick.  Elsewhere it's only as thick as it needs to be to hold cabin pressure.

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You can see the thin stringers from which the outer skin will hang...

Minor nitpick:  I will argue those are struts, not stringers.  Yes, the thermal skin attaches to it, but its structural role here has it acting in longitudinal compression.  The thermal skin is about as thick as the sheet metal used in the U.S. to make HVAC ducts.

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The triangular sections between the outer boxes were storage areas for auxiliary tanks and equipment the astronauts would need on the Moon, including tools, science packages and, on the later missions, the folded-up lunar rover.

The end caps on the cruciform structure were for structural strength, not necessarily to protect (as with a skin) what was contained therein.  Because the struts for the landing gear attach there, the end caps resist the torsion load that would occur if the LM landed at a more acute angle than strictly planned.

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Grumman, whose proud engineers (http://www.ehartwell.com/LM//index.htm) built the Lunar Module, also built the best and most durable naval aircraft ever...

I had the pleasure of helping to restore an F-14 Tomcat when I was a volunteer at a small air museum in Oakland, California back in the 1990s.  Tom Kelly's team built that too.

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When I first saw pictures like this, I thought that they had formed the skin to the right shape, and then added the ribs...

The reality is far more interesting and clever (and stronger):  The skin & ribs are a single block of aluminum!  They milled-down the sections between the ribs to the desired skin thickness.  They did this for each section of hull, then welded the sections together at strong edges.

I've been saying that for years, so you're to be forgiven for repeating it.  But I've lately found out (after having a good close look at the construction) that the integrated skin-and-stringer method was used only for very small elements.  (I also asked some people, to confirm it.)  The larger ones, which comprise what you can see in the photos, were made in a semi-traditional way.  Which is to say, the skin and stringers were separate pieces.

As I said above, the only milling done on the skin was done chemically, and it was done to selectively reduce the thickness of the skin where not required.  The skin was 0.055 to 0.065 inch thick under the stringers, and somewhat thicker (I don't have an exact figure) at the edges where welding might occur.  The spaces between the stringers were only 0.015 to 0.025 inch thick.  (For comparison, a carbonated beverage can in the U.S. is 0.015 inch thick.)  The variable thickness was achieved by chem-milling.  The stringers were either formed or milled, depending on whether they were for flat or curved sections, and attached by various means.

The confusion is natural, even among engineers, because that's exactly how we make some of the formers.  As I said above, you start off with a slab and then mill it down to have just a very thin web between the thicker remaining parts that bear most of the load.  If you wanted to go extremely thin, past the point where mechanical milling is no longer feasible, you could conceivably use chemical processes to erode the material further, leaving essentially a large integrated skin and stringer component.  I don't know of anyone who does that, though.  Such a thing would be strong, though, that one in which the stringers are attached later.  This is because the loads passed between skin and stringer wouldn't be concentrated at attachments or weldments that would need to be thicker than the surrounding material to bear them.

I said semi-traditional methods.  The skin panels were typically welded together first, then the stringers were attached.  This is the reverse of the typical process.  In aircraft the stringers are longerons too, and are attached first to the formers.  In the Saturn V, the skin and stringers were assembled first as a large sheet, then formed into the shape of the rocket.

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Grumman went onto use the same technique to build the F-14 Tomcat.

It definitely shows.  Crawling around in the guts of one of those, you definitely see echoes of the LM.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: bknight on September 16, 2019, 10:59:42 AM
The start with a block of metal and mill away everything but the thin shell is astounding to me.  I continue to learn fact from this web site.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: Northern Lurker on September 16, 2019, 12:01:28 PM
I know metallic swarf from mechanic machining can be recycled. Can chem milled metal be reclaimed and recycled?
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 16, 2019, 12:23:36 PM
The start with a block of metal and mill away everything but the thin shell is astounding to me.  I continue to learn fact from this web site.

A lot of mechanical parts are made this way.  You start with a billet that's slightly thicker than the thickest part, face it (to create exactly parallel top and bottom surfaces), and then mill away large amounts of it.

Imagine the end cap to some casing for a mechanical assembly such as a gear train.  You could just have a plate cut to the right outline, with a hole for the shaft and smaller holes for the bolts.  And that's the cheap, simple way.  But let's say you wanted a bearing for the shaft.  You could allow the casing to be 50 mm thick there, but maybe only for a 15 mm radius beyond the shaft.  Then you want a similar buildup of material around the bolt holes.  The face material may not have to bear pressure.  It may only need to keep in the lubricant and keep out particle contaminants.  It may need to be only 3 or 4 mm thick.  But that's not strong enough to handle the loads between the shaft bearing and the bolt holes.  But because we know how stress acts in a material, we can allow thick ribs -- say 20 mm thick and 20 mm wide -- between the shaft bearing and the bolt holes.  This accomplishes the structural goals without all the weight.

Another related case for the same part would be if the part needed (or wanted) to be domed in some fashion.  Instead of a metal forming process, which may leave microfractures and weird stress effects, you would machine it out of a thickness of stock that can accommodate the dome.  It's like turning a wooden bowl on a lathe, only with possibly more complex geometry.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 16, 2019, 12:33:55 PM
I know metallic swarf from mechanic machining can be recycled. Can chem milled metal be reclaimed and recycled?

Yes, for certain values of "can."  Since the chemicals are difficult to handle and almost always toxic, any process that involves them is expensive and dangerous.  And the amount of metal you get out of the process is small; the goal is almost always to recycle the chemical for reuse.  The metals are generally present as ions in the solution and must be extracted chemically, usually also involving a fair amount of energy input.  This is different than simply sweeping up shop waste or emptying filters and washing off the lubricant materials for mechanical recycling.  Recycling the chemical baths is not always cost-effective.  But increasing attention to environmental concerns are changing that equation.  Recycling chemical consumables from engineering processes is kind of a hot button for research in academic engineering these days.  I'd like to think that Grumman did the responsible thing and properly recycled all its chemicals from the LM construction.  But it was the 1960s, so maybe.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: bknight on September 16, 2019, 01:57:12 PM
The start with a block of metal and mill away everything but the thin shell is astounding to me.  I continue to learn fact from this web site.

A lot of mechanical parts are made this way.  You start with a billet that's slightly thicker than the thickest part, face it (to create exactly parallel top and bottom surfaces), and then mill away large amounts of it.

Imagine the end cap to some casing for a mechanical assembly such as a gear train.  You could just have a plate cut to the right outline, with a hole for the shaft and smaller holes for the bolts.  And that's the cheap, simple way.  But let's say you wanted a bearing for the shaft.  You could allow the casing to be 50 mm thick there, but maybe only for a 15 mm radius beyond the shaft.  Then you want a similar buildup of material around the bolt holes.  The face material may not have to bear pressure.  It may only need to keep in the lubricant and keep out particle contaminants.  It may need to be only 3 or 4 mm thick.  But that's not strong enough to handle the loads between the shaft bearing and the bolt holes.  But because we know how stress acts in a material, we can allow thick ribs -- say 20 mm thick and 20 mm wide -- between the shaft bearing and the bolt holes.  This accomplishes the structural goals without all the weight.

Another related case for the same part would be if the part needed (or wanted) to be domed in some fashion.  Instead of a metal forming process, which may leave microfractures and weird stress effects, you would machine it out of a thickness of stock that can accommodate the dome.  It's like turning a wooden bowl on a lathe, only with possibly more complex geometry.

As a youngster, I did witness the finishing of a crankshaft from an piece that hand been poured, I guess, into a mold, left to harden.  After cooling then the machinist milled holes and then finished the bearing surfaces.  It was cool and much better IMO than taking one out of a junk yard and then replacing in the engine.
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: jfb on September 16, 2019, 02:52:52 PM
The start with a block of metal and mill away everything but the thin shell is astounding to me.  I continue to learn fact from this web site.

A lot of mechanical parts are made this way.  You start with a billet that's slightly thicker than the thickest part, face it (to create exactly parallel top and bottom surfaces), and then mill away large amounts of it.

Imagine the end cap to some casing for a mechanical assembly such as a gear train.  You could just have a plate cut to the right outline, with a hole for the shaft and smaller holes for the bolts.  And that's the cheap, simple way.  But let's say you wanted a bearing for the shaft.  You could allow the casing to be 50 mm thick there, but maybe only for a 15 mm radius beyond the shaft.  Then you want a similar buildup of material around the bolt holes.  The face material may not have to bear pressure.  It may only need to keep in the lubricant and keep out particle contaminants.  It may need to be only 3 or 4 mm thick.  But that's not strong enough to handle the loads between the shaft bearing and the bolt holes.  But because we know how stress acts in a material, we can allow thick ribs -- say 20 mm thick and 20 mm wide -- between the shaft bearing and the bolt holes.  This accomplishes the structural goals without all the weight.

Another related case for the same part would be if the part needed (or wanted) to be domed in some fashion.  Instead of a metal forming process, which may leave microfractures and weird stress effects, you would machine it out of a thickness of stock that can accommodate the dome.  It's like turning a wooden bowl on a lathe, only with possibly more complex geometry.

Every now and again a random video will show up in my YouTube feed demonstrating CNC and milling machines cutting out gears and parts from solid blocks of aluminum, and I'm always amazed by the following:


I'm one of those people who's less impressed by the building than by the crane used to build it.  When you look at the tools behind something, they're almost always far more interesting pieces of technology than what they build. 
Title: Re: "The LM was made of aluminum foil and tape!" - counterargument
Post by: JayUtah on September 16, 2019, 03:19:00 PM
The "cast-then-machine" fabrication steps have been de rigueur since probably the early 1800s.  I think the Periscope Films channel on YouTube is the one that has a lot of films on vintage industrial processes.

The cutting tools on the newer CNC machines are fantastically expensive.  The machines are amazing not only for their cutting power, but for the ability to zip through the manufacturing space with sub-mil accuracy.  The ability to stop milling, fly over to the tool crib, change tools, and fly back to the same place to a precision of 0.0001 inch blows my mind.