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  Apollo command modules: Kapton, outer color

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Author Topic:   Apollo command modules: Kapton, outer color
andyevertonfc
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posted 12-30-2005 06:35 AM     Click Here to See the Profile for andyevertonfc   Click Here to Email andyevertonfc     Edit/Delete Message   Reply w/Quote
Can anyone explain to me why the foil used on the exterior of the Apollo command module is very obviously silver in lunar orbit photographs (almost mirror like) yet becomes gold when returned to earth.

I have a piece of Apollo 11 foil which is without doubt, very definitely, gold!

Ken Havekotte
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posted 12-30-2005 07:18 AM     Click Here to See the Profile for Ken Havekotte   Click Here to Email Ken Havekotte     Edit/Delete Message   Reply w/Quote
All of the Apollo Kapton tapes, coated with aluminum and oxidized silicon monoxide, were "silver" and "gold" in color. As the pressure-sensitive polyimide tape was applied over the spacecraft's external ablator surfaces, the down-side of the Kapton was gold in color, with silver that you see exposed as the outermost layers.

During reentries, however, some of the Kapton was peeled and/or broke away from the Command Module spacecrafts, especially during a return voyage to the moon. When this did occur, it would look as though -- in many instances -- that much of the "gold" surfaces were in fact part of the outside layers... and even more so when a bright sun was overhead during an ocean recovery.

Take for instance most of the recovery pictures of Apollo 11's Columbia appear to show the Kapton as a gold color instead of silver. But rest assured, it was always silver -- not gold -- as the outermost layers of the thermal material.

andyevertonfc
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posted 12-30-2005 10:12 AM     Click Here to See the Profile for andyevertonfc   Click Here to Email andyevertonfc     Edit/Delete Message   Reply w/Quote
I've 'dismounted' my piece of foil (tricky procedure is in very big glass frame) and indeed it is silver on the reverse! Am I correct in assuming that the side exposed to space was the silver side? Why is it always displayed with the gold side forward?

Ken Havekotte
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posted 12-30-2005 12:53 PM     Click Here to See the Profile for Ken Havekotte   Click Here to Email Ken Havekotte     Edit/Delete Message   Reply w/Quote
Yes, you are correct, as the silver portion of the Kapton is the side that is directly exposed to the space environment. Even a couple of Apollo astronauts were in error about this same question. When displaying the thermal artifact material, the silver-coated Kapton should be displayed front-up while the gold-coated layer is the underside of the polyimide tape.

Danno
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posted 12-30-2005 11:38 PM     Click Here to See the Profile for Danno   Click Here to Email Danno     Edit/Delete Message   Reply w/Quote
Even though I knew that, I had to pick up my Cernan Apollo 17 acrylic (which correctly displays silver on front) and check out the other side. It is silver on the back side as well!

Any ideas on why that is?

andyevertonfc
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posted 12-31-2005 04:48 AM     Click Here to See the Profile for andyevertonfc   Click Here to Email andyevertonfc     Edit/Delete Message   Reply w/Quote
Have rechecked my 'swatch' (this is an excellent excuse to get it off the wall and wallow in the amazing joy of having something that was on Apollo 11). The swatch is about 3cm by 1 cm and the golden side shows some very minor scratching. The silver side appears more scratched, although these are very minor, almost showing the gold underneath in places.

Studying a photo of the command module recovery it seems that the golden colour appears to be caused by re-entry scorch marks. The lower section of the CM, near to the flotation collar, is very obviously silver.

Does anyone know if the kapton was applied in a single layer, or were there multiple layers?

randyc
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posted 12-31-2005 11:45 AM     Click Here to See the Profile for randyc   Click Here to Email randyc     Edit/Delete Message   Reply w/Quote
It's interesting that the Apollo 17 'Kapton' pieces in the acrylic do not have a gold backing because the first time I saw them my impression was that they looked more like pieces of crinkled aluminum foil and not Kapton.

I have seen Kapton from several other Apollo missions, and they all look the same. But the 'Kapton' from Apollo 17 is different from all of them (it does not have the gold backing, and it is thicker than the Kapton tape samples from the other missions).

It also appears that the underside is coated with a red adhesive that is not present in the other Kapton samples that I have seen.

Were there areas of the Command Module that had a different type of Kapton tape applied, or, if not, why do the Apollo 17 samples look different?

Ben
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posted 12-31-2005 12:36 PM     Click Here to See the Profile for Ben   Click Here to Email Ben     Edit/Delete Message   Reply w/Quote
Maybe the foil in those Apollo 17 lucites is not from the outside of the CM.

Danno
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posted 12-31-2005 01:24 PM     Click Here to See the Profile for Danno   Click Here to Email Danno     Edit/Delete Message   Reply w/Quote
Here is a response I received via e-mail:
The foil that is in the newer acrylics flown on Apollo 17 is not the exterior kapton polymide tape, it's a liner foil used under the outer ablator material and it's thicker than kapton foil. The thicker foil is silver on both sides, whereas the .00085 kapton foil is gold on the spacecraft side and silver on the outside surface.

Ken Havekotte
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posted 01-01-2006 06:31 PM     Click Here to See the Profile for Ken Havekotte   Click Here to Email Ken Havekotte     Edit/Delete Message   Reply w/Quote
About Apollo 17's Kapton lucites that were produced by the Cernan Corporation years ago, yes, indeed, this was another type of Kapton polyimide film. The pressure-sensitive thermal "tape" was applied in one, two and four-inch widths over the exterior of the Apollo CM-spacecraft. More "Kapton" and "Mylar" coatings, as came from Apollo 17, were used as well throughout the spacecraft.

The most extensive use of Kapton in space was on the Apollo Lunar Modules. Up to 27 layers of "Kapton" coated with a thin deposit of aluminum served as thermal insulation on the exterior of the moon ship.

This lightweight thermal control insulation protected both Apollo space vehicles from the extreme heat and cold of outer space by creating a multi-layer reflective barrier against the intense thermal insulation primarily because it does not burn, melt, or shrink excessively at high temperatures.

As an example of its ability to withstand heat: At 200 degrees C. -- a temperature at which most films have little tensile strength -- it would take 17,000 pounds per square inch of force to pull apart a sheet of Kapton one-thousandth of an inch thick.

There is another polyimide sheet material, known as Pyralin, that was used on the inner wall panels of the command ship.

mensax
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posted 01-04-2006 08:35 AM     Click Here to See the Profile for mensax   Click Here to Email mensax     Edit/Delete Message   Reply w/Quote
I've got a follow up question. It has been written that "Kapton, on the other hand, did have a 'mission requirement' in that it was one of the major thermal substances that was used to 'insulate' or protect our Apollo astronauts from excessive heat and cold while in space."

In an earlier posting that I made a while back someone replied with a comment about Kapton... "The reflective color on the cone of Apollo was a thin layer applied over the thermal protection system to improve the reflection of radar tracking waves, to help tracking at lunar distance."

So, are both comments true? I can see where on the Lunar Module many layers were used, with space in between, which would act as an insulating layer. But, on the command module it was just one layer tightly sealed to the craft... which it would seem would eliminate any insulating abilities of it. Certainly, it would seem that the reflective abilities of this material would reflect dangerous waves from the Sun.

So, my question is was the purpose of the Kapton on the command module to reflect damaging rays, and radar waves, and to insulate?

Ken Havekotte
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posted 01-06-2006 02:29 PM     Click Here to See the Profile for Ken Havekotte   Click Here to Email Ken Havekotte     Edit/Delete Message   Reply w/Quote
To my knowledge, I have never heard of any Kapton material from the Apollo program being used for any sort of radar tracking while in space. Tracking of the Apollo Command/Service Modules, to my understanding, had nothing to do with Kapton.

There is a NASA Technical Note (Report # TN D-7564) published in Jan. 1974 that discusses, in detail, about the whole Apollo Thermal Protection Subsystem that included the Kapton usage. As mentioned in some of my certification write-ups of the Du Pont-made thermal plastic film, the thermal control requirements for the Apollo ship modules in outer space necessitates a relatively low thermal absorbance-to-emittance ratio of 0.4 for the surface of the Command Module. This low ratio is achieved with a pressure-sensitive Kapton polyimide tape that is coated with aluminum and oxidized silicon monoxide. It was applied over, as you know, the entire external surface of the spacecraft's ablator.

Kapton was also used extensively in the Lunar Module and in the astronauts' suits made by ILC Industries. When Apollo astronauts explored the lunar surface, there were two inner layers of aluminized Kapton that helped protect the moonwalkers against temperatures from minus 250 degrees F. to 250 degrees F.

Another use of Kapton in space vehicles -- and still today in some instances -- is for electrical insulation on aerospace wire. The most extensive use was in the LM with more than 14 miles of wiring insulated with Kapton polyimide film.

Though Kapton has proven to be vital to space exploration, it was not developed specifically for that purpose. It is the result of a Du Pont Film Department exploratory research effort aimed at finding useful new materials. That effort began in 1955 at a Du Pont experimental station in Delaware and consisted of one chemist working in one laboratory.

If you can find more information about such a tracking radar usage of Kapton, I would certainly appreciate knowing more.

randyc
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posted 01-12-2006 07:48 PM     Click Here to See the Profile for randyc   Click Here to Email randyc     Edit/Delete Message   Reply w/Quote
I was looking at some photos that were taken during the Apollo 17 mission and found a closeup of the Command Module showing details of the Kapton insulation installation. What I saw surprised me, because in every photo that I had seen of the Command Module the outside surface had the appearance of polished chrome (see the photo below):

But when viewed closeup it actually looks like this:

Note the way it was applied around the window. Functionality was definitely more important than aesthetics!

andyevertonfc
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posted 01-13-2006 09:27 AM     Click Here to See the Profile for andyevertonfc   Click Here to Email andyevertonfc     Edit/Delete Message   Reply w/Quote
Stunning picture, never seen one like that before ...amazing detail.

rasorenson
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posted 07-14-2010 10:41 PM     Click Here to See the Profile for rasorenson   Click Here to Email rasorenson     Edit/Delete Message   Reply w/Quote
For all of the photos that exist showing Apollo Command Modules (CM) before, during and after flight, I still don't have a clear idea what the CM surface looked like before applying the mirrored silver reflector film.

I assume in it's "naked" state it was white. Museum CMs show specs of a white surface after all the burnt surface is cleaned off.

It seems once it left the factory, it was covered in a blue plastic shielding material which I assume was removed prior to the silver mylar or film application. What appears "shiny gold" after splashdown are scorched pieces of that silver film. Most the rest then appears to be a dull rust color of the actual metal surface.

Do you think we could put together a photographic sequence of the CM appearance from factory to splashdown?

Editor's note: Threads merged.

SpaceAholic
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posted 07-14-2010 10:49 PM     Click Here to See the Profile for SpaceAholic   Click Here to Email SpaceAholic     Edit/Delete Message   Reply w/Quote
Its "naked" color was that of Avcoat 5026 Ablator.

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