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Post by gwiz on Mar 23, 2007 10:06:44 GMT -4
In fact it relates to an old David Percy claim: the one where he says the United States decal on the side of the LM is improperly lit. He calibrates the overall lighting using the surrounding Mylar, which is mosly reflecting an image of the black sky, and says that there's no way the decal could be lit by enough light under those conditions. He attributes the blackness of the surrounding Mylar to the total lack of light striking it, not the relative lack of light reflecting from it to the camera. I think there was also some confusion due to his not realising that there had been a change in the pattern of thermal covering between the early and later missions, to the extent that a panel that was originally gold mylar was for the later missions replaced with mylar that actually had a black coating.
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Post by JayUtah on Mar 23, 2007 11:31:10 GMT -4
...with mylar that actually had a black coating.
H-film applied inside out. The aluminized Mylar blanket was used for general thermal and micrometeoroid protection. Next higher on the thermally-resistant scale is H-film, which (IIRC) is nickel-coated Mylar. It was applied with the nickel side out, producing a dull black appearance. And next higher is Inconel foil and/or mesh, applied where rocket plumes impinged directly. Inconel is a nickel alloy from which jet engine tailcones are often made.
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Post by Jason Thompson on Mar 23, 2007 13:21:58 GMT -4
Not that it matters to a conspiracy theorist. There is only foil, duct tape, and black stuff to them, and things either reflect or absorb. The idea that things do so in different degrees depending on their physical make-up just doesn't occur....
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Post by nomuse on Mar 23, 2007 18:08:19 GMT -4
Erm, I don't think they understand reflection very well, either. Most of the time it is undirectional, all-or-nothing; "If the astronaut is lit up, then the little rocks at his feet should be too!" or "You say it's a reflection of the lunar landscape. So why is this patch here black?"
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JMV
Venus
Posts: 41
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Post by JMV on Mar 23, 2007 23:56:52 GMT -4
Next higher on the thermally-resistant scale is H-film, which (IIRC) is nickel-coated Mylar. As I've understood it, H-film is a polyimide film also known by DuPont's trademark name Kapton. Mylar on the other hand is a polyethylene terephalate film, which is different from Kapton. Kapton also is indeed more thermally resistant than Mylar. Kapton is a transparent yellowish/amber colored film and apparently it's second-surface aluminized Kapton what gives modern spaceprobes their gold-like color in some parts. I'm not saying this is why LM is gold colored because according to this page second-surface aluminized Kapton hadn't been developed yet at the time of designing of the Galileo spacecraft. I've noticed that the Eagle descent stage had two shades of yellow on its thermal blankets. One more gold-like and the other more reddish or orange and less wrinkly as if the layer was made of stronger or thicker material. In some parts especially on the landing gear struts the orange material seems transparent as if there was more wrinkled reflective material underneath. I've assumed the orange stuff is Kapton whereas the more wrinkled yellow material is Mylar. I don't know for certain though. The narrow tape strips used on the thermal blankets also seems to be Kapton tape. I don't know what material the black layers of the thermal blankets are but the texture of them seems very similar to the texture of RCS plume deflectors, which according to this page are painted with black Pyromark paint. The paint apparently has absorbtivity of 0.95. If it reflects only 5% of incident light it should appear roughly as dark as the boulders in some of the Apollo pics. [EDIT: This goes a bit off-topic but it's a minor observation I wanted to share with you: Don't you just love how the hoaxters have "faked" the sandblasting effect of the descent engine and lunar dust. www.hq.nasa.gov/office/pao/History/alsj/a11/AS11-40-5920HR.jpgNotice the line where the rim of the footpad has shielded the copper brown blanket from high-velocity dust particles. That blanket material is normally glossy and slightly transparent but has been sandblasted matte and opaque here]
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Post by svector on Mar 26, 2007 9:45:30 GMT -4
And again what interests me is Jack White's fanatical following. Among his fans he seems to have achieved an almost godlike status. They leap instantly to his defense whenever his ideas are challenged. I'm jealous -- my colleagues here have a running contest to see who can catch me in an error. My side of the debate is sure a lot harder on the ol' self esteem. LOL, don't get too down. The difficult path is often the noble one. If enlightening the stubborn masses by exposing truth was without challenge, it wouldn't be as rewarding in the end. Jay Windley is Apollo's version of Billy Graham. ;D
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Post by JayUtah on Mar 27, 2007 16:07:04 GMT -4
Kapton is indeed the correct material, not Mylar, at least for the visible layer.
The following is taken from R. Hellmann et. al, "Lunar Module thermal-vacuum simulation utilizing conformal heater thermal control", Journal of Spacecraft and Rockets, vol. 7 no. 2 (1970), pp. 126-131.
Hellmann and his co-authors are the Grumman engineers responsible for the LM's thermal design.
The difference in shades of orange is likely because different film thicknesses were applied on different areas. There are actually a number of materials, coatings, and skins visible on the typical lunar module, whether in the H or J variants, besides those mentioned by the Grumman authors. Sullivan (Virual LM) suggests thermal paint was applied in regions that appear matte black in photographs. Those are the areas I believe are covered in reversed metal-backed film.
One of the things I would love to do (or see Svector do, the way things are going) is obtain samples of all the LM coatings and demonstrate their optical properties on film or in video.
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Post by PhantomWolf on Mar 27, 2007 23:48:19 GMT -4
Well Jay, if you can get them, happy to have them in our presentation.
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