Quote:
Originally Posted by JayUtah
I can confirm that different skin materials were used on the inboard sections of the LM footpads. The dark material is H-film and was used to protect parts of the LM that would possibly be subjected to exhaust impingement. The "gold" aluminized mylar is not well suited to direct exhaust impingement.
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I know this is an ancient thread, but I figure at least some of the original participants may see it.
I think the different thermal protection on the inboard footpads may have been to protect against infrared radiation from the descent engine bell, as well as (or maybe instead of) direct impingement by hot gas. There may also have been thermal radiation from the plume. We know hypergolic engines in steady state emit little visible light, but what about other wavelengths? Burning hydrogen, for example, is almost invisible too but it emits a lot of ultraviolet.
There's a shield between the engine bell and the landing radar, designed to protect the latter from the intense infrared radiation. It's pretty obvious from the design of this shield (a simple rectangular plate) that the problem is radiation and not flowing gas.