On Sat, 11 Feb 2023 07:23:09 -0800 (PST), Quadibloc
<
jsavard@ecn.ab.ca> wrote:
On some social media platform, I saw a picture of the Soviet version of the Lunar Module in a museum.
There were comments on its golden color.
When I first saw the photo, my reaction was: why on Earth would the Soviets make a lunar lander out of brass? That's a heavy metal for its strength; aluminum or something would be better!
And then I thought: oh, no. Russia has plenty of titanium, and they used it a lot. So maybe it's coated with titanium nitride, like drill bits, and that's where the golden color comes from.
And then I finally slapped my head! Of course it really was gold-plated, like the people were saying. U.S. Moon landers like surveyor, and the Lunar Module, were covered with foil that was also gold-plated. And that was for the same reason they used
gold on the mirrors of the JWST! Gold is good at reflecting infrared light - so it's used on the JWST to see in the infrared, and it's used to plate space vehicles to keep them cool!
We don't use gold for thermal protection, and I doubt the Soviets did,
either. Energy from the Sun is primarily in visible light, not IR. The
gold we see on spacecraft is actually aluminum sheathed in yellow
plastic. It reflects primarily visible light to prevent spacecraft
from absorbing too much light and heating up. Absorbed visible light
is re-radiated in the IR (this is the reason for the greenhouse effect
on Earth). But almost no energy from the Sun is in the IR.
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