I was looking at pictures of the lunar module (don't question why ;)) and looking at the landing leg's gold foil I googled why they're there. It is said that it's used to manage the extreme environment and temperature of space, my question is, can any other material be used in place of the gold foil? I imagine the gold foil could be quite expensive, do other materials work just as well? If so, why don't we use it?
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$\begingroup$ Shouldn’t you VTcing your question auto close it $\endgroup$– StarshipCommented Sep 19 at 22:51
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1 Answer
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Multilayer insulation (MLI) has no gold foil. It is instead multiple layers of Mylar or Kapton, with aluminum deposited in the inside. The Kapton is what gives MLI a golden color. The layers are separated by a mesh material.
Source: https://www.nesdis.noaa.gov/news/good-gold-are-satellites-covered-gold-foil
Quoting from the above source,
While they may seem like they are draped in precious metal, it’s usually not gold at all… or even foil! It is actually a material called multi-layer insulation, or MLI.
MLI consists of lightweight reflective films assembled into thin layers that range in thickness. These layers are usually made of polyimide or polyester films (types of plastics) coated with very thin layers of aluminum. The exact composition depends on where the satellite will orbit, what the insulation will be protecting and how much sunlight it will be exposed to.
The gold and silver colored sheets you see are often a single layer of aluminized polyimide with the silver aluminum side facing in. The yellowish-gold color of the polyimide on the outside gives the satellite the appearance of being wrapped in gold.
answered Sep 16 at 9:59
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3$\begingroup$ 30 years ago, I worked on a physics experiment that did use gold-plated Mylar only six microns thick, but it was for voltage, not insulation! We made three $\pm$4 kV planes 26 mm apart stretched tight across a frame the same size and shape as a standard door, with lots of tiny wires strung between to track charged particles passing through. For details, see Fissum, Bertozzi, et al., 2001, Vertical drift chambers for the Hall A high-resolution spectrometers at Jefferson Lab, Nuclear Instruments & Methods A 474(2), osti.gov/biblio/903086 $\endgroup$– Ryan CCommented Sep 16 at 17:04