I think you're referring to McLaren lining their engine bay with a thin layer of gold? The use case here was very good heat transfer with low weight, since you

I think you're referring to McLaren lining their engine bay with a thin layer of gold? The use case here was very good heat transfer with low weight, since you only need a very thin layer to do it. "Aerospace" is unfortunately a word that is overused by PR departments because it sounds flash. "Aircraft-grade aluminum" is the main one. It's a meaningless word because it just means some particular alloy of the metal. The difference is that here McClaren wants to transfer heat via condution very efficiently. In space you can't do that because everything is in vacuum - condution is very inefficient. So the way you get heat in or out is via radiation, and that means the Sun is a problem. The films around satellites are designed to reflect sunlight. The gold in there is probably kapton, or something very similar. Polyimides were developed by DuPont in the 1950s and in the 60s they came up with Kapton which is now ubiquitous in electronics (flexible PCBs for example). Kapton was used on the Lunar Module (and other bits): https://apollo11space.com/apollo-11-kapton-foil/ https://apollo11space.com/apollo-11-kapton-foil/ Some of the best-in-class films today are manufactured by a company called Dunmore. They made insulation layers for Hubble, Curiosity, JWST and some other high profile missions. All these companies do defense contracting so they probably make films for spy satellites as well. https://www.dunmore.com/industries/insulation.html https://www.dunmore.com/industries/insulation.html