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Re:Space shuttle Endeavour's giant orange external tank begi... by gadders on Thursday January 04, 2024 @05:00AM (#38865190)
Anyone remember the first few launches where the tanks were white, then they realised they could save a bunch of weight by not painting them?
Re:Space shuttle Endeavour's giant orange external tank begi... by ajdoingnothing on Thursday January 04, 2024 @08:08AM (#38866550)
Yes! Win-win imho — the orange made it look much better along with the white SRBs, orbiter and a blue sky in the background.
Re:Space shuttle Endeavour's giant orange external tank begi... by adolph on Thursday January 04, 2024 @08:12AM (#38866596)
I had to look it up in case this was a Berenstein Bears/Shazam bad collective memory:

The external tank's orange color is the color of the spray-on foam insulation. The first two tanks, used for STS-1 and STS-2, were painted white to protect the tanks from ultraviolet light during the extended time that the shuttle spent on the launch pad prior to launch. Because this did not turn out to be a problem, Martin Marietta (now part of Lockheed Martin) reduced weight by leaving the rust-colored spray-on insulation unpainted beginning with STS-3, saving approximately 272 kg (600 lb).

https://en.wikipedia.org/wiki/Space_Shuttle_external_tank

Re:Space shuttle Endeavour's giant orange external tank begi... by whycome on Thursday January 04, 2024 @08:55AM (#38866978)
Rarely mentioned, but I think the foam is polyisocyanurate. I think it changes to the rust colour due to exposure (it's typically light yellow). Anyone got more info?

https://ntrs.nasa.gov/citations/19890003374

Re:Space shuttle Endeavour's giant orange external tank begi... by gadders on Thursday January 04, 2024 @10:04AM (#38867827)
I did hesitate slightly before posting, but I remember watching the countdown at junior school and the launch when I got home.
Re:Space shuttle Endeavour's giant orange external tank begi... by marssaxman on Thursday January 04, 2024 @05:25PM (#38873142)
I'll never forget them; watching those launches had a profound impact on the course of my life.