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This image of STS-8 shows red peeking through the grey of the launch structure. That got me thinking...

  • Mercury-Atlas launch towers were red (although Mercury-Redstone's towers were yellow, I think)

  • TItan GLV launch towers were red.

  • Saturn launch towers were obviously red. (Although apparently the milkstool was grey?)

But the shuttle launch structure was all grey. Even later Titans were grey.

Why all the different colors? Why go to such length as to paint over an entire massive launch structure in a different paint/sealant? Is the grey more resistant than the red, hence why the base of the Saturn structure had it, the milkstool had it, and I'm guessing the shuttle SRBs required the entire launch structure to have it?

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Several searches of NTRS and the FAA did not reveal a direct answer, so this is an educated guess.

The Kennedy Space Center Story does confirm that the tower was painted red during the Apollo era:

Each launcher is 445 feet tall and weighs about 12,000,000 pounds. The two-story base, enclosed by battleship grey steel plates, covers half an acre. Within the base are computers linked with the computers in the firing room of the Launch Control Center and also connected with other launch related equipment.

Towering over the base is the red umbilical structure; it provides support for nine swing arms for direct access to the space vehicle, 17 work platforms and distribution lines for propellant, pneumatic, electrical and instrumentation systems.

p. 27

This source used to be available on NTRS as document 19710024295, but seems to be no longer available. The similar book Moonport makes no mention of painting or color at all.

The mention of "battleship grey" suggests that it the very same paint that is used on naval ships. Such paint has a long history of being durable and corrosion-resistant -- an important factor for a facility near the ocean. Thus, it would be the expected default paint color at KSC.

I suspect that the red color of the tower is a kind of aircraft warning paint. FAA rules require such paint for structures taller than 200 feet, so they are easily visible by aircraft; the mobile launch platform is 445 feet tall. The rules do allow the FAA to grant exceptions; in particular, the MLP tower is solid red, instead of alternating stripes of "aircraft orange" and white. Also, even though KSC is in a restricted airspace, NASA and the Air Force do fly in the vicinity, so it is a prudent idea to increase the visibility of the tower.

The first two Shuttle stacks were painted entirely in white, including the external tanks. It would therefore be prudent to continue to paint the towers in a highly visible red color. However, the external tanks of all of the remaining missions were unpainted. Conveniently, the natural color of the external tank insulation was an orange color, and highly visible. Thus, there was no longer a need to paint the tower red and the more reliable grey paint could be used.

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  • $\begingroup$ That FAA document is from '15, I wonder if there's a similar such rule of Apollo vintage? Also interesting reference here, a fun video on paint (???): youtube.com/watch?v=C5PzL7Yeops $\endgroup$ Sep 8, 2021 at 6:21
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    $\begingroup$ I think you're right that the current one is anti-corrosion paint, but the red one probably also was - red lead paint was pretty ubiquitous for such purposes. There was a major move away from it in the 1970s due to toxicity, which neatly matches with the timeframe stated here. $\endgroup$ Sep 8, 2021 at 8:56
  • $\begingroup$ Since this is advertised as a guess, I've removed my downvote. I'd be surprised if this is correct. @Andrew is more likely on the right track. The answer may be in the idiosyncratic first hand-account of building the shuttle launch tower here 16streets.com/39-B/… but I don't have time to read it again now. It does say the gray paint is a "pearl gray epoxy top coat". $\endgroup$ Sep 8, 2021 at 12:47
  • $\begingroup$ @Andrew: WRONG, the paint was zinc-based, not lead. NASA has to do an annual environmental report; these came up repeatedly in my searches (e.g. this). "Lead levels were consistently low but were higher than background soils in the 63-250 μ range. Zinc concentrations were above background levels and the source was believed to be the large amount used in corrosion control on the pad and mobile launch platform surfaces." ... $\endgroup$
    – DrSheldon
    Sep 8, 2021 at 13:33
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    $\begingroup$ "The red paint on the structure contains high amounts of PCBs (Polychlorinated Biphenyls) and lead." From a NASA press release quoted here. collectspace.com/news/news-020404a.html $\endgroup$ Sep 8, 2021 at 15:56
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Yes, you kind of did hit the nail on the head. All of the original mobile launchers including the Redstone launcher were painted red. In fact, the Redstone launcher was originally an oil derrick. For the Redstone, there was a yellow device at the launch pad. It was called a "Cherry Picker" and acted as an elevator to take the astronaut up to capsule level. It was found out many years later, that the pigment chemicals in red paint, did not fair too well in the corrosive salt air right next to the ocean. This was especially true at Pad 19 which was where the Gemini Titan II's were launched. By the time that tower was dismantled years ago, the red had faded to a rustic red/pink color. The launcher towers rusted easily. Hence, when the newer towers were erected, especially for the Shuttle program, the towers were painted gray as gray pigment has a better resistance to rust and corrosion. Personally and just for looks, I preferred the red, but gray paint means less maintenance and that is understandable. Also, they decided after the first two shuttles to quit painting the external tank white. This actually lessened the lift off weight of the craft.

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  • $\begingroup$ The Shuttle towers were originally red, so your answer is incorrect. When you fix it, add some references and stick to answering what was asked. $\endgroup$ Jul 22, 2022 at 12:49
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    $\begingroup$ In the fifties and sixties there was a widely used red pigment made from lead that was famous for its resistance to rust and corrosion. Read en.wikipedia.org/wiki/Lead(II,IV)_oxide Decades later lead free paints were used to reduce toxicity. So zinc powder was used in a gray paint. $\endgroup$
    – Uwe
    Jul 22, 2022 at 20:36
  • $\begingroup$ The Shuttle FSS (fixed service structure) towers were actually the original top sections of two of the Apollo mobile launch towers. So not exactly new, although of course they had to be modified on the ground for their new purpose and then erected at the pads. The RSS (rotating service structure) was new though. This has no bearing on the gist of your answer I'm just mentioning it as additional info. $\endgroup$ Apr 1 at 16:10

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