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The different parts of the Soyuz rocket have different colors:

  1. White
  2. Dark gray
  3. Orange

Soyuz rocket with different colors

Progress rockets I saw have different "liveries", multicolored like this

Multicolored Progress rocket

and white like this:

White progress

I suppose they are painted like that (sometimes multicolored, sometimes white) for a reason.

What is/are these reason/s?

I have several hypotheses:

  1. Visual observation. Soyuz rockets were designed at a time, when there were no rocketcams and the flight controllers used specialized telescopes to see what happens with the rocket (in addition to telemetry). If different stages have different colors it may be easier to determine whether they have separated or not. But it does not explain, why some Progress rockets (which have the same "ancestor" as Soyuz) are white.
  2. Danger sign. Orange parts are colored that way because some of them fall down to ground and may contain remainders of a highly toxic propellant.
  3. Ease of recovery. Orange parts fall to ground and are then searched for. Therefore, these parts are colored to be as easily detectable visually as possible (similar to the black boxes of aircraft). Allegedly (not sure, if it's actually true), in the 1950es the parts of rockets, which fell on the ground were collected for at least two reasons. First, in case of failure, to analyze the cause of it. Second, to prevent people from collecting the remainders of the rockets and selling them to competing nations.
  4. No suitable paint. Russian industry is incapable of producing a paint, which would sustain varying and harsh conditions of a spaceflight (like heat coming from the engines at the start and cold of the space in the later stages of the flight). As far as I know, you cannot paint a device the way you like - the color must be certified for the environment, in which the device will be operated. This hypothesis is refuted by the fact that the Angara rocket is white.

Angara rocket

Update 1 (16.11.2014 15:08 MSK): ChrisR suggested another hypothesis:

  • Weight. The orange parts may be bare (unpainted) to make the rocket weigh less.

Update 2 (16.11.2014 15:45 MSK): TidalWave proposed another hypothesis:

  • Ice. Prior to launch, the rocket is covered with ice and therefore appears white. I. e. rockets painted with the same color may appear as white and non-white, depending on whether the ice has melted (and/or been shaken off during launch) or not.

Weight hypothesis seems to be incorrect (see comments).

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    $\begingroup$ I expect the answer is more related to the external coating for structural purposes. The US space shuttle's external tank was painted white for the first two (three?) missions, until it was decided that it added deadweight. Hence all subsequent missions left that thank bare, it was orange. $\endgroup$
    – ChrisR
    Nov 16, 2014 at 11:30
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    $\begingroup$ Re your edit, those orange parts on the Soyuz rocket aren't bare / unpainted. ChrisR alludes to Space Shuttle External Tank's spray on insulation that is orange, perhaps brown-ish in color. On a Soyuz, those are stage aft skirts. They're a subject to too much vibration, acoustic shock air pressure and temperature difference for any such spray-on foam to stay on it for long. I doubt there's any bare materials exposed on a Soyuz or a Proton. Perhaps anodized to save on weight, but they need some kind of environmental protection. I suspect skirts are painted to later analyze system's combustion. $\endgroup$
    – TildalWave
    Nov 16, 2014 at 12:18
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    $\begingroup$ BTW large part of what appears to be white on the first photo are just parts of the rocket with frozen ice condensation on it because there's LOX (cryogenic liquid oxygen) tanks under. Before fueling, and with exception of the topmost payload part (TMA and Progress vehicles), the launch vehicles in first and second photo (both Soyuz) are actually identical in colors. There's another color tho, and that is red parts that are supposed to be removed from the launcher prior to the launch. You'd sometimes notice such parts during transport and they're gone just before the actual launch. $\endgroup$
    – TildalWave
    Nov 16, 2014 at 12:29
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    $\begingroup$ ..because it makes the rocket look pretty? (Some think the white/gray and orange is prettiest, others prefer the pure white.) Sorry if that seems a trivial reason, but it seems you've already covered most of the practical & sensible ones. Just speculation of course.. $\endgroup$
    – Andrew Thompson
    Nov 16, 2014 at 16:58
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    $\begingroup$ That third photo is a Proton rocket, which I do not believe launches Progress rockets (please correct me if I'm wrong). $\endgroup$
    – dotancohen
    Jan 25, 2015 at 8:12

3 Answers 3

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Most rockets are painted white (some have black stripes). White paint reflects more heat than other colors, so this reduces propellant boiloff. The first N-1 was dark gray, later launchers were painted in increasingly light colors because temperatures rose too high to work inside the rocket when it was sitting on the launch pad (from the book N-1: for the Moon and Mars).

The R-7 is an outlier. There is some speculation that its green color is due to it being derived from an ICBM, but there are issues with that theory:

  • It would have made sense to paint them all green if rockets were manufactured and painted before it became clear whether they'd be used as an ICBM or space launcher. The numbers make that an unlikely story: thousands of R-7s have been built for space launches. Only ~10 were ever operational as ICBMs. By 1968, the R-7 ICBM was phased out.
  • Some early R-7s were gray or white instead of green.

I have not been able to find a good explanation for the green paint of the R-7.

The other outlier is the Shuttle external tank. This had a thick layer of insulation to prevent ice formation on the outside of the tank; ice shedding during the launch could have easily damaged the Shuttle's heat shield tiles. The insulation was left in its natural color after the first few launches, when it was found the heat load was acceptable without paint. This saved a few hundred kg.

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I think looks are a serious matter to consider, as Andrew Thompson pointed out in the comments. Satellite operators have to decide which launch provider to use, and for many missions, there are no definitive criteria to pick one over the other. Looking modern and "high-tech-y" may secure some contracts. In any event, because the payload fraction is low on the Soyuz to begin with, carrying a little paint will not hurt much.

I have a soviet-era poster in my bedroom of a Soyuz on the launch pad. The poster is black and white and also faded, but it the rocket seems to be single-colored, apparently white.

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As someone pointed out, specially on the TMA vehicle the white parts are the LOX's tank skin. That color on those tank may reduce heat absortion (from solar light), reducing LOX boil off and thus, increasing laundpad residence time. It could be very important to deal with some launch delays/scrubs. The grey parts are the RP-1 tank's skin. I can't guess now a reason for that color, but the necessities of those tanks are quite different from the necessities of the LOX tanks.

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    $\begingroup$ No, that's not it. The white comes from the ice that's frozen on the surface of the tank as the atmospheric moisture condenses on it. Since LOX is cryogenic, temperature is low enough even through insulation to freeze on the spot. That's what's called cryo-ingestion (or is it cryo-pumping, I always confuse the two). It has nothing to do with boil-off reduction. Most of that ice falls off during liftoff, and the rest melts off as the launcher approaches maximum dynamic pressure. The underlying color scheme is same for both launch vehicles on first two photos the second just isn't fueled yet. $\endgroup$
    – TildalWave
    Jan 24, 2015 at 21:13
  • $\begingroup$ @TildalWave the reason for the gray or gray/green color is probably to contrast the white ice. They want to see where ice is forming, if it is forming in the right places. $\endgroup$
    – DrZ214
    May 30, 2015 at 5:13
  • $\begingroup$ @DrZ214 Or just some paint they have plenty of, comes cheap and does the job. Looks a similar shade of olive gray like what military vehicles would be painted in as camouflage colors (kinda year-long average color of the tundras). It's just a guess tho. There could be many reasons, or even none at all and someone of high position just liked that color and decided that should be it. It wouldn't be the only rocket in the world that's painted in a specific color for aesthetic reasons. E.g. Delta II are painted in Delta Blue to match the color of the Pacific ocean at Huntington Beach, CA. $\endgroup$
    – TildalWave
    May 30, 2015 at 5:28

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