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Many orbital launch vehicles use a combination of a chilled oxidiser (usually LOX when dealing with liquid-fuelled rockets) and a fuel (commonly RP-1, but with many designs now opting for Methane). Both LOX & Methane require super-cooled temperatures to maintain liquidity: the boiling point for LOX is −182.96°C, while Methane's is -161.5°C.

SpaceX has attempted to take this lower (with varying success...) by super-chilling their LOX and RP-1 (to the point where the latter starts acting most similarly to a watery gel) down to -206.67°C & -6.67°C respectively.

Falcon 9 however, is painted in a proprietary blend of white on top of its Aluminum-Lithium alloy. The understanding, at least within casual spaceflight fan circles, is that this reflective coating is enough to prevent excessive heat buildup and eliminate or reduce propellant boiloff.

The CRS-13 mission looks set to change this slightly — with the Falcon 9 first stage continuing to sport its soot from its previous flight:

enter image description here The CRS-13 vehicle at SLC-40 in Florida, with its soot still present from the last landing.

Does this added layer of darker material influence the thermal properties of the vehicle with respect to its propellant?

Furthermore, RocketLab's Electron launch vehicle completely bucks the trend of white rocket designs; instead opting to stick with the sleek & shiny black of its Carbon-composite fibre body:

enter image description here The second Electron launch vehicle on the launchpad at Mahia Peninsula, New Zealand; sporting its black carbon-composite design.

Propellant thermal management should surely be in full play with this vehicle, especially considering it has a much higher surface to volume ratio, when compared to Falcon 9.

So, just how much does the exterior color of the vehicle affect thermal management protocols, the propellant, and rates of boiloff? Is this a genuine concern or something that has endlessly made the rounds of spaceflight-geek circles with no substantial evidence?

Ideally, I'm looking for an answer which has citations to prior work, or studies conducted recently on modern launch vehicles.

marked-down
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  • You forgot to mention liquid hydrogen, -252 °C is substantially colder than LOX or liquid methane. Oxygen and methane will be solid at the temperature of LH2. – Uwe Dec 12 '17 at 11:21
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    When the first N-1 was rolled out to the launch pad (painted dark gray), it was found that interior temperatures were uncomfortably high for the technicians working inside the rocket. Later N-1s were painted white instead to mitigate this problem. – Hobbes Dec 12 '17 at 12:12
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    I'm not sure but I imagine weight savings could also play a role during coating or paint selection as paint can get heavy especially on larger scales. – Dragongeek Dec 12 '17 at 12:19
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    I don't know about choice of colors, but with the Shuttle's main tank they choose to go without paint entirely after first test flights, saving up a good couple hundred kilograms of dead weight. – SF. Dec 12 '17 at 12:58
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    It's hard to paint carbon fiber, you need a lot of priming to fill up the porous surface. Probably more weight penalty than it's worth. – GdD Dec 12 '17 at 13:02
  • @GdD: You don't need a perfect finish, you just need enough coverage to reduce the heat load. – Hobbes Dec 12 '17 at 15:41
  • There's a question on the Shuttle tank color here somewhere which addresses the tradeoff. – Hobbes Dec 12 '17 at 15:42
  • I'm pretty sure the answer is "it completely depends on the level of insulation and thermal coupling between the outer skin and the cryostat" and so would depend mostly on the specific mechanical and thermal engineering of each individual rocket design. A better question would be "how does the Electron rocket insulate cryogenic propellant from its black, sunlight-absorbing areas?" or "is the Electron's LOX under the black area?" – uhoh Dec 13 '17 at 06:31
  • Peter Beck's Answer: https://www.reddit.com/r/space/comments/8a1wwy/i_am_peter_beck_ask_me_anything_about_rocket_lab/dwvalm0/ – randomUsername Apr 09 '18 at 21:58

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Wernher von Braun always painted their rockets in large black & white blocks or checkers, to enable them to see if the rocket rolled during launch. This continued on to the Saturn series. There were some instances where the tanks under the black gained too much pressure. I don't know if there were any painting scheme changes as a result.

Johnny Robinson
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  • "There were some instances where the tanks under the black gained too much pressure." Interesting! Do you remember where you saw this? Is it possible to list a source? – uhoh Dec 13 '17 at 06:08
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The interstage above the first stage of the Saturn V SA-500F test article was painted black. It was found to get too hot while standing in sunlight on the launch pad. Later Saturn Vs had the interstage painted white.

DrSheldon
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