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I was reading Michael Collins' account of the Apollo 11 TLI burn [1], and I wonder wheter the "flashes", "lightning", "sparks flying" and "insistent fireflies" he and Neil Armstrong saw out of the Command module windows could be due to the engine somehow creating a high voltage during operation.

The phenomenon lasted just for the duration of the burn, so it is clearly different from the transient white flashes that some astronauts have seen when a charged particle impacts their brain in space. And it cannot be due to ice fragments or gas particles floating around the ship, as these would go away fast as soon as the engine starts moving the ship.

The burn was performed by the Saturn IV-B cryogenic engine (H2 + O2). I guess a pure combustion shouldn't produce high voltage, but maybe little metal particles flying off the turbopumps could create friction against the engine's metallic nozzle? Collins' description points to an electrical phenomenon, something like Saint Elmo's fire but in space. I'm thinking about the engine accidentally becoming a Van de Graaff generator, which in conjunction with some external phenomenon (solar wind, Van Allen belts) could have resulted in the sparks. So my question is:

TL;DR: Can vacuum rocket engines produce high voltages during operation?

Side questions (not important, but still interesting):

  • Was there ever an official explanation for the flashes?
  • Has any other space flight ever reported something similar?
  • If it was indeed high voltage, shouldn't astronauts wear electrician-grade insulated globes for just in case the voltage mades its way into some switches or part of the cabin?

[1] Collins, M. (2019) Carrying the fire: An Astronaut's journeys. 50th anniversary edition. New York: Farrar, Straus and Giroux. p 372. ISBN 978-0-374-53776-0

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  • $\begingroup$ "Collins' description points to an electrical phenomenon, something like Saint Elmo's fire but in space." Couldn't it just be light from the engine? That wouldn't require an "official explanation". I'm certain it wasn't any kind of electrical phenomenon, but I have no idea how to prove that. $\endgroup$ Apr 1, 2023 at 14:42
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    $\begingroup$ Can you please edit your question to specify whether you are asking if a rcket engine can produce high voltages as per the headline, or what the explanation for the lightning is, as per the body of your question. $\endgroup$
    – Rory Alsop
    Apr 1, 2023 at 15:46
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    $\begingroup$ @MisterSmith it's pretty easy to end up with the question at the end of the post diverging from the one in the title. What I learned to do is to wait until the very end and I'm ready to post before I write the title to make sure it's in synchrony with everything else. It looks like what you would like to ask is "Can engines make high voltage and if so, could this be an explanation if there isn't already one?" which is a bit too much for a single SE question that can have a single SE answer. $\endgroup$
    – uhoh
    Apr 2, 2023 at 9:01
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    $\begingroup$ @MisterSmith Although it's natural to want to ask both, for SE it's necessary to ask one here and post a separate question for the other, and leave a link for each one in the other one. Since Woody has written an answer primarily to "Can engines make high voltage" I'd recommend you ask about the explanation in your next question post and remove it from this one. Thanks! Once you make the edit you can put the question back into the review queue for reopening. $\endgroup$
    – uhoh
    Apr 2, 2023 at 9:02
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    $\begingroup$ @MisterSmith it's usually the community votes on reopening, you've got 4 reopen votes already, probably one more will come fairly soon :-) $\endgroup$
    – uhoh
    Apr 4, 2023 at 2:01

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Although this was clearly not happening during Apollo 11, rocket engines could produce high voltage, but they would need to be re-engineered as the core of a magnetohydrodynamic generator.

In these generators, a high velocity gas stream, seeded with ions (a plasma), passes through a magnetic field. The ions are deflected at right angles to both the axis of flow and the magnetic field, and then collected by electrodes. enter image description here

Source: Wikipedia

The acceleration nozzle looks suspiciously like a de Laval nozzle.

Thermal ionization of rocket exhaust is maximal in the throat area and decreases with expansion. https://www.sciencedirect.com/science/article/abs/pii/S0082078465802132

The Earth provides a (very weak) external magnetic field. So, in the absence of solenoids dangling in the rocket plume, a weak voltage potential could be produced east-west across the plume. I doubt this is related to the Apollo 11 “OMG, it’s full of stars” effect.

A rocket-based MDH generator could be incorporated into a sci-fi plot where grounded colonists MacGyver disabled rockets to generate electricity for rail guns which fend off invading Klingons.

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  • $\begingroup$ Cool info, but not an answer to what was asked. $\endgroup$ Apr 1, 2023 at 15:35
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    $\begingroup$ @OrganicMarble ... actually, the question is, "Can rocket engines produce high voltages?" The answer is "Yes, but only if incorporated into a MHD." $\endgroup$
    – Woody
    Apr 1, 2023 at 15:38
  • $\begingroup$ That's the title. The body says "Was there ever an official explanation for the flashes? Has any other space flight ever reported something similar? And if it was indeed high voltage, shouldn't astronauts wear electrician-grade insulated globes for just in case the voltage mades its way into some switches or part of the cabin?" Don't see your post addressing any of that. $\endgroup$ Apr 1, 2023 at 15:45
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    $\begingroup$ @OrganicMarble ... correct. The OP has several distinct questions. I only addressed one of them. Is there an official explanation of the flashes? $\endgroup$
    – Woody
    Apr 1, 2023 at 16:15
  • $\begingroup$ Nah, it was interesting. But I'm still betting on metallic particles, as in a Van de Graaff generator. $\endgroup$ Apr 3, 2023 at 10:28

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