8

I am assuming here that these solar mirrors/panels are orbiting Ganymede, not flying through its atmosphere.

Nothing indicates that Ganymede has a substantial atmosphere - it is missing it now, in the show there are domes and humans use space suits, there is nothing that indicates the presence of an atmosphere.

I would expect that the destroyed satellites would stay in orbit rather than start falling immediately toward ground. AFAIK pieces should stay in orbit rather than start falling immediately like after the destruction of a powered object flying through the atmosphere.

Here are the objects that were destroyed:

enter image description here

Note that these panels seem to be depicted destroyed, on the ground at the first scene of the next episode, around 2:06 - and that scene is not in distant future given that wounded leader of Martian team is still alive.

enter image description here

In s2e8, around 5:00 one character claims that mirrors started falling immediately and hit domes.

So why these panels fall immediately rather than stay as a debris in orbit?

  • I removed the possible solutions because answers to the question really belong in the answer section below, not in the question body. – Mithrandir Jan 15 '18 at 12:36
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    I think it's safe to rule out number 4, anyway. With the notable exception of the proto-molecule, they appear to be trying pretty hard for realistic science. Perhaps the books would provide more context, though, from someone who's read them. – Steve-O Jan 15 '18 at 14:32
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    My assumption was always that the explosions pushed some into higher orbits and some down out of orbit – user20310 Jan 15 '18 at 17:34
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    I can confirm that they're called "orbital mirrors" in the book, and that they also fall down immediately there, which does seem like a contradiction. – tobiasvl Jan 16 '18 at 9:32
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    Just a small note - just because there are suits and domes doesn't mean there isn't an atmosphere. Just because there's an atmosphere doesn't mean you can breathe it, or that it's safe to expose yourself to it. Also note that the satellites would normally be under constant thrust due to reflecting the incident light (or transmitting the power in case of a solar satellite). Combined with the weak gravity of Ganymede (lower orbital speed) and whatever impulse they got when they were destroyed, it might be conceivable that they fall within mere hours. You'd need to math it out. – Luaan Jan 16 '18 at 15:36
3

The book, Caliban's War, doesn't shed more light (heh) on the issue.

The mirrors do, as you assume, orbit Ganymede. At least: Almost every time they're brought up in the book, they're called "orbital mirrors".

The great orbital mirrors had always been his allies, shining down on his fields like a hundred pale suns.
Caliban's War, page 21

The following passage might imply that the mirrors start falling when the power is cut (how long that takes is, like in the show, not stated):

Power to the grow lights had been cut, and the mirrors … He couldn't think about the mirrors.
Caliban's War, page 25

If there's an actual correlation between the power failure and the mirrors falling, this might mean that the mirrors normally experience orbital decay, and that constant adjustments to their course are needed to keep the orbits. When the power disappears, Ganymede's communication with the mirror array is lost, and the mirrors' orbit starts decaying until they fall down.

In order for this to happen, though, Ganymede would need to have an atmosphere. Orbital decay like this would really only occur if there was atmospheric drag. However:

The atmosphere was so thin it could pass as an industrial vacuum.
Caliban's War, page 9

I could only find one other person raising this point online. The authors and showrunners do not seem to have addressed it, and I couldn't find any articles talking about it either (although there are many articles about the show's adherence to real-life physics and the few holes that do exist, I couldn't find any about this).

All in all, this seems to be a plot hole which hasn't been caught by a lot of people.

user20310 said the following in a comment:

My assumption was always that the explosions pushed some into higher orbits and some down out of orbit

This might also be a possibility. Prax Meng often talks about that "the cascade" will kill Ganymede. He means that the moon's artificial ecosystem will collapse, piece by piece, because of the events at the beginning of the story. However, small events cascading into larger ones is a theme throughout the book (and season; episode 10 of season 2 is even called "Cascade"). It's possible the authors intended the destruction of the mirrors in orbit to trigger a Kessler cascade. However, with the low atmospheric drag, this wouldn't suddenly cause the mirrors to lose orbit entirely, like you say in your question.

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    "this wouldn't suddenly cause the mirrors to lose orbit entirely" - what worse, there are scenes (later in show) that depict mirrors falling straight down. – Mateusz Konieczny Jan 16 '18 at 16:19
  • "pushed some into higher orbits and some down out of orbit" - maybe I missed it but there is no case of debris/pieces showed to be pushed upward or remaining in orbit. – Mateusz Konieczny Jan 16 '18 at 16:20
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One answer would be that the term 'orbital mirror' is a historical generic term like 'tin foil' and 'kleenex'. Foil is no linger made of tin and not all tissue paper is made by Kleenex but the terms have stuck. The Mirrors didn't take long to fall so they were pretty close to Ganymede station. Otherwise there would have been plenty of time to destroy or divert them, or at least evacuate people from the most vulnerable dome areas. They could have been supported by a low power Epstein drive or perhaps some of the collected sunlight could have been used to generate thrust from vaporized ice brought up from the surface by transport ship as fuel. They wrongly assumed that any catastrophic failure would nevertheless give the operators time to divert the mirror to crash away from the station. Nobody imagined they'd get stuck in a battle zone.

  • I really like this solution! It is unlikely to be what author intended, but I really like solutions for plotholes that fit within a story. I should rewatch and check is there anything that would disprove that idea. – Mateusz Konieczny Dec 1 '18 at 21:57

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