This year's Doctor Who Christmas Special was pretty decent, I thought, apart from one thing. Which seriously bugged me.
The Titanic (an alien spaceship) is orbiting Earth, and then Things Go Wrong, and there's a race to prevent the Big Bad from turning off the engines because, if that happens, the ship will crash into the planet, killing everyone. (It uses nuclear power for its engines, so if it crashes, it goes critical and wipes out everyone.)
What The Fuck?
Who thinks that spaceships need to constantly run their engines to stay in orbit? Isn't that the whole fucking point of orbit, that you just stay there, because of basic Newtonian physics? Even people who don't think about physics a lot should be aware of how the Space Shuttle (or any other type of satellite) just stays up there in orbit, until it needs to come down again; Star Trek and other science fiction shows have also made us used to the basic idea that you park around a planet, and you can e.g. beam down the entire senior command crew, and the ship will just quietly tick over until they come back and need to move it away from this planet.
But no, RTD decides that, because this is a space ship in the shape of an ocean-going ship, somehow he needs to say that you need to keep the engines going, or the ship will sink crash into the planet.
Never mind that, while our heroes are trying to fend off the Big Bad from commandeering the engines of the ship, nobody thinks "wait, let's steer the ship away from the planet so it falls onto, e.g. the moon" - which will still kill everyone on board, but not, crucially, the 6 billion people on Earth.
The worst thing is that if the Big Bad had instead pointed the ship into a decaying orbit, and then locked the engines, so the struggle was about unlocking the engines so our protagonists could avoid burning up in re-entry, the whole thing would have made a lot more scientific sense, without sacrificing any of the plot points.
