Factual error: The surviving space shuttle takes off from the asteroid horizontally, like an airliner taking off from a runway. This is absurd. There is no air to provide lift for the wings, so the shuttle - with its engines providing thrust straight back - would simply trundle along the ground like a car. It doesn't use its maneuvering jets at any time, and they are far too feeble to lift the weight of the shuttle anyway. Nor do they gimbal the main engine, which would lift the shuttle vertically on an axis through the centre of the engine - they swoop gracefully into the air after a long take off. Second, they'd have to count on finding a clear length of ground on a debris strewn asteroid. Vertical takeoff, anyone?
General Kimsey: We spend $250 billion a year on defence, and here we are! The fate of the planet is in the hands of a bunch of retards I wouldn't trust with a potato gun!