"What would happen if an astronaut became mentally unstable in space and, say, destroyed the ship's oxygen system or tried to open the hatch and kill everyone aboard?"

It turns out NASA has detailed, written procedures for dealing with a suicidal or psychotic astronaut in space. The documents, obtained this week by The Associated Press, say the astronaut's crewmates should bind his wrists and ankles with duct tape, tie him down with a bungee cord and inject him with tranquilizers if necessary.

...The crew members might have to rely in large part on brute strength to subdue an out-of-control astronaut, since there are no weapons on the space station or the shuttle. A gun would be out of the question; a bullet could pierce a spaceship and kill everyone. There are no stun guns on hand.

(Via DefenseTech.)