At a NASA press conference
, a reporter asked the question "What happens if the space shuttle
goes out of control and heads for a city?"
Believe it or not, the space shuttle has a self-destruct system on board. It's not new news, nearly every rocket launched has had one of these. It's known as the Flight Termination System.
Launches are in Cape Canaveral for a reason, so that the shuttle can be launched over a large, uninhabited sea. If it crashes, chances are it'll hit the water. If the shuttle loses control, or heads for the coast, the system will destroy the shuttle before it becomes a threat to civillians. This is different from an intact abort, where the shuttle can be steered to a runway/ocean/ alternate orbit.
Basically, along the solid rocket boosters and the External tank is a long line of dynamite (ordinance packages), about the size of a small pipe running from top to bottom, known as a Range Safety Package. In case the shuttle goes out of control, a person at Mission Control known as the "Range Safety Officer" has the job of monitoring the condition and direction of the launch. In the event of a catastrophe mentioned above, the officer presses two switches that send a coded radio signal to the dynamite, and breaking the shuttle apart before it becomes a danger.
There is no dynamite on the shuttle itself, just on the booster rockets and the tank. However, it is almost a certainty that the activation of this system will kill the crew. Earlier systems such as Apollo and Mercury always had a method of escape. (Gemini had ejection seats, while the rest had a capsule eject). The space shuttle is the first rocket by NASA that does not have a way to escape during launch. They do have parachutes, but can only be used when the rockets are shut down, or during re-entry.
While this sounds horrifying, you must realize that the astronauts have volunteered for this mission, civillians in Florida and on the east coast in their homes have not. Probably the only thing worse than a shuttle accident that kills the crew is one that also kills all the spectators.
The Flight Termination System has only been used once on the space shuttle, on the Challenger. If you watch closely on the tape, the booster rockets had broken off seconds after the explosion. While the shuttle was falling, the rockets were still going in spearate directions, out of control. The Range Safety Officer sent the commands, and both rockets detonated about 10 seconds after the first explosion. There was an argument to dismantle this system, but the Challenger changed everyone's mind.
There is no way for the crew on board to trigger the system, and no way to stop it. The only warning would be a small light by the pilot that would come on if the first destruct order of the two was given. The only thing the crew could do if they saw that would be to jettison the External tank and the boosters with it, but would most likely cause the shuttle to spin out and crash.
During re-entry, there is no way to destroy the shuttle. The shuttle itself has no explosives, and the risk is roughly the same as any airplane.
BTW, the risk of you getting killed by a falling airplane is 1 in 25,000,000.