Shuttle engine test is one in a million: "It will happen today at 294 seconds into the 520-second test firing of a space shuttle main engine. The 'it' is a milestone: Second 294 will mark the 1 millionth second of shuttle engine firing. That figure includes test firings at Stennis as well as live launches from Kennedy.

"About 760,000 seconds of the 1 million, or 76 percent, has been done at Stennis, according to Boeing officials. The engine being tested today will be used on space shuttle Discovery, NASA's second mission since the return to flight."

"The space shuttle main engine is the most highly tested large rocket engine ever built. It's a reusable, staged-combustion cycle engine. Using a mixture of liquid oxygen and liquid hydrogen, the engine can attain a maximum thrust of 512,950 pounds, which is greater than 12 million horsepower."