In the span of a few seconds, a smooth countdown to launch Space Shuttle Mission STS-93, a five-person crew, and the Chandra X-Ray Observatory abruptly ended twenty years ago just before ignition of Orbiter Columbia’s three Space Shuttle Main Engines (SSME).
An indication that hydrogen gas was leaking into the orbiter’s aft compartment where the engines were mounted popped up on a systems engineer’s computer screen as pre-liftoff water began to be poured into the launch pad flame trench.
At T-10 seconds, the Ground Launch Sequencer (GLS) gave Columbia’s flight computers the go to start the engines and the hydrogen burn off igniters started as another precursor to main engine ignition that occurs just under seven seconds from liftoff. Starting the engines with leaking hydrogen could make the situation worse, so with no time to lose, primary hazardous gas system engineer Ozzie Fish called out on the Shuttle launch team’s main voice loop to stop everything.
It could take a second or two to manually stop a Shuttle launch countdown, which fell on primary GLS engineer Barbara Kennedy to make happen by pushing a button on her console to cutoff the countdown.
The indication of a leak turned out to ...