What Went Wrong

Discovery's engine No. 3 had already helped power three shuttle missions, and its age was showing. About 6 sec. before blastoff, a heated mixture of liquid hydrogen and liquid oxygen was supposed to be pumped forcefully through the engine's main fuel line into a central combustion chamber, where it would ignite. But the 10 1/4 in. long, 74-lb. fuel valve faltered a fraction of a second in opening, prompting the central computer system to abort the entire mission. Of the three main engines, only No. 2 had been fully ignited. During its 1.7 sec. ignition, hydrogen gas leaked out and exploded, charring the shuttle's body flap.

By week's end engineers had yet to figure out whether a part of the valve had failed or whether an intermediate computer had missed a command. In any case, the master computer performed right on cue. Said Mission Commander Henry Hartsfield: "The system detected a problem and shut down the engines. That's exactly what we had been told all along it would do, and I'm glad it did."