What Happened on August 4th

Only a few seconds before ignition, a computer halts an engine test in preparation for the launch of the space shuttle Discovery. The shuttle engine's computerized controllers determined that a valve was not closing fast enough and sent a major component failure command from the computer to all three engines, telling them not to fire. The test and computer system were part of NASA efforts to ensure the safety of Discovery, whose flight would be the first since the Challenger explosion in 1986.