|Space Shuttle Flight 12 (STS-41D)|
|Attempt||Planned||Result||Turnaround||Reason||Decision point||Weather go (%)||Notes|
|1||25 Jun 1984, 12:00:00 am||scrubbed||---||Failure of Orbiter's back-up General Purpose Computer forced the scrub.||(T-9:00 minutes and holding)|
|2||26 Jun 1984, 12:00:00 am||scrubbed||1 day, 0 hours, 0 minutes||Post-SSME start RSLS abort due to anomaly in number three main engine||(T-0:06)||Discovery returned to OPF for engine replacement; launch delayed over two months|
|3||29 Aug 1984, 12:00:00 am||scrubbed||64 days, 0 hours, 0 minutes||Discrepancy with master events controller relating to SRB fire commands|
|4||30 Aug 1984, 1:41:50 pm||successful||1 day, 13 hours, 42 minutes||delayed 6 minutes, 50 seconds when private aircraft strayed into KSC airspace|
June 26: Abort flight:
June launch attempt
During the 26 June launch attempt, there was a launch abort at T-6 seconds, followed by a pad fire about ten minutes later.
Mission Specialist Steve Hawley was reported as saying following the abort: "Gee, I thought we'd be a lot higher at MECO (Main Engine Cut-Off)!". About ten minutes later, the following was heard on live TV coverage:
While evacuating the shuttle, the crew was doused with water from the pad deluge system, which was activated due to a hydrogen fire on the launch pad caused by the free hydrogen (fuel) that had collected around the engine nozzles following the shutdown and engine anomaly. Because the fire was invisible to humans, had the astronauts used the normal emergency escape procedure across the service arm to the slidewire escape baskets, they would have run into the fire.
Changes to procedures resulting from the abort included more practicing of "safeing" the orbiter following aborts at various points, the use of the fire suppression system in all pad aborts, and the testing of the slidewire escape system with a real person (Charles F. Bolden, Jr.). It emerged that launch controllers were reluctant to order the crew to evacuate during the STS-41-D abort, as the slidewire had not been ridden by a human.
Examination of telemetry data indicated that the engine malfunction had been caused by a stuck valve that prevented proper flow of LOX into the combustion chamber.