Space Logs > RCLS Abort History
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STS-41 D: June 26, 1984
The countdown for the second launch attempt for Discovery's maiden flight ended at T-4 seconds when the orbiter’s computers detected a sluggish valve in main engine 3. The main engine was replaced and Discovery was finally launched on August 30, 1984.
STS-51 F: July 12, 1985
The countdown for Challenger's launch was halted at T-3 seconds when on-board computers detected a problem with a coolant valve on main engine 2. The valve was replaced and Challenger was launched on July 29, 1985.
STS-55: March 22, 1993
The countdown for Columbia's launch was halted by on-board computers at T-3 seconds following a problem with purge pressure readings in the oxidizer preburner on main engine 2 Columbia's three main engines were replaced on the launch pad, and the flight was rescheduled behind Discovery's launch on STS-56. Columbia finally launched on April 26, 1993.
STS-51: August 12, 1993
The countdown for Discovery's third launch attempt ended at the T-3 second mark when on-board computers detected the failure of one of four sensors in main engine 2 which monitor the flow of hydrogen fuel to the engine. All of Discovery's main engines were ordered replaced on the launch pad, delaying the Shuttle's fourth launch attempt until September 12, 1993.
STS-68: August 18, 1994
The countdown for Endeavour's first launch attempt ended 1.9 seconds before liftoff when on-board computers detected higher than acceptable readings in one channel of a sensor monitoring the discharge temperature of the high pressure oxidizer turbopump in main engine 3. A test firing of the engine at the Stennis Space Center in Mississippi on September 2nd confirmed that a slight drift in a fuel flow meter in the engine caused a slight increase in the turbopump’s temperature. The test firing also confirmed a slightly slower start for main engine 3 during the pad abort, which could have contributed to the higher temperatures. After Endeavour was brought back to the Vehicle Assembly Building to be outfitted with three replacement engines, NASA managers set October 2nd as the date for Endeavour’s second launch attempt.