English: STS-55 Columbia, Orbiter Vehicle (OV) 102, launch attempt from Kennedy Space Center (KSC) Launch Complex (LC) Pad 39A comes to an abrupt halt when space shuttle main engine (SSME) number 3 fails to fully ignite. The SSME failure initiated a main engine abort sequence by the orbiter onboard computers. Ignition of the SSMEs began at T-6.6 seconds and shutdown was completed at about T-3 seconds, resulting in an on-the-pad abort of STS-55. This was the first time in the post-Challenger era that an SSME shutdown has halted a Shuttle launch countdown, and only the third time in the history of the program. OV-102, atop the external tank (ET) and flanked by two solid rocket boosters (SRBs), had been scheduled to lift off from LC Pad 39A at 9:51 am (Eastern Standard Time (EST)). The fixed service structure (FSS) tower appears to the left of OV-102. View provided by KSC with alternate KSC number KSC-93PC-475.