spacetoday.net: Delta 4 launch encountered upper-stage engine issue

Posted: Sun, Oct 7, 2012, 10:20 AM ET (1420 GMT)
Delta 4 launch of GPS2F-3 (ULA)

United Launch Alliance (ULA) confirmed late Friday that there was a problem with the upper-stage engine during Thursday's launch of a GPS satellite on a Delta 4 rocket. According to ULA, launch controllers noticed an "unexpected data signature" in the performance of the RL10 engine that powers the Delta's upper stage. The unidentified problem caused reduced thrust levels from the engine, but the upper stage was still able to release its payload, the GPS 2F-3 satellite, into the proper orbit because of design margins and propellant reserves. ULA and the engine's manufacturer, Pratt & Whitney Rocketdyne, have created a team to investigate the anomaly. It's not clear yet if the issue will delay the launch in late October of an Atlas 5, which uses a different variant of the RL10 in its upper stage.