Launch of the U.S. Air Force’s X-37B spaceplane on its third classified mission has been postponed to Dec. 11 from Nov. 27, United Launch Alliance announced Nov. 20.
The Denver-based company, which is the U.S. military’s primary launch services provider, did not give a reason for the delay.
A query to Air Force Space Command was referred by spokesman Mike Pierson to the Air Force Press Desk at the Pentagon. A call to the press desk went unanswered Nov. 21, the day before the U.S. Thanksgiving holiday.
The Boeing-built X-37B was to launch Oct. 25 aboard an Atlas 5 from Cape Canaveral Air Force Station, Fla. But the launch was postponed while the Air Force and ULA separately investigate an upper-stage engine anomaly logged Oct. 4 during an otherwise successful Delta 4 launch of the service’s GPS 2F-3 satellite. ULA’s Delta 4 and Atlas 5 rockets use variants of Pratt & Whitney Rocketdyne’s RL-10 cryogenic upper-stage engine.
The ongoing investigations have created a cascade of launch delays at the Cape, where other government payloads, including NASA’s Tracking and Data Relay Satellite-K, are now waiting for the all-clear from the Air Force and ULA.