| CAPE CANAVERAL, Florida
CAPE CANAVERAL, Florida Oct 11 The U.S. Air
Force on Thursday launched an investigation into a glitch with
the flight of an unmanned Delta 4 rocket that carried a GPS
navigational satellite into orbit last week.
The Global Positioning System 2F spacecraft reached its
intended orbit despite a problem with the rocket's upper-stage
engine, which is built by Pratt & Whitney Rocketdyne, a unit of
United Technologies Corp that is being sold to GenCorp
Future flights of the Delta 4 rocket are on hold, pending
results of the investigation, the Air Force said. The Delta 4
rocket is built by United Launch Alliance, a joint venture of
Boeing Co and Lockheed Martin Corp.
General William Shelton, who heads Air Force Space Command,
said the Air Force planned a rigorous investigation to determine
the root cause of the anomaly with the upper-stage engine.
The Delta 4's second-stage RL10 engine unexpectedly reduced
its thrust during the Oct. 4 launch, United Launch Alliance
reported after the liftoff from Cape Canaveral Air Force Station
"The onboard inertial guidance and flight control systems
compensated for the lower thrust conditions and the Delta second
stage delivered the satellite to the proper orbit," ULA said in
ULA and Pratt & Whitney Rocketdyne are also investigating
The probe could also affect launches involving ULA's Atlas 5
rockets, which use a similar RL10 second-stage engine. An Atlas
5 is scheduled to launch around Oct. 25 with the military's
X-37B spacecraft, a robotic miniature space shuttle that has
made two prior flights.