A hydrogen propellant valve in the Pratt & Whitney RL10 Centaur upper-stage engine caused the placement of two classified National Reconnaissance Office ocean surveillance spacecraft into the wrong orbit after launch from Cape Canaveral June 15, the U.S. Air Force Space and Missile Systems Center (SMC) at Los Angeles Air Force Base, Calif., now says.

The Air Force had earlier put the blame on the Centaur, which is Lockheed Martin's responsibility, as opposed to specifically the engine, which is Pratt & Whitney's responsibility (DAILY, July 3).

"The RL-10 cryogenic liquid hydrogen valve is assessed to be the source of the fuel leak during the coast phase of the flight," SMC says. "The anomaly investigation team has initiated high-fidelity testing of the valve assembly."

The objective of this testing, which is being performed at Pratt & Whitney Rocketdyne's engine test facility in West Palm Beach, Fla., is to characterize and replicate the behavior of the valve under conditions similar to those in flight. Initial results are being evaluated by the team while additional testing continues, according to SMC.

"To accommodate ongoing investigation activities, the Air Force and United Launch Alliance have updated the WGS [Wideband Global SATCOM] launch date to August 31, 2007. The Delta IV DSP [Defense Support Program] mission remains on schedule for August 28."

This is a minor slip for the next Atlas V, as happens routinely at Cape Canaveral, indicating that the Air Force believes the valve problem can be solved without significant schedule impacts to the Delta IV and Atlas V, which both use upper stages powered by Pratt & Whitney RL10 engines.