The Air Force-led review of an anomaly that occurred during the June flight of a United Launch Alliance (ULA) Atlas V rocket has determined the cause to be a faulty valve that led to a fuel leak, the service said last week.
The fuel leak is said to have prevented the rocket’s payload of classified intelligence satellites from deploying in their proper orbits during the June 15 mission, which was designated AV-009.
“The cause of the upper stage underperformance was a fuel leak in the RL10 engine system cryogenic liquid hydrogen valve following the first of two main engine burns for the Centaur upper stage,” the Space and Missile Systems Center (SMC) wrote in a statement detailing released Oct. 5 outlining the findings of the Air Force, National Reconnaissance Office and ULA investigation into the mishap.
“The leak continued,” SMC explained, “during the long coast phase between the two Centaur main engine burns. The rigorous three-month investigation systematically identified all possible causes of the leak. Through high-fidelity testing at Pratt & Whitney Rocketdyne and at another high-fidelity test stand at the ULA facilities in Denver, engineers were able to replicate the flight behavior of the valve design from the AV-009 flight.”
SMC said that independent review team members and “senior level customers” also participated in the review and provided consensus on the findings of the investigation.
Corrective actions for near-term flights include replacing the valve with a design that has been shown by extensive testing to operate properly under all flight conditions, SMC said. The flight valves will also be tested under flight-like conditions to confirm that they will operate properly and with sufficient margins, the center said. Further, additional cycling of the fuel valve is being added to the mission designs to provide additional assurances of proper operation and valve closures during the flight, it said.
SMC said during the investigation, engineers were able to review both Atlas and Delta launch vehicle data and system designs in parallel to ensure that all data were considered and that corrective actions were properly implemented for both launch systems.
ULA is the joint venture of Boeing [BA] and Lockheed Martin [LMT]. Atlas is originally a Lockheed Martin design, while Boeing developed the Delta family of boosters.
“We were able to conduct this investigation as a fully integrated team, including the ULA and U.S. government Atlas and Delta teams working together, and our national security space program is the beneficiary,” Col. Sam Greaves, commander of SMC’s Launch and Range Systems Wing, said in the statement. “This has been a very comprehensive investigation and review which clearly demonstrates that our focus on Mission Success remains our number one priority.”