A NASA team was unable to isolate a single technical root cause for Orbital ATK’s [OA] Antares launch failure, but instead found three credible technical root causes (TRC), of which any one or a combination there of, could have resulted in the failure.
“The IRT determined that all three of these technical root causes would need to be addressed as part of any return to flight efforts for Antares,” the NASA independent review team (IRT) investigating the October 2014 Antares failure said in the executive summary of its Orb-3 accident investigation report, released Oct. 29. “However, the presence of the machining defect and foreign operating debris (FOD) could have increased the possibility of failure associated with the engine design and Antares operating conditions.”
One TRC was manufacturing, or another workmanship defect, in the engine E15 liquid oxygen turbopump. Forensic investigation performed by Orbital ATK and NASA discovered the presence of a defect on the turbine housing bearing bore that was not consistent with baseline design requirements. The investigation determined that the defect was introduced during machining of the bearing bore housing and was, therefore, present before the engine acceptance test program (ATP) and Antares launch for Orb-3.
A second TRC was inadequate design robustness of the AJ26 liquid oxygen (LO2) turbopump hydraulic balance assembly (HBA) and turbine-end bearing for Antares. The team found that the HBA and thrust bearing designs have several intricacies and sensitivities that make it difficult to reliably manage bearing loads. The AJ26 is an old Soviet-era engine refurbished by Aerojet Rocketdyne [AJRD]. Aerojet Rocketdyne is no longer supplying AJ26s to Orbital ATK.
As a result, this area of the turbopump is vulnerable to oxygen failure and fires. The NASA IRT found the AJ26 engines were not subjected to a thorough delta-qualification program to demonstrate their operational capability and margin for use on Antares. Performing a thorough delta-qualification program for Antares would likely have revealed these issues, the IRT said.
A third TRC was FOD introduction to the engine E15 liquid oxygen turbopump. Forensic investigation identified the presence of both titanium and silica OD within E15 before its impact on the shore of NASA’s Wallops Island Flight Facility, Va. However, the IRT said, no firm conclusions can be drawn with respect to the quantity of FOD introduced to, or already present, within the engine prior to, or at the time of, the explosion, which damaged the Mid-Atlantic Regional Spaceport (MARS), located at the Wallops Island Flight Facility.
The lack of significant particle impact damage to the recovered impeller and other components indicates that there were not gross-levels of FOD present within the system, the IRT found. In addition, there is no clear forensic evidence that FOD directly, or indirectly, led to the engine E15 failure.
Orbital ATK President and CEO David Thompson said Oct. 27 in a conference call with analysts that the company has four NASA Cargo Resupply Services (CRS) missions in the next year: December, March, May and either late September or early October. The December and March missions will take place on United Launch Alliance (ULA) Atlas V rockets from Cape Canaveral Air Force Station, Fla., while the May and September/October launches will take place on a re-engined Antares from Wallops Island. Thompson’s remarks came courtesy of the Seeking Alpha website.
ULA is a joint venture of Lockheed Martin [LMT] and Boeing [BA].