NASA says it can’t pinpoint what caused the explosion of Orbital ATK’s unmanned Antares rocket shortly after launch in a cargo resupply mission for the International Space Station on Oct. 28, 2014.
In its long-awaited report on the Antares blast — publicly issued in executive summary a full a year and one day after the mission failure — the space agency said it couldn’t find a single “root cause” of the blast.
It said the “proximate cause” of the Orbital Antares rocket failure was an explosion within the Aerojet-modified AJ-26 rocket engine.
Investigators also identified “three credible technical root causes, any one or combination of which could have resulted in the engine failure.”
Last month, Aerojet agreed to pay Orbital $50 million to settle a dispute over the rocket-engine company’s role in the explosion. The Antares rocket used in that mission was built a Soviet-era engine modified for Antares use by Aerojet.
Last fall’s explosion of an Antares rocket shortly after launch from NASA’s Wallops Flight Facility in Virginia also resulted in the loss a cargo spacecraft headed for the ISS. Orbital has yet to resume cargo shipments to the space station.
Orbital says it no longer will use those engines in its rockets, yet NASA recently questioned the company’s ability to resume ISS missions anytime soon. The company insists that it’s on track to resume Antares launches from Wallops by mid-2016.
Last October’s launch was conducted under a license from the Federal Aviation Administration, which coordinated with NASA in its probe.
William Gerstenmaier, associate administrator for human exploration and operations at NASA, said the protracted probe into the “unfortunate event” was needed to learn how to improve launch vehicle dependability and safety.
“The findings from this team will provide a basis to begin discussions on future areas for improvement,” Gerstenmaier said. “Even though not all recommendations will be implemented as written, all the recommendations will enable positive lessons for the agency.”
In addition to technical findings and recommendations, the report addresses how to improve prelaunch communication between NASA and its launch-services contractors under the agency’s Commercial Resupply Program.
As for that “root cause” conundrum, investigators identified a turbopump problem in the Antares engine but couldn’t determine what caused that.
One possibility is that the engine lacked “design robustness” for certain conditions, another theory is that launch debris clogged the engine, while a big third concern involves a possible manufacturing defect identified by investigators. Orbital previously cited the problem with debris clogging the engine following the company’s own investigation into the explosion.
“All three of these technical root causes would need to be addressed as part of any return to flight efforts for Antares,” NASA said.