NASA says it may have discovered the root cause of two consecutive launch failures of Orbital Sciences Corp.’s Taurus XL rocket, a manufacturing defect that could affect the company’s Antares rocket being developed to loft commercial resupply missions to the International Space Station (ISS).
William Gerstenmaier, associate administrator for NASA’s Human Spaceflight and Operations Directorate, says NASA and Orbital investigative teams have traced the problem to a heat-treated frangible rail designed to fracture when a pyrotechnic charge is detonated post-launch to shed the rocket’s payload-fairing shroud.
NASA lost its Orbiting Carbon Observatory (OCO) in 2009 and its Glory climate-monitor in 2011, both on launches of the Taurus XL, when the vehicle’s payload shroud failed to open after separating from the rocket.
“We had thought maybe the charge holder had slumped or moved down and that didn’t allow the frangible rail to fracture properly,” Gerstenmaier said during a Nov. 15 meeting of the NASA Advisory Council’s human exploration and operations committee in Washington. “Our teams kept digging, and it looks like there’s potentially some extrusion problems with the way that material is extruded and the way it is heat treated. It is not uniform along the entire length of the rail.”
Gerstenmaier says both Orbital and NASA investigation teams filed accident investigation reports with NASA in September and December 2011, respectively, both of which failed to determine the root cause of a March 4, 2011, launch failure aboard the Taurus XL that led to the loss of Glory.
Since then, NASA terminated its Taurus XL launch service task order for a relaunch of an identical Orbital Sciences-built OCO spacecraft, though the investigative teams have continued to explore possible root causes of the Glory launch failure. He said the teams have discovered a manufacturing problem “that may be more generic than just to the Taurus,” and that while the investigation into this new line of inquiry is preliminary, the findings and mitigation efforts may affect not only the Taurus XL, but other Orbital launch vehicles as well, including the company’s Pegasus, Minotaur and Antares launchers.
“We had two open items on the fault tree,” Gerstenmaier said of the Glory mishap investigation. “There was a leg we had potentially closed off that wasn’t a concern, but that we now think is the most probable.”
Gerstenmaier said the team “went out and essentially looked in the scrap bin at some fairings, and we actually investigated some other spacecraft that had some rails.” He says investigators kept digging and, “when they did that, they started discovering some things that didn’t look quite right.”
Orbital spokesman Barron Beneski says the company ’s Antares, Pegasus and Minotaur rockets all fly versions of the frangible joint fairing separation system. These rails are located along the seam between the two halves of Orbital’s clamshell-shaped fairing, as well as at the base of the fairing that connects to the launch vehicle itself.
“These come apart to jettison the protective nose cone once the rocket is out of Earth’s atmosphere,” Beneski says. “We have done a great deal of work on this system since the Taurus XL Glory mission failure to ensure the flight worthiness of the system for upcoming missions, including the Antares test flight.”
Gerstenmaier says a report on recent findings is expected in the first quarter of 2013. When asked whether the problem could lead to the loss of cargo slated to fly aboard Antares during a demonstration mission slated for April, he said not to worry.
“We deem this cargo as the expendable cargo,” he says. “We’re careful what cargo we put on these flights, so we can tolerate loss.”
In the meantime, the planned December debut of Antares will slip into 2013 to allow time for clean-up at its Wallops Island launch pad on Virginia's eastern shore in the wake of Hurricane Sandy. The first flight, slated for early next year, will carry a dummy Cygnus cargo carrier along with a secondary payload comprising four cubesats. Orbital's first demonstration to the ISS under NASA's Commercial Orbital Transportation Services (COTS) program is expected to follow three months later.