Boeing: Starliner error would have been caught with expanded testing
By Cat Hofacker|February 28, 2020
Complete findings from NASA-Boeing review coming next week
The clock error that prevented Boeing’s CST-100 Starliner capsule from reaching the International Space Station in December could have been found with more complete testing, a Boeing official told reporters Friday.
The capsule’s uncrewed flight test was cut short soon after it separated from the United Launch Alliance rocket that blasted it into space. Starliner should have fired its Orbital Maneuvering and Attitude Control thrusters in an orbital insertion burn, meant to put the spacecraft on a path to intersect with the International Space Station, but due to a coding error the Mission Elapsed Time clock reflected an incorrect time. The thrusters did not fire and the capsule returned to Earth without going to ISS.
The docking would have been the design’s first visit to the station, and one of the final tests if NASA is going to certify Starliners to ferry astronauts to and from ISS as part of the Commercial Crew program. Independent investigators on a review panel have questioned the thoroughness of Boeing’s prelaunch testing.
Ahead of the launch, Boeing sent avionics boxes loaded with Starliner’s flight software to the ULA facility in Denver to test the integration of the Atlas V rocket with the capsule during launch. In hindsight, engineers wish they had kept the simulation going after the capsule separated from the rocket. “If we would have run the integrated test with ULA through the first orbital insertion burn timeframe, we would have seen that we would have missed the orbital insertion burn,” said John Mullholland, Boeing’s Commercial Crew program manager, in a Friday teleconference.
Instead of simulating an entire mission from launch to docking, “the team decided they would rather run multiple tests with chunks of the mission,” Mullholland said. “Going forward, for every flight, we will do launch to docking and undocking to landing in addition to the other tests we were doing in our qualification testing.”
Mullholland stressed that the oversight was “not a matter at all of the team consciously shortcutting,” nor is this approach “unique to Boeing and the Boeing Starliner.” In fact, the company has briefed “other programs outside of Boeing” on its findings “as part of our commitment to make human spaceflight safer.”
The clock error was one of two software problems discovered during the uncrewed flight. When the capsule missed its insertion burn, engineers immediately began scrubbing the software. In addition to the clock error, they found a coding error that could have complicated Starliner’s return to Earth had the capsule been able to reach the station. After undocking, the service module must separate from the capsule, and position itself for reentry with valve-mapping software that determines the combination of thrusters to fire. The coding error could have propelled the service module into the capsule instead of away from it.
The independent review team will announce the full results of its investigation during a March 6 teleconference, NASA said in a press release Friday. In the meantime, Mullholland said, the panel had given Boeing dozens of action items it must complete for Starliner before the capsule could fly again. This includes a full audit of the million lines of software code.
“We understand what we need to do to make this right; we’re going to make it right and we’re going to have a fantastic spacecraft going forward,” he said.
Nevertheless, he said, “it’s a little too early” to determine if a second uncrewed flight test will be needed.
“The timeframe between us and the next flight is really going to be determined by how long it takes for us to work through those corrections,” he said.
NASA says it wants Boeing and fellow Commercial Crew contractor SpaceX to be flying crews in the “first part” of 2020, two years and some odd months after the original 2017 flight dates. A two-person crewed flight to ISS in the SpaceX Crew Dragon capsule is tentatively scheduled for May 7, but the agency has said that date could slip.