Starliner’s timer was off—capsule thought engines were firing when they weren’t

Right on schedule Friday morning, an Atlas V rocket launched the Starliner spacecraft into a planned suborbital trajectory. This is a critical mission for NASA and Boeing, as the company seeks to use this test flight to prove its capsule's readiness to launch humans into space next year. After being released by the rocket, Starliner was supposed to use its Orbital Maneuvering and Attitude Control engines to provide the thrust needed to reach a stable orbit and begin the process of catching up to the International Space Station. But that did not happen. During a post-launch news conference, NASA Administrator Jim Bridenstine explained that the mission elapsed timing system had an error in it, with the net effect that the spacecraft thought it was performing an orbital insertion burn, when in fact it was not. The on-board computer then expended a significant amount of propellant to maintain a precise attitude, thinking it had reached orbit. "Today, a lot of things went right," Bridenstine said. "But we did not get the orbital insertion burn we were hoping for." When ground-based controllers realized the problem, they immediately sent a command to begin the orbital insertion burn, but due to a communications problem—which could have been a gap in coverage of NASA's Tracking and Data Relay Satellite System or some spacecraft error—those commands were not received right away by Starliner. So it continued to expend fuel to maintain a precise attitude. By the time the commands got through, Starliner had expended too much fuel to make a safe rendezvous and docking with the International Space Station, the primary goal of this test flight. Boeing's senior vice president of space and launch, Jim Chilton, said the flight control team then put the spacecraft into an orbit so that it can safely return to Earth, for a landing beneath parachutes in New Mexico on Sunday. Although it is possible that the mission, originally planned for seven days, will be extended a day or two, the baseline plan is now to return Sunday morning.

Too early to say

The spacecraft has operated nominally in a number of different ways so far, with good power systems, cooling, and more. However, the inability to perform a docking at the station raised the question of whether Boeing will need to perform a second uncrewed test flight before NASA allows its astronauts to fly on Starliner. “I think it’s too early to know," Bridenstine responded during the news conference. "We don’t know what the root cause is. I’m not saying yes and I’m not saying no." NASA does not have a specific requirement that Starliner must demonstrate a rendezvous-and-docking before it clears Starliner for human flights, but certainly the agency's engineers would feel more comfortable with that task having been performed. In any case, the primary issue appears to be one of software rather than hardware. Boeing may be able to convince NASA that had humans been on board the vehicle, they would have immediately recognized the problem and manually commanded the orbital insertion burn. Whether there is an additional test flight or not, this problem almost certainly delays Boeing's crewed flight of Starliner beyond the first half of 2020. This would, for the time being at least, put SpaceX back into the lead for getting humans back into space from a US-based launch pad. A source said Friday that the company appears to be on track toward a springtime launch of astronauts on board the Crew Dragon vehicle. Looking ahead to Sunday, Boeing must also be concerned about the mission-timing issue when it attempts to bring Starliner back to Earth. The spacecraft has a specific entry sequence, and must perform a series of parachute releases to safely land in the desert. Chilton acknowledged that the company will be looking closely at that problem between now and the landing. "We don’t understand why the spacecraft got off the expected mission elapsed time," he said. "We're certainly going to go and diagnose it."