Today, Ars Technica reports that the mission also had failures in its thruster performance. The mission failure reported at the time that because of the timer error, the thrusters on the service module fired much more than the mission profiles call for. They're now saying that, “Many of the elements of the propulsion system were overstressed.”
The NASA [initial information] release did not mention thruster performance, but an agency source told Ars that engineers are looking closely at the performance of the Starliner propulsion system. In addition to four large launch abort engines, the service module has 28 reaction control system thrusters, each with 85 pounds of thrust and 20 more-powerful orbital maneuvering thrusters, each with 1,500 pounds of thrust. [Note: text in brackets added - SiG.]Ars asked for a comment from Boeing, and they were given the following statement:
During the post-flight news conference Jim Chilton, Boeing's senior vice president of the Space and Launch division, said the service module thrusters were stressed due to their unconventional use in raising Starliner's orbit instead of performing one big burn. As a result, the company had to shut down one manifold, which effectively branches into several lines carrying propellant to four thrusters. "We even shut down one manifold as we saw pressure go low 'cause it had been used a lot," he said.
The NASA source said eight or more thrusters on the service module failed at one point and that one thruster never fired at all.
"After the anomaly, many of the elements of the propulsion system were overstressed, with some thrusters exceeding the planned number of burns for a service module mission. We took a few cautionary measures to make sure the propulsion system stayed healthy for the remainder of the mission, including re-pressurizing the manifold, recovering that manifold’s thrusters. Over the course of the mission we turned off 13 thrusters and turned all but one back on after verifying their health."In my opinion, after Sunday's successful SpaceX test, this puts Boeing a bit behind the eight ball. After all, the emphasis up 'till now has been (my interpretation) trying to determine if they could claim the mission met all requirements. Since the Starliner capsule never completed its primary mission of docking at the ISS, it seemed to be a stretch and everything else had to be superb. With these apparent thruster issues, it seems to me Boeing would have to show the specifications for the thruster system and demonstrate, line by line, how they proved it worked per the specifications and here I'm assuming the design went through Critical Design Reviews where both Boeing and NASA signed off on the requirements, agreeing to them.
Two weeks ago, NASA and Boeing committed to a two month schedule to complete the analysis of the timer anomaly, while concurrently determining if another test flight is required. My bet is that they'll have to redo this test flight essentially in its entirety.
Starliner on the pad on 12-19-19. Trevor Mahlmann photo.
During Sunday's post-testflight press conference, NASA Administrator Jim Bridenstine repeatedly emphasized that he wants more than one ride to the ISS. He wants both Boeing and SpaceX to succeed and he wants a vibrant private sector in space. Everything he said sounded reasonable to me. Both Bridenstine and Elon Musk commented that they could have the Crew Dragon ready to fly to the ISS by mid-March, but that with other considerations on the table they collectively said “second quarter.” I'll be keeping my ears and eyes open for any changes.