BOEING: Starliner’s thruster performance receiving close scrutiny from NASA.

The NASA 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.

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.

And from the comments:

I will give Boeing a semi-pass on this one. The thrusters were used in a manner they would never be used during a mission, so it’s probably not surprising they had issues after that. However, it is concerning that one thruster never fired at all. That is certainly not acceptable, and unfortunately, may be yet another failure of Boeing’s quality assurance culture. In light of this additional finding, there is absolutely no way they should be allowed to do a manned flight without a successful unmanned demo. Considering Dragon had yet another great flight adds more fuel to that argument. If SpaceX can do it, why can’t Boeing?

Good question.