Boeing continues to work through the software errors and communications issues that arose during December’s uncrewed Orbital Flight Test of the CST-100 Starliner commercial crew spacecraft. Boeing is implementing the findings of a joint NASA/Boeing Independent Review Team (IRT) and identifying gaps in its software testing, while it continues to investigate why Starliner’s communications system was not able to connect on more than 30 occasions.

John Mulholland, Vice President and Program Manager for the Boeing Commercial Crew Program, briefed reporters today on the company’s progress. After highlighting what went right with the mission — a perfect launch on United Launch Alliance’s Atlas V rocket, many successful on-orbit tests, and a nearly pinpoint landing in New Mexico — he acknowledged what did not.

Software errors were responsible for the two highest profile anomalies. First, the Mission Elapsed Timer on Starliner was off by 11 hours. Starliner is designed to separate from the Atlas V before attaining orbit and fire its own engines to reach orbit and finish the journey to the International Space Station (ISS). Because of the timing error, when it separated the automated system thought the orbital insertion burn already had taken place. The communications problem prevented ground controllers from immediately commanding the correct engine burn sequence.

The spacecraft did reach orbit, but only after consuming much more fuel than planned. It did not have enough to rendezvous and dock with the ISS so did not complete that part of the test flight.

Starliner remained in orbit for two days conducting other tests while engineers on the ground scoured the software to determine what went wrong and look for other problems. They found one just in time. Another software error could have led to a catastrophic ending during reentry and landing.

Mulholland said today that Boeing learned “hard lessons” from the flight, one of which is to do more software testing. Extensive simulations were performed to verify the Atlas V and Starliner systems worked properly together, but the tests ended at the point where the two separated so did not include checking to see that Starliner grabbed the correct Mission Elapsed Time from the rocket. That time is loaded into the rocket’s computers only at terminal count just before launch. Starliner had taken the time from when the rocket was powered up hours earlier. The reentry software error that was caught in time was because an incorrect emulator was used during tests.

Mulholland stressed that the decision to break the testing into discrete “chunks” was only because the engineering team thought it was “logical” to do it that way, not because of cost. “It was not a matter at all of the team consciously shortcutting what they believed was appropriate.” From now on, however, Boeing will run simulations all the way from launch to docking, as well as from undocking to landing.

“Looking back, it’s easy to determine that we should have” done that testing, but “I think the sensitivity of the Mission Elapsed Timer was not recognized by the team and wasn’t believed to be an important aspect of the mission.”

The NASA/Boeing IRT has completed its work on the software issues, but has more to do on the communications problems. Mulholland said today they are now focused on antenna selection and some of the algorithms. There were 37 communications dropouts, 36 of which occurred over northern Europe and Russia.

Next Friday, NASA and Boeing will provide a briefing on the results of the IRT, although Mulholland said Boeing has asked the IRT to extend its service through the end of March to continue working on the communications issue.

Boeing is developing Starliner as a Public-Private Partnership (PPP) with NASA under a fixed price contract, as is SpaceX with its Crew Dragon. Some have questioned why an IRT was set up to look at this Boeing problem when one was not required after SpaceX’s anomaly last year while preparing for an In-Flight Abort test that resulted in the destruction of its Crew Dragon capsule.

Mulholland said this IRT was set up at Boeing’s request. “On launch day, we specifically asked NASA to partner with us on an IRT. I don’t know how others might approach it.” He added that the IRT has provided a “tremendous amount of value.”

He confirmed that it is up to NASA to decide whether or not Boeing must repeat the uncrewed flight test or move on to the next step, a crewed flight test. Boeing took a $410 million charge against earnings in the fourth quarter of 2019 in case a repeat is required. His message today was that they will fly with a crew when they are ready and he is not willing to make any commitments at this point.