Starliner launch attempt scrubbed

Updated 1:50 p.m. Eastern.

KENNEDY SPACE CENTER, Fla. — A last-minute problem scrubbed the Atlas 5 launch of Boeing’s CST-100 Starliner on its first crewed flight June 1.

A ground computer halted the countdown 3 minutes and 50 seconds before the scheduled 12:25 p.m. Eastern launch of the Crew Flight Test (CFT) mission with NASA astronauts Butch Wilmore and Suni Williams on board. Controllers did not immediately disclose what triggered the hold in the countdown beyond a brief statement from NASA that the “computer ground launch sequencer not loading into the correct operational configuration after proceeding into terminal count.”

“The system was unsuccessful in verifying the sequencer’s necessary redundancy,” NASA said in a statement about 90 minutes after the scrub.

Because Starliner has an instantaneous launch window, the hold scrubbed the launch attempt. There are backup launch opportunities June 2, 5 and 6.

NASA, Boeing and United Launch Alliance worked through minor issues during the countdown. About two hours before the scheduled liftoff, launch controllers reported a problem with valves that control the flow of liquid oxygen and liquid hydrogen into the Centaur upper stage to top off its tanks. Engineers concluded that faulty sensors caused the valves to close and switched to a backup set of sensors, which allowed topping to resume.

Less than 20 minutes before liftoff, spacecraft controllers noted a problem with fans that circulate air in the pressure suits Wilmore and Williams were wearing. The fans were working again a few minutes later.

The helium leak found after the previous scrubbed launch attempt May 6 was not an issue with this launch attempt. Controllers reported that the leak rate was acceptable and, in fact, had appeared to decrease.

It is unclear how long this issue night delay the launch, although controllers were initially working to set up for a June 2 launch.

A slip beyond June 6 could lead to a significantly longer delay. Steve Stich, NASA commercial crew program manager, said at a May 31 prelaunch briefing that ULA would need time to replace batteries in the rocket if the vehicle does not launch by June 6. Gary Wentz, vice president of government and commercial programs at ULA, said that battery replacement work would take about 10 days.

NASA officials said earlier this year that they needed to complete the certification of Starliner by November or December so that the first operational mission, Starliner-1, can launch in early 2025 as currently planned. At the prelaunch briefing May 31, Stich declined to say if that schedule will hold even with the delay in launching CFT.

“That will be something that we will work on after the flight,” he said of certification. “The path to Starliner-1 clearly is through Crew Flight Test. That is the most important thing we have towards certification.”

Mark Nappi, Boeing vice president and commercial crew program manager, said 80% of the certification plan is already in place and is scheduled to be done by November, but the remainder depends on what happens during the CFT mission, including what in-flight anomalies take place that need to be resolved.

“The longer it takes to fly CFT, the shorter that period becomes for us to review that data,” he said. “Getting the certification review done as soon as we can is important regardless of when we fly.”