The Starliner launch was delayed to mid-May

WASHINGTON — The first crewed flight of the Boeing CST-100 Starliner will be delayed for at least another week and a half to replace a faulty valve on the Atlas 5 launch vehicle.

NASA announced late May 7 that the Crew Flight Test (CFT) mission, whose May 6 launch was canceled due to a valve malfunction in the Centaur rocket’s upper stage, had been rescheduled for no later than May 17 at 6:16 p.m. Eastern.

The long delay will allow United Launch Alliance to return the rocket to the Vertical Integration Facility (VIF) hangar near the pad to replace Centaur’s liquid oxygen pressure regulating valve. This valve began to oscillate after the stage was loaded with liquid oxygen, creating a humming noise noticed by the launch pad crew.

In a press conference after the May 6 scrub, Tory Bruno, ULA’s president and CEO, said the concern was that vibration could cause the valve to approach its rated life of 200,000 cycles. He noted that the valve was vibrating at a rate of 40 Hz.

Next, he said, engineers will check whether those vibrations include full revolutions of the valve. If so, ULA will have to replace the valve. However, if the valve only moves partially, it is possible that the valve is not near its design life and can be retained. Officials said at the press conference that they might try to launch again the next day, but later revised the launch date to the next opportunity, May 10, before this latest delay.

In NASA’s statement about the new delay, the agency said that while the valve vibration was mitigated once the valve was closed after scrubbing, that vibration returned twice as propellant was being unloaded from the rocket.

“After evaluating the history of the valve, data signatures from the launch attempt, and evaluating risks related to continued use, the ULA team determined that the valve exceeded its qualifications and mission managers agreed to remove and replace the valve,” NASA stated.

The new date is somewhat later than the forecasts presented in the briefing. The valve replacement procedure, which involves installing tools to support the stage, takes several days, Bruno said. “It is unlikely that we will be ready to make another attempt before Sunday [May 12],” He said.

This was not one of the days NASA had set as a launch date, with backup dates for the original launch attempt being May 7, 10 and 11. Steve Stich, director of NASA’s Commercial Crew Program, estimated the next available launch opportunity after May 11 would be May 14 or 15.

There is no conflict in the near-term schedule for a launch on the International Space Station, where the Starliner spacecraft will dock. “We intentionally canceled our summer schedule to give us plenty of runway for this CFT mission,” Dana Weigel, NASA’s ISS program manager, said at the press conference.

NASA said the two astronauts leading the CFT mission, Butch Wilmore and Sonny Williams, will remain at Kennedy Space Center in pre-flight quarantine until this final delay.

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