The first crewed flight of the Boeing CST-100 Starliner will be delayed by at least a week and a half to replace a faulty valve on the Atlas 5 launch vehicle. Late on May 7, NASA announced the launch of the Crew Flight Test (CFT) mission. The launch, which was postponed on May 6 due to valve failure in the upper part of the Centaur rocket, was postponed to May 17 at 18:16 ET.

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

Tory Bruno, ULA’s president and chief executive officer, said at a briefing after the May 6 cleanup that the concern may have caused the valve to approach its 200,000-cycle life. He noted that the valve was vibrating at a frequency of 40 hertz.

He said at the time that engineers would check whether these vibrations were for full valve cycles. In such a case, ULA will need to replace the valve. However, if the valve moves partially, it may not be close to its design life and can be salvaged. Officials said at a briefing that they might try the launch again the next day, but later revised the launch date to May 10, the next possibility before this latest delay.

In NASA’s statement regarding the new delay, it was stated that while the vibration of the valve decreased when the valve was closed after cleaning, the vibration returned twice during the fuel evacuation of the rocket.

“After evaluating the valve’s operational history, data signatures from the launch attempt, and risks associated with continued use, the ULA team determined that the valve was beyond qualification and mission managers agreed to remove and replace the valve,” NASA said.

The new date is slightly later than the estimates announced in the briefing. Bruno said the valve replacement procedure, which involves installing instruments to support the scene, takes several days. “It is unlikely that we will be ready to make another attempt before Sunday [12 травня]”, – said.

This was not one of NASA’s designated launch dates; Return dates for the first launch attempt were 7, 10 and 11 May. Steve Stich, NASA’s commercial crew program manager, estimated that the next launch opportunity after May 11 would be May 14 or 15.

There is no discussion about launching Starliner to the International Space Station, where it will dock, in the near future. “We intentionally cleared our summer schedule to give us plenty of runway for this CFT mission,” NASA’s ISS program manager Dana Weigel said at the briefing.

NASA said the two astronauts participating in the CFT mission, Butch Wilmore and Suni Williams, will remain at Kennedy Space Center in pre-flight quarantine during the latest delay.