Controllers postponed Boeing‘s CST-100 Starliner’s crewed test flight on May 6 due to a valve issue with the rocket, pushing the launch forward by a minimum of four days.
Just over two hours before the planned 10:34 p.m. Eastern launch from Cape Canaveral Space Force Station in Florida, the Atlas 5 rocket’s launch director opted to scrub the mission, known as the Crew Flight Test.
The concern centered on an oxygen relief valve on the rocket’s Centaur upper stage. Dillon Rice, the ULA launch commentator, explained on NASA TV that the team was apprehensive about the valve’s behavior and decided, out of caution, to halt launch operations for the day.
During a subsequent press conference, ULA CEO Tory Bruno disclosed that the valve was emitting a buzzing sound at around 40 hertz, audible to teams at the launch pad. Although closing the valve stopped the buzzing, it necessitated scrubbing the launch to adhere to flight rules prohibiting alterations to the Centaur’s state while crewed.
While backup launch opportunities were set for May 7, 10, and 11, the next attempt hinged on whether the valve required replacement.
Bruno indicated that if the vibrations represented full motions of the valve, nearing its rated life of 200,000 cycles, replacement would be necessary, likely delaying the launch to the following week.
However, engineers were assessing data to determine if the buzzing indicated less than full motion, potentially allowing a launch as early as May 7.
NASA later announced a projected launch no earlier than May 10, ruling out May 7, to grant teams additional time for valve data analysis.
The scrub came after NASA astronauts Butch Wilmore and Suni Williams had boarded Starliner, reporting no issues with the spacecraft. Preparations were proceeding well ahead of schedule until the decision to scrub.
The Crew Flight Test represents the final evaluation of the Starliner spacecraft before NASA certifies it for International Space Station crew rotation missions, following two uncrewed flights in December 2019 and May 2022.
After launch, the spacecraft is slated to dock with the station within a day and remain for about a week before undocking and landing at White Sands, New Mexico.
Ahead of the flight, Wilmore and Williams expressed readiness to handle a launch scrub gracefully, drawing from experiences like Bob Behnken’s advice following the weather-related scrub of the first Crew Dragon spacecraft’s launch in 2020.
