by Douglas Messier
It could take between several weeks and two months for Boeing to work through the valve problems that resulted in the launch scrub of the Starliner spacecraft on Tuesday, a source tells Parabolic Arc. The vehicle will be launched from Florida on an uncrewed flight test to the International Space Station (ISS).
The launch was scrubbed after engineers received what Boeing said “unexpected valve position indications in the propulsion system” of the spacecraft. The signals came from more than half of the 24 propulsion valves in Starliner’s service module, according to the source, who insisted upon anonymity due to not being authorized to speak to media.
The affected valves, which are positioned throughout the service module, supply fuel and oxidizer to Starliner’s attitude control and orbital maneuvering thrusters and launch abort engines. Boeing said it ruled out software errors as a cause of the signals.
A number of the valves are in locations that can’t be reached because the spacecraft was closed out for launch. It is possible that Boeing engineers will need to partially de-stack Starliner from its Atlas V booster and take apart the service module to reach the valves, the source said.
Atlas V and Starliner have been rolled back to the Vehicle Integration Facility. Boeing might be able to launch Starliner in several weeks if engineers can address the problems there, the source said. If they need to return Starliner to Boeing’s Commercial Crew and Cargo Processing facility, a launch might not take place until October.
Boeing has experienced problems with valves in the past. A valve failed to close after the engine shutdown command was issued during a test of Starliner’s abort system in June 2018. The flowing propellant became a flame thrower that set the surrounding desert on fire.
The source said the new valve problems have raised anew concerns about Boeing’s quality assurance practices as the company moves toward flying astronauts to the space station aboard Starliner.
The upcoming flight test will be Starliner’s second attempt to reach ISS. During its first flight in December 2019, a Starliner vehicle was unable to fire its engine properly to reach the space station’s orbit. A subsequent investigation found that software and communications errors combined to prevent Starliner from reaching ISS.
Starliner flew a two-day mission in Earth orbit before successfully landing using parachutes and airbags at the White Sands Missile Range in New Mexico.
If the upcoming flight is successful, NASA astronauts will conduct a flight test of Starliner to the space station. The crewed flight had been scheduled for late this year, but it appears likely the mission will slip into 2022.
Boeing developed Starliner under NASA’s Commercial Crew Program. SpaceX also developed the Crew Dragon vehicle to ferry astronauts to and from the space station under the same program.
SpaceX has conducted three Crew Dragon flights to the station with astronauts aboard since April 2020. The first was a demonstration mission, the other two were conducted on a commercial basis. A fourth flight of Crew Dragon to ISS is scheduled for the end of October.