The launch of a United Launch Alliance Atlas 5 rocket carrying Boeing’s unlucky Starliner capsule was delayed for another four days, from Friday to next Tuesday, to give engineers time to ensure a small helium leak in the crew ship’s propulsion system has been resolved. , officials said Tuesday.
Liftoff from Pad 41 at Cape Canaveral Space Force Station is now scheduled for 4:43 p.m. EDT on May 21, setting up a docking at the International Space Station the following afternoon. The flight is expected to end with a landing in White Sands, New Mexico, around May 30.
Mission commander Barry “Butch” Wilmore and co-pilot Sunita Williams expected to take off in the Starliner first piloted flight last Monday. They were in the process of strapping down when the countdown was canceled due to a problem with an oxygen pressure relief valve on the Centaur rocket’s upper stage.
Two days later, the Atlas 5 was removed from the launch pad and back to the nearby ULA Vertical Integration Center, where the suspect valve was replaced. The tests confirmed that the rocket is ready for another launch attempt.
The unrelated helium leak in the Starliner’s booster pressurization system was noted during last week’s countdown, but remained within safe limits for flight. After the Atlas 5 and Starliner were returned to the VIF for oxygen valve replacement, managers decided to take a closer look at the helium issue.
The leak was detected in the distribution manifold within one of four “doghouse” sets spaced around the exterior of the Starliner’s drum-shaped service module. Each doghouse has four orbital maneuvering and attitude control – OMAC – thrusters and four small reaction control system maneuvering jets.
Pressurized helium gas is used to push propellants into the rocket engines in each doghouse. The leak was traced to a flange on a single RCS booster.
The screws have been retightened and engineers believe the system is ready for flight. But managers decided to pressurize the helium lines throughout the spacecraft to ensure that the lines are, in fact, free of leaks or within acceptable limits.
“As part of the testing, Boeing will bring the propulsion system to flight pressurization, just as it does before launch, and then allow the helium system to naturally release to validate existing data and strengthen the flight logic,” he said. the company in a statement. declaration.
“Mission teams have also completed a full review of data from the May 6 launch attempt and are not tracking any other issues.”
Wilmore and Williams, both veteran Navy test pilots and astronauts with four flights to the station between them, flew back to Johnson Space Center in Houston last Friday for additional simulator training. They are expected to fly back to Florida later this week to prepare for another launch attempt.
Starliner is one of two commercially built crew ships ordered by NASA following the retirement of the space shuttle program in 2011. SpaceX won a contract valued at $2.6 billion for the development of the company’s Crew Dragon spacecraft, and Boeing received US$4.2 billion to develop the Starliner.
The goal was to stimulate the development of independent, commercially operated spacecraft capable of transporting astronauts to and from the International Space Station. Spacecraft from different vendors will allow NASA to continue sending crews to the space station even if a problem derails one company’s spacecraft.
SpaceX launched its first two-man crew in 2020. Since then, the company has launched eight NASA-sponsored crew rotation flights to the station, three commercial research missions to the lab, and a privately funded two-man, two-man trip. women. to low Earth orbit. In total, 50 people flew into space aboard Crew Dragons.
Wilmore and Williams will be the first astronauts to fly aboard a Starliner after a series of technical failures that included major software problems during an initial unpiloted test flight in December 2019 and corroded propulsion system valves that delayed a second uncrewed test mission to May 2022.
The second test flight was a success, but engineers were faced with additional questions about the parachute harness connectors and protective tape wrapped around the wiring that posed a fire risk in the event of a short circuit. Work to fix these and other issues has delayed the first pilot launch until this month.
The problem with the Atlas 5’s oxygen valve was the responsibility of United Launch Alliance. The helium leak responsible for the latest delay is on the Starliner list, but it is apparently a relatively minor issue and would not have prevented the launch last week.
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