Tuesday, June 18

NASA, Boeing further delay Starliner Crew Flight Test launch amid ongoing helium leak review – Spaceflight Now

A United Launch Alliance (ULA) Atlas 5 N22 rocket with Boeing’s Starliner spacecraft on top as seen the day before its planned May 6 launch. A problematic valve caused the mission to scrub two hours before liftoff. Image: Michael Cain/Spaceflight Now

Ongoing analysis of a helium leak on Boeing’s Starliner spacecraft forced NASA and Boeing to delay the Crew Flight Test mission further.

A blog post, issued late on Friday afternoon, announced a new target launch date for Starliner CFT with NASA astronauts Butch Wilmore and Suni Williams of no earlier than Saturday, May 25, at 3:09 p.m. EDT (1909 UTC).

The spacecraft will launch atop an Atlas 5 rocket from United Launch Alliance to dock with the International Space Station for a roughly eight-day stay before returning to Earth.

Heading into a May 6 launch attempt, a leak was detected in the pressurization system that allows the fuel and oxidizer on the Starliner’s Service Module (SM) to flow correctly to their designated thrusters when called upon. The SM features 28 reaction control system (RCS) thrusters and 20 orbital maneuvering and attitude control (OMAC) thrusters.

The helium leak was connected to a single RCS thruster and was determined to be within flight limits on May 6.

However, during the countdown, a pressure relief valve on the Atlas 5 rocket’s Centaur upper stage was acting up and the mission was scrubbed about two hours before liftoff. The rocket was rolled back into ULA’s Vertical Integration Facility (VIF) where the valve was replaced, tested and cleared for flight.

While inside the VIF, Boeing decided to further study and test the helium leak to provide greater assurance that it wouldn’t impact the mission.

Teams brought the spacecraft up to flight pressure on May 15 and determined that “the [helium] leak in the flange is stable and would not pose a risk at that level during flight,” NASA and Boeing said in a joint blog post.

The update also noted that “testing also indicated the rest of the thruster system is sealed effectively across the entire service module.”

Helium is pressurized to a certain level during the run-up to launch as well as during the rocket’s ascent in the event that the thrusters and the launch abort engines would be needed for an abort and a quick escape for the astronauts.

Once the spacecraft reaches orbit, it would vent off some of the helium intentionally.

While the testing this week had some positive indications, Boeing and NASA decided to take more time for Boeing “to develop operational procedures to ensure the system retains sufficient performance capability and appropriate redundancy during the flight.”

“As that work proceeds, NASA’s Commercial Crew Program and the International Space Station Program will take the next few days to review the data and procedures to make a final determination before proceeding to flight countdown,” the blog stated.

Spaceflight Now reached out to NASA and Boeing for an interview regarding the update. A NASA spokesperson said there was no briefing planned until the standard pre-launch briefing late next week. Meanwhile, a Boeing spokesperson declined an interview, though presumably, will have a representative participate in the forthcoming briefing. NASA did not respond to requests for interviews.

Following the May 6 launch scrub, and while this work has been ongoing, Wilmore and Williams flew back to Houston, Texas, to be with their families and continue training for the mission. They are due to return to Florida “closer to the new launch date.”

The Starliner spacecraft was selected alongside SpaceX’s Crew Dragon capsule to become the two vehicles NASA would use to transport its astronauts to and from the ISS. Boeing and SpaceX received $4.2 billion and $2.6 billion respectively for the development work and the first six operation missions.

SpaceX launched its uncrewed demonstration mission in 2019 and the two-member crewed Demo-2 flight in May 2020. To date, Dragon has flown 53 people across 13 mission, four of which were non-governmental private flights.

Boeing’s Orbital Flight Test in 2019 ran into multiple issues, including a software problem that prevented it from being able to safely dock to the ISS. The second Orbital Test Flight (OFT-2) was delayed a year due to a corrosion problem in some of the propulsion system valves.

Teams were optimistic about a 2023 launch of the CFT mission, but the mission was delayed until 2024 as they worked through questions concerning the parachutes’ soft links and either mitigated or removed about a mile of flammable tape within the spacecraft.

source: spaceflightnow.com