United Launch Alliance Delays Starliner Launch to Replace Suspect Valve in Atlas 5 Rocket

Following a launch scrub on Monday, May 6, United Launch Alliance (ULA) managers have made the decision to return the Atlas 5 rocket, which is carrying Boeing's Starliner astronaut ferry ship, to its processing facility. This is in order to replace a suspected valve, consequently delaying the next launch attempt to at least May 17, NASA reported in an official blog post on Tuesday.

The new "no-earlier-than" launch target from Florida's Cape Canaveral Space Force Station is scheduled for 6:16 p.m. EDT, a week from Friday. This new date will allow engineers to conduct the necessary valve repair while also coordinating with the U.S. Eastern Range launch schedule to ensure a smooth rendezvous with the International Space Station.

The Issue and Preparations

The culprits behind the delay were identified as a pressure relief valve in the rocket's Centaur upper stage liquid oxygen plumbing. This valve failed to seat properly during the final stages of propellant loading, producing an audible hum due to its rapid opening and closing. While ULA engineers could have potentially forced the valve in place under normal circumstances, stringent flight rules for the Starliner mission prohibited any changes to the rocket's "fueled state" while astronauts were on board, leading to the scrubbed launch.

After evaluating the valve history and data signatures from the failed launch attempt, the ULA team concluded that the valve had exceeded its qualification. As a result, mission managers agreed to remove and replace the valve. The plan is to transport the Atlas 5 and its mobile launch platform back to the nearby Vertical Integration Facility for the valve replacement and subsequent testing. Once completed, the rocket will be moved back to the pad for normal pre-launch preparations.

Boeing's Starliner, which is aiming to rival SpaceX's Crew Dragon spacecraft, has faced significant delays and technical hiccups, costing Boeing over $1 billion to rectify. On the other hand, SpaceX's Crew Dragon has successfully completed numerous flights, carrying astronauts, cosmonauts, and civilians into orbit, highlighting the contrast between the two programs.