Boeing Starliner Crewed Flight Test Postponed Amid Helium Leak Discovery

The inaugural crewed launch of Boeing's CST-100 Starliner spacecraft has been rescheduled to no earlier than June 1, 2024, following the discovery of a small helium leak in the vehicle's service module. This postponement marks the latest in a series of delays for the critical NASA Commercial Crew Program mission, which aims to certify a second American spacecraft for transporting astronauts to and from the International Space Station (ISS).

Chronology of Technical Challenges

The mission, known as the Crew Flight Test (CFT), was initially scrubbed on May 6, just two hours before liftoff, due to an anomalous 'buzzing' sound from an oxygen relief valve on the United Launch Alliance (ULA) Atlas V rocket's Centaur upper stage. While ULA addressed the valve issue, subsequent data reviews by the mission team uncovered a separate, more intricate problem within the Starliner spacecraft itself.

Engineers detected a small helium leak in a flange on a single reaction control system (RCS) thruster within the Starliner's service module. The helium system is crucial for pressurizing the spacecraft's propellant lines, enabling the thrusters to function correctly for orbital maneuvering and attitude control.

Engineering Analysis and Path Forward

Teams from NASA and Boeing are conducting a thorough analysis to understand the full impact of the helium leak. This includes pressurizing the system to replicate flight conditions and evaluating potential operational workarounds. The leak has been determined to be stable and does not pose a risk of catastrophic failure, but mission managers are proceeding with an abundance of caution to ensure all system parameters are fully understood before committing to launch.

1. Initial Scrub: Caused by a faulty oxygen relief valve on the Atlas V Centaur upper stage.
2. Second Issue Identified: A small but persistent helium leak in the Starliner's service module propulsion system.
3. New Launch Target: Now scheduled for no earlier than 12:25 p.m. EDT on Saturday, June 1, 2024.

Mission Significance and Crew Safety

We are taking our time and following our standard mission management team process. We are letting the data drive our decision making as we continue to work through this latest issue and proceed toward launch of Starliner's first crewed flight.

The CFT mission, crewed by NASA astronauts Butch Wilmore and Suni Williams, represents the final developmental milestone before Starliner can be certified for long-duration operational missions to the ISS. Successfully completing this flight is essential for providing redundant, U.S.-based crew transportation to low-Earth orbit, a key objective of the Commercial Crew Program.

The ongoing delays underscore the rigorous safety protocols inherent in human spaceflight. Both NASA and Boeing have reiterated that ensuring the safety of the crew is the primary consideration, and the spacecraft will only launch when teams are confident in its performance and reliability.