Boeing Starliner's On-Orbit Thruster Review at the ISS

NASA and Boeing mission managers are conducting a comprehensive engineering review of the CST-100 Starliner's propulsion system while it remains safely docked at the International Space Station. This in-depth analysis follows the detection of multiple helium leaks and several reaction control system (RCS) thruster failures during the spacecraft's journey to the orbiting laboratory, making vehicle performance and crew safety the mission's top priorities.

On-Orbit Propulsion System Anomalies

During its crewed flight test, Starliner experienced five distinct helium leaks within its service module, which pressurizes the propulsion system. Additionally, five of the 28 RCS thrusters failed to fire as commanded during critical orbital maneuvers, including the final approach to the ISS. While mission controllers successfully recovered four of the thrusters, the underlying cause of these anomalies requires thorough investigation.

Detailed Engineering Analysis Aboard the ISS

With the spacecraft securely attached to the station, engineering teams on the ground are leveraging the stable microgravity environment to conduct a series of diagnostic tests. This includes performing "hot-fire" tests on the affected thrusters to gather performance data and analyzing telemetry to understand thermal conditions and system pressures that may have contributed to the malfunctions.

1. Helium Leak Characterization: Identifying the precise location and rate of decay for each of the five detected helium leaks to model their potential impact on the return journey.
2. Thruster Performance Verification: Systematically testing the RCS thrusters to confirm their functionality and understand the root cause of the previous intermittent failures.
3. Data Correlation: Cross-referencing flight data with ground test results to determine if a common failure mode connects the helium leaks and thruster issues.

Implications for Certification and Crew Safety

The successful resolution of these propulsion issues is a critical milestone for certifying Starliner for future crew rotation missions under NASA's Commercial Crew Program. The primary focus remains the safety of astronauts Butch Wilmore and Suni Williams, ensuring the spacecraft is fully capable of performing a safe de-orbit burn and atmospheric reentry.

We are taking our time and following our standard mission management team process. Starliner is performing well in orbit while docked to the space station. We are strategically using the extra time to clear a path for some critical station activities while completing our analysis.

Next Steps and Return Schedule

The mission's return to Earth has been postponed to allow engineers sufficient time to complete their data review and system analysis. NASA and Boeing will hold further technical reviews before finalizing a new undocking and landing date. The ongoing investigation represents a crucial phase of in-flight vehicle validation.

This meticulous on-orbit review underscores the rigorous safety culture inherent in human spaceflight. By thoroughly addressing these unexpected challenges, NASA and Boeing aim to ensure the Starliner is a robust and reliable vehicle for transporting astronauts to and from low-Earth orbit, reinforcing the resilience of space exploration endeavors.