Engineers Analyze Starliner's On-Orbit Helium Leaks and Thruster Issues
November 5, 2025
Engineers are rigorously analyzing Boeing Starliner's on-orbit helium leaks and thruster anomalies ahead of its crucial return.
Following its historic first crewed launch, Boeing's CST-100 Starliner spacecraft is under intense engineering scrutiny while docked at the International Space Station (ISS). Mission control teams from NASA and Boeing are meticulously analyzing a series of technical anomalies, including multiple helium leaks and several thruster malfunctions, that occurred during its journey to the orbiting laboratory. The resolution of these issues is critical for the safe return of its crew and the final certification of the vehicle for future operational missions.
A Deep Dive into On-Orbit Anomalies
The primary challenges facing the engineering teams are five distinct helium leaks within Starliner's service module propulsion system and the unexpected failure of five reaction control system (RCS) thrusters during the final phases of its approach to the ISS. These systems are essential for maneuvering the spacecraft in orbit and ensuring a precise, controlled reentry through Earth's atmosphere.
Investigating the Helium Propulsion System
The spacecraft's propulsion system uses helium gas to pressurize propellant lines, enabling fuel and oxidizer to flow to the thrusters. While one small leak was identified and assessed prior to launch, four new leaks emerged once the vehicle reached orbit. Engineers are now conducting tests to understand the precise leak rates and their potential impact on the system's performance for the undocking and deorbit burn.
- Helium Leak Assessment: Teams are analyzing pressure decay data to characterize the five leaks and confirm they pose no risk to the return flight.
- RCS Thruster Analysis: Engineers are investigating the root cause of the thruster failures, which were overcome by the flight crew during docking maneuvers.
- Flight Control System Verification: Extensive software and hardware checks are being performed to ensure all redundant systems are fully operational for reentry.
Significance of the Thruster Malfunctions
The malfunction of several RCS thrusters during rendezvous and docking operations required astronauts Butch Wilmore and Suni Williams to intervene, highlighting the importance of crewed test flights. While the spacecraft docked successfully, understanding why these thrusters failed to perform as expected is a top priority for ensuring the vehicle's automated systems are reliable for future missions.
Our teams are applying a methodical, data-driven approach to understand these issues completely. Astronaut safety remains our absolute top priority as we prepare for Starliner's return journey.
Next Steps for Starliner's Return
Before Starliner can be cleared for its return to Earth, mission managers must formally sign off on the analysis, confirming that the spacecraft's propulsion systems have sufficient capability and redundancy for a safe undocking, deorbit, and landing. The data gathered from this Crew Flight Test is invaluable and will directly inform the final steps needed for NASA to certify the Starliner for long-duration crew rotation missions to the ISS.
These on-orbit challenges, while significant, are a fundamental part of the spaceflight development process. The rigorous engineering investigation underway underscores the meticulous safety culture that governs human space exploration, ensuring new vehicles are thoroughly vetted before they become a cornerstone of humanity's access to low-Earth orbit.
Frequently Asked Questions
The Starliner is on its first crewed flight test (CFT), a mission to certify the spacecraft for regular crew transport to and from the International Space Station (ISS) as part of NASA's Commercial Crew Program.
No. According to NASA, the crew is safe aboard the International Space Station. The issues are with the Starliner spacecraft itself, and mission managers will only approve its undocking and return once they are confident in its safety and performance.
Helium is an inert gas used to pressurize propellant tanks, forcing fuel and oxidizer into the thrusters for orbital maneuvers. A significant leak could potentially impact the performance and redundancy of the propulsion system required for a safe return to Earth.
Ground teams are conducting extensive data analysis and testing of the affected systems while the spacecraft is docked. The primary next step is to clear the spacecraft for a safe undocking from the ISS and subsequent atmospheric reentry and landing in the western United States.