Engineers Analyze Boeing Starliner's On-Orbit Performance as NASA Delays Crew Return

NASA and Boeing mission managers have extended the stay of the CST-100 Starliner spacecraft at the International Space Station (ISS) to conduct a thorough analysis of its on-orbit performance. This decision follows the detection of several small helium leaks in the spacecraft's propulsion system and unexpected behavior from five of its Reaction Control System (RCS) thrusters during the initial flight phases. The extended mission allows engineering teams on the ground to gather crucial flight data, ensuring all systems meet performance specifications for a safe return to Earth.

Mission Context: The Crew Flight Test (CFT)

The Crew Flight Test is Starliner's inaugural crewed mission, a critical step in certifying the spacecraft for regular rotational flights to the ISS under NASA's Commercial Crew Program. Piloted by NASA astronauts Butch Wilmore and Suni Williams, the mission's primary objective is to test the vehicle's end-to-end capabilities, from launch and docking to atmospheric re-entry and landing. Such test flights are designed to uncover and resolve unexpected issues in the operational space environment.

Investigating On-Orbit Anomalies

Two primary issues are under intense scrutiny. First, engineers are tracking five distinct helium leaks within Starliner's service module. Helium is used to pressurize the propellant lines, enabling the RCS thrusters to fire. While the leak rates are low and do not pose an immediate risk to the mission, understanding their cause is vital for ensuring propulsion system integrity. Second, five RCS thrusters failed to fire as expected during the final approach to the ISS, although they were later successfully recovered. Teams are analyzing telemetry to pinpoint the root cause, which could be related to thermal conditions or software.

1. Helium Leaks: Five small leaks have been identified in the service module's propulsion system manifolds. The current leak rates are stable and well within safety margins.
2. RCS Thruster Performance: Five of the 28 RCS thrusters were deselected by the flight software during docking operations due to off-nominal performance but were later restored.
3. Data Analysis: The extended ISS stay provides engineers with a unique opportunity to perform on-orbit checkouts and gather more data on system performance before the critical undocking and de-orbit burn.

The Importance of Rigorous Testing

This intensive, real-time analysis of a new crew vehicle highlights the methodical and safety-focused nature of human spaceflight. Identifying and resolving these issues before the spacecraft is certified for operational missions is precisely the purpose of a flight test. The data gathered will lead to hardware and software refinements, ultimately increasing the reliability and safety of the Starliner system for future astronaut crews.

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 flight test objectives.

Future Research and Next Steps

Joint NASA and Boeing teams will continue to analyze telemetry, conduct hot-fire tests of the affected RCS thrusters, and model helium system performance to inform the final plan for undocking and landing. A new return date will be announced once teams are confident that all systems are understood and ready for the dynamic phases of re-entry. The crew remains safe and productive aboard the ISS, participating in both station operations and Starliner flight test activities.

Ultimately, the diligent engineering review of Starliner's on-orbit performance underscores the commitment to crew safety that defines human space exploration. While extending the mission, this period of analysis is an invaluable investment in the future of NASA's Commercial Crew Program and humanity's sustained presence in low-Earth orbit.