NASA and Boeing Postpone Starliner's ISS Departure to Address Technical Challenges

NASA and Boeing have announced another delay for the return of the CST-100 Starliner spacecraft from the International Space Station (ISS), now targeting undocking no earlier than June 25. This extension provides mission managers with additional time to meticulously review propulsion system data, specifically addressing the recurring helium leaks and thruster performance issues observed during the spacecraft’s inaugural crewed flight with astronauts Butch Wilmore and Suni Williams.

Mission Context: The Crew Flight Test

The Crew Flight Test (CFT) is the critical final validation step for Boeing's Starliner before it can be certified by NASA for long-duration operational missions to the ISS. The primary objectives are to test the spacecraft's end-to-end capabilities, from launch and docking to atmospheric reentry and landing. A successful CFT would establish a second independent U.S. crew transportation system, alongside SpaceX's Crew Dragon, enhancing assured access to the orbiting laboratory.

Analysis of In-Flight Anomalies

Since its launch on June 5, Starliner has encountered several technical challenges. Mission teams are currently focused on two primary issues: multiple helium leaks within the service module's propulsion system, which pressurizes the thrusters, and the unexpected failure of five Reaction Control System (RCS) thrusters during the final phases of its rendezvous and docking with the ISS.

1. Helium Leaks: Five distinct leaks have been detected in the service module. While the leak rates are low and do not pose an immediate threat, engineers are analyzing their potential impact on the remainder of the mission.
2. Thruster Malfunctions: Five of the 28 RCS thrusters failed to fire correctly during docking. Four were subsequently recovered through software cycling, but the root cause of their initial failure requires further investigation to ensure system redundancy for the undocking burn.
3. Data Review: The additional docked time allows teams on the ground to conduct thorough checkouts and hot-fire tests of the thrusters to better understand their performance before committing to the return flight.

Prioritizing Crew Safety

We are taking our time and following our standard mission management team process. We are letting the data drive our decision-making relative to managing the small helium system leaks and thruster performance we observed during rendezvous and docking.

Next Steps and Return Profile

Engineers will continue to analyze flight data and conduct system tests while Starliner remains docked. The new target departure date of June 25 is provisional and contingent on resolving these technical queries to NASA's satisfaction. Upon departure, Wilmore and Williams will embark on a parachute-assisted landing at one of several designated sites in the southwestern United States, concluding their historic test flight.

While the delays introduce new challenges, they underscore the rigorous safety protocols governing human spaceflight. The successful resolution of these issues and the safe return of the crew are paramount as NASA and its commercial partners work to solidify a robust and reliable human presence in low-Earth orbit.