NASA Boeing Starliner Is Too Risky for Return Mission, SpaceX Dragon To Rescue Astronauts!

Boeing's Starliner spacecraft is preparing for an in-orbit "hot fire" test of its thruster system at the International Space Station (ISS), scheduled for either Saturday, July 27, or Sunday, July 28. This test is crucial as NASA and Boeing continue to investigate thruster failures and a helium leak that occurred during its current mission, known as the Crew Flight Test (CFT).
The test will involve the spacecraft's 28-thruster reaction control system (RCS), though only 27 of these thrusters will be used due to one being deemed unusable for the return journey. Commands for the test will be sent from the ground, but NASA astronauts Butch Wilmore and Suni Williams, currently aboard the ISS, are likely to participate due to their interest and expertise as former U.S. Navy test pilots.
Steve Stich, manager of NASA's Commercial Crew Program, explained that the purpose of the test is to ensure the thruster system operates as expected before undocking. This includes verifying the helium system, which hasn't been checked since June 15. Engineers will pressurize the manifold and hot-fire the thrusters, examining helium leak rates to ensure system stability.
Initially, the CFT mission was planned to last about ten days following its launch on June 5. However, due to thruster issues and helium leaks, the mission has been extended indefinitely while engineers troubleshoot these problems. The spacecraft docked safely with the ISS despite these challenges.
Ground tests conducted at the White Sands Test Facility in early July provided more insight into the issues faced during docking. For instance, an Aerojet Rocketdyne test thruster, similar to those on Starliner and stored for three years before recent tests, showed severe valve system degradation due to nitrogen dioxide vapor. Propellant flow was restricted by a bulging seal, and Teflon erosion caused by high-temperature bubbling was found in a downstream filter.
Stich noted that the thruster behavior observed in orbit aligns with the issues seen during ground tests. Although the RCS thruster type has a heritage from other Aerojet spaceflight programs, modifications for Starliner's service module might have contributed to the problems. The thrusters are housed within protective "doghouses" that insulate them from the cold temperatures of space. During CFT, frequent RCS thruster pulses, combined with firings from the orbital maneuvering and attitude control system (OMAC), caused higher-than-expected temperature increases in the thrusters.




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