The Boeing CST-100 Starliner crew has received encouraging news regarding their return to Earth. Ground testing of the spacecraft’s thrusters, which have left it in orbit since early June, has concluded. Boeing and NASA had awaited the completion of these tests to start preparing for the spacecraft’s homeward journey.
An update late last week confirmed, “Ground testing of a Starliner Reaction Control System (RCS) thruster at the White Sands Test Facility in New Mexico is finished, and teams are now focusing on reviewing the data.” The main goal of the tests was to assess thruster performance degradation, which would help the team understand why some thrusters were deactivated during the flight and the potential effects of reactivating those thrusters on the overall mission.
The term “de-selected” refers to the thrusters that ceased functioning. The helium tanks that control these thrusters experienced leaks both prior to and during the Starliner launch, causing several delays. Despite having 70 hours’ worth of helium aboard, well above the necessary seven, officials noted last month that while the spacecraft could return immediately if necessary, they aren’t fully prepared for that outcome.
In their last report, NASA and Boeing mentioned a possible return flight at the end of this month. However, the timeline has since become less defined: “Boeing and NASA engineers will conduct thruster disassembly and inspections, and will continue to finalize flight rationale to support readiness reviews for Starliner’s planned return to Earth with commander Butch Wilmore and pilot Suni Williams in the upcoming weeks.”