NASA and Boeing engineers have completed a hot-fire test of the jet engines of the Starliner spacecraft’s reaction control system with astronauts Butch Wilmore and Suni Williams on board.

The test evaluated 27 of the spacecraft’s 28 jet engines, testing engine performance and helium leak rates, and yielded positive preliminary results.

Starliner spacecraft tests overview

On July 27, teams of NASA and Boeing engineers completed a jet engine test of the Starliner spacecraft’s hot fire response control system to evaluate the spacecraft’s propulsion system. NASA astronauts Butch Wilmore and Suni Williams, assigned to the agency’s Boeing Crew Flight Test, sit inside a docked spacecraft during a test in preparation for Starliner re-entry from the International Space Station.

The test involved firing 27 of the spacecraft’s 28 jets in short bursts to test the engine’s performance and helium leak rate. Preliminary results show that all engines tested returned to pre-flight levels, depending on thrust and chamber pressure.

Helium manifolds and engine performance

As part of the test configuration, all helium manifolds that control and direct helium flow were opened, allowing engineers to continue to evaluate Starliner’s helium supply and leak rate. Teams testing Starliner continue to demonstrate the margin needed to support the return trip from the station. Following the test, the helium manifolds were closed and will remain closed until Starliner activates its propulsion system prior to docking. Teams will also test the helium leak rate prior to Starliner’s removal.

Teams are reviewing data from hot-fire tests and final ground tests of the Starliner engine at NASA’s White Sands Test Center in New Mexico before testing the agency’s readiness for reentry. Following this agency-level analysis, NASA and Boeing will select a target return date.

Current activities of astronauts

As ground crews work to complete Starliner’s return to Earth, Wilmore and Williams continue to assist with scientific research and maintenance with the Expedition 71 crew. On July 29, Willmore and Williams boarded their spacecraft and tested water systems, called Boeing mission personnel into a conference call, and donned space suits to perform a pressure test. Wilmore began his morning assembling the BioServe centrifuge in the Harmony module, while Williams reviewed procedures for operating the free-flying auxiliary robots Astrobee.