Exactly two months ago on August 6, 2024, Boeing’s Starliner spacecraft carried Indian-American astronaut Sunita Williams to the International Space Station. Sunita Williams, along with NASA astronaut Butch Wilmore, made history in June when they became the first members to travel to the ISS aboard the Starliner.
The spacecraft was launched on June 5 and arrived at the ISS on June 6. It was reportedly scheduled to return by June 14. However, the Starliner’s return to Earth has been delayed due to thruster anomalies and a helium leak in the spacecraft. NASA and Boeing have not yet set a return date.
It said officials in space and on Earth are continuing tests and studies to determine the root cause of the problems with Starliner and ensure the safe return of the two astronauts aboard the Boeing spacecraft.
“It was a test flight [NASA’s Boeing Crew Flight Test] “We were hoping to find some findings that could be used to improve the next flight,” Sunita Williams said on July 10.
“As always, the safety of the astronauts remains the top priority for both NASA and Boeing,” NASA said in its Aug. 1 statement.
This was Boeing’s second flight to the ISS and the third flight test of Starliner overall. But this crewed flight test was the first launch to the ISS with astronauts on a Boeing spacecraft and a United Launch Alliance Atlas V rocket as part of the agency’s Commercial Crew Program.
Is the Starliner healthy now?
Boeing said in a statement that the Starliner’s propulsion system has been extensively tested. The aerospace company ensured that the Starliner’s propulsion system “maintained redundancy and that helium levels remained stable”.
Boeing reported that the test “confirmed that 27 of the 28 RCS thrusters are healthy and returned to full operational capability”.
As officials take time to determine the root cause of the anomalies on the Starliner, Boeing said, “The data also supports the root cause assessment of the helium and thruster issues and the flight justification for the return of Starliner and its crew to Earth.”
NASA officials previously said the propulsion systems are highly redundant to one another. “So if there’s a problem with one of the thrusters, the redundancy will take over and get us home safely,” they said.
Starliner’s propulsion system is part of the spacecraft’s “service module.” The problems center on this system, which is needed to propel the Starliner capsule away from the ISS and dive into Earth’s atmosphere. Several of Starliner’s thrusters overheated when fired, and leaks of helium – which is used to pressurize the thrusters – appear to be linked to the frequency of their use.
Thrusters are needed to position the Starliner spacecraft for reentry and also to slow the capsule to the proper speed before the service module separates. Only after this phase does the capsule take off for the final time. Briefly, the mission was delayed because at least one of the 28 thrusters malfunctioned.
19 tests conducted
Boeing and NASA conducted 19 tests of the Starliner’s propulsion system. These included “approximately 100,000 computer model simulations representing potential variables and conditions that Starliner might experience during undocking, deorbit burns, and landing”.
Seven ground tests were conducted of the reaction control system (RCS) thrusters removed from the Starliner-1 service module. These included one “free-flight hot fire” test and two docked hot fire tests. In addition, helium leak rate data was also measured.
When a hot fire test of the Starliner spacecraft’s reaction control system jets was conducted on July 27, “the teams confirmed [that] Starliner continues to show the margin needed for the return trip from the station.”
NASA said on July 30 that ground teams were working to finalize Starliner’s return to Earth.
