Starliner approaches the International Space Station during a test flight in 2022. The orbiting laboratory was flying 430 kilometers (270 miles) above the South Pacific at the time of this photograph. Credit: NASA
When NASA astronauts Butch Wilmore and Suni Williams took off from Earth On June 5, aboard Boeing's Starliner spacecraft on its first crewed test flight to the International Space Station (ISS), they were expected to spend about a week in space. However, the two astronauts will now spend about eight months in orbit and return home on a different craft.
POT announced on Saturday that the uncrewed Starliner spacecraft will autonomously return to Earth early next month. Wilmore and Williams will have two seats at home aboard the soon-to-arrive SpaceX Dragon capsule with the Crew-9 astronauts, set to depart in February of next year.
“This was not an easy decision, but it was absolutely the right one,” NASA Associate Administrator Jim Free said during the press conference.
Problems with the propeller
The main concern remains Starliner's thrusters, which Problems experienced as the spacecraft prepared to dock with the ISS. Those thrusters are needed both to undock the spacecraft from the station and to perform the vital deorbit burn to put Starliner on a safe path home during its return trip.
NASA and Boeing teams have been working around the clock to test and collect data on the thrusters and model their behavior, hoping to better determine why they experienced problems and how they might behave once they are fired again to set the spacecraft on a trajectory back home.
But in the end, “there was too much uncertainty in the thruster prediction,” said Steve Stich, director of NASA’s Commercial Crew Program. “If we had a way to accurately predict what the thrusters would do during undocking and throughout the deorbit burn and separation sequence, I think we would have taken a different course of action. But when we looked at the data and looked at the potential for thruster failure with a crew on board … it was too much of a risk with the crew, so we decided to do the uncrewed test flight.”
Despite the uncertainties that led to the decision, “we have learned a lot about the spacecraft during its journey to the station and its docked operations. We will also continue to collect more data on Starliner during the uncrewed return and improve the system for future flights to the space station,” said Ken Bowersox, NASA associate administrator for space operations.
Stay in orbit
Far from overstaying their welcome, Williams and Wimore “have seamlessly become part of the Expedition 71 crew,” said Norm Knight, NASA’s Director of Flight Operations. They will remain part of that crew aboard the ISS and will return home at the scheduled end of the Crew-9 mission early next year.
That mission is scheduled to launch no later than Sept. 24. Because of the limited number of docking ports on the ISS that support commercial vehicles, Starliner must depart before Crew-9’s SpaceX Dragon capsule can lift off and head to the station. Additionally, Crew-9 will carry only two of the planned four crew members to accommodate the return of Williams and Wilmore.
Now that the crucial decision has been made, engineers are moving forward with developing and testing a simplified undocking procedure for the uncrewed Starliner. The readiness assessment is expected to be completed by the end of next week, according to Bowersox.
Before it can take off, the Crew 9 roster and manifest will also need to be updated; NASA has not yet announced which of the four planned crew members will head to the ISS and which will remain on Earth. According to Sitch, the Dragon capsule will need to include two different seats for Williams and Wilmore, as well as additional ballast during launch. NASA will send personal effects and SpaceX spacesuits for the two astronauts.
In the meantime, Sitch added, the Crew-8 vehicle currently on the station will serve as a lifeboat for Williams and Wilmore, should the situation arise.
'This is a test flight'
While eight months is clearly longer than Wilmore or Williams planned to spend aboard the ISS, it is within NASA's normal operating experience. The panel also noted that this is a test flight and that handling unexpected events is part of the core job of an astronaut and an engineer.
“Spaceflight is risky, even in its safest and most routine forms. A test flight, by its nature, is neither safe nor routine. The decision to keep Butch and Suni aboard the International Space Station and bring home Boeing’s uncrewed Starliner is a result of our commitment to safety. Our core value is safety, and it is our North Star,” said NASA Administrator Bill Nelson.
Ultimately, he added, NASA wants to understand the cause of the problems and how to make the best adjustments so that Starliner, in conjunction with SpaceX Dragon, can safely transport future crews to and from the ISS.
“Overall, Starliner has performed exceptionally well, so keep an eye on it. This is a test flight,” Knight said. “The thruster issue and associated investigations will have great benefits for future human exploration when Starliner flies again.”
