WASHINGTON – Boeing’s CST-100 Starliner will return from the International Space Station in September without the two astronauts aboard who launched on the plane in June after NASA concluded that problems with the engines posed too great a risk.
NASA announced on August 24 that Butch Wilmore and Suni Williams, the NASA astronauts who flew to the ISS in June as part of the Starliner’s Crew Flight Test (CFT) mission, will remain on the station until next February, with the Starliner returning uncrewed to Earth in early September.
Agency officials said at a briefing that they made the decision after concluding they did not understand well enough the performance of the reaction control system engines that failed during the Starliner’s approach to the station in June. NASA and Boeing have been working since then to determine the cause of the engine’s power loss to see if it would reoccur when the Starliner undocks and returns to Earth.
However, they said they had not been able to resolve all of the uncertainties about the engines to their satisfaction. “This uncertainty remains in our understanding of the physics of what is happening in the engines,” said Jim Free, NASA’s deputy administrator.
Testing of the engines at NASA’s White Sands Test Facility in New Mexico was able to reproduce the loss of engine power, finding that a Teflon seal had heated up and expanded, restricting the flow of oxidizer to the engine. But officials said they did not know enough about how this happened to be certain that there would be no problems during the time-critical firings when Starliner departs the station and during the deorbit firing.
“There were just too many uncertainties in predicting the engines,” said Steve Stich, NASA’s commercial crew program manager. “The risk to the crew was just too great, and that’s why we decided to conduct the unmanned test flight.”
“One of the really important factors to me is that we simply don’t know how many times we can use the engines on the way back before we run into a problem,” said Ken Bowersox, NASA’s deputy administrator for space operations.
Both Bowersox and Stich called the decision to bring Starliner back unmanned a very obvious one. Bowersox noted that it was only in the last week that he realized it was not feasible to bring Wilmore and Williams back with Starliner. “With more time, we might have gotten a lot smarter, but we’re at the point where we need to bring Starliner home,” he said.
Bowersox added that the decision to pursue an unmanned return was unanimous among NASA officials. Boeing, he said, is willing to support both an unmanned and manned return. “They believe in their vehicle and would be willing to bring a crew home with it.”
NASA Administrator Bill Nelson said at the press conference that there was no political influence on the decision, although there was speculation about whether the office of Vice President Kamala Harris, the Democratic presidential candidate and chair of the National Space Council, might have played a role. “I can tell you unequivocally from a personal perspective that politics played no role in this decision,” he said. “It has absolutely nothing to do with it.”
The road ahead
NASA now plans to proceed with an alternate strategy it outlined earlier this month. Starliner will undock from the station without a crew and return to Earth to land at White Sands or another location in the southwestern United States. Crew-9 will launch no earlier than Sept. 24 with two of the originally assigned four people on board, freeing up spots for Williams and Wilmore. That Crew Dragon spacecraft will return as planned in February 2024.
At the briefing, NASA did not disclose which of the four Crew-9 members currently assigned to the mission – NASA astronauts Zena Cardman, Nick Hague and Stephanie Wilson and Roscosmos cosmonaut Alexsandr Gorbunov – would remain on assignment. “We are working to finalize those crew assignments and update the training plan,” said Norm Knight, director of NASA’s Flight Operations Directorate. “Those decisions will be released as soon as they are finalized.”
Both he and Dana Weigel, NASA’s program manager for the ISS, said Wilmore and Williams are prepared for a much longer stay on the station. Both have flown long-duration missions to the ISS before and received refresher training on ISS operations as part of contingency planning for a scenario like this one in which their stay would need to be extended.
“They have integrated seamlessly into the Expedition 71 crew,” Knight said, referring to the long-term crew currently on the station, “and are contributing to the important work aboard the International Space Station.”
The Starliner’s departure will also be modified, Stich said. “We’ll modify the separation sequence a little bit to get away from the space station a little faster,” he said. There will also be changes in the spacecraft’s software configurations to allow docking without astronauts on board to monitor operations and make changes. NASA has not announced a specific date for the Starliner’s return, other than sometime in early September.
The future of the Starliner
When Starliner will fly again is still uncertain. Officials said they will wait until Starliner completes its uncrewed return to evaluate what changes to the spacecraft are needed and how they will be made. That includes whether another crewed test flight will be needed before NASA certifies the spacecraft for ISS crew rotation missions.
“We haven’t made a final decision about what our goals are or what we have achieved,” Stich said. “I don’t think we have decided yet on another manned flight test.”
“I wouldn’t rule anything out,” Bowersox added. “We have some options as to how we proceed.”
There has been speculation that Boeing, which has already posted $1.6 billion in losses on Starliner, including $125 million disclosed in July, might walk away from the fixed-price contract rather than incur further losses. Nelson said Boeing’s new chief executive, Kelly Ortberg, has assured him the company will continue with the Starliner program.
“He expressed to me his intention that they will continue to work on the issues once Starliner is safely back,” Nelson said. “We will have redundant access for our crew to the space station.” Later in the call, however, he said he did not ask Ortberg whether the company was willing to cover costs such as an additional test flight, “nor would it have been appropriate” to discuss it in that conversation.
No Boeing representatives were present at the meeting. Bowersox said that because the meeting was about a NASA decision, the agency felt it was appropriate for only its representatives to speak to the media about its decision.
“Boeing remains primarily focused on crew and spacecraft safety,” the company said in a brief statement. “We are executing the mission as defined by NASA and preparing the spacecraft for a safe and successful unmanned return.”
Nelson said he expects the Starliner to fly again with astronauts on board. When asked how sure he was of that, he simply replied: “100%.”
From eight days to eight months
Wilmore and Williams launched on Starliner on June 5 after numerous delays and docked with the station the following day. At the time of the mission launch, NASA expected Starliner to stay at the ISS for only eight days. At a post-launch press conference, it even announced specific undocking and landing times for the spacecraft’s return on June 14.
However, the Starliner’s engine problems during its approach to the station and the discovery of several other helium leaks prompted NASA to extend the spacecraft’s stay, initially by days and later by weeks.
In late June, NASA delayed Starliner’s return until at least the second half of July to conduct ground tests of Starliner’s engines to replicate the problems encountered during its approach to the station. However, in late July, NASA delayed Starliner’s departure until mid-August while it continued engine studies, including testing the engines on the spacecraft itself while docked to the ISS.
As of late July, there was no public indication that NASA was considering alternatives to Williams and Wilmore returning on the Starliner. “I’m very confident that we have a good vehicle to bring the crew back,” said Mark Nappi, Boeing vice president and commercial crew program manager, at a July 25 briefing.
Less than two weeks later, however, NASA officials admitted they were now considering scenarios in which the two astronauts instead remained on the ISS while Starliner returned uncrewed. In that scenario, Williams and Wilmore would remain on the ISS until February 2025 and return on the Crew Dragon-9 spacecraft, whose launch NASA had postponed from August 18 to September 24.
At NASA’s last Starliner briefing on Aug. 14, the agency said it needed to make a decision about Starliner by the last week of August to plan the spacecraft’s departure with or without astronauts on board and to accommodate the launch of Crew-9 and the return of Crew-8. At that briefing, officials said they were still working to model and understand the behavior of the engines, and there was no consensus on whether it would be safe for Wilmore and Williams to return with Starliner.
NASA’s decision to allow the Starliner to return unmanned extends Wilmore and Williams’ stay on the ISS from eight days to over eight months.
“All the astronauts on the station are professionals,” Knight said. Wilmore and Williams were informed of the decision to bring Starliner back without them and supported it, he explained. “It’s disappointing that they’re not coming home with Starliner, but that’s OK. It’s a test flight. That’s their job and they know the risks that come with it.”
“We keep them very busy on the ISS,” he added. “They are part of the crew and they are doing well.”
