The eventful Starliner Crew Flight Test (CFT) mission crewed by astronauts Butch Wilmore and Suni Williams has reached a point where a decision has now been made to return the astronauts home on Crew Dragon Freedom. This comes after the CFT mission stretched from the initial “soft” planning for eight days to spending two and a half months aboard the International Space Station, and the CFT crew will now stay in orbit for eight months.
The Boeing Starliner, Calypso, launched successfully into orbit atop an Atlas V N22 from Cape Canaveral Space Force Station (CCSFS) on June 6, 2024. However, during the first hours of the flight, helium leaks were noticed in the propulsion system. Eventually, five leaks were discovered, but the leak rate was slow enough that the mission could proceed to rendezvous and docking operations.
Starliner Calypso approaching the ISS before docking on June 6, 2024. (Credit: NASA)
However, during rendezvous with the International Space Station (ISS), five thrusters failed; a serious degradation in thrust was noticed from these thrusters, and controllers needed to try to get them back online. Four of these thrusters were returned to service and Calypso successfully docked with ISS.
The thruster failures and helium leaks continued to receive scrutiny from mission controllers while the CFT astronauts were greeted by the Expedition 71 crew. While the nine crew members from both missions combined and performed typical science and housekeeping duties, the mission was extended multiple times.
A Starliner thruster being tested at White Sands. (Credit: NASA)
By the end of June, it was realized that more testing would be needed before teams would feel comfortable proceeding with a crewed return of Starliner to a touchdown on land in the western United States. Boeing and NASA conducted tests at White Sands, New Mexico with a Starliner service module that had spent the last three years in a fueled state.
These tests showed clear thruster degradation similar to that found on orbit, thought to be caused by an issue with bulging seals in an oxidizer valve, restricting the flow of propellant to the thrusters. While Boeing and NASA worked to find the root cause of the degradation, NASA quietly worked on contingency plans to bring the CFT crew home on a Crew Dragon if necessary.
Contingency plans are routinely made for the Space Station and its visiting vehicles, and one was also made for Tracy Dyson if there were issues with the Soyuz she flew to the Station.
The combined crews of Expedition 71 and Starliner CFT pose aboard ISS. (Credit: NASA)
After CFT’s June 6 launch, the spacecraft was initially rated for a 45-day stay at the Station, docked to the Harmony node module’s forward port, but that would be extended. Mid-August was defined as a cutoff point if necessary, and as July turned into August there was still no consensus on bringing Calypso home with its crew. The spacecraft’s stay was extended to allow for additional testing and analysis of the propulsion system.
The Starliner was cleared to act as the CFT crew’s emergency return vehicle if an emergency were to happen aboard the Station that required an immediate evacuation. However, much discussion remained as to whether the CFT astronauts would be cleared for a nominal return on Calypso. The main concerns regarding the thrusters are how well they would perform during the departure from ISS and during the de-orbit burn to bring the crew back to Earth.
Starliner Calypso is seen docked to the Harmony module’s forward port from a window on the SpaceX Crew Dragon Endeavour. (Credit: NASA)
On Wednesday, Aug. 14, NASA held a teleconference in which former Shuttle and ISS astronaut and current associate administrator for the agency’s Space Operations Mission Directorate Ken Bowersox stated there would be a flight readiness review meeting no earlier than the end of the following week. Engineers were continuing a data analysis of the propulsion system which needed to be finished before that meeting.
The options for the CFT crew’s return home were to perform a nominal return aboard Starliner or to stay aboard the Station while Calypso returned without crew. Since the latter option was chosen, Crew-9 will launch with two astronauts, and the CFT crewmembers will stay an additional six months aboard the Station as Expedition 71/72 crewmembers.
The Crew-9 launch was moved to late September and to SLC-40 at Cape Canaveral Space Force Station (CCSFS) to accommodate planning for this option, while also allowing the Polaris Dawn mission to proceed in late August. Polaris Dawn is to launch no earlier than Aug. 27 using the Crew Dragon Resilience, and it will not fly to ISS.
As the second option was chosen, Butch Wilmore and Suni Williams will return aboard Crew-9 in late February 2025, after eight months in orbit. They will be wearing SpaceX launch and entry suits for their trip home, and Crew Dragon Freedom will be Butch and Suni’s “safe haven” spacecraft as well.
Crew Dragon Endeavour with the Milky Way in the background. (Credit: NASA)
Starliner Calypso currently occupies the docking port that Crew-9 will need to use, and once it undocks there will only be the Crew Dragon Endeavour at the US segment of ISS before Crew-9 arrives. In the unlikely event of a contingency where the crew — including the CFT astronauts — have to depart the ISS quickly after Calypso’s undocking but before Freedom’s arrival, Butch and Suni will fly aboard Endeavour without suits and on a foam-cushioned cargo pallet in the compartment below the crew seats.
The configuration work to allow for a contingency return of six astronauts aboard the Crew-8 spacecraft will be completed before Starliner undocks. Starliner will use a simplified undocking procedure now that it will come home without crew.
Prior to the decision on how and when to send the CFT astronauts home, NASA held two reviews — a program control board review and part one of an agency flight readiness review. Part two of the flight readiness review will be held later to discuss Starliner’s return. The final decision from this review was announced on Saturday, Aug. 24 during a NASA press conference.
The original crew portrait for Crew-9 before the change in plans caused by returning CFT without crew. (Credit: NASA)
The agency-level flight readiness review was chaired by Ken Bowersox. NASA Administrator Bill Nelson, who has also flown aboard the Shuttle, made the final decision. NASA’s deputy administrator, associate administrator, agency center directors, the Flight Operations Directorate, and NASA technical authorities are also typically involved in agency-level reviews.
The decision was to send Starliner Calypso home without crew and to have Butch Wilmore and Suni Williams stay aboard the ISS for six more months. This decision was made due to remaining uncertainty in the performance of the thrusters as well as the physics involved during the thruster failures.
The polling was unanimous with the NASA people regarding the decision, and Boeing said they would be ready to work with either option. The CFT crewmembers will come home on Crew-9’s spacecraft toward the end of February 2025, joined by two Crew-9 members. The crew assignment will be publicized when it is finished.
Starliner Calypso after returning to Earth following the OFT mission. (Credit: NASA/Bill Ingalls)
NASA Administrator Bill Nelson emphasized safety when announcing the decision to return Starliner home uncrewed. As he stated during the press conference “spaceflight is risky, even at its safest and most routine. A test flight, by nature, is neither safe nor routine. Our decision to keep Butch and Suni aboard the Space Station and bring Starliner home uncrewed is the result of our commitment to safety: our core value and our North Star.” NASA commercial crew program manager Steve Stich summarized that a return on Starliner was “just too much risk for the crew.”
Starliner Calypso will land in the western United States — at White Sands Space Harbor — sometime in early September. The spacecraft is likely able to come home safely, but NASA did not want to take additional undue risk given the issues the propulsion system had before Calypso’s docking. Crew-9 will launch no earlier than Sept. 24 with two crewmembers rather than the usual four, with the CFT crew joining them on their six-month increment.
(Lead image: Starliner Calypso docked to the forward port on the Harmony node on ISS. Credit: NASA)
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