The Boeing Starliner Calypso, which launched to the International Space Station on June 5 with two experienced astronauts on board, is about to undock from ISS after three months on orbit — but with those fliers staying behind on the Station for the next six months while the Crew Flight Test (CFT) mission ends without them on board.
The autonomous undocking happened on schedule Friday, Sept. 6 at 6:04 PM EDT (22:04 UTC). Landing was initially scheduled for later that same day at 10:04 PM MDT (04:04 UTC Saturday, Sept. 7) at White Sands in New Mexico. This was the third uncrewed landing of Starliner at that site, and the fourth landing of a crew-capable vehicle there.
The White Sands Missile Range (WSMR) complex, within a region of New Mexico known for gypsum sand dunes, was named as one of the landing sites for Starliner along with the Dugway Proving Ground in Utah and the Willcox Plain in southeast Arizona. Edwards Air Force Base in California has been named as a contingency site as well.
Space Shuttle Columbia landing at Northrup Strip — now White Sands Space Harbor — in March 1982 to close out the STS-3 test flight. (Credit: NASA)
There are two sites within WSMR available for Starliner’s landing. One of these sites — WSMR-N — is at the northern end of the range, and another — more southerly site — is the White Sands Space Harbor (WSSH) site where the Space Shuttle Columbia landed on what was then known as Northrup Strip to close out the STS-3 mission in March 1982.
WSSH has hosted all three landings of the Starliner spacecraft so far. Starliner Calypso landed at WSSH after the troubled Orbital Flight Test (OFT) mission in December 2019 and the second — not yet named — Starliner spacecraft landed there in May 2022 after OFT-2. All three landings were uncrewed and now the Starliner-1 mission would be the next opportunity for a crewed landing at the site.
On Thursday, Aug. 29, Part 2 of NASA’s agency readiness review took place. During the first part of this review, the agency decided to proceed with an uncrewed undocking of Starliner. In the second part, everyone polled “go” for undocking pending the vehicle’s operational status and landing weather.
Seven mission data loads have been updated, and the CFT software is being used “as is” otherwise. The software has been tested in a series of runs in Boeing’s avionics and software integration lab and it has checked out with good results.
CFT crewmembers Butch WIlmore and Suni Williams aboard ISS. (Credit: NASA)
The Starliner’s return to Earth started with the final hatch closure by CFT astronauts Butch Wilmore and Suni Williams, at 1:30 PM EDT (17:30 UTC) on Sept. 5. A readiness poll took place on that day, while the undocking poll took place approximately 45 minutes, with the result being “go”, before the scheduled departure on Sept. 6.
The winds and clouds at White Sands currently are looking favorable, with wind speeds of seven to 10 knots expected, though rain showers in the mountains are being watched. If an undocking had not been approved, there were opportunities every four days thereafter. The next opportunity to undock was on Tuesday, Sept. 10, while Sept. 14 and Sept. 18 were available if needed. The Sept. 22 opportunity could have conflicted with Soyuz operations but that is moot now.
Starliner Calypso is seen docked to the Harmony module’s forward port from a window on the SpaceX Dragon Endeavour spacecraft docked to the zenith port on the Harmony module on ISS. (Credit: NASA)
The undocking procedure that will be used was different from the procedure that the CFT crew would have used if they were on board. After the spacecraft was released from the forward docking port on the Station’s Harmony module, it did not conduct a flyaround as had been planned with the crewed undocking. 12 hooks were retracted from the docking port and springs pushed Calypso away from the Station.
A “breakout burn”, with 12 separate thruster firings, pushed Calypso away from the Station quickly. This burn was performed around 90 seconds after undocking; during a crewed undocking, the spacecraft would have been staying closer to the Station for a longer time. This procedure was meant to place less stress on the thrusters due to the need for fewer burns.
Starliner Calypso departing ISS without its crew on Sept. 6, 2024. (Credit: NASA TV)
The “breakout burn” took five minutes to complete. Four minutes after undocking, Calypso left the imaginary “keep out sphere” 200 meters around ISS. The next milestone was successfully accomplished 10 minutes after the breakout burn when Starliner crossed the approach ellipsoid, where spacecraft are supposed to be able to stay away from ISS for 24 hours even if all maneuvering capability were lost.
After departure from the Station, there were additional tests performed on the thrusters to check their performance after three months on orbit. During one of those tests – this one on the crew module – one of 12 thrusters failed; there is redundancy in the system. These tests were done to gather additional data to assist NASA and Boeing in their diagnostics and resolution of the propulsion system’s issues that prevented a crewed return.
Diagram showing the Starliner’s key components. (Credit: Boeing)
A few hours after Calypso leaves ISS, the spacecraft conducted its deorbit burn over the Pacific Ocean. The deorbit burn, lasting approximately one minute, took place at 11:17 PM EDT on Sept. 6 (03:17 UTC Sept. 7), and the burn successfully placed Calypso on a trajectory to land in New Mexico. It was expected that all thrusters would be functional except for the B1A3 thruster in the bottom “doghouse” on Starliner’s service module.
I estimate Starliner orbit is now about -20 x 418 km
— Jonathan McDowell (@planet4589) September 7, 2024
The service module was jettisoned after the deorbit burn and made a destructive reentry over the Pacific. Since the service module was expended, the propulsion system cannot be inspected upon return to Earth. NASA and Boeing have conducted additional on-orbit testing of the propulsion system to gather data on its performance as a result.
Starliner Calypso reached a temperature of up to 1,930 degrees Celsius during re-entry and communication was briefly lost due to ionized air surrounding the spacecraft. The spacecraft flew on a path that took it over the Pacific, then over Baja California and other parts of western Mexico, and finally United States airspace over New Mexico.
Illustration of Starliner’s landing sequence. (Credit: Boeing)
Landing was set for WSSH, which has hosted all other crew-capable spacecraft landings at WSMR. When Calypso reached the vicinity of White Sands, the forward heat shield was jettisoned to expose the parachute compartment four minutes before touchdown. Two drogue chutes deployed afterward, followed by the deployment of a pilot chute and three main chutes.
Starliner Calypso on three main chutes before landing at White Sands, New Mexico to conclude the CFT mission. (Credit: NASA TV)
A rotation handle was deployed to align the spacecraft for landing at approximately two minutes and 49 seconds before touchdown. The large base heat shield was jettisoned afterward to expose the airbags, which were deployed at an altitude of around one kilometer before the nighttime touchdown. Starliner Calypso successfully touched down on those airbags at 10:01 PM MDT on Sept. 6 (04:01 UTC Sept. 7).
After Starliner’s landing, cargo that was loaded aboard the spacecraft by the CFT crew for the return home will be unloaded and the spacecraft will be safed. The spacecraft will be inspected and returned to Boeing for reuse on a future flight, while the company and NASA examine telemetry from the expended service module and its propulsion system.
Starliner under its parachutes for the OFT-2 landing in 2022. (Credit: NASA)
After Starliner’s return to Earth, further crew changes are scheduled for this month. Soyuz MS-26 is set to fly on Wednesday, Sept. 11 at 16:23 UTC with Alexey Ovchinin and Ivan Vagner from Roscosmos as well as NASA’s Don Pettit. After MS-26 arrives at the Station, a crew handover will take place with Oleg Kononenko, Nikolai Chub, and Tracy Caldwell-Dyson returning to Earth on Soyuz MS-25.
Soyuz MS-25’s return to Earth is planned for Sept. 24, which is also the current launch date for the revised Crew-9 mission. Crew-9, using Crew Dragon Freedom, will fly with commander Nick Hague and mission specialist Aleksandr Gorbunov of Roscosmos. This will mark the first flight of a Crew Dragon with two crewmembers since the Demo-2 mission in May 2020.
Former Crew-9 members Zena Cardman — who had been the mission commander — and Stephanie Wilson would presumably be available for future ISS rotations. Hague and Gorbunov will perform a regular ISS rotation along with the CFT astronauts, and Crew Dragon Freedom will be the spacecraft Hague, Gorbunov, Butch Wilmore, and Suni Williams use for contingencies and their scheduled return to Earth.
Current Crew-9 members from left to right: Nick Hague of NASA and Aleksandr Gorbunov. (Credit: NASA)
Before Crew-9’s arrival, Crew Dragon Endeavour has been set up to return the CFT astronauts along with the nominal Crew-8 members in the event of any contingency requiring the evacuation of ISS. After the handover between Crew-8 and Crew-9, Crew-8 is scheduled to return to Earth sometime this month.
Prior to the CFT mission, the first operational flight of Starliner — Starliner-1 — had been scheduled for February 2025. That slot has now been taken by a Crew Dragon flight, Crew-10. When Starliner flies again depends on what remediation actions are required for the propulsion system, as well as any other actions required to validate the spacecraft’s safety for operational flights.
(Lead image: The American flag seen through Starliner Calypso’s cockpit window during the CFT mission. Credit: NASA)