Two American astronauts, sent into space for an eight-day mission by a Boeing Starliner, have been stuck for months on the International Space Station (ISS), as their craft was deemed too risky to safely make the return trip home.

On June 7, 2024, Boeing, in conjunction with the National Aeronautics and Space Administration (NASA), launched the two American astronauts, Barry “Butch” Wilmore and Sunni Williams, into space aboard Boeing’s ‘Starliner’ capsule. The mission: an eight day test of systems aboard Starliner, but this not-exactly-successful mission has turned into an eight-month detour around the planet for the pair.

For the past four months, the astronauts have been making their home aboard the ISS (along with seven other astronauts), while solutions to get the pair safely home have been in flux. However, on Sept. 29, their rescuers (SpaceX’s Crew-9), arrived to ferry them back home – but not until the end date of the SpaceX mission – in February 2025; turning their eight-day mission into an unexpected eight-month ordeal. 

Usually with an occupancy of four people, SpaceX’s Crew-9 only sent up two astronauts in their capsule, leaving room for Wilmore and Williams to hitchhike a ride back home with them when they depart in February. 

The true tale of how we got to this astronauts-stranded-in-space situation is as complicated as, well, space-travel:

Starliner, a spacecraft designed by Boeing for long-term missions to and from the International Space Station (ISS), originally had this mission targeted for 2017, but among helium leaks, thruster failures, computer issues, valve replacements, the project ran, on average, three years behind their targets – and now has left two astronauts stuck in space. 

Wilmore has been with NASA since 2000 following a Navy pilot career. Starliner was to be his third mission to space. 

Williams, commissioned to join the Navy for engineering, has been on numerous flights into space, once holding the record for most spacewalks total (seven) and most spacewalk time for a woman. She is no stranger to the ISS. 

The two had months of training leading up to the launch of Starliner, marking the first crewed flight aboard Boeing’s CST-100 Starliner. Wilmore, acting as commander, and Williams, acting as pilot, the capsule rode along the Atlas V rocket, designed by the United Launch Alliance. 

The Starliner and Atlas V rocket had two prior trips to space together before the agencies deemed it safe enough for human travel. Although Starliner had an original target operational date of 2017, the first uncrewed test flight did not take place until December 2019. 

Test flights are used to test various systems, software and hardware, on the capsule, the different modules it comprises, and the rockets. The performance of all these aspects are intently observed by both astronauts at the ISS and ground control facilities. Most notably, Mission Control at the Johnson Space Center (JSC) in Houston, Texas. 

On the morning of Dec. 20, 2019, Atlas V launched CST-100 Starliner into its first Orbital Flight Test (OFT-1). The capsule orbited the planet for two days. 

“Mission control teams in Houston have been pursuing two primary objectives: to maintain spacecraft integrity and orbital trajectory for two landing opportunities,” Starliner Updates released the morning of Dec. 21. 

By the end of the next day, Starliner had successfully come back down to Earth, landing in White Sands Harbor, N.M. OFT-1 was all-in-all widely successful. The recovered spacecraft was transported to Kennedy Space Center (KSC) in Cape Canaveral, Fla.

With the first test flight off without a hitch, Boeing started looking towards the future. The goal: to earn Starliner’s certification from NASA for long-term missions bringing cargo, personnel, and supplies to and from the ISS. NASA supplied Boeing with $4.2 billion in 2014 to make this capsule as part of NASA’s Commercial Crew Missions. 

The deal with NASA was in part of a race between Boeing’s Starliner and Elon Musk’s SpaceX Space Dragon capsule. SpaceX received $2.6 billion from NASA to create their rocket, which launched mid-September 2024 and arrived at the ISS days later. 

Over the last decade, Boeing has exceeded their $4.2 billion budget by an additional $1.6 billion. Much of it would be due to the delays that took place following OFT-1. 

Boeing committed to a second, uncrewed flight test (OFT-2) in the spring of 2020. Many logistical delays continued through the pandemic of that year. NASA and Boeing continued their reviews of OFT-1 and inspected the Starliner capsule. Come December 2020, Boeing released their target launch date of March 29, 2021. 

Throughout the spring of 2021, Starliner made it to the launch pad multiple times atop its Atlas V rocket, yet for some reason or another it was moved to wait at a seaside launch pad or for further testing in production facilities at KSC.

The summer came, and on Aug. 3, 2021, Starliner had received the official ‘go-ahead’ from NASA. Starliner made it to the launch pad, but several issues arose, causing NASA and Boeing to scrub the OFT-2 launch window. 

“NASA continues to work side-by-side with Boeing to understand the CST-100 Starliner’s service module valve performance, including the unexpected indications some of the valves were in the closed position during its August 3 launch attempt of [OFT-2],” Patti Bieling wrote for NASA on Aug. 6, 2021. 

Back at the production facility Starliner went for further, deeper trouble shooting into the valves and propulsion systems. Months passed, and the company started to look for other solutions, landing on discarding the issued service module entirely.

Boeing ultimately decided to scrap the current service module. The company moved up its production (through deadlines and discards), and used the service module they originally designed for the Crewed Flight Test (CFT), for OFT-2. The next service module, meant for Starliner-1, its planned first post-certification mission, would now go to the CFT. 

Now the build up to OFT-2 really begins. 

In launching, there are certain launch windows that are blocked out for missions. With March 2022 good and gone, Starliner OFT-2 targeted for May 19, 2022. In the days leading up, Starliner was rolled to the launchpad as its Atlas V fuelled up. 

OFT-2 finally launched successfully that evening, lifting off at 6:54 p.m. This flight, instead of orbiting for a time and landing back on Earth, NASA and Boeing wanted to test Starliner’s docking systems. So on May 20, Starliner docked at the ISS for the first time at 250 miles above Earth. 

“The docking showed that the spacecraft can effectively execute a rendezvous and docking with the ISS. Starliner will be able to complete this action repeatedly as it takes crews to the orbiting laboratory in the future,” Mission update came out May 20, 2022

While docked, the hatch was opened while crew aboard the ISS floated in and out for closeout work and routine inspections before sending the capsule back to Earth.

Starliner landed successfully, for the second time, in White Sands Harbor, N.M., completing OFT-2.

At this point, Wilmore and Williams are all in. They’ve been run through exercises, tests, simulations, to test their suits, the pressurized crew module, all the way to the seat fittings and cabin temperature.

“Overall, the training activities gave the astronauts and support teams confidence in operations that built their knowledge base for subsequent flight preparation activities,” Starliner Updates wrote on Dec. 14, 2022

The companies started looking towards the summer of 2023 for their CFT amid verification tests and busy flight schedules ahead for NASA.

On June 1, 2023, mission updates wrote about an issue in the parachutes, which are necessary for safe landing of the vessel. They received word of the issue from the supplier, and sent it to the engineering teams for additional analysis. It was then Boeing decided to withdraw from the summer launch target.

The next update came in October 2023 from NASA. Starliner remained at Boeing’s production facility as KCS as new parachutes were installed, thermal control systems were modified, and tape was replaced. Wilmore and Williams continued their simulations, running through every possible scenario to ensure preparedness. 

On April 25, 2024 NASA gave its approval for Starliner’s CFT. The capsule was moved to Launch position on May 4 atop its Atlas V rocket. On May 6, Wimore and Willaims were en route to the launch pad, prepped for being loaded into the capsule to conduct final closeout procedures. 

About three hours from launch, the two astronauts were loaded into the capsule. 

But just as the first crewed flight braced themselves, the entire thing was scrubbed. The launch plans dissolved as another valve issue arose. 

“NASA, Boeing, and [ULA] scrubbed the launch opportunity on Monday, May 6 for the agency’s Boeing [CFT] to the [ISS] due to a faulty oxygen relief valve observation on the [ULA] Atlas V rocket Centaur second stage,” wrote Elyna Niles-Carnes, NASA, May 6, 2024. 

Another cat-and-mouse game ensued throughout the month of May, with analyses, tests, and modifications in an attempt to make it to the next launch window. Helium leaks were also discovered as the astronauts were returned to Houston to quarantine, practice simulations, and prepare for next launch opportunities.

NASA gave the ‘go ahead’ on May 29, a day after the return of the astronauts to KSC, so flight crews began preparation for an early July launch. 

This launch was historic in a few ways: “Williams is the first female astronaut to fly on the first flight of a crewed spacecraft. It also marks the first crewed launch on the ULA Atlas V rocket, and the first crewed launch on an Atlas-family class rocket since… May 1963.” (Niles-Carnes, NASA).

Minutes before liftoff, the crew access arm, a large cat-walk type structure, retracted from the capsule and rocket, back into the crew access tower. The rocket becomes detached from everything for a safe departure. 

And the launch was…scrubbed again. This time, “due to the computer ground launch sequencer not loading into the correct operational configuration after proceeding into terminal count.” 

People had gathered on the green, anticipating watching a rocket send two humans into space. With minutes on the counter and cameras already rolling, the anticipation soured to confusion, disappointment, and a little bit of fear. 

The astronauts were once again removed from the crew module, to be quarantined at KSC. The launch was delayed another four days. Day and night technicians and engineers inspected every piece of the support launchpad equipment. 

“The ULA team identified an issue with a single ground power supply within one of the three redundant chassis that provides power to a subset of computer cards controlling various system functions…The chassis containing the fault ground power unit was removed, visually inspected, and replaced,” according to Danielle Sempsrott.

Everything functioned normally following the replacement and NASA gave the Boeing Flight Test Crew the ‘go ahead’ for the June 5 launch date. 

For the third time, the two astronauts arrived at the launch pad, cool and confident. The days spent waiting for technical difficulties allow them to undergo additional simulation training, pressure tests, and prepare themselves for the eight day journey.

The hatch was (once again) closed. The arm retracted (yet again). The air and Earth rumbled as Atlas V ignited, propelling the rocket in a successful lift off as the first crewed launch of Starliner.

After a 25.5 hour long journey into the atmosphere, the Starliner successfully docked at the ISS, delivering the astronauts to their destination. Early the next afternoon, Starliner successfully docked at the ISS, and the crew greeted each other warmly. 

Upon docking, however, several problems arose. More helium leaks were noticed, and although it was assured the rate of leakage would not affect the return trip (as Starliner has ample supply of Helium), ground teams and astronauts aboard the ISS worked tirelessly to ensure Wilmore and Williams could return home on the planned return date of June 22. 

But Starliner, ever so not punctual, pushed the date back further than a month. The crutch of the delay is what NASA called a “hot fire test.” Starliner, while attached to ISS, will fire a number of its thrusters, to observe and gain data on the performance of each thruster.

By the end of the month, the root issue was pulled up and configured. Mission Control Center in Houston began simulations on undocking and landing for Starliner on July 31. As more analyses took place, teams prepared for the potential return of Wilmore and Williams aboard Starliner. 

But it wasn’t to be. 

“The uncertainty and lack of expert concurrence does not meet the agency’s safety and performance requirements for human spaceflights, thus prompting NASA leadership to move the astronauts to Crew-9,” wrote Jessica Taveau with NASA.

So that was it. Starliner headed back to Earth Sept. 6 unmanned, landing once again in White Sands Harbor NM the following day, but leaving its two-person crew to get a different ride back to Earth..

Wilmore and Williams were moved to be part of the Crew-9 team aboard Elon Musk’s SpaceX Crew Dragon Capsule. SpaceX’s Crew-9, a group of four astronauts sent with the capsule, are set to remain at the ISS until early 2025. 

Now their recent competitors are their saviors in space. Wilmore and Williams are expected to join Crew-9 on the return mission to Earth, targeted for next February, after the failure of Starliner.

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Starliner Updates the website Boeing uses to relay its Starliner mission updates, and where most of the facts are pulled from for this article. 

NASA.gov provides updates on all planned space missions and crafts in rotation today.