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Boeing Crew Flight Test
Spacecraft properties
Boeing Starliner Spacecraft 3 Calypso launches on the Crew Flight Test atop an Atlas V rocket
Names	Boe-CFT

Mission type	Flight test
Operator	Boeing Defense, Space & Security
Mission duration	Planned: 8 days Capsule Final: 93 days, 13 hours, 9 minutes Crew: 391 days, 11 hours


Spacecraft	Boeing Starliner Spacecraft 3 Calypso
Spacecraft type	Boeing Starliner
Manufacturer	Boeing Defense, Space & Security


Crew
Crew size	2
Launching	Barry E. Wilmore Sunita Williams
Landing	None


Start of mission
Launch date	5 June 2024, 14:52:15 (5 June 2024, 14:52:15) UTC (10:52:15 am EDT)
Rocket	Atlas V N22 (AV-085)
Launch site	Cape Canaveral, SLC‑41
Contractor	United Launch Alliance


End of mission
Landing date	7 September 2024, 04:01:35 UTC (12:01:35 am MDT)
Landing site	White Sands Missile Range


Orbital parameters
Reference system	Geocentric orbit
Regime	Low Earth orbit
Inclination	51.66°


Docking with ISS
Docking port	Harmony forward
Docking date	6 June 2024, 17:34 UTC
Undocking date	6 September 2024, 22:04 UTC
Time docked	92 days, 4 hours, 30 minutes

Boeing Crew Flight Test mission patch Williams (left) and Wilmore (right) Commercial Crew Development ← Boeing OFT‐2

The Boeing Crew Flight Test (Boe-CFT) was a very important space mission. It was the first time the Boeing Starliner spacecraft carried astronauts into space. On June 5, 2024, two NASA astronauts, Barry E. Wilmore and Sunita Williams, launched from Cape Canaveral Space Force Station. Their goal was to fly to the International Space Station (ISS).

The mission was supposed to last only eight days. But, the Starliner capsule had some problems with its small rocket engines (called thrusters) after it connected to the ISS. After a long investigation, NASA decided it was too risky for the astronauts to return on the Starliner. Instead, the Starliner came back to Earth without anyone on board on September 7, 2024. The astronauts will return later on a different spacecraft, the SpaceX Crew-9 Dragon.

This mission faced many delays. It was first planned for 2017. Before this crewed flight, the Starliner had two uncrewed test flights in 2019 and 2022.

The Starliner spacecraft was put on top of the Atlas V rocket on April 16, 2024. But the launch was delayed several times due to technical issues. For example, a valve problem on the Atlas V rocket stopped the first launch attempt on May 7. A computer problem on the ground caused another delay on June 1. There were also small helium leaks inside the Starliner itself. Finally, the third launch attempt on June 5, 2024, was successful!

Why the Mission Was Delayed
The Starliner Capsule
The Astronaut Crew
The Mission Journey
See also

Why the Mission Was Delayed

The Starliner program had many problems that caused delays. The very first uncrewed test flight, called Boe-OFT, was delayed from 2017 to 2019. During that flight, software errors stopped the Starliner from reaching the ISS.

After that, a second uncrewed test flight was planned for 2021. But it was stopped because of serious valve problems. The next attempt in 2022 was successful. This meant the crewed test flight could finally be planned.

However, in August 2023, Boeing announced more delays. There were concerns about the strength of parts in the parachute system. Also, there were worries about the wiring possibly catching fire. Because of these issues, Boeing had to do many checks before the crewed flight was allowed.

The Starliner Capsule

The Starliner capsule used for this mission is named Calypso. This was its second trip to space. It was first used for the very first uncrewed test flight.

NASA announced in August 2020 that Calypso would be prepared for this mission. It received new parachutes and airbags. The part of the capsule that connects to the ISS was also changed. This was to fit a new cover that was first used on the second uncrewed test flight.

The Astronaut Crew

Because of all the delays, the astronauts assigned to this mission changed several times. The first crew was chosen in 2018.

Nicole Aunapu Mann was supposed to be on this mission. She would have been the first woman to fly on the first crewed flight of a new spacecraft. But she was later moved to the SpaceX Crew-5 mission.
Eric Boe was first assigned as the pilot in August 2018. But he was replaced by Michael Fincke in January 2019 for health reasons.
Boeing astronaut Chris Ferguson was originally the commander. But he was replaced by NASA astronaut Barry E. Wilmore in October 2020. Ferguson said he needed to spend more time with his family.

On April 18, 2022, NASA said they hadn't decided which astronauts would fly on this mission. But on June 16, 2022, NASA confirmed that this flight would have two people: Barry Wilmore and Sunita Williams. Michael Fincke trained as a backup pilot. Sunita Williams is the first woman to fly on the first crewed flight of a new type of orbital spacecraft.

Prime crew
Position	Launching astronaut	Landing astronaut
Commander	Barry E. Wilmore Expedition 71/72 Third spaceflight	None
Pilot	Sunita Williams Expedition 71/72 Third spaceflight	None

Backup crew
Position	Astronaut
Commander	Michael Fincke

The Mission Journey

Mission Overview

The Atlas V rocket launched the Starliner with its two astronauts. The spacecraft was supposed to connect with the International Space Station. Then, it would return to Earth for a landing in the southwestern United States.

The mission was planned for eight days. But the Starliner had problems with its propulsion system (the parts that make it move). The mission was extended many times so engineers could study the issues. Eventually, NASA decided to leave the crew on the ISS. The Starliner returned to Earth without them after three months in space. The astronauts will come back on a different spacecraft.

This mission was special because it was the first time a crewed spacecraft launched on an Atlas V rocket. It was also the first time a crewed spacecraft launched from Cape Canaveral Space Force Station since 1968.

Launch Day

Starliner capsule stacked on top the Atlas V rocket before launch

In 2023, the mission was delayed to March 2024. This was because of problems with the parachute system and concerns about wiring catching fire. By November 2023, NASA said the mission was on track for an April 2024 launch. Most of the flammable material was removed. A test of the new parachute system was successful in January 2024.

In February 2024, the Atlas V rocket was moved to its launch building. This started preparations for stacking the Starliner on top. In March 2024, the launch was moved to early May because of scheduling at the ISS. The Starliner spacecraft was finished on April 15. It was moved to the launch pad and stacked on the Atlas V rocket the next day.

The astronauts arrived at Kennedy Space Center on April 25. On the same day, the mission was officially approved to proceed. On May 2, another spacecraft, the SpaceX Crew-8 Dragon, moved to a different port on the ISS. This made room for the Starliner, which could only dock at one specific port. The Atlas V rocket was moved to its launch pad on May 4.

First Launch Attempt: May 6, 2024

The first launch attempt on May 6, 2024, was stopped about two hours before liftoff. This was because of a noisy oxygen valve on the rocket's upper stage. This problem had happened before on Atlas V flights. It could usually be fixed by closing and reopening the valve. But rules said they couldn't do that with astronauts on board. So, the launch was stopped.

The next day, the team decided the valve needed to be replaced. This delayed the launch to May 17. Meanwhile, NASA and Boeing found a small helium leak on the Starliner. This caused even more delays.

Second Launch Attempt: June 1, 2024

After studying the helium leak, NASA and Boeing decided on May 24 to launch on June 1. They believed the spacecraft was safe to fly even if the leak got worse. They also found a small design weakness in the propulsion system. This could prevent the spacecraft from returning to Earth in a very rare case. Engineers then created a new way to return if this problem happened.

Astronauts Barry Wilmore and Sunita Williams flew back to Kennedy Space Center on May 28. On May 29, the teams confirmed they were ready for a June 1 launch.

In late May, a pump on the ISS that turns astronaut urine into drinking water broke. NASA decided to send a replacement pump on the Starliner. To make space for the pump, Wilmore and Williams had to leave their personal clothes and toiletries behind. They would use spare items already on the ISS.

The second launch attempt on June 1 was stopped just under four minutes before liftoff. This happened because one of the ground computers was working too slowly. It was found that a faulty power supply unit caused this. On June 2, the team replaced the part, and it worked normally.

Successful Launch: June 5, 2024

The Starliner finally launched on the Atlas V rocket on its third try, on June 5 at 10:52 am EDT. The launch happened from Cape Canaveral Space Force Station in Florida. This was the 100th flight for the Atlas V rocket.

The rocket flew in a special setup. It had two solid rocket boosters and two engines on its second stage. The solid rocket boosters fell away about 2 minutes and 20 seconds after launch. The main part of the rocket kept firing for about 4 and a half minutes. Then, the second stage fired its engines. The Starliner separated from the rocket about 15 minutes after liftoff.

To keep the astronauts safe, the rocket put the Starliner into a slightly lower orbit. The Starliner then used its own thrusters to enter its final orbit about 31 minutes after launch.

Flying to the ISS and Docking

Starliner approaching the ISS during the Crew Flight Test (CFT)

After reaching orbit, the astronauts practiced controlling the spacecraft. They pointed the antenna, aimed the solar panels, and even manually moved the spacecraft. The Starliner can fly by itself, but these tests showed the crew could take over in an emergency.

Later on June 5, ground controllers found two more helium leaks in the Starliner's propulsion system. To manage these leaks, they temporarily turned off parts of the system. This disabled six of the spacecraft's 28 small thrusters. The leaks were small, and there was still enough helium for the mission. So, they were allowed to dock. A fourth, even smaller leak was found after docking. The cause of these leaks is still unknown. But it seems to be a problem with the propulsion system.

As the Starliner got close to the ISS, five thrusters on the back of the spacecraft stopped working. This made it hard for the spacecraft to control its direction. The mission teams managed to get four of the thr thrusters working again. They did this by resetting them and testing them. During this time, the crew manually held the spacecraft just outside the station's safe zone. After checking the thrusters, the Starliner was allowed to dock. A similar problem happened during the uncrewed test flight in 2022.

The Starliner connected to the front part of the ISS Harmony module on June 6. This was almost 27 hours after launch, including an hour-long delay because of the thruster problem. Astronauts Butch Wilmore and Suni Williams entered the station. They joined the other astronauts already living there.

Staying on the ISS

Starliner docked to the ISS as seen from the Crew-8 Dragon spacecraft

On June 7, the Starliner astronauts spent their first full day on the ISS. They moved cargo and emergency equipment between the Starliner and the station. One important item they unpacked was a new pump for the station's toilet system. This system turns urine into drinking water. The old pump had broken, so the new one was added to the Starliner's cargo at the last minute. By the next day, the new pump was installed and working.

On June 8, the crew tested the Starliner's ability to be a "safe haven" in an emergency. This means it could protect the crew for a long time or allow them to leave the station quickly. This is a requirement for any crewed spacecraft visiting the ISS. The Starliner astronauts, along with two other ISS crew members, also tested living conditions inside the Starliner with four people. On June 9, the crew continued checking the Starliner as part of their tests. The spacecraft was then put into a low power mode until it was time to undock.

From June 10, the Starliner crew started helping with general ISS maintenance and research. They did health checks, worked on computer maintenance, and helped with a space fire investigation. They also talked to people on Earth, including students at Sunita Williams' old elementary school. They continued with biomedical activities, like collecting microbe samples and sequencing genes. They also helped prepare for a planned spacewalk.

Boeing Starliner Spacecraft 3 Calypso docked to the ISS during the Crew Flight Test

NASA said that since arriving, Wilmore and Williams spent half their time on research. This gave their crewmates more time to prepare for another spacecraft's departure.

While Starliner was docked, NASA and Boeing kept checking its performance. They focused on the helium leaks and thruster problems. NASA delayed the end of the mission many times to keep testing the spacecraft in space. This was important because the service module (which has the thrusters) is thrown away before returning to Earth. So, this was their only chance to collect data from it.

On June 10, NASA reported a fifth small helium leak and a new problem: a valve that didn't close properly. On June 15, they tested the thrusters. Seven out of eight thrusters worked normally. One thruster that couldn't be fixed during docking was deemed unusable. This test also showed that all five helium leak rates had decreased. The cause of the helium and thruster problems was still unknown. Managers thought the intense movements during docking might have caused some of the issues.

In July, a team started ground tests in New Mexico on a thruster like those on the Starliner. They tried to copy the conditions Calypso experienced. They found that a Teflon seal had changed shape. Heat seemed to cause the seals to bulge and block the fuel flow. However, when they tested this on the Starliner in orbit, the same problem wasn't seen. This suggested the seals might not be the main cause.

Because of these results, some NASA engineers were still worried about the Starliner. They couldn't agree that it was safe to bring the astronauts back on it. Boeing, however, felt confident in the Starliner.

Due to this uncertainty, NASA delayed the launch of the SpaceX Crew-9 mission. NASA wanted the Starliner to undock from the ISS before Crew-9 arrived. NASA also thought about different ways to bring the astronauts home if Starliner was unsafe. This included launching Crew-9 with two empty seats.

The seven Expedition 71 crew members gather with the two Crew Flight Test members for a team portrait aboard the space station
Starliner docked to the ISS as seen from the Cupola
Suni Williams, Tracy C. Dyson, and Jeanette Epps (left to right) pose for a portrait during dinner time on the Unity module
Suni Williams pictured inside the Harmony module
Williams and Wilmore in the vestibule that connects the ISS to Starliner

Uncrewed Return to Earth

NASA first planned for the Starliner to undock and return to Earth on June 14. This would have ended an eight-day stay. But the landing was delayed many times. This allowed NASA and Boeing to investigate the helium leaks and thruster failures. On June 28, NASA said the Starliner would not be approved to fly until its thruster problems were understood.

On August 24, NASA announced that it was too risky to bring Wilmore and Williams back on the Starliner. The crew would return in 2025 on a Crew Dragon spacecraft. This means the SpaceX Crew-9 mission will launch with two astronauts instead of four. The two empty seats will be for Williams and Wilmore. Since the ISS only has two docking ports, the Starliner had to undock before Crew-9 could connect.

Boeing disagreed with some news reports saying the astronauts were "stuck" in space. After NASA decided the Starliner would return without a crew, Boeing chose to release only short statements. Reporters felt that NASA and Boeing should have been more open about the mission.

The Starliner's original plan for returning home involved the astronauts closing the hatch. Then, after about three hours of preparation, it would undock. The capsule would then fly around the station in a spiral. Finally, it would fire its thrusters to begin the trip back to the western United States. The capsule would have landed about six and a half hours later.

Instead, the uncrewed Starliner undocked on September 6. It performed a simpler maneuver to move away from the ISS. It mostly used its forward-facing thrusters, which had no problems during docking. The spacecraft then fired its engines to begin its descent to Earth.

Crews inspect Boeing Starliner Spacecraft 3 Calypso after landing.

The Starliner reentered Earth's atmosphere about six hours after undocking. It deployed three parachutes, slowing the capsule down. Before landing, six airbags inflated to cushion the landing. It landed in the White Sands Missile Range in New Mexico on September 7. All possible landing sites were in the western United States. This allowed the service module to be dropped off to burn up safely over the Pacific Ocean.

During its return, the Starliner had two new technical problems. These were not related to its earlier issues. There was a brief glitch in its navigation system. Also, one of the 12 thrusters used to control the capsule during reentry failed to ignite. This thruster was different from the ones that caused problems in orbit.