Boeing Crew Flight Test Explained

Boeing Crew Flight Test
Names List:Boe-CFT[1]
Mission Type:Flight test
Operator:Boeing
Mission Duration:Planned:
8 days
Elapsed:
Spacecraft Type:Boeing Starliner
Manufacturer:Boeing
Launch Date:UTC (10:52:15amEDT)
Launch Rocket:Atlas V N22 (AV-085)[2]
Launch Site:Cape Canaveral, SLC41
Launch Contractor:United Launch Alliance
Landing Site:White Sands Missile Range
Crew Size:2
Docking:
Docking Type:dock
Docking Port:Harmony forward
Docking Date:6 June 2024, 17:34UTC
Time Docked: (in progress)
Orbit Reference:Geocentric orbit
Orbit Regime:Low Earth orbit
Orbit Inclination:51.66°
Apsis:gee
Insignia:Boeing CFT patch.png
Insignia Caption:Boeing Crew Flight Test mission patch
Crew Photo:Boeing CFT Crew Portrait-Sunita Williams and Barry Wilmore (KSC-20240404-PH-NAS01 0001).jpg
Crew Photo Caption:Williams (left) and Wilmore (right)
Programme:Commercial Crew Development
Previous Mission:Boeing OFT-2
Programme2:Boeing Starliner flights
Previous Mission2:Boeing OFT-2
Next Mission2:Boeing Starliner-1

Boeing Crew Flight Test (Boe-CFT) is the first crewed mission of the Boeing Starliner capsule. Launched on 5 June 2024, the mission flew a crew of two NASA astronauts, Barry E. Wilmore and Sunita Williams, from Cape Canaveral Space Force Station to the International Space Station. The mission was meant to last eight days, ending with a landing in the American Southwest on 14 June. However, the capsule's thrusters malfunctioned and helium leaked as Starliner docked with the ISS, and NASA decided not to fly the spacecraft back to Earth until the problems were solved or at least better understood. Wilmore and Williams remain aboard the ISS, after their launch. NASA says it plans to decide by mid-August how to return Wilmore and Williams to Earth: on Starliner or on a SpaceX Dragon capsule with the Boeing spacecraft returning uncrewed.

The flight was initially to occur in 2017, but various delays pushed back the launch. The spacecraft's first two uncrewed orbital flight tests, Boe-OFT and Boe-OFT-2, took place in 2019 and 2022 respectively.

The spacecraft was integrated with the Atlas V launch vehicle on 16 April 2024 in preparation for launch. The flight was scheduled for 7 May 2024 but was scrubbed about two hours before liftoff due to an oxygen valve problem on United Launch Alliance's (ULA) Atlas V. The launch was repeatedly delayed due to a leak of helium, which is used to pressurize the reaction control system thrusters in the Starliner service module. The second launch attempt was on 1 June, but was scrubbed 3 minutes, 50 seconds before liftoff when the ground launch sequencer computer registered a loss of redundancy due to a faulty power supply. The third launch attempt on 5 June at 14:52:15UTC (10:52:15amEDT local time at the launch site) was successful.

During the flight, more helium leaks were discovered, and as the Starliner approached the ISS, five of the 28 thrusters failed. Resetting and firing the thrusters eventually showed that four of the five were again functioning, and the Starliner docked with the ISS after a delay.

Delays

Multiple development problems caused the first uncrewed test to be delayed from 2017 until 2019. Another major delay occurred after software errors prevented Starliner from reaching the ISS during that flight. A second uncrewed test flight attempt in 2021 was scrubbed due to serous valve problems found before launch, and the next attempt in 2022 was then successful and met all flight objectives. This enabled the scheduling of the crewed test flight.[3] However, Boeing announced in August 2023 that it would be delayed to no earlier than March 2024 due to problems with the strength of certain joints within the parachute system and concerns over the potential for combustion of the wiring harnesses. As a result, Boeing underwent multiple investigations before another flight test would be permitted.[4]

Capsule

CFT is the second mission for the Starliner Calypso capsule, which was first used on the first Orbital Flight Test. NASA announced that Boeing prepared to reassemble the vehicle for flight, following multiple checkouts, for the CFT mission in August 2020, and that new parachutes and airbags would be fitted. The CFT capsule's docking system was modified to accommodate the new re-entry cover that debuted on the OFT-2 test flight.

Crew

Because of the delays, crew assignments were changed several times after the initial assignments in 2018. Nicole Mann was initially assigned to this mission, which would have made her the first woman to fly on the maiden crewed flight of an orbital spacecraft, but was subsequently re-assigned to the SpaceX Crew-5 mission as the first female commander of a NASA Commercial Crew Program launch. For medical reasons, Eric Boe, who was originally assigned to the mission in August 2018 as the pilot, was replaced by Michael Fincke on 22 January 2019. Boe replaced Fincke as the assistant to the chief for commercial crew in the astronaut office at NASA's Johnson Space Center. Boeing astronaut Chris Ferguson was originally assigned to the flight as commander, but he was replaced by NASA astronaut Barry E. Wilmore on 7 October 2020. Ferguson cited family reasons for the replacement. Matthew Dominick replaced him on the backup crew.

On 18 April 2022, NASA said that it had not finalized which of the cadre of Starliner astronauts, including Barry E. Wilmore, Michael Fincke, and Sunita Williams, would fly on this mission or the first operational Starliner mission. On 16 June 2022, NASA confirmed that this CFT mission is a two-person flight test, consisting of Wilmore and Williams; Fincke is to train as the backup spacecraft test pilot and remains eligible for assignment to a future mission.[5] Williams is the first woman to fly on a maiden crewed flight of an orbital spacecraft type.

Mission

Overview

The third launch of the Atlas V N22 variant launched Starliner with a crew of two. The vehicle docked with the International Space Station and will return to Earth for a ground landing in the southwestern United States.

Boe-CFT is the first launch of a crewed spacecraft by an Atlas V launch vehicle. In addition, the mission is the first launch of a crewed spacecraft utilizing a member of the Atlas family of launch vehicles since Mercury-Atlas 9 flown by Gordon Cooper in May 1963[6] and the first launch of a crewed spacecraft from Cape Canaveral Space Force Station since that of Apollo 7 in October 1968.

A short-duration mission with two astronaut test pilots is sufficient to meet all NASA and Boeing test objectives for CFT, which include demonstrating Starliner's ability to safely fly operational crewed missions to and from the space station.

The Starliner will make a ground landing in the Western United States, a first for a crewed capsule mission launched from the United States, which has all made a splashdown in an ocean.

Launch

In 2023, following the discovery of a technical problem with the spacecraft's parachute system and a flammability concern on the spacecraft's wiring, CFT was delayed to no earlier than March 2024.[7] In November 2023, NASA announced that the mission was on track for an April 2024 launch, with most of the flammable material removed from the spacecraft and a drop-test of the redesigned parachute system planned for January 2024.[8] This test was successful, allowing NASA and Boeing to proceed into launch preparations.[9] In February 2024, the Atlas V rocket was moved into ULA's Vertical Integration Facility at Space Launch Complex-41, starting preparations for stacking ahead of the launch.[10] [11] In March 2024, the launch was rescheduled from 22 April to early May due to scheduling conflicts on the ISS,[12] with a launch date of 6 May announced in early April.[13] Work on the Starliner spacecraft inside Boeing's production facility was completed on 15 April, and the spacecraft was moved to the launch pad and stacked on top the Atlas V rocket the following day.[14] [15] [16] The crew arrived at Kennedy Space Center on 25 April,[17] and on the same day the mission concluded its Flight Test Readiness Review, officially approving the mission to proceed.[18] On 2 May, the SpaceX Crew-8 Dragon spacecraft relocated from the forward port of the ISS Harmony module to the zenith port, to make room for the CFT mission, which is only approved to dock on the forward port.[19] Following the completion of ULA's Launch Readiness Review, the Atlas V rocket rolled to its launch pad on 4 May.[20]

The first attempt to launch CFT, on 6 May 2024, was scrubbed around T-2 hours before launch due to a problem with an oxygen valve on the rocket's Centaur upper stage.[21] [22] While this problem had been seen in previous Atlas V flights and could be resolved simply by closing and reopening the valve, new flight rules prohibited doing so with crew on board, which forced the decision to scrub the launch.[23] [24] The next day, the launch team determined that this faulty valve would need to be replaced, with the rocket having to be rolled back to its Vertical Integration Facility, delaying the launch to 17 May.[25] [26] Meanwhile, in an unrelated problem, NASA and Boeing discovered a small helium leak on Starliner's propulsion system, which delayed the launch further to allow the teams to assess the situation.[27] [28] On 24 May, following several days of analysis, NASA and Boeing announced plans to launch CFT on 1 June without repairing the helium leak, determining that the spacecraft was safe to fly even if the leak rate worsened by many times. This review also uncovered a "design vulnerability" in the propulsion system that could prevent the spacecraft from completing a deorbit burn in a very remote failure mode; engineers then devised a new reentry mode to employ should this failure mode occur.[29] [30] Astronauts Barry Wilmore and Sunita Williams after returning to Houston following the previous scrub, flew back to Kennedy Space Center on 28 May. After a 29 May meeting, teams from NASA, Boeing, and ULA confirmed readiness for a 1 June launch.[31] [32] [33]

In late May, the pump in the ISS urine processor assembly malfunctioned, halting the ability to convert the crew's waste back into drinkable water. NASA made the decision to place a replacement pump on the Starliner. To maintain a consistent mass and accommodate the 64kg (141lb) pump, Wilmore and Williams suitcases were removed, which contained personal clothes and toiletries, instead the CFT crew will use generic spare clothes and toiletries already aboard the ISS.[34] [35]

The second launch attempt, on 1 June, was scrubbed 3 minutes and 50 seconds before liftoff after an automatic hold was triggered when one of three redundant ground launch sequencer computers gave slower-than-normal readings.[36] [37] This was found to have been caused by a faulty power supply unit connected to that computer. On 2 June, a ULA team replaced the computer chassis containing this power supply and verified that the new hardware was performing normally.[38]

CFT lifted off on the Atlas V rocket on its third launch attempt, on 5 June at 10:52 am EDT. The mission was launched from ULA's SLC-41 launch site at Cape Canaveral Space Force Station, Florida, and was Atlas V's 100th flight. The rocket flew in the N22 configuration, with no payload fairing, two GEM 63 solid rocket boosters, and two RL10A-4-2 engines on the Centaur second stage. The solid rocket boosters separated from the rocket 2 minutes and 20 seconds after liftoff. The core stage continued firing until 4 minutes and 28 seconds after launch and was separated shortly thereafter. The Centaur second stage then began firing until 11 minutes and 52 seconds after launch. The Starliner spacecraft separated from the second stage about 15 minutes after liftoff. To maximize safety, it was placed in a sub-orbital trajectory by the rocket and used its own thrusters to enter orbit about 31 minutes after launch.[39] [40]

Launch attempt summary

Note: times are local to the launch site (Eastern Daylight Time).

CFT mission launch events[41] [42]
Time Event
L−6:00:00 Atlas V cryo load
L−4:00:00 Atlas V cryo load complete/stable configuration
L−4:30:00 Crew suit-up begins
L−4:04:00 T-4 minute hold begins
L−3:20:00 Crew suit-up complete/departs for the launch pad
L−3:10:00 Crew Module preps begin
L−2:50:00 Crew arrives for insertion
L−1:20:00 Hatch closure complete
L−0:50:00 Cabin leak checks/cabin pressurization complete
L−0:35:00 Crew space to ground communication checks
L−0:22:00 Flight Director Poll: Go for terminal count
L−0:20:00 Crew visors configured for launch
L−0:18:00 Starliner poll for terminal count
L−0:18:00 Starliner to internal power
L−0:11:00 Crew access arm retracted
L−0:07:00 Atlas V launch vehicle poll for terminal count
L−0:07:00 Starliner configured for terminal count
L−0:05:00 Starliner configured for ascent
L−0:04:00 T-4 minute hold releases
L−0:00:02.7 RD-180 engine ignition
L+0:00:01.1 Liftoff (thrust to weight > 1)
L+0:00:06.0 Begin pitch/yaw maneuver
L+0:01:01.7 Maximum dynamic pressure
L+0:01:05.3 Mach 1
L+0:02:20.4 SRB jettison
L+0:04:28.9 Atlas Booster Engine Cutoff (BECO)
L+0:04:34.9 Atlas separation from Centaur
L+0:04:40.9 Ascent cover jettison
L+0:04:44.9 Centaur First Main Engine Start (MES-1)
L+0:05:04.9 Aeroskirt jettison
L+0:11:55.4 Centaur First Main Engine Cutoff (MECO-1)
L+0:14:55.4 Starliner Separation

Cruise and docking

In the hours after getting into orbit, the crew performed several manual maneuvering exercises, including pointing the antenna towards the TDRSS communications satellites, pointing the solar panels towards the sun, manually using the star tracker, manually braking and accelerating the spacecraft to perform orbital maneuvers, and manually orienting the spacecraft for reentry. Although the Starliner spacecraft is designed to operate autonomously and these capabilities are not required in a nominal mission, these tests showed that the crew can take over many functions of the craft during an emergency.[43]

Late on 5 June, just before the crew's sleep time, flight controllers on the ground detected two more helium leaks in different parts of Starliner's propulsion system. To manage these leaks, flight controllers temporarily closed the two helium manifolds associated with the new leaks, which disabled six of the spacecraft's 28 reaction control system thrusters. The leaks were described as small and the spacecraft still had plenty of helium to complete its mission, so managers gave permission to dock. The helium manifolds were reopened during rendezvous and docking and were subsequently closed once the spacecraft docked, as is standard procedure. A fourth leak, smaller than the other three, was detected after docking. The cause of the helium leaks is not yet known, but NASA and Boeing's managers acknowledged that this appears to be a systemic problem with the propulsion system, contrary to their expectations before the mission that the first helium leak was an isolated problem caused by one defective seal.[44] [45] [46]

As Starliner approached the ISS, five reaction control system thrusters unexpectedly ceased to work. Mission teams managed to bring back four of the thrusters by doing a series of resets and hot-fire tests on them, during which the crew manually held the spacecraft just outside the station's 200-meter keep-out zone. After verifying that the thrusters were operating normally, Starliner was permitted to dock with the station. A similar problem occurred during the uncrewed OFT-2 mission in 2022: thrusters in the same location in the spacecraft were deactivated during the approach. Mission managers believe the failure of the thrusters could be related to input data being outside some predetermined limits rather than being a software or hardware problem, although the exact cause is unknown.[47]

Starliner docked with the forward port of the ISS Harmony module on 6 June at 1:34 pm EDT, nearly 27 hours after launch, including an hour-plus delay caused by the thruster problem.[48] Astronauts Butch Wilmore and Suni Williams entered the station at 3:45 pm EDT, joining Expedition 71 crewmembers Jeanette Epps, Matthew Dominick, Tracy C. Dyson, and Michael Barratt of NASA, and Oleg Kononenko, Nikolai Chub, and Alexander Grebenkin of Roscosmos.[49]

ISS stay

On 7 June, the CFT astronauts spent their first full day aboard the ISS transferring cargo and emergency gear in and out of Starliner. They were helped by ISS crewmates Michael Barratt and Matthew Dominick.[50] Among the items unpacked was a new pump for the station's urine processing facility, which converts urine into drinking water. It was added as a last-minute change to Starliner's cargo manifest after the station's old pump malfunctioned on 29 May.[32] [33] By the next day, the new pump was already installed and operating properly.[51]

On 8 June, the crew tested the ability of the Starliner vehicle to act as a "safe haven" in the event of an emergency at the ISS, which includes sheltering the crew for an extended time or quickly departing the station if needed. This is a requirement for any crewed vehicle that visits the ISS. The CFT astronauts were also joined by Matthew Dominick and Tracy C. Dyson to test the living conditions on Starliner with a crew of four inside.[51] On 9 June, the CFT crew continued performing checks on Starliner as part of their flight test objectives.[52] The spacecraft was then switched to a low power mode, in which it will stay until undocking preparations begin at the end of the mission.[53]

On 10 June, with all their initial Starliner testing completed, the CFT crew started working on general ISS maintenance and research activities. They started their day by measuring their temperature, blood pressure, pulse, and respiratory rate. Later, Wilmore worked on the maintenance of a computer connected to the Microgravity Science Glovebox, while Williams installed hardware to support a space fire investigation. They also participated in a number of public-relations events where they talked to people on Earth, including a call to Sunita L. Williams Elementary School, located in Williams' hometown of Needham, Massachusetts.[53] [54] On 11 June, the astronauts spent their time on biomedical activities, with Wilmore organizing the inventory of the Human Research Facility, and Williams working on procedures to collect microbe samples and sequence their genes. They also participated in an event with Tennessee Tech, Wilmore's home university.[55] On 12 June, Wilmore checked cargo in the Harmony module and worked on maintenance of the station's bathroom, while Williams continued her gene sequencing work from the day before.[56] On 13 June, the CFT crew worked to support a planned spacewalk by astronauts Matt Dominick and Tracy Dyson; they helped the pair during the suit-up process, and, once the spacewalk was canceled, helped them get out of their spacesuits. Later in the day, they took an inventory of the personal consumables they had used up to that point and worked with flight controllers to update their tablets with emergency procedures.[57]

On 14 June, after their undocking date was pushed back to 22 June, the CFT astronauts had a call with Boeing mission managers to discuss the end of the mission and then entered Starliner to review the spacecraft's flight operations and procedures.[58] On the weekend of 15 and 16 June, they performed tasks related to their CFT mission and assisted the ISS crew.[59] On 17 June, Williams worked on maintenance tasks and prepared the Advanced Plant Habitat for future experiments, and on 18 June she continued working on the gene sequencing study from the prior week. Meanwhile, Wilmore spent the two days working on a study of the behavior of flowing liquids in space.[60] [61]

NASA said that since their arrival on 6 June, Wilmore and Williams have been tasked with completing half of all hands-on research time conducted aboard the ISS, giving their crewmates more time to prepare for the departure of Northrop Grumman’s Cygnus NG-20 spacecraft.[62]

While Starliner is docked to the ISS, NASA and Boeing teams have continued to assess the spacecraft's performance, especially relating to the helium leaks and RCS thruster problems. NASA delayed the end of the mission several times to continue testing the spacecraft in space; because the service module is discarded on reentry, NASA and Boeing will not have another opportunity to collect data from it. On a 10 June update, NASA reported a fifth small helium leak in the service module, plus a new problem: an RCS oxidizer isolation valve that did not close properly.[63] [64] On 15 June, the spacecraft was powered on for a test of the RCS thrusters, during which seven of eight aft-facing thrusters performed nominally, including four of the five that had malfunctioned during docking. One thruster, which could not be restored during docking, was deemed unusable and will not be used for the remainder of the mission. This test also enabled engineers to measure the helium leaks in the spacecraft, and all five leak rates were found to have decreased. The cause of the helium and thruster problems remained unknown. NASA managers speculated that the intense "dynamic operations" during the docking sequence could have contributed to the problems.[65] [66]

In July, a joint NASA-Boeing team began conducting ground tests at the White Sands Missile Range in New Mexico on an RCS thruster that was planned to be used on a future Starliner mission.[67] The team simulated conditions that Calypso experienced from launch to docking with over 1,000 pulses, then simulating five undock-to-deorbit firing sequences with 500 pulses, including sequences with longer and more frequent pulses. These tests were completed by 18 July.

During these tests, the team was able to replicate the thrust degradation that caused the thrusters to fail. When the test thruster was disassembled, the team found that a Teflon seal had been deformed.[68] A buildup of heat appears to have caused Teflon seals in the thruster to bulge and constrict the flow of propellant. However, when the tests were replicated on the Starliner in orbit, the same problem was not seen, and even thrusters which had previously lost significant thrust performed close to normal,[69] suggesting that the seals might not be the root cause.

After those results, at a meeting of key NASA engineers called the Program Control Board, Ken Bowersox said, "We heard from a lot of folks that had concerns." The meeting ended with no agreement on flight rationale for returning Wilmore and Williams to Earth on Starliner.[70]

Boeing, for its part, has expressed confidence in Starliner and believes there is flight rationale for returning the spacecraft to Earth with the astronauts aboard.[71]

Amid the uncertainty, NASA delayed the launch of its SpaceX Crew-9 mission originally scheduled for 18 August to 24 September 2024.[72] [73] NASA says that it wants Starliner to be undocked from the ISS before the launch of Crew-9.[74] The agency is also considering several return scenarios if Starliner is deemed unsafe to bring Williams and Wilmore home, including launching Crew-9 with two empty seats.[75] [76] However, NASA said that taking such an action would add additional risks as the Starliner would require a software update to allow it to fly autonomously.[77]

Return to Earth

NASA's original plan was for Starliner to undock from the ISS and return to Earth on 14 June, concluding an eight-day stay.[78] Since then, the landing date has been pushed back several times by NASA and Boeing in order for engineers to better understand what had caused the maneuvering thrusters to fail and what was causing the helium leaks.[79] [80] [81]

On 28 June, NASA announced that while Starliner could return the astronauts to Earth if the ISS were to experience an emergency, the capsule would not be approved to fly until its thruster problems were solved or at least better understood. The extension of the astronauts' stay was highly emphasized in the press, with some reports stating that they were "stuck" in space. Boeing criticized these reports, while reporters argued NASA and Boeing should be more transparent about the mission.[82] While NASA and Boeing initially said Starliner could remain docked to the ISS for up to 45 days,[83] they later said that Starliner would actually be able to stay docked for up to 90 days when considering the performance of the onboard batteries.[84]

If the crew returns on Starliner, then it would take about three hours to prepare to undock from the ISS after they close the hatch. Once undocked, Starliner would make a flight around the station before firing the service module thrusters to begin the trip back to the western United States, where the capsule would land about six and a half hours later.[85]

Starliner would make a ground landing, a first for a crewed capsule mission launched from the United States. After reentering the atmosphere, three parachutes would be deployed, slowing the capsule to about 4mph. Before reaching the ground, six airbags would deploy to cushion the landing. The prime landing targets are two sites inside the White Sands Missile Range in New Mexico. Other potential landing locations include the Willcox Playa in Arizona and the Dugway Proving Ground in Utah. Edwards Air Force Base in California serves as a contingency landing location.[86] All of the landing sites are in the western United States, allowing the service module to be jettisoned for a destructive reentry over the Pacific Ocean.[87]

See also

Notes and References

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  2. Web site: 21 March 2023 . Atlas 5 • CST-100 Starliner Crew Flight Test . 27 July 2024 . Spaceflight Now.
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  5. Web site: Potter . Sean . 16 June 2022 . NASA Updates Astronaut Assignments for Boeing Starliner Test Flight . live . https://web.archive.org/web/20220616201752/https://www.nasa.gov/press-release/nasa-updates-astronaut-assignments-for-boeing-starliner-test-flight/ . 16 June 2022 . 17 June 2022 . NASA.
  6. News: Sloan . Kaycee . 1 May 2024 . Astronauts to launch from Cape Canaveral for first human spaceflight in nearly 56 years . live . https://web.archive.org/web/20240503122329/https://www.wfla.com/glance-at-the-galaxy/astronauts-to-launch-from-cape-canaveral-for-first-human-spaceflight-in-nearly-56-years/ . 3 May 2024 . 3 May 2024 . WFLA-TV.
  7. Web site: 8 August 2023 . First Starliner crewed flight delayed to 2024 . live . https://web.archive.org/web/20240605235757/https://spacenews.com/first-starliner-crewed-flight-delayed-to-2024/ . 5 June 2024 . 5 June 2024.
  8. Web site: 21 November 2023 . Starliner "on track" for April crewed test flight . live . https://web.archive.org/web/20240605235757/https://spacenews.com/starliner-on-track-for-april-crewed-test-flight/ . 5 June 2024 . 5 June 2024.
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  13. Web site: 2 April 2024 . NASA, Boeing Update Launch Date for Starliner's First Astronaut Flight – NASA's Boeing Crew Flight Test . live . https://web.archive.org/web/20240504233230/https://blogs.nasa.gov/boeing-crew-flight-test/2024/04/02/nasa-boeing-update-launch-date-for-starliners-first-astronaut-flight/ . 4 May 2024 . 5 June 2024.
  14. Web site: 15 April 2024 . NASA, Boeing Prep Starliner to Join Rocket Ahead of Crew Flight Test – NASA's Boeing Crew Flight Test . live . https://web.archive.org/web/20240603163101/https://blogs.nasa.gov/boeing-crew-flight-test/2024/04/15/nasa-boeing-prep-starliner-to-join-rocket-ahead-of-crew-flight-test/ . 3 June 2024 . 5 June 2024.
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  29. Web site: 24 May 2024 . NASA and Boeing moving ahead with Starliner test flight after propulsion issues . live . https://web.archive.org/web/20240606000406/https://spacenews.com/nasa-and-boeing-moving-ahead-with-starliner-test-flight-after-propulsion-issues/ . 6 June 2024 . 5 June 2024.
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  32. Web site: 31 May 2024 . Starliner ready for next crewed test flight launch attempt . live . https://web.archive.org/web/20240605235857/https://spacenews.com/starliner-ready-for-next-crewed-test-flight-launch-attempt/ . 5 June 2024 . 5 June 2024.
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  34. Web site: Dinner . Josh . 31 May 2024 . The ISS has a urine pump problem. Boeing's Starliner astronaut launch will flush it out. . 10 July 2024 . Space.com . en.
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  36. Web site: June 2024 . Starliner launch attempt scrubbed . live . https://web.archive.org/web/20240606000409/https://spacenews.com/starliner-launch-attempt-scrubbed/ . 6 June 2024 . 5 June 2024.
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  40. Web site: Rosenstein . Sawyer . Boeing's Starliner CFT launches on third attempt . live . https://web.archive.org/web/20240602041232/https://www.nasaspaceflight.com/2024/06/starliner-cft-launch/ . 2 June 2024 . 5 June 2024.
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  43. Web site: Starliner Manual Piloting Demonstrations Successful . live . https://web.archive.org/web/20240606164022/https://starlinerupdates.com/starliner-manual-piloting-demonstrations-successful/ . 6 June 2024 . 7 June 2024.
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  45. Web site: 6 June 2024 . Boeing's Starliner finally soars, but mission control reports more helium leaks . live . https://web.archive.org/web/20240606152718/https://arstechnica.com/space/2024/06/after-a-successful-launch-boeings-starliner-runs-into-more-helium-leaks/ . 6 June 2024 . 7 June 2024.
  46. Web site: 7 June 2024 . After a drama-filled day, Boeing's Starliner finally finds its way . live . https://web.archive.org/web/20240607002406/https://arstechnica.com/space/2024/06/after-a-drama-filled-day-boeings-starliner-finally-finds-its-way/ . 7 June 2024 . 7 June 2024.
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  55. Web site: Garcia . Mark . 11 June 2024 . Crew Works Genetics, Maintenance and is GO for Spacewalk . NASA.
  56. Web site: Garcia . Mark . 12 June 2024 . Astronauts Work Final Spacewalk Preps and Genetic Sequencing . NASA.
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  58. Web site: Garcia . Mark . 14 June 2024 . Spacewalks Rescheduled Before Station Boosts Orbit . NASA.
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  61. Web site: Garcia . Mark . 18 June 2024 . Spacewalks, Biotech Research are Tuesday's Focus on Station . NASA.
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  65. Web site: Foust . Jeff . 18 June 2024 . Starliner ISS stay extended to complete thruster and helium leak testing .
  66. Web site: Berger . Eric . 18 June 2024 . NASA delays Starliner return a few more days to study data . Ars Technica.
  67. Web site: 3 July 2024 . Starliner testing continues in space and on the ground to support future long-duration missions . 10 July 2024 . Boeing.
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  76. News: Sheetz . Michael . 2 August 2024 . NASA weighs Boeing vs. SpaceX choice in bringing back Starliner astronauts . CNBC.
  77. Web site: Wattles . Jackie . 7 August 2024 . Boeing Starliner astronauts have now been in space more than 60 days with no end in sight . 7 August 2024 . CNN . en.
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  79. Web site: Wall . Mike . 10 June 2024 . Boeing's 1st Starliner astronaut mission extended through June 18 . 10 June 2024 . Space.com.
  80. News: Sanders . Chris . Roulette . Joey . Chiacu . Doina . 14 June 2024 . Boeing Starliner set for June 22 undocking, return to Earth, NASA says . 14 June 2024 . Reuters.
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  82. News: Roulette . Joey . 28 June 2024 . Boeing Starliner's return from space to hinge on weeks of more testing . 28 June 2024 . Reuters.
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