The Boeing Starliner (or CST-100) is a spacecraft designed to transport crew to and from the

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

(ISS) and other low-Earth-orbit destinations. Developed by

Boeing The Boeing Company, or simply Boeing (), is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, and missiles worldwide. The company also provides leasing and product support s ...

under

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

Commercial Crew Program The Commercial Crew Program (CCP) provides Private spaceflight, commercially operated human spaceflight, crew transportation service to and from the International Space Station (ISS) under contract to NASA, conducting crew rotations between t ...

(CCP), it consists of a reusable crew capsule and an expendable

service module A service module (also known as an equipment module or instrument compartment) is a component of a crewed space capsule containing a variety of support systems used for spacecraft operations. Usually located in the uninhabited area of the spacec ...

. Slightly larger than the

Apollo command module The Apollo command and service module (CSM) was one of two principal components of the United States Apollo (spacecraft), Apollo spacecraft, used for the Apollo program, which landed astronauts on the Moon between 1969 and 1972. The CSM functi ...

or SpaceX Crew Dragon, but smaller than the Orion capsule, the Starliner can accommodate a crew of up to seven, though NASA plans to fly no more than four. It can remain docked to the ISS for up to seven months and is launched on an Atlas V N22 rocket from

Cape Canaveral Space Launch Complex 41 Space Launch Complex 41 (SLC-41), sometimes referred to as "Slick Forty-one," is one of two launch sites at the Integrate-Transfer-Launch Complex in Cape Canaveral Space Force Station, Florida. Originally built as Launch Complex 41 (LC-41), it and ...

in Florida. In 2014, NASA awarded Boeing a US$4.2 billion

fixed-price contract A fixed-price contract is a type of contract for the supply of goods or services, such that the agreed payment amount will not subsequently be adjusted to reflect the resources used, costs incurred or time expended by the contractor. This contract ...

to develop and operate Starliner, while SpaceX received $2.6 billion to develop and operate

Crew Dragon Dragon 2 is a class of partially reusable spacecraft developed, manufactured, and operated by the American space company SpaceX for flights to the International Space Station (ISS) and private spaceflight missions. The spacecraft, which consi ...

. By February 2025, Boeing's effort had exceeded its budget by at least $2billion. Originally planned to be operational in 2017, Starliner has been repeatedly delayed by problems in management and engineering. The first uncrewed Orbital Flight Test in December 2019 was deemed a partial failure, leading to a second Orbital Flight Test in May 2022. During the Crew Flight Test, launched in June 2024, the Starliner's thrusters malfunctioned on approach to the ISS and NASA concluded that it was too risky to return its astronauts to Earth aboard the spacecraft, which landed uncrewed in September 2024.

Background

As the Space Shuttle program drew to a close, NASA sought to foster the development of new spaceflight capabilities. Departing from the traditional model of government-owned and operated spacecraft, NASA proposed a revolutionary approach: companies would own and operate spacecraft, while NASA would act as a customer, purchasing flights as needed. To incentivize innovation, NASA offered funding to support the development of these new vehicles. However, unlike previous

cost-plus contract A cost-plus contract, also termed a cost plus contract, is a contract such that a contractor is paid for all of its allowed expenses, ''plus'' an additional payment to allow for risk and incentive sharing.fixed-price, placing the financial risk of cost overruns on the companies themselves. Boeing has an extensive history of developing vehicles for space exploration, having built the first stage (

S-IC The S-IC (pronounced S-one-C) was the first stage of the American Saturn V rocket. The S-IC stage was manufactured by the Boeing Company. Like the first stages of most rockets, more than 90% of the mass at launch was propellant, in this case RP ...

) of the

Saturn V The Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, had multistage rocket, three stages, and was powered by liquid-propel ...

rockets, assembling the

Lunar Roving Vehicle The Lunar Roving Vehicle (LRV) is a Battery electric vehicle, battery-powered four-wheeled Rover (space exploration), rover used on the Moon in the last three missions of the American Apollo program (Apollo 15, 15, Apollo 16, 16, and Apollo 17 ...

s, and serving as the prime contractor for the

US Orbital Segment The US Orbital Segment (USOS) is the name given to the components of the International Space Station (ISS) constructed and operated by the United States National Aeronautics and Space Administration (NASA), European Space Agency (ESA), Canadian ...

of the ISS since 1993. With its proven track record and deep expertise, Boeing was seen as well-positioned to compete for the commercial spaceflight contracts. In 2010, Boeing unveiled its entry into NASA's Commercial Crew Program competition: the CST-100. The company received initial funding of $18 million in the first round of the Commercial Crew Development (CCDev 1) program to support Starliner's development. Additionally, United Launch Alliance, a joint venture between Boeing and Lockheed Martin, secured $6.7 million to develop the Emergency Detection System to allow its

Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to ...

rocket to be

human-rated Human-rating certification, also known as man-rating or crew-rating, is the certification of a spacecraft or launch vehicle as capable of safely transporting humans. There is no one particular standard for human-rating a spacecraft or launch veh ...

to launch Starliner. At the time, Boeing expressed optimism that the Starliner could be operational as early as 2015, contingent upon timely approvals and funding. In October 2011, NASA announced that the

Orbiter Processing Facility Orbiter Processing Facility (OPF) is a class of hangars where U.S. Space Shuttle orbiters underwent maintenance between flights. They are located west of the Vehicle Assembly Building, where the orbiter was mated with its external tank and Space ...

-3 at

Kennedy Space Center The John F. Kennedy Space Center (KSC, originally known as the NASA Launch Operations Center), located on Merritt Island, Florida, is one of the NASA, National Aeronautics and Space Administration's (NASA) ten NASA facilities#List of field c ...

would be leased to Boeing for manufacture and test of Starliner, through a partnership with Space Florida. Over the next three years, NASA would hold three more rounds of development funding, awarding Boeing $92.3 million under CCDev2 in 2011, $460 million under the Commercial Crew integrated Capability (CCiCap) program in 2012, and $9.9 million under the Certification Products Contract (CPC) in 2013. NASA was expected to announce its selection for the lucrative Commercial Crew Transportation Capability (CCtCap) contract in September 2014. Boeing had lobbied NASA for a sole-source contract, arguing that it needed the program's full budget for the successful development of Starliner. Within NASA, there was considerable support for this approach, with many decision-makers expressing confidence in Boeing's capabilities and safety record. In fact, NASA officials had even drafted a justification for selecting Boeing as the sole provider. While William H. Gerstenmaier, NASA's human exploration lead, had considered the Starliner proposal as stronger, he was hesitant to award a sole-source contract. The multi-year Commercial Crew Program had been designed to foster competition and redundancy, and Gerstenmaier believed that selecting just one company would undermine these goals. Through his efforts, he successfully convinced NASA to delay the CCtCap announcement and secure additional funding to support two competing efforts. On September 16, 2014, NASA announced that both Boeing and

SpaceX Space Exploration Technologies Corp., commonly referred to as SpaceX, is an America, American space technology company headquartered at the SpaceX Starbase, Starbase development site in Starbase, Texas. Since its founding in 2002, the compa ...

would be awarded CCtCap contracts to develop crewed spacecraft. Boeing received a US$4.2 billion to complete and certify the Starliner, while SpaceX received a US$2.6 billion to complete and certify

. To receive the full contract amount, each company would need to successfully complete an abort test, an uncrewed orbital flight test, a crewed orbital flight test, and six crewed missions to the ISS. However, NASA would not need to pay for any failed tests and was only required to purchase two crewed missions to the ISS from each company. Following the initial guaranteed missions, the companies would compete for launch contracts on an ongoing basis. In November 2015, NASA announced that it had dropped Boeing from consideration in the separate multibillion-dollar

Commercial Resupply Services Commercial Resupply Services (CRS) are a series of flights awarded by NASA for the delivery of cargo and supplies to the International Space Station (ISS) on commercially operated spacecraft. The first phase of CRS contracts (CRS-1) were sign ...

competition to fly cargo to the International Space Station.

Development

The name CST-100 was first used when the capsule was unveiled to the public in June 2010. The acronym "CST" stands for Crew Space Transportation, while the number "100" represents to the

Kármán line The Kármán line (or von Kármán line ) is a conventional definition of the Outer space#Boundary, edge of space; it is widely but not universally accepted. The international record-keeping body Fédération Aéronautique Internationale, FAI ( ...

, the unofficial boundary of space located at an altitude of above Earth. The design draws upon Boeing's experience with NASA's Apollo, Space Shuttle, and ISS programs, as well as the

Orbital Express Orbital Express: ASTRO and NEXTSat Orbital Express was a space mission managed by the United States Defense Advanced Research Projects Agency (DARPA) and a team led by engineers at NASA's Marshall Space Flight Center (MSFC). The Orbital Express p ...

project.

The spacecraft consists of a reusable capsule and an expendable service module and is designed for missions to

low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...

. The capsule accommodates seven passengers, or a mix of crew and cargo. For

missions to the ISS it will carry four passengers and a small amount of cargo. The Starliner capsule uses a weldless, spun-formed structure and is reusable up to ten times with a six-month turnaround time.

plans to alternate between two reusable crew modules for all planned Starliner missions. Each flight uses a new service module, which provides propulsion and power-generation capacity for the spacecraft. Starliner features wireless Internet and tablet technology for crew interfaces. Starliner uses the

NASA Docking System The NASA Docking System is NASA's implementation of the International Docking System Standard (IDSS), an international spacecraft docking standard promulgated by the International Space Station Multilateral Coordination Board. NDS is a Docking an ...

. Boeing modified the Starliner design prior to OFT-2, adding a hinged re-entry cover below its expendable nosecone for additional protection of the docking port during

atmospheric entry Atmospheric entry (sometimes listed as Vimpact or Ventry) is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. Atmospheric entry may be ''uncontrolled entr ...

. This was tested on the OFT-2 mission. By contrast, the reusable SpaceX Dragon 2 nosecone is hinged and protects its docking port during both launch and reentry. The capsule uses the Boeing Lightweight Ablator for its re-entry

heat shield In engineering, a heat shield is a component designed to protect an object or a human operator from being burnt or overheated by dissipating, reflecting, and/or absorbing heat. The term is most often used in reference to exhaust heat management a ...

Solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s provided by Boeing subsidiary Spectrolab are installed onto the aft face of the service module, providing 2.9 kW of electricity. In addition to the capsule and service module, a structure called an aeroskirt is integrated into the launch vehicle adapter of Atlas V. The aeroskirt provides aerodynamic stability and dampens the shock waves that come from the front of the rocket. The spacecraft's propulsion system is produced by

Aerojet Rocketdyne Aerojet Rocketdyne is a subsidiary of American Arms industry, defense company L3Harris that manufactures rocket, Hypersonic flight, hypersonic, and electric propulsive systems for space, defense, civil and commercial applications. Aerojet traces ...

and consists of 64 engines: * 12 × MR-104J RCS (

reaction control system A reaction control system (RCS) is a spacecraft system that uses Thrusters (spacecraft), thrusters to provide Spacecraft attitude control, attitude control and translation (physics), translation. Alternatively, reaction wheels can be used for at ...

) thrusters on the capsule, using hydrazine

monopropellant Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with biprop ...

and reserved for orienting the capsule during atmospheric re-entry * 52 on the service module using monomethylhydrazine and

nitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

bipropellant: ** 28 × RCS thrusters on the service module for attitude control during the majority of the flight ** 20 × OMAC (orbital maneuvering and attitude control) thrusters for altering orbits ** 4 × RS-88 engines for launch escape capability in the event of an abort The RCS and OMAC thrusters on the service module are grouped into four "doghouses" equally spaced around the perimeter of the service module, each containing five OMAC thrusters (three aft-facing and two forward-facing), and seven RCS thrusters: two aft-facing, two forward-facing, and one each in the radial and two tangential directions. The latter three are in a plane which is very close to the spacecraft's center of mass. To translate the spacecraft, thrusters are used in balanced pairs so that the center of force goes through the spacecraft's center of mass. To rotate the spacecraft, thrusters are used in unbalanced pairs so there is no net force and the net torque is centered within the spacecraft. The RCS thrusters are used for rotation (attitude control) and very fine docking maneuvers, while the OMAC thrusters are used for significant orbital adjustments. The RCS thrusters are also used to compensate for slight imbalances in the OMAC thrusters. Boeing designed the capsule to make ground landings instead of a

splashdown Splashdown is the method of landing a spacecraft or launch vehicle in a body of water, usually by parachute. This has been the primary recovery method of American capsules including NASA’s Mercury, Gemini, Apollo and Orion along with th ...

, a first for a crewed capsule mission launched from the United States. After reentering the atmosphere, three parachutes are deployed, slowing the capsule to approximately . Before reaching the ground, six airbags deploy to cushion the landing. There are four primary landing locations, including two sites inside the

White Sands Missile Range White Sands Missile Range (WSMR) is a United States Army military testing area and firing range located in the US state of New Mexico. The range was originally established in 1941 as the Alamogordo Bombing and Gunnery Range, where the Trinity t ...

in New Mexico, the Willcox Playa in Arizona and the

Dugway Proving Ground Dugway Proving Ground (DPG) is a United States Army facility established in 1942 to test biological and chemical weapons, located about southwest of Salt Lake City, Utah and south of the Utah Test and Training Range. Location Dugway Provin ...

in Utah.

Edwards Air Force Base Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, California, Kern County, but its eastern end is in San Bernardino County, California, San Bernardino County and a souther ...

in California serves as a contingency landing location. 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. Boeing says that between all five landing sites, there are around 450 landing opportunities each year. Following the award of the Commercial Crew Transportation Capability (CCtCap) contract in 2014, NASA assigned a team of four experienced astronauts, Bob Behnken, Eric Boe, Doug Hurley and Sunita Williams, to serve as consultants to engineers at both Boeing and SpaceX. These astronauts were also slated to be the test pilots on the inaugural missions. Hurley recounted a stark contrast in the working relationships between the astronauts and the engineers at the two companies. While the SpaceX engineers were receptive to feedback, enthusiastic about collaborating, and attentive to suggestions, Hurley found the Boeing engineers to be indifferent, arrogant, and overconfident. He also said the Boeing team failed to inform the astronauts about the propellant leak that occurred during the Pad Abort Test. Ultimately, Hurley told the chief of the astronaut office that he would not fly on Starliner. Hurley and Behnken later went on to command the Crew Dragon's historic Demo-2 mission, the first crewed flight of the spacecraft. Williams flew into space on the Boeing Crew Flight Test, but returned to Earth on a Crew Dragon, after thrusters malfunctioned on the Starliner. Despite being initially awarded significantly more funding, Boeing faced substantial budget overruns for the Starliner program, exceeding $2billion . In November 2019, NASA's Office of Inspector General released a report revealing that a change to Boeing's contract had occurred in 2016, stating: "For Boeing's third through sixth crewed missions, we found that NASA agreed to pay an additional $287.2 million above Boeing's fixed prices to mitigate a perceived 18-month gap in ISS flights anticipated in 2019 and to ensure the contractor continued as a second commercial crew provider", and NASA and Boeing committed to six missions instead of the last four being optional. In August 2024, after the setbacks experienced during the Crew Flight Test, NASA Administrator

Bill Nelson Clarence William Nelson II (born September 29, 1942) is an American politician, attorney, and former astronaut who served from 2001 to 2019 as a United States Senate, United States senator from Florida and from 2021 to 2025 as the Administrator ...

stated that Boeing CEO Kelly Ortberg committed to continuing the Starliner program. However, financial analysts expressed skepticism that Boeing would continue to invest in a money-losing program, and in October ''

The Wall Street Journal ''The Wall Street Journal'' (''WSJ''), also referred to simply as the ''Journal,'' is an American newspaper based in New York City. The newspaper provides extensive coverage of news, especially business and finance. It operates on a subscriptio ...

'' reported that Boeing was exploring a sale of some of its space division programs, including Starliner. But in March 2025, Commercial Crew Program manager Steve Stich stated that the next flight may happen in late 2025 or early 2026.

Testing

Various validation tests began on test articles in 2011 and continued on actual spacecraft starting in 2019.

Abort and drop tests

In September 2011, Boeing announced the completion of a set of ground

drop test A drop test is a method of testing the in-flight characteristics of prototype or experimental aircraft, experimental aircraft and spacecraft by raising the test vehicle to a specific altitude and then releasing it. Test flights involving powered ...

s to validate the design of the airbag cushioning system. The airbags are located underneath the heat shield of the Starliner, which is designed to be separated from the capsule while under parachute descent at about altitude. The airbags, manufactured by ILC Dover, are deployed by filling with a mixture of compressed nitrogen and oxygen gas, not with the pyro-explosive mixture sometimes used in automotive airbags. The tests were carried out in the

Mojave Desert The Mojave Desert (; ; ) is a desert in the rain shadow of the southern Sierra Nevada mountains and Transverse Ranges in the Southwestern United States. Named for the Indigenous peoples of the Americas, indigenous Mohave people, it is located pr ...

of southeast California, at ground speeds between in order to simulate crosswind conditions at the time of landing. Bigelow Aerospace built the mobile test rig and conducted the tests. In April 2012, Boeing dropped a mock-up of its Starliner over the

Nevada desert Nevada ( ; ) is a landlocked U.S. state, state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the List of U.S. stat ...

at the Delamar Dry Lake,

Nevada Nevada ( ; ) is a landlocked state in the Western United States. It borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the seventh-most extensive, th ...

, successfully testing the craft's three main landing parachutes from . Boeing reported in May 2016 that its test schedule would slip by eight months in order to reduce the mass of the spacecraft, address aerodynamics issues anticipated during launch and ascent on the Atlas V rocket, and meet new NASA-imposed software requirements. The Orbital Flight Test was scheduled for spring 2019. The booster for this Orbital Flight Test, an Atlas V N22 rocket, was assembled at

United Launch Alliance United Launch Alliance, LLC (ULA) is an American launch service provider formed in December 2006 as a joint venture between Lockheed Martin Space and Boeing Defense, Space & Security. The company designs, assembles, sells and launches rockets ...

's (ULA) facility at

Decatur, Alabama Decatur () is the largest city and county seat of Morgan County, Alabama, Morgan County (with a portion also in Limestone County, Alabama, Limestone County) in the U.S. state of Alabama. Nicknamed "The River City," it is located in North Alabam ...

by the end of 2017. The first crewed flight ( Boe-CFT) was scheduled for summer 2019, pending test results from Boe-OFT. It was planned to last 14 days and carry one NASA astronaut and one Boeing test pilot to the ISS. On April 5, 2018, NASA announced that the first planned two-person flight, originally slated for November 2018, was likely to occur in 2019 or 2020. A serious incident occurred during a hot-fire test in June 2018. A design flaw in the propellant system left four of eight valves open, leading to the release of over of toxic monomethylhydrazine propellant, resulting in a fireball that engulfed the equipment. The incident was reportedly exacerbated by animosity with the propulsion system subcontractor, Aerojet Rocketdyne, who Boeing refused to pay for design changes. While it informed NASA of the incident, Boeing attempted to keep the incident quiet, even withholding information from the astronauts involved in the project. In October 2018, the first unpiloted orbital mission was delayed to April 2019, and the first crew launch was rescheduled to August 2019. In March 2019,

Reuters Reuters ( ) is a news agency owned by Thomson Reuters. It employs around 2,500 journalists and 600 photojournalists in about 200 locations worldwide writing in 16 languages. Reuters is one of the largest news agencies in the world. The agency ...

reported that these test flights had been delayed by at least three months, and in April 2019 Boeing announced that the unpiloted orbital mission was scheduled for August 2019. In May 2019, all major hot-fire testing, including simulations of low-altitude abort-thruster testing, was completed using a full up-to-service module test article that was "flight-like," meaning that the service module test rig used in the hot-fire testing included fuel and helium tanks, reaction control system, orbital maneuvering, and attitude-control thrusters, launch abort engines and all necessary fuel lines and avionics that will be used for crewed missions. This cleared the way for the pad abort test and the subsequent uncrewed and crewed flights. A pad abort test took place on November 4, 2019. The capsule accelerated away from its pad, but then one of the three parachutes failed to deploy, and the capsule landed with only two parachutes. Landing was, however, deemed safe, and the test a success. Boeing did not expect the malfunction of one parachute to affect the Starliner development schedule.

First orbital flight test (uncrewed)

The uncrewed Boeing Orbital Flight Test (OFT) launched on December 20, 2019, bearing an Anthropomorphic Test Device nicknamed "Rosie the Rocketeer" and clothed in Boeing's blue IVA spacesuit as well as a Plush toy of Jedediah Kerman from

Kerbal Space Program ''Kerbal Space Program'' is a 2015 Space flight simulation game, space flight simulation video game developed by Mexican studio Squad for Linux, macOS, Windows, PlayStation 4, PlayStation 5, Xbox Series X/S and Xbox One. In the game, players dir ...

. It landed two days later, having nearly ended in catastrophic failure. The mission was ultimately declared a partial failure. After launch, the spacecraft captured a " mission elapsed time" from its Atlas V launch vehicle that was 11 hours off. Consequently, when the spacecraft separated from the rocket, instead of briefly firing its reaction control thrusters to enter orbit, its computers commanded them to fire for far longer, consuming so much fuel that the spacecraft no longer had enough to dock with the ISS. As the capsule was prepared for re-entry, another software error was discovered; it could have caused a catastrophic collision between the service module and crew capsule. The spacecraft landed at

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

, two days after launch. After its landing, NASA astronaut Sunita Williams named the spacecraft ''Calypso'' after the research vessel used by

oceanographic Oceanography (), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean, including its physics, chemistry, biology, and geology. It is an Earth science, which covers a wide range of top ...

researcher

Jacques Cousteau Jacques-Yves Cousteau, (, also , ; 11 June 191025 June 1997) was a French naval officer, oceanographer, filmmaker and author. He co-invented the first successful open-circuit self-contained underwater breathing apparatus (SCUBA), called the ...

. After the mission, Boeing vice president John Mulholland acknowledged that the company had not conducted integrated end-to-end tests for the entire mission, but had instead performed tests of smaller segments. This approach contributed to the software errors that led to the near-catastrophic failures during the flight test. Mulholland insisted that Boeing cut no corners, and that end-to-end tests were not omitted to save money. NASA was also faulted for not pressing Boeing to conduct an end-to-end test. The subsequent NASA–Boeing investigation into the flight made scores of recommendations for Boeing and NASA. Boeing declared these to be proprietary, so the only ones publicly known are the ones that officials deliberately disclosed. In 2020, company officials said they were addressing 80 of the recommendations.

Second orbital flight test (uncrewed)

Because the first OFT did not achieve its objectives, Boeing officials said on April 6, 2020 that the Starliner crew capsule would fly a second uncrewed demonstration mission,

Boeing Orbital Flight Test 2 The Boeing Orbital Flight Test-2 (also known as Boe-OFT-2) was a repeat of Boeing's unsuccessful Boeing Orbital Flight Test, first Orbital Flight Test (Boe-OFT) of its Boeing Starliner, Starliner spacecraft. The uncrewed mission was part of NA ...

(OFT-2), before flying astronauts. NASA said that it had accepted a recommendation from Boeing to fly a second unpiloted mission. ''The Washington Post'' reported that the second orbital flight test, with much the same objectives as the first, was expected to launch from Cape Canaveral "sometime in October or November 2020". Boeing said that it would fund the unplanned crew capsule test flight "at no cost to the taxpayer". Boeing told investors earlier in 2020 that it was taking a US$410 million charge against its earnings to cover the expected costs of a second unpiloted test flight. Boeing officials said on August 25, 2020 that they set the stage for the first Starliner demonstration mission with astronauts in mid-2021. Boeing modified the design of the Starliner docking system prior to OFT-2 to add a re-entry cover for additional protection during the capsule's fiery descent through the atmosphere. This re-entry cover is hinged, like the SpaceX design. Teams also installed the OFT-2 spacecraft's propellant heater, thermal-protection tiles, and the airbags used to cushion the capsule's landing. The crew module for the OFT-2 mission began acceptance testing in August 2020, which is designed to validate the spacecraft's systems before it is mated with its service module, according to NASA. On November 10, 2020, NASA's Commercial Crew Program manager Steve Stich said that the second orbital flight test would be delayed until first quarter 2021 due to software issues. The uncrewed test continued to slip, with the OFT-2 uncrewed test flight being scheduled for March 2021 and the crewed flight targeted for a launch the following summer. The launch date of OFT-2 moved again with the earliest estimated launch date set for August 2021. During the August 2021 launch window some issues were detected with 13 propulsion-system valves in the spacecraft prior to launch. The spacecraft had already been mated to its launch rocket, United Launch Alliance's (ULA)

Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to launch payloads for ...

, and taken to the launchpad. Attempts to fix the problem while on the launchpad failed, and the rocket was returned to the ULA's VIF (Vertical Integration Facility). Attempts to fix the problem at the VIF also failed, and Boeing decided to return the spacecraft to the factory, thus cancelling the launch at that launch window. There was a commercial dispute between Boeing and Aerojet Rocketdyne over responsibility for fixing the problem. The valves had been corroded by intrusion of moisture, which interacted with the propellant, but the source of the moisture was not apparent. By late September 2021, Boeing had not determined the root cause of the problem, and the flight was delayed indefinitely. Through October 2021, NASA and Boeing continued to make progress and were "working toward launch opportunities in the first half of 2022", In December 2021, Boeing decided to replace the entire service module and anticipated OFT-2 to occur in May 2022. The OFT-2 mission launched on May 19, 2022. It again carried Rosie the Rocketeer test dummy suited in the blue Boeing inflight spacesuit. Two Orbital Maneuvering and Attitude Control (OMAC) thrusters failed during the orbital insertion burn, but the spacecraft was able to compensate using the remaining OMAC thrusters with the addition of the Reaction Control System (RCS) thrusters. A couple of RCS thrusters used to maneuver Starliner also failed during docking due to low chamber pressure. Some thermal systems used to cool the spacecraft showed extra cold temperatures, requiring engineers to manage it during the docking. On May 22, 2022, the capsule docked with the International Space Station. On May 25, 2022, the capsule returned from space and landed successfully. During reentry one of the navigation systems dropped communication with the GPS satellites, but Steve Stich, program manager for NASA's Commercial Crew Program, said this is not unexpected during reentry.

Third orbital flight test (crewed)

Starliner's crewed flight test was intended to be the capsule’s final evaluation before entering regular NASA service. The plan was to launch two astronauts, dock with the ISS for about a week, and return to Earth roughly eight days later. But on approach to the ISS, the spacecraft began losing several of its eight aft-facing

(RCS) thrusters. After two failed, commander Butch Wilmore took manual control, noting the vehicle was more sluggish than during a test the day before. NASA waived standard flight rules to allow docking despite the degraded conditions. Eventually four thrusters failed, resulting in a loss of

six degrees of freedom Six degrees of freedom (6DOF), or sometimes six degrees of movement, refers to the six mechanical degrees of freedom of movement of a rigid body in three-dimensional space. Specifically, the body is free to change position as forward/backw ...

(6DOF) attitude control. This statement acknowledges that

6DoF Six degrees of freedom (6DOF), or sometimes six degrees of movement, refers to the six Degrees of freedom (mechanics), mechanical degrees of freedom of movement of a rigid body in three-dimensional space. Specifically, the body is free to cha ...

control was lost due to the failures. The astronauts later described the situation as "very precarious." Wilmore could no longer fully control the capsule, but abandoning the docking attempt was not a safe option either, as the same thrusters were needed to orient Starliner for its deorbit burn and reentry. The team at NASA Mission Control (which Boeing contracted to operate the spacecraft) decided to attempt a reset—essentially a thruster reboot. Wilmore stabilized the capsule before calling down, "Hands off," allowing Mission Control to override the flight software and reactivate the failed jets. Two thrusters came back online, but shortly after, a fifth thruster failed. A second reset restored all but one thruster, allowing Starliner to complete its planned autonomous docking. During the flight, five helium leaks were also detected in the service module. Despite NASA and Boeing’s public reassurances, Wilmore and pilot Sunita Williams later admitted that on June 6 when they docked they already privately doubted Starliner’s ability to return them safely to Earth. Boeing, however, maintained confidence in the capsule’s design. NASA and Boeing continued to assess the situation, and by late August NASA had concluded that the risks of returning with crew were too high. The spacecraft returned uncrewed and landed safely at

on 7September at 04:01:35UTC (6September, 11:01:35pm MDT, local time at the landing site), about six hours after it undocked from the ISS. The mission, originally scheduled for 2017, had already been plagued by delays due to parachute system issues and wiring concerns. A launch attempt on May 6, 2024, was scrubbed due to an oxygen valve problem on the rocket. Subsequently, a helium leak in the service module further delayed the mission. Another attempt on June 1 was scrubbed due to a ground computer hardware fault. Starliner launched on June 5 at 14:52 UTC (10:52am EDT). A ground investigation later linked the thruster degradation to a

Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...

seal warped by heat. While the on-orbit issues were replicated in tests at White Sands using hardware planned for future flights, they could not be reproduced aboard the in-flight Starliner. During reentry, Starliner experienced a brief navigation glitch and the failure of an orientation thruster, issues unrelated to the earlier problems. NASA has committed to a full review of mission data to determine what further steps are needed for certification. NASA Administrator

stated that Boeing CEO Kelly Ortberg committed to continuing the Starliner program despite the setbacks. Boeing, however, drew criticism after abruptly canceling its participation in a post-landing press conference and refusing to answer questions from journalists, opting to release only brief written statements.

Commercial use

Under the CCP, Boeing owns and operates the Starliner capsules, allowing the company to offer non-CCP commercial flights if they do not interfere with NASA missions. While SpaceX has secured private commercial flights, Boeing has yet to do so. The CCP agreement permits Boeing to sell seats for space tourists on ISS flights. While initially proposed, the extended length of typical ISS missions makes this unlikely. In October 2021,

Blue Origin Blue Origin Enterprises, L.P. is an American space technology company headquartered in Kent, Washington. The company operates the suborbital New Shepard rocket and the heavy-lift New Glenn rocket. In addition to producing engines for its own ...

, Boeing, and

Sierra Nevada Corporation Sierra Nevada Corporation (also styled SNC) is an American aerospace, defense, electronics, engineering and manufacturing corporation that specializes in aircraft modification, integration and other space technologies. The corporation contracts ...

announced plans for a commercial space station called Orbital Reef. This "mixed-use business park" could be serviced by both Starliner and Sierra Nevada's Dream Chaser spacecraft.

Launch vehicle

Starliner was designed to be compatible with multiple launch vehicles, including the Atlas V,

Delta IV Delta IV was a group of five expendable launch systems in the Delta rocket family. It flew 45 missions from 2002 to 2024. Originally designed by Boeing's Defense, Space and Security division for the Evolved Expendable Launch Vehicle (EELV) p ...

Falcon 9 Falcon 9 is a Reusable launch system#Partial reusable launch systems, partially reusable, two-stage-to-orbit, medium-lift launch vehicle designed and manufactured in the United States by SpaceX. The first Falcon 9 launch was on June 4, 2010, an ...

, and Vulcan Centaur. For the three completed test flights and up to six further missions, Starliner is expected to fly atop the Atlas V. However, United Launch Alliance, the operator of the Atlas V, ceased production of the rocket in 2024 after producing vehicles for all remaining contracted launches. The vehicles have been allocated to customers, including the six needed for the remaining Starliner flights. The Starliner faces an uncertain future after that. Delta IV is retired and no more are available, the Falcon 9 is owned by crewed launch competitor SpaceX, and the Vulcan Centaur has not yet been human-rated, testing Boeing would have to pay for.

Configuration

For Starliner launches, ULA uses the Atlas N22 configuration. All other Atlas V launches use a payload fairing and the single-engine version of the Centaur upper stage. N22 is configured with no payload fairing, two solid rocket boosters (SRBs), and a Dual Engine Centaur second stage. Starliner is the only crewed payload for Atlas V. While most Atlas V launches since 2021 have used the newer Northrop Grumman GEM63 SRBs, these boosters are not rated for human spaceflight. Therefore, crewed missions employ the older Aerojet Rocketdyne AJ-60A SRBs. Although the Dual Engine Centaur had not been used since 2000 after the introduction of the more powerful Atlas V, it was brought back into service for Starliner missions. Two engines allow the rocket to fly a gentler and flatter trajectory to minimize the G-forces experienced by the astronauts and ensures the capsule can abort at any time, returning the crew to Earth in case of a problem.

Launch profile

After passing through the stages of max ''q'', SRB jettison, booster separation, Centaur ignition, nosecone and aeroskirt jettison, it releases the Starliner spacecraft at stage separation, nearly 15 minutes after lift-off on a suborbital trajectory, just below the orbital velocity needed to enter a stable orbit around Earth. After separating from the Dual Engine Centaur, the Starliner's own thrusters, mounted on its service module, boost the spacecraft into orbit to continue its journey to the International Space Station. The suborbital trajectory is unusual for a satellite launch, but it is similar to the technique used by the

Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

and

Space Launch System The Space Launch System (SLS) is an American Super heavy-lift launch vehicle, super heavy-lift Expendable launch system, expendable launch vehicle used by NASA. As the primary launch vehicle of the Artemis program, Artemis Moon landing progra ...

. It ensures that, if the spacecraft fails to make the orbital insertion burn, it will re-enter the atmosphere in a controlled way. The Starliner's orbit insertion burn begins about 31 minutes into the mission and lasts 45 seconds.

List of spacecraft

, Boeing planned to have three Boeing Starliner capsules in service to fulfill the needs of the Commercial Crew Program with each capsule expected to be capable of being reused up to ten times with a six-month refurbishment time. On August 25, 2020, Boeing announced it would alternate between just two capsules for all planned Starliner missions instead of three.

List of flights

List includes only completed or currently manifested missions. Dates are listed in

UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

, and for future events, they are the earliest possible opportunities (also known as dates) and may change. NASA has only placed orders for three Starliner flights once the capsule is certified for operational use. Under the terms of its contract with Boeing, it has the option to purchase up to six operational flights, Starliner-1 through Starliner-6. However, it is unclear if it will be possible to operate that many missions before the scheduled retirement of the ISS in 2030.

Technology partners

, reaction control system and retrorockets * Airborne Systems, parachutes * Bigelow Aerospace, elements of crew capsule *

Collins Aerospace Collins Aerospace is an American technology company that is one of the world's largest suppliers of aerospace and defense products. It was formed in 2018 from the merger of Rockwell Collins and UTC Aerospace Systems. Headquartered in Charlotte, ...

, life support systems * David Clark Company, spacesuits *

ILC Dover ILC Dover is a special engineering development and manufacturing company, globally headquartered in Frederica, Delaware. It specializes in the use of high-performance flexible materials, serving the aerospace manufacturer, aerospace, personal pr ...

, airbags *

Samsung Samsung Group (; stylised as SΛMSUNG) is a South Korean Multinational corporation, multinational manufacturing Conglomerate (company), conglomerate headquartered in the Samsung Town office complex in Seoul. The group consists of numerous a ...

, mobile communications technology * Spincraft, crew module pressure shell spin-form work

Notes

References

External links

* by Boeing (2010) * by Boeing (2014)
Reporter's Starliner Notebook

Astronaut Doug Hines enters the Boeing Starliner for the first time during OFT-2

Boeing Commercial Crew Transportation Capability Contract (CCtCap)
- the fixed price contract with NASA for the Starliner program {{Crewed ISS flights American spacecraft Bigelow Aerospace Starliner Commercial spaceflight Crewed spacecraft Reusable spacecraft Supply vehicles for the International Space Station