Boeing Starliner


The Boeing Starliner is a spacecraft designed to transport crew to and from the International Space Station and other low-Earth-orbit destinations. Developed by Boeing under NASA's Commercial Crew Program, it consists of a reusable crew capsule and an expendable service module.
Slightly larger than the Apollo command module 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 in Florida.
In 2014, NASA awarded Boeing a US$4.2 billion fixed-price contract to develop and operate Starliner, while SpaceX received $2.6 billion to develop and operate Crew Dragon. 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, so it returned 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 different approach: companies would own and operate spacecraft while NASA would act as a customer, purchasing flights as needed. NASA offered funding to support the development of these new vehicles, but unlike previous cost-plus contracts these new contracts would be fixed-price, placing the financial risk of cost overruns on the companies themselves.
Boeing had an extensive history of developing vehicles for space exploration, having built the first stage of the Saturn V rockets, assembling the Lunar Roving Vehicles, and serving as the prime contractor for the US Orbital Segment of the ISS since 1993. Hence, Boeing was suitable 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 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 rocket to be human-rated 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-3 at Kennedy Space Center would be leased to Boeing for manufacture and test of Starliner, through a partnership with Space Florida.
Over the next three years, NASA held three more rounds of development funding, awarding Boeing $92.3 million under CCDev2 in 2011, $460 million under the Commercial Crew integrated Capability program in 2012, and $9.9 million under the Certification Products Contract in 2013.
NASA was expected to announce its selection for the lucrative Commercial Crew Transportation Capability 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 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 Crew Dragon. 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 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 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 project.
The spacecraft consists of a reusable capsule and an expendable service module and is designed for missions to low Earth orbit. The capsule accommodates seven passengers, or a mix of crew and cargo. For NASA 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. Boeing 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. 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. 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.
Solar cells 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 and consists of 64 engines:
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, 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 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, 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 in New Mexico, the Willcox Playa in Arizona and the Dugway Proving Ground in Utah. Edwards Air Force Base 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 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 internal budget overruns for the Starliner program, exceeding $2billion as of 2025.
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.