On August 7, 2023, Boeing revealed to Business Insider that they were planning to target a March window for their first crewed flight of their Starliner capsule carrying astronauts Sunita “Suni” Williams and Barry “Butch” Wilmore to the International Space Station. This announcement, while seemingly long overdue, represents one of the final steps to begin regular operational missions to the orbiting laboratory. Human certification for the vehicle will provide the redundancy that NASA so desperately needs, and represents a triumph over numerous technical and logistics issues for the Starliner team. It is crucial however, to understand how the program got to this point, and what role the vehicle will serve once it is finally certified to begin ISS rotations.
Boeing’s Starliner was one of two spacecraft selected by NASA as part of their Commercial Crew program – an initiative to reduce costs by contracting private entities to fly NASA astronauts. This model differs significantly from previous operations, in which NASA constructed and operated their own fleet of spacecraft. Under Commercial Crew, the spacecraft are owned and operated by the vendor, and crew transportation is provided to NASA as a commercial service. Each mission typically sends up to four astronauts to the ISS, with an option for a fifth passenger available. Operational flights occur approximately once every six months for missions that last for just as long. A spacecraft remains docked to the ISS during its mission, and missions usually overlap by at least a few days. Work began on the Commercial Crew program in 2011, immediately after the wind down of the Space Shuttle program, but was marred by insufficient funding at the get-go which resulted in lengthy delays.
With the program established in 2011 and work finally beginning, a series of open competitions over the following two years saw successful bids from Boeing, Blue Origin, Sierra Nevada, and SpaceX to develop proposals for ISS crew vehicles. In 2014, NASA awarded separate fixed-price contracts to Boeing and SpaceX to develop their respective systems and fly astronauts to the ISS. Each contract required successful demonstrations to achieve human rating for the system, including pad abort, uncrewed orbital test, launch abort, and a crewed orbital test. Operational missions were initially planned to begin in 2017, with missions alternating between the two providers. Delays required NASA to purchase additional seats on Soyuz spacecraft up to Soyuz MS-17 until Crew Dragon missions began in 2020.
For a majority of the program, Boeing’s Starliner has remained firmly in second place when compared to SpaceX’s Crew Dragon, suffering from numerous hurdles, which Boeing has worked feverishly and tirelessly to remedy. Starliner’s unique land-landing design required a new series of validation tests, and a comprehensive review of parachute systems pushed the debut flight out by a considerable margin. In May 2019, all major hot-fire testing including simulations of low-altitude abort-thruster testing, was completed using a full 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, one of the final milestones for flight – simulating an escape from a hypothetical compromised launch vehicle on the pad. This pad abort test took place on November 4, 2019. The capsule accelerated away from its pad, but one of the three parachutes failed to deploy, and the capsule landed with only two parachutes (Which, while off nominal, is within margins for the vehicle). Landing was, however, deemed safe, and the test a success. With these tests out of the way Boeing could proceed towards their Orbital Flight Test.
Boeing’s Orbital Flight Test was intended to mirror the DM-1 test performed by SpaceX, and certify the spacecraft for safe approach and rendezvous with the orbiting lab. The first Atlas V N22, designated AV-080, launched the CST-100 Starliner spacecraft on an uncrewed test flight to the International Space Station on December 20, 2019 for a mission planned to last 8 days. The capsule was intended to dock with the space station and then return to Earth to land in the Western United States after an orbital shakedown cruise ahead of Boeing Crewed Flight Test. This, however, did not go to plan. Thirty-one minutes after launch the mission elapsed timer (MET) clock experienced a critical error. During a later press conference, it was revealed that the MET was offset by 11 hours. When it became obvious that the orbit raising maneuver did not happen and the spacecraft was out of attitude, NASA and Boeing tried sending commands to get Starliner back on track, but the position of the spacecraft switching communications between two TDRS satellites delayed the orbital insertion burn. This delay resulted in an abnormal orbit and excessive fuel use. The decision was made to abort the ISS rendezvous/docking due to the spacecraft’s excessive fuel use, even with the MET issue fixed. Starliner returned to Earth two days later, landing at White Sands Space Harbor on December 22nd. Though the ISS rendezvous that was planned for the OFT did not happen, Jim Chilton, Vice President for Boeing’s space and launch division, estimated that Starliner had achieved over 60% of the flight objectives, and this could reach over 85% once all the data from the spacecraft was retrieved and analyzed.
On July 7th, 2020 NASA and Boeing announced the completion of the OFT review, a comprehensive look at the issues that took place on the flight and steps required to move forward. The number of corrective actions was increased to 80 from the initial March 2020 update. Twenty-one recommendations focused on a need for more testing and simulations; including the necessity to do full end-to-end tests prior to flights instead of testing in chunks as done for the leadup to the OFT. Ten recommendations were made to cover software requirements such that they have proper coverage to catch errors during testing. 35 of the recommendations surrounded improvements over process and operations such as including more reviews and use of experts. Seven recommendations covered software updates that addressed the three main anomalies that occurred during the flight. The final 7 included “Knowledge Capture” and Boeing organizational changes to enable better safety reporting. They also included hardware changes to filter out radio interference and others to address the communication issue. With the investigation complete, Boeing and NASA concluded that a repeat of the OFT would be necessary before flying a crewed demonstration mission.
As part of the original fixed-price contract, the redo flight of OFT was paid for by Boeing at an estimated out-of-pocket cost to the company of $410 million USD. The mission ended up using the hardware, Starliner spacecraft, and Atlas V originally planned for use on the Boe-CFT crewed flight test. The mission had been planned for late 2021, but issues including moisture intrusion in the service module and the rather dramatic arrival of the Russian Nauka module ultimately resulted in a re-manifest of Station traffic, forcing a lengthy delay for the Starliner team. Orbital Flight Test-2 lifted off for the ISS atop another Atlas V N22 vehicle on May 19th, 2022, from Launch Complex 41 at Cape Canaveral Space Force Station. Starliner separated from the Atlas V launch vehicle after successful suborbital insertion. During the Orbit Insertion Burn, two OMAC thrusters out of the twelve thrusters in the service module failed shortly after ignition, but Boeing claimed it did not pose a threat. On-board flight control systems took over the situation and switched to backup thrusters to complete the burn successfully, placing Starliner in a good orbit. Twenty-six hours and 34 minutes after the beginning of the mission, Starliner achieved soft capture on its first docking attempt. Twenty minutes later the spacecraft achieved a hard capture. Docking took place after a delay of about one hour due to a need to retract and re-extend the ring clamp on its NASA Docking System docking interface. After several days mated to the station, Starliner undocked from ISS and returned to Earth, landing at White Sands Space Harbor on May 25th, 2022.
With the OFT successfully completed, Boeing mission engineers began to look for opportunities to fly their next mission, the coveted Crewed Flight Test. The Boeing CFT would have resembled SpaceX’s DM-2, with the spacecraft performing a rendezvous and docking with crew onboard, and a short duration stay. As Boeing was preparing to ramp up for launch in June 2023, issues regarding a certain kind of aerospace grade tape known as P213 and wiring harnesses cropped up, prompting a stand down to investigate, and an indefinite delay – once again setting the team back. The third Atlas V N22 launch vehicle variant was planned to launch Starliner with a crew of two, Sunita Williams and Barry “Butch” Wilmore. The vehicle would then dock with the International Space Station and return to Earth under parachutes for a ground-landing in the United States at White Sands Space Harbor. In the lead up to the projected launch time, Boeing teams were refurbishing the crew module from the OFT-1 mission for the Crew Flight Test. This would have been the first launch of a crewed spacecraft by an Atlas V launch vehicle. Based upon current space station resources and scheduling needs, a short duration mission with two astronaut test pilots would be 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. In an August 7th telecon, providing an update on the vehicle, both NASA and Boeing stressed their firm commitment to resolving these issues and getting the spacecraft flying by March of 2024. For the P213 tape, NASA databases were inconsistent as to its flammability, which ultimately interfered with operations. It is worth noting that this same kind of tape is standard across other aerospace manufacturers, and most of the tape found on Starliner is in the easily accessible upper dome of the spacecraft, and where inaccessible, further mitigation actions would be carried out. Higher-ups from both NASA and the NESC have been brought in to inspect the vehicle and certify it for flight.
As Starliner once again finds itself waiting, there is some speculation as to what the future of the program will look like. Boeing’s space division has long been plagued by cultural issues, and issues in communication can lead to unacceptable conditions when it comes time to fly. It is easy to quickly glance at the program and write it off as a lost cause, or a target for cancellation. Mark Nappi of Boeing said in the August 7th telecon that he “expects to complete all of the contracted missions by the time the International Space Station is retired” around the end of the decade. Crews which were assigned to Starliner missions have seen themselves moved to SpaceX crew rotations, including NASA’s Jeanette Epps and JAXA’s Koichi Wakata. A limited number of Atlas vehicles means that Starliner will require a new ride to space once the available launch vehicles are no more – necessitating a new process for human certification. But, there is an element of hope to the Starliner story. Once the vehicle is certified, missions will switch between both Commercial Crew providers, ensuring that the ISS has the redundancy it needs in the face of an unstable international political situation. The vehicle has prospects beyond ISS in an age of commercial space. Blue Origin has named Boeing as one of their providers for their Commercial Low Earth Orbit station Orbital Reef, as well as Northrop Grumman for their proposal. The fifth seat onboard Starliner could enable further international opportunities, bringing short duration astronauts to the ISS or other LEO destinations as part of handovers. While Starliner may have had the rockier start, the attention to detail on the part of the Boeing team brings confidence in their commitment to get it right, a reminder that even in an age of competitive and fast spaceflight, diligence and determination can produce a product that sticks around for a good long while. With the March target in sight and a straightforward path laid out, Starliner looks ready to once again take to the skies.
Edited by David Diebold and Beverly Casillas.