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Boeing and NASA Prepare for Crewed Flight Test

Boeing’s Starliner spacecraft approaches the International Space Station during the OFT-2 mission in 2022.
Credit: NASA

On May 6th, 2024, Boeing’s CST-100 Starliner spacecraft is set to fly for the third time, this time carrying its most important cargo to date: a human crew. Flown by veteran NASA astronauts Barry “Butch” Wilmore and Sunita “Suni” Williams, this mission intends to fully certify the vehicle for human flight, validating all of the hard work and determination that has led up to this mission. The crew, launching atop their Atlas V N22 launch vehicle, will spend slightly over a week in space as they put their spacecraft, Calypso, through her paces. While the Starliner development process has not been easy, it has remained essential for the future of ISS access – ensuring necessary redundancy and resilience in the event of a spacecraft’s grounding. 

The crew of Boeing’s Crew Flight Test (CFT) represent some of NASA’s best and brightest, joining the crew of Expedition 71 onboard the International Space Station for a short stay while systems onboard Starliner and Station are assessed. The crew for this mission has fluctuated over time, given the program’s lengthy delays requiring astronauts be reassigned to different, operational missions. Marine Corps veteran Nicole Aunapu Mann was initially assigned to the CFT mission, which would have made her the first woman to fly on the maiden crewed flight of an orbital spacecraft, but was subsequently reassigned to the SpaceX Crew-5 mission as the first female commander of a NASA Commercial Crew Program launch. Due to medical reasons, Eric Boe, who was originally assigned to the mission in August 2018 as pilot, was replaced by Michael Fincke on 22 January 2019. Boeing astronaut Chris Ferguson was originally assigned to the flight as commander, but he was replaced by NASA astronaut Barry Wilmore on 7 October 2020. Ferguson cited family reasons for the replacement. On 16 June 2022, NASA confirmed that Boeing’s CFT mission will be a two-person flight test, consisting of Barry Wilmore and Sunita Williams; Fincke was assigned to train as the backup spacecraft test pilot and remains eligible for assignment to a future mission.

Barry Wilmore and Sunita Williams pose with their T-38 jets after arriving in Florida for preflight operations, the last step before boarding their capsule for flight.
Credit: Derek Newsome for

Barry “Butch” Wilmore will be the commander for the mission. A veteran of two spaceflights, Wilmore has 178 days in space under his belt. In 2009, he served as a pilot aboard space shuttle Atlantis for STS-129. Additionally, Wilmore served as a flight engineer for Expedition 41 until November 2014, when he assumed command of the station upon arrival of the Expedition 42 crew. He returned to Earth the following March. Prior to being selected by NASA in 2000, the father of two obtained both his bachelor’s degree and master’s degree in Electrical Engineering from Tennessee Technological University, Cookeville, before graduating with another master’s degree in Aviation Systems from the University of Tennessee, Knoxville. He is also a graduate of the United States Naval Test Pilot School, Patuxent River, Maryland, and has completed four operational deployments during his tenure as a fleet naval officer and aviator. 

Sunita “Suni” Williams will be the pilot for the flight test. Williams has spent 322 days in space across two missions: Expedition 14/15 in 2006 through 2007, and Expedition 32/33 in 2012. The Massachusetts native also conducted seven spacewalks, totaling 50 hours and 40 minutes. Before her career began with NASA in 1998, Williams graduated with her bachelor’s degree in Physical Science from the U.S. Naval Academy, Annapolis, Maryland, before obtaining her master’s degree in Engineering Management from the Florida Institute of Technology, Melbourne. In total, she has logged more than 3,000 flight hours in over 30 different aircraft.

As the final flight test for Starliner, NASA’s Boeing-Crew Flight Test will validate the transportation system, including the launch pad, rocket, spacecraft, in-orbit operational capabilities, and return to Earth with astronauts aboard. NASA astronauts Butch Wilmore and Suni Williams will fly Starliner, lifting off aboard ULA’s (United Launch Alliance) Atlas V rocket from Space Launch Complex-41 at Cape Canaveral Space Force Station in Florida, for about a one week stay aboard the space station. The Starliner and crew will land under parachutes and an airbag-assisted landing in the western United States. This is Boeing’s second flight to the International Space Station and third Starliner flight test overall, following a second successful Orbital Flight Test, the uncrewed mission also known as OFT-2, in May 2022. 

The OFT-2 mission sits on the launchpad ahead of flight in May, 2022. This mission profile is similar to what the CFT crew will perform, albeit with humans in the loop.
Credit: An Tran

During CFT, the spacecraft and its crew will perform several flight test objectives, supporting the certification ahead of regular rotation missions for Starliner. The first test is to demonstrate performance of crew equipment from pre-launch through ascent, including suit and seat performance. During approach, rendezvous, and docking with the station, the Starliner team will assess spacecraft thruster performance for manual abort scenarios, conduct communication checkouts, test manual and automated navigation, and evaluate life support systems. Crew aboard the station will monitor the spacecraft’s approach and the Starliner crew would command any necessary aborts. By testing human in loop systems, both Boeing and NASA can verify how the spacecraft handles during operations, should human intervention ever be needed.

Starliner will autonomously dock to the forward-facing port of the Harmony module, which was vacated during a relocation maneuver by the astronauts of SpaceX Crew-8 on May 2nd. The on-station test objectives will consist of performing hatch opening and closing operations, configuring the spacecraft for its time docked to the station, and transferring emergency equipment onboard. During its stay, the crew will evaluate the spacecraft, its displays, and cargo transfer systems. Wilmore and Williams will also go inside Starliner, close the hatch, and demonstrate the spacecraft can perform as a “safe haven” in the case one is needed in the future. Visiting spacecraft can be used as safe havens in the event of a contingency aboard the space station, such as depressurization, fire, or risk of collision with orbital debris – as was seen during the Crew-3 mission. 

Starliner docked to the forward port of Harmony, taken through the window of the Crew-4 Dragon during the OFT-2 mission.
Credit: ESA/NASA/Sam Cristoforetti

Wilmore and Williams will live and work alongside the Expedition 71 crew for about a week before boarding Starliner for return to Earth. After undocking, the next flight test objective will assess manual piloting of Starliner before switching back to autonomous operations. The crew will spend approximately six hours in the spacecraft from undocking until its first landing opportunity. During re-entry to Earth’s atmosphere, the spacecraft will begin to slow down from orbital velocity at 17,500 miles per hour, and the crew could feel loads up to 3.5 g. The spacecraft’s forward heat shield will be jettisoned after re-entry, having completed its work protecting the parachute system, and two drogue and three main parachutes will further slow Starliner’s descent. The base heat shield will deploy, exposing the dual airbag system. The six primary airbags will deploy at the base of the capsule, cushioning its landing at approximately 4 mph in the western United States. Potential landing locations include two targets in the vast White Sands Missile Range, New Mexico; Willcox, Arizona; Dugway Proving Ground, Utah. Edwards Air Force Base in California is available as a contingency landing site.

CFT represents the culmination of a years-long certification process, verifying that all systems aboard the spacecraft are acceptable for flight. Boeing’s OFT 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. 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 on time 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.

Astronauts Sunita Williams and Barry Wilmore speak to the press before the rollout of their spacecraft to be mated with its launch vehicle on April 16. 2024.
Credit: Brandon Berkoff

After a lengthy analysis, Boeing and NASA leadership moved to repeat the OFT mission, with the goal of fully completing all of the necessary tests that were missed during OFT-1. 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 upcoming crewed flight test, resulting in a shuffle in the flight order and placing further limitations on the number of Atlas Vs available. 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. The mission encountered several, non mission critical hiccups with the spacecraft’s orbital maneuvering thrusters – and was ultimately declared successful by NASA and Boeing. After spending 4 days and 8 hours docked to the ISS, the spacecraft returned to earth, touching down at White Sands Missile Range on May 25, 2022.

With the crucial OFT campaign out of the way, the company could now begin to look towards their first flight of crew. As Boeing was preparing to ramp up for launch of the CFT mission 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. After nearly a year of review, and a re-test of the parachute system to further verify operational readiness, launch operations began for the teams as the various components of the spacecraft made their way to the spaceport at Kennedy Space Center. On April 16th, 2024, Calypso was rolled out of its processing facility at Kennedy Space Center for the trek to the launch pad, where it was subsequently stacked atop an Atlas V rocket. The Atlas V used for Starliner operations bears the unique N22 designator, as it does away with the fairing used on all other variants of Atlas. The crew arrived at Kennedy Space Center in their T-38 jets on Thursday, April 25 and entered their standard quarantine period – ensuring that their health remains in top condition ahead of their flight to the ISS. 

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. For Boeing, this also includes an optional fifth seat to allow participants from the commercial sector to join NASA astronauts, should any buyers choose to do so. Operational flights occur approximately once every six months for missions that last for just as long. A spacecraft notionally remains docked to the ISS during its mission, but will oftentimes change “parking spots” on station to enable arrivals at the forward port on Harmony. 

Calypso voyages to the pad at LC-41, where she will be mated to her Atlas N22 launch vehicle.
Credit: David Diebold

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. Commercial Crew is centered around the idea of dissimilar redundancy, a premise which stipulates that two providers be available for added resilience in the event that something should go wrong. Since 2020, SpaceX has been the sole US provider of missions to the ISS, while continuing to engage in contingency seat trading with the Russian space agency Roscosmos. This arrangement, while not ideal, enabled continued crew access to the ISS and ensured a 7 person team on orbit, maximizing science output of the orbiting laboratory. Through the full utilization of the Commercial Crew Program, with two US vehicles in service, NASA will see handovers between providers starting in 2025, taking a spot on the schedule known as USCV-10 should CFT be successful. As of the time of writing, Boeing is contracted to fly Starliner missions 1-6. For SpaceX, extension of their flight contracts was easy with the reusable Falcon 9 proving to be a workhorse rocket for the 2020s and beyond – but the issue is far more pressing for Boeing. After the 2022 invasion of Ukraine by Russia, ULA made the formal decision to terminate the Atlas line in 2029, citing availability of the Russian made RD-180. This left a limited stock of Atlas vehicles left for the program, with no clear answer over a successor lifter.    

The Starliner program has prospects beyond ISS in an age of commercial space, should the stations to serve come to fruition and a suitable replacement launcher be found. Blue Origin has named Boeing as one of their transportation and logistics providers for their Commercial Low Earth Orbit station Orbital Reef, alongside the Sierra Nevada Dream Chaser spaceplane. 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 as part of greater access to space provided by commercial industry. For a significant portion of the spacecraft’s development history, these capabilities have been touted as a key selling point as NASA seeks to support a more commercial model for LEO access. These plans, in recent years, have been placed on the backburner as Boeing aims to certify the spacecraft for frequent, reliable NASA-centered operations.  

With CFT on the very near horizon, both Boeing and NASA are eager to fly crews to the ISS with the true vision of the Commercial Crew Program in mind – two providers providing access and resilience to anything the world could throw at it. Now, one final step remains in the quest to fulfill this vision, running the final gauntlet of the Crewed Flight Test to deliver Butch and Suni to their home away from home on orbit. 

Edited by Scarlet Dominik

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