What to Know About Boeing Starliner’s First Crewed Test Flight

Boeing’s CST-100 Starliner, a semireusable vessel to the ISS that has been marred by nearly a decade of delays, will finally make its first crewed flight test on Monday, barring any further hiccups. Boeing on Friday confirmed that NASA gave Starliner the “go to proceed.”

If the mission—intended to be Starliner’s final test flight—is successful, NASA will work to certify the spacecraft for routine, six-month crew rotation missions to the space station, beginning with Starliner-1, scheduled for 2025. Starliner’s crew capsule is designed to be reusable over 10 missions.

Commercial Crew is one of the linchpins of U.S. space exploration efforts. The program—a public-private partnership between NASA and companies such as Boeing, SpaceX, and Blue Origin—transports and swaps out the astronaut crews responsible for critical research on the orbital laboratory.

Used by astronauts and private companies from around the world, the space station is the only facility that allows researchers to investigate the effects of long duration spaceflight as NASA gears up for future missions to the moon, Mars, and beyond.

Since crew rotation missions began in 2020, all eight missions—including Crew-8, which is still in progress—have been facilitated by SpaceX’s Crew Dragon. The missions have also used the company’s Falcon 9 launch vehicle.

Boeing—which since 2014 has battled SpaceX for supremacy in the commercial crew program—has yet to launch a crewed flight of its Starliner, which NASA views as a redundant but important alternative to Crew Dragon. But the manufacturer on Monday has a chance to throw its hat in the ring.

“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 said in a mission profile on its website.

A successful crewed flight test would represent the final barrier to the start of Boeing’s commercial contract with NASA, under which the partners are obligated to complete six crew rotation missions. These would represent the manufacturer’s first commercial human spaceflight missions. SpaceX, so far, has flown astronauts to the space station 11 times.

Commercial Crew is NASA’s effort to transport astronauts to the ISS from American soil, using U.S.-built rockets and spacecraft. By involving private companies such as Boeing, a rarity for the agency in years past, the idea was to reduce costs and complexity while keeping missions safe and on schedule.

Boeing unveiled the concept for the CST-100 Starliner—with CST standing for Crew Space Transportation and 100 denoting the Kármán Line, a boundary 100 kilometers above the Earth informally considered to be the edge of space—in 2010. The manufacturer claimed the spacecraft could be operational within five years.

That prediction did not come to fruition. By 2014, NASA had narrowed down its search for a reusable Commercial Crew capsule to two candidates: Starliner and SpaceX’s Crew Dragon.

Each company was awarded billions of dollars to build and certify an aircraft by 2017, the year they were expected to be ready for a first crewed flight test. Boeing’s $4.2 billion contract includes six service missions plus uncrewed and crewed test flights to the space station.

Neither company met its deadline. But Crew Dragon made its first flight with astronauts in 2020. The same can not be said for the Starliner program, which for nearly a decade has been bogged down by delays.

The first uncrewed Starliner Orbital Test Flight Mission, scheduled for 2017, was delayed three times to 2019. Half an hour into that flight, an anomaly forced NASA to abort a planned docking with the space station. Though the mission to the orbital laboratory was scrapped, the spacecraft was safely recovered.

A second uncrewed orbital test flight, OFT-2, was also delayed more than a year due to valve problems late in the initial countdown. It eventually launched in 2022, reaching the ISS for the first time and meeting all mission objectives.

The prelude to Starliner’s first crewed test flight sounds like a familiar tune. The mission was pushed back several times in 2023, culminating in an indefinite delay caused by a pair of issues discovered just weeks before a planned launch in July.

All told, the program has overrun planned costs by $1.5 billion. According to a NASA Office of the Inspector General report, the space agency committed to additional flights and payments not specified in its original contract, in a bid to keep Boeing as a contractor.

The delays to Starliner have forced NASA to put all of its eggs in SpaceX’s basket, jeopardizing Commercial Crew missions should Crew Dragon—which so far has proven reliable—experience issues. But with the agency giving its all clear last week, the long-awaited rocket spacecraft appears set to finally make its debut.

Starliner was designed and built by Boeing with the help of more than 425 suppliers. Early missions, including next week’s planned flight, will be launched by United Launch Alliance’s Atlas V launch vehicle. But the spacecraft is billed as “launch vehicle agnostic,” compatible with vehicles in the medium-lift launch class.

Starliner’s unique weldless structure was devised with reusability in mind. Its service modules are expendable, but its crew module can be reused up to 10 times, according to Boeing. The crew module can fit seven crewmembers, but NASA missions will include four or five astronauts.

Combined, the crew and service modules have 40 reaction control system thrusters, which aid in control and steering. While the vehicle is designed to be autonomous, Boeing has trained the crew to be able to take over.

The service module has an additional 20 orbital maneuvering and attitude control thrusters and four launch abort engines, which, combined with a pusher abort system, provide an escape route in the case of emergency during launch or ascent. Stacked on top of Atlas V, the spacecraft stands just over 170 feet.

Commander Barry “Butch” Wilmore and Pilot Sunita “Suni” Williams will command next week’s planned mission. Both are experienced NASA astronauts with multiple spaceflights in the books. During the crewed test flight, Wilmore and Williams will be the first to launch on Starliner and Atlas V and manually control Starliner.

The astronauts’ goal will be to validate the transportation system, including the launch pad, rocket, spacecraft, and in-orbit capabilities, for future missions. 

Before, during, and after their weeklong stay on the space station, the crew will perform an array of tests designed to support the spacecraft’s certification. These include evaluations of equipment such as suits and seats from prelaunch through ascent, as well as assessments of communications, manual and automated navigation, life support systems, and thrusters while aboard the orbital lab.

Boeing has been “tasked with operating the entire mission,” including launch, in-orbit operations, landing, recovery and refurbishment. The company is also responsible for crew training, mission planning, spacecraft and launch vehicle assembly, and testing and integration.

Starliner arrived at Cape Canaveral Space Force Station in Florida on April 16, where it will launch from historic Space Launch Complex-41. To this point, the launch pad has only hosted uncrewed spacecraft. The spacecraft has already been stacked, with crew preparations well underway.

About 15 minutes into the mission, the Starliner capsule will separate from the booster. Orbital maneuvering and attitude control thrusters will kick in about 30 minutes in, performing an engine burn to align it in orbit and start the approximately daylong sojourn to the space station.

Cameras onboard the capsule will pick out the moving laboratory from among a sea of fixed stars as it approaches to within a few hundred feet over the following few hours. Once flight controllers give the all clear, Starliner will approach and dock autonomously with one of two Boeing-built docking adapters—another critical test.

NASA will provide continuous coverage leading up to the docking through the opening of the hatch. On Thursday, four crewmembers already aboard the space station will relocate a Crew Dragon capsule to a different docking port, making way for the SpaceX rival’s alternative.

After spending a few days evaluating the spacecraft and its systems, Wilmore and Williams will return to Starliner, which will slowly undock from the space station and position itself over the Pacific Ocean. The service module will slow it from orbital speeds of about 17,500 mph as the crew module detaches. It will then accelerate back to Earth into a parachute landing in the Western U.S., touching down at just 4 mph.

Starliner’s first crewed test flight has plenty of implications for Boeing, NASA, and U.S. ambitions in space more broadly.

On the commercial side, failure could deal a blow to the aerospace giant, which is under contract for six NASA service missions following the flight. The company also has ambitions to attract other customers, such as Jeff Bezos’ Blue Origin, describing NASA as Starliner’s “anchor customer.”

The test flight comes as Boeing rival SpaceX continues to thrive. Before Boeing completes its first crewed mission to the space station, its rival has already completed 11 such missions—eight crew rotation missions and three private astronaut missions with customer Axiom Space—and is preparing to fly astronauts to the moon on NASA’s Artemis III.

In addition, Boeing plans to sell the extra fifth seat on its NASA missions to private and commercial- or government-sponsored astronauts. Any ambitions for private commercial spaceflight will depend on next week’s mission.

NASA would also suffer from another setback to Starliner. The space agency hopes for the space station to be continuously crewed as it uses the orbital laboratory to explore future missions to more distant destinations, such as the moon or Mars. At the moment, it is too reliant on SpaceX.

“Our hearts and souls are in this spacecraft, and a little part of us will be lifting off with Butch and Suni,” said Dana Hutcherson, deputy manager of NASA Commercial Crew and a 13-year veteran of the program.

NASA envisions visiting spacecraft such as Starliner being used as “safe havens” in the event of a contingency aboard the space station, such as depressurization, fire, or potential collision.

One such contingency took place in December 2022, when the Soyuz MS-22 capsule that transported NASA astronaut Frank Rubio to the space station sprung a coolant leak, stranding Rubio and two Roscosmos cosmonauts in orbit for months. Rubio’s 355 consecutive days aboard the ISS—his first stint in space—are now a NASA spaceflight record.

SpaceX has been a reliable partner for NASA, having not suffered an incident in service thus far. But the agency wants a contingency plan. For example, in Rubio’s case, NASA was prepared to get its astronaut home in an extra seat on a scheduled Crew Dragon launch. The backup spacecraft was not needed, but it could have rescued Rubio had Roscosmos not delivered a replacement Soyuz in time.

Boeing is also developing launch vehicles for planned NASA lunar landings during Artemis II and Artemis III. Starliner is further intended to transport personnel to the Orbital Reef, a new space station under development by Blue Origin in partnership with NASA.

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