The first crew launch of Boeing’s Starliner capsule has been postponed indefinitely

The long-awaited first crewed test flight of Boeing Co.’s Starliner spacecraft will not take off as planned Saturday, and may face a longer delay as engineers evaluate a stubborn leak of helium from the capsule’s propulsion system.

NASA announced the latest delay to the Starliner test flight late Tuesday. Officials will take more time to consider their options on how to proceed with the mission after a small helium leak was discovered in the spacecraft’s service module.

The space agency did not clarify the options on the table, but sources said they ranged from flying the spacecraft “as is” with a thorough understanding of the leak and confidence that it will not become more significant during flight, to removing the capsule from its location. Atlas V missile and returned to the hangar for repair.

In theory, the first option could allow for a launch attempt next week. The latter alternative could delay the launch until at least late summer.

NASA said in a statement on Tuesday evening: “The team held meetings for two consecutive days, to evaluate the flight justification, system performance, and redundancy.” “There is still advanced work in these areas, and the next potential launch opportunity is still under discussion. NASA will share more details once we have a clearer path forward.”

Delays are nothing new for the Starliner program, but it is not yet clear how this delay will compare to previous setbacks for the spacecraft.

Software issues interrupted an unmanned test flight in 2019, forcing Boeing to fly a second test mission. The Starliner was on the launch pad when pre-flight checks revealed stuck valves in the spacecraft’s propulsion system in 2021. Boeing finally flew the Starliner on a round-trip mission to the space station in May 2022. Concerns about the Starliner’s parachutes and flammable tape inside the spacecraft delayed Crew cabin The crew test flight from last summer through this year.

Boeing aims to become the second company to transport astronauts to the space station under a contract with NASA’s Commercial Crew Program, after SpaceX’s crew transportation service begins in 2020. Assuming a smooth crewed test flight, NASA hopes to evacuate the Starliner spacecraft for six people. Month-long crew rotation flights to the space station begin next year.

In the dog house

Engineers first noticed a helium leak during the first launch attempt of the Starliner spacecraft’s crewed test flight on May 6, but managers did not consider it significant enough to halt the launch. Ultimately, a separate problem with a pressure-regulating valve on the United Launch Alliance (ULA) spacecraft’s Atlas V rocket prompted officials to cancel the launch attempt.

NASA astronauts Butch Wilmore and Sonny Williams were already strapped into their seats inside the Starliner spacecraft on the launch pad at Cape Canaveral Space Force Station in Florida, when officials ordered the countdown halted on May 6. Wilmore and Williams returned to their homes in Houston awaiting the opportunity to launch the next Starliner.

ULA returned the Atlas V rocket to its hangar, where technicians replaced the faulty valve in time for another launch attempt on May 17. NASA and Boeing pushed back the launch date to May 21, then to May 25, as engineers evaluated a helium leak. The Atlas V rocket and Starliner spacecraft remain inside ULA’s Vertical Integration Facility awaiting the next launch opportunity.

Boeing engineers traced the leak to a flange on a single reaction control system actuator in one of four doghouse-shaped thrust chambers in the Starliner’s service module.

There are 28 reaction control propulsion systems—essentially small rocket motors—in the Starliner service module. In orbit, these thrusters are used to make slight corrections in the spacecraft’s trajectory and point it in the right direction. The service module contains two sets of more powerful engines to perform larger orbital adjustments and launch abort maneuvers.

The spacecraft’s propulsion system is pressurized using helium, an inert gas. The thrusters burn a toxic propellant mixture of hydrazine and nitrogen tetroxide. Helium is non-flammable, so even a small leak is unlikely to pose a major safety issue on Earth. However, the system needs enough helium gas to push propellant from the internal storage tanks into the Starliner’s engines.

In a statement last week, NASA described the helium leak as “stable” and said it would not pose a risk to the Starliner mission if it did not worsen. A Boeing spokesperson declined to provide Ars with any details about the helium leak rate.

If NASA and Boeing can resolve their concerns about helium leaks without requiring lengthy repairs, the International Space Station could accommodate docking of a Starliner vehicle during part of July. After docking at the station, Willmore and Williams will spend at least eight days at the complex before separating to head for a parachute-assisted, air-cushioned landing in the southwestern United States.

After July, the schedule became chaotic.

The space station has a busy roster of several visiting crew members and cargo vehicles in August, including the arrival of a new team of astronauts aboard the SpaceX Dragon spacecraft, and the departure of a departing crew aboard another Dragon. There may be an additional window for Starliner to dock with the space station in late August or early September before SpaceX’s next cargo mission launches, which will occupy the docking port that Starliner needs to use. The docking port opens again in the fall.

ULA also has other high-priority missions it would like to launch from the same platform needed for the Starliner test flight. Later this summer, ULA plans to launch the final mission of the U.S. Space Force using an Atlas V rocket. Next, ULA aims to launch the second test flight of its new Vulcan Centaur rocket — the replacement for the Atlas V rocket — next September.