Miguel J. Rodriguez Carrillo/AFP via Getty Images
The first crewed test flight of Boeing’s long-delayed Starliner spacecraft will not launch as planned on Saturday and could be delayed even longer as engineers investigate a stubborn helium leak in the capsule’s propulsion system.
NASA announced the latest delay to the Starliner test flight late Tuesday. After the small helium leak on the spacecraft’s service module was discovered, officials will take more time to consider how to proceed with the mission.
The space agency hasn’t described what options are on the table, but sources said they range from flying the spacecraft “as is” with a thorough understanding of the leak and assurance that it won’t become more serious in flight, to removing it the capsule takes his Atlas V rocket and takes it back to a hangar for repairs.
Theoretically, the former option could allow a launch attempt as early as next week. The latter alternative could delay the launch at least until late summer.
“The team has been in meetings for two consecutive days to evaluate flight logic, system performance and redundancy,” NASA said in a statement Tuesday evening. “There is still much work to be done in these areas, and the next possible launch opportunity is still under discussion. NASA will provide 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 compares to previous spacecraft setbacks.
Software problems prevented a pilotless test flight in 2019 and forced Boeing to conduct a second demonstration mission. Starliner was on the launch pad when pre-flight checks in 2021 discovered stuck valves in the spacecraft’s propulsion system. Boeing finally flew Starliner on a round-trip mission to the space station in May 2022. Concerns about Starliner’s parachutes and flammable tape inside the spacecraft’s crew cabin delayed the manned test flight from last summer to this year.
Boeing aims to be the second company to fly astronauts to the space station as part of NASA’s commercial crew program, following the launch of SpaceX’s crew transportation service in 2020. Assuming a smooth crewed test flight, NASA hopes to release the Starliner spacecraft for six months, with monthly rotational crew flights to the space station beginning next year.
In the doghouse
Engineers first noticed the helium leak during the first launch attempt for Starliner’s manned test flight on May 6, but managers did not consider it significant enough to abort the launch. Ultimately, another problem with a pressure control valve on the United Launch Alliance (ULA) Atlas V rocket caused officials to abandon the launch attempt.
NASA astronauts Butch Wilmore and Suni Williams were already strapped into their seats in the Starliner spacecraft on the launch pad at Cape Canaveral Space Force Station in Florida when officials ordered a halt to the countdown to May 6. Wilmore and Williams returned to their homes in Houston to await the next opportunity for Starliner launch.
ULA returned the Atlas V rocket to its hangar, where technicians replaced the defective valve in time for another launch attempt on May 17. NASA and Boeing pushed back the launch date to May 21 and then to May 25 as engineers assessed the helium leak. The Atlas V rocket and Starliner spacecraft remain at ULA’s Vertical Integration Facility awaiting the next launch opportunity.
Boeing engineers traced the leak to a flange on a single reaction control system engine in one of the Starliner service module’s four doghouse-shaped propulsion pods.
On the Starliner service module are 28 reaction control system engines – essentially small rocket engines. In orbit, these engines are used for minor course corrections and pointing the spacecraft in the correct direction. The service module has two sets of more powerful engines for larger orbital adjustments and launch-abort maneuvers.
The spacecraft’s propulsion system is pressurized with helium, an inert gas. The engines burn a mixture of toxic hydrazine and nitrogen tetroxide propellants. Helium is not flammable, so a small leak is unlikely to pose a major safety risk on the ground. However, the system requires sufficient helium gas to move propellants from their internal storage tanks to 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 unless it worsened. A Boeing spokesperson declined to provide Ars with details on the helium leak rate.
If NASA and Boeing address their concerns about the helium leak without requiring lengthy repairs, the International Space Station could allow the Starliner to dock by mid-July. After docking with the station, Wilmore and Williams will spend at least eight days at the complex before undocking and making their way to a parachute-assisted, airbag-padded landing in the southwestern United States.
After July the schedule gets messed up.
The space station has a lot going on in August with multiple crew members and cargo vehicles arriving, including a new team of astronauts on a SpaceX Dragon spacecraft and the departure of an outgoing crew on another Dragon spacecraft. There could be an additional window of time in late August or early September for Starliner to dock with the space station before SpaceX’s next cargo mission launches, which will occupy the docking port that Starliner must use. The docking port will reopen in the fall.
ULA also has other high-priority missions that it would like to launch from the same launch pad needed for the Starliner test flight. Later this summer, ULA plans to launch the U.S. Space Force’s final mission with an Atlas V rocket. ULA then plans to launch the second demonstration flight of its new Vulcan Centaur rocket – the replacement for the Atlas V – in September.