Miguel J. Rodriguez Carrillo/AFP via Getty Images
The first test flight of Boeing’s long-delayed crewed Starliner spacecraft will not take off as scheduled on Saturday and may face a longer delay as engineers evaluate a stubborn helium leak from the capsule’s propulsion system.
NASA announced the latest delay to the Starliner test flight late Tuesday. Officials will have more time to consider their options for continuing the mission after discovering a small helium leak on the spacecraft’s service module.
The space agency did not describe 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 making sure it won’t rise during flight, to removing the capsule from its Atlas V rocket and taking it her back to the hangar for repairs.
In theory, the first option could allow an attempt to launch as early as next week. The second alternative could delay the start until at least the end of the summer.
“The team is meeting for two consecutive days to evaluate the flight rationale, system performance and redundancy,” NASA said in a statement Tuesday evening. “These areas are still being worked on and other possible launch opportunities are still being discussed. NASA will share more details once we have a clearer path forward.”
Delays are nothing new to the Starliner program, but it’s not yet clear how this delay will compare to the spacecraft’s previous setbacks.
Software problems aborted an unmanned test flight in 2019, forcing Boeing to fly a second demonstration mission. The Starliner was on the launch pad when preflight checks revealed stuck valves in the spacecraft’s propulsion system in 2021. Boeing eventually flew the Starliner on a return mission to the space station in May 2022. Concerns about the Starliner’s parachutes and flammable tape inside the spacecraft’s crew cabin delayed the test manned flights from last summer to this year.
Boeing aims to become the second company to fly astronauts to the space station under a contract with NASA’s Commercial Crew Program, after SpaceX launches its crew transport service in 2020. Assuming a smooth crewed test flight, NASA hopes to release the spacecraft Starliner for six years. monthly crewed rotation flights to the space station beginning next year.
In the doghouse
Engineers first noticed a helium leak during the first launch attempt for the Starliner crewed test flight on May 6, but managers did not consider it significant enough to abort the launch. Finally, a separate problem with a pressure control valve on the United Launch Alliance (ULA) spacecraft’s Atlas V rocket prompted officials to scrap the launch attempt.
NASA astronauts Butch Wilmore and Suni 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 a halt to the May 6 countdown. Wilmore and Williams returned to their homes in Houston to wait for another opportunity to launch the 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 moved the launch date to May 21 and then to May 25 as engineers evaluated the helium leak. The Atlas V rocket and Starliner spacecraft remain inside ULA’s Vertical Integration Facility to await the next opportunity to launch.
Boeing engineers traced the leak to a flange on a single reaction control system in one of the four doghouse-shaped propulsion modules on the Starliner service module.
On the Starliner’s service module are 28 reaction control system thrusters—essentially small rocket engines. In orbit, these thrusters are used to make minor course corrections and point the spacecraft in the right direction. The service module has two sets of more powerful engines for larger orbit adjustments and launch abort maneuvers.
The spacecraft’s propulsion system is pressurized using helium, an inert gas. The jets burn a mixture of poisonous hydrazine and nitrogen oxide as propellants. Helium is not flammable, so a small leak is unlikely to be a major safety concern on the ground. However, the system needs enough helium to push the propellants from their internal reservoirs into the Starliner’s thrusters.
In a statement last week, NASA described the helium leak as “stable” and said that unless it worsened, it would not pose a risk to the Starliner mission. A Boeing spokesman declined to provide Ars with any details on the extent of the helium leak.
If NASA and Boeing resolve their helium leak concerns without requiring lengthy repairs, the International Space Station could accommodate Starliner docking by part of July. After landing on the station, Wilmore and Williams will spend at least eight days in the complex before detaching and heading for a parachute and airbag landing in the southwestern United States.
After July, the schedule gets messy.
The space station has been busy with numerous crew and cargo vehicles in August, including the arrival of a new team of astronauts on a SpaceX Dragon spacecraft and the departure of an outgoing crew on another Dragon. There may be another window for the Starliner to dock with the space station in late August or early September before the next SpaceX cargo mission launches to occupy the docking port the Starliner needs to use. The docking port will reopen in the fall.
ULA also has other high-priority missions it would like to launch from the same pad needed for the Starliner test flight. Later this summer, ULA plans to launch the last US Space Force mission using an Atlas V rocket. After that, ULA aims to launch a second demonstration flight of its new Vulcan Centaur rocket — the replacement for the Atlas V — as soon as September.