NASA and Boeing officials are preparing for a second attempt to launch the first crewed test flight of the Starliner spacecraft on Saturday from the Cape Canaveral Space Force Station in Florida.
The Boeing Starliner, sitting atop a United Launch Alliance Atlas V rocket, is scheduled for launch at 12:25 p.m. EDT (4:25 p.m. UTC). NASA Commander Butch Wilmore and Pilot Suni Williams, both veteran astronauts, will take the Starliner spacecraft on its first trip into low Earth orbit with a crew on board.
The first crewed flight of a new spacecraft is not an everyday event. Starliner is the sixth crewed orbiter-class spacecraft in the history of the US space program, following SpaceX’s Mercury, Gemini, Apollo, Space Shuttle and Crew Dragon. NASA signed a $4.2 billion contract with Boeing in 2014 to develop the Starliner, but the project is running years behind schedule and has cost Boeing nearly $1.5 billion in cost overruns. SpaceX, meanwhile, won the contract at the same time as Boeing and began launching astronauts on Crew Dragon four years ago this week.
Now it’s finally Starliner’s turn. A successful crew test flight would pave the way for six operational Starliner flights to ferry astronauts to and from the International Space Station (ISS).
Assuming the test flight lifts off from Earth on Saturday, the spacecraft is scheduled to touch down on the ISS at 1:50 p.m. EDT (5:50 p.m. UTC) Sunday to begin a stay of at least eight days. Once managers are satisfied the mission has achieved all planned test objectives, and pending good weather conditions at the Starliner landing zone in the western United States, the spacecraft will leave the station and return to Earth for a parachute landing. If the mission launches on Saturday, the earliest nominal landing date would be Monday, June 10.
Wilmore and Williams were already here. On May 6, the astronauts were strapped into their seats in the cockpit of the Starliner, awaiting liftoff to the International Space Station. A valve malfunction on the Atlas V rocket prevented launch that day, and officials subsequently discovered a helium leak in the Starliner’s service module, delaying the mission until this weekend.
Flying as it is
After weeks of inspections and analysis, managers determined that the Starliner could safely fly as is with the leak. The spacecraft uses helium to pressurize its propulsion system and push hydrazine and nitrous oxide propellants from internal tanks into the capsule’s maneuvering nozzles.
“When we looked at this issue, it wasn’t about the stores,” said Mark Nappi, Boeing’s vice president and program manager for the Starliner. “It came down to: Is it safe or not? And it is safe, and that’s why we decided we can fly with what we have.”
Ground teams traced the leak to a flange on one of the four doghouse-shaped propulsion modules around the perimeter of the Starliner spacecraft’s service module. In the worst-case scenario, if the condition worsened during the flight, ground controllers could isolate it by closing off the pipeline supplying the leak. If the leak doesn’t get worse, engineers are confident they can pull it off without major mission impact.
“We were really looking at what our options were with this particular flange,” said Steve Stich, NASA’s commercial crew program manager, who oversees the agency’s contract with Boeing. The flange has helium lines and lines for the spacecraft’s toxic fuel and oxidizer, making repair “problematic,” Stich said.
To safely repair the leak, which officials believe is likely caused by a faulty seal, ground teams would have to detach the capsule from the Atlas V rocket, take it back to the hangar and drain its fuel tanks. That would likely push the long-delayed Starliner test flight to later this year.
However, the leakage is relatively small and stable. “It’s about a pound a day out of 50 pounds of total capacity in the tank,” Stich said.
“In our case, we have a reserve in the helium tank, and we tried really hard to understand that reserve and understand the worst cases, and we took the time to go through that data,” Stich said. we can manage that leak, both by looking at it before takeoff and if it gets bigger in flight, we could manage it.”