NASA and Boeing officials are set 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.
Liftoff of Boeing’s Starliner, encapsulated on a United Launch Alliance Atlas V rocket, is scheduled for 12:25 p.m. EDT (4:25 p.m. UTC). NASA Commander Butch Wilmore and Pilot Sonny Williams, both veteran astronauts, will take the Starliner spacecraft on its first crewed trip into low Earth orbit.
The first crewed flight of a new spacecraft is not an everyday occurrence. The Starliner is the sixth manned orbiting spacecraft in the history of the US space program, following SpaceX’s Mercury, Gemini, Apollo, the Space Shuttle and Crew Dragon. NASA signed a $4.2 billion contract with Boeing in 2014 to develop the Starliner, but the project has been years behind schedule and cost Boeing nearly $1.5 billion in cost overruns. SpaceX, meanwhile, won a contract at the same time as Boeing and began launching Crew Dragon astronauts four years ago this week.
Now it’s finally Starliner’s turn. A successful crew test flight will mark the beginning of six operational Starliner flights to transport astronauts to and from the International Space Station (ISS).
Assuming the test flight begins on Saturday, the spacecraft should board the ISS at 1:50 p.m. EDT (17:50 UTC) on Sunday to begin a stay of at least eight days. Once managers are satisfied that the mission has achieved all of its planned test objectives, and pending good weather conditions at the Starliner landing area in the western United States, the spacecraft will leave the station and return to Earth for a parachute landing. If the mission takes off on Saturday, the earliest nominal landing date would be Monday, June 10.
Wilmore and Williams have been here before. On May 6, the astronauts were strapped into their seats in the cockpit of the Starliner awaiting liftoff on a flight to the International Space Station. A valve failure on the Atlas V rocket prevented the 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 review and analysis, managers decided the Starliner was safe to fly as it was with the leak. The spacecraft uses helium gas to pressurize its propulsion system and push hydrazine and nitrogen tetroxide propellants from internal tanks to the capsule’s maneuvering thrusters.
“When we looked at this issue, it didn’t come down to deals,” said Mark Nappi, Boeing vice president and program manager for the Starliner. “It all came down to: Is it safe or not? And it’s safe, and that’s why we decided we can fly with what we have.”
Ground crews traced the leak to a flange on one of the four doghouse-shaped propulsion pods around the perimeter of the Starliner spacecraft’s service module. In the worst case scenario, if the condition worsened during flight, ground controllers could isolate it by closing the manifold feeding the leak. If the leak doesn’t get worse, engineers are confident they can manage it without major mission impacts.
“We looked very carefully 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 a helium conduit and lines for the spacecraft’s toxic fuel and oxidizer, making repair “problematic,” Stich said.
To safely fix the leak, which officials believe is likely caused by a faulty seal, ground crews will have to disconnect the capsule from the Atlas V rocket, return it to a hangar, drain its fuel tanks. This will likely delay the long-delayed Starliner test flight until later this year.
But the leak is relatively small and steady. “That’s about half a pound a day out of 50 pounds of total tank capacity,” Stich said.
“In our case, we have a reserve in the helium tank, and we tried to really understand that reserve and understand the worst cases and took the time to look at that data,” Stich said. “We really think we can manage that leakage, both by looking at it before launch and then, if it gets bigger in flight, we can manage it.”
