Boeing’s Starliner spaceship was recalled to the factory because of sticky valves.
The Starliner is set to bring NASA astronauts to and from the International Space Station and has been years behind schedule. Past problems with the spacecraft have added financial losses to Boeing’s balance sheet.
Friday’s announcement means the capsule will be lifted off the Atlas-5 rocket at Cape Canaveral Space Force Station in Florida and returned to the Boeing factory near NASA’s Kennedy Space Center. The planned unmanned demonstration flight, which should be carried out, will be delayed by at least two months and possibly until next year. And that will further postpone Boeing’s maiden flight with astronauts on board.
“This is obviously a disappointing day,” said Kathy Lueders, NASA’s assistant administrator for human exploration and operations, during a conference call. “But I would like to emphasize that this is another example of why these demo missions are so very important to us.”
A similar spaceship, Crew Dragon, built by SpaceX for NASA, has brought astronauts to the space station three times since last year and could put two more crews into orbit before the end of 2021.
Starliner was originally scheduled to take off for the space station on July 30 with no astronauts on board – a replay of an earlier flight to check the spacecraft’s systems – and then return to Earth about a week later. But that launch date was postponed after a mishap on the space station when a newly docked Russian module, Nauka, accidentally fired its engines, causing the station to spin.
The next opportunity to launch was August 3rd, and the rocket with Starliner on top was on the launch pad the night before when a severe thunderstorm rolled through. During the next day’s countdown, 13 valves on Starliner’s propulsion system did not open and the start was aborted.
In the days of troubleshooting that followed, engineers managed to get nine of the 13 valves working, but four got stuck.
“If we could free them all, we would be in good working order,” said John Vollmer, Boeing’s vice president and program manager for Starliner. “We turned for that, but since we didn’t get all of the valves, we decided that we were just outside the runway and had to go back to the factory.”
Mr Vollmer said the problem occurred with 24 valves that control the flow of nitrogen tetroxide, a propellant used by Starliner engines. Some of the nitrogen tetroxide appears to have passed through Teflon seals and, on the other hand, interacts with moisture to produce nitric acid, Mr Vollmer said.
“This nitric acid led to a certain amount of corrosion which led to the static friction of these valves,” said Mr. Vollmer.
Mr Vollmer said the valves have remained unchanged in design since Starliner first launched in December 2019. That flight was affected by serious software bugs preventing it from reaching the space station, which led Boeing and NASA to decide that a fix was needed before confirming that Starliner is ready to carry astronauts. But the hardware, including the valves, worked almost flawlessly during the 2019 shortened trip.
“We haven’t seen this problem in the past and we see it now,” said Mr Vollmer. He said the engineers now had to figure out what was different – maybe the weather conditions, including the thunderstorm drenching, maybe something in the manufacture of the valves. He said he didn’t think rain got directly into the valves.
The Starliner launch now follows the launch of NASA’s Lucy spacecraft, which is supposed to examine Trojan asteroids that are gravitationally trapped in the orbit of Jupiter. The alignment of the planets dictates that Lucy must take off during a three-week period from mid-October to early November. If it misses this window, the next opportunity would be next year.
Once Starliner is back at Boeing’s Kennedy Space Center facility, the first thing the engineers will do is figure out what to disassemble to fix the valves. Mr Vollmer said it was too early to estimate how long the fixes would take or when the spacecraft would return to the launch pad.
“It’s probably too early to say if it’s this year or not,” he said. “I would definitely hope as soon as possible. And if we could fly this year it would be fantastic. “