SpaceX spent ‘a month or so’ battling one key issue before its latest Crew Dragon launch: Sticky valves in life support
The Crew Dragon spacecraft launched by SpaceX yesterday successfully docked with the International Space Station as its crew of four astronauts began their six-month mission.
The docking took place about 9:16 EST while the two spacecrafts were orbiting above Australia, SpaceX officials said in a streamed broadcast.
Called Crew-7, this journey marks SpaceX’s seventh operational human spaceflight mission to the space station under NASA’s Commercial Crew Program. It’s also the eleventh time SpaceX has launched humans into orbit.
It comes as Boeing Co. — NASA’s other Commercial Crew provider — works to get its long-delayed Starliner spacecraft ready to fly next year. Delays have raised concerns about NASA’s goal of having multiple lifelines to the ISS.
Led by NASA astronaut and commander Jasmin Moghbeli, Saturday’s crew includes Danish astronaut Andreas Mogensen of the European Space Agency, Satoshi Furukawa from the Japan Aerospace Exploration Agency and Russian cosmonaut Konstantin Borisov. The crew are slated to stay on board before returning in early 2024.
The four astronauts of SpaceX’s Crew-6 mission, who have been living on the ISS since March, will spend the next week welcoming the Crew-7 astronauts before returning to Earth in their own Crew Dragon capsule, tentatively scheduled for Sept. 1.
Sticky Valves
NASA and SpaceX had originally hoped to launch Friday, but chose to call off liftoff hours prior in order to take more time to analyze the Dragon’s life-support system.
The launch of Crew-7 comes after SpaceX disclosed issues with sticky valves on a previous Dragon flight — an issue that could have been a problem for Saturday’s flight. During a cargo resupply mission to the space station in June, SpaceX noticed that a particular valve in the Dragon cargo capsule had been stuck open throughout the flight. The valve is meant to remain open and only needs to close if there is a propellant leak, so it didn’t pose much of a problem. But if there had been a leak, SpaceX would have had a much bigger issue.
After that mission ended and the Dragon capsule returned to Earth, SpaceX took a look at the problematic valve and found evidence of corrosion after sending parts of it for testing. That triggered the company to look at valves throughout the Dragon fleet.
“We wanted to understand it very thoroughly, so we spent the last month or so looking at data, and SpaceX did testing of different valves all across the country,” Steve Stich, the manager of the Commercial Crew Program at NASA, said during a press conference ahead of flight.
Ultimately, the company pinpointed the source of the problem. Some of the propellant the Dragon spacecraft uses can mix with too much moisture in the air, creating acid that corrodes the valve.
SpaceX said that further testing revealed a fix for the sticky valves. “We figured out there’s a way that if we actually power the valve a little bit longer, we can actually drive through this corrosion and get back functionality to the valve,” Bill Gerstenmaier, vice president of build and flight reliability at SpaceX, said during the press conference. The company is also incorporating dry nitrogen air to purge excess moisture from the system, a solution that Boeing used for Starliner.
SpaceX also opted to replace some of the valves on multiple Dragon spacecraft — including some of the valves on Crew-7’s Dragon.
SpaceX and NASA are still thinking of ways to fix the corrosion in the long-term, though, as the goal is to fly the Crew Dragon vehicles to space at least five times each.