WASHINGTON — NASA and SpaceX are moving ahead with the launch of a seventh crew rotation mission to the International Space Station this week, remaining vigilant about crewed launches even as they become more routine.
NASA said Aug. 21 it completed a flight readiness review for the Crew-7 mission, approving plans for a launch at 3:49 a.m. Eastern Aug. 25 from Launch Complex 39A at the Kennedy Space Center in Florida. A launch that day would set up a docking of the Crew Dragon spacecraft Endurance with the station at 2:02 a.m. Eastern Aug. 26.
The Crew-7 mission is commanded by NASA astronaut Jasmin Moghbeli with European Space Agency astronaut Andreas Mogensen as pilot. Satoshi Furukawa, an astronaut from the Japanese space agency JAXA, and Roscosmos cosmonaut Konstantin Borisov will be mission specialists. The four will spend about six months on the station.
Officials said at a briefing that they cleared all issues associated with the mission during the nearly seven-hour review. That included concerns about corrosion seen on isolation valves in a cargo Dragon spacecraft launched to the station in June. The corrosion prevented the valves from operating, but those valves, used only in the event of a propellant leak in a thruster, were not needed on that CRS-28 mission.
Steve Stich, NASA commercial crew program manager, said SpaceX replaced some of the valve components on Endurance and that engineers have a “good rationale” for the remaining valves on the spacecraft. “We wanted to understand it very thoroughly, so we spent the last month or so looking at data,” he said, including testing and other analysis of valves by both SpaceX and NASA.
The corrosion appears to be caused by propellant vapors leaking through seals and reacting with ambient moisture, creating acid. The materials used in the valves are designed to resist corrosion, he said, but with enough vapor and moisture some corrosion will develop.
That drew parallels to Boeing’s CST-100 Starliner, which suffered severe corrosion of valves in its propulsion system that prevented the valves from operating. That postponed the launch of its second uncrewed test flight by more than nine months, from August 2021 to May 2022.
The corrosion mechanism is “somewhat similar” between the two spacecraft, Stich said, although differences in materials result in different kinds of corrosion.
“We learned quite a bit from the investigation we did on Starliner and it probably helped us to get to the root cause a little bit faster,” he said. That included the importance of having a purge system that removes vapors from the vicinity of the valves to prevent corrosion. “I think we’re learning a little bit about capsules and valves between the two different vehicles, Starliner and Dragon.”
Stich said the review also resolved another minor issue seen during the return of another Crew Dragon spacecraft in March at the end of the Crew-5 mission, when one of the drogue parachutes inflated several seconds slower than the other. Separate work by NASA and SpaceX to model parachute dynamics led them to clear the issue, he said.
Both Stich and Bill Gerstenmaier, vice president of build and flight reliability at SpaceX, said the valve and parachute analyses were examples of how they remained focused on safety for crewed missions even as such missions become more routine. Crew-7 will be SpaceX’s 11th launch with astronauts on board, a figure that includes the Demo-2 test flight in 2020 and three private astronaut missions.
“We know the importance of flying crew and the trust that the crew puts in us,” said Gerstenmaier, a former NASA official who led the agency’s human spaceflight activities for several years. “We treat that extremely seriously as a company.”
That focus continues even as SpaceX’s overall launch activity grows. A Falcon 9 launch of 21 Starlink satellites from Vandenberg Space Force Base in California early Aug. 22 was the 54th launch of that vehicle so far this year, and the 58th launch for SpaceX overall, counting three Falcon Heavy launches and the Starship/Super Heavy test flight in April. That approaches the 61 launches that SpaceX conducted in all of 2022.
“There’s an advantage of flying a lot,” Gerstenmaier said, including both a better understanding of the hardware and the ability to test changes on other launches before incorporating them on crewed missions. He noted that Starlink launches use a higher thrust profile, which provides more margin for crewed missions.
Starlink launches “really help us out,” Stich said, by testing changes that can later be incorporated into crewed flights. “We can watch that new component or the change in the component, how it flies in the flight environment, and then come back and look at the data and get comfortable with it for a crewed flight.”