WASHINGTON — NASA and SpaceX are moving forward with launching the seventh crew rotation mission to the International Space Station this week, and remain vigilant about crewed launches even as they become more routine.
NASA said on Aug. 21 that it had completed a flight readiness review for the Crew-7 mission, and approved plans for launch at 3:49 a.m. EDT on Aug. 25 from Launch Complex 39A at Kennedy Space Center in Florida. Launching that day will dock the Crew Dragon Endurance spacecraft with the station at 2:02 a.m. EDT on Aug. 26.
The Crew-7 mission will be led by NASA astronaut Jasmine Mokbeli and 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 specialists on the mission. The four will spend about six months at the station.
Officials told a news conference that they had settled all issues related to the mission during the review, which lasted nearly seven hours. This included concerns about corrosion seen on isolation valves on the Dragon cargo spacecraft that was launched to the station in June. Corrosion prevented the valves from working, but those valves, which are only used in the event of a propellant leak in the thruster, were not needed on the CRS-28 mission.
Steve Stitch, NASA’s commercial crew program manager, said SpaceX has replaced some valve components on the Endurance spacecraft, and that engineers have a “good rationale” for the remaining valves on the spacecraft. “We wanted to understand it very comprehensively, so we’ve spent the last month or so looking at the data,” he said, including tests and other analyzes of the valves by both SpaceX and NASA.
The corrosion appears to be caused by fuel vapors escaping through the seals and reacting with ambient moisture, resulting in acid formation. He added that the materials used in the valves are designed to resist corrosion, but with enough steam and moisture, some corrosion may develop.
This drew similarities to the Boeing CST-100 Starliner, which suffered severe valve wear in its propulsion system that prevented the valves from working. This led to the launch of its second uncrewed test flight being delayed by more than nine months, from August 2021 to May 2022.
Stitch said the wear mechanism is “fairly similar” between the two spacecraft, although the differences in materials result in different types of wear.
“We’ve learned a lot from our Starliner investigation, and it may have helped us get to the root cause a little faster,” he said. This included the importance of a purge system that removed vapors from around the valves to prevent corrosion. “I think we’re learning a little bit about the capsules and valves that are in between the two different spacecraft, Starliner and Dragon.”
The revision also resolved another minor issue seen during the return of another Crew Dragon spacecraft in March at the end of the Crew-5 mission, Stitch said, when one decoy parachute inflated several seconds slower than the other. He said separate work by NASA and SpaceX modeling parachute dynamics led them to solve the problem.
Both Stich and Bill Gerstenmaier, vice president of construction and flight reliability at SpaceX, said the valve and parachute analyzes were examples of how the focus remains on the safety of crewed missions even as such missions become more routine. Crew-7 will be SpaceX’s 11th crewy Launches with astronauts on board, a number that includes the Demo-2 test flight in 2020 and three private astronaut missions.
“We know the importance of the flight crew and the trust that the crew places in us,” said Gerstenmaier, a former NASA official who led the agency’s manned spaceflight activities for several years. “We take that very seriously as a company.”
And that focus continues even as SpaceX’s overall launch activity grows. The Falcon 9 launch of 21 Starlink satellites from Vandenberg Space Force Base in California early Aug. 22 was the 54th launch.y The launch of that car so far this year, 58y SpaceX launches overall, including three Falcon Heavy launches and the Starship/Super Heavy test flight in April. That approaches the 61 launches SpaceX has conducted in all of 2022.
“There’s a lot of advantage to flying,” Gerstenmaier said, including a better understanding of the hardware and the ability to test changes on other launches before integrating them into manned missions. He noted that Starlink launches use a higher profile, which provides more margin for manned missions.
The launch of Starlink “really helps us,” Stitch said, by testing changes that can later be incorporated into manned flights. “We can watch this new component or change in component, how it flies in the flight environment, and then go back and look at the data and get used to it in manned flight.”