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SpaceX's next cargo launch to space station delayed due to odd propellant reading

 SpaceX’s Cargo Dragon spacecraft is lifted aboard a recovery vessel after splashing down in the Atlantic Ocean off the coast of Florida on Thursday, Sept. 30, 2021.
SpaceX’s Cargo Dragon spacecraft is lifted aboard a recovery vessel after splashing down in the Atlantic Ocean off the coast of Florida on Thursday, Sept. 30, 2021. (Image credit: SpaceX)

SpaceX's next cargo mission to the International Space Station won't launch this week after all.

The robotic flight, called CRS-25, will send a SpaceX Dragon capsule toward the orbiting lab atop a Falcon 9 rocket from NASA's Kennedy Space Center in Florida. The liftoff had been scheduled for Friday (June 10), but that's not going to happen.

"NASA and SpaceX are standing down from this week’s Falcon 9 launch of the CRS-25 cargo mission to the International Space Station," NASA officials wrote in an emailed statement this afternoon (June 6). "Officials from NASA and SpaceX met today to discuss an issue identified over the weekend and the best path forward."

SpaceX's Dragon: First private spacecraft to reach the space station

That issue involves hydrazine, the propellant used by Dragon's Draco thrusters. While fueling Dragon up, technicians measured elevated vapor readings of hydrazine in one part of the Draco system, the NASA statement explained.

"The propellant and oxidizer have been offloaded from that region to support further inspections and testing," the statement added. "Once the exact source of the elevated readings is identified and cause is determined, the joint NASA and SpaceX teams will determine and announce a new target launch date."

As its name suggests, CRS-25 will be the 25th robotic resupply run that SpaceX launches to the International Space Station for NASA. The mission will be the third for this particular Dragon, which also launched on cargo missions to the orbiting lab in December 2020 and August 2021.

A SpaceX Dragon is already docked to the orbiting lab — the capsule named Freedom, which carried four astronauts to the station in late April for a six-month stay. SpaceX holds a separate contract with NASA's Commercial Crew Program to conduct such astronaut missions and has already launched five of them to date, counting a crewed demonstration flight in May 2020.

Mike Wall is the author of "Out There (opens in new tab)" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) or on Facebook (opens in new tab).  

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Michael Wall is a Senior Space Writer with Space.com (opens in new tab) and joined the team in 2010. He primarily covers exoplanets, spaceflight and military space, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.