Dragon docked to ISS
A cargo Dragon spacecraft docked to the International Space Station earlier this year, with several of its Draco thrusters visible. Credit: NASA

ARCADIA, Calif. — A SpaceX cargo Dragon mission to the International Space Station will now launch no earlier than July 11, a delay of more than a month after engineers identified the source of elevated hydrazine readings in the spacecraft.

In a statement late June 13, NASA said that agency officials met with SpaceX to discuss the status of the investigation into elevated vapor readings of monomethyl hydrazine (MMH) detected earlier this month after the spacecraft was fueled ahead of a launch then planned for June 10. The readings, the sign of a potential leak in the vehicle’s Draco thrusters, prompted a launch delay announced June 6.

After removing propellant from the vehicle, “SpaceX was able to narrow down the source of the issue to a Draco thruster valve inlet joint,” the agency said. “Teams will now remove the specific hardware to replace it ahead of flight.”

In the statement, NASA said it has rescheduled the launch of the CRS-25 cargo mission to no earlier than July 11. The agency said last week, before the cause of the readings had been identified, that it had rescheduled the launch for no earlier than June 28. The spacecraft will transport experiments and cargo to the station.

The Draco thrusters are used for orbital maneuvering by Dragon, including approaching and departing the station, as well as for deorbiting at the end of the mission. The thrusters use MMH and nitrogen tetroxide propellants.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...