WASHINGTON — NASA and SpaceX have postponed the launch of a Dragon cargo mission to the International Space Station after discovering a potential propellant leak in the spacecraft’s thrusters.
In a statement in late June, NASA said the launch of the CRS-25 mission, which was scheduled for June 10, would be postponed after detecting “high vapor readings” of monomethylhydrazine (MMH) in part of the thruster. Spaceship Draco. system. The cause of the high reading is under investigation.
The Dragon spacecraft uses Draco thrusters for orbital maneuvers, including approaching and departing from the space station and deorbiting at the end of the mission. Thrusters use MMH thrusters and nitrogen tetroxide, a storable and hypergolic combination. The freighter version of Dragon lacks the more powerful SuperDraco thrusters developed by SpaceX for the Crew Dragon spacecraft abort system.
NASA said the high readings were detected when the thruster was loaded into the spacecraft, but did not say when it happened, other than that the problem was “identified over the weekend.” NASA and SpaceX officials said they met June 6 to discuss the issue “and the best way forward.”
The agency said MMH and nitrogen tetroxide propellants were offloaded from Dragon to allow engineers to investigate the problem. “Once the exact source of the elevated readings has been identified and the cause determined, joint NASA and SpaceX teams will determine and announce a new target launch date,” he said.
The Dragon will deliver more than two tons of supplies and equipment to the ISS. Among the mission’s science payloads, highlighted in a NASA briefing on June 2, are an Earth science instrument that will study mineral dust in the atmosphere, experiments to study how sutured wounds heal in microgravity and the aging immune system, and a student-developed experiment that will use biopolymers to create bricks from materials like those found in lunar and Martian regolith.
The thruster issue is the second issue to involve a Dragon spacecraft in recent weeks. NASA said May 24 that SpaceX is replacing the heat shield structure of the upcoming Crew Dragon spacecraft, which will launch in September as part of the Crew-5 mission. This heat shield failed an acceptance test earlier in May.
NASA revealed the heat shield issue in a statement that denied a published report that hypergolic thrusters leaked during the re-entry of the Crew Dragon spacecraft that flew the Ax-1 private astronaut mission in April, damaging the heat shield.
“Data associated with recent Dragon crew re-entries was normal – the system worked as expected without dispute,” the agency said last month. “There were no hypergol leaks when returning from a crewed Dragon mission or contamination with the heat shield causing excessive wear.”