WASHINGTON — A SpaceX Cargo Dragon spacecraft is en route to the International Space Station after a July 14 launch that was delayed more than a month by a hydrazine leak on the spacecraft.
A Falcon 9 lifted off from Kennedy Space Center launch complex 39A at 8:44 p.m. Eastern and put the Dragon into low Earth orbit 12 minutes later. The spacecraft is expected to dock at the station at approximately 11:20 a.m. on July 16.
The Falcon 9’s first stage landed on a drone ship in the Atlantic Ocean seven and a half minutes after launch. The stage completed its fifth flight, having previously launched the Crew-3, Crew-4 and CRS-22 missions for NASA and the Turksat 5B communications satellite. The launch this year was the 30th so far for SpaceX, up from 31st for all of 2021.
The Dragon spacecraft, which is operating a mission called the CRS-25, is carrying 2,668 kilograms of cargo, including scientific research, crew supplies, spacewalk equipment and hardware. That total includes 544 kilograms of equipment housed in the unpressurized trunk portion of the spacecraft.
One of the science payloads is an Earth science instrument called Earth Surface Mineral Dust Source Investigation, or EMIT, which will be installed on the outside of the station. It will be used to study dust mineral dust in the atmosphere and how it interacts with ecosystems worldwide.
“We really need to be able to model how dust interacts with the entire Earth system,” Robert Green, principal investigator for EMIT at the Jet Propulsion Laboratory, said at a NASA briefing in June. EMIT provides much more data on mineral dust than other sensors. “We will use these new measurements to update those Earth system models and make the Earth system models more accurate.” The instrument will also support planning for the Earth System Observatory’s line of future missions.
The launch of the CRS-25 mission was scheduled for early June. However, NASA and SpaceX delayed the launch after detecting what NASA called “elevated vapor readings” of hydrazine in the spacecraft’s propulsion system. Dragon uses monomethylhydrazine and nitrogen tetroxide as propellants for its Draco thrusters that handle approach and departure from the ISS and disappear from orbit at the end of the mission.
At a prelaunch briefing on July 13, Benji Reed, senior director of manned space programs at SpaceX, said the company traced the leak to imperfections in a “sealing surface” where a valve connects to the propulsion system. “We replaced that valve and then thoroughly tested the system to confirm there is no more leakage,” he said.
He added that the problem was not with the valve itself, but with the sealing of joints and joints in the plumbing. The sealing surface around the valve had been “reworked” but seemed fine, he said. Initial testing of the propulsion system during assembly did not detect a leak, but if it existed at the time, it may not have been enough to detect that leak. SpaceX only found the leak in “full” system testing prior to launch.
“Since then, we’ve updated our processes,” Reed says. One involves reworking sealing surfaces for ‘stricter acceptability’. The company is also implementing stricter testing processes.
The problem is only for the Dragon spacecraft flying this mission. “We looked very closely at that,” he said, but found no similar issues on other Dragon spacecraft in the fleet. There is also no sign of any leaks on the Crew Dragon spacecraft currently docked at the Crew-4 mission station.
While investigating this leak, SpaceX decided to replace the spacecraft’s parachutes. Reed said that was done as a precaution because hydrazine vapors could have damaged the parachutes. “The first results of those inspections are coming in and those original parachutes look great,” he said. “We’ll likely use those on a future mission if the teams determine they’re safe to use for flight.”
Dana Weigel, deputy program manager for NASA ISS, said during the prelaunch briefing that NASA plans to keep Dragon on the station for 33 days before it disconnects and crashes off the coast of Florida. The spacecraft will bring back about 50 scientific studies, as well as space station hardware that is being repaired or replaced.
That includes a spacesuit that sustained a small water leak during a March spacewalk, or EVA, by European Space Agency astronaut Matthias Maurer, causing water to get on its helmet visor. NASA has since suspended spacewalks at the station except for unforeseen circumstances.
Weigel said NASA would like to get the suit back so engineers can determine the source of the leak. “That’s really key for us,” she said. “That will be part of what we need for our assessment” to resume spacewalks.
After CRS-25, the next commercial cargo mission is NG-18, a Northrop Grumman Cygnus mission tentatively scheduled for mid-October. The SpaceX CRS-26 Dragon mission will follow late in the year and will include a series of solar panels to be installed at the station by spacewalking astronauts. “That’s our next goal if we hope to do a planned EVA,” Weigel said.