SpaceX this week postponed the planned launch of a Dragon cargo mission to the International Space Station to investigate a possible leak detected while refueling the spacecraft at Cape Canaveral.
The Dragon spacecraft was scheduled to launch Friday morning from NASA’s Kennedy Space Center in Florida. Officials haven’t set a new target launch date for SpaceX’s resupply mission, but a NASA spokesperson confirmed it won’t take place on Friday or Saturday.
SpaceX detected “high vapor readings” of monomethylhydrazine, or MMH, fuel in an “isolated region” of the Dragon spacecraft’s propulsion system during propellant loading ahead of launch this week, NASA said in a statement. .
Refueling the Dragon spacecraft is one of the last steps in preparing the capsule for flight, and usually occurs just before SpaceX moves the craft to the launch pad for integration with its Falcon 9 rocket.
The Dragon spacecraft has propellant tanks containing hydrazine fuel and nitrogen tetroxide oxidizer. The two thrusters ignite on contact with each other, providing momentum to the freighter’s Draco thrusters used for maneuvering in orbit.
Each Dragon spacecraft has 16 Draco thrusters, small rocket engines that generate about 90 pounds of thrust. Draco engines are used for orbit adjustment burns and control the spacecraft’s approach to the space station, then fire at the end of the mission for a deorbit burn to guide the capsule through the atmosphere for re-entry and splash.
The SpaceX ground treatment team, working at Cape Canaveral Space Force Station’s Dragon Refurbishment Facility, offloaded fuel and oxidizer from the spacecraft area with high vapor readings of hydrazine, NASA said.
Multiple sources told Spaceflight Now that a hydrazine fuel leak could be the culprit, but NASA said the origin of the vapor has yet to be identified.
“Once the exact source of the elevated readings is identified and the cause is determined, joint NASA and SpaceX teams will determine and announce a new target launch date,” NASA said in a statement.
The Dragon spacecraft assigned to the next cargo mission is designated C208 in SpaceX’s fleet of reusable capsules. The spacecraft has visited the space station twice before, most recently on a 32-day resupply mission last August and September.
The next Dragon resupply mission, known as CRS-25, will be SpaceX’s 25th cargo flight to the space station under contract with NASA.
The Dragon capsule of the CRS-25 mission will deliver more than 4,500 pounds of food, supplies and experiments to the orbiting research laboratory.
The spacecraft will also carry an Earth science instrument to the station to monitor the mineral composition of dust particles in desert regions around the world. Developed at NASA’s Jet Propulsion Laboratory, the Earth Surface Mineral Dust Source Investigation, or EMIT, instrument is already locked inside the Dragon spacecraft’s unpressurized trunk for the journey to the space station.
The EMIT instrument will be removed from the Dragon Vault using the space station’s robotic arm and then mounted on an experiment platform outside the complex. The data collected by the instrument will help scientists learn more about the impact of dust thrown into the atmosphere by deserts on terrestrial ecosystems and human health.
While the Dragon cargo launch is on hold, SpaceX is pushing ahead with plans for another Falcon 9 launch this week with Egypt’s Nilesat 301 communications satellite. Nilesat 301 is scheduled to lift off Wednesday from Cape Canaveral during an opening launch window at 5:04 p.m. EDT (21:04 GMT).
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