NASA is about to have double Dragons at its space station

NASA and SpaceX are making final preparations for a cargo mission that will carry nearly three metric tons of supplies to the International Space Station.

This “CRS-21” mission is the 21st cargo supply mission that SpaceX will launch for NASA overall. But it is the first under a new supply contract that runs through 2024, and this will be the first to use an upgraded “Cargo Dragon 2” vehicle to ferry food, water, science experiments, and other materials to the orbiting laboratory.

The new cargo vehicle is a modified version of the Crew Dragon spacecraft that has flown humans to the space station twice this year, in May and November. The cargo variant lacks seats and cockpit controls, a life support system, and the Super Draco thrusters that are used as an emergency escape system if a problem occurs during launch.

Compared to the first SpaceX cargo vehicle, Cargo Dragon 2 features a dozen powered lockers for science experiments, twice as many as previously flown. It is also designed to be recovered and readied for repeat flights more quickly than its predecessor, and the vehicle has the capability to autonomously dock with the station, rather than needing to be grabbed by a robotic arm and attached to a port.

After it launches and reaches the space station, there will be two Dragon vehicles attached to the laboratory for the first time. That’s because Crew Dragon Resilience, which launched on November 15 carrying four astronauts, is also docked to the station and will remain there for about five more months.

It’s also worth noting that NASA continues to become more comfortable with reusing spacecraft and rockets built by SpaceX. The Falcon 9 first stage being used for this mission has already flown three times. In all of the missions that SpaceX has flown for NASA before, the space agency has never allowed the company to use a first-stage booster that has flown more than once. In the photos above, the dirty and sooty booster makes a stark contrast with the shiny, white Cargo Dragon 2 spacecraft.

This mission is scheduled to launch at 11:39am ET (16:39 UTC) on Saturday from Launch Complex 39A at Kennedy Space Center in Florida. Weather is a concern, both at the launch site and for recovery of the Falcon 9 rocket’s first stage. The official forecast calls for a 50-percent chance of favorable conditions at the launch site on Saturday. Weather is better for a back-up launch opportunity on Sunday, so the launch may well slip a day.

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Listing image by NASA