This afternoon, SpaceX is set to launch its Dragon cargo capsule, filled with nearly 5,700 pounds of cargo and supplies for the crew of the International Space Station. It’s SpaceX’s last resupply mission to the station for 2019. Following the flight, SpaceX will attempt one of its signature rocket landings, targeting a drone ship floating in the Atlantic Ocean.
It’s atypical for SpaceX to do an ocean landing after a flight to the ISS. Normally, the company tries to land its Falcon 9 rocket on a concrete landing pad on solid ground. That’s because there’s usually enough propellant left over to pull off such a ground landing. Getting to low Earth orbit — where the space station lives — is a fairly short trip. That means there’s usually…