The crew will have their hands full as they offload the spacecraft's 1.8 tons of pressurized supplies and experiments. Mike Suffredini, NASA’s ISS Program manager, estimated it was the biggest cargo haul for Dragon to date. There is also equipment in the spacecraft's unpressurized exterior, including CATS, the Cloud-Aerosol Transport System. CATS will be installed on the station's exterior to monitor the planet's distributions of clouds and aerosols.

Dragon's journey began Saturday morning with the liftoff of a Falcon 9 rocket from Cape Canaveral on the Florida coast. As this is SpaceX's fifth paid cargo run and sixth overall since 2012, the scene has become remarkably routine. Most of the attention surrounding the flight focused on an attempt to land the Falcon's core stage on an autonomous landing pad in the Atlantic Ocean. The rocket made it back to the landing ship but crashed, prompting CEO Elon Musk to call the effort "close, but no cigar."

The landing ship is a repurposed ocean barge equipped with thrusters to help it hold steady within a radius of three meters—even in the choppiest of ocean conditions. It returned to the Port of Jacksonville with support ships Sunday afternoon. Internet discussion boards were abuzz with speculation as users shared screenshots of the ship obtained from various webcams, along with photos and video captured by spectators along the St. John's River. Space news website Spaceflight Now captured several images of the landing pad returning to port. It appeared to be in good condition, with a handful of onboard support structures blackened or damaged.

All of the publicly available information about what happened Saturday comes from Elon Musk on Twitter. On Saturday morning, Musk said the set of deployable grid fins used to control the rocket's descent ran out of hydraulic fluid: