Space shuttle Discovery departed the International Space Station today, leaving behind a new storage room, a prototype robot and tons of supplies during its 39th and final space flight.Discovery pilot Eric Boe gently pulsed the ship's steering jets to back away from the station at 1200 GMT, completing a nine-day visit. The shuttle is due back at the Kennedy Space Center in Florida on Wednesday. The station, a 100 billion dollar project of 16 nations, has been under construction since 1998.Discovery delivered a combination storage room-research module to the outpost, along with an outdoor platform to house large spare parts and tons of equipment, supplies and science experiments. The gear includes a prototype humanoid robot called Robonaut 2, or R2, which has not yet been unpacked.The crew conducted two spacewalks to help prepare the station for operations after the shuttle fleet's retirement. They stayed two extra days to give the six live-aboard station crewmembers a hand setting up the new module.