Japan's first unmanned space cargo ship cast off from the International Space Station Friday as it nears the end of a successful maiden voyage. Astronauts aboard the station used the outpost's robotic arm to pluck the spacecraft, called the H-2 Transfer Vehicle 1 (HTV-1), free from an Earth-facing mooring and let it go at about 1:30 p.m. EDT. NASA delayed the departure of HTV-1 from the station by one orbit - about 90 minutes - in order to be sure a piece of Russian space junk would not pose a risk to the spacecraft.