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.

The HTV-1 is the first in a new line of Japanese space freighters to haul tons of supplies for astronauts aboard the space station. It is the latest addition to an international flotilla of unmanned space cargo ships for the station that includes Russian and European vehicles.

But the HTV-1 is currently the only freighter capable of delivering cargo for use inside the station, as well as new experiments and other equipment for the outpost's exterior. It is due to fire its thrusters on Sunday in order to begin an intentional death plunge into Earth's atmosphere over the Pacific Ocean.

"We'd like to thank everybody across the planet for this beautiful vehicle," NASA astronaut Nicole Stott radioed Mission Control as HTV-1 left the station's vicinity. "It was pretty much flawless from beginning to end."

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. The debris, part of a defunct Russian satellite, posed no danger to the space station and its crew, but could have posed a threat to the HTV-1 once it entered a different orbit later today, NASA officials said.

The Japan Aerospace Exploration Agency (JAXA) launched the HTV-1 in early September using its brand-new H-2B rocket. Both spacecraft functioned perfectly during the spaceflight debut. A mission control center in Tsukuba, Japan, watched over HTV-1's weeklong trek to the space station.

The gleaming HTV-1 is a gold-colored cylinder about 33 feet long, 14 feet wide and covered in solar panels attached to its curved hull. It is capable of hauling up to 6 tons of cargo to the space station, but HTV-1 carried about 4 1/2 tons of supplies on its maiden flight, NASA officials have said.

HTV-1 arrived at the space station on Sept. 17, when Stott and her five crewmates plucked it from space using the station's robotic arm. They packed it with nearly 1,600 pounds of trash before discarding the disposable spacecraft Friday.

Unlike Russian and European cargo ships, which can fly themselves up to the space station autonomously, HTV-1 is designed to be grappled by the station's arm. NASA hopes to use a similar method for securing future commercial cargo ships built in the United States.

JAXA officials said Japan spent about $220 million to build HTV-1, but the spacecraft's development has cost an estimated $680 million since 1997. The Japanese agency plans to build at least one new HTV a year, they added.