US Dragon spacecraft arrives at space station

The unmanned Dragon capsule owned by private US firm SpaceX arrived at the International Space Station (ISS) Tuesday morning for its fourth commercial resupply mission to the orbiting laboratory, US space agency NASA said.

The spacecraft was successfully captured by a robotic arm operated by astronauts Alexander Gerst and Reid Wiseman inside the ISS at 6:52 am EDT (1052 GMT), NASA said.

Dragon, which was launched aboard a Falcon 9 rocket early Sunday, carried 2.5 tons of supplies and payloads, including materials to support 255 scientific experiments in space.

The interesting scientific payloads on Dragon include the first 3D printer in space, which is the size of a small microwave, a group of 20 mice to study the long-term effects of microgravity on mammalian physiology, and a science instrument to monitor ocean winds.

Dragon is scheduled to spend four weeks there and then leave the ISS in mid-October for a parachute-assisted splashdown off the coast of California.

It was Dragon's fourth cargo mission to the ISS. Under a 1.6-billion-U.S.dollar contract with NASA, SpaceX will fly a total of 12 cargo missions to the ISS using the Dragon spacecraft and the Falcon 9 rocket.

Besides SpaceX, NASA has also signed a deal with another private company called Orbital Sciences Corp. to supply cargo to the ISS.