SpaceX has arrived at the International Space Station, delivering the world's first inflatable tent for astronauts.

The US aerospace company's unmanned Dragon cargo ship, carrying lettuce seeds, lab mice and an inflatable pop-up room, arrived on Sunday at the space station where six spacecraft are now docked.

British astronaut Tim Peake reached out with the station's robotic arm and grabbed the Dragon, carrying its nearly 3,175kg of gear, at 7:23am (11:23 GMT).

"It looks like we've caught a Dragon," said Peake.

Four Russian spaceships - two Progress cargo carriers and two Soyuz capsules which ferry astronauts - are docked at the space station, along with Orbital ATK's Cygnus cargo ship and SpaceX's Dragon.

Not since 2011, during the final flight of the space shuttle Discovery, have there been six vehicles parked at the space station at the same time, NASA said.

Included in the Dragon's cargo is an expandable room that will be temporarily attached to the orbiting outpost.

Known as the Bigelow Expandable Activity Module, the habitat is not scheduled for use until the end of May, but will stay at the space station for two years so astronauts can test how it stands up to space debris and solar radiation.

Six space vehicles are parked at the International Space Station, NASA said [Tim Peake/ESA/NASA/Handout/Reuters]

The module can expand to about three metres by four metres.

Astronauts plan to enter the room "for a few hours several times a year to retrieve sensor data and assess conditions," NASA said.

The cargo also contains Chinese cabbage seeds which astronauts will grow in space, and lab mice that will test whether certain drugs can help prevent muscle and bone loss in microgravity.

SpaceX's Dragon is currently the only spaceship capable of returning cargo to Earth.

It is expected to splash down in the Pacific Ocean on May 11, carrying science experiments including biological samples from astronaut Scott Kelly's one-year mission which ended in March.

The Dragon blasted off on Friday from Cape Canaveral, Florida, atop a Falcon 9 rocket.

Minutes after launch, the first stage portion of the Falcon 9 rocket successfully landed on a drone ship in the Atlantic Ocean for the first time.

The feat was hailed as a big step forward for SpaceX chief executive Elon Musk's mission to make rockets as reusable as airplanes, an innovation that he says will bring down the cost of space flight.

Currently, sophisticated rocket parts costing tens of millions of dollars are jettisoned into the sea after launch.

Source: AFP