US air force launch robotic space plane into orbit for a fourth flight aboard rocket

THE US air force has launched its robotic space plane into orbit for a fourth flight aboard an Atlas 5 rocket.

This June 2009 photo made available by the U.S. Air Force via NASA shows the X-37B Orbital Test Vehicle at Vandenberg Air Force Base, Calif. On Wednesday, May 20, 2015, the Air Force launched its unmanned mini-shuttle from Cape Canaveral, Fla. Like the old shuttle, the X-37B launches vertically and lands horizontally, is reusable, and has lots of room for experiments. But no one flies on them; they are operated robotically. (U.S. Air Force via AP)

THE US air force has launched its robotic space plane into orbit for a fourth flight aboard an Atlas 5 rocket, in a mission aimed at testing a new engine to steer satellites.

The rocket carrying the X-37B successfully lifted off from Cape Canaveral, Florida, on Wednesday and officials said the scheduled return of the unmanned plane had yet to be determined.

The mini-shuttle has been shrouded in secrecy and military officers have refused to discuss its purpose.

But defence experts have speculated it might be meant for spying from space, fixing broken satellites or even as a space “bomber.”

Captain Chris Hoyler, a spokesman for the US air force, said the latest flight was part of efforts looking at the “technical parameters for an affordable, reusable space vehicle.”

The Atlas V rocket carrying the X-37B space plane launches. Picture: AFP/ HO/United Launch Alliance

The X-37B will be testing a new orbital “thruster system” — which uses electricity and xenon — that could be employed to manoeuvre satellites in space, officials said.

Asked if the plane could be used for surveillance, Hoyler declined to comment.

The X-37B payload also includes a NASA experiment, which will study how a range of materials can endure conditions in space. The results could help scientists working on the possible design of future spacecraft.

The last mission for the X-37B in 2014 extended over 674 days but officials never said what the plane was up to. AFP evt