Top-secret US drone, X-37B, returning home, but what did it do on mission?

AMERICA’S mystery space drone is coming home today after a record 22 months in orbit — and there’s a big secret on board.

IT spent nearly two years in orbit on a top-secret mission. Now, America’s mysterious space drone is touching down on Earth — and we still have no idea what it did up there.

And despite the mission being shrouded in secrecy, preparations are already in progress for the next mission.

“Preparations for the third landing of the X-37B are under way at Vandenberg Air Force Base” in California, said a US Air Force spokesman, Captain Chris Hoyler.

HUSH-HUSH: X-37B Orbital Test Vehicle’s mission is Pentagon’s closely guarded secret

A defence official said future missions would seek to extend the vehicle’s technical capabilities and time in orbit.

But the official, who spoke on condition of anonymity, declined to discuss exactly what the space plane carries or what its purpose is.

Returning home ... The US Air Force's mysterious unmanned space plane is about to come back to Earth after more than two years in orbit on a mission the military won't tell much about. Picture: AFP/US Air Force

“The specific parameters are unreleasable,” the official said. Analysts say the X-37B could be a platform for spying from space, including possibly snooping on other countries’ satellites.

But officials have previously denied the project had anything to do with creating a “space weapon” that could knock down other satellites.

The Air Force says the X-37B can test technology for “reusable” spacecraft and conduct unspecified experiments that can be studied on Earth.

The latest mission was the third and the longest so far for the vehicle. An initial flight launched in 2010 lasted about eight months and a second flight had the spacecraft in orbit for more than 15 months.

The X-37B, manufactured by aerospace giant Boeing, weighs five tonnes and measures about 29 feet (8.8 meters) long, with a wing span of roughly 15 feet across.

Travelling at speeds 25 times faster than the speed of sound, the vehicle is launched into space on the back of a rocket and, once its mission is complete, returns from orbit like a plane.

But, unlike NASA’s civilian shuttle, it has two stabilisers in the rear instead of one, forming a “V” shape.