Boeing X37B, US Top Secret Spy Plane lands after 674 days in Orbit

This June 16, 2012 file image from video made available by the Vandenberg Air Force Base shows an infrared view of the Boeing X-37B unmanned spacecraft landing at Vandenberg Air Force Base. 

The purpose of the U.S. military's space plane is classified, only fueling speculation about why it has been orbiting Earth for nearly two years on this, its third mission. 

The plane is expected to land this week at a Southern California Air Force base. 

Credit: AP Photo /Vandenberg Air Force Base

A top-secret space plane landed Friday at an Air Force base on the Southern California coast.

The plane spent nearly two years circling Earth on a classified mission. Known as the Boeing X-37B, it resembles a mini space shuttle.

It safely touched down at 9:24 a.m. Friday, officials at Vandenberg Air Force Base said.

Just what the plane was doing during its 674 days in orbit has been the subject of sometimes spectacular speculation.

Several experts have theorized it carried a payload of spy gear in its cargo bay.

Other theories sound straight out of a James Bond film, including that the spacecraft would be able to capture the satellites of other nations or shadow China's space lab.

In a written release announcing the return of the craft, the Air Force only said it had been conducting "on-orbit experiments."

The Boeing X-37B program has been an orphan of sorts, bouncing since its inception in 1999 between several federal agencies, NASA among them. It now resides under the Air Force's Rapid Capabilities Office.

The plane that landed Friday is one of two built by Boeing. This is the program's third mission, and began in December 2012.

The plane stands 9 1/2 feet tall and is just over 29 feet long, with a wingspan under 15 feet. It weighs 11,000 pounds and has solar panels that unfurl to charge its batteries once in orbit.

The Air Force said it plans to launch the fourth Boeing X-37B mission from Cape Canaveral, Florida, next year.

USAF Boeing X-37B: 500 days in orbit and more speculation

The highly extended mission hints that there's more than mundane testing on this flight. Perhaps components that were undergoing testing on previous flights are now on a true operational mission. 

Or perhaps we are witnessing a long endurance run to prove that certain critical satellite parts can work reliably for a long-duration spy satellite. Both theories are plausible.

With more than 500 days in orbit, the third mission of the mysterious X-37B spaceplane is not only longer than any previous flight, but also much stranger.

The X-37B is a robotic spacecraft launched by the US Air Force on a secret mission that has generally eluded boffins and analysts.

It's not unusual for nations to launch secret spacecraft, but it's often the case that their true missions can be deduced.

The size of the rocket, the orbit and other factors can give analysts clues that a certain satellite is an optical spy satellite, a radar observation satellite or a classified communications satellite.

Knowing that the secrecy is sometimes just a formality, some missions have patches that hint at their true missions, like owl's eyes and large mesh arrays with the motto "We own the night".

Suspicions that this was a radar observation satellite that could see targets in the dark were confirmed.

No such clues have been dropped for X-37B. Part of its mission is known, thanks to US Air Force statements and the fact that X-37B was once a civilian project operated by NASA.

This is an experimental spaceplane designed to test new technologies, ranging from "robot pilot" avionics to an advanced heatshield system.

Photography of the exterior of this spaceplane has been extensive, both before and after landing.

There's more mystery surrounding what lies inside. X-37B features a small shuttle-like payload bay in its middle, with clamshell doors that open in space.

We know that there's a solar panel inside that unfurls from a mast once the X-37B is in orbit but there's room for other items too.

Exactly what else is inside, and what it's doing, has confounded the media and the space community.

This analyst has suggested that X-37B is conducting mundane but critical tests of electromechanical components intended for future US national security satellites.

The parts are operated in open space for long periods then returned to Earth for study.

Other analysts have suggested that the vehicle is conducting a semi-operational mission that involves the use of sensors for Earth observation.

NASA Space Shuttle Hangar assigned to Boeing X37B Secret Space Plane

Space shuttle Atlantis backs out of Orbiter Processing Facility-1 (OPF-1) at NASA's Kennedy Space Center in Florida in 2011. 

The building will now be used by Boeing to service the U.S. Air Force’s X-37B space plane.

A former NASA space shuttle hangar will serve as the new home and servicing facility for a fleet of secretive military space planes.

The Boeing Company announced on Friday (Jan. 3) it will begin converting Orbiter Processing Facility-1 (OPF-1) at NASA's Kennedy Space Center in Florida to support the U.S. Air Force X-37B Orbital Test Vehicle (OTV).

Built by Boeing's Phantom Works, the winged X-37B space plane resembles in some ways a smaller version of NASA's shuttle with a 15-foot (4.5 m.) wingspan.

The move to use OPF-1 will "enable the U.S. Air Force to efficiently land, recover, refurbish, and re-launch" the 29-foot-long (8.8 m.), reusable unmanned spacecraft, Boeing officials said in a statement.

No other details were released, other than Boeing noting the project will expand its presence in Florida by "adding technology, engineering and support jobs at the Kennedy Space Center."

This NASA Marshall Space Flight Center image shows on-orbit functions for the reusable X-37 space plane, now under the wing of the U.S. Air Force. 

Credit: NASA/MSFC