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.

Boeing X-37B: Secretive mission passes 500 days in space

An artists’ conception of the X-37B in Earth orbit. 

Credit: U.S. Air Force.

A secretive mission will pass a quiet milestone at the end of this month when the U.S. Air Force's unmanned spaceplane the X-37B surpasses 500 days in space.

Launched atop an Atlas V rocket flying in a 401 configuration from Cape Canaveral Florida after several delays on December 11th, 2012 on OTV-3, the X-37B has already surpassed its own record of 469 days in space set on OTV-2.

Said milestone was crossed last month. If the current mission stays in space until April 25th of this year, it will have surpassed 500 days in space.

Two X-37Bs were built for the USAF, and the first test mission flew in 2010. NASA performed drop glide tests with an early variant of the X-37A in 2005 and 2006, and DARPA is thought to be a primary customer for the program as well.

Measuring just 8.8 metres in length, the X-37B is tiny compared to its more famous spaceplane cousin the U.S. Space Shuttle.

The X-37B has a maximum weight at liftoff of 4,990 kilograms and features a payload bay 2.1 by 1.2 metres in size.

The spacecraft itself is solar powered, as it unfurls a panel—as depicted in many artists' conceptions—once it's in orbit.

Of course, its mission profile is classified, and the X-37B could land unannounced at any time. The previous landings occurred at Vandenberg Air Force Base in California and were only announced shortly thereafter.


Not only is this the longest continuous mission for any spaceplane, but the ATV-3 is also the smallest, lightest and only the second spaceplane to land autonomously, the first being the Russian space shuttle Buran that flew one mission and landed after one orbit at the Baikonur Cosmodrome on November 15th, 1988.

The idea of a reusable spaceplane has been around since the dawn of the Space Age. The U.S. Space Shuttle program was the most high profile of these, having flown 135 missions from 1981 to 2011.

The X-37B awaiting encapsulation for launch. 

Credit: U.S. Air Force.

But even the space shuttle launch system wasn't fully reusable, expending its large orange external fuel tank after every mission and requiring extensive refurbishment for the solid rocket motors and orbiter after each and every flight.

The Soviets abandoned Buran in 1988, and other examples of spaceplanes such as North American's X-15 surpassed the 100 kilometre in altitude Kármán line marking the boundary to space, but were suborbital only.

And this year, customers may get a chance to make similar suborbital hops into space aboard Virgin Galactic's SpaceShipTwo spaceplane at $250,000 dollars a ticket.

But the most ambitious design for a true spaceplane was conceived in the 1960's: Boeing's X-20 Dyna-Soar, which was never built.