Secretive U.S. space plane due to land

U.S. Air Force’s robotic X-37B space plane is set to return to Earth after almost two years in orbit. The secret mission is believed to have been a test of new sensors and other next-generation satellite technologies

Propulsion Liquid-fuelled rocket engine for orbital manoeuvres

Twin angled tail fins
Air brake

Payload bay: Unpressurized area similar in size to pickup truck bed. Deployable solar panels provide power in orbit

Guidance Onboard GPS navigation and flight control. Autonomous re-entry and landing sequence

Thermal protection: Heat-resistant ceramic tiles shield craft from intense heat of re-entry

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SPECIFICATIONS
Length 
Wingspan
Launch weight
Re-entry speed
Orbit range
8.38m
4.6m
5 tonnes
Mach 25
177-800km

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Avionics
JP-8 kerosene jet fuel tank
Experiment bay
Hydrogen peroxide tank
Manoeuvring thrusters
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Guidance Onboard GPS navigation and flight control. Autonomous re-entry and landing sequence

Space shuttle to scale

X-37B

X-37B MISSIONS
VEHICLE Launched Landing Duration
OTV-1
OTV-2
OTV-1
Apr 22, 2010
Mar 5, 2011
Dec 11, 2012
8 months
15 months
22 months
Dec 3, 2010
Jun 16, 2012
Oct 14, 2014

Sources: U.S. Air Force, Boeing, Space.com