Pictures: Secretive X-37B lands at Kennedy Space Center

U.S. Air Force courtesy photo The secretive unmanned X-37B spaceplane operated by the U.S. Air Force Rapid Capabilities Office, has com...

U.S. Air Force courtesy photo

The secretive unmanned X-37B spaceplane operated by the U.S. Air Force Rapid Capabilities Office, has completed its fourth mission, Air Force announced today.

The reusable space plane, landed at the NASA’s Kennedy Space Center Shuttle Landing Facility in Florida today morning, after being in space for 718 days, conducting on-orbit experiments. This brings total days spent in orbit by the OTV program to 2,085 days since first mission in 2010.

Local residents were greeted with the sonic boom of the spacecraft as it arrived for touch down.

While looking and operating similar to the retired NASA Space Shuttles, the X-37B is much smaller, and being unmanned can remain in space for longer periods, at more than 270 days.

USAF says the X-37B program performs risk reduction, experimentation and concept of operations development for reusable space vehicle technologies.

U.S. Air Force courtesy photo

The X-37B is designed for vertical launch in the payload bay of a United Launch Alliance Atlas V rocket, to low Earth orbit altitudes where it can perform long duration space technology experimentation and testing. Upon command from the ground, the OTV autonomously re-enters the atmosphere, descends, and lands horizontally on a runway.

Small thrusters at its nose and tail help to maneuver in the orbit along with a larger rocket engine at the rear.

Technologies being tested in the program include advanced guidance, navigation and control, thermal protection systems, avionics, high temperature structures and seals, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems, advanced materials and autonomous orbital flight, reentry and landing.

The #X37B #OTV4 is the newest and most advanced re-entry spacecraft. Find out more about today's landing here: https://t.co/GUGgOMQiYg pic.twitter.com/HfHHVnWhYc

— U.S. Air Force (@usairforce) May 7, 2017

Developed by Boeing, the X-37B has a launch weight of 11,000 pounds (4,990 kilograms) and is 29 feet, 3 inches (8.9 meters) long with a wingspan of 14 feet, 11 inches (4.5 meters).

The Air Force is preparing to launch the fifth X-37B mission from Cape Canaveral Air Force Station, Florida, later in 2017.