An artist's illustration of the U.S. Air Force's X-37B space plane in orbit. The solar-powered winged spacecraft has spent more than 620 days in orbit as part of the military's secret OTV-3 mission, which launched in December 2012. Credit: NASA Marshall Space Flight Center
The U.S. Air Force's mysterious unmanned space plane has winged beyond 600 days in orbit on a classified military mission that seems to have no end.
The X-37B space plane is carrying out the Orbital Test Vehicle-3 (OTV-3) mission, a long-duration cruise that marks the third flight for the unpiloted Air Force spaceflight program.
The Air Force launched the miniature space shuttle into orbit on Dec. 11, 2012 using an expendable Atlas 5 rocket.
By the end of Friday (Aug. 29), the space plane had spent 627 days in orbit. That's one year, eight months, 19 days and counting, to be exact.
"The Air Force continues to push the envelope of the solar-powered X-37B capabilities," said Joan Johnson-Freese, a professor of National Security Affairs at the U.S. Naval War College in Newport, Rhode Island.
The unmanned X-37B spacecraft — flying a mission known as Orbital Test Vehicle 3 (OTV-3) — launched into space atop an Atlas 5 rocket from Florida’s Cape Canaveral Air Force Station on Dec. 11, 2012.
What payloads the space plane is toting and the overall mission goals on its confidential cruise are classified.
But it is known that the OTV-3 mission signals a milestone for the X-37B program.
This same vehicle was flown on the X-37B program's inaugural flight back in 2010.
That OTV-1 mission lasted nearly 225 days in orbit, gliding back to Earth on autopilot over the Pacific Ocean and touching down at Vandenberg Air Force Base in California.
An OTV-2 mission, which used a different X-37B space plane, was lofted in 2011. That vehicle flew for 469 days, more than doubling its sister ship’s space stay, concluding its mission by also making a Vandenberg landing.
Next-generation technology
According to a Boeing fact sheet, each space plane is built with lightweight composite structures, rather than traditional aluminum.
A new generation of high-temperature leading-edge tiles for the wings is utilized, distinct from the space shuttle’s carbon leading-edge segments.
The X-37B is outfitted with toughened uni-piece fibrous insulation impregnated silica tiles, which are significantly more durable than the first-generation tiles used by the space shuttle.
Advanced conformal reusable insulation blankets are used for the first time on the X-37B.
The Boeing fact sheet also points out that avionics on an X-37B are designed to automate all de-orbit and landing functions.
Additionally, there are no hydraulics onboard the winged vehicle; flight controls and brakes use electromechanical actuation.
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