X-37B Space Plane: US Air Force's 4th Mystery Mission in Photos

OTV-4: X-37B's Fourth Flight

United Launch Alliance

The mission poster for the fourth X-37B space plane launch by the U.S. Air Force and United Launch Alliance. The X-37B is also known as the Orbital Test Vehicle, hence the mission's OTV-4 designation. This flight is called the AFSCP-5 flight for Air Force Space Command 5.

X-37B in Rocket Nose Cone

NASA

When readied for launch, the X-37B space plane is packed upright inside a rocket payload fairing (the nose cone) as shown in this image from the first X-37B launch (OTV-1) in 2010.

X-37B Space Plane 4th Launch

ULA

The Air Force's robotic X-37B space plane launched aboard an Atlas V rocket from Cape Canaveral, Florida, on May 20, 2015.

X-37B Space Plane 4th Launch #2

ULA

The Air Force's robotic X-37B space plane launched aboard an Atlas V rocket from Cape Canaveral, Florida, on May 20, 2015.

X-37B Space Plane 4th Launch #3

ULA

The Air Force's robotic X-37B space plane launched aboard an Atlas V rocket from Cape Canaveral, Florida, on May 20, 2015.

X-37B Space Plane Rollout 1

United Launch Alliance

At Cape Canaveral Air Force Station, Florida, an Atlas V rocket carrying the Air Force's X-37B space plane rolls out to the launch pad on May 19, 2015. Launch of the AFSPC-5 mission is scheduled for May 20.

X-37B Space Plane Rollout 2

United Launch Alliance

At Cape Canaveral Air Force Station, Florida, an Atlas V rocket carrying the Air Force's X-37B space plane rolls out to the launch pad on May 19, 2015. Launch of the AFSPC-5 mission is scheduled for May 20.

X-37B Space Plane Rollout 3

United Launch Alliance

At Cape Canaveral Air Force Station, Florida, an Atlas V rocket carrying the Air Force's X-37B space plane rolls out to the launch pad on May 19, 2015. Launch of the AFSPC-5 mission is scheduled for May 20.

X-37B Space Plane Rollout 4

United Launch Alliance

At Cape Canaveral Air Force Station, Florida, an Atlas V rocket carrying the Air Force's X-37B space plane rolls out to the launch pad on May 19, 2015. Launch of the AFSPC-5 mission is scheduled for May 20.

AFSPC-5 Payload Encapsulation Raising Up

ULA

The Air Force's AFSPC-5 payload inside a 5-meter diameter payload fairing undergoes mating to an Atlas V booster inside the Vertical Integration Facility at Cape Canaveral Air Force Station's Space in Florida. Launch is set for May 20, 2015.

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com.

Space.com Staff
News and editorial team

Space.com is the premier source of space exploration, innovation and astronomy news, chronicling (and celebrating) humanity's ongoing expansion across the final frontier. Originally founded in 1999, Space.com is, and always has been, the passion of writers and editors who are space fans and also trained journalists. Our current news team consists of Editor-in-Chief Tariq Malik; Editor Hanneke Weitering, Senior Space Writer Mike Wall; Senior Writer Meghan Bartels; Senior Writer Chelsea Gohd, Senior Writer Tereza Pultarova and Staff Writer Alexander Cox, focusing on e-commerce. Senior Producer Steve Spaleta oversees our space videos, with Diana Whitcroft as our Social Media Editor.