Inside the Air Force's secret space plane

The Air Force launched its third Orbital Test Vehicle, the X-37B, Dec. 11, 2012, at Cape Canaveral, Fla. The third launch follows closely behind a record-setting 469 days in space for the second OTV. (U.S. Air Force)

The Air Force launched its third Orbital Test Vehicle, the X-37B, Dec. 11, 2012, at Cape Canaveral, Fla. The third launch follows closely behind a record-setting 469 days in space for the second OTV. (U.S. Air Force)

The U.S. Air Force's secrecy-shrouded X-37B unmanned spaceplane returned to Earth early Friday after more than seven months in orbit on a classified mission, officials said. (Boeing)

The winged craft autonomously landed at at Vandenberg Air Force Base on the California coast 130 miles northwest of Los Angeles, Vandenburg spokesman Jeremy Eggers said. "It's very exciting," Eggers said of the 1:16 a.m. PST landing. (USAF / Vandenberg AFB)

The X-37B was launched by an Atlas 5 rocket from Cape Canaveral, Florida, on April 22, with a maximum mission duration of 270 days. (USAF / Vandenberg AFB)

Also known as the Orbital Test Vehicle, the Boeing-built spacecraft was originally a NASA project before being taken over by the military. (USAF / Vandenberg AFB)

The Air Force has not said whether it carried anything in its cargo bay, but insists the primary purpose of the mission was to test the craft itself. "We are very pleased that the program completed all the on-orbit objectives for the first mission," program manager Lt. Col. Troy Giese said in a statement. (USAF / Vandenberg AFB)

The craft is expected to return to space next year. Officials have made public only a general description of the mission objectives: testing of guidance, navigation, control, thermal protection and autonomous operation in orbit, re-entry and landing. (USAF / Vandenberg AFB)

The ultimate purpose of the X-37B and details about the craft have longed remained a mystery, though experts said the spacecraft was intended to speed up development of combat-support systems and weapons systems. (Boeing)

April 22, 2010: U.S. Air Force's novel robotic X-37B space plane launches atop an Atlas 5 rocket from a seaside pad at the Cape Canaveral Air Force Station in Florida. (NASA)

This undated image released by the U.S. Air Force shows the X-37B spacecraft, which got a boost into orbit from Florida on April 22. The reusable robotic X-37B Orbital Test Vehicle is a small space shuttle-like craft. The craft will wing its way into Earth orbit, remain aloft for an unspecified time, then high-tail its way back down to terra-firma -- auto-piloting down to a landing at Vandenberg Air Force Base in California. (AP)

Diagram of the U.S. Air Force's X-37B Orbital Test Vehicle. Some new details have emerged on the secretive space plane's April 2010 launch test flight. (Karl Tate/Space.com)

The U.S. Air Force's X-37B Orbital Test Vehicle is shown inside its payload fairing during encapsulation at the Astrotech facility in Titusville, Fla., ahead of a planned April 2010 launch from Cape Canaveral Air Force Station in Florida. (USAF)

A United Launch Alliance Atlas 5 rocket with the Air Force's X-37B Orbital Test Vehicle (OTV) -- inside the bulbous nose cone -- the rolls out to its Space Launch Complex-41 launch pad at the Cape Canaveral Air Force Station in Florida on April 21, 2010. (Pat Corkery/United Launch Alliance)

This diagram depicts the Orbital Test Vehicle 1 space plane and its position atop the Atlas 5 rocket that will launch it into space on a test flight in April 2010. (United Launch Alliance)

The X-37B/Orbital Test Vehicle spacecraft undergoes final testing at Boeing.  (U.S. Air Force)

Artist's conception of the X-37 advanced technology flight demonstrator re-entering Earth's atmosphere. The X-37 will be a testbed for dozens of advanced structural, propulsion and operational technologies that could dramatically lower the cost of future reusable launch vehicles. The X-37 will operate in both the orbital and reenty phases of flight. The X-37 measures approximately 27.5 feet long and 15 feet in wingspan. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the X-37 project. The X-37 industry team is led by The Boeing Co. of Seal Beach, Calif.  <b>Source</b>: NASA/MSFC

Artist's depiction of the X-37 Flight Demonstrator. While the launch range approval is still forthcoming, SPACE.com has learned that the U.S. Air Force has the X-37B manifested for an April 2010 liftoff. <b>Source: </b>Boeing Phantom Works

Illustration of the X-37 Advanced Technology Demonstrator during flight. As a mini-space plane, this Boeing Phantom Works craft has been under development for years. Several agencies have been involved in the effort, NASA as well as the Defense Advanced Projects Research Agency (DARPA) and various arms of the U.S. Air Force. <b>Source</b>: NASA

Illustration of the X-37 Advanced Technology Demonstrator in STS cargo bat. Once in orbit, what such a vehicle might enable depends on the eye of the beholder. Intelligence gathering, kicking off small satellites, testing space gear are feasible duties, as is developing reusable space vehicle technologies. <b>Source</b>: NASA

NASA's X-37 Approach and Landing Test Vehicle is installed in a structural test facility at Boeing's Huntington Beach, Calif., plant.  The tests, which were completed in July 2003, were conducted to verify the structural integrity of the vehicle in preparation for atmospheric flight tests.  The X-37 is a flight demonstrator project to flight test advancing technologies for NASA's Orbital Space Plane Program.  <b>Source: </b>Boeing/R. Davis

A Boeing technician makes adjustments to composite panels on NASA's X-37 Approach and Landing Test Vehicle in preparation for structural testing at Boeing's Huntington Beach, Calif., plant.  The proof tests to validate the structural integrity of the airframe were successfully completed in July 2003.  Technologies demonstrated will aid in the design of the Orbital Space Plane.  <b>Source: </b>Boeing/R. Davis

Boeing technicians at the Huntington Beach plant make adjustments to composite panels on NASA's X-37 Approach and Landing Test Vehicle prior to proof tests to validate the airframe structure.  The X-37 is an advanced technology flight demonstrator designed to test technologies for the Orbital Space Plane Program.  <b>Source: </b>Boeing/R. Davis

The unpowered, unpiloted X-40A vehicle is an 85 percent scale, risk-reduction version of the proposed X-37 flight demonstrator.  In 2001, the X-40A proved the capability of an autonomous flight control and landing system in a series of flight tests at NASA'a Dryden Flight Research Center. Ultimately, the unpiloted X-37 is intended as an orbital testbed and technology demonstrator, capable of landing like an airplane and being quickly serviced for a follow-up mission. <b>Source</b>: NASA

X-40A's first flight was a 74 second glidef from 15,000 feet on March 14, 2001.  Each of the seven flights were successfully completed. The unpiloted X-40 is a risk-reduction vehicle for the X-37, which is intended to be a reusable space vehicle.  The X-37 is designed to demonstrate technologies in the orbital and reentry environments for next-generation reusable launch vehicles that will increase both safety and reliability, while reducing launch costs from $10,000 per pound to $1,000 per pound. <b>Source</b>: NASA

The X-40A vehicle, released from a helicopter during a test at NASA's Dryden Flight Research Center. <b>Source</b>: NASA

CH-47 and X-40A before Free Flight 4A. The unpiloted X-40 is a risk-reduction vehicle for the X-37, which is intended to be a reusable space vehicle. <b>Source</b>: NASA