Vandenberg AFB preps for X-37B landing

CBS News

The Air Force is preparing to bring its unmanned X-37B spaceplane back to Earth after 15 months of clandestine military operations. The robotic spaceplane, a lifting body one quarter the size of NASA's now-retired space shuttle, is expected to land on a 3-mile-long runway at Vandenberg Air Force Base, Calif., sometime in the next two weeks.

An artist's concept of the Air Force's X-37B spaceplane in orbit. (Credit: Boeing)
The X-37B was boosted into orbit by a United Launch Alliance Atlas 5 rocket that took off from Florida's Cape Canaveral Air Force Station on March 5, 2011. It was the second launch for the Air Force Orbital Test Vehicle program following a successful 224-day maiden flight in 2010. The spacecraft used for that mission has been refurbished and is expected to be relaunched in October.

As with the initial test flight, the spaceplane currently in orbit has been operating in military secrecy since launch last year. Amateur satellite trackers, however, have monitored the spacecraft's trajectory in a roughly 210-mile-high orbit tilted 42.8 degrees to the equator. Ted Molczan, an accomplished satellite tracker in Canada, told Spaceflight Now the spacecraft began reducing its altitude in May, initially dropping to an altitude of 182 miles.

It is not clear when the X-37B will land, but whenever it comes down it will make its high-speed descent under the control of a state-of-the-art autopilot incorporating Global Positioning System navigation data.

Equipped with twin tail fins, stubby wings and an advanced heat shield, the X-37B, built by Boeing's Experimental Systems Group, measures 29 feet long with a wingspan of 14 feet. Fueled for launch, the spaceplane tips the scales at some 11,000 pounds.

Originally developed by NASA, Boeing and the Defense Advanced Research Projects Agency, or DARPA, the X-37 program ultimately was folded into the Orbital Test Vehicle program operated by the Rapid Capabilities Office of the Air Force.

"The X-37B is one-fourth the size of the space shuttle, and relies upon the same family of lifting body design," Boeing says in a company description. "It also features a similar landing profile. The vehicle was built using lighter composite structures, rather than traditional aluminum.

Along with improved wing leading edge insulation, the spacecraft also incorporates tougher heat-shield tiles across its underside that "are significantly more durable than the first generation tiles used by the space shuttle," Boeing said. "All avionics on the X-37B are designed to automate all de-orbit and landing functions."

The spaceplane is equipped with a payload bay about the size of a pickup truck bed -- 7 feet by 4 feet -- but it's not known what might have been carried aloft during the OTV program's second mission.

Among the possibilities: reconnaissance cameras or other spy sensors; test gear to precisely measure the craft's performance over the course of a long-duration mission; space exposure experiments to help researchers learn more about the long-term effects of the space environment on sensitive materials or instruments. The Air Force will not discuss any aspect of the craft's mission.

"Our second X-37 test vehicle has been on orbit for 409 days now, much longer than the 270-day baseline design spec," Air Force Gen. William L. Shelton, commander of Air Force Space Command, said at the 28th Annual National Space Symposium in April. "Although I can't talk about mission specifics, suffice it to say this mission has been a spectacular success."