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Air Force's mini space shuttle returns after 468-day flight

Posted: June 16, 2012

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Capping a 15-month clandestine military mission circling the planet, the Pentagon's miniature spaceplane, one quarter the size of NASA's now-retired space shuttle, returned to Earth just after dawn Saturday for a pinpoint touchdown at Vandenberg Air Force Base.

An artist's concept of the X-37B in space. Credit: Air Force
The Orbital Test Vehicle received the ground-issued command to come home, initiating a fully autonomous sequence of firing its propulsion system to brake from orbit, plunging through the atmosphere for a super-hot reentry over the Pacific Ocean, executing a series of turns to dissipate speed towards Vandenberg, then dropping its gear with dinner plate-sized wheels for a tire-smoking touchdown at 5:48 a.m. local (8:48 a.m. EDT; 1248 GMT) while flying on a sophisticated autopilot fed with GPS navigation.

The powerless glider's approach and landing used Vandenberg's three-mile-long concrete runway once envisioned to support manned space shuttles returning from polar-orbiting military flights. The base is located on California's Central Coast about 150 miles northwest of Los Angeles.

"Similar to OTV-1, the vehicle will go through post-landing assessments and refurbishment and lessons learned from that will be incorporated into the next mission," said Maj. Tracy Bunko, an Air Force spokeswoman.

Watch a video of the landing and see a collection of post-landing photos.

The official duration for OTV-2 was 468 days, 13 hours and 2 minutes on a voyage that circled the globe more than 7,000 times. The single-mission numbers surpassed the flight time amassed and orbits accumulated by any of the individual space shuttles in their reusable lives. Discovery had the fleet-leading credentials at 365 days and 5,800 orbits on 39 trips to space.

The marathon OTV-2 flight also lasted twice as long as the program's maiden mission in 2010.

Vandenberg officials said its personnel had conducted extensive, periodic training to stay ready to receive the spaceplane at a moment's notice. Range Safety personnel had the duty to destroy vehicle if it had deviated from prescribed boundaries, but all went according to plan Saturday.

"Team Vandenberg has put in over a year's worth of hard work in preparation for this landing and today we were able to see the fruits of our labor," said Col. Nina Armagno, 30th Space Wing commander. "I am so proud of our team for coming together to execute this landing operation safely and successfully."

Launched atop an Atlas 5 rocket from Cape Canaveral on March 5, 2011, shrouded inside the booster's nose cone for the flight through the atmosphere, the winged craft was inserted into low-Earth-orbit where it operated in secret to carry out a research mission with a classified payload.

Its pickup truck-size cargo bay, seven feet long and four feet wide, could have been filled with equipment being exposed to the harsh environment of space for proof testing or could have contained experimental instruments intended for use by future military and reconnaissance satellites. The craft's unique capability to drop from orbit and land on a runway allows technicians to get their hands on the hardware after it spent more than a year in space.

"We're in a very serious and important business in providing national security space capabilities for our nation. As you well know, some of those technologies are state of the art, highly complex, very technical and our ability to examine those technologies before they're made operational is a long sought after capability," Richard McKinney, deputy under secretary of the Air Force for space programs, explained following the OTV-1 landing.

"Now we can test those capabilities well in advance of putting them in operational. So rather than having it go up for the first time and do an operational mission, we could actually test those capabilities."

Wild speculation about the spaceplanes and their missions has ranged from secret flyby surveillance of China's orbital station to the weaponization of space.

"I appreciate the innovation and creativity of some people, but this is a test bed," McKinney said after OTV-1. "We're going to use this to put experiments on orbit. We're going to check them out. We're going to test them and we're going to bring them back. That's what this is."

Built by Boeing's Phantom Works division, the spaceplane is 29 feet long with a wing span of 15 feet, made of light-weight composite structures instead of aluminum and shielded with improved leading-edge ceramic insulation panels on its wings and tougher silica tiles affixed to its belly that are designed to be more durable than first-generation tiles used on the space shuttle. It can weigh up to 11,000 pounds fueled for launch. The in-space design life is 270 days, but good performance on this mission enabled ground controllers to keep it aloft significantly longer.

Unlike the space shuttles that used cryogenic liquid hydrogen and liquid oxygen reactants to generate electricity through onboard fuel cells, limiting the mission lengths by the amount of consumables that could be carried, the OTV is powered by a deployable solar array. The longest shuttle flight was 18 days.

Hobbyist satellite trackers closely monitored the vehicle since its launch last spring, watching it in an initial 206-mile (331 km) orbit inclined 42.8 degrees to the equator. Last summer, the orbit was raised slightly to 209 miles (337 km).

"It maintained this altitude against the effects of drag through frequent small orbit maneuvers," said Ted Molczan, a respected satellite observer.

In May, however, the craft began lowering its altitude, briefly slipping out of the trackers' sight until being discovered in the new orbit of 182 miles (293 km) tiled 41.9 degrees relative to the equator.

The new orbit caused its ground track to repeat, almost precisely, every three days; the previous altitude repeated every two days. Molczan said satellites with ground tracks repeating at intervals of two, three or four days have long been favored for U.S. imagery intelligence satellites, potentially offering a clue to the craft's payload.

"We want to be able to put an object up into space, materials and technology and so forth, test them out, bring them back and examine them," McKinney said after the OTV-1 mission. "That's what it is, pure and simple."

This was the second of the Orbital Test Vehicles to fly in the X-37B program, following the inaugural voyage that spent 224 days in space from April to December 2010, frequently maneuvering in what was considered to be a shakedown cruise to demonstrate the spaceplane's capabilities.

On the occasion of OTV-2 surpassing the first vehicle's mission duration, Lt. Col. Tom McIntyre, the program manager, said the second spaceplane was expanding the platform's envelope.

"This successful flight is important in the progression of the X-37B program, moving us forward in our effort to prove the utility and cost-effectiveness of an unmanned, long-duration, reusable spacecraft."

The original vehicle has been refurbished for shipment back to Cape Canaveral and a return to space. Another United Launch Alliance Atlas 5 rocket will haul that craft to orbit in a liftoff now targeted for October.

"The exact number of X-37 missions has yet to be determined, but we anticipate that multiple missions will be required to meet the program objectives and validate the technologies of interest," Bunko said this month.

The cost of the OTV program is classified.

"It's a test bed, it's a platform, it's an experiment process that we just didn't have before," McKinney said previously. "I think it opens up a whole new realm of possibilities in terms of being able to prove out new technologies and new materials."