NEW YORK — After seven months in space, the U.S. Air Force’s X-37B unmanned space plane on Dec. 3 returned to Earth to wrap up a debut flight shrouded in secrecy.

The robotic X-37B space plane made a middle of the night landing at Vandenberg Air Force Base in California to end its maiden voyage. The space plane, also known as Orbital Test Vehicle 1, glided back to Earth over the Pacific Ocean before landing at the revamped Vandenberg runway at 1:16 a.m. PST.

“Today’s landing culminates a successful mission based on close teamwork between the 30th Space Wing, Boeing and the Air Force Rapid Capabilities Office,” said the Air Force’s X-37B program manager, Lt. Col. Troy Giese. “We are very pleased that the program completed all the on-orbit objectives for the first mission.”

In all, the X-37B space plane spent more than 220 days in orbit. Air Force Space Command announced Nov. 30 that the X-37B would land sometime between Dec. 3 and Dec. 6.

The Air Force has kept the exact nature and cost of the X-37B’s mission a closely guarded secret, but some analysts and skywatchers have speculated that the spacecraft served as an unmanned orbital spy platform.

One such expert is Brian Weeden, a former U.S. Air Force orbital analyst who serves as a technical adviser for the Secure World Foundation, a Superior, Colo.-based think tank. Weeden says the X-37B, like all reusable space planes, has a “lot of engineering and technical issues” that can limit its cost-effectiveness. But he still sees X-37B as a reasonably capable orbital space than can fill gaps in satellite coverage. “I would say that right now the space plane is probably more responsive in terms of meeting a warfighter’s [operationally responsive space] need than anything else we have,” he said. “But that depends a lot on the turnaround time.”

The Air Force could reconfigure the X-37B’s sensor payload for each mission, for example, to meet the emerging needs of military commanders or intelligence agencies to peek at certain parts of the world, Weeden suggested.

The X-37B also carries enough propellant to change orbit in the middle of a mission and thus change its coverage area on the fly.

Finally, the X-37B has a possible time advantage over a satellite in terms of launch preparations, Weeden said. Each satellite has a unique way of mating with the rocket that carries it into orbit, which can be a time issue on short notice. The Air Force could bypass that interface issue by installing the needed sensor payload into the standard body of the X-37B.


Robot space drone’s long flight

The Air Force launched the robot space plane atop a United Launch Alliance Atlas 5 rocket on April 22. Since then, the spacecraft has orbited Earth, at times tracked by meticulous skywatchers who first spotted the spacecraft in space with telescopes, then noticed its apparent maneuvers to change orbits. 

“This is a historical first, not only for Vandenberg Air Force Base, but for the Air Force and our nation to receive a recoverable spacecraft here and really take a step forward in advancing unmanned space flight,” Air Force Col. Richard Boltz, commander of the 30th Space Wing, said in a statement before the landing.

The X-37B space drone is a robotic winged spacecraft that looks in many ways like a miniature space shuttle. It was built by Boeing’s Phantom Works Division in Seal Beach, Calif., and can fly long, extended missions because of its solar array power system, which allows it to stay in orbit for up to 270 days, Air Force officials have said.

The X-37B started out as a fairly ambitious NASA project designated X-37. In 1999, NASA and Boeing signed a $173 million cooperative agreement to jointly develop the vehicle. NASA stopped funding X-37 before the vehicle had flown its first space mission.

Susan Turner, former deputy manager for NASA’s X-37 program, said while the Air Force took an early interest in X-37 as a possible space maneuvering vehicle, NASA’s driving interest was advancing the technological readiness of reusable space vehicles in general. As such, NASA loaded the X-37 with a batch of technologies, including an automated re-entry and landing system. NASA also called for flight controls driven entirely by electro-mechanical actuators, eliminating the bulky hydraulic circuits in normal control systems. New thermal tiles were required to protect the X-37 against the fiery heat of re-entry because of its steeper inclination approach compared with the space shuttle. The heat load also rises because of the X-37’s smaller size, which means less surface area to bleed off heat. The X-37 was one of several ultimately abandoned X-vehicle programs NASA began in the 1990s with the goal of fielding a next-generation space shuttle capable of runway takeoffs and landings.

“We were going to fill the sky with X-planes,” Turner recalled in an interview earlier this year. She is currently with the engineering directorate at NASA’s Marshall Space Flight Center in Huntsville, Ala.

But the X-37 managed to survive as a NASA project only until 2004, when then-U.S. President George W. Bush announced his Moon-centered Vision for Space Exploration that abandoned space planes for tried and true rocket-launched capsule designs.

NASA eventually transferred the X-37 to the U.S. Defense Advanced Research Projects Agency, which in turn handed off the project to the Air Force in 2006.


X-37B’s mystery mission

Air Force officials have said the X-37B Orbital Test Vehicle 1 is being used to demonstrate and test guidance, navigation and control systems, as well as evaluate autonomous landing techniques for winged spacecraft. Details about any experimental payloads on the spacecraft are classified, Air Force officials have said.

Before the April launch of the Orbital Test Vehicle 1 flight, Gary Payton, then the Air Force’s deputy undersecretary of space programs, said that the X-37B is not a space weapon.

“I don’t know how this could be called a weaponization of space,” Payton told reporters at the time. “Fundamentally, it’s just an updated version of the space shuttle kinds of activities in space.”

But some facts about the X-37B spacecraft are well known.

For example, the spacecraft has two wings, a payload bay about the size of a pickup truck bed and black heat-resistant tiles to withstand the searing hot temperatures of atmospheric re-entry.

The X-37B is about 9 meters long and has a wingspan of just over 4 meters across. It stands just over 3 meters tall and weighs about 5,000 kilograms.

The X-37B launches like a rocket and glides back to Earth like NASA’s space shuttles, but instead of a single tail fin at the rear, the X-37B has two stabilizers, called “ruddervators,” sprouting up in a V shape.

The vehicle also was equipped with a destruct mechanism, so Air Force officials could destroy it by remote control if it veered off course while gliding over the Pacific Ocean toward the Vandenberg Air Force Base.


Robot space plane’s return

To prepare for the mini-shuttle’s landing, a huge team of workers had to replace some 658 steel plates along the centerline of Vandenberg’s nearly 4,600-meter runway because the older ones could pose a hazard to the X-37B vehicle’s tires.

The Air Force has already ordered a second X-37B, the Orbital Test Vehicle 2, which is slated to launch on another test flight sometime in the spring of 2011.

But for now, Air Force officials said they were ecstatic to see the successful return of the first X-37B spacecraft.

“With it being such a unique mission for the base, it is exciting to be a part of this historic landing,” said Air Force Capt. Dariusz Wudarzewski, 2nd Range Operations Squadron commander. “For how long we have been working on it, I think everyone is really excited to see it culminate.”



U.S. Air Force Official Touts Space Plane Applications