Military Aviation | Air & Space Magazine
Will the Air Force Finally Get a Spaceplane?
If Boeing's X-37 can maneuver politically as well as in space.
Ben Iannotta
COUNTRY MUSIC SUDDENLY BLARES FROM UNSEEN LOUDSPEAKERS AS VETERAN Boeing manager Dennis Rainwater opens the door to a large, gymnasium-like room. Inside, a blue curtain blocks the view of the far side of the chamber.
NASA once considered using the space shuttle to carry the X-37 to orbit, but those plans changed. When the craft does go into space, it will most likely ride atop an expendable launcher.
(NASA/MARSHALL)
Photo Gallery Rainwater has to shout to be heard. "Behind the blue curtain is something you're not supposed to see," he yells.
Or hear, for that matter. The country crooning drowns out the conversations of people working on whatever is behind the curtain and disguises the sounds of tools that might be drilling, cutting, or grinding.
We're in Boeing's secretive High Desert Assembly Integration and Test facility, part of a complex known as the Phantom Works, in Palmdale, California. The facility is part of the Air Force's Plant 42, a collection of buildings where, historically, aerospace companies have worked on the projects that have made the United States the world leader in military and space technology. F-117 stealth fighters, B-2 stealth bombers, and space shuttle orbiters all sprang from Plant 42. Today, another technological push is taking place here. Lying on the unclassified side of this particular high bay is the partially assembled lower fuselage of a 28-foot-long experimental craft called the X-37. It is a technology demonstrator for a spacecraft that, launched on an expendable rocket, could eventually fly almost any of the missions of the bombers and orbiters that preceded it. At long last the Air Force would have the spaceplane it has pursued since the late 1950s.
It was named the Aerospaceplane when the 1950s designs first appeared. In the '60s, it became the X-20 Dyna-Soar. Secretary of Defense Robert McNamara canceled Dyna-Soar in 1963, before it ever flew, but the dream of a spaceplane survived through the next three decades in a series of studies and programs. The most ambitious was the National Aerospace Plane, a 1980s effort nicknamed the Orient Express (for its farfetched goal of carrying passengers from New York to Tokyo in two hours), but the technological leap it required overwhelmed the Air Force-NASA partnership formed to build it. The program dissipated into small technology development projects before being canceled altogether in 1992.
The direct antecedent of the Reusable Spaceplane was born in the early 1990s at the Air Force Research Laboratory at Kirtland Air Force Base in New Mexico. The program was called the Military Space Plane. Its advocates envisioned a craft that could do in space what an unmanned Predator reconnaissance aircraft and an E-3 Sentry Airborne Warning and Control System do in the air. In a crisis, the Pentagon would launch spacecraft called Space Maneuver Vehicles to return images of enemy positions, eavesdrop, coordinate air forces, and jam satellites. To accomplish such missions, the Space Maneuver Vehicles would do hat previous spacecraft have not been able to: change orbital planes and altitudes.
After a mission, each SMV would blaze back into the atmosphere toward a runway, where Air Force ground crews would scramble to refurbish it in hours or days in what Air Force planners call "aircraft-like operations." Space Maneuver Vehicles would be unpiloted, and, best of all, they would operate safely above surface-to-air missiles.
The Air Force Research Laboratory took an important step toward developing its spaceplane in 1996, when it hired Boeing to build the X-40, a 22-foot-long flight test vehicle. Made of a graphite/epoxy shell with an internal aluminum frame, the X-40 was to test the aerodynamic handling characteristics of a returning spacecraft and to prove that a small vehicle designed for reuse could land autonomously on a 10,000-foot runway. In 1998, Boeing dropped the unpiloted vehicle from a Black Hawk helicopter; it dove toward Holloman Air Force Base in New Mexico from an altitude of 9,000 feet and used its autonomous guidance, navigation, and control system to land successfully. Later, the Army Aviation Technical Test Center supplied Boeing with a CH-47 Chinook helicopter and pilots to conduct a series of seven test flights for NASA. The X-40, dropped from 15,000 feet, landed on Runway 22 at Edwards Air Force Base in California.
"We were not off on the lakebed; we were coming in with all the other airplanes," says Randy Hein, Boeing's X-40 program manager. "They cleared the airspace, but we were coming in on an operational runway, which was a neat thing to be able to do." As Hein speaks, the gleaming X-40 waits inside a storage facility at Boeing, like a Ferrari ready to be taken for another spin.
Hein and his team sweated out one moment during the first flight test at Holloman that captures the challenge of designing an aircraft to land without a pilot. "We had one touchdown where we lifted up and came back down - bounced, if you will," Hein says. The vehicle was undamaged, and the team's analysis quickly pinpointed the problem. When the X-40's tires touch down on the runway, the main gear tires spin up from zero to about 195 mph, creating a force that pushes the nose down. Piloted aircraft show the same nosedown tendency, and in training pilots learn how to compensate to keep the nose up on landing. In the X-40, flight software must compensate, and on the first landing, the X-40's automated control surfaces overcompensated (as more than one pilot has done), and the vehicle briefly lifted off. Boeing's engineers revised their computer model of the forces created by the tires' spin up and reprogrammed the flight software to increase the reaction rate of the control surfaces.
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