Free-flights of Air Force X-40A test vehicle planned as part of NASA's X-37 flight demonstrator program

The first of up to seven free-flight tests of the X-40A, an 85 percent scale version of NASA's X-37 technology demonstrator, is planned to begin this week at the Dryden Flight Research Center at Edwards, Calif.

NASA and its industry partner The Boeing Company are using the X-40A, on loan from the U.S. Air Force, as part of its risk mitigation activities for the X-37 program. It will help test the shape, guidance and other systems for the X-37. Flight objectives include validation of Computed Air Data Systems (CADS), which will be used in the flight control system of the X-37.

Other test points are: in-flight performance evaluation of the Honeywell SIGI Space Integrated Global Positioning System Inertial Navigation System; test of control Room Operations; and flight test of guidance, navigation and control software.

"These tests with the X-40A will provide us a great deal of valuable data applicable to the X-37," said Dick Cervisi, Boeing Phantom Works X-37 program manager. "Performing these tests will significantly reduce the risk to be encountered in the X-37 flight program."

The X-40A will be lifted by a U.S. Army Chinook helicopter to an altitude of 15,000 feet above ground level and released to glide to a runway landing, guided by on-board systems. The free-flight will take approximately 75 seconds from release to landing. The vehicle will reach a velocity of up to about 200 miles per hour (168 knots).

Six captive-carry flights -- when a vehicle is tethered to an aircraft but not released -- of the X-40A by the Chinook helicopter have been conducted at Dryden. Each flight averaged one hour and 40 minutes, at an elevation of 15,000 feet (about 4.6 kilometers) and speed of 108 miles per hour (about 90 knots). Those flights validated the functionality and performance of the X-40A's guidance, navigation and control systems, air-data and telemetry.

The X-40A test vehicle was built for the Air Force by The Boeing Company at its Seal Beach, Calif., facility. It has a fuselage length of 22 feet (about 6.7 meters), a wing span of 12 feet (about 3.65 meters) and weighs about 2,600 pounds (about 1179 kilograms). It was flight tested once before, in August 1998 at Holloman Air Force Base in southern New Mexico, for the Air Force's Space Maneuver Vehicle program.

Although Boeing performed a number of modifications to the X-40A in preparation for the current tests, including improved instrumentation and telemetry, a new integrated inertial navigation system/global positioning system (INS/GPS) payload, upgraded power systems and additional redundancy for range safety, the flight control system remains single string. Inherently, a single string system is not as reliable as the fault-tolerant system planned for the X-37.

The X-37, managed for NASA by the Marshall Space Flight Center in Huntsville, Ala., 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.

The X-37, carried into orbit by the Space Shuttle, is planned to fly two orbital missions beginning in 2003.

The X-37 government team, led by the Marshall Center, includes NASA's Ames Research Center in Mountain View, Calif.; Johnson Space Flight Center in Houston, Texas; Kennedy Space Center at Cape Canaveral, Fla.; Goddard Space Flight Center in Greenbelt, Md.; Langley Research Center in Hampton, Va.; Dryden Flight Research Center and the Air Force Flight Test Center, both at Edwards Air Force Base in Edwards, Calif.; and the Space and Missile Systems Center and the Air Force Research Laboratory in Albuquerque, N.M. The X-37 industry team is led by Boeing at Seal Beach, Calif.