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Northrop NASA HL-10
NASA research pilot Bill Dana watches as NASA's NB-52B flys overhead after a research flight in the HL-10. On the left, John Reeves can be seen at the cockpit of the HL-10.

Northrop NASA HL-10
Showing that not every moment of a test pilots life needs to be serious, NASA pilots Bill Dana (left) and John A. Manke try to drag Air Force test pilot Peter Hoag away from the HL-10 lifting body while Air Force Major Jerauld R. Gentry helps from the cockpit.

Northrop NASA HL-10
Northrop HL-10 rear view showing the various control surfaces

Northrop NASA HL-10
Northrop HL-10 parked on the ramp at NASA's Flight Research Center in 1966

Northrop NASA HL-10
NorthropHL-10 on lakebed

Northrop NASA HL-10
Northrop HL-10 landing

The HL-10 was a peculiar research aircraft built by the Northrop Corporation for NASA in 1966. "HL" stands for horizontal landing, and "10" refers to the tenth design studied by engineers at NASA's Langley Research Center in Hampton, Virginia.

The HL-10 was one of five heavyweight lifting-body designs flown at NASA's Flight Research Center (FRC - later Dryden Flight Research Center), Edwards, California, from July 1966 to November 1975 to study and validate the concept of safely maneuvering and landing a low lift-over-drag vehicle designed for reentry from space. The vehicle essentially had no wings and generated very little lift compared to a regular aircraft. What lift there was came about due to the overall shape of the body.

The HL-10 could not takeoff under its own power. Instead it was dropped from a B-52 mothership. After a series of 11 initial glide tests, the first powered flight occurred on October 23rd, 1968, the HL-10 used the same basic XLR-11 rocket engine that powered the original X-1s. A total of five powered flights were made before the HL-10 first flew supersonically on May 9, 1969, with John Manke in the pilot's seat.

The unusual shape of the aircraft, as well as the difficulties in performing comparatively low-speed landings, required a complex set of control surfaces. The rudders also served as speed brakes, allowing the pilot to adjust his speed during descent. Moving the flaps at the rear of the fuselage in the same direction pitched the nose up, while moving them in opposite directions rolled the vehicle to the right or left. After the first flights, the HL-10's fins were modified to improve its handling qualities. Once these changes were made the HL-10 displayed the best handling characteristics of the original heavyweight lifting body aircraft.

The HL-10 was flown 37 times during the lifting body research program and logged the highest altitude and fastest speed in the Lifting Body program. On Feb. 18, 1970, Air Force test pilot Peter Hoag piloted the HL-10 to Mach 1.86 (1,228 mph). Nine days later, NASA pilot Bill Dana flew the vehicle to 90,030 feet, which became the highest altitude reached in the program.

The four principal HL-10 pilots were Air Force Major Jerauld R. Gentry, Air Force test pilot Peter Hoag, and NASA pilots John A. Manke and Bill Dana.

Thanks to the lessons learnt through the HL-10 and the Lifting Body program, NASA engineers had some points of reference when it came to designing the Space Shuttle and figuring out how to make a safe landing with an unpowered aircraft with relativley poor aerodynamic qualities.

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