The Northrop HL-10 was one of five US heavyweight lifting body designs flown at NASA's Flight Research Center (FRC—later Dryden Flight Research Center) in 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. It was a NASA design and was built to evaluate "inverted airfoil" lifting body and delta planform. It currently is on display at the entrance to the Armstrong Flight Research Center at Edwards Air Force Base. Development Northrop Corporation built the HL-10 and Northrop M2-F2, the first two of the fleet of "heavy" lifting bodies flown by the NASA Flight Research Center. The contract for construction of the HL-10 and the M2-F2 was $1.8 million. "HL" stands for horizontal landing, and "10" refers to the tenth design studied by engineers at NASA's Langley Research Center, Hampton, Virginia. Main gear was a modified T-38 system retracted manually, and lowered by nitrogen pressure. Nose gear was a modified T-39 unit, retracted manually and lowered with nitrogen pressure. Pilot Ejection System was a modified F-106 system. Silver zinc batteries provided electrical power for the control system, flight instruments, radios, cockpit heat, and stability augmentation system. To assist in pre-landing flare, four throttleable hydrogen peroxide rockets provided up to 400 lbf (1.8 kN) of thrust. Operational history After delivery to NASA in January 1966, the HL-10 made its first flight on December 22, 1966, with research pilot Bruce Peterson in the cockpit. Although the XLR-11 rocket engine (same type used in the Bell X-1) was installed, the first 11 drops from the B-52 launch aircraft were unpowered glide flights to assess handling qualities, stability, and control. In the end, the HL-10 was judged to be the best handling of the three original heavy-weight lifting bodies (M2-F2/F3, HL-10, X-24A). 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 February 18, 1970, Air Force test pilot Peter Hoag piloted the HL-10 to Mach 1.86 (). Nine days later, NASA pilot William H. "Bill" Dana flew the vehicle to , which became the highest altitude reached in the program. During a typical lifting body flight, the B-52—with the research vehicle attached to the pylon mount on the right wing between the fuselage and inboard engine pod—flew to a