The USA also put considerable effort into the creation of lifting-body vehicles as the design precursors of manned re-entry vehicles. These lifting-body vehicles were intended to prove the viability of wingless flying machines that could re-enter the atmosphere at hypersonic speed after orbital flight and fly back to their bases. The two main protagonists of such vehicles were Martin Marietta and Northrop, the former with the X-24, and the latter with the M2-F2 and HL-10. In mid-1964 the US National Aeronautics and Space Administration (NASA) contracted Northrop to produce the M2-F2 and HL-10. The HL-10 was similar to the M2-F2 in most respects other than the camber of its D-section lifting body. On the M2-F2 the flat and curved surfaces were on the top and bottom respectively, but on the HL-10 these positions were reversed.
The HL-10, powered by the XLR-11 rocket engine, was dropped from beneath the wing of a Boeing B-52 on 22 December 1966. The first powered flight using rockets was made by the HL-10 from a B-52 on 13 November 1968.
Major Jerauld Gentry standing in front of the HL-10
Engine: Thiokol (Reaction Motors) liquid-propellant rocket, 8,000 lb (3,630 kg) st
Max width: 15 ft 1 in (4.60 m) between fin tips
Length: 22 ft 2 in (6.76 m)
Planform area: 162 sq ft (15.05 sq.m)
Max launching wt: 9,400 lb (4,265 kg)
Max landing wt: 8,000 lb (3,630 kg)
Max speed achieved: Mach 1.9
Max altitude achieved: 27430m