Artist's concept showing an HL-20 lifting body atop a National Launch System. Developed by the Langley Research Center, the HL-20 was one of two concepts considered by NASA in the early 1990s as a type of Personnel Launch System (PLS). The PLS is a small 'space taxi' system which would assure rapid manned access to space and minimize maintenance costs. HL-20 was designed to be capable of runway landings and was intended to be able to fit within the payload bay of a Space Shuttle once its wings were folded.
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