Artist's concept showing one HL-20 lifting body docked with Freedom and one on its return trip to Earth. 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 asure rapid manned acces 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. The Freedom Space Station concept eventually became the International Space Station (Is). Construction of the Is began in 1998 and the first crew arrived in 2000.
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