McDonnell Douglas DC-X
 The DC-X short for Delta Clipper or Delta Clipper Experimental was an unmanned prototype of a reusable single stage to orbit launch vehicle built by McDonnell Douglas in conjunction with the United States Department of Defense's Strategic Defense Initiative Organization (SDIO) from 1991 to 1993. Starting 1994 until 1995 testing continued through funding of the US civil space agency NASA.