 The CBM concept itself began to emerge with the first studies of the program in the early 1980s, experienced multiple iterations of concept, and completed development shortly before launch of the first flight element as the 1990s drew to a close.The CBM is just one branch in the long evolution of the United States' ability to assemble large spacecraft.At least as early as the late 1950s, the capability had been recognized as “...necessary for building space stations and assembling vehicles in low Earth orbit...”.