The NASA Space Station Program has recently undergone substantial changes, brought about by the future availability of the Space Shuttle as an earth-to-orbit transportation system. The assembly of a Modular Space Station in earth orbit from elements delivered by the Space Shuttle is feasible and can be accomplished in the late 1970f s or early 1980*s. Low transportation costs, return of modular elements for either refurbishment or update, and incremental growth are major advantages of the modular approach. Initially, a modest three- to six-man Station can be assembled in orbit and, over a period of years, evolve to a larger more sophisticated facility by adding modules and updating subsystems as technology advances
