Eight tasks were defined by NASA to fulfill the intent of those objectives; but tatter, at NASA direction, efforts were concentrated on "Experiments and Utilization and "Design of Modular Concepts," two of the original tasks. The other tasks were reduced in scope or terminated. The ultimate objectives of the program were conceptual investigation of a family of space stations utilizing- the modular, or building block, concept and integration of a broad spectrum of experiments and applications into this family of space stations. The study was a follow- on effort to "Study of a Rotating Manned Orbital Space Station," performed for MSC, by Lockheed. (See March 1964 entry.) The modular concept, as defined in the study, could be applied to a wide variety of missions and configurations, but only six missions using four configurations were developed: A 45-day mission, three-man crew, 370-km Orbit at 28.5-degree inclination ; one compartment laboratory. A l-year mission, six-man crew, 370-km orbit at 28.5-degree inclination; two compartment laboratory. A 90-day mission, three- to six-man crew,, 370-km orbit at 90-degree inclination; two compartment laboratory. A 90-day mission, three- to six-man crew, 35 900-km orbit at 30-degree inclination; two compartment laboratory. A 1- to 5-year mission, six- to nine-man crew, 370-km orbit at 28.5-degree inclination; interim station (six compartments). A 5- to 10-year mission, 24- to 36-man crew, 480-km orbit at 29.5-degree inclination; operational station (Y configuration). This investigation of the four configurations, as opposed to the study of a single design, dictated that Lockheed utilize a conceptual study approach and reduce or eliminate efforts not directly applicable to feasibility demonstration. Only major structural and mechanical designs were produced. Detailed design was limited to the depth necessary to ensure concept feasibility. Two groups of NASA-furnished experiments provided the basis for determining interior arrangements of individual stations: 85 priority I Apollo Extension Systems experiments for the one and two-compartment laboratories and 405 "Supplementary Applications" for the interim and operational stations. The experiments were briefly reviewed to define man-hour, power, weight, volume, types of equipment, and laboratory layout requirements. Principal guidelines were used to aid in defining the modular multipurpose space station: Use of state-of-the-art equipment was emphasized, but advanced subsystem concepts were considered and design flexibility maintained so equipment of advanced design could he incorporated w hen available and proven. In all cases, systematic growth potential was achieved without requirements for major developments or technical innovations. Utilization of identical components and equipment on as many of the stations as possible was stressed to reduce cost, complexity, and technical risk. Two basic structural module diameters were studied- the 465 cm and 660 cm and the advantages and disadvantages of the two sizes were compared in order to mate recommendations for a final choice. All configurations of the modular multipurpose space station would be launched from Cape Kennedy by Saturn launch vehicles. Meteoroid and radiation environment models were specified by MSC.