QUOTE : First consider the human systems and mission objectives when planning human space exploration. Understand what the mission is trying to accomplish and the duration. Design from the inside-out! Select the suits, cockpit/seats, EVA equipment and rovers, airlock, crew survival equipment, ECLSS, non-toxic fluids/gases/materials, crew quarters/hygiene systems, exercise equipment, water/air/waste recycling, quantity of food/water/oxygen, radiation protection, power source; then back out the spacecraft and launch vehicle that fit the items with +15% mass margin +10% volume margin. Dominant minds have prevailed in past space exploration architectures where a launch vehicle and spacecraft were proudly chosen prematurely, then when reality sets in; the same minds complain too much mass, too little volume, too high cost, and too long a schedule exist to fit their vehicles!