NASA and the Air Force are currently considering Space Station concepts which feature a wide variety of manned activities including payload operations, command and control, large system deployment, geo-vehicle buildup, and spacecraft servicing and launch. This paper identifies potential mission operations and objectives for these concepts and defines the related crew tasks. Relationships are presented between crew and station operational capabilities. An Environmental Control Life Support Subsystem (ECLSS) is defined and design impacts are identified for each mission type. Crew requirements are synthesized and ECLSS characteristics are presented for each mission type.