A model is being developed to quantitatively compare and select systems and technology options for defined missions envisioned in the National Aeronautics and Space Administration's (NASA's) Space Exploration Initiative. It consists of a modular, top-down hierarchical break-down of the life support system (LSS) into subsystems, and further break-down of subsystems into functional elements representing individual processing technologies. A series of papers titled “Human Life Support During Interplanetary Travel and Domicile” was planned to describe the technique and results. Part I, presented at the 19th ICES Conference, described the system approach. Parts II, III, and IV are presented at this conference. Part II describes the modeling technique. Part III describes results of a system trade study for a Mars Expedition Mission comparing open and closed loop systems. Part IV, this paper, describes results of trading processing technologies in a closed loop configuration for the Mars Expedition Mission in terms of weight and power. The technologies were chosen from those being considered for Space Station Freedom and represent only physical/chemical technologies. Technologies were traded and compared to a baseline set for the following functional elements: CO2 Removal, CO2 Reduction, H2O Electrolysis, Potable H2O Cleanup, Hygiene H2O Cleanup, and Urine Processing.