This report summarizes a trade study of different options of a bioregenerative Life Support System (LSS) and a subsequent conceptual
design of a hybrid LSS. The evaluation was based mainly on the terrestrial testbed projects MELISSA (ESA) and BIOS
(Russia). In addition, some methods suggested by the Advanced Life Support Project (NASA) were considered. Computer models,
including mass flows were established for each of the systems with the goal of closing system loops to the extent possible. In order to
cope with the differences in the supported crew size and provided nutrition, all systems were scaled for supporting a crew of six for a
780 day Mars mission (180 days transport to Mars; 600 days surface period) as given in the NASA Design Reference Mission Scenario
[Hoffman, S.J., Kaplan, D.L. Human exploration of Mars: the Reference Mission of the NASA Mars Exploratory Study,
1997]. All models were scaled to provide the same daily allowances, as of calories, to the crew. Equivalent System Mass (ESM) analysis
was used to compare the investigated system models against each other. Following the comparison of the terrestrial systems, the
system specific subsystem options for Food Supply, Solid Waste Processing, Water Management and Atmosphere Revitalization
were evaluated in a separate trade study. The best subsystem technologies from the trade study were integrated into an overall design
solution based on mass flow relationships. The optimized LSS is mainly a bioregenerative system, complemented by a few physicochemical
elements, with a total ESM of 18,088 kg, which is about 4 times higher than that of a pure physico-chemical LSS, as
designed in an earlier study