Computer modeling of top-level advanced life support systems (ALSS) has been initiated with completion of a prototype model of the biomass production component (BPC). Object oriented analysis and design were utilized to develop a flexible programming structure capable of expansion and incorporation with other components of the ALSS model. The biomass production model (BPM) has a world wide web (WWW) -accessible user interface which facilitates data viewing, modification, and input. Users utilize default values in the existing database or enter data specific to a scenario under consideration. The BPM simulates production of multiple crops within controlled environments, tracking automation, labor, production of edible and inedible biomass, and resource needs. At the conclusion of a simulation run, graphs showing the history of key variable values are available for the user to view on the monitor. This paper focuses on design and implementation the BPM.