The development of regenerative life support systems (RLSS) to support long duration manned space exploration is of great importance. To design future chambers effectively, it is necessary to model both chamber performance and plant growth in current systems. The Johnson Space Center RLSS test bed, which consists of the Variable Pressure Growth Chamber (VPGC) and the Ambient Pressure Growth Chamber (APGC), is a facility that is being used to investigate plant growth and support hardware integration. Detailed and simplified models of the VPGC and APGC have been developed to investigate system performance and response to changes in loading as well as to study long-term plant growth under varying environmental conditions, including temperature, light level, CO2 level, dew point or relative humidity, and photoperiod. To support these studies, models of two crops, lettuce and wheat, have also been developed and integrated into the detailed and simplified simulations of each chamber. This paper will discuss the results of the development effort of the analytical simulations of the VPGC and APGC and compare the data from three previous crop growth experiments against model predictions.