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This work concerns the model of a biological life support system consisting of higher plants, a unit of “biological combustion”, a physicochemical reactor, and 1/30 of a human. The cycling of the main biogenic elements of the system, water, and carbon dioxide was closed to a high degree (more than 95%). Experimental-theoretical analysis of the cycling processes in the system was based on the calculations of mass exchange rates dynamics and some stoichiometric equations. The model was designed for the study of mechanisms of material transformation and the directions of mass exchange processes in the artificial ecosystems.

EcosimPro‘s capability to solve a problem domain that can be represented by Differential-Algebraic Equations (DAE) and discrete events, make it particularly attractive to model bio-regenerative life support systems. Components of the envisaged MELiSSA bio-regenerative life support system are driven by the adaptation of the biomass to changing environmental conditions, which could be of continuous nature, such as depletion or replenishment of nutrition, and discrete events, such as step changes in light fluxes and control interactions. The authors first present simulation results for a closed and an open loop bio-regenerative system. The simulations include the establishment of a quasi-steady state, reaction to step changes including a mass balance check, and the simulation of a controlled bioreactor. The results demonstrate the capability of this tool to model components of a bio-regenerative life support system, as well as an entire bio-regenerative life support system in the future.

The MELISSA (Microbial Ecological LIfe Support System Alternative) project has been set up to be a model for the studies on ecological life support systems for long term space missions. The compartmentalisation of the loop, the choice of the micro-organisms and the axenic conditions have been selected in order to simplify the behaviour of this artificial ecosystem and allow a deterministic and engineering approach. In this framework the MELISSA project has now been running since beginning 1989. In this paper we present the general approach of the study, the scientific results obtained on each independent compartment (mass balance, growth kinetics, limitations, compound conversions,..), the tests of toxicity already performed between some compartments and their effect on the growth kinetics. The technical results on instrumentation and control aspects, and the current status of the ESA/ESTEC hardware are also reviewed.