ELISSA – a Comprehensive Software Package for ECLSS Technology Selection, Modelling and Simulation for Human Spaceflight Missions

The software tool ELISSA (Environment for Life-Support Systems Simulation and Analysis) is being developed at the Institute of Space Systems (IRS), University of Stuttgart since the mid-90s and allows the analysis and validation of new ECLSS designs, as well as system optimization. The time-discrete simulation tool offers a wide library of both physico-chemical and biological components for air, water, food and waste management, with special focus on potential components for future long duration missions. The components have been modeled, depending on their Technology Readiness Level (TRL) and current available reference data, either from specifications of existing technologies, experimental data or from physical/chemical fundamentals from the literature. As a result, some components are model as a detailed dynamic process, whereas others are represented as a static process. The ELISSA components library is constantly being updated with new components data, including real data from experiments, for example from the photobioreactor experiment currently being developed at IRS. The ELISSA user can select the components to be used for each ECLSS model and simulation as well as other mission specific parameters such as size of the crew, mission duration, initial consumables or tank sizes, through a user-friendly interface. The simulation results show the behavior of the system over the mission time, allowing to properly size the components, tanks and consumables for a specific mission. ELISSA provides the Equivalent System Mass (ESM) in order to compare different ECLSS designs. To complement ELISSA, two other tools have been developed: PrELISSA, which enables the comparison of a large number of components combinations for a first model design selection and Reliability ELISSA, which allows the evaluation of the reliability at different system levels considering the use of spare parts. The entire ECLSS reliability is the result of a complex time-discrete stochastic simulation.