Designing the Environmental Control and Life Support System (ECLSS) for exploration missions to the interplanetary space is a complex task beginning from the definition of the needs (e.g. diet, safety, radiation level,..) up to the selection of technology possibilities. In this context a major issue is the influence of crew number and mission duration to the ECLSS design. These are the main reasons why during mission studies the design of the ECLSS system mostly starts from scratch. Uncertainties about requirements, functions and technologies most suitable for the mission lead to a high number of iterations before a baseline design can be achieved. The aim of the SCALISS (Scaling of Life Support Systems) study was to understand and investigate in ECLSS functionality, technologies and scalabilities in order to produce a robust initial design starting point for future Phase-A studies with an automated tool. The developed Java-based ECLSS sizing tool is described in this paper together with the validation case study results. The possible evolutions and interactions with the ALiSSE tool are also described
