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Every ecosystem, whether natural or man-made, has a natural tendency to increase its organisational level inducing a maximal utilisation of its resources and consequently, minimising the net output from the system. In order to obtain useful net output from an ecosystem, therefore, it is necessary to stop and to stabilise the evolution at an intermediate organisational level by proper control. “Ecological” life support systems for manned space missions will be required to maximise productivity and safety whilst at the same time respecting tight size constraints, which implies powerful control and regulation systems. However the behaviour of complex ecosystems is relatively poorly understood, their stability/evolution is greatly influenced by intrinsic internal controls and classical control theories cannot be easily applied.

This paper discusses the capabilities of the ECOSIM software which is currently under development for the European Space Agency. This software is primarily intended to simulate Environmental Control and Life Support (ECLS) systems. It may be also customised to the simulation of passive and active thermal control systems, power systems, and more generally any system which can be described as a set of interconnected physical components. ECOSIM shall provide a powerful continuous simulation language, a graphical user interface and a library of ECLSS custom-made components. After a brief overview of the major aims of the development, the software is discussed from its main aspects, the language and its mathematical formalism, the graphical user interface, and the ECLS systems customisation for representing the physical, chemical, and biological processes of interest. Examples are provided aiming at enhancing the understanding of the critical aspects of the language and the user interface.

Based on the thermal requirements of future large European platforms such as the Columbus Space Station, several developments in the field of two-phase flow systems were initiated over the last few years in Europe. This paper will give a general overview of the objectives, development status and test results of an ESA-funded ‘Two-phase heat transport system’ study and of two studies sponsored by the German Ministry of Research and Technology on two-phase heat transport. The ESA two-phase loop system resulting from the concept trade-off is driven by an electrically powered liquid pump and is provided with a capillary cold plate and an evaporative heat exchanger mounted in parallel. Under certain conditions, a simplified version of this type of system is able to work in a capillary-pumped mode. The system is designed for a heat load of 10-20 KW, a length of 20 m, a working temperature around 20°C and R114 as working fluid.