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The Thermal design of the ENVISAT-1 ASAR Active Antenna has provided many engineering challenges. The selection of the Thermal Control has been complicated by the need to dissipate the high power (1300 watts) generated by the active equipments that are mounted on the Antenna Tile Sub-System directly behind the radiating surface. This high power has to be dissipated from the Antenna whilst minimising heater power consumption. The final design uses passive Thermal Control for dissipating the heat from the equipments during operating modes, via radiation from the Active face of the Antenna towards the Earth. This has required evaluations of possible Thermal finishes and resulted in a black painted Earth facing Active radiating face. Heat loss by conduction to the ENVISAT-1 platform has also been minimised in order to ensure that ASAR has negligible impact Thermally on the platform.

The ENVISAT ASAR antenna is 10 meters in length in the deployed configuration and consequently thermal balance testing was impossible due to TVAC chamber size and MGSE limitations. Therefore the verification of the ASAR active antenna thermal design was based mainly on analysis complemented, when necessary, by thermal balance tests at subsystem level on key components. This approach called up for extensive sensitivity analyses, taking into account the fact that all of the design, orbital parameters, operational scenario and mathematical simulation are subject to uncertainties. Special emphasis was put on assessing the impact of uncertainties on albedo and earthshine for low time constant components of the ASAR antenna which is facing the Earth.

This paper discusses the capabilities of the ABLAT software which has been developed by ERC and Dornier for the European Space Agency. The software provides an ablation modelling capability for the ESATAN thermal analyser and consists of two sections: i. A stand-alone preprocessor allowing specification of the ablation model. This has both an X11/OSF Motif and a command line interface. ii. An integrated solver capability within the ESATAN system, allowing transient analysis of an ablating surface in conjunction with a standard thermal model. After a brief overview of the major aims of the development, the software is discussed from two main points of view, the user interface facilities (how the user defines the model to the system), and the calculation facilities (what can be calculated, and how are these calculations performed).

ECOSIM is a software tool for the simulation of Environmental Control and Life Support (ECLS) systems which has been developed for the European Space Agency. A preliminary model of the Hermes Air Management System has been developed during the ECOSIM testing in order to assess the functionality of the software and to verify its results with those obtained from previous simulation tools. The model represents the Hermes cabin with its crew and it includes submodels for the sub-systems performing the following functions: Temperature and Humidity Control. Total Pressure and Composition Control. Air revitalisation. The interactions between these different subsystem are taken into account by the model, while many of the previous simulations made assumptions to decouple the different subsystems (e.g: a constant cabin temperature has been assumed during cabin depressurization transients, to decouple the pressure control section from the air conditioning section).

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.

FHTS is a major extension to the existing ESATAN thermal analyser. It is capable of carrying out one dimensional steady state or transient analysis, solving for pressure, temperature and mass flow rate, for single or two phase loops. This paper begins by giving an overview of the capabilities of FHTS and outlines the stringent quality assurance standards adhered to during its development. The coding standards ensure software verification during its development via module testing and the development of a test suite. Further verification of both the single phase and two phase capability has already been carried out by comparison against Retran, a well established package used throughout the Nuclear Industry. An outline of the results from this work and conclusions drawn is given. Although limited in scope the work proved extremely valuable.

The Fluid Heat Transport Systems (FHTS) extension to the ESATAN thermal analyser was released to industry in 1989. A significant as effort has been directed towards obtaining, far as possible, an error free code which gives results in reasonable agreement with reference data. The first steps to ensure confidence in FHTS have been taken by system testing during software acceptance and by means of a comparison with RETRAN, a US code unique in possessing a US safety evaluation report for reactor licensing applications. RETRAN output data was taken as the a priori reference data to verify FHTS. Two sets of test cases have been defined, one concerning single-phase problems (basically the Columbus water loop), the second set containing models with two-phase conditions (a simple idealised loop and boundary conditions). The paper highlights the difficulties encountered during the comparison work, presents the major results and discusses the main issues involved in FHTS verification/validation.

MANIP development aims at providing an interactive, integrated software environment for performing the thermal design of spacecrafts. The user of MANIP is expected to be a thermal engineer, not a programmer. This basic requirement determines the essence of MANIP and has a major impact on the requirements related to defining, refining and simulating a model, and subsequently analysing the simulation results. The paper highlights the main aspects of implementation and use.

Fluid loop modelling has been added to the capabilities of the thermal analyser ESATAN. Predictions of pressure and mass flow rate, in addition to the thermal solution, may now be obtained in one dimensional piped fluid networks. Such predictions may be steady state or transient, with single or homogeneous two phase flow. The user interface has been designed for compatibility with conventional ESATAN model input, by definition of fluid nodes and links. Predefined models of common fluid loop hardware are provided as part of the software package. Analysis may be all-fluid, all-thermal, or both fluid and thermal simultaneously.