Search Results

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).

As a consequence of the continuously increasing complexity of design, development and qualification of modern spacecraft subsystems, computer aided tools become increasingly important for solving the various engineering tasks in these fields. In the framework of development tasks for satellites and space stations, e.g. ERS-I/II, ROSAT, CLUSTER, SOHO, COLUMBUS-ECLSS, and HERMES a software environment has been developed at Dornier GmbH in recent years, which allows thermal analysis, thermal control and space environment control for system simulation as well as for detained component level simulation, monitoring and testdata evaluation. COSITHERM is a modular software package for the prediction of thermal radiation effects. SIMTAS can be used for detailed analysis of single system components as well as for the prediction of system response of arbitrarily connect components.

Electro emissive devices, called ESTHER, are thin sheets - similar to solar cells - whose infrared emissivity can be varied reversibely by electrical charging. Bonded to external surfaces of spacecraft radiators, they allow active control of the heat radiated to space while consuming negligible electrical energy. Applying this novel component for spacecraft thermal control, considerable cost savings in spacecraft development and operation can be achieved. Progress in the design and manufacturing process has been made since the first puplication in July '92 /1/ revealing an increased variability of emissivity and an increased duty cycle stability. The material selection process was facilitated by the exposure of material samples to the space environment during two spaceflight missions and the subsequent material analyses.

Electroemissive (ESTHER) devices are thin sheets - similar to solar cells - whose infrared emissivity can be varied reversibly by electrical charging. Bonded to the external surfaces of spacecraft radiators they can be used for the active control of the Irradiated heat by consuming negligible electrical energy. The window to a revolutionary new thermal control design technology for spacecraft may be opened.

ESABASE/SUNLIGHT is a software tool to calculate illumination, effective illumination, exposure time, incident electromagnetic power, absorbed electromagnetic energy for spacecraft surfaces during planet orbiting missions considering sun and planet irradiation, effects of eclipse and self-shading, multireflections, transmission, pointing and (variable) geometry. Calculation applies a fast Monte Carlo raytracing algorithm and is based on wavelength dependent spectra and material properties. ESABASE/SUNLIGHT is fully integrated in the CAE-frame ESABASE which offers a powerful geometry specification language, orbit generator, pointing facility and advanced libraries as well as gateway, pre-, postprocessing and display tools with the benefits of standardisation and exchange to other analysis tools.

The redesign of the international Space Station Freedom (SSF) and funding constraints in the ESA member states caused a redirection of the development effort for the Attached Pressurised Module (APM). For the ECLSS the most important changes are the reduction in length of the module in order to make it compatible with the ARIANE V capabilities and the more severe cost constraints. As a result new concepts for the cabin loop were investigated leading to a decrease in cabin loop power consumption, mass and volume and a reduced development effort due to a lower number of items. In the previous concept a module internal loop with a flow rate of 864m3/hr and an Intermodule Ventilation (IMV) flow rate for air revitalisation to the station with 240m3/hr were installed. The revised boundary conditions with a reduced overall massflow rate of 540m3/hr allows the combination of the cabin loop and the IMV with limited impact on the total power consumption.

Manned space laboratories like the US Space Station Freedom or the european COLUMBUS APM are equipped with so-called racks for subsystem and payload accommodation. An important resource is air for cooling the unit internal heat sources, the avionics air. Each unit inside the rack must be supplied with sufficient amount of air to cool down the unit to the allowable maximum temperature. In the course of the COLUMBUS ECLSS project, a thermohydraulic mathematical model (THMM) of a representative COLUMBUS rack was developed to analyse and optimise the distribution of avionics air inside this rack. A sensitivity and accuracy study was performed to determine the accuracy range of the calculated avionics air flow rate distribution to the units. These calculations were then compared to measurement results gained in a rack airflow distribution test, which was performed with an equipped COLUMBUS subsystem rack to show the pressure distribution inside the rack.