Thermal design of the CFRP support struts for the spatial framework of the Herschel Space Observatory

Thermal finite element (FE) models, of low thermal conductance struts which are required to provide support for the low temperature components of the Herschel Space Observatory, have been validated by measurements at temperatures below 20 K. The Herschel Space Observatory structure is introduced. FE modelling of two designs of support strut is briefly discussed and the final designs presented. Validation of the design models was made in two experiments. The first of these provided specific thermal conductivity data for component CFRP materials, whose composition was initially designed on the basis of data available in the literature. The second experiment was performed to confirm the thermal conductance (Q′/ΔT), of the completed struts. The validation test rigs are described together with details of the experimental methods employed. Values of conductance were at the level of 5 × 10−5 W/K at a mean temperature of 6 K. The measured data are presented and discussed with reference to the thermal models. Sources of measurement inaccuracy, are also discussed.