Analysis of Thermally Induced Disturbances of a Gossamer Composite Boom
Sickinger, C
German Aerospace Center

Thermally induced disturbances are a general risk for very light Gossamer space systems. For example, the first generation of the deployable solar arrays of the Hubble space telescope develop a significant level of thermal excitation to the spacecraft, especially at the transition zones between light and shadow; these arrays were composed of flexible solar blankets and supporting Bi-STEM booms. Steep temperature gradients and rapid temperature changes cause the initiation of large deflections and thermo-elastic jitter.

This is particularly true for Gossamer systems which have a very large surface and, in contrast to this, low thermal mass. In the given presentation the design of a 35m long low-CTE (coefficient of thermal expansion) composite boom is being analysed as a structural member of a Gossamer-like application, such as solar sails, antennas, or solar arrays. The boom design is mainly driven by the requirement to minimise thermo-elastic effects. Consequently, the composition of the laminate stacking sequence and the boom surface were selected to minimise the thermal elongation along the boom's length and the thermal gradients over the cross section, respectively. However, uncertainties such as lay-up angle scatter could result in significant deviations from the nominal material properties and, therefore, the thermo-mechanical performance. Probabilistic analyses have been used to evaluate the boom design over the requirements. The presentation will give a general verification approach by analysis to cope with the aspect of thermally induced disturbances. Factors of safety will be derived on base of Monte Carlo simulations. In addition, an analysis approach of the thermally induced oscillation of the 35m long composite boom in cantilever configuration will be introduced.