Numerical and experimental activities in fluid/spacecraft interactive dynamics

Currently planned and future space missions impose increasingly demanding stability and pointing requirements on spacecraft systems. Perturbations due to large amounts of liquids on board cannot be ignored. The ability to understand, predict and control the dynamics of the moving liquid is essential. At NLR, both numerical and experimental methods are developed. These are used for studying the effects of fluids on spacecraft dynamics and serve as a basis for the development of a verified and validated interactive fiill fluid/spacecraft dynamics simulation. Numerical results were obtained for specific fluid/spacecraft configurations. Based on this work a verification and validation methodology approach, using succesive simulation steps of increased complexity, initiating from the two dimensional full tank case, was applied to the coupled rigid body dynamics model of Flow Science fluid flow analysis program FL0W-3D. Representative results of these numerical experimenit for simulation verifi cation are presented. As part of the NLR experimental activities in this field, the Wet Satellite Model (WSM) experiment was launched in April 1992 with the MASER-5 sounding rocket (ESA funded). After ejection of the WSM free-flyer from the rocket payload, an altitude of 312 Km was reached with a free fall time of 370 seconds. The experimental data as measured by a set of nine accelerometers and three pressure sensors were transmitted to the ground station. These experiment data are used in the process of validation of interactive fluid/spacecraft numerical simulation. A short description of the WSM experiment is presented. Based on the experience gained from the WSM program, the SLOSHSAT experimental mini-satellite for fluid dynamics study is resentiy being designed by NLR (with Fokker Space and Systems) for the European Space Agency (ESA). This Shuttle launched minispacecraft WU1 embody an instrumented experiment for fluid/spacecraft interactive dynamics. The SLOSHSAT spacecraft, its instrumentation and test program is described