This paper describes the modeling, analysis, and testing done to determine the DS1 nutation time constant. The significance of this analysis and testing program is that Deep Space One was the first spacecraft flown by JPL with a diaphragm tank located on the spin axis. First, modeling considerations are made, and in order to simulate the nonlinear behavior of the spacecraft containing the liquid (Hydrazine), the dynamics of a rigid body coupled through a universal joint to a pendulum mass representing the liquid slosh has been analyzed. This nonlinear simulation is done in order to estimate the nutation time constant with a pendulum slosh model. Second, some considerations follow on the modeling of tanks with diaphragms in spinner tanks. Third, the actual spin drop tests are described. These tests also confirm a nutation time constant in excess of 1000 seconds, both in the case of tests done for the Xenon tank only and in the case of tests done for the Hydrazine tank only. The large value of the nutation time constant computed and verified by testing for this system ensured that it remained well above the required values of 150 seconds at ignition, and 50 seconds at burnout.
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