Nutation Time Constant Determination of On-Axis Diaphragm Tanks on Spinner Spacecraft

The modeling, analysis, and testing done to determine the Deep Space One nutation time constant are described. The significance of this analysis and testing program is that Deep Space One was the first spacecraft flown by the Jet Propulsion Laboratory with a diaphragm tank located on the spin axis. First, modeling considerations are made, and to simulate the 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 simulation is done in order to estimate the nutation time constant with a pendulum slosh model. Second, the actual spin drop tests are described. These tests also confirm a nutation time constant in excess of 1000 s, 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 s at ignition and 50 s at burnout.