On the Dynamics of a Nutation Ring Damper

TL;DR

This paper analyzes the dynamics of a nutation ring damper in spinning satellites, combining theoretical mechanics and CFD simulations to understand energy dissipation and decay of nutation in CubeSat applications.

Contribution

It introduces a comprehensive theoretical model of a viscous fluid ring damper, extending from a point mass to a distributed slug, and validates findings with CFD simulations.

Findings

The system's equilibrium points are characterized on the angular momentum sphere.

The damping effect leads to a decay in nutation angle over time.

CFD simulations support the theoretical energy dissipation estimates.

Abstract

Nutation triggered by external disturbances is an undesirable phenomenon for a spinning satellite. Passive decay in nutation angle must be achieved in such cases and benefits missions involving spin-stabilized satellites or mass-constrained satellites like CubeSats. Motivated by previous work of other authors, the dynamics of a general nutating satellite with an attached ring containing a viscous fluid is analyzed in a theoretical mechanics framework. The fluid in the ring is modeled as a rigid point mass and is then extended to a distributed rigid slug. The nonlinear equations of motion of the system, under the assumption of zero external torques, are studied in a body-fixed frame. Equilibrium points and system trajectories are studied on the angular momentum sphere. The settling time of the dynamical system after an initial disturbance is investigated. The energy dissipation is modeled using an approximate drag coefficient. Fluid dynamic effects are further examined through CFD simulations in the Navier-Stokes setting using the open-source software package ANSYS Fluent. Applications of the analysis and simulations to CubeSats are discussed.