On the dynamics of non-rigid asteroid rotation

TL;DR

This paper introduces a new analytical method for modeling the final spin state of non-rigid asteroids, considering energy dissipation and angular momentum conservation, with solutions involving Riccati equations for the asteroid's rotational components.

Contribution

It presents a novel solving procedure for asteroid rotation dynamics that accounts for energy dissipation and provides analytical solutions using Riccati equations.

Findings

The rotation evolves towards a state with minimal energy at fixed angular momentum.

The second component of angular momentum satisfies a Riccati differential equation.

The third component can be derived from the second component's solution.

Abstract

We have presented in this communication a new solving procedure for the dynamics of non-rigid asteroid rotation, considering the final spin state of rotation for a small celestial body (asteroid). The last condition means the ultimate absence of the applied external torques (including short-term effect from torques during collisions, long-term YORP effect, etc.). Fundamental law of angular momentum conservation has been used for the aforementioned solving procedure. The system of Euler equations for dynamics of non-rigid asteroid rotation has been explored with regard to the existence of an analytic way of presentation of the approximated solution. Despite of various perturbations (such as collisions, YORP effect) which destabilize the rotation of asteroid via deviating from the current spin state, the inelastic (mainly, tidal) dissipation reduces kinetic energy of asteroid. So, evolution of the spinning asteroid should be resulting by the rotation about maximal-inertia axis with the proper spin state corresponding to minimal energy with a fixed angular momentum. Basing on the aforesaid assumption (component K_1 is supposed to be fluctuating near the given appropriate constant of the fixed angular momentum), we have obtained that 2-nd component K_2 is the solution of appropriate Riccati ordinary differential equation of 1-st order, whereas component K_3 should be determined via expression for K_2.