Design Considerations for Stability of Liquid Payload Projectiles

It is well known that projectiles equipped with liquid payloads experience large destabilizingmoments induced by internalmotion of the fluid. For some configurations, thesemomentsmay lead to catastrophicflight instabilities. This paper explores howpayload geometry, fluid spin-up rate, and themagnitude of launch perturbations affect the flight trajectories of projectiles with a liquid payload, including projectile instability. A dynamic simulation model is used in which a projectile rigid-body dynamics representation incorporates liquid moments generated from linearized Navier–Stokes predictions. A novel feature of this simulation is its use of linear filtering within the model, which determines fast- and slow-mode angle-of-attack contributions at each time step to be used in computation of liquid moments. Example cases and Monte Carlo simulations demonstrate how design factors and launch perturbations affect the projectile’s tendency to exhibit flight instability. The paper concludes with a summary of advantageous design characteristics that are likely to mitigate the effects of destabilizing liquid moments. Nomenclature AR = liquid cavity equivalent cylinder aspect ratio CLSM = liquid side moment coefficient CLIM = liquid overturning moment coefficient CLRM = liquid roll moment coefficien