Influence of internal moving parts on the ballistic flight path of a projectile
The ballistic flight path of an artillery shell containing an internal component, which is only partially restrained with respect to the geometric axes, can differ significantly, and in some cases disastrously, from the expected flight path of an inertially equivalent rigid shell. Dynamic behavior of the internal component creates gyrodynamic torques ultimately affecting the shell's instantaneous heading angle and spin rate. The ability of a shell to damp these torques and retain both aerodynamic and gyroscopic stability depends in large measure on initial rotational and translational kinetic energy, expected apogee, and inertial properties. To investigate the consequences of nonrigid shell trajectories, a model is proposed comprised of a shell case with an internal body capable of independent rotation and translation. Examination of the resulting equation of motion shows that the shell's heading angle resembles the description of a linear damped harmonic oscillator driven by a forcing function created solely from the internal component. Any resulting phase behavior between the principal axes of inertia of the body and component can drive the internal component at a forced and free natural nutation frequency. In a departure from earlier research done in this field, it is contended that not all internal motion leads to the destabilization of flight behavior. Instead, stability depends on: (1) the ratio of moments of inertia of the internal part; (2) the applied aerodynamic moments (whether supersonic, transonic, or subsonic); and (3) the combined component/body transfer function.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5688497
- Report Number(s):
- UCRL-92781; CONF-850881-2; ON: DE85013203
- Resource Relation:
- Conference: 12. conference on atmospheric flight mechanics, Snowmass, CO, USA, 19 Aug 1985
- Country of Publication:
- United States
- Language:
- English
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