Dynamic modeling of the atmospheric flight mechanics of a projectile equipped with an uncontrolled internal rotating disk is investigated and a modified projectile linear theory is established. It is shown through modeling of this type of projectile that several coefficients of the epicyclic dynamics are altered, leading to changes in the fast and slow epicyclic modes. A study of the frequency and damping properties of the epicyclic modes is conducted by systematically varying disk orientation, location, mass, and rotational speed. It is shown that the presence of an internal rotating disk can cause substantial changes in the epicyclic dynamics, suggesting the potential of a rotating internal part as a possible control mechanism. A further study considers the active trajectory control of a projectile using a mass unbalance, created by the radial orientation of an internal part. To evaluate the potential of this concept, a seven degree-of-freedom flight dynamic model of a projectile equipped with an internal part is defined. It is shown that by holding the internal part fixed with respect to a non-rolling reference frame, predictable trajectory changes are generated including predictable impact point changes. It is also shown that using the same control mechanism and destabilizing the projectile by fundamentally altering the inertia and, or aerodynamic properties of the projectile can lead to greater control authority. / Graduation date: 2005

The effectiveness of a direct fire penetrator projectile equipped with an actively controlled ram air mechanism is investigated through dynamic simulation. The ram air control mechanism consists of a rotary sleeve valve which directs air flow from an inlet at the center of the nose to side ports. The projectile dynamics, the inertial measurement unit and the control system are included in the system model. It is shown that the ram air control mechanism provides sufficient control authority to significantly reduce dispersion of a direct fire penetrator. The effects of accelerometer and gyroscope bias and noise are investigated. It is seen that moderate values of bias and noise do not affect the dispersion significantly. But with higher values the dispersion is greater than the dispersion for the free flight. / Graduation date: 2002

Currently, there are few analytical tools within the ballistics community to aid in the design and performance evaluation of aerodynamically asymmetric projectiles. The scope of this thesis is to (1) create analytical tools that are capable of quantifying aerodynamically asymmetric projectile performance, (2) demonstrate the ability of these models to accurately account for aerodynamic asymmetries, and (3) gain insight into the flight mechanics of several aerodynamically asymmetric projectiles. First, a six-degree-of-freedom (6 DOF) flight dynamic model, which uses a point-force lifting-surface aerodynamic model, was developed to replicate flight characteristics observed from measured results of common projectiles. A quasi-linear flight dynamic model was then created using the machinery of Projectile Linear Theory (PLT). From this, flight dynamic stability models were developed for linear time-invariant (LTI) and linear time-periodic (LTP) systems. Dynamic simulation and stability trade studies were then conducted on asymmetric variants of 4-finned, 3-finned, 2-finned, and hybrid projectile configurations. First, stability of symmetric projectiles are validated and show that the classical and extended PLT model yielded identical results. Results show that aerodynamic asymmetries can sometimes cause instabilities and other times cause significant increase in dynamic mode damping and increase/decrease in mode frequency. Partially asymmetric (single plane) configurations were shown to cause epicyclic instabilities as the asymmetries became severe, while fully asymmetric (two plane) can grow unstable in either the epicyclic modes or the roll/yaw mode. Another significant result showed that the LTP stability model is able to capture aerodynamic lifting-surface periodic affects to evaluate dynamic stability requirements for asymmetric projectiles.