Simplified Interior Ballistics Analysis of a Hybrid Projectile Prototype

Structural analysis is a critical aspect in the successful design of tube launched projectiles, such as mortar rounds. Ongoing research conducted at West Virginia University has focused on a Hybrid Projectile (HP), folding-wing UAV design inspired by mortars. This has driven the necessity of a structural analysis of the prototype design to provide vital feedback to designers to ensure that the HP is likely to survive the act of launching. Due to the extreme accelerations during the launching phase, a typical mortar round experiences dramatic impulse loads for an extremely brief duration of time. Such loads are the result of the propellant combustion process. Thermodynamic-based interior ballistic computations have been formulated and were used to solve the dynamic equations of motion that govern the system. Modern ballistic programs solve these equations by modeling the combustion of the propellant. However, mathematical procedures for such analyses require complex models to attain accurate results. Consequently, the objective of this research was to create a ballistic program that could evaluate interior ballistics by using archived pressure-time data without having to simulate the propellant combustion. A program routine created for this purpose reduces the complexity of calculations to be performed and minimizes computational effort, while maintaining a reasonable degree of accuracy for the motion dynamics results (temporal position, velocity, acceleration of the projectile). Additionally, the program routine was used to produce a mathematical model describing the pressure as a function of time, which could be used as loading conditions for more advanced explicit-dynamic finite element simulations to evaluate the transient response and stress wave propagation of the prototype and individual payload components. Such simulations remove uncertainties related to the transient loads needed to assess the structural integrity of the projectile and its components.