Influence on launching velocity by the figure and material characteristic of projectiles

A solid metal plate is often used as the projectile in reconnection electromagnetic launcher. Yet the performance is not optimum. In this paper, analysis is made about the laws of influence on magnetic field distribution of driving coils by using projectiles with different figures and materials. Further analysis is made about the influence on launching velocity of the above factors. A single-stage reconnection electromagnetic launcher is made. Experiments are carried out separately on latticed projectiles, hollow projectiles, aluminium projectiles, iron projectiles and copper projectiles. Some significant conclusions are drawn. Under the same condition, hollow projectiles achieve the highest velocity, while latticed projectiles have a weaker shielding effect upon magnetic field. The magnetic permeability and electric conductivity of material have a great influence upon launching velocity. Based on magnetic domain theory, qualitative analysis is made about the causation of magnetic hysteresis loss, classical eddy current loss and abnormal loss. As the loss under high-frequency alternating magnetic field increasing rapidly, ferromagnetic materials are not suitable here. The electric conductivity of projectiles, as well as the thickness and the density makes sense to launching velocity. As the frequency grows higher in pulsed magnetic field, the influence from thickness and electric conductivity of projectiles becomes weaker. Therefore, hollow projectiles made up of aluminium material which has a higher electric conductivity and a lower density will be the best choice.