Study of the Current Distribution, Magnetic Field, and Inductance Gradient of Rectangular and Circular Railguns

Two different geometries of the rail in an electromagnetic launcher are rectangular and circular. In this paper, rectangular and circular railguns are simulated and compared using the finite-element method. Rectangular and circular railguns are formed by two parallel copper rails. The surface area of the railgun bore is 9 cm² and the surface area of the rail cross-section is 6 and 18 cm². Current distribution (<i>J</i>), magnetic field intensity (<i>H</i>), and inductance gradient (<i>L</i>^') are computed for the two aforementioned bore geometries, and the results are compared together. In the circular railgun, <i>L</i>^' is a function of the opening angle of the rails (θ), inner radius (<i>R</i>_i), and outer radius (<i>R</i>_o). Different values for θ, <i>R</i>_i, and <i>R</i>_o, in practical range, are used to compute <i>L</i>^'. By analyzing the numerical and theoretical results, it can be shown that the magnetic flux density in the middle of the circular railgun is a descending function according to the central angle. Finally, strengths and weaknesses of the rectangular railgun in comparison with the circular railgun are discussed.