Available at: http://digitalcommons.calpoly.edu/theses/1563
Date of Award
MS in Electrical Engineering
This thesis derives working expressions from electromagnetic physical laws to gain a deeper understanding of the nature of railguns. The expressions are refined for ease of use and then compared to electromagnetic simulators that solve complex equations that arise from different rail geometry. Further simplifications lead to an expression for the final velocity of the projectile and showcase the importance of the system resistance to projectile flux gain ratio. A Simulink simulation then incorporates the resulting non-linear differential equations and approximates the projectile velocity over time based on physical dimensions and material properties. Some equations derived can be found in literature regarding the subject but often lack explanation. This work is intended to provide a thorough derivation of all the relative constituent relations between the critical characteristics of the gun such as the strength of the forces acting on the rail and projectile, rail current, and initial velocity of the projectile. This makes it easier to identify what influences acceleration of the projectile, how much bracing each rail needs, how much initial velocity to give the projectile, etc. Design options discussed besides the standard design include the augmented rail system, a magnetic shell design, and a “wrap around” design. The tradeoffs encountered in each design are discussed in length. Due to the lack of a sufficient power source during testing the projectile was unable to travel down the length of the rails due to metal binding, insufficient pulse duration, and too much circuit resistance. It was found that using copper tungsten for the rails ensures that the rails can withstand the arcing inflicted by the kilo-Ampere current along the rails very well compared to other materials. Also, the copper in the tungsten alloy ensures high conductivity while the tungsten provides structural integrity to the rails during arcing between them and the projectile. Frequency response of conductive projectiles is characterized and improvements such as laminated projectiles are suggested as solutions to mitigate eddy currents induced in the projectile and improve performance.
Available for download on Thursday, June 08, 2017