Masters Theses

Date of Award

5-1993

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

Roger Crawford

Committee Members

Vakili, Peters

Abstract

Railgun performance has not reached the expected level as originally indicated by electromagnetic theory. That is, projectile exit velocities do not approach the extremely high velocities that ideal analysis indicated Various researchers re-examined railgun theory, and attempted to determine ways of improving railgun performance.

Research at the University of Tennessee Space Institute has been conducted to explore the causes of that decrease in performance. Ablation in the railgun bore has been identified as a factor in the reduction of peak expected performance. However, some experimental data indicated that some ablation effects, primarily the electrothermal interaction of the expanding ablated material and the driving gas, actually increased performance under certain conditions.

The purpose of this thesis is to describe the effort undertaken to identify some of the effects that ablation imposes on the performance of railguns, and to describe the computer model created to simulate these effects. This computer model included routines which accounted for the gas dynamics of the injector's driving gas through use of the (1)time-dependent method of characteristics, (2) the electromagnetic forces occurring within the electric arc armature, (3) the rate of ablation of material from the wall, and (4) the electrothermal interaction between each of these. A description is made of each routine's impact on the simulation, and each routine's importance to the calculation procedure is identified.

This effort concluded that the electrothermal interaction which occurred in each shot caused the driving potential of the injector light gas to increase, thereby increasing the force attributable to the light gas. This increase in force caused the railgun to produce velocities higher than were expected.

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