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In this paper, we evaluate the thermal stress arising in rails and supporting structures of an electromagnetic launcher. We examine the effects of using rail overlays and active cooling. These not only reduce the peak temperature, but also affect the overall thermal gradient. The transverse temperature distribution within the rail structure is obtained by a numerical solution of magnetic and thermal diffusion equations. The effects of cooling rate and cooling channel location on the temperature distribution are evaluated. The resultant thermal stress in the rail structure is then computed. The analysis yields two fruitful approaches: use of thin resistive overlays, which minimize thermal stress on the structure by effecting a more even temperature distribution; and use of active cooling at a central location, which even though ineffective at very early times, enables more efficient heat removal in the time between launches.
Date of Publication: Jan 2003