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The U.S. Navy is considering the development of electromagnetic railguns for future ships for naval surface-fire support (NSFS) and other missions. To reach long ranges, muzzle velocities in excess of 2000 m/s with projectile flight mass of 16 kg and above are needed. Relatively high firing rates are desired; typically 6-12 rounds per minute, so substantial power demands will be made on the ship. For an electrically driven ship, as in the DD(X) concepts presently being explored by the Navy, an existing electrical infrastructure would be in place that could be modified to recharge the pulsed power supplies for the railgun. This study focused on the railgun, the pulsed power system needed to drive the gun, the power system needed to restore the energy required to match the firing rate, and special ship interfaces. Railgun concepts and sizing for the NSFS mission were undertaken, and research and development issues of importance for the success of a future system were identified. Recommendations for analytical and experimental studies that should be undertaken to further address these issues are provided.Index Terms-Electromagnetic railgun, fire support, kinetic energy, projectile, pulsed power.

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Axial beam centroid and beam breakup (BBU) measurements were conducted on an 80 ns FWHM, intense relativistic electron bunch with an injected energy of 3.8 MV and current of 2.9 kA. The intense relativistic electron bunch is accelerated and transported through a nested solenoid and ferrite induction core lattice consisting of 64 elements, exiting the accelerator with a nominal energy of 19.8 MeV. The principal objective of these experiments is to quantify the coupling of the beam centroid motion to the BBU instability and validate the theory of this coupling for the first time. Time resolved centroid measurements indicate a reduction in the BBU amplitude, hξi, of 19% and a reduction in the BBU growth rate (Γ) of 4% by reducing beam centroid misalignments ∼50% throughout the accelerator. An investigation into the contribution of the misaligned elements is made. An alignment algorithm is presented in addition to a qualitative comparison of experimental and calculated results which include axial beam centroid oscillations, BBU amplitude, and growth with different dipole steering.