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The rapid fire railgun (RAFIRA), a unique railgun that can be operated in multishot mode, is well suited for the study of the influence of different rail materials on velocity and electrical contact of the armature and/or the wear of different rail materials. That is why we performed experiments with RAFIRA operated in multishot mode (firing rate of 50 Hz), using different rail materials (CuCr and Dural) and various shot energies. For these experiments, the shot energy for RAFIRA was raised, for the first time, up to the maximum energy at a disposal of 1.45 MJ per shot with projectile masses of over 120 g. In this way, we were able to show that the influence of the rail material depends on the applied shot energy: for low shot energies (<1 MJ), CuCr rails show better results in terms of velocities and exit times of the projectiles. This effect vanishes for high shot energies (>1 MJ). Whereas in terms of electrical contact, Dural rails show both less erosion and the capability to maintain a solid sliding contact until shot out for all energies applied.

The most important part of a railgun launch package is the armature where the electromagnetic force is generated leading to the acceleration of the launch package. In case of metal armatures, the most commonly used armature types are the C-shape and the multi-fiber brush technology. However, rarely both armature types were systematically compared under similar experimental conditions. That is why we constructed launch packages based on the C-shaped and brush armature technology with comparable armature and payload mass. With these launch packages a series of experiments were performed in an energy range between 0.8 MJ and 1.13 MJ corresponding to a speed range between 950 m/s and 1400 m/s. The results of the experiments were then analyzed qualitatively and quantitatively. On the one hand our results show that the total losses are higher for the C-shaped armature technology than for the brush aramture technology. On the other hand our results show that launch packages based on the C-shaped technology convert better electrical energy into kinetic energy.

In the past 30 years, there have been significant advances in the development of modeling and simulation algorithms for electromagnetic railguns. The development of instrumentation capable of measuring the physical parameters that occur during a high velocity launch, however, has not kept pace with the advances in modeling capabilities. In addition, there has been an increase in the size and complexity of existing railguns and therefore it has become necessary to find instrumentation that has the flexibility to conform to the variations present from one railgun to the next, to aid in the cross-utilization of instrumentation across the community. This paper will describe results from Georgia Tech and Navy efforts to evaluate diagnostic techniques that measure different phenomenon at higher resolution in both time and space in order to provide the data needed to validate railgun models. The diagnostics described here address all aspects of railgun testing, including the launcher, projectile, and pulsed power supplies and all phases of the evaluation process from validation of modeling and simulation tools to structural health monitoring. Specific quantities for which diagnostics will be described include temperature, electric and magnetic field sensors, and strain measurements. Examples of electromagnetic sensors that will be presented include colossal magneto-resistance (CMR) sensors, which respond to changes in a magnetic field with a change in resistance, and a slab coupled optical sensor (SCOS) for detecting electric fields. Test results from railguns at both Georgia Tech and ISL will be described.

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