Diagnostic capabilities for electromagnetic railguns

Abstract

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.

<italic>In Situ</italic> Measurement of Strain and Temperature for Railgun Launcher Diagnostics

“…Phosphors have long been known to exhibit temperature dependence in their luminescence characteristics that can be exploited for temperature measurements [2]- [5]. Both the decay time of the luminescence and its spectral properties change in a quantifiable way as a function of the substrate temperature.…”

“…This paper describes the status of continuing efforts by ONR and Georgia Tech (GT) to develop and apply diagnostic technologies for the measurement of in-bore temperatures and mechanical strain using optical techniques [2]. The technique to be described for temperature measurements is based upon phosphor thermometry, whereas two different mechanical strain measurement techniques will be compared, one based on Brillouin scattering and the other using fiber Bragg gratings (FBGs).…”