Measuring the Armature Position in a Railgun Using Embedded Permanent Magnets

This paper describes how small permanent magnets embedded in a launch package can be used to locate armature position during launch with greater accuracy than can be achieved by detecting the dipole field of the armature itself. Using this technique, we determined armature position in a medium-caliber launcher to within a millimeter of the value measured with photonic Doppler velocimetry, a precise optical technique. This paper describes the technique and some experimental results.