High-Frequency Muzzle Voltage Measurements

Abstract

Abstract : The muzzle voltage in solid-armature railguns is an important diagnostic because it can provide information about the state of the rail-armature interface. Sudden jumps in the muzzle voltage can indicate that an armature has made a transition from low voltage to arcing contact. However, in many tests, the muzzle voltage increases gradually, and the onset of transition as indicated by the muzzle voltage is ambiguous. This report describes research aimed at developing alternative approaches for detecting the onset of arcing contact in solid armature railguns. The work, conducted at the IAT in the early part of 2006, sought to determine whether there is information in the 20 kHz-500 MHz range of the power spectrum that correlates strongly with the onset of transition to arcing contact. To this end, we analyzed two types of signals collected during railgun tests for information that might indicate the onset of arcing. One was a high-frequency muzzle voltage measurement recorded with a 1 GHz sampling rate. The other signal was broad band electromagnetic (EM) radiation (also sampled at 1 GHz) collected using a 2-meter dipole antenna in the vicinity of the railgun. The results show that there is some correlation between the high-frequency and conventional muzzle voltage measurements, and there is little correlation between the broadband EM radiation measurement and the conventional muzzle voltage measurement. The high-frequency muzzle voltage measurement does not appear to contain information about the electrical state of the rail-armature interface that could be used to indicate the presence of arcing.