Development of the prototype Munitions Case Moisture Meter, Model ORNL-1

Abstract

There is a great need for a rapid and simple means of determining the moisture content in combustible cartridge case (ccc) munitions. Previous studies have demonstrated that accumulation of moisture in ccc rounds, such as the M829, leads to softening of the case wall and weakening of the adhesive joint. Moisture in the ccc can lead to incomplete combustion of the case upon firing the round. Currently, there are no facile methods for measuring the moisture content. A prototype portable meter for non-destructive and rapid estimation of moisture in ccc has been developed. The Munitions Case Moisture Meter Model ORNL-1 demonstrates the feasibility of developing an instrument based on the moisture dependence of dielectric properties, to measure moisture in ccc munitions in storage and in the field. These instruments are simple, inexpensive, lightweight, portable, low-power battery operated, and intrinsically safe. They provide nondestructive, noninvasive, and rapid measurements. Calibration data for the prototype are not available at this time. Therefore, calibration of the meter and the development of a scale reading directly moisture content in munitions rounds could not be completed. These data will be supplied by the US Army from its tests of the meter with actual munitions. However, experimental results on empty cccs in laboratory conditions demonstrate satisfactory performance of the instrument. Additional work is needed to bring the prototype to its optimum usefulness and accuracy for field measurements. This includes: Calibration of the meter scale with full-up munitions; Data and evaluation procedures to adjust the performance of the meter for different environmental conditions such as temperature and humidity; and Studies of the dielectric properties of moist ccc materials, as a function of frequency and temperature, are needed for adjustment of the meter for optimal performance.