Optimization of Spark and ESD Propellant Sensitivity Tests. A review

Abstract

AbstractAll cured propellants can pass small‐scale spark sensitivity tests, yet some, generally involving larger propellant samples, are electrostatic discharge (ESD) sensitive. These tests fail to rank propellants because the test methods themselves are not optimized and frequently use instrumentation which does not indicate the energy transferred to the sample.For spark ignition of premixed combustible gases or fuel sprays in air, minimum energies are measured and considered thermochemical properties for a given fuel/air ratio, initial temperature and pressure, and for a spray, a given droplet size distribution. Obtaining such data requires monitoring the total energy discharged across the gap during the spark and parametric studies where gap length and spark duration are varied systematically to establish the true minimum (essential to hazard/risk analysis). Electrode geometry and tip design, as well as electrode material, are other important considerations.Present spark and ESD sensitivity tests used for solid propellants are reviewed in the context of methods more likely to provide meaningful initiation thresholds.