We have developed an extensive range of low hazard, ESPs with unique features, not previously known for energetic materials. When an ESP is fitted with electrodes and the required voltage and current are applied, the solid propellant ignites and continues to burn until the voltage is removed, causing extinguishment. Once extinguished, the electrically controlled propellant can then be re-ignited electrically at will. Throttling of the propellant burning rate is accomplished by changing the electrical power input (Sawka, 2007). Baseline ESPs are also insensitive to ignition by spark, bullet impact and flame, so they are safer to transport and should be able to be used as DOT Class 1.4s explosives.
DSSP is developing a new class of deployable energetics that are safe, electrically-controlled Electric Solid Propellants (ESP). These novel energetic materials are suited to a broad spectrum of applications, including commercial space propulsion, explosives, and pyrotechnics. Vol. 5 No. 1 26 Identify. Adapt. Deliver.™ IQT QUARTERLY.
While the acronym ESP readily describes the desired properties, there is a significant amount of fundamental chemistry understanding and materials science engineering required to bring these materials to a readiness level suitable for use and deployment. Even more is required to do so in a commercially sustainable fashion.
Understanding the chemistry starts with a molecular description of the structure of the propellant. DSSP’s ESP energetics are cross-linked solution-solids similar to today’s plastisol energetics. This is unlike most conventional energetics, which require a separate chemical binder to hold the materials together.
Once cured, unlike every other known energetic material, ESPs are inert unless ignited with an electric potential of appropriate magnitude. Once electrically ignited, burning rates can be increased by at least 10x (throttled) using higher amounts of electrical power and then switched off (extinguished) by removing that electrical power. DSSP has shown that ESPs cannot be ignited by flame, spark, shock, or even bullet impact. The combustion of baseline ESP formulations produces benign non-toxic gases with CO2, N2, and H2O as the major products, so they are safe for use in close proximity to humans. ESPs represent the first “smart” energetic material. Unique to the ESP formulation is the liquid HAN oxidizer which is an ionic liquid with semi-crystalline behavior. Ionic liquids allow transport of electrical charge through the materials and provide ESPs’ remarkable response to electrical power. Whereas most conventional propellants have very low electrical conductivity, ESPs are highly conductive.