Kevin J. White

Plasma-propellant interactions studies: measurements of heat flux produced by hydrocarbon ablation-supported plasmas

An investigation is underway to determine the mechanisms which contribute to the enhanced performance of electro-thermal chemical (ETC) ignition systems. Measurements of the plasma properties are difficult due to the hot, low density, ionized plasma flow which interfered with the data acquisition system. The present study utilizes an infrared (IR) camera to measure the temperature of both a copper disk and propellant grains exposed to a plasma. Use of the IR camera minimizes the electrical noise interference experienced in past experiments. The copper disk was used to determine the total energy flux produced by the plasma and the propellant grains were used to determine the energy flux absorbed by the propellant. A larger average energy appears to be transferred to JA2 compared to M30 propellant with similar plasma energy inputs. While it is likely that this is due to the higher absorption coefficient of JA2, the JA2 experiments also showed a significant amount of particles on the propellant face which may have contributed to the higher energy measured.

Experimental characterization of plasma effects on energetic materials for electrothermal-chemical launch applications

Energetic electrical plasmas play a fundamental role in the electrothermal-chemical (ETC) propulsion concept, where they are used to provide energy conversion from an electrical power source to the combustion chamber of an ETC launcher. Recent research in the areas of large-caliber ETC gun experiments as well as small-scale plasma experiments have demonstrated the ability to alter the propellant combustion process and the chemical or physical properties of propellant samples exposed to energetic electrical plasmas. Such results have warranted continued investigations into the underlying processes involved in propellant and plasma interactions, specifically in the behavior of exposed propellant samples to plasmas operating at varying degrees of electrical power. Experimental characterization has been performed with various samples of energetic materials including JA2, CL20, RDX, M9, M30, M43, KELP, and BAMO-AMMO (BA), which were allowed to interact with plasmas having different electrical power levels. The plasma power level ranged from 60 MW to a maximum of 264 MW, and total energy transferred to the plasma capillary ranged from 17 to 70 kJ. Propellant samples were analyzed using a Fourier transform infrared spectroscopy (FTIR) technique, which was used to determine the effects of plasma exposure on the energetic materials. Preliminary results from the experiments indicate that some propellant formulations are easily altered (either chemically or physically) or ignited by a plasma while others are less sensitive to the plasma exposure. In addition, the effects of the plasma are found to be minimized with the introduction of protective films even for plasmas of high power and energy levels.

Measurement techniques in a 30-mm electrothermal-chemical (ETC) gun facility

Abstract : Methods of acquiring data including pressures, load current and voltage, and crow-bar diode current and voltage with a minimum of electrical noise in electrothermal-chemical (ETC) ballistic and combustion experiments are described. Measurements are performed in a 30-mm ETC gun facility that is driven by a 130-kJ (maximum) pulsed-power supply and a 50-cm3 closed chamber facility using a 300-kJ power supply, both of which are located at the U.S. Army Research Laboratory (ARL), Aberdeen Proving Ground, MD. Strict attention is devoted to grounding measurement and data-recording devices, as well as to shielding measurement electronics, data lines, and high-power modulator components with faraday enclosures. The use of ferrite rings on data lines and 60-Hz power lines is frequent, and fiber-optical links are used for electrical isolation between data recording equipment and high-voltage components. The experimental arrangement and resulting data are presented, and comments and conclusions are included.