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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, HELP, 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. Index Terms - electrothermal/electrothermal-chemical launchers.

Materials research involving novel semiconductors for application to high-temperature electronics has taken on much interest recently by the scientific community. While silicon (si) based electronic materials and devices continue to play a dominant role in much of the electrical power industry, novel high-power and high-temperature materials are of great interest to the electric combat systems community. The technical interest in silicon carbide (SIC) is mainly due to its ability to operate at greatly elevated power and temperature (>300 [degrees] C) levels compared to its Si-based counterpart. High-power and temperature pulsed-power electronics can be exploited by future military combat systems, which could potentially provide significantly improved combat vehicle performance including increased lethality through extending the maximum obtainable gun performance using advanced electric weapon concepts such as electrothermal-chemical (ETC) and electromagnetic (EM) gun technologies. The results of recent experiments conducted at the U.S. Army Research Laboratory (ARL) and the University of Delaware demonstrate the electrical behavior of SiC and metal ohmic-contact layers as a function of thermal stress. It has been determined from these experiments that both titanium (Ti) and tantalum (Ta) metalization structures will provide a stable electrical ohmic-contact with n-type SiC at elevated temperatures for short bursts of time that are considered relevant for pulsed-powered electric weapon technologies. The Ti-SiC structure investigated exhibited a stable current-voltage (I-V) characteristic to as much as 800 [degrees] C for a 10-rain burst, while Ta metalizations provided a stable I-V characteristic on SiC even after a temperature burst of 1,000 [degrees] C for as long as a 3-min interval. For samples of n-type, 4H SiC, metalized with (Ti), the standard deviation in resistance (resistivity) of the measured samples is less than 0.17 ohms for a sample having an average resistance of 4.45 ohms. The Ti-SiC sample was exposed to an elevated temperature range of 300-1,120 [degrees] C. For the Ta contact on SiC, the standard deviation in resistance is 0.05 ohms for a sample having an average resistance of 4.25 ohms over a temperature range of 600-1,120 [degrees] C. The experiments showed that for both Ti and Ta metalized SiC samples, the change in resistivity of annealed samples is between 3.8% and 1.2% compared to the average values of sample resistance based upon the I-V measurement technique used. These results indicate the ability of Ti-SiC and Ta-SiC structures to perform in a stable manner without significant electrical degradation to the metal contact, SiC substrate, or the metal-semiconductor interface as a function of high-temperature burst conditions. Index Terms - power conditioning and energy storage.

Theoretical calculations are performed with a one-dimensional (1-D), steady state, isothermal computer plasma model to define plasma output parameters for various input electrical energies and capillary radii of relevance to the electrothermal-chemical (ETC) propulsion concept. Three capillaries of 1.92, 4.75, and 7.0 mm radius, and a fixed length of 11.84 cm, were chosen for this study with input currents between 30 and 350 kA. Plasmas are categorized according to their total power and energy levels (based on a 3-ms pulse width) and are compared with respect to their resistance, exit pressure, and core plasma temperature. The input power ranges from 0.17 to 1.89 GW, for input energies from 0.49 to 5.80 MJ, which is considered suitable coverage for ETC ignition through ETC enhanced propulsion concepts. The study shows that the range of resistance, pressure, and temperature are 12.8-195 [milli[ohms]], 19.8-2000 MPa, and 2.9-13.5 eV, respectively, for the chosen capillary geometry. Flow conditions for plasma calculations include choked (no pressure boundary) and unchoked (450-MPa pressure boundary) for some calculations. Results from the computational model and interpretations from the perspective of capillary implementation into ETC propulsion concepts are also included. Index Terms - Capillary, ionized gas, plasma, polyethylene, propulsion, pulsed power.

Researchers at the Weapons and Materials Research Directorate of the Army Research Laboratory (ARL) have recently completed experimental testing with a G-hardened gun-launched miniature instrumentation package that fits within the projectile fuze cavity for obtaining realistic in-bore, deceleration, and projectile impact data. This device consists of an accelerometer and a digital recorder that is designed for the reliable capture of ballistic data during projectile launch, flight, and target impact. During recent flight test evaluation at the ARL, Aberdeen Proving Ground, projectiles containing this device were tested with a telemetry link as well as recovery and direct downloading of onboard recorded data. For projectile impact studies both concrete and bunker targets were successfully engaged. This methodology of onboard data recording has been shown to provide a reliable and high-fidelity characterization of projectile in-bore and impact events critical for advanced munitions designers. Index Terms--Ballistics, flight-testing, high-g recorders, instrumented projectiles.

Recent experiments with die-level silicon carbide (SIC) transistors are described where the objective of the experiments is to determine the behavior of SiC field effect transistors (FET) in a high-g environment typical of conventional guns, missiles, or electric launchers. The results of the experiments have shown for the first time that die-level SiC FET's can survive mechanical forces to as much as 12 000 times the force of gravity (12000-g's) without the mechanical support and protection of microelectronic encapsulation materials (e.g. plastic encapsulation material or PEM). A second series of experiments is performed with commercial-off-the-shelf (COTS) sensors that rely upon standard sensor technology including silicon (Si) semiconductors. These experiments provide details of several COTS sensors previously qualified for high-g environments, which are characterized here under harsh electromagnetic interference (EMI) conditions. The sensors tested include a Si optical solar cell, an accelerometer, and a magnetometer. The output response of the sensors is recorded during the EMI event to ascertain the effect of coupled electromagnetic radiation on the sensors. Index Terms--Electric weapons, electromagnetics, EM, high-g, munitions, SiC, silicon carbide, widebandgap materials.

Presents the Pulsed Power-Plasma-Interior Ballistic (PPIB), a PC-based, end-to-end electrothermal-chemical (ETC) gun ballistic simulation code developed by Princeton Combustion Research Laboratories. Analysis on the development of the PPIB code; Calculations of High energy plasma; Conclusions.