Effect of the thermal and gas-dynamic properties of solid rocket propellant particles on the propellant combustion rate

The aim of this work is to eliminate the explosion possibility of a rocket engine that operates on a fast-burning solid propellant. The problem is considered by analogy with experiments conducted earlier. Various ways to increase the propellant combustion rate are presented. Examples of how the solid propellant combustion rate depends on the metal fuel and the oxidizer particle size are given. It is shown that unstable combustion of a solid propellant at high combustion chamber pressures is due to unstable combustion of the gas phase in the vicinity of the bifurcation point. Zeldovich’s theory of nonstationary powder combustion is applied to analyzing the explosion dynamics of the Hrim-2 missile’s solid-propellant sustainer engine. This method of analysis has not been used before. The suggested version that this phenomenon is related to the aluminum particle size allows one to increase the combustion rate in the combustion chamber of a liquid-propellant engine, thus avoiding the vicinity of the bifurcation point. The combustion of solid propellants differing in aluminum particle size is considered. The metal fuel and the oxidizer particle sizes most optimal in terms of explosion elimination are determined and substantiated. The use of submicron aluminum enhances the evaporation of ammonium perchlorate due to the infrared radiation of aluminum particles heated to an appropriate radiation temperature. This increases the gas inflow into the charge channel, thus impeding the suppression of ammonium perchlorate sublimation by a high pressure, which is important in the case where the engine body materials cannot withstand a high pressure in the charge channel. This increases the stability and rate of solid propellant combustion. It is shown that the Hrim-2 missile’s solid propellant cannot be used in the Hran missile. The combustion rate is suggested to be increased by using fine-dispersed aluminum in the solid propellant.

Capacitance-voltage differintegral characteristics of fractal field-effect device

In the present paper, we use the theoretical model of fractal elements to study the charge and capacitance-voltage differintegral characteristics of a fractal field-effect device. The control of the charge channel and the capacity of a fractal nanotransistor is revealed by changing the scaling of the nanolayer, the charge density in which is determined from the sum of the charges of electrons, holes, and ionized impurities. The significant influence of fractal charge distribution carriers on the device capacitance at high frequencies is noted. This fact theoretically confirms the possibility of increasing the capacitance of metal-oxide-semiconductor structures to increase the efficiency of the field-effect-transistors. The comparison of the obtained expressions shows the strong influence of fractal medium on the electric field size and charge density in a semiconductor that is followed by the change of capacitive device parameters. The differential-integral method for modeling artificial metamaterial fractal radioelements with necessary electrical characteristics is proposed.

On the influence of the charge channel geometry and fuel properties on the working process instability in the solid propellant rocket combustion chamber

The paper numerically studies the influence of how the charge channel shape and the law of solid fuel burning rate influence the gas-dynamic vortex flow pattern and pressure self-oscillations in the combustion chamber of a solid-propellant rocket engine. The work presents the findings of the research which show that, using the numerical method, it is possible to choose the optimal shape of the charge channel and the solid propellant grade, which provide the least probability of occurrence of the pulsating combustion regime

Organic Materials for Multifunctional Transistor-Based Devices

Organic field-effect transistors (OFETs) are “soft material” versions of accumulationmode silicon-based FETs, where a gate field across a dielectric induces a conductive charge channel at the interface of the dielectric with a semiconductor, between source and drain electrodes. Charge carrier mobilities >0.01 and on/off ratios >10,000 are routinely obtained, adequate for a few specialized applications such as electrophoretic pixel switches but well below standards established for silicon microprocessor technology. Still, progress that has been made in solution-phase semiconductor deposition and the printing of contacts and dielectrics stimulates the development of OFET circuits for situations where extreme low cost, large area, and mechanical flexibility are important. Circuits with hundreds of OFETs have been demonstrated and a prototype OFETcontrolled black-on-white “electronic ink” sign has been fabricated.