h. ebrahim

In this research, the heterogeneous decomposition reaction of hydrazine and ammonia in a space propulsion system of hydrazine monopropellant type with an adiabatic fixed bed reactor and 30% iridium catalyst is used to create a thrust force of 5 newtons and a specific impulse of 220 seconds and the application of position change or orbital motion. This process is created by two heterogeneous reactions and turning into hot light gases of hydrogen and nitrogen leaving the reactor bed and then the nozzle of the thrust force in the opposite direction of the gas flow. Considering that the iridium 30%  is a reference and main catalyst that has suitable mechanical, physical, and thermal properties but is very rare and expensive, the purpose of using nickel replacement catalyst 15% is . Compared to iridium, this catalyst is very abundant and cheap, and has functional characteristics, suitable and close to iridium. Regarding the correctness and accuracy of the performance results of two catalysts in a space propulsion system and vacuum conditions and the same static and operational test in a stable and uniform flow of hydrazine to the reactor bed for 30 seconds were measured and evaluated by evaluation indicators such as creating force Thrust (5 newtons), special impulse (about 230 seconds), bed pressure drop (less than 1 bar), minimum amount of ammonia decomposition are compared. Finally, due to the compatibility of nickel catalysts with iridium, a suitable alternative is approved.

In the present study, a space thruster system type monopropellant has been modeled and designed so as to create a Five- Newton thrust force(propulsion) and specific impulse of 220 seconds, with the usage of adjusting motion or changing the position of the satellite. This model consists of two major parts including a catalytic reactor with hydrazine feed, 15% nickel catalyst based on gamma alumina and a convergent-divergent nozzle. The catalytic reactor model is a fixed bed, one-dimensional, steady state and adiabatic with heterogeneous decomposition reactions. The process functions by performing two heterogeneous decomposition reactions of hydrazine and ammonia and converting to light gases (hydrogen and nitrogen) with high temperatures. Subsequently, the thrust force will be obtained by the evolution of the gas from bed and nozzle. The catalyst is made up of wet impregnation method and the required characteristics are specified by quantitative, qualitative and thermal analysis tests. The outcomes of modelling include mass, energy, kinetic, physical and chemical variables in the space propulsion. It is also considered as one of the important advantages of designing the measurement and predicting the variables. So as to determine the performance and validity of the model, indicators such as the thrust force, specific impulse, bed pressure drop and the minimum of ammonia decomposition has been scrutinized with the same kinetic and operating conditions in the designing and experimental model (in atmospheric conditions and static). The obtained results are consistent and have been verified.

We use gauge-gravity duality to study the effect of corrections to the coupling constant on equilibration time in field theory for scalar operators with Delta=2,3. We will show that for larger correction in coupling constant the equilibration time enhances and this behavior is independent of the method we use to make the system out of equilibrium. Interestingly we observe that for fast energy injection the rescaled equilibration time is independent of temperature of field theory.