Sharif Digital Repository

Transient internal ballistics of a solid propellant rocket motor during rapid depressurization due to opening of an auxiliary nozzle for active thrust termination has been considered in this work. Prediction of thrust termination and reversing dynamics is required for successful stage separation in multi-stage rockets. Quasi one-dimensional unsteady Euler equation with a transient propellant burning model that accounts for the effects of time rate of change of the chamber pressure on the burning rate have been used to simulate the internal ballistics of a rocket motor. The compressible convective flow solver used in this study is based on Roe's scheme. The effects of rapid chamber pressure... 

Thrust termination dynamics of a solid propellant rocket motor that is crucial to the performance of the rocket has been analyzed. Active thrust termination or reversing of a separating motor facilitate the staging process and enhance the performance of a multistage rocket. This can be achieved by opening a secondary nozzle located on the motor head and causing rapid depressurization of the motor chamber. The strong dependence of the solid propellant burning rate on the chamber pressure causes a transient nonlinear behavior that can result in premature dynamic extinguishments of the motor. It was confirmed that there is a maximum achievable level of equilibrium reverse thrust due to... 

Solid rocket performance during rapid pressure excursions differs greatly from predictions based on steady state burning rate data. Rapid pressurization following a chamber filling interval produces indicated burning rate overshoots. Transient internal ballistics of a solid propellant rocket motor during rapid pressurization part of chamber filling phase has been considered in this work. Quasi one-dimensional unsteady Euler equations with a transient propellant burning model that accounts for the effects of time rate of change of the chamber pressure on the burning rate have been used to simulate the internal ballistics of rocket motors. The compressible convective flow solver used in this... 

In this paper, the internal ballistics of a solid propellant rocket motor including a pyrogen type igniter is numerically investigated. The aim of the simulation is to calculate the chamber pressure as a function of time, during flame spreading phase. In addition, effects of the igniter flow on the propellant heat-up and ignition are studied in detail using unsteady quasi one-dimensional conservation equations for a working gas, coupled with the transient conduction within a solid propellant. The convective and radiative heat flux from the igniter flow to the solid surface is considered. The flow-field equations are solved using upwind Roe's scheme. The obtained results can be used to design... 

Spining is used in some of solid rocket motors to increase the flight trajectory precision or for stability requirements. The angular acceleration due to the spin increases the burning rate of solid propellant and changes the motor performance by increasing the operating pressure and decreasing the burning time. On the other hand, due to the rocket and its grain rotation, the gases injected from propellant surface to the flow field have an initial angular velocity. The angular velocity of each particle increases as it approaches to the center due to the conservation of angular momentum and a reduction in its radial location, although it vanishes close to the central axis due to viscous... 

In this paper, the internal ballistics of solid propellant rocket motor with an arbitrary grain configuration is numerically investigated using quasi one dimensional simulation of Inviscid conservation equations. The upwind Roe's scheme is used to calculate the convective fluxes. Appropriate burning rate model to predict the erosive burning in solid propellant is used here. By using this phenomenon and accurate simulation, tactical motor performance can be considerably improved  

In this paper, the effect of viscosity on internal ballistics simulation of a solid rocket motor with an internal burning cylindrical grain is numerically investigated. Axisymmetric compressible Navier-Stokes equations are discretized by finite volume approach on structured mesh and are solved using upwind Roe's scheme. A quasi steady procedure is used to simulate the regression of the burning surface by using a steady flow solver. Grid resolution is studied to insure acceptable accuracy. It is finally shown that most physical phenomena are quite accurately simulated by using an Euler solver, while NS solvers do not increase the accuracy as much they increase the CPU time  

In this paper, the effects of water addition to a solid rocket motor (SRM) with an end-burning grain configuration are investigated, numerically. Inviscid quasi one-dimensional conservation equations are discretisked and solved using upwind Roe's scheme together with appropriate boundary conditions. The set of assumptions made to solve the problem are described in detail and the results are presented for several water inlet diameters and pressures. It is shown that, the penetration of a certain volume of water into combustion chamber can result in an ISP increase of up to 14% and therefore a performance enhancement with no extra mass of propellant  

In this paper, the internal ballistics of a solid rocket motor (SRM) including a blast tube is investigated, numerically. Effects of the blast tube presence on the performance of the SRM are studied in detail using unsteady quasi one-dimensional conservation equations. These equations are discretized and solved using upwind Roe's scheme. Any two-dimensional grain configuration can be accounted for if an appropriate geometrical input file is generated using a grain analysis program. The results are presented for several blast tube geometries  

Rarefied gas flow in micro/nano electro mechanical systems (MEMS/NEMS) does not perform exactly as that in macro-scale devices. The main goal in this study is to investigate mixed subsonic-supersonic flows in micro/nano channels and nozzles and to provide physical descriptions on their behaviors. We use DSMC method as a reliable numerical tool to extend our simulation. It is because the DSMC provides accurate solution for the Boltzmann equations over the entire range of rarefied flow regime or Knudsen numbers. As is known, the appearance of oblique/normal shocks at the inlet of a channel or a nozzle adds to the complexity of internal flow field analyses. We found some very unique physical... 

The hybrid rocket motor is a kind of chemical propulsion system that has been recently given serious attention by various industries and research centers. The relative simplicity, safety and low cost of this motor, in comparison with other chemical propulsion motors, are the most important reasons for such interest. Moreover, throttle-ability and thrust variability on demand are additional advantages of this type of motor. In this paper, the result of an internal ballistic simulation of hybrid rocket motor in a zero-dimensional form is presented. Further to validate the code, an experimental setup was designed and manufactured. The simulation results are compared with the experimental data... 

The performance of an HTPB/N2O hybrid motor was experimentally investigated. A hybrid motor was designed and manufactured in a laboratory with the purpose of studying the effects of various parameters on the motor's performance, including fuel regression rate and specific impulse. A series of tests were conducted to find a correlation between the fuel regression rate and the oxidizer's mass flux. The effects of chamber's pressure on the regression rate as well as other performance parameters were investigated. While the burning rate did not change dramatically, both the efficiency and ISP of the motor increased. The local fuel regression rate and the fuel port were also calculated. In... 

Time-varying structural reliability of a multistage solid-propellant launch vehicle subjected to deterministic and stochastic loads is investigated. The study is of practical importance because the launch vehicle's structure is influenced by a combination of external aerodynamics as well as inertial and internal ballistic loads emanating from the solid rocket motors. In addition, as launch-vehicle flight conditions change during flight, the vehicle will be subjected to time-varying loads. In this sense, the environmental, aerodynamic, and internal pressure fluctuations can be interpreted as stochastic forces affecting the launch-vehicle structural reliability. To account for temporal... 

Structural and system reliability of a typical jet vane (JV) thrust vector control (TVC) subsystem subjected to stochastic loadings is investigated. Jet vane TVC (JVTVC) is used in many aerospace liquid and solid propulsion systems. For the purpose of this work, JVTVC structural reliability of a solid rocket propulsion system is computed using an explicit closed-form limit state function. The JV structure is influenced by the internal ballistic loads emanating out of the solid rocket propulsion internal ballistic, whose performance is modeled via a one-dimensional uniform flow assumption at the engine steady operating condition. Subsequently, JV structural reliability is predicted using the... 

This study is concerned with the general motion of a guided flexible launch vehicle idealized as a non-uniform beam under continuous thrust action. The governing equations of motion are derived following the Lagrangian approach and generalized coordinates. The rigid motion consists of the conventional vehicle velocities (rotational and translative), whereas the elastic motion, introduced through modal substitution, represents the vehicle local lateral and transverse displacements relative to a mean body axis system. A complete simulation routine has been developed, which allows for investigation of the influence of variuos vibrational forcing functions, local stiffness changes and the... 

Reaction thrusters (RTs) are used as an alternative to momentum exchange devices when disturbance torques exceed the control authority of momentum exchange devices. The reaction control system (RCS) can employ some rocket thrusters to provide attitude control during the thrusting or coast phase. Within the control loop, the RCS's target could be either achieving and keeping a certain attitude or controlling the rate of an attitude change. In the coast phase, some tasks such as preacceleration, settling of liquid propellant, damping of structural vibrations, providing a velocity increment to separate stages and payloads, and carrying out orbital and nonorbital maneuvers may be included in its...