Showing papers on "Solid-fuel rocket published in 2013"

Chemical erosion of carbon-phenolic rocket nozzles with finite-rate surface chemistry

Abstract: Ablative materials are commonly used to protect the nozzle metallic housing and to provide the internal contour to expand the exhaust gases in solid rocket motors. Because of the extremely harsh environment in which these materials operate, they are eroded during motor firing with a resulting nominal performance reduction. The objective of the present work is to study the thermochemical erosion behavior of carbon-phenolic material in solid rocket motor nozzles. The adopted approach relies on a validated full Navier–Stokes flow solver coupled with a thermochemical ablation model, which takes into account finite-rate heterogeneous chemical reactions at the nozzle surface, rate of diffusion of the species through the boundary layer, pyrolysis gas and char-oxidation product species injection in the boundary layer, heat conduction inside the nozzle material, and variable multispecies thermophysical properties. The results obtained with the proposed approach are compared with two sets of experimental data: subs...

Mechanical Erosion of Graphite Nozzle in Solid-Propellant Rocket Motor

Abstract: A detailed theoretical/numerical framework is established to study the mechanical erosion of graphite-nozzle materials in solid rocket motors with aluminized ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellants. The analysis is based on a combined Eulerian–Lagrangian approach for treating multiphase motor flowfields. The multicomponent reacting gas-phase dynamics is formulated using the conservation equations of mass, momentum, and energy in the Eulerian framework. Turbulence closure is achieved using the standard k-e two-equation model. The dispersed phase, consisting of aluminum and alumina droplets, is treated in the Lagrangian framework. Combustion of aluminum droplets to aluminum-oxide smoke is considered. Two empirical correlations are first calibrated and then employed to predict the mechanical-erosion rate of the nozzle surface. The estimated erosion rates fall within the range of the available experimental data. Mechanical erosion is prevalent in the convergent section of ...

Stability analysis and numerical simulation of simplified solid rocket motors

Abstract: This paper investigates the Parietal Vortex Shedding (PVS) instability that significantly influences the Pressure Oscillations of the long and segmented solid rocket motors The eigenmodes resulting from the stability analysis of a simplified configuration, namely, a cylindrical duct with sidewall injection, are presented They are computed taking into account the presence of a wall injection defect, which is shown to induce hydrodynamic instabilities at discrete frequencies These instabilities exhibit eigenfunctions in good agreement with the measured PVS vortical structures They are successfully compared in terms of temporal evolution and frequencies to the unsteady hydrodynamic fluctuations computed by numerical simulations In addition, this study has shown that the hydrodynamic instabilities associated with the PVS are the driving force of the flow dynamics, since they are responsible for the emergence of pressure waves propagating at the same frequency

Detectability of Delaminations in Solid Rocket Motors with Embedded Stress Sensors

Abstract: A finite element model is used to investigate the effect of delaminations on the radial stress distribution along the bondline during the cooling process of a solid rocket motor composed of propellant, insulation, and casing. Under the assumption of stress sensors evenly distributed along the circumference of the interface between the propellant and insulation, a relationship is established between the debond angle, the number of sensors, and the required sensor accuracy. Two approaches are proposed to detect debonds based on the radial stress readings from these embedded sensors. In addition, a quantitative mapping is obtained between the debond size and the sensor data to inversely estimate the extent of the delamination. It is demonstrated that the proposed framework can detect delaminations in solid rocket motors.

Spectral and statistical analysis of noise from reusable solid rocket motors

Abstract: As part of investigations into the design of next-generation launch vehicles, near and far-field data were collected during horizontal static firings of reusable solid rocket motors. In addition to spectral analysis at individual microphone locations, the spatial and temporal variation of overall and one-third octave band pressure levels at sideline and polar arc arrays is considered. Analysis of the probability density functions reveals positively skewed pressure waveforms, but extreme skewness in the first-order estimate of the time derivative because of the presence of significant acoustic shocks. However, plume impingement is the likely cause of reduced high-frequency levels and skewness at far-downstream positions.

Solid rocket thrust vector control

Abstract: Thrust vector control systems that superimpose a side force on the motor thrust, steering being achieved by the side force causing a moment about the vehicle center of gravity are described. A brief review of thrust vector control systems is presented, and two systems, flexible joint and liquid injection, are treated in detail. Treatment of the flexible-joint thrust vector control system is limited to the design of the flexible joint and its insulation against hot motor gases. Treatment of the liquid injection thrust vector control system is limited to discussion of the injectant, valves, piping, storage tanks, and pressurization system; no evaluation is presented of the nozzle except for (1) the effect of the injectant and erosion at the injection port and (2) the effect of injection on pressure distribution within the nozzle.

Cold tests and the dynamic characteristics of the pintle type solid rocket motor

Abstract: Dynamic characteristics of a pintle-perturbed conical nozzle are studied theoretically, experimentally, and numerically under the condition of constant mass flow rate. Conventional one-dimensional nozzle theory in conjunction with a two-dimensional axisymmetric flow solver calculates the internal flow parameters in the nozzle equipped with the pintle. The commercial flow solver is used based on the strongly-coupled flow equation system which is closed with one-, or two-equation turbulence models. Theoretical and numerical flow parameters are properly validated by the experiments. For the dynamic characteristics of the pintle nozzle, performance variations are examined in terms of the free volume size, the pintle actuating speed and pintle geometries. The dynamic characteristics of the pintle-perturbed nozzle largely depend on the mass flow rate through the nozzle throat which is a strong function of the reduced throat area and chamber pressure. It also depends on the pintle activation because the nozzle throat and the chamber pressure change with the extent of the pintle displacement.

Eulerian modeling and simulation of polydisperse moderately dense coalescing spray flows with nanometric-to-inertial droplets : application to Solid Rocket Motors

Abstract: In solid rocket motors, the internal flow depends strongly on the alumina droplets, which have a high mass fraction. The droplet size distribution, which is wide and spreads up with coalescence, plays a key role. Solving for unsteady polydisperse two- phase flows with high accuracy on the droplet sizes is a challenge for both modeling and scientific computing: (1) very small droplets, e.g. resulting from the combustion of nanoparticles of aluminum fuel, encounter Brownian motion and coalescence, (2) small droplets have their velocity conditioned by size so they coalesce when having different sizes, (3) bigger droplets have an inertial behavior and may cross each other’s trajectory, and (4) all droplets interact in a two-way coupled manner with the carrier phase. As an alternative to Lagrangian approaches, some Eulerian models can describe the disperse phase at a moderate cost, with an easy coupling to the carrier phase and with massively parallel codes: they are well-suited for industrial computations. The Multi- Fluid model allows the detailed description of polydispersity, size/velocity correlations and coalescence by separately solving “fluids” of size-sorted droplets, the so-called sections. In the present work, we assess an ensemble of models and we develop a numerical strategy to perform industrial computations of solid rocket motor flows. (1) The physics of nanoparticles is assessed and included in a polydisperse coalescing model. High order moment methods are then developed: (2) a Two-Size moment method is ex- tended to coalescence to treat accurately the physics of polydispersity and coalescence and the related numerical developments allow to perform applicative computations in the industrial code CEDRE; (3) a second order velocity moment method is developed, together with a second order transport scheme, to evaluate a strategy for a moderately inertial disperse phase, and academic validations are performed on complex flow fields; (4) a time integration strategy is developed and implemented in CEDRE to treat efficiently two-way coupling, in unsteady polydisperse cases including very small particles. The developments are carefully validated, either through purposely derived analytical formulae (for coalescence and two-way acoustic coupling), through numerical cross-comparisons (for coalescence with a Point-Particle DNS, for applicative cases featuring coalescence and two-way coupling with a Lagrangian method), or through available experimental results (for coalescence with an academic experiment, for the overall physics with a sub-scale motor firing). The whole strategy allows to perform applicative computations in a cost effective way. In particular, a solid rocket motor with nanoparticles is computed as a feasibility case and to guide the research effort on motors with nanoparticle fuel propellants.

High-energy metal fuels for rocket propulsion: characterization and performance

Abstract: paper describes a joint international effort to improve solid propellant performance within the framework of a FP7 European Project. Several metallized solid rocket propellants, of the broad family AP/HTPB/Metal in the ratio 68/14/18, were experimentally analyzed seeking to optimize the delivered specific impulse by identifying the most suitable high-energy fuel. Keeping the same nominal composition, different metallic fuels (including micrometric and nanometric Al, AlH3, and a variety of dual metal compositions) were characterized, tested, and contrasted to a conventional micrometric aluminum (30 µm average grain size) certified for space flights. In order to overcome the intrinsic performance limitations of the matrix AP/HTPB, a new matrix consisting of ADN/GAP satisfying also the need for environmentally benign propellant formulation was considered as well. A comparative analysis between the two solid propellant systems in terms of ideal thermochemistry and experimental combustion properties reveals advantages and disadvantages of both. Overall, it is judged worthwhile to develop ADN/GAP propellants, with or without metallic fuels, to enhance the current status of solid rocket propulsion. Controlling morphology and mechanical properties of ADN/GAP compositions and understanding their flame structure and aggregation/agglomeration properties are the main issues still challenging industrial users.

Solid rocket ramjet fuel gas flow regulation device driven by linear motor

Abstract: The invention discloses a solid rocket ramjet fuel gas flow regulation device driven by a linear motor. The nozzle throat area of a fuel gas generator is changed through the linear motor driving a cone-shaped valve head, and thus the fuel gas flow of the fuel gas generator is regulated; an inner shell structure is formed in the fuel gas generator, a thermal insulation bushing is mounted in an inner shell, the tubular linear motor is arranged in the thermal insulation bushing, a rotor of the linear motor is fixed in the thermal insulation bushing, a stator of the linear motor is fixedly connected with one end of a valve rod, the other end of the valve rod is fixedly connected with the cone-shaped valve head which stretches into a spray pipe of the solid fuel gas generator, one end, close to the cone-shaped valve head, of the valve rod is matched with an inner hole of the thermal insulation bushing, an annular groove is arranged, a movable sealing piece is arranged in the annular groove, and a pressure sensor is mounted at a rear seal head of the fuel gas generator. According to the solid rocket ramjet fuel gas flow regulation device driven by the linear motor, fuel gas flow can be accurately and randomly regulated, the precision is high, the structure is simple and compact, the size is small, the weight is light, and the sealing effect is reliable.

High-Pressure Burning Rate Studies of Solid Rocket Propellants

Abstract: Increasedrocketmotorperformanceisamajordriverinthedevelopment of solid rocket propellant formulations for chemical propulsion systems. The use of increased operating pressure is an option to improve performance potentially without the cost of reformulation. A technique has been developed to obtain burning rate data across a range of pressures from ambient to 345 MPa. The technique combines the use of a low loading density combustion bomb with a high loading density closed bomb technique. A series of nine ammonium perchlorate (AP) based propellants were used to demonstrate the use of the technique, and the ‘

Analysis of Major Defects and Nondestructive Testing Methods for Solid Rocket Motor

Abstract: The paper introduces the major defects and its causes of solid rocket motor,the harm and effects of the combustion chamber defects for the stability of motor were clarified,the main methods and their advantages and disadvantages of defect detection currently used in solid rocket motor are also cited and analyzed, and it points out the developing trends about various of detection technology used in conjunction.

Multichannel solid rocket engine ignition sequence control method

Abstract: The invention relates to a multichannel solid rocket engine ignition sequence control method. Propellant ignition time and two-way pulser ignition triggering excitation time which is specially required are accurately controlled through accurate sequence triggering control according to a known pressure intensity-time curve, and therefore experimental measurement work of composite propellant pressure intensity coupling response functions of a random pulse excitation method can be carried out under the condition that the pulse triggering excitation time is accurately controlled. The greatest characteristic of the multichannel solid rocket engine ignition sequence control method is that T-shaped burner ignition time and the two times of pulse excitation time are accurately controlled, accurate pulse triggering excitation can be carried out on T-shaped burner experiment under different working conditions through adjustment of a time interval of a high-speed timer according to an engine internal trajectory pressure intensity curve, and the precision of the triggering time interval is 10 ms.

CuO/Al Thermites for Solid Rocket Motor Ignition

Abstract: Fast and repeatable ignition transients for small solid rocket combustors can be difficult to achieve. This work sets out to characterize a CuO/Al thermite mixture to fill this need. Igniter function was determined using high-speed imaging, allowing an examination of product droplet size and combustion time as a function of packaging technique. Safety testing (electrostatic discharge, drop weight impact, and friction) indicated that this material is far safer than existing ignition compounds. A simple dual-criteria ignition model is applied to igniter sizing, and our modeling results were successfully evaluated using hot fire tests of motors with various exposed propellant surface conditions. The end result is a safe, inexpensive, reliable, and readily available method of igniting small (500 g–50 kg propellant mass) solid rocket combustors.

Cartridge with rapidly increasing sequential ignitions for guns and ordnances

Abstract: A cartridge may be loaded with a powder column containing stratified, stacked layers of propellant, each powder layer over-compressed to a specified degree, with the burn rate controlled by the specified degree of over-compression applied to each respective powder layer. The application of a highly compressed powder column reduces the burn rate, and may force one or more of the powder layers to launch with the projectile down the barrel. Accordingly, the powder column is forced to burn in a manner similar to fuel burning in a solid fuel rocket engine. This greatly reduces the pressure(s) developed in the chamber, and permits the force of the burning powder to be efficiently focused on forward propulsion. The rapidly increasing set of sequential ignitions provides higher and higher energy densities with each subsequent ignition, and creates a more uniform linear acceleration of the projectile for the full length of the target barrel.

Solid rocket motor grain burn back analysis using level set methods and Monte-Carlo volume integration.

Abstract: We employ the level set method to perform coupled grain burn back analysis in solid rocket motor simulations. A method of generating a signed distance function from STL files for the initialization of the level set function is given. Monte-Carlo integration techniques are applied to calculate the burning surface and port area parameters from the evolved implicit representation of the burning surface. Multiple timescales are used for improved efficiency of the grain regression coupling with the internal ballistics code.

Propellant trade-off analysis for upper stage solid rocket motors performance

Abstract: Aim of this paper is to perform a propellant trade-off analysis in order to determine the propellant formulation able to maximize solid rocket motor performance for upper stage solid rocket motors (SRMs). The study is performed with the use of a 0D quasi-steady model of SRM internal ballistics developed on this purpose, which assumes the chemicalequilibrium in the combustion chamber up to the nozzle throat, frozen flow conditions in the nozzle divergent, and takes into account the nozzle throat erosion using a validated semi-empirical correlation of the throat recession rate. Three different upper stage SRM configurations are selected for the propellant trade-off analysis. The SRM configurations are inspired in terms of design to the available data in the open literature of three Zefiro family SRMs: Zefiro 23 and Zefiro 9A, second and third stage of VEGA launcher, and Zefiro 40, candidate for the evolution of Zefiro 23. Results indicate that, with respect to the baseline propellant HTPB 1912 (19 % aluminum 12 % HTPB), a gain in the performance can be obtained for propellant formulation with a higher aluminum loading and roughly the same HTPB mass fraction. The optimum aluminum loading increases with respect to the baseline formulation for SRM configurations characterized by high nozzle throat erosion.

Numerical investigation of the flow of ultradisperse particles of the aluminum oxide in the solid-fuel rocket engine nozzle

Abstract: The work deals with the two-phase flow investigation. The computations were done for a continuous coagulation model within the framework of the phenomenological multi-fluid model of the medium. A conclusion was drawn that the diminution of the particles size leads to a reduction of two-phase losses in the nozzle unit of the solid-fuel engine.