Showing papers on "Solid-fuel rocket published in 2003"

Azido Polymers—Energetic Binders for Solid Rocket Propellants

Abstract: High-energy solid rocket propellants are composite materials having a binder [hydroxy terminated polybutadiene (HTPB)], high-energy additives [e.g., ammonium perchlorate (AP)], and pyrolants (metal...

Mechanical analysis on rocket propellants

Abstract: The mechanical properties of solid rocket propellants are very important for good functioning of rocket motors. During use and storage the mechanical properties of rocket propellants are changing, due to chemical and mechanical influences such as thermal reactions, oxidation reactions or vibrations. These influences can result in malfunctioning, leading to an unwanted explosion of the rocket motor. Most of modern rocket propellants consist of a polymer matrix (i.e. HTPB) filled with a crystalline material (i.e. AP, AN). However, the more conventional double base propellants consist of a solid gel matrix with additives, such as stabilizers. Both materials show a mechanical behaviour, quite similar to that of general polymers. To describe the material behaviour of both propellants a linear visco-elastic theory is often used to describe the mechanical behaviour for small deformations. Because the time-temperature dependency is also valid for these materials a mastercurve can be constituted. With this mastercurve the response properties (stiffness) under extreme conditions can be determined. At TNO-PML a mastercurve of a double base propellant was constituted using dynamical mechanical analysis (DMA) and compared with a mastercurve reduced from conventional (static) stress relaxation tests. The mechanical properties of this double base propellant determined by DMA were compared with conventional (quasi-static) tensile test results.

A Review of Analytical Methods for Solid Rocket Motor Grain Analysis

Abstract: Analytical methods for solid rocket motor grain design are proving to be tremendously beneficial to some recent efforts to optimize solid-rocket propelled missiles. The analytical approach has fallen out of favor in recent decades; however, for some classes of grains, the analytical methods are much more efficient than grid-based techniques. This paper provides a review of analytical methods for calculating burn area and port area for a variety of cylindrically perforated solid rocket motor grains. The equations for the star, long spoke wagon wheel, and dendrite grains are summarized and the development of the burn-back equations for the short spoke wagon wheel and the truncated star configurations are included. This set of geometries and combinations of these geometries represent a very wide range of possibilities for two-dimensional grain design. Introduction In many practical solid rocket motor design efforts, final geometric designs for grains are arrived at using numerical layering techniques. This process is geometrically versatile and imminently practical for cases in which small numbers of final geometries are to be considered. However, for a grain design optimization process in which large numbers of grain configurations are to be considered, generating grids for each candidate design is often prohibitive. For such optimization processes, analytical developments of burn perimeter and port area for two-dimensional grains are critically important. Most modern texts on solid rocket propulsion do not provide geometric details for grain design. This paper will offer a review of analytical methods for determining burn area and port area as a function of burn distance for a selection of common grain designs. Analytical developments for solid rocket motor grains were much more prevalent in the decades before widespread use of microcomputers. A summary of one version of the burn back equations for the star grain and for part of one type of wagon wheel can be found in Barrere. Analytical methods have also been developed for the truncated star and for the dendrite. Other potential grain configurations are described in NASA publications but very few geometric details are given in such publications. 1 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 20-23 July 2003, Huntsville, Alabama AIAA 2003-4506 Copyright © 2003 by Roy Hartfield. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Star Grain Geometry Grain geometries are generally described using lengths and angles defined in the cross section. A sample burn back diagram is shown in Figure 1 and the geometric definition diagram for the familiar star grain geometry is shown in Figure 2. Since some of the geometric equations for the burn perimeter and port area for the star grain have been developed and published, only a summary of this geometry is included here. Figure.1 Sample Star Grain Figure 2. Star Grain Geometry The geometric relationship between the two primary angles in the geometry definition can be written as:

Effect of Nozzle Cavity on Resonance in Large SRM: Numerical Simulations

Abstract: The nozzle design effect on sound production is investigated to improve the understanding of the aeroacoustic coupling that occurs in solid rocket motors with a submerged nozzle. Earlier analytical and experimental work demonstrated that flow-acoustic coupling is observed only for submerged nozzles for which the sound pressure level increases linearly with the nozzle cavity volume. Numerical simulations of the flow-acoustic coupling phenomena and in particular of the effect of the nozzle cavity volume on the pressure pulsations are performed using the code CPS. The numerical and experimental pressure spectra are compared. The frequencies are well simulated by the numerical code even if the pressure levels are overestimated. The nozzle design effect on sound production is also observed with a reduction of pressure level of 55% when the nozzle cavity is removed. Furthermore, the nozzle cavity modifies the flowfield around the nozzle head. With the cavity, the recirculation bubble is shorter, and the flow close to the nozzle head presents high amplitudes of radial mean velocity and fluctuation. That explains why the vortices break up when interacting with the nozzle head. With the cavity, the vortices shed by the inhibitor move along the border of the recirculation bubble and then pass in front of the cavity entrance, where they generate sound by interacting with the velocity fluctuations induced by the cavity volume. This results in a strong interaction between the vortices and the nozzle, which leads to large pressure oscillations.

Numerical Simulation of Distributed Combustion in Solid Rocket Motors with Metalized Propellant

Abstract: An Eulerian‐Lagrangian two-phase approach suitable for the numerical simulation of the multiphase reacting internal e ow in a solid rocket motor with a metalized propellant is discussed. An Eulerian description has been used to analyze the motion of the continuous phase that includes the gas as well as the small (micrometer-sized ) particulates, whilea Lagrangian description is used for the analysis of the discrete phase that consists of the larger particulates in the motor chamber. An empirical model is used to compute the combustion rate for agglomerates, whereasthecontinuous-phasechemistry istreatedusingchemicalequilibrium.Acomputercodeincorporating this analysiswasusedtosimulatethereactinge owinasolidrocketmotorwithanammoniumperchlorate (AP)/hydroxyl terminatedpolybutadiene (HTPB)/aluminum(Al)propellant.Thecomputedresultsindicatethattherelativelyslow combustion rate of aluminum droplets can result in an extended combustion zone in the chamber rather than a thin reaction region. Thepresenceof the extended combustion zone resultsin thechamber e owe eld being far from isothermal and the chemical composition being far from uniform, as would be predicted by a surface combustion assumption.Thetemperatureinthechamberincreasesfromabout2600Katthepropellantsurfacetoabout3550 K inthecore. Similarly thechemicalcomposition andthedensity ofthepropellantgasalso showspatiallynonuniform distribution in the chamber. The analysis discussed provides a moresophisticated toolfor solid rocket internal e ow predictions than is presently availableand can beuseful in studying apparent anomalies and improving the simple correlations currently in use.

Particle Velocity on Solid-Propellant Surface Using X-Ray Real-Time Radiography

Abstract: In a solid rocket motor using aluminized composite solid propellant and submerged nozzle, two-phase flow needs to be investigated by both experiment and computation. The boundary conditions for the ejecting particles constrain their trajectories; hence, these affect the two-phase flow calculations and, thus, significantly affect the evaluation of the slag accumulation. A new method to determine the velocities of particles on the solid-propellant surface was developed, which is based on the x-ray real-time radiography (RTR) technique and coupled with the two-phase flow numerical simulation. A method was developed to simulate the particle ejection from the propellant surface. The moving trajectories of metal particles in a firing combustion chamber were measured by using the RTR high-speed motion analyzer. Image-processing software was also developed for the RTR images so that the trajectories of particles could be obtained. Numerical simulations with different propellant-surface boundary conditions were performed to calculate particle trajectories. By comparing the two trajectories, an appropriate boundary condition on the propellant surface was inferred. The present method can be extended to study the impingement of particles on a wall and other related two-phase flows.

Optimum design of fiber-reinforced composite cylindrical skirts for solid rocket cases subjected to buckling and overstressing constraints

Abstract: In order to increase the flight range of aerospace vehicles and the efficiency of solid rocket motors, designers attempt to reduce the weight of solid rocket motors. A skirt is a potential element for weight reduction in rocket motors as it leads to reduction of the total weight of solid rocket motor. Due to its significance for solid rocket motors, the objective of this paper is to investigate the optimal design of a fiber-reinforced composite cylindrical skirt subjected to a buckling strength constraint and an overstressing strength constraint under aerodynamic torque and axial thrust. The present optimal design problem involve in determining the best laminate configuration to minimize the weight of the cylindrical skirt. To find the optimal solution accurately and quickly, the hybrid genetic algorithm (HGA) is employed in this work. Buckling strength and overstressing strength of the fiber-reinforced composite cylindrical skirt are analyzed using classical laminate theory and elastic stability theory of thin shells. The Tsai-Wu failure criterion is employed to assess the first ply failure, and an overstressing load level factor is introduced to describe the failure strength. In addition, a buckling load factor is introduced to describe the buckling strength. Due to the critical issue of buckling strength, the effects of the design parameters on the buckling strength are investigated in this work. Finally, a practical design example of the proposed fiber-reinforced composite cylindrical skirt is investigated using the present analysis procedure. Results reveal that the fiber-reinforced composite cylindrical skirt laminated symmetrically with both cross-ply layers [0/90°] and angle-ply layers [+45/−45°] can sustain a great buckling load. Furthermore, the buckling strength of the skirt shell laminated with equal-hybrid between the angle-ply layers and the cross-ply layers is greater than that of the skirt shell laminated with over-weighted hybrid between the angle-ply layers and the cross-ply layers. Results provide a valuable reference for designers of aerospace vehicles.

Flow Simulation in Solid Rocket Motors Using Advanced CFD

Abstract: This paper describes a recently developed flow solver intended for the simulation of solid rocket motors. It solves the integral form of the 3-D Euler/NavierStokes equations on moving and/or deforming grids. The grids are structured and can be composed of an arbitrary number of blocks. The object oriented design of the flow solver enables an easy addition of physical modules for the modeling of turbulence, particles, smoke, species and radiation. The solver contains a module to move the interior grid including the block boundaries according to the boundary deformation. Furthermore, the flow solver is able to exchange data with an exterior program through a set of standard interfaces. This feature is used to supply the flow solver with boundary conditions (e.g. related to the burning surface) as well as with the movement of the surface grid due to burn back and/or structural deformation. The numerical schemes utilized and the implementation are described in some detail. The accuracy of the new flow solver is demonstrated for three solid rocket motors.

Development of erosive burning models for cfd predictions of solid rocket motor internal environments

Abstract: Four erosive burning models, equations (11) to (14). are developed in this work by using a power law relationship to correlate (1) the erosive burning ratio and the local velocity gradient at propellant surfaces; (2) the erosive burning ratio and the velocity gradient divided by centerline velocity; (3) the erosive burning difference and the local velocity gradient at propellant surfaces; and (4) the erosive burning difference and the velocity gradient divided by centerline velocity. These models depend on the local velocity gradient at the propellant surface (or the velocity gradient divided by centerline velocity) only and, unlike other empirical models, are independent of the motor size. It was argued that, since the erosive burning is a local phenomenon occurring near the surface of the solid propellant, the erosive burning ratio should be independent of the bore diameter if it is correlated with some local flow parameters such as the velocity gradient at the propellant surface. This seems to be true considering the good results obtained by applying these models, which are developed from the small size 5 inch CP tandem motor testing, to CFD simulations of much bigger motors.

Non-linear combustion stability prediction of srms using spp/ssp

Abstract: Solid rocket motors experience combustion stability problems when the interior acoustic modes become coupled with combustion processes. Current linear stability analysis codes can predict if a solid rocket motor will be unstable, but do not predict the severity of the problem. Two non-linear analytic approaches have been devised that predict the limiting pressure amplitudes of these unsteady motions. The first approach is based upon numerically solving a system of ordinary differential equations in time. The second approach presumes the final relationship between the acoustic mode shapes, the combustion processes and the losses in the system. The basic theory behind each approach is presented, followed by the waveforms predicted for three different chamber configurations, including the Advanced Solid Rocket Motor. Both of these approaches rely on an accurate determination of the linear problem, and recent improvements to this analysis are presented as well.

Modeling of Rocket Motor Ballistics for Functionally Graded Propellants

Abstract: Functionally Graded Solid Rocket Propellants are being developed at NSWC-Indian Head in conjunction with the University of Maryland. The approach being used treats these propellants as typical Functionally Graded Materials (FGMs), which by definition are structures that possess gradual variations in material behavior that enhance material and/or structural performance. For functionally graded propellants, Twin Screw Extrusion (TSE) processing is used to continuously vary the composition throughout a grain in a controlled manner. As a result, TSE processing allows the burning rates of propellants to be tailored as a function of burning web thickness. This in turn will allow for direct Thrust Magnitude Control (TMC) for a solid rocket motor, which has proven difficult to achieve in the past. To realize the benefits of functionally graded propellants in rocket motors, an Inverse Design Procedure (IDP) is being developed that couples processing, property, and performance models with mathematical optimization techniques to enable designers to determine realistic gradient architectures that will meet the performance objectives. An essential part of this program is the development of a model that is capable of predicting the ballistic performance of functionally graded propellants. The development of such a model requires that new parameters be taken into account that would not be considered for a conventional solid propellant. For instance, not only will the burning rate change as a function of pressure and initial temperature, but the burning rate characteristics will also change as a function of position in the grain. Furthermore, the density and the thermochemistry associated with the graded architecture of the propellant will be changing in a continuous manner, whereas the grain will conventionally be represented by a web with discrete thickness. The details of the ballistics model and the effect on performance predictions related to discrete representations of continuously graded architectures will be discussed in the paper.

Assessment on Analysis and Prediction Method Applied on Thrust Oscillation of Ariane 5 Solid Rocket boosters

Abstract: This paper is devoted to state-of-the art numerical simulation of thrust oscillations of segmented solid rocket motors with aluminized propellant. After the description of numerical tools, the first part of the paper deals with the second and the third peak of pressure oscillations observed at the end of the Ariane 5 P230 SRM operation. The study described proves that in such geometries, an accurate numerical model is necessary to reach a good level of fluctuation amplitudes simulation, with respect to experimental firings. This model must include reactive two-phase flow for aluminum combustion and fluid structure coupling. These two models have been taken into account in the last simulations and the results are in good agreement with the firing tests. But some assumptions had to be done. A large parametric study is running. The second part of the paper presents the first results obtained on a numerical parametric study about the unexpected behavior of solid particles in a flow with surface vortex shedding.

Probabilistic Risk Assessment of Solid-Propellant Rocket Motors

Abstract: An approach is developed for probabilistic risk assessment of the propellant contained in solid rocket motors Depending on the storage conditions, the propellant might be subjected to thermally induced loads that provokemechanical damage Time-dependent random functions for thermal loading are presented along with temperature-dependent and loading-rate-dependent structural capacity models Limit state functions are formulated for two critical structural responses, namely, bore cracking and propellant/insulant debonding Using first- and second-order reliability methods, instantaneous reliabilities are calculated and are used in progressive reliability computations The sensitivities of the structural reliabilities to statistical and probabilistic descriptions of capacity and response input parameters are investigated Example calculations for motor storage at various sites are used to demonstrate the methodology Progressive reliability estimates are shown to be lower than instantaneous reliability predictions and a better indicator of motor service life The major findings from sensitivity studies of the example problems here are that statistical values of propellant capacity (ie, mean and standard deviation) have the greatest influence on predicted service life, whereas probabilistic distribution is least influential Moreover, storage in an extremely cold environment has a much more significant effect on service life than does storage in moderately cold weather conditions Thus, it can be concluded that reducing variability in propellant capacities through material processing will lead to significant improvements in the service life estimate of solid rocket motors

Influence of Alumina Particles Heterogeneity on Particle Sizing and Radiative Properties Evaluation in Solid Rocket Plumes.

Abstract: Rocket propulsion by solid aluminized propellants produces large amounts of alumina particles that mainly contribute to the radiative properties of the plume. The optical properties of Al2O3 particles and their size distribution constitute the main factors that have to be evaluated in order to compare the measured radiative properties with numerical simulations. Shots experiments have been performed at ONERA (Office National d'Etudes et de Recherches Aerospatiales, France) on a subscale motor. For each shot, the particles were characterized by two experimental set-ups: an in situ Mie light-scattering granulometer and an impacting-collecting system. This paper presents the main results of the particle characterization derived from these two set-ups. We specially focus on the presence of hollow spherical particles and its impact on particle sizing and the evaluation of the radiative properties of the alumina particles. Nomenclature

Process for igniting a rocket engine and rocket engine

Abstract: A process for igniting a rocket motor or rocket engine is presented, wherein a fuel rich propellant, propellant mixture, or propellant streams for the rocket motor or rocket engine is ignited by decomposing at least one liquid igniter liquid to provide an oxygen rich hot gas.

Effect of a Sudden Change in Cross-Sectional Area of the Solid Rocket Motor Duct on Coagulation of Condensed Particles

Abstract: Results of numerical simulations are reported for two-phase flows with allowance for coagulation and fragmentation of particles of polydisperse condensate in the combustor duct of the solid rocket motor (SRM) with a sudden change in cross-sectional area typical of solid-propellant charges of a complex shape. It is shown that a sudden change in cross-sectional area can lead to a significant (multiple) coagulation-induced increase in the mean particle size. The calculation results are validated by a test series on a model SRM with the use of a laser system for diagnosing particle dispersion.

Stress analysis of propellant grain loaded in composite case motor under vertical storage

Abstract: Under vertical storage state of solid rocket motor (SRM), its propellant grain bears two main associate loads in a long period, that is, the heat load due to the temperature difference after the curing temperature tends to equilibrium state and self axial gravity load. By taking into account of the material properties and different loading conditions, and based on the linear elastic three dimensional finite element method, strain and stress of a SRM grain are calculated respectively under those loads, and some danger parts of grain and their interfaces are analyzed in special.

Numerical simulation of the form and development of rocket gas near flow field

Abstract: The complicated wave system exists around the near region of the solid rocket motor. The interaction between expansion and compressed wave is the important part of correlated study on plane-missile and missile-warship. The distribution of the pressure and temperature field of complicated wave system is the direct factor which causes the dynamical and hot impact. It is difficult to study the complicated properties of jet flow field by means of experimental method. A method of numerical analysis was applied to study the wave system existing in near rocket gas field and the initial shock wave of high-unexpanded gas jet flow. The properties of the near region of gas flow field have obtained from the numerical result. The data accord with those given in reference and provide helpful information.

Finite Element Simulation of a Space Shuttle Solid Rocket Booster Aft Skirt Splashdown Using an Arbitrary Lagrangian-eulerian Approach

Abstract: Explicit finite element techniques employing an Arbitrary Lagrangian-Eulerian (ALE) methodology, within the transient dynamic code LS-DYNA, are used to predict splashdown loads on a proposed replacement/upgrade of the hydrazine tanks on the thrust vector control system housed within the aft skirt of a Space Shuttle Solid Rocket Booster. Two preliminary studies are performed prior to the full aft skirt analysis: An analysis of the proposed tank impacting water without supporting aft skirt structure, and an analysis of space capsule water drop tests conducted at NASA's Langley Research Center. Results from the preliminary studies provide confidence that useful predictions can be made by applying the ALE methodology to a detailed analysis of a 26-degree section of the skirt with proposed tank attached. Results for all three studies are presented and compared to limited experimental data. The challenges of using the LS-DYNA ALE capability for this type of analysis are discussed.

Solid pocket motor and safety system

Abstract: PROBLEM TO BE SOLVED: To provide a solid rocket motor capable of preventing danger in advance when an unexpected situation such as fire occurs and the solid rocket motor during storage receives heat externally and a safety system capable of operating the solid rocket motor effectively. SOLUTION: This solid rocket motor for storage is provided with a body storing a solid propellant in a motor case, a nozzle attached to one end of the body, an igniter attached to the other end of the body or the nozzle, and a destruction mechanism attached detachably to the outer peripheral surface of the solid rocket motor and capable of destroying the solid rocket motor by a signal from the outside.

Modeling and Simulation of a Health Monitoring System in an Analog Motor

Abstract: : Finite element modeling of a cross section of a solid rocket motor is used to determine the relationship between several variables in a health monitoring system. The system consists of pressure sensors mounted on the inner case wall In a pressurized motor, differences among the sensor readings are indicative of crack growth in the propellant The computational data is used to determine the relationship between sensor sensitivity, the number of sensors, and the minimum detectable crack size. The method of determining the relationships is applicable to other loading conditions, such as thermal loading.

Numerical simulation of infrared radiation proper-ties of solid rocket engine exhaust plume

Abstract: In the case of certain parameters for concentration and temperature profile, particle and radiation properties of gas, the finite volume method in body-fitted coordinates is used to calculate the infrared spectral properties of the solid rocket exhaust plume with anisotropic scattering particles, results of which are compared with those of discrete ordinate method. Apparent spectral radiative intensities at 2.7μm and 2.95μm and band radiative intensity within 2.7～2.95μm are analyzed. Furthermore, the errors caused by isotropic scattering or no scattering approximation to non-linear anisotropy scattering model are investigated.

Temperature test of motor combustion gas flow field with thermographic instrument

Abstract: Radiant temperature of solid rocket motor combustion gas flow field was tested and measured by means of infrared thermographic instrument on the basis of the experiment, and the test results were analyzed and treated through data calibration of high temperature wind tunnel. The method for setting up the radiant coefficient is put forward to solve the infrared radiation temperature measurement problem for motor combustion gas flow field.

Performance analysis of thermal protection system of a solid rocket nozzle

Abstract: A coupled approach is adopted to solve the conjugate problem of fluid flow and heat transfer in solid rocket nozzles in order to achieve an optimum thermal protection system (TPS). The computational fluid dynamics (CFD) code to solve the Navier-Stokes equations for fluid flow in a rocket nozzle is coupled with the charring material ablation code through an energy balance at the active surface of the wall material. The present analysis compares well with the test results generated in-house as well as those reported in the literature.