Shear creep and failure model of bonded interface in solid rocket motors

Simulation of particulate flows in combustion chambers of solid rocket motors with multiscale model

Impact of thermal protections insulation layer on solid rocket motor residual thrust

Ultrasonic measurement and data processing method for the dynamic burning rate of large-scale solid rocket motors

Film cooling characteristics of a pintle in a thrust-controlled solid rocket motor

Solid rocket motors (SRMs) play a pivotal role in space exploration owing to their reliability and high thrust-to-weight ratios. SRM propellant health monitoring is in critical demand owing to the complex operational scenarios throughout the entire life cycle of SRMs. To achieve in situ detection of three-dimensional stress, this study introduces a novel flexible three-dimensional stress sensor (FSS). First, a liquid metal pressure-sensing element with a variable cross-section was designed and numerically modeled. The performance of the FSS under different loading conditions was analyzed using finite element modeling. The sensing element prototype was fabricated using mold casting and liquid metal injection methods. The fabricated sensing-element prototype with an area ratio of 1:5 exhibited a sensitivity coefficient of 1.5%/kPa at a pressure of 300 kPa, a maximum hysteresis error of 3.98%, and a stability error of 0.17%. Finally, the FSS was developed by integrating multiple pressure-sensing elements and encapsulating the force-concentrating layers. The fabricated FSS prototype was characterized using simulated propellant experiments. Via comparison with the simulation results, the FSS was found to detect multiaxial stress differences when embedded within a propellant.

ABSTRACT With the further development of the aerospace industry, solid rocket motors urgently require materials with superior mechanical properties and ablation resistance for internal insulation layers. This study innovatively introduces newly synthesized four polyphosphazenes (PPNs) bearing diverse side‐chain functionalities, including diallylamine polyphosphazene (VPN), acetylenyl aniline polyphosphazene (AYP), naphthylamine polyphosphazene (NLP), and allyl phenoxy polyphosphazene (APP), into EPDM composites as functional fillers. These resulting composites all exhibited excellent mechanical and ablation resistance properties, among which EP‐NLP exhibited the most outstanding performance, showing a 1089% increase in elongation at break and a 60.74% reduction in linear ablation rate, achieving values of 918.94% and 0.042 mm/s, respectively. In‐depth analysis of the morphology, composition, and structure of the char layer revealed that PPNs promote the formation of phosphate structures and SiC during ablation, which led to the formation of a denser char with higher hardness and an increased degree of graphitization. The underlying mechanisms for these improvements are systematically investigated, offering a promising design strategy for advanced thermal protection systems in aerospace and solid rocket motor applications.

Abstract The nonlinear mechanical behavior and temperature sensitivity of HTPB propellant for solid rocket motors were investigated. The rate-dependent mechanical properties of the propellant were examined through a combination of experiments and numerical simulations. Experimental results demonstrate that the tensile mechanical properties of HTPB propellant are rate-dependent at 223 K and 323 K; stresses at a given strain gradually increase with increasing strain rate. By use a generalized nonlinear ZWT intrinsic model, the tensile mechanical behavior of HTPB propellant under a wide range of strain rates was to described. A numerical simulation of a uniaxial tensile test was performed using a UMAT subroutine. The results demonstrate that the model accurately represents the mechanical properties of the HTPB propellant.

An inverse prediction and experimental study for the internal insulator boundary conditions of solid rocket motor

Experiments show that, during decompression, solid rocket motors (SRMs) may undergo a downward deviation in the combustion chamber pressure or extinction. To clarify the mechanisms and laws of these phenomena, the microscale combustion of ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellants and the depressurization process of different SRMs are simulated with a pressure range of 1∼10.2 MPa and a pressure change rate range of −300 to −1000 MPa/s. The results indicate that the dynamic characteristics of the motor can be divided into three categories: monotone stability, pit-and-stability, and extinction. Under slow depressurization, the heat exchange of the system exhibits no obvious lag, unlike that observed for the pressure-change process in the combustion chamber, and monotonic stability occurs. Under fast depressurization, the solid-phase heat conduction process lags behind the change in the combustion chamber pressure, and the transient burning rate varies, resulting in pit-and-stability. A larger depressurization rate produces a greater deviation in the transient burning rate. When the depressurization process is rapid, the pyrolysis and heat conduction processes in the reaction zone on the propellant surface lag the change in combustion pressure, and the propellant is extinguished, causing extinction. A method for constructing the SRM relaxation coefficient distribution based on its design and propellant parameters is established. By determining the position of characteristic points within the relaxation coefficient distribution, the dynamic operating characteristics of the SRM under depressurization are revealed.

This paper outlines the design and implementation of a Gough-Stewart (G-S) platformbased test stand for static testing of solid rocket motors, specifically for the ISRO’s Gaganyaan CES Motors which are tested vertically. Static testing is crucial for validating design assumptions and ascertaining performance of these solid rocket motors. The G-S platform integrated with tapered notch joint flexures with 300 kN capacity column-type load cells are used for the force/moment measurement. The research emphasizes the role of flexure hinges in minimizing friction and backlash, thereby improving sensitivity and reliability in thrust measurements. A detailed design methodology is presented, highlighting key geometric parameters and material properties necessary for its optimal performance. The G-S platform employs a 6-3 configuration, enabling accurate measurement of thrust and moments under various loading conditions. The analysis underscores the importance of considering the centre of rotation and its motion during deflection to avoid parasitic movement, ensuring the stability of the mechanism. The tapered notch flexure demonstrates superior performance over traditional spherical joints, particularly due to lower stress levels and ease of manufacturing. Finite Element Method (FEM) analysis indicates significant stress reductions, revealing maximum values of 684 MPa for conventional rectangular designs and 556 MPa for the tapered configuration, highlighting the structural advantages of the proposed design

This work explores solid rocket motor grain design, leveraging additive manufacturing techniques based on slurry deposition and UV-curing. The objective is to develop an automated design procedure to identify optimal solutions that meet mission requirements, exploiting new geometries and ballistic configurations previously unattainable with the classical mix–cast–cure manufacturing process. The design procedure is based on a stochastic optimization approach coupled with surrogate modeling of the pressure–time response, considering variable geometrical and ballistic parameters. Several surrogate models were tested after the creation of suitable databases through the computation of pressure evolution for different configurations. The most appropriate surrogate model was selected and applied within optimization routines to evaluate individual designs. The optimizer identifies the most suitable configuration to obtain the desired pressure–time response and to meet motor requirements. Different design approaches have been tested to evaluate the ballistic distribution’s influence on performance and how it can be leveraged to meet requirements, even with significant modifications in grain geometry. The results show that the proposed procedure is able to effectively achieve the expressed requirements, successfully handling the novel design environment. Furthermore, they highlight the strong influence of the ballistic distribution on performance and show how it can be successfully exploited to guide grain design.

Fundamental knowledge on how polymer architecture affectscuringand material properties of solid rocket motors (SRMs) using hydroxyl-terminatedpoly­(butadiene) (HTPB) as a prepolymer has historically been basedon studies employing impure samples. Herein, we present the synthesisof highly controlled HTPB via reversible addition–fragmentationchain-transfer (RAFT) polymerization and explore how the hydroxylgroup content affects viscosity and pot-life. We further examine thekinetics of curing in order to gain a mechanistic insight. The synthesisof these polymers involved the design and preparation of chain-transferagents, which allowed for star-shaped polymers via the Z-group approach.We demonstrate that increasing the number of hydroxyl groups servesto decrease the pot-life, despite the fact that network forming reactions(e.g., urethane formation) counterintuitively proceed more slowly,providing insight into the mobility of reactive chain ends duringcuring reactions relevant to SRM loading. Further, the architecturallypure materials presented here all have longer pot-lives than the commerciallyobtained HTPB, highlighting the benefit of using more controlled polymersfor energetics applications. This represents the first examinationof these processes using architecturally pure HTPB, a rare exampleof homopolymerization of butadiene using RAFT polymerization and afacile approach to more complex structures of poly­(butadiene) thanhave been reported previously.

Numerical investigation of combustion instability in solid rocket motors under overload conditions

Abstract Addressing the issue of particle erosion of the thermal insulation layer in graphite nozzles subjected to high-concentration particle flow scouring, a numerical simulation of two-phase flow was conducted using the Standard k-ε Turbulence Model and the Particle Trajectory Model. The particle erosion rates of graphite materials were computed using the Oka particle erosion model and then compared with the experimental results of particle erosion. The results of the simulation calculations indicate that: After injecting solid particles into the nozzle, compared to the pure gas-phase flow field, the temperature at the fluid-solid coupling interface decreases in the contraction section, first decreases and then increases in the throat section, and significantly rises in the expansion section; In particle erosion simulation calculations, a higher mass flow rate corresponds to a greater erosion rate. Moreover, in studies on the factors influencing particle erosion, it has been found that the mass flow rate exerts a more significant impact on the erosion rate than the particle diameter does; reducing the particle mass flow rate and optimizing the nozzle convergence angle are effective methods to mitigate mechanical erosion.

Numerical study on the performance of pintle controlled solid rocket motor based on fluid-thermal-structure interaction

Multifidelity Model–Assisted Knowledge Transfer Optimization Method for Computationally Intensive Solid Rocket Motor Design

Heat and mass transfer mechanism model of AP/HTPB propellant based on micro-CT in the ignition stage of a solid rocket motor

Abstract Aiming at the problem that the composite case of solid rocket motors is prone to typical damages such as delamination and fiber breakage during manufacturing, transportation, and storage, this paper establishes models of intact cases and cases with delamination damage based on laminate theory. The mechanical response of the cases under an internal pressure of 1.5 MPa was systematically analyzed, and the damage characteristics of delamination at different positions were focused on. The simulation results show that: there is significant stress concentration at the delamination damage location in the head section, and the strain at the center of the damage is lower than that in the surrounding area; the stress and strain at the centers of the two damage locations in the cylinder section are both smaller than the surrounding values, and crescent-shaped local stress concentration distribution appears around the front and rear of the damage areas; the evolution trends of damage strain in the fiber direction at different damage locations in the cylinder section are highly consistent.

This study develops a three-dimensional multi-physics framework for simulating ignition transients in solid rocket motors (SRMs), explicitly resolving the coupled interactions of transient compressible flow, heat transfer, combustion, and structural dynamics. The methodology introduces a weighted residual formulation based on common-refinement discretization for fluid–structure interface data transfer, which rigorously enforces conservation laws while minimizing numerical errors across non-matching meshes. Temporal synchronization across physical domains is achieved through predictor–corrector iterations, ensuring stability in strongly coupled simulations. Validation employs a supersonic shock-panel interaction benchmark, where data exchange tests between mismatched fluid and solid surface meshes confirm the method’s accuracy and robustness properties. Quantitative comparisons with experimental measurements and reference numerical solutions demonstrate its accuracy in handling compressible fluid–structure coupling. Application to an SRM ignition case captures coupled flow evolution, flame propagation, and propellant structural responses. The coupled simulation reveals distinct flame spreading patterns and dynamic burning surface evolution, directly linked to chamber pressure variations unobserved in single-field analyses. Furthermore, the results identify the propellant’s viscoelastic behaviour and ignition-induced structural vibrations, underscoring the necessity of multi-physics coupling to resolve transient ignition mechanisms. This work establishes a computational foundation for analyzing critical interactions governing SRM ignition dynamics.