Search Results (246)

The purpose of this paper is to present the development of an engineering level code for calculating hypersonic aerodynamics and convective heating, HI-Mach. Novel to this paper are the use of analytic methods for streamline tracing and the direct differentiation of geometric sensitivities for both forces and heat load. Independent panel inclination methods calculate the pressure distribution on the surface of a hypersonic vehicle. Normal shock relations provide the thermodynamic state on each panel. Streamlines are integrated using closed-form streamline equations. Flat plate formulas corrected for compressibility calculate the skin friction coefficient and acreage heat flux on each panel. Formulas for heating on stagnation points and lines, including effects of ellipticity and sweep, are used to calculate stagnation region heating. A method for obtaining the sensitivities of a quantity of interest with respect to the geometry in a hypersonic panel code is described. These are obtained using direct analytical derivatives. The approach is precise and has been thoroughly tested against finite differencing. HI-Mach provides results orders of magnitude faster than would be obtained by CFD. Results from HI-Mach are analyzed and compared to experimental results for the HL-20 lifting body geometry. For the aerodynamic characteristics, HI-Mach predicted force coefficients within 12% of experimental results at $M\infty =4.5$ and 21% at $M_{\infty }=1.6$. Heating results for the HL-20 match experimental and CFD results to within 20% over a wide range of operating conditions. Full article

Utilizing the pyrolysis reaction of endothermic hydrocarbon fuels to provide thermal protection for hypersonic vehicles is a feasible approach. The introduction of catalysts or cracking-initiating additives could promote hydrocarbon fuel cracking and increase the reaction heat sink. Catalysts such as ZSM-5 zeolite, Al₂O₃, and precious metals were commonly used for hydrocarbon fuel cracking. By optimizing their pore structure and acidity, their catalytic cracking performance can be effectively improved. These catalysts can function not only as catalytic coatings but also be dispersed in the fuel to act via quasi-homogeneous catalytic cracking. Additionally, small-molecule and macromolecular additives could crack at lower temperatures to generate active free radicals, thereby initiating the cracking of hydrocarbons and increasing the reaction heat sink. Under the conditions of a reaction temperature of 650–750 °C, a pressure of 3–5.5 MPa, and a fuel flow rate of 1 g/s, quasi-homogeneous catalysts can enhance the heat sink of hydrocarbon fuel cracking by 5–21%, while cracking-initiating additives can enhance it by 5.6–8.6%. Therefore, based on the different action modes of catalysts or additives, this review summarizes the recent research on improving the cracking of endothermic hydrocarbons from three aspects: coating catalysts, quasi-homogeneous catalysts, and cracking-initiating additives. Subsequently, the potential challenges of each approach in practical applications are analyzed. Furthermore, based on the current research findings, we outline future research directions with the expectation of facilitating the advancement of efficient cracking technologies for endothermic hydrocarbons. Full article

High-altitude and high-speed aircraft generate substantial aerodynamic heat during flight, creating a harsh thermal environment in the engine compartment that risks overheating and burnout of control components and fuel and lubricating oil accessories. Consequently, the thermal protection system (TPS) design for engine accessories has become one of the key technologies in hypersonic vehicle design. Based on certain TBCC, this paper uses a modular active-passive integrated TPS design and employs the quality management experimental design tool to optimize the design and decouple the method proposed on the modular design boundaries. This paper is the first to combine modular design with design of experiments (DOE) tools and apply them to the TPS of high-altitude and high-speed combined power accessories. The design scheme is optimized by identifying the main influencing factors. The optimized TPS scheme decreases the performance loss by 10% and increases cooling efficiency by 22–26%. The proposed engineering method shortens the development cycle significantly and improves efficiency by 78%. The modular design method for accessory TPS provided in this paper has good engineering applicability and can be widely used in the early stages of thermal protection scheme design, scheme optimization, scheme selection, and overall thermal management of hypersonic combined power systems. Full article

Trajectory optimization of hypersonic vehicles face challenges from complex aerodynamic environments and multiple constraints, where traditional offline optimization methods struggle to meet real-time requirements. This study proposes a novel online trajectory optimization framework for hypersonic vehicles that integrates a multi-strategy improved whale optimization algorithm (MWOA) with an attention-mechanism Long Short-Term Memory (AM-LSTM) network. First, an offline trajectory dataset under aerodynamic uncertainties is generated using sequential second-order cone programming (SOCP). Subsequently, a multi-head attention mechanism is incorporated into the LSTM network to effectively capture sequential dependencies within the trajectory data. To automate the hyperparameter tuning of the AM-LSTM architecture, a multi-strategy improved whale optimization algorithm is developed, which incorporates circle chaotic mapping for population initialization, a nonlinear convergence factor to balance global and local search, and a dynamic golden-sine mutation strategy to enhance optimization robustness. The trained MWOA-AM-LSTM hybrid model is then employed for real-time trajectory generation. Numerical simulation results demonstrate that the proposed framework achieves superior terminal accuracy under aerodynamic perturbations, validating its effectiveness and robustness for hypersonic vehicle reentry trajectory optimization. Full article

Re-entry flights of reusable first or upper stages typically foresee phases in the hypersonic flight regime, characterized by severe aero-thermal loads which could become critical for the most exposed components, like the vehicle forebody or the fin leading edges. These require consequently dedicated thermal protection systems (TPS), whose design generally requires a multi-disciplinary approach. In this framework, a viable solution is the use of high-temperature resistant ceramic matrix composite (CMC) structures, but the implementation of such technology, especially for the manufacturing of complex components and its application in real flight conditions, still presents significant challenges. In this work, the design activities for the CMC-based TPS of the payload forebody of a hypersonic sounding rocket are presented, developed within the framework of the STORT project, whose mission includes in flight demonstration of multiple critical technologies required for sustained flight at Mach numbers above 8, corresponding to a significantly high integral thermal load. Full article

With the rapid development of aerospace technology towards hypersonic vehicles, the synergistic demand for lightweighting and high-efficiency thermal insulation performance of ablation-resistant thermal insulation materials is becoming increasingly urgent. In this study, nanoporous phenolic resin was used as the matrix to prepare quartz fiber-reinforced phenolic aerogel composites (QF/PF), mullite fiber-reinforced phenolic aerogel composites (MF/PF), and carbon fiber-reinforced phenolic aerogel composites (CF/PF), and the influence mechanisms of different reinforcing fibers on the properties of the composites were systematically investigated. QF/PF exhibits optimal thermal insulation performance with a thermal conductivity of 0.1 W/(m·K) at 20–200 °C, followed by MF/PF with a thermal conductivity of 0.11 W/(m·K). Relatively weak thermal insulation performance is demonstrated in CF/PF, whose thermal conductivity reaches 0.14 W/(m·K). However, in terms of mechanical properties, CF/PF is outstanding, with a tensile strength of 54.62 MPa and a bending strength of 29.69 MPa. In addition, the most excellent ablation resistance is displayed in CF/PF, with a linear ablation rate of 0.13 mm/s and a mass ablation rate of 0.0435 g/s, which are significantly lower than QF/PF and MF/PF. This study provides an important basis for the selection of reinforcing fibers in different application scenarios. QF/PF or MF/PF is preferred for high thermal insulation requirements. CF/PF is favored for high load-bearing requirements or extreme ablative environments. Full article

This article proposes a novel predefined-time sliding mode fault-tolerant control method for the attitude tracking of hypersonic vehicles subject to actuator failures and external disturbance. A novel sufficient condition of the Lyapunov function ensuring predefined-time stability and practical predefined-time stability is established, which serves as the theoretical basis for the controller design. In contrast to existing Lyapunov conditions, this formulation provides greater design flexibility. Based on this theoretical foundation and an extended state observer, a predefined-time sliding mode controller is developed. The controller ensures system robustness while enabling an accurate estimate of the settling time upper bound, which is independent of initial conditions. Furthermore, the actual settling time can be tuned via the preset parameters. Finally, the proposed controller is evaluated on a hypersonic vehicle model subject to actuator bias, loss of effectiveness faults, and external disturbance. Numerical simulations demonstrate that the proposed method exhibits superior performance, including faster convergence, lower tracking errors, and enhanced robustness and fault tolerance, compared to an existing predefined-time sliding mode control approach. Full article

Hypersonic vehicles impose stringent requirements on lightweight structures to maintain mechanical integrity under extreme thermal environments. Bismaleimide (BMI)-based carbon fiber-reinforced polymer (CFRP) composites, featuring a high glass transition temperature and excellent thermal stability, are regarded as promising candidates for such applications. However, the high curing temperature and narrow processing window of BMI resins make it challenging to manufacture stiffened-shell structures with low defect levels and high fiber volume fractions. In this study, an integrated manufacturing route—hot-melt prepregging–filament winding–matched-metal mold forming—is proposed, and the key processing parameters are optimized via single-factor experiments and the Box–Behnken response surface methodology. The tensile strength of the laminate is selected as the response variable to evaluate the effects of the compression displacement (A), thermal consolidation/bonding temperature (B), heating rate (C), and cooling rate (D). The results reveal a unimodal dependence of the tensile strength on each parameter, with the significance ranking B > D > A > C; moreover, the A–B and A–D interactions are significant (p < 0.01). The established quadratic regression model exhibits good agreement with experimental data (R² = 0.974; R²_adj = 0.949). The predicted optimum conditions are A = 0.07 mm, B = 114.93 °C, C = 1.35 °C·min⁻¹, and D = 4.58 °C·min⁻¹, corresponding to a predicted tensile strength of approximately 2287 MPa. Validation experiments yielded 2291 MPa, in excellent agreement with the prediction. Microstructural observations indicate tight interlaminar bonding and a pronounced reduction in voids under the optimized conditions. Applying the optimized process to fabricate stiffened-shell demonstrators achieves a fiber volume fraction of >60% and a void content of <1%. This work provides a quantitatively defined processing window and parameter optimization basis for the high-quality manufacturing of BMI-CFRP stiffened-shell structures, with significant engineering relevance. Full article

This paper presents a comprehensive study on the control law design for the turbine-to-ramjet mode transition in an adaptive-cycle turbine-based combined cycle (TBCC) engine, aiming to mitigate the persistent “thrust gap” challenge. An integrated conceptual configuration of a hypersonic vehicle with a parallel-duct TBCC system, which replaces the conventional turbofan with a three-bypass adaptive cycle engine (ACE), is proposed. High-fidelity performance models for both the ACE and the scramjet are developed, with a Kriging surrogate model employed to accelerate the computationally intensive ACE simulations during the transition. A co-optimization framework is established, defining a comprehensive performance index that balances thrust tracking accuracy and control smoothness under rigorous intake-engine flow matching constraints. Using sequential quadratic programming (SQP), the control schedules for the ACE’s variable geometries are optimized. Comparative analyses reveal that the ACE, with its flexible bypass management and multiple adjustable mechanisms, can actively adapt its airflow demand to match the restricted intake supply. Consequently, the optimized ACE-based TBCC reduces total airflow fluctuation during the Mach 3–3.5 transition from 106% (conventional turbofan baseline) to 42.5%, while maintaining required thrust. This work quantitatively demonstrates the superior flow-handling capability of adaptive cycle technology, providing a viable and effective solution for ensuring stable and efficient mode transition in future hypersonic TBCC propulsion systems. Full article

With the development of aerospace technology, hypersonic flight vehicles are evolving towards larger size, lighter weight, and higher performance. Their cross-domain maneuverability and extreme flight environment led to the rigid–flexible coupling effect and became the core bottleneck restricting performance improvement, seriously affecting flight stability and control accuracy. This paper systematically reviews the research status in the field of control for high-speed rigid–flexible coupling aircraft and conducts a review focusing on two core aspects: dynamic modeling and control strategies. In terms of modeling, the modeling framework based on the average shafting, the nondeformed aircraft fixed-coordinate system, and the transient coordinate system is summarized. In addition, the dedicated modeling methods for key issues, such as elastic mode coupling and liquid sloshing in the fuel tank, are also presented. The research progress and challenges of multi-physical field (thermal–structure–control, fluid–structure–control) coupling modeling are analyzed. In terms of control strategies, the development and application of linear control, nonlinear control (robust control, sliding mode variable structure control), and intelligent control (model predictive control, neural network control, prescribed performance control) are elaborated. Meanwhile, it is pointed out that the current research has limitations, such as insufficient characterization of multi-physical field coupling, neglect of the closed-loop coupling characteristics of elastic vibration, and lack of adaptability to special working conditions. Finally, the relevant research directions are prospected according to the priority of “near-term engineering requirements–long-term frontier exploration”, providing Refs. for the breakthrough of the rigid–flexible coupling control technology of the new-generation high-speed aircraft. Full article

In aerospace, defense, and energy systems, ceramic matrix composites (CMCs) are smart structural materials designed to function continuously in harsh mechanical, thermal, and oxidative conditions. Using high-strength fiber reinforcements and tailored interphases that enable damage-tolerant behavior, their creation tackles the intrinsic brittleness and low fracture toughness of monolithic ceramics. With a focus on chemical vapor infiltration, polymer infiltration and pyrolysis, melt infiltration, and additive manufacturing, this paper critically analyzes current developments in microstructural design, processing technologies, and interfacial engineering. Toughening mechanisms are examined in connection to multiscale mechanical responses, including controlled debonding, fiber bridging, fracture deflection, and energy dissipation pathways. Cutting-edge environmental barrier coatings are assessed alongside environmental durability issues like oxidation, volatilization, and hot corrosion. High-performance braking, nuclear systems, hypersonic vehicles, and turbine propulsion are evaluated as emerging uses. Future directions emphasize self-healing systems, ultra-high-temperature design, and environmentally friendly production methods. Full article

Normal shock pressure ratios in equilibrium air for Mach numbers up to 30 and altitudes to 300,000 feet are shown to be correlated by a simple power law which provides an accuracy of ±2%, thereby permitting direct calculation of corresponding enthalpy ratios accurate to ±1% without iteration; a slight change in power-law coefficients extends this capability to Mach 65. Temperature, density, and compressibility may be then found directly from tables for high temperature air. For Mach numbers up to at least 6, a linear approximation for specific heat provides direct solutions for post-shock state variables, while a complementary logarithmic model of the equation of state enables direct solutions for Mach numbers up to about 12. This approach, which provides accuracy within ±3% for all relevant variables in the practical flight corridor of vehicles at these low to moderate hypersonic Mach numbers, should prove useful in design and analysis because the algebraic solutions obtained need neither iteration or interpolation. Full article

Experiments on hypersonic boundary-layer instability of a fin–cone configuration were conducted in a Φ 0.5 m Mach 6 Ludwieg tube tunnel. Infrared thermography and high-frequency pressure sensors were used to measure the transition front and instability waves under four different nose bluntness conditions. On the leeward surface, transition is delayed near the centerline due to expansion waves generated by the double-cone structure. The region close to the corner is strongly influenced by the horseshoe vortex, whereas instability waves around 110 kHz manifest as the flow moves away from it. In contrast, transition on the windward surface occurs earlier and broadband high-frequency instability waves of 160–300 kHz are present near the corner. Increasing nose bluntness strongly suppresses transition away from the fin root, especially near the centerline and on the fin-off cone side, but has a relatively limited impact on the shock-interaction regions near the fin–cone corner. Transition on the fin surface remains insensitive to nose bluntness variations. This work elucidates the distinct transition behaviors across different regions of a complex fin–cone configuration and their differential responses to nose bluntness, providing valuable insights for the aerodynamic design and transition prediction of hypersonic vehicles. Full article

The atmospheric reentry of hypersonic vehicles generates a plasma sheath enveloping the vehicle surface. This fluid medium moves at velocities distinct from the vehicle body, significantly altering its electromagnetic scattering properties. This paper introduces a Multi-Frame Lorentz Transformation Finite-Difference Time-Domain (FDTD) method, which incorporates a spatially varying velocity field into the computational scheme. The proposed algorithm maintains velocity synchronization in electromagnetic field updates and employs a near-to-far-field transformation for far-zone analysis. We systematically investigate the scattering characteristics of a plasma-sheath-covered hypersonic vehicle across a range of velocities and analyze the effect of velocity on the Radar Cross-Section (RCS) under different polarization conditions. Full article

The problem of shock wave/boundary layer interaction induced by compression corners widely exists in the external and internal flows of various supersonic/hypersonic aircraft. In practical engineering applications, multistage continuous compression is often used in the fin/rudder structure, while in internal flow, multistage compression schemes are usually employed at the inlet to enhance total pressure recovery; therefore, it is necessary to investigate the characteristics of multistage compression corner shockwave/boundary layer interactions. In basic research, it is usually simplified as the double compression corner shockwave/boundary layer interaction issue. In this paper, an experimental study of hypersonic shock/boundary layer interaction characteristics is conducted under quiet and noise inflow conditions, respectively, for the double compression corner model. Using high-speed Schlieren, the typical structure of shockwave/shockwave interaction and shockwave/boundary layer interaction above the corner is explored under both quiet and noisy incoming flow conditions. Then, based on gray average, root-mean-square analysis, Fast Fourier transform, proper orthogonal decomposition, and dynamic mode decomposition methods, the time-average and unsteady characteristics of the double compression corner configuration-induced separation were studied, and a comparative analysis was conducted. The difference law between wind tunnel noise level and interaction characteristics was summarized. Finally, the characteristic length and spectral characteristics of unstable waves that dominated the stability of the plate boundary layer were studied. The formation mechanism of separation is discussed, which provides technical support for the internal and external aerodynamic design and targeted optimization of hypersonic vehicles. Full article