Hypersonic Vehicle Research Articles

Parameterized evasion strategy for hypersonic glide vehicles against two missiles based on reinforcement learning

In practical combat scenarios, Hypersonic Glide Vehicles (HGV) face the challenge of evading Successive Pursuers from the Same Direction while satisfying the Homing Constraint (SPSDHC). To address this problem, this paper proposes a parameterized evasion guidance algorithm based on reinforcement learning. The three-player optimal evasion strategy is firstly analyzed and approximated by parametrization. The switching acceleration command of HGV optimal evasion strategy considering the upper limit of missile acceleration command is analyzed based on the optimal control theory. The terminal miss of HGV in the case of evading two missiles is analyzed, which means that the three-player optimal evasion strategy is a linear combination of two one-to-one strategies. Then, a velocity control algorithm is proposed to increase the terminal miss by actively controlling the flight speed of the HGV based on the parametrized evasion strategy. The reinforcement learning method is used to implement the strategy in real time and a reward function is designed by deducing homing strategy for the HGV to approach the target, which ensures that the HGV satisfies the homing constraint. Experimental results demonstrate the feasibility and robustness of the proposed parameterized evasion strategy, which enables the HGV to generate maximum terminal miss and satisfy homing constraint when facing single or double missiles.

Robust control for hypersonic flight vehicle overload tracking under dynamics uncertainties

Robust control for hypersonic flight vehicle overload tracking under dynamics uncertainties

Backstepping control of hypersonic vehicles under input and output constraints with model uncertainties and disturbances

In this paper, considering the physical restriction of hypersonic vehicle systems in a practical flight environment, the altitude tracking problem is studied with input magnitude, input rate, output constraints, system parameter uncertainties and disturbances, which expands the traditional considerations of control methods in the hypersonic vehicle field. The hyperbolic tangent function is employed to address the system input constraints. Furthermore, the incorporation of barrier Lyapunov function serves to ensure that the system output is limited in the prescribed limitations. In particular, two extended state observers are integrated to eliminate errors from model uncertainties and disturbances. Based on the effective combination of these techniques and auxiliary variable designs, a novel backstepping controller is proposed to simultaneously handle problems of input and output constraints, model uncertainties and disturbances. The closed-loop system stability is demonstrated using the Lyapunov theory. Simulation results show the effectiveness and superiority of the proposed controller compared with the traditional backstepping controller.

Enhanced Trajectory Forecasting for Hypersonic Glide Vehicle via Physics-Embedded Neural ODE

Forecasting hypersonic glide vehicle (HGV) trajectories accurately is crucial for defense, but traditional methods face challenges due to the scarce real-world data and the intricate dynamics of these vehicles. Data-driven approaches based on deep learning, while having emerged in recent years, often exhibit limitations in predictive accuracy and long-term forecasting. Whereas, physics-informed neural networks (PINNs) offer a solution by incorporating physical laws, but they treat these laws as constraints rather than fully integrating them into the learning process. This paper presents PhysNODE, a novel physics-embedded neural ODE model for the precise forecasting of HGV trajectories, which directly integrates the equations of HGV motion into a neural ODE. PhysNODE leverages a neural network to estimate the hidden aerodynamic parameters within these equations. These parameters are then combined with observable physical quantities to form a derivative function, which is fed into an ODE solver to predict the future trajectory. Comprehensive experiments using simulated datasets of HGV trajectories demonstrate that PhysNODE outperforms the state-of-the-art data-driven and physics-informed methods, particularly when training data is limited. The results highlight the benefit of embedding the physics of the HGV motion into the neural ODE for improved accuracy and stability in trajectory predicting.

Invited Article: The oxidation kinetics and mechanisms observed during ultra-high temperature oxidation of (HfZrTiTaNb)C and (HfZrTiTaNb)B2

Ultra-high temperature ceramics (UHTCs), most notably transition metal carbides and borides, exhibit melting temperatures exceeding 3000 °C, making them appropriate candidates to withstand the extreme temperatures (∼2000 °C) expected to occur at the leading edges of hypersonic vehicles. However, their propensity to react rapidly with oxygen limits their sustained application. The high entropy paradigm enables the exploration of novel UHTC compositions that may improve on the oxidation resistance of conventional refractory mono-carbides and -diborides. The oxidation kinetics of candidate high entropy group IV + V (HfZrTiTaNb)C and (HfZrTiTaNb)B2 materials were evaluated at 1500–1800 °C using Joule heating in one atmosphere 0.1%–1% oxygen/argon gas mixtures for times up to 15 min. Possible mechanisms based on the resulting complex time, temperature, and oxygen partial pressure dependencies are discussed. The carbides formed porous and intergranular oxides. Oxidation resistance was improved upon a continuous external scale formation. The diborides formed dense external scales and exhibited better oxidation resistance compared to the carbides. This improvement was attributed to the formation of liquid boria. Both compositions showed an unexpected reduction in material consumption at 1800 °C for all times tested, compared to results at lower temperatures. An in-depth analysis of the composition and morphology of the oxide scale and sub-surface regions for specimens tested at 1800 °C revealed that the formation of denser group IV-rich (Hf, Zr, Ti) oxides mitigated the formation of the otherwise detrimental liquid-forming group V (Ta, Nb) oxides, leading to the improved oxidation resistance.

Reinforcement Learning Control of Hypersonic Vehicles and Performance Evaluations

This work presents a new framework for model-based continuous-time reinforcement learning (CT-RL) control of hypersonic vehicles (HSVs). The predominant classes of CT-RL methods for general nonlinear systems in adaptive dynamic programming (ADP) and deep RL tend to either present substantial theoretical results but lack practical synthesis capability (ADP) or show empirical promise without offering theoretical guarantees (deep RL). Meanwhile, RL control frameworks developed directly for HSVs tend to require a simplified model and complicated control structure, and they lack the substantial numerical evaluations essential for real-world flight implementation. To directly address these challenges, we propose a new decentralized excitable integral reinforcement learning framework within which the reference input-based exploration improves persistence of excitation. Together with new insights on prescaling and established decentralized control structure for HSVs, we demonstrate the resulting controller for significant performance improvement over classical Linear Quadratic Regulator (LQR) and feedback linearization methods. Additionally, we provide convergence, optimality, and closed-loop stability guarantees of the proposed method. We demonstrate these performance guarantees over a set of substantial and systematic numerical evaluations on an unstable, nonminimum phase HSV model subject to varying modeling errors and initial conditions.

Preparation, mechanical properties and anti-oxidation behavior of lightweight porosity-controlled SiC(rGO, xZrB2) composite PDCs for thermal protection

Achieving well-balanced light weight with simultaneous improvement in mechanical and antioxidant properties of SiC-based composite polymer-derived ceramics (PDCs) for hypersonic vehicle components is still a huge challenge. Herein, lightweight SiC(rGO, xZrB2) composite PDCs were prepared via re-pyrolyzing ball-milling-induced ZrB2-SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene (PCS-VTES-GO, PVG) blends. Main reinforcements consist of ZrB2, ZrO2(ZrC), ZrOSi and SiO2/β-SiC phases, among which favorable compatibility enables enhanced bear loading performances and high-temperature oxidation resistance. Rigid SiC(rGO)p tightly links with flexible PVG pyrolysis products, and co-assembles into robust SiOxCy/Cfree(rGO) matrix in framework owing to plentiful Si-dangling bonds at their interfaces. More interestingly, interfacial ZrOSi/ZrC transition zone can augment structural disorder of ceramic network, give bridging effects, strengthen interfacial compatibility, and even hinder further crack propagation for self-densification. Particularly, SiC(rGO, 30%ZrB2) composite PDCs possess optimal hardness (6.49 GPa) and outstanding fracture toughness (5.77 MPa⋅m1/2). Porous SiC(rGO, 30%ZrB2) composite PDCs own stable structure integrity within 60-min testing under butane torch flame at 1300 °C. Self-healing protective SiO2-ZrO2 glass layer avoids destructive structure and timely covers defects, thus retains good mechanical performances. Such good synergistic reinforcement and multiscale design of porosity-controlled composite, realizes integration of lightweight/good load-bearing characteristics with improved oxidation resistance for thermal protection system (TPS) of hypersonic vehicles.

Predictor-corrector reentry guidance for hypersonic glide vehicles based on high-precision analytical solutions

To address the challenge of improving downrange prediction accuracy while reducing unnecessary bank reversals, we propose a predictor-corrector guidance method based on high-precision analytical solutions. First, precise analytical solutions for downrange and crossrange are derived to establish the foundation for the guidance law, and we use a neural network model for accurate flight-path angle prediction. Next, we compensate for Earth's rotation effects in the downrange prediction by employing the Taylor expansion. Aiming to eliminate phugoid oscillations, we add the flight-path angle feedback into the command of the bank angle and angle of attack. Subsequently, a lateral guidance law that combines the heading angle error corridor with predicting bank reversals is introduced. The sign of the bank angle is determined by the corridor during the initial flight phase. Following the vehicle travels a specified downrange distance, we use the crossrange analytical solution to regulate subsequent bank reversals. Simulations under disturbance conditions demonstrate that the proposed guidance method has high accuracy and strong robustness, effectively meeting various constraints.

Mechanism of active flow control using a novel spike aerodome-channel concept in the hypersonic flow: A numerical study

Among the design requirements of hypersonic vehicles, reducing aerodynamic heating and drag force simultaneously is the main challenge. This paper proposes a novel spike aerodome-channel combination concept to realize the flow field reconstruction around the hypersonic blunt body. The novel configuration is investigated in the axisymmetric flow at a Mach number of 6 at zero angle of attack. The two-dimensional Reynold-averaged Navier–Stokes equations are numerically solved, and the shear-stress transport k–ω model is the turbulence model implemented in this study. Parameters such as spike length and lateral jet location are investigated to explore the drag and heat reduction performance and the flow control features. The obtained results show that the application of the novel spike aerodome-channel concept alters the flow field by eliminating or replacing the strong bow shock wave, and the design of hypersonic vehicles can benefit from the application of the proposed concept. The blunt body coupled with a frustum of cone-tipped spike-channel configuration provides a remarkable drag reduction effect of 20.71% with respect to the case without channel. Considering the effect of lateral jet location, the drag reduction performance of the case with LR = 0.75 is superior to that of the root jet case at the same spike length, and a considerable drag reduction of 28.93% is obtained with L/D = 2.4. In addition, longer spike length is beneficial for improving drag reduction performance, while excellent efficiency of heat protection is obtained in a certain spike length range. For the case of L/D = 1.6 with root jet, the peak Stanton number is significantly decreased by 33.51%.

Improved Design Method for Hypersonic Intakes Using Pressure-Corrected Osculating Axisymmetric Flows Method

The efficient design of air intake is crucial for high-speed airbreathing propulsion systems. This paper presents a novel design method that integrates the recently introduced internal conical flow M (ICFM) basic flowfield (Musa et al., “New Parent Flowfield for Streamline-Traced Intakes,” AIAA Journal, Vol. 61, No. 7, 2023, pp. 2906–2921) with the pressure-corrected osculating axisymmetric flows and streamline tracing techniques. The new design method takes into account the effects of lateral pressure gradients by incorporating pressure corrections into the original design method using crossflow velocity information from the ICFM flowfield. Additionally, new entrance and throat profiles are introduced for designing two hypersonic internal waverider intakes with shape transition. One intake is designed using the new method, and the other using the original method. Viscous simulations have been performed at design (i.e., Mach 6.0) and off-design (i.e., Mach 4.0 and 3.5) conditions. The results indicate that the pressure-corrected intake exhibits superior performance in terms of total pressure recovery and reduced flow distortion. This reveals that the new design method can achieve a smooth shape and efficient aerodynamic transitions between the intake entrance and throat. The new entrance and throat profiles realized better performance than the typical ones. The startability analysis reveals that the Van Wie curve controls the considered intakes. Thus, combining the pressure-corrected osculating axisymmetric flows with the ICFM flowfield enhances the performance of hypersonic intakes, making this approach a promising avenue for future hypersonic vehicles.

Adaptive Cooperative Game Penetration Guidance for Multiple Hypersonic Vehicles With Performance Constraints

Adaptive Cooperative Game Penetration Guidance for Multiple Hypersonic Vehicles With Performance Constraints

Numerical investigation on the performance of combinational spike and transpiration cooling concept for nose cone under hypersonic conditions

Abstract Aiming at solving the thermal protection problems of the nose cone for hypersonic vehicles, a novel combinational spike and transpiration cooling concept is proposed in this paper. Although the temperature of the nose cone structure can be effectively reduced by traditional transpiration cooling, the cooling effect is not ideal due to the extremely high heat flux and pressure near the stagnation point. In the combinational configuration, the bow shock wave at the leading edge of the nose cone is pushed away by the spike, so that the pressure and heat flux along the nose cone surface are reduced obviously, and the cooling effect is also improved significantly. The flow field generated by this innovative concept has been thoroughly examined through numerical simulations employing the compressible Reynolds-Averaged Navier-Stokes (RANS) equations in conjunction with the shear stress transport (SST) k-ω turbulence model. The fluid-thermal interaction is considered by using the conjugate heat transfer approach. The performance of three configurations based on the nose cone are numerically investigated, including transpiration cooling, spike, combinational spike and transpiration cooling. The numerical results show that, compared with the traditional transpiration cooling, the temperature at the stagnation point of the nose cone for the combinational configuration is reduced by about 64%, which proves the feasibility and high efficiency of the novel combinational concept. With the increase of coolant mass flow, the temperature along the nose cone surface for combinational configuration decreases, while the magnitude of the temperature reduction decreases. Therefore, under certain incoming flow conditions, the appropriate coolant mass flow should be considered to achieve better thermal protection effect.

Coupling study of onboard power generation system of Magnetohydrodynamics enhanced Brayton Cycle

Closed cycle power generation systems offer a possible solution to meet the high electricity needs of hypersonic vehicles, but the power generation is limited by the finite cold source and cycle temperature. Introducing two-phase flow liquid metal (LM) MHD power generation based on Closed-Brayton-Cycle (CBC) is a potential solution that can enhance the thermal-electricity conversion process at the system level. However, it is difficult to reflect the complex coupling relationship between the power generation system and the vehicles propulsion system and the limitations of finite cold sources by relying only on ideal system analysis, especially the contradiction between the void fraction and the mass flow of working fluid after the introduction of LMMHD power generation. The study utilizes a multi-dimensional model to evaluate the performance of the CBC enhanced by multi-stage LMMHD generators coupled with hydrocarbon fuel scramjet. The multi-stage mixing-separation LMMHD generator is proposed to decouple the void fraction of the MHD channel and the wall cooling process, and control the void fraction by change number of stages. The calculation result indicate that the void fraction significantly affects the overall power generation performance, including output power, performance boundary, etc. Increasing the void fraction is beneficial, and the optimal void fraction is 0.65. At the same Mach number, the fuel cooling capacity available to the system increases with the fuel equivalence ratio, resulting in higher total power output. The maximum Mach number for thermal protection of the combustor walls alone may surpass 9.5. For gas void fractions of 0.35/0.5/0.65, the maximum power generation reaches 182.8/167.1/156.9 kW, respectively. The novel system is compared with other advanced thermal-electricity conversion cycles under nearly the same conditions and demonstrated clear performance advantages.

Investigating Intra-Pulse Doppler Frequency Coupled in the Radar Echo Signal of a Plasma Sheath-Enveloped Target

In detecting hypersonic vehicles, the radar echo signal is coupled with an intra-pulse Doppler frequency (I-D frequency) component caused by relative motion of a plasma sheath (PSh) and the vehicle, which can induce the phenomenon of a ghost target in a one-dimensional range profile. In order to investigate the I-D frequency generated by the relative motion of a PSh, this study transforms a linear frequency modulated (LFM) signal into a single carrier frequency signal based on echo signal equivalent time delay-dechirp processing and realizes high resolution and fast extraction of the I-D frequency coupled with the frequency-domain echo signal. Furthermore, by relying on the computation of the surface flow field of the RAMC-II Blunt Cone Reentry Vehicle, the coupled I-D frequency in the radar echo signal of a PSh-enveloped target under circumstances of typical altitudes and carrier frequencies is extracted and further investigated, revealing the variation law of I-D frequency. The key findings of this study provide a novel approach for suppressing anomalies in radar detection of PSh-enveloped targets as well as effective detecting and as robust target tracking.

Correction of Aero-Optical Effect with Blow–Suction Control for Hypersonic Vehicles

High-speed turbulence induces significant aero-optical effects that severely disrupt the functionality of imaging systems of hypersonic vehicles. In this study, the aero-optical correction of various jet cooling modes is investigated using a Terminal High Altitude Area Defense (THAAD)-like seeker model and the imaging impact of high-speed flow field and flow control on the optical window is analyzed by the Delayed Detached Eddy Simulation (DDES) method. The findings reveal that a jet mode parallel to the window exhibits better cooling effectiveness compared to a perpendicular jet mode along the body axis; however, it introduces additional wavefront distortion, leading to degraded imaging quality. Although micro-vortex generators (MVGs) can reduce density fluctuations near the window from a refractive index perspective, they do not effectively mitigate wavefront distortion or improve window cooling efficiency. Finally, incorporating suction control, a comprehensive flow control solution, significantly improves the flow field structure near the window, resulting in a more uniform temperature distribution and reduced wavefront distortion. Applying this flow control method results in a 14.7% reduction in wavefront distortion at 3 Ma and an approximately 20% maximum value reduction at 5 Ma. This study proposes a novel and comprehensive flow control method to effectively mitigate the aero-optical effect in hypersonic flows, providing a new avenue for subsequent researchers in this field.

Flow-thermal coupled investigation on hypersonic spike-jet with channel

As for blunt-body hypersonic vehicles, the extreme drag and aero-heating pose great challenges to the conceptual design. Different from the conventional configurations, a blunt body slotted with a channel is proposed in this paper. The channel is further combined with a jet on the shoulder to reduce drag and aero-heating. Simultaneously, based on the position of the separation point and vortex edge, a modified effective body approach is developed to accurately investigate the drag reduction mechanism. Specifically, the more slender the modified effective body is, the more obvious the drag reduction is. The simulation results show that the spike-channel-jet can push the shear layer on the spike away from the wall. In this way, the position of shear reattachment point moves downstream, which can enlarge the recirculation zone and weaken the shock-shock interaction. Additionally, the reattachment shock is pushed far away from the blunt body, which is also weakened. For drag, net power is introduced to evaluate the practical value of spike-channel-jet for drag reduction. Compared with a simple spike (spike length L/D = 1) of the same size, the spike-channel-jet can reduce the total drag by 24.68 %, the peak pressure coefficient of the blunt body by 38.54 %, the peak temperature of the blunt body by 65.75 %, and the peak temperature of the spike by 10.63 %. The maximum net power can reach 13.30 kW. Considering the fluid-thermal interaction, the findings reveal the influence of the spike length and jet mass flow rate on aerodynamic performance, by modified effective body further analyze the drag reduction mechanism with the jet, and validate the different reasons for the peak temperature and pressure of the blunt body.

High temperature heat flux sensor with ITO/In2O3 thermopile for extreme environment sensing

Hypersonic vehicles and aircraft engine blades face complex and harsh environments such as high heat flow density and high temperature, and they are generally narrow curved spaces, making it impossible to actually install them for testing. Thin-film heat flux sensors (HFSs) have the advantages of small size, fast response, and in-situ fabrication, but they are prone to reach thermal equilibrium and thus fail during testing. In our manuscript, an ITO–In2O3 thick film heat flux sensor (HFS) is designed, and a high-temperature heat flux test system is built to simulate the working condition of a blade subjected to heat flow impact. The simulation and test results show that the test performance of the thick-film HFS is improved by optimizing the structure and parameters. Under the condition of no water cooling, the designed HFS can realize short-time heat flux monitoring at 1450 °C and long-term stable monitoring at 1300 °C and below. With a maximum output thermopotential of 17.8 mV and an average test sensitivity of 0.035 mV/(kW/m2), the designed HFS has superior high-temperature resistance that cannot be achieved by other existing thin (thick) film HFSs. Therefore, the designed HFS has great potential for application in harsh environments such as aerospace, weaponry, and industrial metallurgy.

Experimental Study on Convection Heat Transfer of CO2 in C/SiC Composite Porous Material at Subcritical, Transcritical, and Supercritical States

Using C/SiC as the structure for transpiration cooling is prospective for new hypersonic vehicles, based on clarification of heat transfer process in porous media. But there are still gaps due to the complexity of pore structure of C/SiC, together with the effects of capillary force and strong variation of thermophysical properties for subcritical and supercritical flow. In this study, heat transfer analysis for C/SiC with CO2 as the coolant is presented by experiments. Heat transfer characteristics in typical C/SiC sample under various mass flow rates (0.003–0.018 kg/s), inlet fluid temperatures (20–40 °C) and pressures (5.9–10 MPa) are analyzed. Heat transfer and pressure drop correlations have been developed. The results show heat transfer coefficient at supercritical state behaves non-monotonic under varying flow rates caused by the combined effect of sharp increase of specific heat and the change of flow rate. The effect of pressure on heat transfer can be neglected compared to that of flow rate, while for Reynolds number (Re) >100, the pressure drop of supercritical cases are smaller than that of phase-change cases under similar Re, due to the effect of capillary force in C/SiC. This study can provide basic support for further study of transpiration cooling using C/SiC and CO2.

Tunable Ptδ+/Pt0 sites by highly dispersed defected TiO2 for efficient catalytic methylcyclohexane dehydrogenation

Dehydrogenation reaction occurs for the hydrogen release process of liquid organic hydrogen carriers (LOHCs), the regenerative cooling of advanced aircraft, etc. But the synergistic effects of Pt active sites are still ambiguous. Herein, a series of Pt-based catalysts with tunable Pt0-Ptδ+ sites were fabricated by changing the ratio of highly dispersed defected TiO2 on MCM-41 (M41) for efficient dehydrogenation of methylcyclohexane (MCH). The characterizations indicate TiO2 nanoparticles (NPs) are highly dispersed on M41 support, and possess abundant Ti3+/oxygen vacancies. The increase of TiO2 loading amount can enhance the interaction between Pt NPs and TiO2, which increases Ptδ+/Pt0 ratio gradually. The dehydrogenation test and theoretical results confirm that the synergistic effect of Pt0 and Ptδ+ sites contributes the optimal dehydrogenation performance, in which Pt0 promotes the consecutive C–H bond cleavage and Ptδ+ significantly decreases the desorption energy barrier for H2 and toluene (TOL). Specifically, the MCH conversion (when applied for LOHCs) is ca. 88 % and the selectivity of TOL is over 99.5 % under 1.0Pt/0.5TiO2/M41, while the high MCH conversion of 90 % and TOL selectivity of more than 86 % are achieved under 1.0Pt/1.0TiO2/M41 (as regenerative cooling for hypersonic vehicle). This work provides the approach of modulating the synergistic active sites to obtain high-performance dehydrogenation catalyst.

Multiobjective optimization of transpiration cooling in hypersonic laminar flow using a genetic algorithm approach

The efficient utilization of transpiration cooling is crucial for addressing coolant consumption challenges in hypersonic vehicle design. This study focuses on optimizing the blowing ratio, a key parameter in transpiration cooling. A multiobjective genetic algorithm is employed to determine the optimal blowing ratio using an experimental correlation. The optimization objectives include average thermal effectiveness, length of cooling with thermal effectiveness greater than 0.5, and coolant reservoir volume over a 60 s duration cooling process. The results reveal that a blowing ratio of 0.108 % is the optimal point, with corresponding values for average thermal effectiveness, coolant reservoir volume, and length of cooling being 0.493, 7.093 m³, and 0.14 m, respectively. A comparison with the maximum experimental blowing ratio indicates a 56.61 % reduction in average thermal effectiveness, accompanied by a 56.68 % decrease in coolant reservoir volume. This study highlights the application of multiobjective genetic algorithms in optimizing the transpiration cooling blowing ratio for hypersonic vehicles.