Hypersonic Reentry Vehicle Research Articles

Coordinated adaptive control of hypersonic reentry vehicle considering channel coupling

The paper proposes a coordinated adaptive control for the hypersonic reentry vehicle with channel coupling and system uncertainties. Using the hierarchical sliding mode scheme, the coordinated design is applied to ensure flight safety. Once the yawing moment is not enough to meet the control requirement, the system will coordinate the channel moment distribution, and furthermore, the flight attitude can be stabilized with yawing moment compensation. To obtain the high‐precision uncertain approximation, the online recorded data‐based prediction error is constructed as one learning performance index, which is introduced into the updated law. The uniformly ultimately boundedness of the system signals is guaranteed via the Lyapunov approach. Through the simulation test, the results show that the proposed approach can maintain a stable attitude and present the adaptation to the system uncertainty.

Mathematical Modeling and Associated Numerical Simulation of Fusion/Solidification Front Evolution in the Context of Severe Accident of Nuclear Power Engineering

Considering transient processes where liquid/solid phase change occurs, this paper focuses on the associated modeling and numerical treatment in the frame of “Computational Fluid Dynamics” simulations. While being of importance in many industrial applications involving solidification and melting of mixed materials, including power and manufacturing engineering, the first application of this work pertains to the analysis of severe accidents in a nuclear reactor. Indeed, in this context, the molten core materials (a.k.a. corium) can form a high-temperature multiphase liquid pool at the boundary of which fusion and solidification phenomena are of prime importance. In this context, even if materials at play are treated as pure components, it is mandatory to distinguish two different phase change temperatures with a solid fusion temperature and a liquid solidification temperature. Accordingly, in the frame of a sharp interface representation, the paper introduces non-classical heterogeneous conditions at the liquid/solid boundary in such a way that both moving interface (through Stefan conditions associated with fusion or solidification) and static interface (imposing heat flux continuity) are supported at the same time on different spatial locations along this boundary. Within a monolithic resolution of Navier–Stokes and heat conduction equations, this interface is explicitly tracked with combined Front-Tracking and VOF methods. In order to ensure zero velocity in the solid phase, an Immersed Boundary Method and a direct forcing penalization are also introduced. The main relevant features of this combination of numerical methods are discussed along with their implementation in the TrioCFD code taking advantage of the pre-existing code capabilities. Numerical simulations including both verification tests and a case of interest for our industrial application are reported and demonstrate the applicability of the proposed triptych model+methods+code to treat such problems. The numerical tools and the simulation code developed in this work could be used not only in the several accident context but also to simulate melting, solidification and fusion processes occurring in aerodynamics, hypersonic reentry vehicles and laser applications to cite but a few.

Sliding mode based fault-tolerant control of hypersonic reentry vehicle using composite learning

A sliding mode based fault-tolerant control method using neural learning is studied for hypersonic reentry vehicle (HRV) in this paper. Based on the non-singular second-order terminal sliding mode, the composite neural learning is adopted to deal with the system uncertainties caused by the additive faults. The main point is to construct the prediction error to evaluate the performance of intelligent approximation. Meanwhile, a disturbance observer is employed to estimate the unknown disturbance while the actuator multiplicative fault is compensated with an adaptive law. The simulation of HRV is conducted to verify the effectiveness of the proposed fault-tolerant control scheme.

Hierarchical fault-tolerant control for over-actuated hypersonic reentry vehicles

This paper proposes a performance-focused and deep learning-based hierarchical fault-tolerant control framework for over-actuated hypersonic reentry vehicles. The hierarchical fault tolerance mechanism refers to the fault tolerance that can be realized both in the control allocation and control layers. First, a long short-term memory neural network-based fault diagnosis unit is proposed to solve the difficult problem of diagnosing actuator fault information under multisource disturbances. Based on the diagnosed fault information, the robust least-squares control allocation method is deployed to distribute the desired control moment to the actuator and achieve fault tolerance in the control allocation layer. Then, combined with a fixed time extended state observer, an improved multiple-degree-of-freedom prescribed performance control method is used to compensate the lumped disturbances, including control allocation error, ensure the prescribed tracking performance, and realize fault tolerance in the control layer. Finally, the theoretical analysis proves the stability of the proposed hierarchical fault-tolerant control scheme, and the effectiveness is verified by numerical simulation.

Effect of Thermal Ablation at the Fluid-Solid Interface of a Hypersonic Reentry Vehicle in Rarefied Flow Regime

The present work aims to develop a coupled flow-thermal solver to study atmospheric reentry phenomenon in the rarefied regime. Conjugate thermal analysis is performed for a charring ablative material by coupling a direct simulation Monte Carlo flow solver with an in-house material thermal response solver at the fluid-solid interface. The coupling is achieved by exchanging and updating the interface properties (convective heat flux and wall temperature) between the two solvers in a loosely coupled manner at certain anchor points along the reentry trajectory. Iterative and non-iterative coupling techniques are studied in this work and discussed. The effect of introducing pyrolysis gas at the interface in a loosely coupled flow-thermal analysis is studied by applying a blowing correction function to the heat flux obtained using iterative method. The results show that the blowing gas has an appreciable effect in reducing the surface heat flux that can significantly impact the TPS design.

Hypersonic Re-entry Vehicle Fault-Tolerant Control Against Actuator Failure via Integral Sliding Mode

A fault-tolerant control (FTC) scheme is proposed based on integral sliding mode(ISM) for attitude control of hypersonic re-entry vehicle (HRV) under partial loss of actuator effectiveness. First, the inner/outer loop mathematical model of HRV in the present of actuator failure is given with specific analysis on torque. Then prescribed performance approach is introduced to the ISM controller design by error transformation. Specifically, the transformation error rather than tracking error is chosen as the sliding variable to establish the sliding mode surface and reaching law. As a result, the attitude tracking error of HRV is limited into the expected range. Meanwhile, the transient process and the steady state behavior are both considered. Considering that the unknown fault information of actuator can cause adverse effect on HRV, an extended state observer(ESO) is adopted to estimate the unknown actuator failure. Thus the observer result is served as compensation for the loss of the controlled system performance. Simulation results show that the proposed scheme can fulfil the tracking task with prescribed performance.

Processing of ZrB2- and HfB2-Based Ultra-High Temperature Ceramic Materials: A Review

Abstract ZrB2 and HfB2 are leading materials in the category of ultra-high temperature ceramics (UHTCs). UHTCs are a group of ceramic materials that can withstand ultra-high temperature (>2,000°C) in oxidizing conditions. Such a high temperature will be encountered by future hypersonic reentry vehicles. Future reentry vehicles will have sharp edges to improve aerodynamic performance. The sharp leading edges will cause higher surface temperature than that of the actual blunt-edged vehicles. The sharp edges have less surface area to dissipate heat and thus the temperature gets increased. To withstand the intense heat generated when these vehicles reenter the earth’s upper atmosphere, UHTC materials are needed. UHTC materials are composed of borides of early transition metals. From the larger list of borides, ZrB2 and HfB2 have received the most attention as potential candidates for leading edge materials because their oxidation resistance is superior to that of other borides because of the stability of the ZrO2 and HfO2 scales that form on these materials at elevated temperatures in oxidizing environments. Processing of these materials is very difficult because these materials are very refractory in nature. Powder synthesis usually involves high-temperature solid state reactions. Dense bodies are generally produced by hot pressing and spark plasma sintering. For coating preparation, plasma spray, chemical vapor deposition, and physical vapor deposition is used. All these processing methods for ZrB2 and HfB2 are difficult because of the involvement of very high temperatures. In this review, the present state of the knowledge on processes employed for powder synthesis, fabrication of dense bodies, and coating processes is discussed. The advantages, limitations, and challenges in the different processing methods are addressed.

Quantized fixed-time fault-tolerant attitude control for hypersonic reentry vehicles

A quantized fixed-time fault-tolerant attitude control problem for hypersonic reentry vehicles is considered from the perspective of practical engineering. Taking into account the limited time available for recovery from a fault scenario, fixed-time extended state observers are used to simultaneously compensate for the negative effect of unknown time-varying actuator faults, uncertainties, and external disturbances. In contrast to the existing control schemes, which neglect the signal quantization transmission process and limited communication capacity, the hysteresis quantization mechanism is considered. Based on this, a fixed-time fault-tolerant control scheme is developed to ensure the fixed time convergence of all the tracking errors even in cases involving actuator faults. The stability and convergence are proven by performing a theoretical analysis. The simulation results validate the superiority and robustness of the proposed control scheme.

Kinetic comparative study on aerodynamic characteristics of hypersonic reentry vehicle from near-continuous flow to free molecular flow

A scaled model of the X38-like configuration was simulated under hypersonic conditions for the direct simulation Monte Carlo method and the unified gas kinetic scheme. The inflow conditions considered several flow regimes, from the near-continuum through the slip-transitional to the free molecular regime. Flow fields and surface properties were compared in detail between these two methods. Not only the density and temperature contours distribution but also the surface pressure, heat flux, friction distribution, both kinetic methods give fairly consistent results. Aerodynamics of the model were also achieved and compared. The results provided by both methods agreed with each other very well. The effects of the Knudsen number and angle of attack were assessed. It is meaningful to carry out comparative studies and accelerate both methods to further progress.

Fault detection and isolation based on space projection operator for hypersonic re-entry vehicles with concurrent actuator faults

This article investigates fault detection, isolation and fault-tolerant control for an over-actuated system in hypersonic re-entry vehicle with concurrent actuator faults and disturbance. A series of residuals developed by spatial projection operators is only sensitive to certain faults that can decouple the effects of faults in different directions. Threshold intervals designed through sliding-time windows and a hypothesis test are used to detect faults. Single and concurrent fault isolation can be achieved by utilizing different residual combinations. Subsequently, an augmented observer is introduced to estimate the faults and satisfies the [Formula: see text]-gain constraint to reduce the effect of disturbances. Finally, an adaptive backstepping fault-tolerant control algorithm is designed to achieve stable attitude tracking. The stability of the proposed schemes is proved by Lyapunov and linear matrix inequality theories. Numerical simulation results demonstrate the effectiveness of the proposed methods.

Numerical simulation of hypersonic reaction flows with nonlinear coupled constitutive relations

As all known, there exists extremely thermal and chemical non-equilibrium phenomenon in hypersonic flows. Much effort has been put into the development of computational models for the prediction of such non-equilibrium flow. In order to obtain the real physical solution of the challenging non-equilibrium problems, Eu proposed a set of generalized hydrodynamic equations (GHE) from the viewpoint of generalized hydrodynamics. Based on Eu's GHE equations, Myong developed an efficient computational model, named as the nonlinear coupled constitutive relations (NCCR). The present study is based on the 3-D FVM NCCR model in conjunction with 7-species chemical reaction model to consider the reacting gas effect for hypersonic reentry vehicles. For further examining the performance of the proposed computational model, the typical engineering cases of Radio Attenuation Measurements (RAM)-C II vehicle are adopted. The flow contours, distribution profiles along stagnation line and surface properties are compared between nonlinear coupled constitutive model and those of the Navier-Stokes equation. The accuracy and physical consistency of the NCCR model are critically examined and validated for hypersonic reaction flow in the continuum region. For the near continuum region, the NCCR model can predict non-equilibrium phenomenon more accurately than NS equation through the comparison of shock stand-off distance and electron number density. The comparisons between NCCR model with one component perfect gas and multi-species reacting gas effect are also made to show the importance of chemical reaction source term.

Aerodynamic/reaction-jet compound control of hypersonic reentry vehicle using sliding mode control and neural learning

Considering the saturation of the aerodynamic surface (ADS) and the limitation of the actuator input, the paper investigates the aerodynamic/reaction-jet compound attitude control for the hypersonic reentry vehicle subject to poor aerodynamic maneuverability. The attitude control torque is preferentially allocated to the ADS. If the ADS is saturated, the remaining control torque is distributed to the reaction control system (RCS) through the control distribution algorithm to assist the ADS. For the dynamics uncertainty in the calculation of control torque, the terminal sliding mode (TSM) controller based on the back-stepping frame is designed to improve the robust performance and achieve the finite-time convergence. Furthermore, the predefined-time TSM controller is constructed with the online-data neural learning and the disturbance observer, which guarantee the predefined-time convergence and complete the effective approximation of system dynamics uncertainty. The stability of the attitude system is mathematically proved via Lyapunov function, while the simulation results are provided to show the effectiveness of the proposed controllers.

Robust fault accommodation strategy of the reentry vehicle: a disturbance estimate-triggered approach

This study proposes a novel fault accommodation scheme for the strong coupled attitude system of the hypersonic reentry vehicle (HRV) with both actuator drift and loss of efficiency. A general coupling/fault/uncertainty effect-triggered control concept is first introduced for the HRV attitude tracking system to improve its robustness and dynamic performance, which can be derived easily via Lyapunov stability. The design of such a control approach is based on an improved adaptive disturbance observer (ADO) to estimate the lumped uncertainties and actuator faults. The proposed scheme can achieve graceful degradation in tracking performance for the fault-tolerant control system by eliminating the detrimental uncertainty and actuator fault while keeping the beneficial uncertainty and actuator fault. A detailed design procedure has been presented with consideration of the implementation problem. Simulation results obtained on the HRV have demonstrated the effectiveness of the approach proposed.

A Novel IGC Scheme for RHV with the Capabilities of Online Aerodynamic Coefficient Estimation and Trajectory Generation

A novel integrated guidance and control (IGC) scheme for a Re-entry Hypersonic Vehicle (RHV) is proposed with the capabilities of online aerodynamic coefficient estimation based on an Unscented Kalman Filter and online trajectory generation based on the Gaussian pseudospectral method. A linear quadratic regulator is adopted for trajectory tracking guidance and a second-layer sliding mode controller is designed for attitude control. The variation of lift and drag coefficients are modeled and estimated online, based on which a new trajectory can be generated. The commands of trajectory generation are set as moments of actuators and their extremums pose more constraints on the rate and acceleration of flow angles. Comprehensive simulations are conducted and comparable IGC performances with normal conditions are obtained under large aerodynamic coefficient errors according to online generated trajectory, which proves the effectiveness and advantages of the proposed IGC scheme.

Catalytic recombination assessment on carbon in dissociated shock tube flow

Owing to its superior chemical stability at high temperatures, carbon is attractive as a candidate for ablation thermal protection system (TPS) materials for hypersonic re-entry vehicles. The catalytic recombination behavior is crucial to the ablation process during atmospheric entry because it provokes considerable heat flux at the surface. In the present study, catalytic efficiency values for oxygen and nitrogen recombination on carbon material have been determined by reflected shock experiments that can replicate the flow behavior of a hypersonic stagnation-point blunt body. Dissociated oxygen and nitrogen atoms were adequately produced adjacent to the shock tube endwall. Typical thin-film gauges coated with carbon are used for the stagnation heat-transfer measurements at the endwall. Before and after the tests, the properties of carbon were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Surface heat-transfer data were analyzed with catalytic heat-transfer theories. The role of recombination efficiency on the species mass fraction is also investigated by solving the governing equation for species conservation. The recombination efficiencies of carbon are found to be 0.0023 and 0.00075 for oxygen and nitrogen, respectively. It has been shown that the carbon surface is more catalytically active towards oxygen atoms than nitrogen atoms.

Analysis of nitrogen recombination activity on silicon dioxide with stagnation heat-transfer

Investigation of surface recombination activity of nitrogen on certain materials is crucial in the design of hypersonic re-entry vehicles. In the present work, an experimental study using a conventional shock tube facility has been conducted to investigate the phenomena of nitrogen recombination. Stagnation heat-transfer measurements were conducted behind reflected shock waves in a dissociated shock-tube flow for a mixture of 20% nitrogen and 80% argon. A platinum thin-film gauge was used to measure the stagnation heat-transfer in a shock heated gas mixture under a well-defined test condition. The surface of the heat-transfer gauge was coated with silicon dioxide (SiO2), the principal material used in thermal protection systems (TPS) for the hypersonic vehicles. Spectroscopic analyses were performed for in-depth characterization of the initial surface condition of the test specimen. Recombination activity behavior of nitrogen was evaluated by combining the heat-transfer data with catalytic heat transfer theories. The nitrogen recombination efficiency of silicon dioxide is found to be from 0.0026 to 0.035 at surface roughness factors of 1.01 to 1.10. Compared to the oxygen recombination activity, the nitrogen recombination activity showed a more than five times higher sensitivity to the roughness factor of the SiO2-coated surface.

Trajectory planning for hypersonic reentry vehicle satisfying deterministic and probabilistic constraints

The present work explores the optimal flight of aero-assisted reentry vehicles during the atmospheric entry flight phase with the consideration of both deterministic and control chance constraints. To describe the mission profile, a chance-constrained optimal control model is established. Due to the existence of probabilistic constraints (chance constraints), standard numerical trajectory planning algorithms cannot be directly applied to address the considered problem. Hence, we firstly present an approximation-based strategy to replace the probabilistic constraint by a deterministic version. In this way, the transformed optimal control model becomes solvable for standard trajectory optimization methods. In order to obtain enhanced computational performance, an alternative convex-relaxed optimal control formulation is also given. This is achieved by convexifying the vehicle nonlinear dynamics/constraints and by introducing a convex probabilistic constraint handling strategy. Numerical simulations are provided to demonstrate the effectiveness of these two chance-constrained optimization approaches and the corresponding probabilistic constraint handling strategies.

Computational simulations of near-continuum gas flow using Navier-Stokes-Fourier equations with slip and jump conditions based on the modal discontinuous Galerkin method

Blunt-body configurations are the most common geometries adopted for non-lifting re-entry vehicles. Hypersonic re-entry vehicles experience different flow regimes during flight due to drastic changes in atmospheric density. The conventional Navier-Stokes-Fourier equations with no-slip and no-jump boundary conditions may not provide accurate information regarding the aerothermodynamic properties of blunt-bodies in flow regimes away from the continuum. In addition, direct simulation Monte Carlo method requires significant computational resources to analyze the near-continuum flow regime. To overcome these shortcomings, the Navier-Stokes-Fourier equations with slip and jump conditions were numerically solved. A mixed-type modal discontinuous Galerkin method was employed to achieve the appropriate numerical accuracy. The computational simulations were conducted for different blunt-body configurations with varying freestream Mach and Knudsen numbers. The results show that the drag coefficient decreases with an increased Mach number, while the heat flux coefficient increases. On the other hand, both the drag and heat flux coefficients increase with a larger Knudsen number. Moreover, for an Apollo-like blunt-body configuration, as the flow enters into non-continuum regimes, there are considerable losses in the lift-to-drag ratio and stability.

Performance-Involved Coupling Effect-Triggered Scheme for Robust Attitude Control of HRV

This article investigates the relationship between the tracking performance and coupling effect for attitude tracking issue of hypersonic reentry vehicle (HRV), and proposes a performance-involved coupling effect-triggered robust control scheme. The main feature of the article lies in that the influence of the coupling effect on the performance is discussed via a defined performance-involved coupling effect indicator. Consequently, the proposed control ensures the transient performance within the prescribed limitation in all phases, and the better transient performance is achieved with the help of the sliding mode control and disturbance observer technique enhancing the robustness. Comparison simulations and Monte Carlo tests under coefficients perturbation on the HRV system demonstrate the effectiveness of the proposed control strategy.

Ablative Heating Technology in Hypersonic Re-entry Vehicles and Cruise Aircrafts

The aim of researches conducted in thermal protection systems in aeronautics and astronautics field of engineering is to generally defend the craft from high heat loads during operation while operating at hypersonic regimes in air and space. The motive of the following composition is to draft a review analysis on ablative heating materials as thermal protective equipment on reusable planetary/atmospheric re-entry vehicles such as a space shuttle, an inter-continental ballistic missile, or a hypersonic cruise missile. The heat liberation can cause much damage to the aircraft/spacecraft whilst operation which is generally beyond repair. It is therefore of utmost importance to research multiple strategy to reduce the effect of shockwaves damage to spacecraft/aircraft materials. We shall initiate the analysis by mentioning some re-usable tile thermal protection system types such as high temperature reusable surface insulation tiles (H.R.S.I), fibrous refectory composite insulation tiles (F.R.C.I), low temperature reusable surface insulation tiles (L.R.S.I) and gradually move on to ablative thermal protection systems with the advent of reinforced carbon-carbon’s application in astronautics and aeronautics respectively.