Reentry Research Articles (Page 1)

High-temperature nonequilibrium kinetics is widely encountered in hypersonic flight and atmospheric entry. The accurate acquisition of state-to-state (StS) reaction kinetic data is crucial for constructing nonequilibrium reaction databases and high-fidelity aerodynamic simulations. However, the problem still faces great challenges due to the complex energy transfer processes. Traditional computational methods struggle to balance accuracy and efficiency in predicting StS integral cross sections (ICSs) and rate coefficients. To address this, we proposed a mixed machine learning (ML) framework, GPR-NN, combining the uncertainty-guided sampling capability of Gaussian process regression (GPR) and the strong generalization performance of neural networks (NNs) for large-scale prediction. We applied GPR-NN to the O + O2 dissociation reaction. Based on quasi-classical trajectory (QCT) calculations on the 21A' potential energy surface, a converged GPR model was constructed using 583 ICSs at a wide range of initial conditions. The dataset was expanded to train the NN model using non-redundant input features. The GPR-NN framework exhibited excellent performance: for 319 additional test points not in the training, the root-mean-square error between QCT and GPR-NN predictions was only 0.1728Å2. The correlation coefficient R2 reached 0.9995, and the prediction time was reduced to 0.03s. Under thermal equilibrium conditions, the model-predicted dissociation rate coefficients agreed well with experiments. The model-predicted efficiency functions demonstrate superior accuracy in quantifying vibrational nonequilibrium effects compared to empirical models. By integrating GPR's uncertainty quantification capabilities into NN training, this study overcomes the limitations of individual ML approaches and establishes a scalable and efficient strategy for ML applications in high-temperature nonequilibrium kinetics.

Abstract The plasma around a reentry spacecraft causes the charged particles to interact with the electromagnetic waves emitted by the on-board antennas, and the vehicle experiences radio communication difficulties. A proposed way to mitigate the radio blackout is the magnetic field alleviation technique that consists of superimposing a magnetic field onto the flow, converting the plasma into an anisotropic medium, and changing its refractive index. The applied magnetic field leads to the creation of an extraordinary wave that can propagate for plasma frequencies higher than the radio signal frequency. In this work, a probe containing a cryogenically-cooled high-temperature superconducting magnet is used to study the effect of an applied magnetic field on the plasma flow and on the radio signal propagation, in the VKI Plasmatron facility. The magnetized plasma is characterized by optical emission spectroscopy, stagnation heat flux, and dynamic pressure measurements. The experimental radio signal measurements are conducted using conical horn antennas, operating at frequencies in the K $$_\text{a}$$ a -band. An antenna is placed inside of the magnetic probe, transmitting toward a stagnant air plasma flow. The applied magnetic field causes an increase of the flow temperature, leading to an augmentation of the plasma frequency and stagnation heat flux, due to the Hall effect. No significant effects are observed in the signal transmission and attenuation, while the signal reflection trend is consistent with the variation of magnetic field strength, and plasma and collision frequencies. The dependency of the Faraday rotation with the magnetic field and its direction is observed. While a clear demonstration of the magnetic window is not conclusively observed in the transmission parameters, the behavior of the reflection coefficient shows that the radio blackout mitigation is feasible at optimal combinations of flow ionization.

Study on the dynamics of an origami space plane during Earth atmospheric entry

Analysis of the potential availability of resuspended heavy metals from urban road sediments: A post-runoff approach.

Abstract Semi-trailer trucks are the backbone of any freight system throughout the world, as a major chunk of cargo is transported through them. These trucks transport high volumes of cargo, usually travelling at close to motorway speeds. Consequently, most energy consumed by these trucks is used to overcome the aerodynamic drag force. Therefore, it is important to minimize the drag force for enhancement in fuel consumption. In this study a traditional benchmark semi-trailer truck is compared to a novel modified geometry having a plate with side skirts to shield bluff bodies using a numerical simulation. Results show that there is a 7.71% reduction in fuel consumption compared to the benchmark case of the proposed modified semi-trailer truck. Furthermore, the addition of this novel plate removes the exposure of blunt bodies on the underside of the semi-trailer truck, particularly the axle, differential and suspension components to the oncoming air considerably reducing the drag force. A reduction in this drag force will directly result in improved energy consumption of the truck. Eventually, this would result in lower harmful gas emissions and transportation costs of goods. The implications of this research could be extended to different truck variants beneficial for researchers, transporters, and policymakers.

Abstract A comprehensive understanding of the interaction between electromagnetic field and weakly ionized plasma layer is crucial for modeling magnetohydrodynamic manipulation of re-entry vehicles. In this study, a systematic framework is developed to assess the multi-process effects in weakly ionized hypersonic plasma flows under electromagnetic fields during atmospheric reentry. A decoupled modeling approach is adopted, in which the stagnation region is approximated as a one-dimensional inviscid normal shock to efficiently compute thermochemical states across a wide flight envelope (3-16 km/s, 0-85 km). Thermochemical non-equilibrium is modeled using Park’s two-temperature formulation, with both 7- and 11-species air chemistry models considered. A comprehensive parametric study is then conducted to evaluate the validity of multi-process coupling models and key plasma criteria including oscillation, cyclotron and collision of particles as well as convection and diffusion of magnetohydrodynamic behavior. Critical electromagnetic similarity parameters—magnetic Reynolds number, Hall parameter, and ion slip parameter—are subsequently computed to determine the applicability maps where induced magnetic field, Hall effect, and ion slip effect become significant. Taking RAM C-II vehicle as an example, the results show that Hall and ion slip effects are non-negligible above 40 km and 70 km, respectively, when a 0.5 T magnetic field is applied. The induced magnetic field must be considered at velocities beyond 8 km/s due to the magnetic Reynolds number exceeding unity. Besides, the 11-species model is necessary above 8 km/s to ensure accuracy in ion species prediction. The analysis may provide physics-based criteria for selecting appropriate plasma models in hypersonic magnetohydrodynamic flow control applications.

Thermally induced vibration is a critical phenomenon in thin plates and shells subjected to rapid heating, with particular importance in aerospace reentry vehicles. For instance, in atmospheric reentry capsules, thin structural panels located behind the thermal protection system (TPS) are exposed to intense and sudden thermal shocks caused by high-speed airflow and shock waves, with heating rates reaching up to high temperatures. These panels, which often support electronic or structural subsystems, are highly susceptible to transient thermal deformation and vibration. In this study, the thermal vibration behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) circular plates is investigated. The material properties of the composite constituents are assumed to vary with both temperature and spatial position. Effective material properties are determined using appropriate homogenization techniques. A transient thermal loading scenario, involving a rapid temperature rise, is considered. The temperature distribution through the plate’s thickness is obtained by solving the transient heat conduction equation using a finite difference method in combination with a Crank–Nicolson time integration scheme. Based on the resulting temperature field, thermally induced radial and circumferential forces and moments are computed and incorporated into the governing dynamic equations. The equations of motion are derived using Hamilton’s principle and simplified under axisymmetric conditions due to symmetric loading and boundary constraints. The generalized differential quadrature (GDQ) method is employed for spatial discretization, while the Newmark time integration method is used to compute the transient response, including lateral deflection and other dynamic variables. After validating the proposed model against results from the literature, several novel findings are presented. Among these, it is shown that in orthotropic flat plates — such as the present FG-CNTRC structure — even under fully clamped boundary conditions, the plate undergoes immediate deformation upon exposure to transient thermal loading, without experiencing classical buckling instability.

The unprecedented increase in the number of objects orbiting the Earth necessitates a comprehensive characterisation of these objects to improve the effectiveness of Space Surveillance and Tracking (SST) operations. In particular, accurate knowledge of the attitude and physical properties of space objects has become critical for space debris mitigation measures, since these parameters directly influence major perturbation forces like atmospheric drag and solar radiation pressure. Characterising a space object beyond its orbital position improves the accuracy of SST activities such as collision risk assessment, atmospheric re-entry prediction, and the design of Active Debris Removal (ADR) and In-Orbit Servicing (IOS) missions. This study presents a novel approach for the simultaneous estimation of the attitude and optical reflective properties of uncontrolled space objects with known shape using light curves. The proposed method also accounts for atmospheric effects, particularly the Aerosol Optical Depth (AOD), a highly variable parameter that is difficult to determine through on-site measurements. The methodology integrates different estimation, optimisation, and data analysis techniques to achieve an accurate, robust, and computationally efficient solution. The performance of the method is demonstrated through the analysis of a simulated scenario representative of realistic operational conditions.

This study introduces a novel predictor-corrector guidance (PCG) law for re-entry vehicles based on generalized predictive control (GPC) to address the convergence and solvability challenges of traditional PCG. The guidance process begins by integrating vehicle dynamics to calculate the terminal range error, which is then embedded into a Controlled Autoregressive Integrated Moving Average (CARIMA) model. This converts the nonlinear equation-solving task in traditional PCG into a system stabilization problem. To address the challenge of significant parameter variations in the CARIMA model, which hinder parameter identification in GPC, a nonlinear transformation method is implemented to narrow the parameter range. This ensures the CARIMA model parameters remain within a smaller, manageable range, enabling accurate guidance command generation in each cycle. The convergence of terminal range errors is rigorously proven using a Lyapunov candidate. A feasibility analysis within the predictive control framework further confirms the method’s ability to resolve solvability issues inherent in traditional PCG. Unlike conventional methods, the proposed approach requires only a single dynamics integration per cycle, significantly improving computational efficiency. Extensive simulations on parachute-assisted landing re-entry vehicles with medium lift-to-drag ratios (L/D) across various flight scenarios demonstrate the algorithm’s accuracy, robustness, and computational efficiency. Comparative simulations verify that versus neural network controllers and iterative PCG, the proposed method achieves superior guidance accuracy with 80% less computational time relative to iterative PCG, making it a promising solution for practical re-entry guidance systems.

Abstract We report new results from a study of shock‐related features in the L6 ordinary chondrites Northwest Africa (NWA) 4672 and NWA 12841. Our observations confirm the occurrence of eight high‐pressure (HP) minerals in each meteorite, namely, ringwoodite, majorite, akimotoite, wadsleyite, albitic jadeite, lingunite, tuite, and xieite. Based on the calibration of phase stability fields and majorite chemical variations from static experiments, we estimate peak shock conditions of 18–23 GPa and 1800–2100°C. However, both meteorites also contain minerals thought to record lower pressures, 14–18 GPa for wadsleyite, and possibly ~11.5 GPa for albitic jadeite. These are interpreted to have formed by cooling during partial release from the peak shock state. Although the presence of discrete shock melt veins demands spatial heterogeneity in the temperature field, we interpret the record of HP mineralogy in terms of temporal rather than spatial variation in pressure–temperature conditions during the shock and release event. Specifically, we infer that the cooling of shock melt veins to their liquidus occurred near peak pressure, whereas decompression began before the melt veins reached their solidus. NWA 4672 and NWA 12841 also display dense networks of shock melt veins, metal–sulfide segregations, and dark shock zones, implying a high density of pre‐existing weak zones and, thus, a high likelihood of fragmentation during atmospheric entry. A comparison with the Suizhou L6 chondrite, in which a total of 26 HP phases have been identified, suggests that differences in the identification and number of observed HP polymorphs mostly reflect differences in the completeness and spatial scale of analytical studies rather than a true difference in the intensity of shock processing. It remains quite likely that many shocked L chondrites host more HP phases than have been recognized so far. These new results indicate a need for further high‐resolution studies of L chondrites to distinguish between observational bias and true variations in the range of shock states they experienced.

The Space Shuttle orbiter, a pioneering reusable spacecraft, navigated complex aerodynamic challenges during atmospheric re-entry. This paper investigates the aerodynamic behavior of transonic flow around its delta-wing design, focusing on shock-induced separation, vortex formation, and unsteady aerodynamic effects during descent and landing phases. Utilizing computational fluid dynamics (CFD) methods, including Euler and NavierStokes equations with zonal grid techniques, alongside experimental wind-tunnel campaigns, the study evaluates lift, drag, pressure distribution, and stability derivatives across Mach numbers from 0.8 to 1.2. Key findings highlight the significant influence of wingbody aerodynamic coupling on flutter speed and control surface effectiveness. By integrating numerical predictions with empirical data, the analysis validates existing models and provides insights into practical implications for future aerospace vehicle design. The results offer engineers critical guidance for optimizing designs and mitigating aeroelastic risks, particularly in reentry and subsonic-to-transonic transition scenarios.

Abstract Parachute deceleration systems play a critical role in both aerospace and aviation applications. Their deceleration efficiency and stability are particularly vital in missions such as spacecraft re-entry, landing, and cargo delivery, directly influencing mission success. With the continuous advancement of next-generation spacecraft and aerial vehicles, greater demands are being placed on the dynamic performance of parachute systems. This paper reviews recent progress in the dynamics of parachute deceleration systems, focusing on the characteristics of the inflation process, methods for aerodynamic parameter identification, and the selection of suitable degrees-of-freedom models. It examines the fluid-structure interaction effects and nonlinear behaviors during parachute inflation and analyzes the current inflation models and their applications. Furthermore, it explores aerodynamic parameter identification techniques, including commonly used methods such as genetic algorithms, and evaluates their respective strengths and limitations. The study also discusses the application of models with varying degrees of freedom in parachute systems and emphasizes the importance of selecting appropriate models based on mission-specific requirements. By synthesizing existing research, this paper provides theoretical insights and practical guidance for dynamic modeling and performance optimization of parachute deceleration systems.

Abstract Thermal Protection Systems (TPS) with enhanced thermal and ablation resistance are crucial for space vehicle re-entry. Deposition of Thermal Barrier Coatings (TBCs) on the carbon-based composites, incorporated with ceramic fillers, offer superior performance for advanced aerospace applications. Hence, this present work develops a composite by reinforcing Resorcinol Phenol Formaldehyde Resin (PR) with Polyacrylonitrile (PAN)-based Carbon Fiber Fabric (Cf-PR) composites. The Silicon Carbide (SiC) is incorporated in several concentrations (0, 1, 3, and 5 wt.%) followed by coating with 8wt.% of Yttria (Y2O3)-Stabilized Zirconia (YSZ) powder using Air Plasma Spray (APS). Thermal stability and ablation characteristics are assessed by Thermogravimetric Analysis (TGA) and the Oxyacetylene Torch Test (OAT) conducted at 400 W/cm² for 60 seconds respectively. The ablated surfaces' phase composition and microstructure are analyzed using X-ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM). Analysis revealed that Cf-PR 3wt.% SiC-YSZ coated composites exhibited enhanced thermal and ablation properties, making them strong candidates for advanced aerospace applications.

This paper explores the applications and limitations of purely inertial navigation systems, the use of global navigation satellite systems, and the integration of inertial navigation systems with global navigation satellite systems. A full trajectory simulation accounts for gravitational anomalies, atmospheric effects, and instrumentation errors with Monte Carlo sampling for uncertain parameters and complete error propagation. This simulation disambiguates the contributions of each source of uncertainty to the total error in the final impact point for a range of ballistic trajectories with and without maneuverable reentry vehicles and estimates the limitations to accuracy at intercontinental ranges. Based on these results, the paper discusses the potential for integration of inertial navigation systems with global navigation satellite systems to improve the accuracy of intercontinental ballistic missiles.

Flowfields around a model reentry vehicle, a scaled version of a CobraMRV, are investigated with a combination of high-speed planar laser Mie scattering and planar pulse-burst, cross-correlation, Doppler global velocimetry for scalar visualization and streamwise velocity measurements, respectively. Tests were conducted in the NASA Langley 4-Foot Supersonic Unitary Plan Wind Tunnel over a range of different tunnel operating conditions and model configurations and focused on the shock/boundary-layer interaction under the model. Pseudotomographic reconstructions of these flowfields were assessed for mean flow structure. Mach- and Reynolds-number-dependent effects were examined, including changes in bow-shock angle and standoff distance with Mach number along with global changes to the interaction topology with Reynolds number. Measurement uncertainties ranged from 50 to 150 m/s throughout the region of interest, driven largely by angular uncertainties. The mean measurement accuracy assessed in the tunnel freestream was 5.2% of tunnel-predicted values, while larger deviations were found in the immediate postshock regions due to assumptions made to assess velocity. Minor velocity and structural differences were also observed between repeated test cases. A series of recommendations to improve the fidelity of the velocimetry for future experiments by roughly a factor of 4 is given.

Discontinuous Trajectory Tracking of Hypersonic Glide Reentry Vehicle: An Intention Inference Approach

Uncontrolled reentry of Low Earth Orbit Decaying Objects: a hidden threat to global safety and legal frameworks

Recent Developments in Unsteady Flow Characteristics over Spiked Blunt Bodies: A Survey

Abstract The re-entry capsule measures its altitude by applying a barometric altimeter in the process of landing to the earth to determine the critical conditions for opening the parachute. The measurement accuracy of barometric altimeter has a direct impact on the operation of the parachute system, which in turn affects the safety of the re-entry capsule recovery and landing. In order to analyse the effect of the attitude on the static pressure measurements, a numerical simulation of the airflow field around the capsule during the descent process is carried out in this paper. The results show that different attitude angles lead to significant changes in the flow separation of the blunt body and the pressure distribution on it for constant altitude and descent velocity. By comparing the static pressures at the preset probes, the mechanism leads to deviation of the measured altitudes in various cases is quantitatively analysed. This study aims to support the determination of the attitude constraints of the re-entry capsule and the correction of the static pressure-altitude measurements during the landing process.

The effect of magnetohydrodynamic (MHD) interactions on the postshock naturally generated plasma is investigated in hypersonic flows with Mach numbers of 24, 20, and 16. High-fidelity continuum laminar simulations coupled with Lorentz force and Joule heating effects are carried out over an axisymmetric blunt-nosed body with an external magnetic field of about 1T. The shock and boundary-layer profiles are significantly altered with MHD interactions. If the body is sufficiently streamlined with a rounded nose to ensure plasma generation, modification of viscous interactions at the surface represents a promising method of drag and thermal load reduction at high Mach numbers. It is observed that MHD interactions are strong enough to induce flow separation for the case with the highest Mach number and lower Knudsen number. MHD interactions reduce thermochemical nonequilibrium in high-Knudsen-number cases, while simultaneously enhancing the concentration of ionic species around blunt bodies due to the increased flow residence time. The application of an external magnetic field decreases heat transfer and shear stresses near the leading edge by approximately 50%, thereby reducing the overall thermal and mechanical loads on the vehicle. The changes in ionized and neutral species concentration with the presence of magnetic fields are closely reported for three points along the reentry trajectory. The shock standoff distances are examined and compared with the existing data in the literature, showing very good agreement with the measurements, particularly for high-Knudsen-number flows.