Aerospace

27 pages, 7226 KiB

Open AccessArticle

Experimental Thermohydraulic Assessment of Novel Curved Ribs for Heat Exchanger Tubes: A Machine Learning Approach

by Prashant Deshmukh, Subhash Lahane, Hari Sumant, Abhishek D. Patange and Sakthivel Gnanasekaran

Aerospace 2023, 10(7), 658; https://doi.org/10.3390/aerospace10070658 - 24 Jul 2023

Viewed by 819

Heat transfer enhancement using curved ribs of different cross sections, viz., square, rectangular, triangular, and circular, is a crucial study for designing heat-exchanging devices for various applications, and their thermohydraulic performance prediction using machine learning technique is a vital part of the modern [...] Read more.

Heat transfer enhancement using curved ribs of different cross sections, viz., square, rectangular, triangular, and circular, is a crucial study for designing heat-exchanging devices for various applications, and their thermohydraulic performance prediction using machine learning technique is a vital part of the modern world. An experimental study on using curved ribs suitable for heat transfer enhancement for the circular tube is presented for turbulent airflow with Reynolds numbers varying from 10,000 to 50,000. The machine learning methodology is used to predict the thermohydraulic performance assessment of curved ribs. The square cross-sectioned curved ribs produce the highest performance factor R3 of 1.5 to 2.65 to the equivalent Reynolds number Rec value of 20,000. It is observed that most of the curved rib configurations show a performance ratio R3 maximum and are suitable at a low Reynolds number value. At moderate and high Reynolds number values, the performance factor values decrease due to a rise in the pressure drop values for a few curved rib configurations. An artificial neural network (ANN) model predicts with an accuracy of 95% with the present study experimental values for the heat transfer performance indicators like average heat transfer enhancement Nua/Nus, average heat transfer enhancement fa/fs, and performance ratio R3, i.e., Nua/Nuc. Full article

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10 pages, 2051 KiB

Open AccessArticle

Measurement and Uncertainty Analysis of Lunar Soil Water Content via Heating Flux Method

by Ziheng Liu, Huaiyu He, Jiannan Li, Jialong Hao, Junyue Tang, Zhiheng Zhang, Shengyuan Jiang, Guanxin Chi, Ranran Liu, Lei Wang, Hao Geng and Changbin Xue

Aerospace 2023, 10(7), 657; https://doi.org/10.3390/aerospace10070657 - 24 Jul 2023

Cited by 2 | Viewed by 897

Abstract

According to the big impact hypothesis, the moon should be very dry. However, more and more evidence from the remote sensing of the moon in recent years indicates that there is a lot of water in the moon’s polar regions. Researching the source [...] Read more.

According to the big impact hypothesis, the moon should be very dry. However, more and more evidence from the remote sensing of the moon in recent years indicates that there is a lot of water in the moon’s polar regions. Researching the source and distribution of volatiles such as water can provide a key constraint on the formation and evolution of the moon. If there is a large amount of a volatile such as water ice in the polar area of the moon, it can be used as a further resource. Regrettably, there are no detectors in place to detect the amount and presence of water to date. In the new wave of lunar exploration, polar water has become one of the main tasks of NASA, ESA and RKA. The Chang’e-7 spacecraft of China’s fourth lunar exploration phase has also used the Water Molecular Analyzer and the Lunar Soil Volatile Measuring Instrument to detect water content in the lunar polar region. This paper introduces a set of methods and principles for analyzing water content via the heat flux method according to the characteristics of the Lunar Soil Volatile Measuring Instrument that was deployed on the lunar surface. According to the current design, the water content of 0.008~0.17% can be analyzed. Full article

(This article belongs to the Special Issue Space Sampling and Exploration Robotics)

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20 pages, 9080 KiB

Open AccessArticle

Numerical Investigation of Combustion Mechanism with Multi-Position Injection in a Dual-Mode Combustor

by Wenxiong Xi, Hui Xu, Tianyang Dong, Zhiyong Lin and Jian Liu

Aerospace 2023, 10(7), 656; https://doi.org/10.3390/aerospace10070656 - 24 Jul 2023

Viewed by 900

Abstract

To improve the flame propagation, combustion stability, and uniformity of the temperature field, multi-position injection is applied in a dual-mode combustor by controlling heat release in different locations. Using the chemical reaction of the finite rate combustion model and the detailed reaction mechanism [...] Read more.

To improve the flame propagation, combustion stability, and uniformity of the temperature field, multi-position injection is applied in a dual-mode combustor by controlling heat release in different locations. Using the chemical reaction of the finite rate combustion model and the detailed reaction mechanism of hydrogen combustion as described by Jachimowski, the influence of different multi-position injection patterns in a dual-mode combustor is analyzed. The one-equation Large Eddy Simulation (LES) turbulence model was chosen to define the sublattice turbulent viscous terms in a three-dimensional scramjet model. Based on a combustion chamber, the effect of the injection equivalent ratio (0.35–0.70), the relative position of the nozzle holes, and the injection pressure on the combustion process and flow field characteristics are analyzed with multi-position injection. The combustion efficiency, total pressure recovery coefficients, and pressure distribution under different operation conditions are compared. We observed that the combustion intensity increases and the upstream combustion shock string distance becomes greater with increased equivalent ratios. When the global equivalent ratio of multi-position injection remains unchanged, the arrangement of nozzles with the small injection spacing, i.e., two injection holes arranged face to face on the upper and lower walls, or the setting of multiple injection holes with the same pressure, can effectively increase the stability rate of the combustion flow field. In addition, the combustion efficiency at the outlet and the internal pressure of the combustion chamber in the stable state are also improved, relative to the increased total pressure loss. Full article

(This article belongs to the Section Aeronautics)

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17 pages, 8008 KiB

Open AccessArticle

Experimental and Numerical Investigation on Finned Vortex Reducer in a Rotating Cavity with a Radial Inflow

by Jian He, Xiang Luo, Yang Bai, An Song and Tao Yang

Aerospace 2023, 10(7), 655; https://doi.org/10.3390/aerospace10070655 - 23 Jul 2023

Cited by 1 | Viewed by 928

Abstract

In aero-engines, a secondary air system is used to cool the rotor discs and seal cavities between rotor and stator parts. The pressure loss caused by bleed air can be effectively reduced by setting the finned vortex reducer. Thus, the bleed system design [...] Read more.

In aero-engines, a secondary air system is used to cool the rotor discs and seal cavities between rotor and stator parts. The pressure loss caused by bleed air can be effectively reduced by setting the finned vortex reducer. Thus, the bleed system design can be optimized by researching the flow structure and pressure loss of each section in the cavity with a finned vortex reducer. In this study, the influence of different installation positions of a finned vortex reducer on the pressure loss characteristics was investigated through experimental and numerical simulation methods, focusing on the radial inflow of the secondary air system. The results indicate that the inlet and outlet positions of the fins affect the flow structure in the cavity. The aerodynamic parameters (rotational Reynolds number Re_Φ and mass flow rate coefficient C_w), together with the inlet and outlet radii of the fins, influence the pressure loss in the cavity. Considering the swirl ratio β constrained by the fins, a pressure loss model was established, which showed good agreement with the experimentally measured pressure loss. This model reflects the impact of the inlet and outlet positions of the fins on the pressure loss characteristics. Full article

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24 pages, 6662 KiB

Open AccessArticle

An Online Generation Method of Terminal-Area Trajectories for Wave-Rider Using Deep Neural Networks

by Zhe Liu, Jie Yan, Bangcheng Ai, Yonghua Fan, Kai Luo, Guodong Cai and Jiankai Qin

Aerospace 2023, 10(7), 654; https://doi.org/10.3390/aerospace10070654 - 23 Jul 2023

Viewed by 942

Abstract

This paper presents a deep neural network-based online trajectory generation method for the aerodynamic characteristic description and terminal-area energy management of wave-rider aircrafts. First, the flight dynamics equations in the energy domain are linearized and discretized to generate numerous aircraft trajectory samples with [...] Read more.

This paper presents a deep neural network-based online trajectory generation method for the aerodynamic characteristic description and terminal-area energy management of wave-rider aircrafts. First, the flight dynamics equations in the energy domain are linearized and discretized to generate numerous aircraft trajectory samples with sequential convex optimization (SCO) methods. Then, an optimization objective function is designed to promote the smoothness of the control variables and improve the trajectory similarity. Compared to the nonlinear programming (NLP), the proposed trajectory sample generation method is more suitable for the training of deep neural networks (DNNs). Finally, deep neural networks are formulated and trained for the control variables and state variables, using the generated obtained trajectory samples, so that the reference trajectories can be obtained online during the energy management process of the wave-rider’s terminal phase. Numerical simulations validate the high accuracy of the trajectories generated with the deep neural network. Meanwhile, this proposed method enables smaller storage usage, which is highly suitable for integration into on-board flight control systems. Full article

(This article belongs to the Topic Target Tracking, Guidance, and Navigation for Autonomous Systems)

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31 pages, 8315 KiB

Open AccessReview

3D Printing for Space Habitats: Requirements, Challenges, and Recent Advances

by Reza Hedayati and Victoria Stulova

Aerospace 2023, 10(7), 653; https://doi.org/10.3390/aerospace10070653 - 20 Jul 2023

Viewed by 2465

Abstract

Heavily resource-reliant transportation and harsh living conditions, where humans cannot survive without a proper habitat, have prevented humans from establishing colonies on the Moon and Mars. Due to the absence of an atmosphere, potential habitats on the Moon or Mars require thick and [...] Read more.

Heavily resource-reliant transportation and harsh living conditions, where humans cannot survive without a proper habitat, have prevented humans from establishing colonies on the Moon and Mars. Due to the absence of an atmosphere, potential habitats on the Moon or Mars require thick and strong structures that can withstand artificially produced internal pressure, potential meteoroid strikes, and the majority of incoming radiation. One promising way to overcome the noted challenges is the use of additive manufacturing (AM), also known as 3D printing. It allows producing structures from abundant materials with minimal material manipulation as compared to traditional constructing techniques. In addition to constructing the habitat itself, 3D printing can be utilized for manufacturing various tools that are useful for humans. Recycling used-up tools to compensate for damaged or unfunctional devices is also possible by melting down a tool back into raw material. While space 3D printing sounds good on paper, there are various challenges that still have to be considered for printing-assisted space missions. The conditions in space are drastically different from those on Earth. This includes factors such as the absence of gravity, infinitesimal pressure, and rapid changes in temperature. In this paper, a literature study on the prospects of additive manufacturing in space is presented. There are a variety of 3D printing techniques available, which differ according to the materials that can be utilized, the possible shapes of the final products, and the way solidification of the material occurs. In order to send humans to other celestial bodies, it is important to account for their needs and be able to fulfill them. An overview of requirements for potential space habitats and the challenges that arise when considering the use of additive manufacturing in space are also presented. Finally, current research progress on 3D printing Lunar and Martian habitats and smaller items is reviewed. Full article

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16 pages, 1106 KiB

Open AccessArticle

Trajectory Optimization for Multi-Sensor Multi-Target Search and Tracking with Bearing-Only Measurements

by Xiwen Yang, Hang Yin, Shaoming He, Ye Xie and Hyo-Sang Shin

Aerospace 2023, 10(7), 652; https://doi.org/10.3390/aerospace10070652 - 20 Jul 2023

Viewed by 1145

Abstract

This paper proposes a trajectory optimization approach for multi-sensor multi-target search and tracking using bearing-only sensors. Based on the framework of the joint integrated probabilistic data association (JIPDA) filter, the intensity of potential unknown targets is updated according to the trajectories of the [...] Read more.

This paper proposes a trajectory optimization approach for multi-sensor multi-target search and tracking using bearing-only sensors. Based on the framework of the joint integrated probabilistic data association (JIPDA) filter, the intensity of potential unknown targets is updated according to the trajectories of the UAVs. The performance indices for target search and tracking are constructed based on, respectively, the intensity of unknown targets in the search area and the tracking error covariance. A dimensionless criterion, evaluating the search and tracking performance, is formulated and leveraged as the objective function of the UAV trajectory optimization problem. Simulations were carried out in different search and tracking scenarios to demonstrate the effectiveness of the proposed approach. Full article

(This article belongs to the Topic Target Tracking, Guidance, and Navigation for Autonomous Systems)

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26 pages, 59698 KiB

Open AccessArticle

Potential Propulsive and Aerodynamic Benefits of a New Aircraft Concept: A Low-Speed Experimental Study

by Pedro D. Bravo-Mosquera, Hernán D. Cerón-Muñoz and Fernando M. Catalano

Aerospace 2023, 10(7), 651; https://doi.org/10.3390/aerospace10070651 - 20 Jul 2023

Cited by 1 | Viewed by 2381

Abstract

The aerodynamic design of a new aircraft concept was investigated through subsonic wind-tunnel testing using 1:28-scale powered models. The aircraft configuration integrates a box-wing layout with engines located at the rear part of the fuselage. Measurements involved a back-to-back comparison between two aircraft [...] Read more.

The aerodynamic design of a new aircraft concept was investigated through subsonic wind-tunnel testing using 1:28-scale powered models. The aircraft configuration integrates a box-wing layout with engines located at the rear part of the fuselage. Measurements involved a back-to-back comparison between two aircraft models: a podded version whose engines were assembled on pylons and a boundary-layer ingestion (BLI) version that provided several system-level benefits. The flowfield was investigated through the power balance method and a variety of pressure flowfield and inlet flow distortion metrics. The results proved that the BLI configuration enhances the propulsive efficiency by reducing both the electrical power coefficient and the kinetic energy waste due to lower jet velocities. Furthermore, there was a reduction of the total pressure recovery due to pressure gradients inside the duct, thereby causing high distortion. Overall, this research highlights the importance of wind-tunnel testing to bring any aerodynamic technology to a sufficient level of maturity and to enable future new aircraft concepts. Full article

(This article belongs to the Special Issue Flight Dynamics, Control & Simulation)

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18 pages, 7835 KiB

Open AccessArticle

Cooperation of Thin-Airfoil Theory and Deep Learning for a Compact Airfoil Shape Parameterization

by Jianmiao Yi and Feng Deng

Aerospace 2023, 10(7), 650; https://doi.org/10.3390/aerospace10070650 - 20 Jul 2023

Viewed by 1042

Abstract

An airfoil shape parameterization that can generate a compact design space is highly desirable in practice. In this paper, a compact airfoil parameterization is proposed by incorporating deep learning into the PAERO parameterization method based on the thin-airfoil theory. Following the PAERO parameterization, [...] Read more.

An airfoil shape parameterization that can generate a compact design space is highly desirable in practice. In this paper, a compact airfoil parameterization is proposed by incorporating deep learning into the PAERO parameterization method based on the thin-airfoil theory. Following the PAERO parameterization, the mean camber line is represented by a number of aerodynamic performance parameters, which can be used to narrow down the design space according to the thin-airfoil theory. In order to further reduce the design space, the airfoil thickness distribution is represented by data-driven generative models, which are trained by the thickness distributions of existing airfoils. The trained models can automatically filter out the physically unreasonable airfoil shapes, resulting in a highly compact design space. The test results show that the proposed method is significantly more efficient and more robust than the widely used CST parameterization method for airfoil optimization. Full article

(This article belongs to the Section Aeronautics)

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24 pages, 10254 KiB

Open AccessArticle

Prepositive Synergistic Bulge Design for Improving Aerodynamic Performance of Submerged Inlet

by Xuan Bai and Baigang Mi

Aerospace 2023, 10(7), 649; https://doi.org/10.3390/aerospace10070649 - 20 Jul 2023

Cited by 1 | Viewed by 999

Abstract

A submerged inlet has good stealth characteristics and a low external drag, but it also has the disadvantage of low internal flow efficiency. In view of this, a new efficiency enhancement method based on the prepositive synergistic bulge of the inlet’s anterior lip [...] Read more.

A submerged inlet has good stealth characteristics and a low external drag, but it also has the disadvantage of low internal flow efficiency. In view of this, a new efficiency enhancement method based on the prepositive synergistic bulge of the inlet’s anterior lip is proposed. Taking the submerged inlet of an aircraft as the baseline configuration, a miniature bulge with a square bottom and an outer convex form is designed in front of the inlet’s anterior lip. Through the convex shape of the bulge, part of the low-energy boundary layer airflow is diverted away from the inlet’s entrance, so that the airflow greatly reduces the flow separation after entering the inlet, and the internal flow performance of the entire submerged inlet is improved. Taking the flow field of an aircraft in the classic cruise state as an example, the simulation analysis results show that the flow field characteristics of the entire submerged inlet are obviously improved after adding the synergistic bulge. The total pressure recovery coefficient of the new inlet configuration increased by 1.36%, the total pressure distortion index decreased by 10.86%, and the body drag only increased by 0.37% compared with the baseline case. According to calculations of synergistic bulge inlet configurations with different design parameters, the effect of this configuration is relatively stable, whereby the aspect ratio of the bulge has the greatest impact on the performance, and its value should not be less than 0.75. In addition to the advantages of not requiring additional components or occupying space and being easy to manufacture, the method of adding a synergistic bulge can improve the aerodynamic performance of the baseline inlet under most cruise flight conditions, and its additional drag is small, which gives it a wide applicability range. Full article

(This article belongs to the Section Aeronautics)

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13 pages, 939 KiB

Open AccessArticle

Estimating the Cost of Wildlife Strikes in Australian Aviation Using Random Forest Modeling

by Dan Parsons, Jason Ryan, Michael Malouf and Wayne Martin

Aerospace 2023, 10(7), 648; https://doi.org/10.3390/aerospace10070648 - 19 Jul 2023

Viewed by 1513

Abstract

Wildlife strikes in aviation represent a serious economic concern; however, in some jurisdictions, the costs associated with this phenomenon are not collected or shared. This hampers the industry’s ability to quantify the risk and assess the potential benefit from investment in effective wildlife [...] Read more.

Wildlife strikes in aviation represent a serious economic concern; however, in some jurisdictions, the costs associated with this phenomenon are not collected or shared. This hampers the industry’s ability to quantify the risk and assess the potential benefit from investment in effective wildlife hazard management activities. This research project has applied machine learning to the problem by training a random forest algorithm on wildlife strike cost data collected in the United States and predicting the costs associated with wildlife strikes in Australia. This method estimated a mean annual figure of AUD 7.9 million in repair costs and AUD 4.8 million in other costs from 2008 to 2017. It also provided year-on-year estimates showing variability through the reporting period that was not correlated with strike report numbers. This research provides a baseline figure for the Australian aviation industry to assess and review current and future wildlife hazard management practices. It also provides a technique for other countries, airlines, or airports to estimate the cost of wildlife strikes within their jurisdictions or operational environments. Full article

(This article belongs to the Collection Air Transportation—Operations and Management)

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18 pages, 9532 KiB

Open AccessArticle

A Novel Composite Helicopter Tail Rotor Blade with Enhanced Mechanical Properties

by Anton Hadăr, Andrei-Daniel Voicu, Florin Baciu, Daniel Vlăsceanu, Daniela-Ioana Tudose and Ştefan-Dan Pastramă

Aerospace 2023, 10(7), 647; https://doi.org/10.3390/aerospace10070647 - 19 Jul 2023

Cited by 1 | Viewed by 1920

Abstract

This paper describes the transition towards a composite structure, with the same overall aerodynamic characteristics, for a tail rotor blade of an IAR330 helicopter. The newly proposed structure of the composite blade is made of a carbon-roving spar embedded with epoxy resin, a [...] Read more.

This paper describes the transition towards a composite structure, with the same overall aerodynamic characteristics, for a tail rotor blade of an IAR330 helicopter. The newly proposed structure of the composite blade is made of a carbon-roving spar embedded with epoxy resin, a hexagonal-cell honeycomb core manufactured by fused deposition modelling, and an outer skin made of multiple carbon-fibre-reinforced laminae. The blade was manufactured by the authors using the hand lay-up method at a scale of 1:3 with respect to the real one, and all stages of the manufacturing process are extensively described in the paper. The experimental tests were performed on an Instron 8872 testing machine by applying a bending force on its free edge, similar to the testing methodology employed by various composite blade manufacturers. A three-dimensional numerical model of the tail rotor blade was conceived, analysed using the finite element method, and validated by comparing the numerical and experimental values of the maximum bending force. Further, the model was used for a complex finite element analysis that showed the very good behaviour of the proposed composite blade during flight and emphasized the main advantages brought by the proposed composite structure. Full article

(This article belongs to the Special Issue Advanced Aerospace Composite Materials)

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21 pages, 10532 KiB

Open AccessArticle

Aeroelastic Response of Spinning Projectiles with Large Slenderness Ratio at Supersonic Speed

by Qi Liu, Juanmian Lei, Yong Yu and Jintao Yin

Aerospace 2023, 10(7), 646; https://doi.org/10.3390/aerospace10070646 - 18 Jul 2023

Cited by 2 | Viewed by 1023

Abstract

Obvious aeroelastic deformation occurs in spinning projectiles with large slenderness ratio, which seriously affects flight stability and maneuverability. This paper investigates the aeroelastic response of spinning projectiles with large slenderness ratio under supersonic speed. Based on a dynamic mesh method, an unsteady numerical [...] Read more.

Obvious aeroelastic deformation occurs in spinning projectiles with large slenderness ratio, which seriously affects flight stability and maneuverability. This paper investigates the aeroelastic response of spinning projectiles with large slenderness ratio under supersonic speed. Based on a dynamic mesh method, an unsteady numerical simulation method is developed to study the aeroelasticity of spinning projectiles by coupling aerodynamics and structural dynamics. The numerical simulation method is well validated by the experimental results of AGARD 445.6 wing flutter. Then, the aeroelastic response of spinning projectiles with large slenderness ratio is numerically explored under different flight conditions. The aeroelastic response is obtained, revealing the presence of beat vibrations and variations in response frequency. Furthermore, the influence mechanism of flight conditions on the aeroelastic response is analyzed. The results suggest that the coupling of the first two modes of the projectile caused by the spinning motion leads to the occurrence of beat vibrations in the aeroelastic response; the coupling degree of the first two modes decreases as the angle of attack increases and it increases with the increase in spinning speed; and the time−averaged deformation caused by the time−averaged aerodynamic force is beneficial to the convergence of the aeroelastic response of spinning projectiles, while the rotation−induced Magnus effect is counterproductive. Full article

(This article belongs to the Special Issue Applied Aeroelasticity and Fluid-Structure Interaction)

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15 pages, 25726 KiB

Open AccessArticle

A Method for Constructing Health Indicators of the Engine Bleed Air System Using Multi-Level Feature Extraction

by Zhaobin Duan, Xidan Cao, Fangyu Hu, Peng Wang, Xi Chen and Lei Dong

Aerospace 2023, 10(7), 645; https://doi.org/10.3390/aerospace10070645 - 18 Jul 2023

Viewed by 981

Abstract

Traditional methods are unable to effectively assess the health status of engine bleed air systems. To address the limitation, this paper proposes a methodology for constructing health indicators using multi-level feature extraction. First, this approach involves data-level feature extraction from Quick Access Recorder [...] Read more.

Traditional methods are unable to effectively assess the health status of engine bleed air systems. To address the limitation, this paper proposes a methodology for constructing health indicators using multi-level feature extraction. First, this approach involves data-level feature extraction from Quick Access Recorder (QAR) data and employs a method of significance compensation to process the QAR data. Second, through unsupervised learning, the ResNet Deep Autoencoder (RDAE) is utilized to do the feature-level feature extraction from the processed data. This can solve the problem of lacking annotated data and obtain the health indicators of the engine bleed air system. Third, the method was experimented on one year of QAR data from a specific airline company. The results demonstrate that the RDAE approach achieves the best performance in constructing health indicators for the system. It achieves a miss rate of 0.0523 for the duct pressure of 5th stage bleed, reducing the miss rate by 0.2810 compared to Kernel Principal Component Analysis (KPCA). It also achieves a miss rate of 0 for the pre-cooler outlet temperature, reducing the miss rate by 0.0035 compared to the Deep Autoencoder (DAE). The results indicate that the proposed method provides a more effective assessment of the health status of the engine bleed air system. Full article

(This article belongs to the Special Issue Predictive Maintenance for Complex Systems—from Sensor Measurements to Prognostics to Maintenance Planning)

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24 pages, 8372 KiB

Open AccessArticle

Physics-Guided Neural Network Model for Aeroengine Control System Sensor Fault Diagnosis under Dynamic Conditions

by Huihui Li, Linfeng Gou, Huacong Li and Zhidan Liu

Aerospace 2023, 10(7), 644; https://doi.org/10.3390/aerospace10070644 - 18 Jul 2023

Cited by 5 | Viewed by 1414

Abstract

Sensor health assessments are of great importance for accurately understanding the health of an aeroengine, supporting maintenance decisions, and ensuring flight safety. This study proposes an intelligent framework based on a physically guided neural network (PGNN) and convolutional neural network (CNN) to diagnose [...] Read more.

Sensor health assessments are of great importance for accurately understanding the health of an aeroengine, supporting maintenance decisions, and ensuring flight safety. This study proposes an intelligent framework based on a physically guided neural network (PGNN) and convolutional neural network (CNN) to diagnose sensor faults under dynamic conditions. The strength of the approach is that it integrates information from physics-based performance models and deep learning models. In addition, it has the structure of prediction–residual–generation-fault classification that effectively decouples the interaction between sensor faults and system state changes. First, a PGNN generates the engine’s non-linear dynamic prediction output because the PGNN has the advantage of being able to handle temporal information from the long short-term memory (LSTM) network. We use a cross-physics–data fusion scheme as the prediction strategy to explore the hidden information of the physical model output and sensor measurement data. A novel loss function that considers physical discipline is also proposed to overcome the performance limitations of traditional data-driven models because of their physically inconsistent representations. Then, the predicted values of the PGNN are compared with the sensor measurements to obtain a residual signal. Finally, a convolutional neural network (CNN) is used to classify faults for residual signals and deliver diagnostic results. Furthermore, the feasibility of the proposed framework is demonstrated on an engine sensor fault dataset. The experimental results show that the proposed method outperforms the pure data-driven approach, with the predicted RMSE being reduced from 1.6731 to 0.9897 and the diagnostic accuracy reaching 95.9048%, thereby confirming its superior performance. Full article

(This article belongs to the Special Issue Aerospace Prognosis Technology)

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22 pages, 2088 KiB

Open AccessReview

Review of Alternative Sustainable Fuels for Hybrid Rocket Propulsion

by Francesco Barato

Aerospace 2023, 10(7), 643; https://doi.org/10.3390/aerospace10070643 - 17 Jul 2023

Cited by 3 | Viewed by 6170

Abstract

Hybrid rockets using specific oxidizer–fuel combinations are considered a green alternative to current propulsion systems, as they do not release very toxic or polluting exhausts, but only much less harmful substances such as carbon monoxide/dioxide and soot. However, in a long-term vision where [...] Read more.

Hybrid rockets using specific oxidizer–fuel combinations are considered a green alternative to current propulsion systems, as they do not release very toxic or polluting exhausts, but only much less harmful substances such as carbon monoxide/dioxide and soot. However, in a long-term vision where space access and rocket transportation become a daily routine all around the world, the simple use of current green propellants could begin to become insufficient if the rest of the industry already follows much stricter rules, which are expected to tighten significantly in the future, thereby making emissions from rocket flights no more negligible. In this paper, the possible use of alternative sustainable solid fuels for hybrid rockets that are not derived from fossil fuels and are ideally carbon neutral is investigated and discussed based on the available data in the hybrid literature and on the literature related to renewable fuels in general. Even if this topic is apparently far away from the current necessities, as hybrid propulsion is not yet operational, it is paramount to consider a long-term vision and associated research efforts to make sure that the potential hybrid propulsion introduction to the commercial market is more than a simple flash in the pan, but offers a solid opportunity. Full article

(This article belongs to the Special Issue Hybrid Rocket Engines)

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21 pages, 4679 KiB

Open AccessArticle

A Reinforcement Learning Method Based on an Improved Sampling Mechanism for Unmanned Aerial Vehicle Penetration

by Yue Wang, Kexv Li, Xing Zhuang, Xinyu Liu and Hanyu Li

Aerospace 2023, 10(7), 642; https://doi.org/10.3390/aerospace10070642 - 16 Jul 2023

Cited by 1 | Viewed by 1183

Abstract

The penetration of unmanned aerial vehicles (UAVs) is an important aspect of UAV games. In recent years, UAV penetration has generally been solved using artificial intelligence methods such as reinforcement learning. However, the high sample demand of the reinforcement learning method poses a [...] Read more.

The penetration of unmanned aerial vehicles (UAVs) is an important aspect of UAV games. In recent years, UAV penetration has generally been solved using artificial intelligence methods such as reinforcement learning. However, the high sample demand of the reinforcement learning method poses a significant challenge specifically in the context of UAV games. To improve the sample utilization in UAV penetration, this paper innovatively proposes an improved sampling mechanism called task completion division (TCD) and combines this method with the soft actor critic (SAC) algorithm to form the TCD-SAC algorithm. To compare the performance of the TCD-SAC algorithm with other related baseline algorithms, this study builds a dynamic environment, a UAV game, and conducts training and testing experiments in this environment. The results show that among all the algorithms, the TCD-SAC algorithm has the highest sample utilization rate and the best actual penetration results, and the algorithm has a good adaptability and robustness in dynamic environments. Full article

(This article belongs to the Section Aeronautics)

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38 pages, 47469 KiB

Open AccessArticle

Active Flow Control for Passage Vortex Reduction in a Linear Turbine Cascade with Various Tip Clearance Sizes Using a Dielectric Barrier Discharge Plasma Actuator

by Takayuki Matsunuma and Takehiko Segawa

Aerospace 2023, 10(7), 641; https://doi.org/10.3390/aerospace10070641 - 16 Jul 2023

Cited by 1 | Viewed by 1219

Abstract

In an axial-flow turbine of a jet engine used for aircraft propulsion, the passage vortex (PV) and tip leakage vortex (TLV) generated inside the blade passage deteriorate the aerodynamic performance. In this study, a dielectric barrier discharge plasma actuator (PA) was installed in [...] Read more.

In an axial-flow turbine of a jet engine used for aircraft propulsion, the passage vortex (PV) and tip leakage vortex (TLV) generated inside the blade passage deteriorate the aerodynamic performance. In this study, a dielectric barrier discharge plasma actuator (PA) was installed in the upstream endwall of the turbine cascade to suppress the PV. The effects of the presence or absence of tip clearance and the change in the size of the tip clearance on the vortex structure at the exit of the turbine cascade were observed by recording the flow velocity distributions using particle image velocimetry. In the absence of tip clearance, only the PV existed and was completely suppressed by the PA. By contrast, in the presence of tip clearance, a TLV occurred in addition to the PV. When the input voltage to the PA was varied with various tip clearance sizes, the change in the flow fields where the PV and TLV interfered was clarified. With tip clearance, the PV was suppressed as the input voltage increased; however, the TLV increased considerably. At each tip clearance size, changes in the center positions of the PV and TLV were observed at varying input voltages of the PA. With increasing input voltages of the PA, the center position of the PV moved to the pressure surface side of the tip of the adjacent blade, and the center position of the TLV moved toward the middle of the flow passage. With a larger tip clearance, the amount of movement at the center positions of both the PV and TLV increased. Full article

(This article belongs to the Special Issue Plasma Actuator)

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24 pages, 13235 KiB

Open AccessArticle

High-Precision Magnetic Testbed Design and Simulation for LEO Small-Satellite Control Test

by Jhonny Uscategui, Xinsheng Wang, Gerson Cuba and María Guarirapa

Aerospace 2023, 10(7), 640; https://doi.org/10.3390/aerospace10070640 - 15 Jul 2023

Viewed by 1277

Abstract

Small satellites with academic missions in low Earth orbit (LEO) employ magnetic attitude control systems primarily due to their ease of development and low cost. These systems utilize magnetorquers to generate a magnetic moment that interacts with Earth’s magnetic field, enabling controlled rotation [...] Read more.

Small satellites with academic missions in low Earth orbit (LEO) employ magnetic attitude control systems primarily due to their ease of development and low cost. These systems utilize magnetorquers to generate a magnetic moment that interacts with Earth’s magnetic field, enabling controlled rotation of the satellite around its three axes. The successful execution of these satellite missions relies heavily on rigorous magnetic testing conducted on the Attitude Determination and Control (ADC) subsystem. Hence, the design of a magnetic field simulator that enables precise testing is of utmost importance. This paper presents a comprehensive study, analysis, and verification of the construction of a magnetic testbed capable of accurately reproducing terrestrial magnetic fields in low Earth orbits. The research was conducted in four stages. Firstly, Matlab/Simulink software was employed to predict the satellite’s orbit and the corresponding Earth’s magnetic field affecting it. Secondly, the three-axis magnetic testbed was simulated using Ansys Maxwell software to validate its technical characteristics. In the third stage, based on the previous data, the testbed was assembled and integrated into a university laboratory. Finally, calibration, testing, and verification of the testbed’s results were performed while reproducing Earth’s magnetic field from the satellite’s orbit. The final outcome was a flexible testbed design with the results exhibiting a precision exceeding 99.89%. This confirms that the magnetic testbed reliably generates results during small-satellite magnetic control tests. Full article

(This article belongs to the Section Astronautics & Space Science)

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21 pages, 10212 KiB

Open AccessArticle

JT9D Engine Thrust Estimation and Model Sensitivity Analysis Using Gradient Boosting Regression Method

by Hung-Ta Wen, Hom-Yu Wu, Kuo-Chien Liao and Wei-Chuan Chen

Aerospace 2023, 10(7), 639; https://doi.org/10.3390/aerospace10070639 - 15 Jul 2023

Viewed by 1409

Abstract

In recent years, artificial intelligence (AI) technology has been applied in different research fields. In this study, the XGBoost regression model is proposed to estimate JT9D engine thrust. The model performance mean absolute error (MAE) is 0.004845, the mean-squared error (MSE) is 0.000161, [...] Read more.

In recent years, artificial intelligence (AI) technology has been applied in different research fields. In this study, the XGBoost regression model is proposed to estimate JT9D engine thrust. The model performance mean absolute error (MAE) is 0.004845, the mean-squared error (MSE) is 0.000161, and the coefficient of determination (R²) values of the training, validation, and testing subsets are 0.99, 0.99, and 0.98, respectively. Based on a model sensitivity analysis, the four parameters’ optimal values are as follows: the number of estimators is 900; the learning rate is 0.1; the maximum depth is 4, and the random state is 3. In addition, a comparison between the model performance in this study and that in a previous one was conducted. The MSE value is as low as 0.000021. Full article

(This article belongs to the Special Issue Machine Learning for Aeronautics)

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21 pages, 20353 KiB

Open AccessArticle

Airfoil Analysis and Optimization Using a Petrov–Galerkin Finite Element and Machine Learning

by Pedro Areias, Rodrigo Correia and Rui Melicio

Aerospace 2023, 10(7), 638; https://doi.org/10.3390/aerospace10070638 - 15 Jul 2023

Cited by 1 | Viewed by 1550

Abstract

For the analysis of low-speed incompressible fluid dynamics with turbulence around airfoils, we developed a finite element formulation based on a stabilized pressure and velocity formulation. To shape the optimization of bidimensional airfoils, this formulation is applied using machine learning (TensorFlow) and public [...] Read more.

For the analysis of low-speed incompressible fluid dynamics with turbulence around airfoils, we developed a finite element formulation based on a stabilized pressure and velocity formulation. To shape the optimization of bidimensional airfoils, this formulation is applied using machine learning (TensorFlow) and public domain global optimization algorithms. The goal is to maximize the lift-over-drag ratio by using the class-shape function transformation (CST) parameterization technique and machine learning. Specifically, we propose equal-order stabilized three-node triangles for the flow problem, standard three-node triangles for the approximate distance function (ADF) required in the turbulence stage, and stabilized three-node triangles for the Spalart–Allmaras turbulence model. The backward Euler time integration was employed. An implicit time-integration algorithm was adopted, and a solution was obtained using the Newton–Raphson method. This was made possible in the symbolic form via Mathematica with the AceGen package. Three benchmarks are presented, with Reynolds numbers up to

1 \times 10^{7}

, demonstrating remarkable robustness. After the assessment of the new finite element, we used machine learning and global optimization for four angles of attack to calculate airfoil designs that maximized

C_{L} / C_{D}

. Full article

(This article belongs to the Special Issue The 10th Anniversary of Aerospace: Advances in Aerospace Sciences and Technology)

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20 pages, 4589 KiB

Open AccessArticle

Disruptive Technologies Certification Standard Approach

by Gianpiero Buzzo, Lidia Travascio, Angela Vozella, Mauro Baldizzone, Monica Gily, Clarissa Casagrande, Vincenzo Martina and Emanuele Quarona

Aerospace 2023, 10(7), 637; https://doi.org/10.3390/aerospace10070637 - 15 Jul 2023

Cited by 1 | Viewed by 1197

Abstract

The current rapid technological change identifies the evolution of people’s transportation as one of the primary effects. Hybrid-electric propulsion reveals potential advantages, including fuel savings, lower pollution, and reduced noise emissions. It is becoming a viable alternative propulsion technology for ground and marine [...] Read more.

The current rapid technological change identifies the evolution of people’s transportation as one of the primary effects. Hybrid-electric propulsion reveals potential advantages, including fuel savings, lower pollution, and reduced noise emissions. It is becoming a viable alternative propulsion technology for ground and marine applications and the aviation sector. Hybrid-electric propulsion systems can meet the high demands of next-generation aircraft in terms of lower operating costs, economy, and fuel efficiency while maintaining high flight performance. Introducing similar disruptive technologies requires an evolution of the traditional certification approach and associated means of compliance. Even if it starts with evaluating a hybrid propulsion system, the proposed process can also be adopted in other areas where disruptive technologies need to be adopted, such as H2 fuel systems and active wings, to summarize some potential applications. The Certification Approach for Disruptive Technologies adopts a top–down process, reversing and mixing the usual certification approach currently used for aircraft. It is based on a safety assessment fully integrated into the system’s development. The result of this process will consist of a list of gaps in certification requirements, their classification based on gap solution impact, and proposals to close those gaps. Full article

(This article belongs to the Special Issue On-Board Systems Design for Aerospace Vehicles)

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17 pages, 6641 KiB

Open AccessArticle

Theoretical Stiffness Modeling and Application Research of a Novel Stacked Flexure Hinge

by Yonghong Zhang, Chengmin Wang, Shuangquan Tang, You Jiang, Hong Chen and Wenjie Ge

Aerospace 2023, 10(7), 636; https://doi.org/10.3390/aerospace10070636 - 14 Jul 2023

Viewed by 964

Abstract

This study investigates and designs a novel stacked hinge with low stiffness, large rotation angle, high strength, and length-adaptive functionality. Firstly, based on the large deformation theory of cantilever beams and relevant theories of leaf springs, a stiffness theoretical model for stacked flexure [...] Read more.

This study investigates and designs a novel stacked hinge with low stiffness, large rotation angle, high strength, and length-adaptive functionality. Firstly, based on the large deformation theory of cantilever beams and relevant theories of leaf springs, a stiffness theoretical model for stacked flexure hinges is established. Subsequently, the stiffness theoretical model is further modified by considering the frictional force, aiming to reduce errors. Secondly, a stiffness-testing experimental platform for this flexure hinge is designed to verify the correctness of the theoretical model. Finally, the stacked flexure hinge is applied to the trailing-edge mechanism of a variable camber wing, achieving a deformation target of 15° downward bending of the wing and demonstrating good shape retention, thereby proving the feasibility of the application. Full article

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14 pages, 8595 KiB

Open AccessArticle

Experimental Study on the Water Content Distribution of Profile Samples and the Improvement of Sampling Detection Methods

by Ye Tian, Jiahang Zhang, Junyue Tang, Wei Xu, Weiwei Zhang, Lijun Tao, Shengyuan Jiang and Yanbin Sun

Aerospace 2023, 10(7), 635; https://doi.org/10.3390/aerospace10070635 - 14 Jul 2023

Viewed by 861

Abstract

To provide reliable input information for the load design and extraction of lunar soil water ice samples, it is necessary to study the water content distribution and water migration of simulated lunar soil water ice samples. On this basis, the temperature field model [...] Read more.

To provide reliable input information for the load design and extraction of lunar soil water ice samples, it is necessary to study the water content distribution and water migration of simulated lunar soil water ice samples. On this basis, the temperature field model and the hydrothermal coupling relationship are proposed. The temperature field model was constructed by combining energy conservation and Fourier’s heat transfer law. The coupling relationship was established, and the hydrothermal coupling model was obtained by testing the unfrozen water content using the nuclear magnetic resonance method. Finite element software was used to solve the model numerically, and the water migration rule of the soil water ice samples at different ambient temperatures were analyzed. Thin-wall drilling tests were carried out on the simulated lunar soil water ice samples to obtain water content data for different locations, and the simulation results were verified. Due to the migration effect of the cold end of the water, the closer we tested to the edge of the sample, the higher the water content was. The higher the ambient temperature was, the more pronounced the water migration phenomenon of the whole sample was. These research results provide a basis for sampling scheme design. Full article

(This article belongs to the Special Issue Space Sampling and Exploration Robotics)

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23 pages, 9074 KiB

Open AccessArticle

Adaptive Convex Optimization Guidance for Lunar Landing

by Rongjun Mu, Yanpeng Deng and Peng Wu

Aerospace 2023, 10(7), 634; https://doi.org/10.3390/aerospace10070634 - 13 Jul 2023

Cited by 1 | Viewed by 1147

Abstract

In this paper, a novel guidance algorithm based on adaptive convex optimization is proposed to ensure robustness in the uncertainty of a lunar lander’s parameters and satisfy the constraints of terminal position, velocity, attitude, and thrust. To address the problem of parameter uncertainty [...] Read more.

In this paper, a novel guidance algorithm based on adaptive convex optimization is proposed to ensure robustness in the uncertainty of a lunar lander’s parameters and satisfy the constraints of terminal position, velocity, attitude, and thrust. To address the problem of parameter uncertainty in the landing process, the parameter-adaptive method is used to achieve online real-time optimal estimations of specific impulse and mass by the optimal observer, and the estimated parameters are used to realize optimal trajectory programming. To overcome the difficulty in constraining the attitude and the thrust level at the final stage in the convex optimization process, a rapid adjustment phase is added to meet the final attitude and thrust constraints; the target-adaptive method is used to adjust the target adaptively at the same time. Therefore, the position and velocity deviations caused by the rapid adjustment phase can be eliminated by the target offset. Finally, the results of numerical experiments demonstrate the effectiveness of the proposed algorithm. Full article

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20 pages, 5102 KiB

Open AccessArticle

Can the Orbital Debris Disease Be Cured Using Lasers?

by Stefan Scharring and Jürgen Kästel

Aerospace 2023, 10(7), 633; https://doi.org/10.3390/aerospace10070633 - 13 Jul 2023

Cited by 2 | Viewed by 1948

Abstract

Ground-based high-power lasers are, in principle, able to de-orbit any kind of space debris object from the low Earth orbit (LEO) by remotely inducing laser-ablative momentum. However, the assessment of efficiency and operational safety depends on many factors, like atmospheric constraints or the [...] Read more.

Ground-based high-power lasers are, in principle, able to de-orbit any kind of space debris object from the low Earth orbit (LEO) by remotely inducing laser-ablative momentum. However, the assessment of efficiency and operational safety depends on many factors, like atmospheric constraints or the risk of debris disintegration during irradiation. We analyze laser momentum for a great variety of target geometries and sizes and—for the first time in a large-scale simulation—include thermal constraints in the laser irradiation configuration. Using a coherently coupled 100 kJ laser system at 1030 nm wavelength and a 5 ns pulse duration in an optimized pointing elevation angle range, the pulse frequency should amount to less than 10 Hz to prevent fragment meltdown. For mechanically intact payloads or rocket bodies, repetition rates should be even lower. Small debris fragments sized between 10 and 40 cm can be de-orbited by employing around 100 to 400 station passes with head-on irradiation, while objects exceeding 2 m typically require far more than 1000 irradiations for de-orbit. Hence, laser-based debris removal cannot be considered a prime space sustainability measure to tackle the highest-risk large debris, yet it can provide the remediation of a multitude of small-sized debris using small networks of globally distributed laser sites. Full article

(This article belongs to the Special Issue Laser Propulsion Science and Technology)

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19 pages, 11258 KiB

Open AccessArticle

Unwanted Supplementary Vibrations of Helicopter Radio Communication Systems

by Marek Češkovič, Martin Schrötter, Róbert Huňady, Pavol Kurdel and Natália Gecejová

Aerospace 2023, 10(7), 632; https://doi.org/10.3390/aerospace10070632 - 13 Jul 2023

Viewed by 1224

Abstract

A helicopter in flight can be considered an unstable dynamic system with many unwanted vibrations originating from multiple sources, such as the operation of the engines and individual components. These vibrations cause the degradation of the structural and functional components of a helicopter, [...] Read more.

A helicopter in flight can be considered an unstable dynamic system with many unwanted vibrations originating from multiple sources, such as the operation of the engines and individual components. These vibrations cause the degradation of the structural and functional components of a helicopter, thereby generally reducing the utility and technical efficiency of the aircraft. During the analysis of frequently recurring errors of medium-heavy helicopters, partial damage to antenna elements with vertical polarisation was detected. These damages provided the basis for the presented research, based on which supplementary vibrations caused by unwanted electromagnetic oscillations were revealed. These oscillations were detected in the process of communication between the helicopter crew and the ground ATC (air traffic control) station. This phenomenon’s existence and negative influence were confirmed via measurements and modal analysis, based on which an exact synergy between harmonic frequencies of the helicopter’s normal vibrations was discovered. The obtained results serve as a theoretical and practical basis for the future monitoring of this phenomenon, especially in the process of determining the “health status” of medium-heavy helicopters. Full article

(This article belongs to the Section Aeronautics)

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15 pages, 3930 KiB

Open AccessArticle

The Impact of Battery Performance on Urban Air Mobility Operations

by Xiaotao Qiao, Guotao Chen, Weichao Lin and Jun Zhou

Aerospace 2023, 10(7), 631; https://doi.org/10.3390/aerospace10070631 - 13 Jul 2023

Cited by 2 | Viewed by 2187

Abstract

Urban air mobility (UAM) is a promising transportation concept that can effectively address city traffic congestion and environmental pollution. Power batteries are used extensively in UAM vehicles, and their technical characteristics (charge rate and specific energy) are coupled with other sizing parameters to [...] Read more.

Urban air mobility (UAM) is a promising transportation concept that can effectively address city traffic congestion and environmental pollution. Power batteries are used extensively in UAM vehicles, and their technical characteristics (charge rate and specific energy) are coupled with other sizing parameters to significantly impact the direct operating cost (DOC). This study develops a DOC model based on a standard flight profile and a detailed battery model to determine the impact of battery performance on UAM operations. The results reveal that for a given operating model and current battery technology, there is a narrower charge rate choice for different DOCs; a charging rate of at least 2–2.5 C is required for rational design. Advancements in specific energy are expected to reduce the DOC by 20–25% by 2035. This model reflects the impacts of battery performance on UAM operations, which is conducive to further developments in the UAM market. Full article

(This article belongs to the Special Issue Urban and Regional Air Mobility Research)

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23 pages, 12055 KiB

Open AccessArticle

Study on Low-Velocity Impact Performance of Coal-Based Carbon Foam Sandwich Structures in Thermal Protection Systems

by Qikai Zhuang, Peijie Yue, Kai Li, Xin Guo and Xiaoquan Cheng

Aerospace 2023, 10(7), 630; https://doi.org/10.3390/aerospace10070630 - 12 Jul 2023

Cited by 1 | Viewed by 928

Abstract

Coal-based carbon foam (CCF) has been widely used in the hypersonic vehicles’ thermal protection system (TPS) due to its good thermal insulation and mechanical properties. In addition, CCF can absorb large quantities of energy when crushed so that the CCF sandwich structure can [...] Read more.

Coal-based carbon foam (CCF) has been widely used in the hypersonic vehicles’ thermal protection system (TPS) due to its good thermal insulation and mechanical properties. In addition, CCF can absorb large quantities of energy when crushed so that the CCF sandwich structure can effectively improve the impact resistance of the TPS. However, there are few studies on the impact performance of CCF sandwich structures, even the mechanical constitutive model (MCM) of CCF. This research work built the CCF MCM and studied the low-velocity impact properties. A large number of experiments were implemented to establish an effective and comprehensive CCF MCM which has three parts: basic mechanical properties, multiaxial loading failure criteria, and hardening rules. A series of tests on the low-velocity impact performance of two CCF sandwich structures were carried out, and finite element models (FEMs) were established according to the CCF MCM to simulate these tests. The experimental and simulation results were in good agreement. The impact damage mechanism was revealed by the tests and the FEMs. The MCM can be used not only for the simulation of low-velocity impact process but also for failure analysis of other CCF structures, which will help to design CCF structures at a low cost. Full article

(This article belongs to the Special Issue Structural Design of Aerospace Vehicles)

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18 pages, 4063 KiB

Open AccessArticle

Design of Aerospace Vehicles’ Thermal Protection Based on Heat-Insulating Materials with Optimal Structure

by Oleg M. Alifanov, Margarita O. Salosina, Sergey A. Budnik and Aleksey V. Nenarokomov

Aerospace 2023, 10(7), 629; https://doi.org/10.3390/aerospace10070629 - 12 Jul 2023

Cited by 4 | Viewed by 1453

Abstract

Highly porous open-cell carbon materials have great potential for use as high-temperature thermal insulation for space vehicles due to a unique combination of properties: low density, high rigidity, sufficient compressive strength, and low thermal conductivity. The physical properties of these materials essentially depend [...] Read more.

Highly porous open-cell carbon materials have great potential for use as high-temperature thermal insulation for space vehicles due to a unique combination of properties: low density, high rigidity, sufficient compressive strength, and low thermal conductivity. The physical properties of these materials essentially depend on their microstructure. This implies the possibility of constructing a new advanced technique for the optimal design of multilayer thermal protection systems for aerospace vehicles, taking into account the dependence of materials’ thermal properties on microstructure. The formulation of the optimization problem traditional to thermal design implies the determination of the layer thicknesses that provide a minimum specific mass of the thermal protection, subject to the specified constraints on the maximum temperatures in the layers. The novelty of this work lies in the fact that, along with the thickness of the layers, the design parameters include the cell diameter and porosity, which characterize the structure of highly porous cellular materials. The innovative part of the presented paper lies in the determination of cell diameter and the porosity of open-cell carbon foam together with the thickness of the layers for multilayer thermal insulation, ensuring the required operational temperature on the boundaries of the layers and a minimum of the total mass of the system. This article reveals new possibilities for using the numerical optimization method to determine the geometric parameters of the thermal protection system and the morphology of the materials used. A new methodology for designing heat-loaded structures based on the simultaneous selection of macro- and micro-parameters of the system is proposed. The basic principles of constructing an algorithm for designing a multilayer thermal protection system are outlined, taking into account the possibility of choosing the parameters of the highly porous materials’ structure. The reliability of the developed optimization method was verified by comparing the results of mathematical modeling with experimental data obtained for highly porous cellular materials with known microstructure parameters. Full article

(This article belongs to the Special Issue The 10th Anniversary of Aerospace: Advances in Aerospace Sciences and Technology)

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