Aerospace

4 pages, 162 KiB

Open AccessEditorial

Special Issue: Advances in CubeSat Sails and Tethers (1st Edition)

by Andris Slavinskis and Pekka Janhunen

Aerospace 2024, 11(12), 1016; https://doi.org/10.3390/aerospace11121016 - 11 Dec 2024

Currently, most space missions rely on chemical and electric propulsion systems, both of which are limited by the propellent tank volume whose “wet mass” is launched from the Earth [...] Full article

(This article belongs to the Special Issue Advances in CubeSat Sails and Tethers)

23 pages, 8949 KiB

Open AccessArticle

Optimized Design and Test of Geometrically Nonlinear Static Aeroelasticity Model for High-Speed High-Aspect-Ratio Wing

by Xing Li, Wei Qian, Ling Xiao, Xinyu Ai and Jun Liu

Aerospace 2024, 11(12), 1015; https://doi.org/10.3390/aerospace11121015 - 10 Dec 2024

Abstract

Large transport aircraft tend to adopt a wing layout with a high aspect ratio and swept-back angle due to the requirement of a high lift-to-drag ratio. Composite material is typically employed to ensure the light weight of the structure, causing serious static aeroelasticity [...] Read more.

Large transport aircraft tend to adopt a wing layout with a high aspect ratio and swept-back angle due to the requirement of a high lift-to-drag ratio. Composite material is typically employed to ensure the light weight of the structure, causing serious static aeroelasticity problems to the aircraft. When the airplane is flying in the transonic region, its aerodynamic load is very complex, and the large load leads to large deformation of the wing, triggering geometric nonlinear effects, which further affects the static aerodynamic elasticity characteristics of the wing. In this study, in order to study the static aeroelastic characteristics of the transonic flow of a high-aspect-ratio airfoil, a new design method of the scaled similar optimization model is described, and the change in the model lift coefficient due to geometrically nonlinear static aeroelasticity effects when the angle of attack is changed was investigated by using simulation and wind tunnel test methods. In order to ensure the accuracy of the wing shape when the model was deformed greatly, this study employed the structural design scheme of the wing with the skin as the main stiffness component, and the thicknesses of different regions of the skin were used as the design variables for the stiffness optimization design. The engineering algorithm of nonlinear finite elements was used in this study to calculate the curve of lift with the angle of attack considering the geometric nonlinear static aeroelasticity effect. The results show that the similarity optimization process employed in this study can be used to complete the design of the high-speed aerostatic wing test model, and the wind tunnel test results show that geometric nonlinearity has a large impact on the lift coefficient of the wing. Full article

(This article belongs to the Special Issue Aircraft Design and System Optimization)

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20 pages, 18565 KiB

Open AccessArticle

Accuracy Analysis of a Multi-Closed-Loop Truss Antenna with Clearance

by Di Wu, Jiang Zhao, Xiaofei Ma, Jinbao Chen and Chuanzhi Chen

Aerospace 2024, 11(12), 1014; https://doi.org/10.3390/aerospace11121014 - 10 Dec 2024

Abstract

Surface accuracy is one of the most crucial indicators for evaluating the performance of a large deployable antenna. It depends on the accuracy of the truss structure of the truss antenna. This paper presents a novel method for accurate analysis of a large [...] Read more.

Surface accuracy is one of the most crucial indicators for evaluating the performance of a large deployable antenna. It depends on the accuracy of the truss structure of the truss antenna. This paper presents a novel method for accurate analysis of a large deployable truss antenna with 3D joint clearances. The proposed method does not depend on the structure’s style, which is suitable for general multi-closed-loop structures. Firstly, the clearance model of the truss structure is established using a vector description. Then, an error transfer path analysis method is proposed for the multi-closed-loop structure. The distribution probability of the truss antenna’s surface accuracy is also obtained. The efficiency of the method is validated through a numerical example of a planar mechanism with a multi-closed loop. The proposed method is also applied to analyze the surface accuracy of the large deployable antenna with a parabolic cylindrical truss. Full article

(This article belongs to the Special Issue Space Mechanisms and Robots)

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11 pages, 4199 KiB

Open AccessArticle

Experimental Study on the Propulsion Performance of Laser Ablation Induced Pulsed Plasma

by Hang Song, Jifei Ye, Ming Wen, Haichao Cui and Wentao Zhao

Aerospace 2024, 11(12), 1013; https://doi.org/10.3390/aerospace11121013 - 9 Dec 2024

Abstract

This study investigates the influence of electromagnetic fields on the propulsion performance of laser plasma propulsion. Based on the principle of pulsed plasma thrusters, an electromagnetic field is utilized to accelerate laser plasma, achieving enhanced propulsion performance. This approach represents a novel method [...] Read more.

This study investigates the influence of electromagnetic fields on the propulsion performance of laser plasma propulsion. Based on the principle of pulsed plasma thrusters, an electromagnetic field is utilized to accelerate laser plasma, achieving enhanced propulsion performance. This approach represents a novel method for the electromagnetic enhancement of laser propulsion performance. In this paper, pulsed plasma thrusters induced by laser ablation are employed. The generated plasma is subjected to the Lorentz force under the influence of an electromagnetic field to obtain higher speed, thus increasing impulse and specific impulse. An experimental platform for laser-ablation plasma electromagnetic acceleration was constructed to explore the enhancement effect of discharge characteristics and propulsion performance. The results demonstrate that increased laser energy has little effect on discharge characteristics, while the trend of propulsion performance parameters initially rises and then declines. After coupling the electromagnetic field, the propulsion performance is significantly enhanced, with stronger electromagnetic fields yielding more pronounced effects. Full article

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17 pages, 4646 KiB

Open AccessArticle

Energy Absorption Behavior of Elastomeric Matrix Composites Reinforced with Hollow Glass Microspheres

by Gabrielle Schumacher, Colleen M. Murray, Jungjin Park and Norman M. Wereley

Aerospace 2024, 11(12), 1012; https://doi.org/10.3390/aerospace11121012 - 9 Dec 2024

Abstract

Hollow glass microsphere (HGM) reinforced composites are a suitable alternative to energy absorption materials in the automotive and aerospace industries, because of their high crush efficiency and energy absorption characteristics. In this study, a polyurethane elastomeric matrix was reinforced with HGMs for HGM [...] Read more.

Hollow glass microsphere (HGM) reinforced composites are a suitable alternative to energy absorption materials in the automotive and aerospace industries, because of their high crush efficiency and energy absorption characteristics. In this study, a polyurethane elastomeric matrix was reinforced with HGMs for HGM loadings ranging from 0 to 70 vol% (volume fraction). Quasi-static uniaxial compression tests were performed, subjecting the composite to compressive strains of up to 65%, to assess stress vs. strain and energy absorption characteristics. The results reveal that samples with a higher concentration of spheres generally exhibit better crush efficiency. Specifically, the highest crush efficiency was observed in samples with a 70 vol% HGM loading. A similar relationship was reflected in the energy absorption efficiency results, with the highest energy absorption observed in the 65 vol% sample. A correlation exists between the concentration of HGMs and important metrics such as mean crush stress and energy absorption efficiency. However, it is crucial to note that the optimal choice of sphere concentration varies depending on the desired performance characteristics of the material. Full article

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

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25 pages, 14833 KiB

Open AccessArticle

Investigation of Flow Control in an Ultra-Compact Serpentine Inlet with Fluidic Oscillators

by Lei Liu, Maolong Bai, Zhihao Wang, Zhengkang Lin, Kun Wang, Huijun Tan and Ziyun Wang

Aerospace 2024, 11(12), 1011; https://doi.org/10.3390/aerospace11121011 - 9 Dec 2024

Abstract

For optimal aerodynamic efficiency of specific ultra-compact serpentine intake, fluid oscillators are utilized to regulate airflow. This study employs advanced numerical simulation techniques to examine the effects of various control positions, jet angles, and excitation pressures on flow control efficacy. Control position significantly [...] Read more.

For optimal aerodynamic efficiency of specific ultra-compact serpentine intake, fluid oscillators are utilized to regulate airflow. This study employs advanced numerical simulation techniques to examine the effects of various control positions, jet angles, and excitation pressures on flow control efficacy. Control position significantly impacts the flow field structure within the intake, with a lower surface jet configuration outperforming an upper surface scheme. Optimal performance is achieved with the upper and lower surface jet angles set at 20° and 25°, respectively, under an input pressure of 2.5 times the total inlet pressure. This configuration enhances the total pressure recovery coefficient and reduces the steady-state circumferential distortion index and circumferential total pressure distortion coefficient. However, the flow rate ratio coefficient is notably high. While higher excitation pressures for the fluid oscillator do not inherently exhibit greater effectiveness, careful calibration is essential to accommodate varying positions. Optimal excitation pressure is established for the upper surface, while the control effect on the lower surface improves with increasing excitation pressure. Jet angles significantly affect the fluid oscillator’s control mechanism; small-angle jets effectively add energy to the separation zone, mitigating flow separation, whereas larger jet angles introduce excessive disturbances that outweigh their benefits. Overall, smaller jet angles enhance control effectiveness. Full article

(This article belongs to the Special Issue Environmental Influences on Aircraft Aerodynamics)

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16 pages, 8895 KiB

Open AccessArticle

Influence of Ice Growth Mode on the Ice Thickness and Shape Prediction of Two-Dimensional Airfoil

by Xiaobin Shen, Jingyu Zhao, Zekun Ye, Huanfa Wang and Guiping Lin

Aerospace 2024, 11(12), 1010; https://doi.org/10.3390/aerospace11121010 - 8 Dec 2024

Abstract

Computational results of aircraft icing and predictions of ice shape are not only determined by the solutions of air-supercooled droplet two-phase flow and icing thermodynamic models of surface water film, but are also influenced by the growth mode of the ice layer. Two [...] Read more.

Computational results of aircraft icing and predictions of ice shape are not only determined by the solutions of air-supercooled droplet two-phase flow and icing thermodynamic models of surface water film, but are also influenced by the growth mode of the ice layer. Two ice growth modes were established in a two-dimensional (2D) icing process simulation framework to calculate the ice thickness and ice shape, depending on whether surface deformation of the icing process was considered. Ice accretion simulations were performed with the two ice growth modes for an NACA0012 airfoil under rime ice and mixed ice conditions, and the results of ice amount, ice thickness, and ice shape were compared and analyzed. Under the same amount of ice formation, the ice thickness and ice shape obtained using different ice growth modes vary. The ice thickness and the ice shape size are relatively large without considering surface deformation, whereas the results with growth correction show a certain degree of reduction, which is more noticeable around the leading edge and the ice horns. However, the degrees of difference in ice thickness and ice shape are not the same, and the deviation in ice thickness is more obvious. Furthermore, the ice thickness and ice shape obtained using the ice growth correction mode are more consistent with experimental data and commercial software results, verifying the accuracy of the ice simulation method and the necessity of considering ice surface deformation. This paper is an essential guide for understanding the icing mechanism and accurately predicting two-dimensional ice shape. Full article

(This article belongs to the Special Issue Deicing and Anti-Icing of Aircraft (Volume IV))

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19 pages, 1265 KiB

Open AccessArticle

Neural Network-Based Descent Control for Landers with Sloshing and Mass Variation: A Cascade and Adaptive PID Strategy

by Angel Guillermo Ortega and Afroza Shirin

Aerospace 2024, 11(12), 1009; https://doi.org/10.3390/aerospace11121009 - 8 Dec 2024

Abstract

Autonomous control of lunar landers is essential for successful space missions, where precision and efficiency are crucial. This study presents a novel control strategy that leverages proportional, integral, and derivative (PID) controllers to manage the altitude, attitude, and position of a lunar lander, [...] Read more.

Autonomous control of lunar landers is essential for successful space missions, where precision and efficiency are crucial. This study presents a novel control strategy that leverages proportional, integral, and derivative (PID) controllers to manage the altitude, attitude, and position of a lunar lander, considering time-varying mass and sloshing behavior. Additionally, neural network models are developed, to approximate the lander’s mass properties as they change during descent. The challenge lies in the significant mass variations due to fuel, oxidizer, and pressurant consumption, which affect the lander’s inertia and sloshing behavior and complicate control efforts. We have developed a control-oriented model incorporating these mass dynamics, employing multiple PID controllers to linearize the system and enhance control precision. Altitude is maintained by one PID controller, while two others adjust the thrust vector control (TVC) gimbal angles to manage pitch and roll, with a fourth controller governing yaw via a reaction control system (RCS). A cascade PD controller further manages position by feeding commands to the attitude controllers, ensuring the lander reaches its target location. The lander’s TVC mechanism, equipped with a spherical gimbal, provides thrust in the desired direction, with control angles

α

and

β

regulated by the PID controllers. To improve the model’s accuracy, we have introduced time delays caused by fluid dynamics and actuator response, modeled via computational fluid dynamics (CFD). Fluid sloshing effects are also simulated as external forces acting on the lander. The neural networks are trained using data derived from computer-aided design (CAD) simulations of the lander vehicle, specifically the inertia tensor and the center of mass (COM) based on the varying mass levels in the tanks. The trained neural networks (NNs) can then use lander tank levels and orientation to inform and accurately predict the lander’s COM and inertia tensor in real time during the mission. The implications of this research are significant for future lunar missions, offering enhanced safety and efficiency in vehicle descent and landing operations. Our approach allows for real-time estimation of the lander’s state and for precise execution of maneuvers, verified through complex numerical simulations of the descent, hover, and landing phases. Full article

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

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19 pages, 7808 KiB

Open AccessArticle

Research on UAV Conflict Detection and Resolution Based on Tensor Operation and Improved Differential Evolution Algorithm

by Zhichong Zhou, Guhao Zhao, Yiru Jiang, Yarong Wu, Jiale Yang and Lingzhong Meng

Aerospace 2024, 11(12), 1008; https://doi.org/10.3390/aerospace11121008 - 8 Dec 2024

Abstract

With the widespread application of unmanned aerial vehicles (UAVs) in civilian and military fields, how to effectively detect and resolve conflicts of large-volume and high-density UAV flights in local airspace has become an important issue. This paper proposes a method for UAV conflict [...] Read more.

With the widespread application of unmanned aerial vehicles (UAVs) in civilian and military fields, how to effectively detect and resolve conflicts of large-volume and high-density UAV flights in local airspace has become an important issue. This paper proposes a method for UAV conflict detection and resolution based on tensor operation and an improved differential algorithm. Firstly, the UAV protection zone model and airspace rasterization model are constructed, and the rapid detection of flight conflicts is achieved by using the properties of tensor Hadamard product operations and prime factorization. Then, for the detected conflicts, a hybrid improved differential evolution algorithm is used for resolution. This algorithm improves the solution speed and quality by using an adaptive mutation operator and introducing a redundant evaluation mechanism and a confidence-based selection strategy. Simulation results show that this method can quickly and accurately detect and resolve flight conflicts in high-density UAV scenarios, with high timeliness and conflict resolution capability. Full article

(This article belongs to the Section Aeronautics)

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13 pages, 1108 KiB

Open AccessArticle

An Analysis of Direct Operating Costs for the Wright Spirit Electric Aircraft

by Katie Goodge and Paul Withey

Aerospace 2024, 11(12), 1007; https://doi.org/10.3390/aerospace11121007 - 6 Dec 2024

Abstract

Global warming and CO₂ emissions have become increasingly pressing concerns, with the aviation industry contributing significantly to these issues. In response, efforts have been made to develop environmentally sustainable aviation solutions. This paper examines the Direct Operating Costs (DOCs) of the Wright [...] Read more.

Global warming and CO₂ emissions have become increasingly pressing concerns, with the aviation industry contributing significantly to these issues. In response, efforts have been made to develop environmentally sustainable aviation solutions. This paper examines the Direct Operating Costs (DOCs) of the Wright Spirit, one of the options for electric flight, compared to the conventional BAe 146 on which the Wright Spirit is based. Utilising methodologies adapted from previous studies (largely the AEA method), the analysis investigates various factors influencing DOC including battery prices, flight duration, and charging time. The results indicate a 73% increase in overall DOCs from the BAe 146 to the Wright Spirit, largely influenced by battery costs and lifespan. However, an 83% reduction in fuel/energy costs suggests the potential viability of the Wright Spirit, particularly with anticipated reductions in battery prices. For instance, a quartering of battery prices could result in a GBP 5 increase in costs for 1 h flights; compared to the BAe 146. Moreover, the analysis finds the battery lifespan and charging time to be the most important factors to control in order to increase commercial feasibility. Ticket price comparisons suggest that the Wright Spirit’s costs align closely with current market prices, with a flight from Paris to Heathrow predicted to cost the airline GBP 136.10 per passenger. Future research could explore alternative electric aircraft designs to further assess their impact on DOCs and ticket prices Full article

(This article belongs to the Section Air Traffic and Transportation)

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15 pages, 5707 KiB

Open AccessArticle

Space Environment Monitoring Unit on Wentian Laboratory Cabin Module of China Space Station

by Huanxin Zhang, Guohong Shen, Donghui Hou, Shenyi Zhang, Chunqin Wang, Ying Sun, Liping Wang and Jiajie Liao

Aerospace 2024, 11(12), 1006; https://doi.org/10.3390/aerospace11121006 - 5 Dec 2024

Abstract

This article introduces the design and development of a space environment monitoring unit embedded in the versatile experimental assembly for electronic components outside the China space station’s Wentian laboratory cabin module. A newly designed comprehensive detection system is being used for the first [...] Read more.

This article introduces the design and development of a space environment monitoring unit embedded in the versatile experimental assembly for electronic components outside the China space station’s Wentian laboratory cabin module. A newly designed comprehensive detection system is being used for the first time in this kind of detector. The sensor head of the instrument includes a silicon telescope (composed of two silicon semiconductors) for measuring the LET spectrum and radiation dose rate, a typical chip for monitoring a single-event upset, and a CR-39 plastic nuclear track detector for detecting heavy ion tracks. The two silicon sensors stacked up and down are used for measuring the LET spectrum, which ranges from 0.001 to 100 MeV·cm²/mg. A sensor charge allocation method is adopted to divide the detection range into four cascaded levels, each achieving different detection ranges separately and then concatenated together, while traditional detection methods need multiple sets of probes to achieve the same dynamic range. At the same time, using the two sensors mentioned above, the silicon absorption dose rate under two different shielding thicknesses can be obtained through calculation, ranging from 10⁻⁵ to 10⁻¹ rad (Si)/h. Multiple calibration methods are applied on the ground. The preliminary in-orbit detection results are provided and compared with the simulation results obtained using the existing space environment model, and we analyze and discuss their differences. Full article

(This article belongs to the Special Issue Deep Space Exploration)

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17 pages, 7869 KiB

Open AccessArticle

Experimental Study on the Suppression of Cavity Noise in a Locking-On State by a Slanting Inner Wall

by Yuan Liu, Peiqing Liu and Hao Guo

Aerospace 2024, 11(12), 1005; https://doi.org/10.3390/aerospace11121005 - 4 Dec 2024

Abstract

This paper presents an experimental investigation into the noise characteristics of various slanted wall configurations. The study focuses on the noise suppression effects of cavities with slanted walls on cavity coupling noise. A total of eight configurations, with different slanting angles on the [...] Read more.

This paper presents an experimental investigation into the noise characteristics of various slanted wall configurations. The study focuses on the noise suppression effects of cavities with slanted walls on cavity coupling noise. A total of eight configurations, with different slanting angles on the front and rear walls, were analyzed by varying the inclination of the inner wall. Noise and flow field measurements were conducted in an aeroacoustic wind tunnel, utilizing microphones for near-field and far-field noise data acquisition and hot-wire probes for flow field analysis. The results indicate that larger slant angles lead to more effective noise reduction. As the slant angle increases, the acoustic resonance frequency associated with the slanted inner wall rises, which alters the self-excited oscillation modes involved in coupling with the acoustic resonance. This reduces the impact of coupling on the sound pressure levels. The change in acoustic resonance frequency also modifies the phase delay term of the dominant mode, ultimately leading to a shift in the noise frequency. Full article

(This article belongs to the Section Aeronautics)

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27 pages, 10948 KiB

Open AccessReview

Review on the Structure Design of Morphing Winglets

by Wenbo Wang and Guoqing Yuan

Aerospace 2024, 11(12), 1004; https://doi.org/10.3390/aerospace11121004 - 4 Dec 2024

Abstract

Winglets have a significant impact on the aerodynamic performance of aircraft. When aircraft are in different flight phases such as takeoff, climb, cruise, descent, and landing, traditional fixed winglets often cannot provide optimal performance gains. If winglets that can morph according to different [...] Read more.

Winglets have a significant impact on the aerodynamic performance of aircraft. When aircraft are in different flight phases such as takeoff, climb, cruise, descent, and landing, traditional fixed winglets often cannot provide optimal performance gains. If winglets that can morph according to different flight conditions are employed, it is expected that the aircraft’s lift-to-drag ratio and control performance can be optimized throughout the entire flight process. This paper reviews the current research status, from theoretical studies on the performance gains of morphing winglets and design studies based on mechanical transmission mechanisms, smart materials and novel structures, to optimization techniques and testing and verification technologies in the design of morphing winglets. It elucidates two main reasons for the low technological maturity of current morphing winglet research, and points out three areas worthy of further in-depth study. Full article

(This article belongs to the Special Issue Structures, Actuation and Control of Morphing Systems)

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18 pages, 1698 KiB

Open AccessArticle

An Optimization Method for Manned/Unmanned Aerial Vehicle Collaborative Operation System Architecture Based on PGQNSGA-II

by Xinyao Wang and Yunfeng Cao

Aerospace 2024, 11(12), 1003; https://doi.org/10.3390/aerospace11121003 - 4 Dec 2024

Abstract

The architecture of the Manned/Unmanned Aerial Vehicle Collaborative Operation System (MAV/UAV COS) is crucial for improving combat effectiveness and resource utilization efficiency. Optimizing this architecture involves managing complex, interdependent components, which presents a constrained multi-objective optimization challenge. Initially, the elements of the MAV/UAV [...] Read more.

The architecture of the Manned/Unmanned Aerial Vehicle Collaborative Operation System (MAV/UAV COS) is crucial for improving combat effectiveness and resource utilization efficiency. Optimizing this architecture involves managing complex, interdependent components, which presents a constrained multi-objective optimization challenge. Initially, the elements of the MAV/UAV COS architecture were analyzed and formally expressed, transforming the architecture optimization problem into a multi-objective optimization problem, with the objectives of maximizing total system effectiveness, command-and-control performance, and system execution performance. Constraints were formulated based on mission and payload information. Subsequently, a Quantum Non-Dominated Sorting Genetic Algorithm based on Preference Guidance (PGQNSGA-II) was developed, incorporating an adaptive quantum gate mechanism based on preference information to enhance chromosome updating, ensuring that the probability amplitude of quantum bits aligns more closely with the optimal chromosome. The simulation results demonstrate that the proposed PGQNSGA-II algorithm significantly enhances the global search capability and efficiency compared to traditional quantum genetic algorithms, making it well-suited for optimizing MAV/UAV COS architectures. Full article

(This article belongs to the Section Aeronautics)

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22 pages, 8186 KiB

Open AccessArticle

Unified Assessment of Open and Ducted Propulsors

by Rainer Schnell and Maximilian Mennicken

Aerospace 2024, 11(12), 1002; https://doi.org/10.3390/aerospace11121002 - 3 Dec 2024

Abstract

This paper reconciles the assessment of fan and propeller performance by deriving common metrics that describe their design and operational characteristics and applies them to real-world design examples. Historically, various applications with large differences in flight Mach number and thrust requirements have led [...] Read more.

This paper reconciles the assessment of fan and propeller performance by deriving common metrics that describe their design and operational characteristics and applies them to real-world design examples. Historically, various applications with large differences in flight Mach number and thrust requirements have led to different design methodologies and performance descriptors for ducted and unducted propulsors, making direct comparisons between these propulsion concepts challenging until today. One of the limitations of conventional propeller design methods is the difficulty in isolating the aerodynamic performance of blade sections from the overall design concept. The overall efficiency is largely impacted by top-level design parameters, while the aerodynamic quality is determined by the shaping and spanwise stacking of blade profiles. In contrast, turbomachinery design focuses primarily on the efficiency of the compression process and their respective efficiency metrics. This paper addresses these issues by systematically breaking down propeller efficiency into contributions commonly used in turbomachinery design. By applying consistent methodologies, we thereby enable a fair and quantitative comparison of the potential performance benefit of each concept. Furthermore, using common performance metrics simplifies the design process, making it more accessible to less experienced designers and facilitating the exploration of alternative design approaches for unducted propulsors. Full article

(This article belongs to the Section Aeronautics)

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16 pages, 690 KiB

Open AccessArticle

Characterization of an Ignition System for Nitromethane-Based Monopropellants

by Maxim Kurilov, Christoph U. Kirchberger and Stefan Schlechtriem

Aerospace 2024, 11(12), 1001; https://doi.org/10.3390/aerospace11121001 - 3 Dec 2024

Abstract

This paper presents the results of a hot-fire test campaign aimed at characterizing a newly developed ignition system for nitromethane-based green monopropellants. Nitromethane-based propellants are a cost-effective replacement for hydrazine and energetic ionic liquid hydrazine alternatives such as LMP-103S and ASCENT. The developed [...] Read more.

This paper presents the results of a hot-fire test campaign aimed at characterizing a newly developed ignition system for nitromethane-based green monopropellants. Nitromethane-based propellants are a cost-effective replacement for hydrazine and energetic ionic liquid hydrazine alternatives such as LMP-103S and ASCENT. The developed system uses a glow plug as the ignition source. Additionally, gaseous oxygen is injected simultaneously into the combustion chamber at the beginning of a firing. After closing the oxygen valve, a pure monopropellant operation follows. Three test series were carried out using NMP-001, a previously characterized nitromethane-based monopropellant. During the first test series, the required ROF for ignition was identified to be above 0.3. In the second test series, the low-pressure combustion limit was shown to be 13.9 bar, which is significantly lower than the 30 bar limit of heritage nitromethane-based monopropellants. In the third test series, the oxygen injection timing was optimized to minimize the required amount of oxygen for successful ignition to 1.5 g per ignition in this test setup. This approach to ignition is more cost effective than the catalytic initiation used for other monopropellants because neither costly precious-metal catalytic materials nor lengthy preheating procedures are required. Full article

(This article belongs to the Special Issue Green Propellants for In-Space Propulsion)

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23 pages, 3113 KiB

Open AccessArticle

Allocating New Slots in a Multi-Airport System Based on Capacity Expansion

by Sichen Liu, Shuce Wang, Minghua Hu, Lei Yang, Lei Liu and Yan Wang

Aerospace 2024, 11(12), 1000; https://doi.org/10.3390/aerospace11121000 - 2 Dec 2024

Abstract

Over time, the rapid expansion of civil aviation infrastructure has led to the establishment of multi-airport systems (MASs) or Metroplex, where airports situated in close proximity form interconnected networks. Given that individual airport capacities often fall short of meeting flight scheduling demands, devising [...] Read more.

Over time, the rapid expansion of civil aviation infrastructure has led to the establishment of multi-airport systems (MASs) or Metroplex, where airports situated in close proximity form interconnected networks. Given that individual airport capacities often fall short of meeting flight scheduling demands, devising effective multi-airport flight scheduling methods becomes imperative. This article introduces a novel MAS slot expansion configuration framework centered on coupling terminal areas. In contrast to conventional airport capacity slot expansion approaches, this framework demonstrates superior configurational efficacy within respective airport terminal environments. The model outlined in this research identifies the terminal control sector as the pivotal resource node within the interconnected terminal area, aiming to maximize the total expanded slots while minimizing the overall unfairness among airports within the terminal airspace. Employing the ε-constraint method facilitates the transformation of the minimization objective into solvable constraint conditions. Subsequently, leveraging Beijing Metroplex as a case study, the research devises benchmark, single-airport, multi-airport minimum, and multi-airport maximum scenarios to compare and analyze configuration outcomes in terms of key resource allocation impacts and coupled resource utilization efficiencies. Ultimately, employing the AirTOp fast-time simulation model validates each scenario, demonstrating that the proposed configuration method yields reduced delay levels and fewer conflicts in simulation environments. Full article

(This article belongs to the Special Issue Advances in Air Traffic and Airspace Control and Management (2nd Edition))

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24 pages, 6066 KiB

Open AccessArticle

Three-Dimensional Event-Triggered Predefined-Time Cooperative Guidance Law

by Dingye Zhang, Hang Yu, Keren Dai, Wenjun Yi, He Zhang, Jun Guan and Shusen Yuan

Aerospace 2024, 11(12), 999; https://doi.org/10.3390/aerospace11120999 - 2 Dec 2024

Abstract

To address the problem of multiple missiles attacking a maneuvering target simultaneously in three-dimensional space, we propose a new predefined-time cooperative guidance law based on an event-triggered mechanism. The settling time of the system states under this guidance law is independent of the [...] Read more.

To address the problem of multiple missiles attacking a maneuvering target simultaneously in three-dimensional space, we propose a new predefined-time cooperative guidance law based on an event-triggered mechanism. The settling time of the system states under this guidance law is independent of the initial states, and the upper bound of the settling time can be directly set by the explicit parameters in the guidance law. Firstly, the time-to-go estimate is taken as a consistency variable, and the communication failure and time-delay that are easily encountered during the communication process are taken into account; the event-triggered mechanism is introduced into the guidance law along the line of sight (LOS) direction, and the event-triggered threshold is given. Then, a predefined-time extended state observer is used to accurately estimate disturbances. In addition, the stability of the proposed guidance laws along and perpendicular to the LOS direction is proven by the Lyapunov theory. Finally, the superiority of the proposed guidance law introducing the event-triggered mechanism in reducing energy consumption and its effectiveness in encountering communication failure and time-delay are verified through simulations. Full article

(This article belongs to the Section Aeronautics)

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28 pages, 37860 KiB

Open AccessArticle

Study on Novel Radar Absorbing Grilles of Aircraft Engine Inlet Based on Metasurface Design Theory

by Xufei Wang, Yongqiang Shi, Qingzhen Yang, Huimin Xiang and Jin Bai

Aerospace 2024, 11(12), 998; https://doi.org/10.3390/aerospace11120998 - 2 Dec 2024

Abstract

In modern warfare, the advancement of low detectable technology has made the reduction of an aircraft radar cross section (RCS) crucial for survivability, while engine inlets significantly impact the overall detectability index as major forward scattering sources. Inspired by radar absorbing structures (RASs) [...] Read more.

In modern warfare, the advancement of low detectable technology has made the reduction of an aircraft radar cross section (RCS) crucial for survivability, while engine inlets significantly impact the overall detectability index as major forward scattering sources. Inspired by radar absorbing structures (RASs) based on metasurface theory, as well as the spoof surface plasmon polariton (SSPP) theory, this paper proposes a comprehensive design of radar absorbing grilles (RAGs) which are installed at the inlet aperture of the aircraft intake, where RAGs allow airflow to cross through and absorb the detecting radar wave. To enhance the ability of electromagnetic wave attenuation, an indium tin oxide (ITO) film is added in the middle of the RAGs to change the impedance characteristics. This study clarifies the mechanism influencing radar wave absorption characteristics through design parameters (unit length and sheet resistance) and radar characteristic parameters (frequency, incident angle, and polarization mode). The absorption peak gradually shifts towards lower frequencies with the increase in unit length from 8 to 16 mm of the grille. The integrated average absorption first increases and then decreases with the increase in sheet resistance from 100 to

800 Ω / □

applied as ITO film in the middle of the grille. When the unit length of RAG is 12 mm and

400 Ω / □

, the sheet resistance is applied, and a 90% absorption bandwidth is achieved to 100% within the 8–18 GHz band. The 90% absorption bandwidth reaches 72.3% in the 2–18 GHz band while maintaining absorption above 40% in the 2–8 GHz band. The integrated average absorption reaches 0.887, and the 90% absorption bandwidth increases to 255.6% of the original model’s bandwidth. The results indicate that the proposed RAGs based on metasurface exhibit broadband absorption performance and high angular stability, providing technical support for further application of these grilles in aircraft engine inlets. Full article

(This article belongs to the Section Aeronautics)

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Aerospace

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