Aerospace

26 pages, 2861 KiB

Open AccessArticle

Real-Time On-the-Fly Motion Planning for Urban Air Mobility via Updating Tree Data of Sampling-Based Algorithms Using Neural Network Inference

by Junlin Lou, Burak Yuksek, Gokhan Inalhan and Antonios Tsourdos

Aerospace 2024, 11(1), 99; https://doi.org/10.3390/aerospace11010099 - 22 Jan 2024

Viewed by 961

Abstract

In this study, we consider the problem of motion planning for urban air mobility applications to generate a minimal snap trajectory and trajectory that cost minimal time to reach a goal location in the presence of dynamic geo-fences and uncertainties in the urban [...] Read more.

In this study, we consider the problem of motion planning for urban air mobility applications to generate a minimal snap trajectory and trajectory that cost minimal time to reach a goal location in the presence of dynamic geo-fences and uncertainties in the urban airspace. We have developed two separate approaches for this problem because designing an algorithm individually for each objective yields better performance. The first approach that we propose is a decoupled method that includes designing a policy network based on a recurrent neural network for a reinforcement learning algorithm, and then combining an online trajectory generation algorithm to obtain the minimal snap trajectory for the vehicle. Additionally, in the second approach, we propose a coupled method using a generative adversarial imitation learning algorithm for training a recurrent-neural-network-based policy network and generating the time-optimized trajectory. The simulation results show that our approaches have a short computation time when compared to other algorithms with similar performance while guaranteeing sufficient exploration of the environment. In urban air mobility operations, our approaches are able to provide real-time on-the-fly motion re-planning for vehicles, and the re-planned trajectories maintain continuity for the executed trajectory. To the best of our knowledge, we propose one of the first approaches enabling one to perform an on-the-fly update of the final landing position and to optimize the path and trajectory in real-time while keeping explorations in the environment. Full article

(This article belongs to the Special Issue Integrated Airborne Urban Mobility: A Multidisciplinary View)

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24 pages, 352 KiB

Open AccessArticle

Integrating Life Cycle Assessment in Conceptual Aircraft Design: A Comparative Tool Analysis

by Kristina Mazur, Mischa Saleh and Mirko Hornung

Aerospace 2024, 11(1), 101; https://doi.org/10.3390/aerospace11010101 - 22 Jan 2024

Viewed by 1408

Abstract

Early and rapid environmental assessment of newly developed aircraft concepts is eminent in today’s climate debate. This can shorten the decision-making process and thus accelerate the entry into service of climate-friendly technologies. A holistic approach within the conceptual aircraft design is taken into [...] Read more.

Early and rapid environmental assessment of newly developed aircraft concepts is eminent in today’s climate debate. This can shorten the decision-making process and thus accelerate the entry into service of climate-friendly technologies. A holistic approach within the conceptual aircraft design is taken into consideration in terms of a life cycle assessment (LCA) to properly model and evaluate these concepts. To provide an understanding of how different LCA software affects the assessment, the goals of this study are to establish a baseline metrics definition for comparative evaluation and apply them to two tools. The first tool is an existing simplified derivative of openLCA, while the second, developed in this study, is an automated interface to the same software. The main finding is that researchers and practitioners must carefully consider the intended use of the tool. The simplified tool is suitable for training and teaching purposes and assessments on single score level. In contrast, an advanced tool is required in order to appropriately analyze the overall impact categories requiring high levels of LCA expertise, modeling, and time effort. Full article

(This article belongs to the Special Issue Aircraft Life Cycle Assessment)

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14 pages, 4752 KiB

Open AccessArticle

Measurement of the Convection Velocities in a Hypersonic Turbulent Boundary Layer Using Two-Point Cylindrical-Focused Laser Differential Interferometer

by Ranran Huang, Tao Xue and Jie Wu

Aerospace 2024, 11(1), 100; https://doi.org/10.3390/aerospace11010100 - 22 Jan 2024

Viewed by 864

Abstract

A two-point cylindrical-focused laser differential interferometer (2P-CFLDI) system and a conventional Z-type Schlieren were used to measure the hypersonic turbulent boundary layer on a flat plate at Mach number Ma = 6 and Reynolds number Re = 1.08 × 10⁶ m⁻¹ [...] Read more.

A two-point cylindrical-focused laser differential interferometer (2P-CFLDI) system and a conventional Z-type Schlieren were used to measure the hypersonic turbulent boundary layer on a flat plate at Mach number Ma = 6 and Reynolds number Re = 1.08 × 10⁶ m⁻¹. The boundary layer thickness at the measurement location and the noise radiation angle were obtained by post-processing the Schlieren image. The 2P-CFLDI data underwent cross-correlation analysis to calculate the mean convective velocities at different heights and compared with previous experimental and numerical results. The experimentally measured mean convective velocities agree with the trend of available DNS and experimental results. The mean convective velocity near the wall is significantly larger than the local mean velocity and is the main noise source region. Further filtering treatment shows that the convective velocity of the disturbed structure decreases gradually with the increase in the disturbance scale. The differences between convective velocities at different scales are significantly larger outside the boundary layer than inside the boundary layer, which is in agreement with the findings of the previous hot wire experiments. Near the wall, large-scale disturbances mainly determine the localized mean convective velocity, which are the main source of noise radiation for the hypersonic turbulent boundary layer. Full article

(This article belongs to the Special Issue Selected Papers from 10th International Conference on Vortex Flow Mechanics)

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0 pages, 1501 KiB

Open AccessArticle

Multi-Modal Life Cycle Assessment of Journeys by Aircraft, Train or Passenger Car

by R. J. Roosien, M. N. A. Lim, S. M. Petermeijer and W. F. Lammen

Aerospace 2024, 11(1), 98; https://doi.org/10.3390/aerospace11010098 - 20 Jan 2024

Viewed by 1171

Abstract

To reduce the carbon footprint of transport, policymakers are simultaneously stimulating cleaner vehicles and more sustainable mobility choices, such as a shift to rail for short-haul flights within Europe. The purpose of this study is to determine the climate impact of a journey [...] Read more.

To reduce the carbon footprint of transport, policymakers are simultaneously stimulating cleaner vehicles and more sustainable mobility choices, such as a shift to rail for short-haul flights within Europe. The purpose of this study is to determine the climate impact of a journey within Europe by aircraft, train or passenger car, and to better understand what factors drive this impact in order to make smarter and more sustainable fact-based mobility choices. The study consists of a life cycle inventory (LCI) and life cycle impact assessment (LCA) of greenhouse gas emissions of specific vehicles in five case study travel scenarios in Europe. The energy and resulting direct emissions (including non-CO₂) of the aircraft scenarios were calculated for the purpose of this study using the Mission Aircraft and Systems Simulation tool developed by the Royal Netherlands Aerospace Centre NLR. For other LCA phases and other modes of transport, the study relies on emission factors from public literature. A trip by train results in three to five times less emissions than a comparable trip by aircraft. In most scenarios, the passenger car with two people onboard emits significantly more than a train but slightly less than an aircraft. The study also shows what drives the climate impact of such a trip and how this is very different for different modes of transport. The study further highlights a lack of high-quality data, especially in the areas of indirect emissions and infrastructure, poor consistency among studies and a general under-documentation and lack of transparency regarding assumptions. Full article

(This article belongs to the Special Issue Aircraft Life Cycle Assessment)

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16 pages, 2213 KiB

Open AccessArticle

A Discontinuous Galerkin–Finite Element Method for the Nonlinear Unsteady Burning Rate Responses of Solid Propellants

by Zhuopu Wang, Kairui Yu and Yuanzhe Liu

Aerospace 2024, 11(1), 97; https://doi.org/10.3390/aerospace11010097 - 20 Jan 2024

Viewed by 828

Abstract

The unsteady combustion of solid propellants under oscillating environments is the key to understanding the combustion instability inside solid rocket motors. The discontinuous Galerkin–finite element method (DG-FEM) is introduced to provide an efficient yet flexible numerical platform to investigate the combustion dynamics of [...] Read more.

The unsteady combustion of solid propellants under oscillating environments is the key to understanding the combustion instability inside solid rocket motors. The discontinuous Galerkin–finite element method (DG-FEM) is introduced to provide an efficient yet flexible numerical platform to investigate the combustion dynamics of solid propellants. The algorithm is developed for the classical unsteady model, the Zel’dovich–Novozhilov model. It is then validated based on a special analytical solution. The DG-FEM algorithm is then compared with the classical spectral method based on Laguerre polynomials. It is shown that the DG-FEM works more efficiently than the traditional spectral method, providing a more accurate solution with a lower computational cost. Full article

(This article belongs to the Special Issue Understanding Combustion Instability: A Data-Driven Approach)

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20 pages, 4247 KiB

Open AccessArticle

A Deep Learning Approach for Trajectory Control of Tilt-Rotor UAV

by Javensius Sembiring, Rianto Adhy Sasongko, Eduardo I. Bastian, Bayu Aji Raditya and Rayhan Ekananto Limansubroto

Aerospace 2024, 11(1), 96; https://doi.org/10.3390/aerospace11010096 - 19 Jan 2024

Viewed by 1192

Abstract

This paper investigates the development of a deep learning-based flight control model for a tilt-rotor unmanned aerial vehicle, focusing on altitude, speed, and roll hold systems. Training data is gathered from the X-Plane flight simulator, employing a proportional–integral–derivative controller to enhance flight dynamics [...] Read more.

This paper investigates the development of a deep learning-based flight control model for a tilt-rotor unmanned aerial vehicle, focusing on altitude, speed, and roll hold systems. Training data is gathered from the X-Plane flight simulator, employing a proportional–integral–derivative controller to enhance flight dynamics and data quality. The model architecture, implemented within the TensorFlow framework, undergoes iterative tuning for optimal performance. Testing involved two scenarios: wind-free conditions and wind disturbances. In wind-free conditions, the model demonstrated excellent tracking performance, closely tracking the desired altitude. The model’s robustness is further evaluated by introducing wind disturbances. Interestingly, these disturbances do not significantly impact the model performance. This research has demonstrated data-driven flight control in a tilt-rotor unmanned aerial vehicle, offering improved adaptability and robustness compared to traditional methods. Future work may explore further flight modes, environmental complexities, and the utilization of real test flight data to enhance the model generalizability. Full article

(This article belongs to the Special Issue Artificial Intelligence in Drone Applications (2nd Edition))

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19 pages, 6507 KiB

Open AccessArticle

Development of a Novel Small-Scale Gust Generator Research Facility

by Zhenlong Wu, Tianyu Zhang, Yuan Gao and Huijun Tan

Aerospace 2024, 11(1), 95; https://doi.org/10.3390/aerospace11010095 - 19 Jan 2024

Viewed by 946

Abstract

In this paper, a novel small-scale gust generator research facility was designed and examined for generating Sears-type gusts. The design scheme, integration with the wind tunnel, experiment and validation of its capability are presented in detail. To help design the gust generator and [...] Read more.

In this paper, a novel small-scale gust generator research facility was designed and examined for generating Sears-type gusts. The design scheme, integration with the wind tunnel, experiment and validation of its capability are presented in detail. To help design the gust generator and validate the experimental results of the flow field characteristics generated by the developed gust generator, two numerical simulation methods, the field velocity method (FVM) and oscillating vane method (OVM), were utilized to detect the impacts of the geometrical parameters of the oscillating vanes and the downstream test model. The filtered experimental measurement results agree well with the numerical data, validating the capability of the developed gust generator to produce sinusoidal gusts. However, it should be noted that necessary measures are needed to prevent mechanical noise from interfering with the gusty flow field, which will be a focus of future research. Full article

(This article belongs to the Special Issue Gust Influences on Aerospace)

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21 pages, 12618 KiB

Open AccessArticle

Large-Eddy Simulations of a Hypersonic Re-Entry Capsule Coupled with the Supersonic Disk-Gap-Band Parachute

by Lakshmi Narayana Phaneendra Peri, Antonella Ingenito and Paolo Teofilatto

Aerospace 2024, 11(1), 94; https://doi.org/10.3390/aerospace11010094 - 19 Jan 2024

Viewed by 965

Abstract

The goal of this paper is to investigate the aerodynamic and aerothermodynamic behavior of the Schiaparelli capsule after the deployment of a supersonic disk-gap-band (DGB) parachute during its re-entry phase into the Martian atmosphere. The novelty of this work lies in the investigation [...] Read more.

The goal of this paper is to investigate the aerodynamic and aerothermodynamic behavior of the Schiaparelli capsule after the deployment of a supersonic disk-gap-band (DGB) parachute during its re-entry phase into the Martian atmosphere. The novelty of this work lies in the investigation by LES (large-eddy simulations) of the coupled interaction of the flow field generated behind the capsule and that in front of the flexible DGB parachute. These simulations are performed at an altitude of 10 km and a Mach number around 2, i.e., a regime in which large canopy-area oscillations are observed. LES results have shown a strong interaction between the bow shock, the recompression and expansion waves, high pressure, density and temperature gradients, heat flux towards the airstream and the body implying turbulence generation, ingestion, and amplification through the shock waves. Vortices released from the capsule at a frequency of about 52 Hz and 159 Hz, corresponding to Strouhal numbers of ~0.2 and 0.75, respectively, are the main factors responsible for the instabilities of the hypersonic re-entry capsule and the disk-gap-band parachute coupled system. The nonlinear turbulence flow field generated at the capsule back is amplified when passing the parachute bow shock, and this is responsible for the non-axisymmetric behavior around and behind the parachute that caused the uncontrolled capsule oscillations and the Schiaparelli mission failure. In fact, an LES of the parachute without the capsule, for the same conditions, show a completely axisymmetric field, varying in time, but axisymmetric. In order to avoid this turbulence amplification, dampening of the vortex shedding is critical. Different techniques have been already proposed for other applications. In the case of capsule re-entry, due to the high temperatures in front of the capsule behind the bow shock since air plasma is generated, damping of the vortex shedding could be achieved by means of magnetohydrodynamic (MHD) control. Full article

(This article belongs to the Special Issue High Speed Flows: Measurements & Simulations)

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21 pages, 18364 KiB

Open AccessArticle

Flow Structure behind Spanwise Pin Array in Supersonic Flow

by Philip A. Lax, Skye Elliott, Stanislav Gordeyev, Matthew R. Kemnetz and Sergey B. Leonov

Aerospace 2024, 11(1), 93; https://doi.org/10.3390/aerospace11010093 - 19 Jan 2024

Viewed by 862

Abstract

This work focused on the experimental characterization of a complex flow structure behind a cross-flow array of cylindrical pins installed on the wall of a supersonic duct. This geometry simulates several common gas dynamic configurations, such as a supersonic mixer, a turbulence-generating grid, [...] Read more.

This work focused on the experimental characterization of a complex flow structure behind a cross-flow array of cylindrical pins installed on the wall of a supersonic duct. This geometry simulates several common gas dynamic configurations, such as a supersonic mixer, a turbulence-generating grid, or, to some extent, a grid fin. In this work, the instrumentation employed is essentially non-intrusive, including spanwise integrating techniques such as (1) fast schlieren visualization and (2) Shack–Hartmann wavefront sensors; and planar techniques, namely (3) acetone Mie scattering and (4) acetone planar laser-induced fluorescence. An analysis of the data acquired by these complementary methods allowed the reconstruction of a three-dimensional portrait of supersonic flow interactions with a discrete pin array, including the shock wave structure, forefront separation zone, shock-induced separation zone, shear layer, and the mixing zone behind the pins. The main objective of this activity was to use various visualization techniques to acquire essential details of a complex compressible flow in a wide range of temporal–spatial scales. Particularly, a fine structure in the supersonic shear layer generated by the pin tips was captured by a Mie scattering technique. Based on the available publications, such structures have not been previously identified or discussed. Another potential outcome of this work is that the details revealed could be utilized for adequate code validation in numerical simulations. Full article

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

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55 pages, 6223 KiB

Open AccessReview

A Historical Survey of Corrective and Preventive Maintenance Models with Imperfect Inspections: Cases of Constant and Non-Constant Probabilities of Decision Making

by Vladimir Ulansky and Ahmed Raza

Aerospace 2024, 11(1), 92; https://doi.org/10.3390/aerospace11010092 - 18 Jan 2024

Viewed by 1771

Abstract

Maintenance strategies play a crucial role in ensuring the reliability and performance of complex systems. Imperfect inspections, characterized by the probabilities of false positives and false negatives, significantly impact the effectiveness of maintenance decisions. This survey explores maintenance models under imperfect inspections, characterized [...] Read more.

Maintenance strategies play a crucial role in ensuring the reliability and performance of complex systems. Imperfect inspections, characterized by the probabilities of false positives and false negatives, significantly impact the effectiveness of maintenance decisions. This survey explores maintenance models under imperfect inspections, characterized by constant and non-constant probabilities of false positives and false negatives. This study investigates various maintenance approaches, such as preventive and corrective maintenance, and evaluates their performance, considering the uncertainties introduced by imperfect inspections. By analyzing the existing literature and research findings, this survey provides valuable insights into the challenges and opportunities associated with maintenance decision making in the presence of inspection imperfections. The comparison between maintenance models with constant and non-constant probabilities of false positives and false negatives sheds light on the dynamic nature of these models, enabling a deeper understanding of their real-world applicability and effectiveness. This comprehensive overview is a valuable resource for researchers, practitioners, and decision makers involved in maintenance planning and optimization in diverse industrial sectors. Full article

(This article belongs to the Special Issue Recent Advances in Technologies for Aerospace Maintenance)

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20 pages, 8599 KiB

Open AccessArticle

Evaluation of the Multiaxial Fatigue Life of Electro-Mechanical Actuator for Aircraft Blade Pitch Control Based on Certification Standards

by Young-Cheol Kim, Dong-Hyeop Kim and Sang-Woo Kim

Aerospace 2024, 11(1), 91; https://doi.org/10.3390/aerospace11010091 - 18 Jan 2024

Viewed by 968

Abstract

To achieve the commercialization of electric vertical takeoff and landing (eVTOL) aircrafts, which have recently garnered attention as the next-generation means of transportation, objective certification based on rigorous procedures is essential. With the advancement of structural analysis technology, aircraft airworthiness standards recommend a [...] Read more.

To achieve the commercialization of electric vertical takeoff and landing (eVTOL) aircrafts, which have recently garnered attention as the next-generation means of transportation, objective certification based on rigorous procedures is essential. With the advancement of structural analysis technology, aircraft airworthiness standards recommend a combination of testing and analytical methods to demonstrate structural integrity. In this study, we propose analytical techniques for demonstrating the structural integrity of components for eVTOL aircrafts in accordance with airworthiness standards. We evaluated the static structural integrity and fatigue safety of an electro-mechanical actuator. Multibody dynamics analysis was performed to calculate the loads for application in finite element analysis. Subsequently, static analysis and fatigue analysis based on finite element analysis were conducted to calculate the safety margin and fatigue life of all key components. Therefore, we have confirmed the feasibility of utilizing analytical methods for the structural integrity assessment of aircraft components. We propose the utilization of the technique introduced in this study as one of the approaches for demonstrating compliance with airworthiness standards for eVTOL aircrafts through the application of analytical methods. Full article

(This article belongs to the Special Issue Electro-Mechanical Actuators for Safety-Critical Aerospace Applications (2nd Edition))

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22 pages, 9717 KiB

Open AccessArticle

Numerical Study on the Corner Separation Control for a Compressor Cascade via Bionic Herringbone Riblets

by Peng Zhang, Rixin Cheng and Yonghong Li

Aerospace 2024, 11(1), 90; https://doi.org/10.3390/aerospace11010090 - 18 Jan 2024

Viewed by 911

Abstract

Bionic herringbone riblets are applied to relieve the flow near the blade endwall in a linear compressor cascade under the incidence angle of −4° to 6° at a Reynolds number of 382,000. The herringbone riblets are placed at the endwall upstream of the [...] Read more.

Bionic herringbone riblets are applied to relieve the flow near the blade endwall in a linear compressor cascade under the incidence angle of −4° to 6° at a Reynolds number of 382,000. The herringbone riblets are placed at the endwall upstream of the blade, and the Reynolds-averaged Navier–Stokes simulations are performed to explore their effects on corner separation and the control mechanism. The results show that the herringbone riblets can effectively improve the corner separation over the stable operating range, and the control effect is affected by the riblet height and the yaw angle. The implementation of herringbone riblets with a height of only 0.08 boundary layer thickness and a yaw angle of 30 degrees can reduce the total pressure loss by up to 9.89% and increase the static pressure coefficient by 12.27%. Flow details indicate that small-scale vortices in the riblet channels can accumulate and form a high-intensity large-scale vortex close to the bottom of the boundary layer downstream. Compared with traditional vortex generators, the herringbone riblets induce a vortex closer to the wall due to their smaller size, which can reduce the damage of an induced vortex to the mainstream and enhance its control over the bottom of the boundary layer, thereby effectively reducing additional losses. The induced vortex enhances mixing and injects kinetic energy into the low-energy fluid, thus inhibiting the transverse migration of low-energy fluid in the endwall boundary layer, delaying the formation of the separating vortex, further suppressing the development of corner separation and improving the aerodynamic performance of the cascade. Full article

(This article belongs to the Special Issue Bioinspired Solutions for Flight)

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20 pages, 6258 KiB

Open AccessArticle

A Rapid Method of Integrated Aeropropulsive Analysis for the Conceptual Design of Airbreathing Hypersonic Aircraft

by Yalin Dai, Zhouwei Fan, Jian Xu, You He and Xiongqing Yu

Aerospace 2024, 11(1), 89; https://doi.org/10.3390/aerospace11010089 - 18 Jan 2024

Viewed by 998

Abstract

A special feature of airbreathing hypersonic aircraft is the complex coupling between aerodynamic and propulsive performances. This study presents a rapid analysis methodology for the integration of these two critical aspects in the conceptual design of airbreathing hypersonic aircraft. Parametric modeling is used [...] Read more.

A special feature of airbreathing hypersonic aircraft is the complex coupling between aerodynamic and propulsive performances. This study presents a rapid analysis methodology for the integration of these two critical aspects in the conceptual design of airbreathing hypersonic aircraft. Parametric modeling is used to generate a three-dimensional geometric model of an aircraft. The integrated aerodynamic and propulsive analysis is performed using a loosely coupled method. The aerodynamic analysis uses Euler equations to solve the inviscid aerodynamic forces, while the viscous forces are estimated using semi-empirical engineering methods. The propulsion system is modeled using hybrid one- and three-dimensional approaches. The inlet aerodynamic performance is simulated using three-dimensional simulation based on the Euler equations. The ramjet performance is estimated using a quasi-one-dimensional mathematical model. Nozzle simulation is performed using a one-dimensional plume method. The entire computational process is integrated and can be run automatically. The usefulness of the method is demonstrated through aerodynamic and propulsive performance evaluations in the conceptual design of a notional airbreathing hypersonic aircraft. Full article

(This article belongs to the Special Issue Advanced Aircraft Technology)

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22 pages, 674 KiB

Open AccessArticle

Deciding Technosignature Search Strategies: Multi-Criteria Fuzzy Logic to Find Extraterrestrial Intelligence

by Juan Miguel Sánchez-Lozano, Eloy Peña-Asensio and Hector Socas-Navarro

Aerospace 2024, 11(1), 88; https://doi.org/10.3390/aerospace11010088 - 18 Jan 2024

Viewed by 952

Abstract

This study presents the implementation of Multi-Criteria Decision-Making (MCDM) methodologies, particularly the fuzzy technique for order of preference by similarity to ideal solution (TOPSIS), in prioritizing technosignatures (TSs) for the search for extraterrestrial intelligence (SETI). By incorporating expert opinions and weighted criteria based [...] Read more.

This study presents the implementation of Multi-Criteria Decision-Making (MCDM) methodologies, particularly the fuzzy technique for order of preference by similarity to ideal solution (TOPSIS), in prioritizing technosignatures (TSs) for the search for extraterrestrial intelligence (SETI). By incorporating expert opinions and weighted criteria based on the established Axes of Merit, our analysis offers insights into the relative importance of various TSs. Notably, radio and optical communications are emphasized, in contrast to dark side illumination and starshades in transit. We introduce a new axis, Scale Sensitivity, designed to assess the variability of TS metrics. A sensitivity analysis confirms the robustness of our approach. Our findings, especially the highlighted significance of artifacts orbiting Earth, the Moon, or the Sun, indicate a need to broaden evaluative criteria within SETI research. This suggests an enhancement of the Axes of Merit, with a focus on addressing the plausibility of TSs. As the quest to resolve the profound question of our solitude in the cosmos continues, SETI efforts would benefit from exploring innovative prioritization methodologies that effectively quantify TS search strategies. Full article

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

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29 pages, 17196 KiB

Open AccessArticle

Stealth Aircraft Penetration Trajectory Planning in 3D Complex Dynamic Environment Based on Sparse A* Algorithm

by Jingxin Guan, Jun Huang, Lei Song and Xiaoqiang Lu

Aerospace 2024, 11(1), 87; https://doi.org/10.3390/aerospace11010087 - 18 Jan 2024

Viewed by 847

Abstract

To find a trajectory with low radar detection probability for stealth aircraft under the assumption of 2D space, performing a rapid turning maneuver is a useful way to reduce the radar detection probability of an aircraft by changing the azimuth angle rapidly to [...] Read more.

To find a trajectory with low radar detection probability for stealth aircraft under the assumption of 2D space, performing a rapid turning maneuver is a useful way to reduce the radar detection probability of an aircraft by changing the azimuth angle rapidly to reduce the time of high radar cross-section (RCS) exposure to radar. However, in real flight, not only does the azimuth angle to the radar change rapidly but the elevation angle also changes rapidly, and the change in the radar cross-section is also significant in this process. Based on this premise, this paper established a trajectory planning method based on the sparse A* algorithm in a 3D complex, dynamic environment, called the 3D sparse A* method, based on a log-normal radar model (the 3D-SASLRM method), which considers the RCS statistical uncertainty and the statistical characteristics of the radar signals. Simulations were performed in both simple and complex scenarios. It was concluded that the established 3D-SASLRM method can significantly reduce the radar detection probability. And the essence of reducing under the assumption of 3D space is also to reduce the time of high radar cross-section exposure to radar. Full article

(This article belongs to the Special Issue Advanced Aircraft Technology)

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20 pages, 3336 KiB

Open AccessArticle

Sustainability-Driven Design of Aircraft Composite Components

by Angelos Filippatos, Dionysios Markatos, Georgios Tzortzinis, Kaushik Abhyankar, Sonia Malefaki, Maik Gude and Spiros Pantelakis

Aerospace 2024, 11(1), 86; https://doi.org/10.3390/aerospace11010086 - 18 Jan 2024

Viewed by 1159

Abstract

The current prevailing trend in design across key sectors prioritizes eco-design, emphasizing considerations of environmental aspects in the design process. The present work aims to take a significant leap forward by proposing a design process where sustainability serves as the primary driving force. [...] Read more.

The current prevailing trend in design across key sectors prioritizes eco-design, emphasizing considerations of environmental aspects in the design process. The present work aims to take a significant leap forward by proposing a design process where sustainability serves as the primary driving force. In this context, sustainability is positioned as a fundamental component to be integrated into the initial stages of design, introducing innovative multidisciplinary criteria that redefine the design paradigm. Within this framework, sustainability is characterized using a comprehensive and quantifiable index encompassing technological, environmental, economic, and circular economy dimensions. To demonstrate the practical application of sustainability as the primary criterion in designing mechanical components, a parametrized finite element model of a composite plate is utilized, integrating both pristine and recycled fibers. Subsequently, a demonstrator derived from the aviation industry—specifically, a hat stiffener—is employed as a validation platform for the proposed methodology, ensuring alignment with the demonstrator’s specific requirements. Various representative trade-off scenarios are implemented to guide engineers’ decision-making during the conceptual design phase. Additionally, the robustness of the aforementioned methodology is thoroughly assessed concerning changes in the priority assigned to each sustainability criterion and its sensitivity to variations in the initial data. The significance of the proposed design methodology lies in its effectiveness in addressing the complex challenges presented by conflicting sustainability objectives. Furthermore, its adaptability positions it for potential application across various sectors, offering a transformative approach to sustainable engineering practices. Full article

(This article belongs to the Special Issue 13th EASN International Conference on Innovation in Aviation and Space for Opening New Horizons)

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21 pages, 12377 KiB

Open AccessArticle

Numerical Simulation of Heat Pipe Thermal Performance for Aerospace Cooling System Applications

by Roberto Scigliano, Valeria De Simone, Roberta Fusaro, Davide Ferretto and Nicole Viola

Aerospace 2024, 11(1), 85; https://doi.org/10.3390/aerospace11010085 - 17 Jan 2024

Viewed by 1107

Abstract

The design of integrated and highly efficient solutions for thermal management is a key capability for different aerospace products, ranging from civil aircraft using hydrogen on board to miniaturized satellites. In particular, this paper discloses a novel numerical tool for the design and [...] Read more.

The design of integrated and highly efficient solutions for thermal management is a key capability for different aerospace products, ranging from civil aircraft using hydrogen on board to miniaturized satellites. In particular, this paper discloses a novel numerical tool for the design and thermal performance assessment of heat pipes. To achieve this goal, a numerical Ansys Parametric Design Language code is set up to verify the effective subtractive heat flux guaranteed by the selected heat pipe arrangement. The methodology and related tool show their ability to provide good thermal performance estimates for different heat pipe designs and operating conditions. Specifically, the paper reports two very different test cases: (1) solid metal heat pipes to cool down the crotch leading-edge area of the air intake of a Mach 8 civil passenger aircraft, and (2) a copper-water heat pipe to cool down a Printed Circuit Board of a generic small LEO satellite. The successful application of the methodology and numerical code confirms the achievement of the ambitious goal of developing in-house tools to support heat pipe thermal performance prediction for the entire aerospace domain. Full article

(This article belongs to the Special Issue Heat Transfer and Cooling Systems for Aerospace Equipment)

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19 pages, 7830 KiB

Open AccessArticle

A Solar Thermal Steam Propulsion System Using Disassociated Steam for Interplanetary Exploration

by Leonard Vance, Agustin Espinoza, Jorge Martinez Dominguez, Salil Rabade, Gavin Liu and Jekan Thangavelautham

Aerospace 2024, 11(1), 84; https://doi.org/10.3390/aerospace11010084 - 17 Jan 2024

Viewed by 1130

Abstract

Sustainable space exploration will require using off-world resources for propellant generation. Using off-world-generated propellants significantly increases future missions’ range and payload capacity. Near Earth Objects (NEOs) contain a range of available resources, most notably water-ice and hydrated minerals. However, water-bearing regolith needs to [...] Read more.

Sustainable space exploration will require using off-world resources for propellant generation. Using off-world-generated propellants significantly increases future missions’ range and payload capacity. Near Earth Objects (NEOs) contain a range of available resources, most notably water-ice and hydrated minerals. However, water-bearing regolith needs to be excavated and the water extracted. Water is a compelling choice for fuel as it is readily available in interplanetary space and easily stored. In this paper, we propose using solar concentrators, which can efficiently convert incident sunlight into heat without the need for moving parts. When water is heated up to 4000 K, a value consistent with high-performance refractive materials, it experiences significant disassociation into H₂, O₂, OH, H, and O components, providing a path for adding considerable additional chemical energy per degree of temperature increase, and producing theoretical specific impulse (I_sp) values in the range of 643 s to 659 s. Full article

(This article belongs to the Special Issue Space Propulsion: Advances and Challenges (2nd Edition))

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18 pages, 3825 KiB

Open AccessArticle

Mixed-Integer Linear Programming Model for Scheduling Missions and Communications of Multiple Satellites

by Minkeon Lee, Seunghyeon Yu, Kybeom Kwon, Myungshin Lee, Junghyun Lee and Heungseob Kim

Aerospace 2024, 11(1), 83; https://doi.org/10.3390/aerospace11010083 - 16 Jan 2024

Viewed by 1153

Abstract

Satellites have been developed and operated for various purposes. The global satellite market is growing rapidly as the number of satellites and their mission diversity increase. Satellites revolve around the Earth to perform missions and communicate with ground stations repeatedly and sequentially. However, [...] Read more.

Satellites have been developed and operated for various purposes. The global satellite market is growing rapidly as the number of satellites and their mission diversity increase. Satellites revolve around the Earth to perform missions and communicate with ground stations repeatedly and sequentially. However, because satellites are orbiting the Earth, there is a limited time window for missions to a specific area and communication with ground stations. Thus, in an environment where multiple satellites and multiple ground stations (MS-MGs) are operated, scheduling missions and communications to maximize the utilization of satellites is a complex problem. For the MS-MG scheduling problem, this study proposes a mixed-integer linear programming (MILP) model to assign time windows for missions and communications with ground stations to individual satellites. The MILP model is based on the concept of a time-space network and includes constraints reflecting on the space mission environment of satellites. The objective function and constraints of the MILP model were validated through numerical experiments based on actual data from Korean satellites. Full article

(This article belongs to the Special Issue Heuristic Planning for Space Missions)

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21 pages, 6357 KiB

Open AccessArticle

Evaluation of the Success of Simulation of the Unmanned Aerial Vehicle Precision Landing Provided by a Newly Designed System for Precision Landing in a Mountainous Area

by Pavol Kurdel, Natália Gecejová, Marek Češkovič and Anna Yakovlieva

Aerospace 2024, 11(1), 82; https://doi.org/10.3390/aerospace11010082 - 16 Jan 2024

Viewed by 935

Abstract

Unmanned aerial vehicle technology is the most advanced and helpful in almost every area of interest in human work. These devices become autonomous and can fulfil a variety of tasks, from simple imaging and obtaining data to search and rescue operations. The most [...] Read more.

Unmanned aerial vehicle technology is the most advanced and helpful in almost every area of interest in human work. These devices become autonomous and can fulfil a variety of tasks, from simple imaging and obtaining data to search and rescue operations. The most challenging environment for search and rescue operations is the mountainous area. This article is devoted to the theoretical description and simulation tests of a prototype method of landing the light and the medium-weight UAVs used as supplementary devices for SAR (search and rescue) and HEMS (helicopter emergency medical service) in hard-to-reach mountainous terrains. The autonomous flight of a UAV in mountainous terrain has many specifics, and it is usually performed according to predetermined map points (pins) uploaded directly into the control software of the UAV. It is necessary to characterise each point flown on the chosen flight route line in advance and therefore to know its exact geographical coordinates (longitude, latitude and height of the point above the terrain), and the control system of UAV must react to the change in the weather and other conditions in real time. Usually, it is difficult to make this forecast with sufficient time in advance, mainly when UAVs are used as supplementary devices for the needs of HEMS or MRS (mountain rescue service). The most challenging phase is the final approach and landing of the UAV, especially if a loss of GNSS (global navigation satellite system) signal occurs, like in the determined area of the Little Cold Valley in the Slovak High Tatras—which is infamous for the widespread loss of GNSS signals or communication/controlling connection between the UAV and the pilot-operator at the operational station. To solve the loss of guidance, a new method for guiding and controlling the UAV in its final approach and landing in a determined area is tested. An alternative landing navigation system for UAVs in a specific mountainous environment—the authors’ designed frequency Doppler landing system (FDLS)—is briefly described but thoroughly tested with the help of artificial intelligence. An estimation of dynamic stability is used based on the time recording of the current position of the UAV, with the help of a frequency-modulated or amplitude-modulated signal based on the author’s prototype of a precision landing system designed for mountainous terrain. This solution could overcome the problems of GNSS signal loss. The presented research primarily evaluates the success of the simulation flights for the supplementary UAV. The success of navigating the UAV to land in the mountainous environment at an exact landing point using the navigation signals from the FDLS was evaluated at more than 95%. Full article

(This article belongs to the Special Issue UAV Path Planning and Navigation)

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12 pages, 4775 KiB

Open AccessArticle

Enhancing RDX Thermal Decomposition in Al@RDX Composites with Co Transition Metal Interfacial Layer

by Su-Lan Yang, Kan Xie, Jing Wang, Bingchen An, Bin Tian, Hongqi Nie, Jie-Yao Lyu and Qi-Long Yan

Aerospace 2024, 11(1), 81; https://doi.org/10.3390/aerospace11010081 - 16 Jan 2024

Viewed by 1218

Abstract

In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition [...] Read more.

In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition temperature of RDX in the DSC curve was decreased by 26.3 °C in the presence of Al/Co, which could be attributed to the nano-sized Co transition metal catalyzing the decomposition reaction of nitrogen oxides in RDX decomposition products. The decomposition peak temperature of RDX and the heat released by the thermal decomposition of RDX in the Al/Co@RDX composite were decreased by 26.3 °C and increased by 74.5 J·g⁻¹, respectively, in comparison with those of pure RDX. The types of major gaseous products released from Al/Co@RDX were found to be identical to those of pure RDX, encompassing N₂O, CH₂O, CO₂ and HCN. However, the concentrations of those gaseous products for Al/Co@RDX were higher than those observed for pure RDX, which may owe to the fact that the Al/Co composite can interact with the –CH₂ and –NO₂ within RDX molecules, which leads to the weakening of the C-N and N-N bonds. In addition, the decomposition of RDX in the Al/Co@RDX composite was observed as a one-step process with an apparent activation energy (E_a) of 115.6 kJ·cm⁻³. The decomposition mechanism of the RDX in the Al/Co@RDX composite was identified to follow the chain scission model (L2), whereas the two-step decomposition physical models observed for pure RDX were found to closely resemble the L2 and autocatalytic models. Full article

(This article belongs to the Special Issue Advanced Chemical Propulsion and Electric Propulsion)

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29 pages, 44669 KiB

Open AccessArticle

An Improved Approach for Reducing the Dimensionality of Wing Aerodynamic Optimization Considering Longitudinal Stability

by Boqian Ji, Jun Huang, Xiaoqiang Lu, Yacong Wu and Jingjiang Liu

Aerospace 2024, 11(1), 80; https://doi.org/10.3390/aerospace11010080 - 16 Jan 2024

Viewed by 891

Abstract

The wing aerodynamic shape optimization is a typical high-dimensional problem with numerous independent design variables. Researching methods to reduce the dimensionality of optimization from the perspective of aerodynamic characteristics is necessary. One traditional aerodynamic-based approach decouples the wing’s camber and thickness according to [...] Read more.

The wing aerodynamic shape optimization is a typical high-dimensional problem with numerous independent design variables. Researching methods to reduce the dimensionality of optimization from the perspective of aerodynamic characteristics is necessary. One traditional aerodynamic-based approach decouples the wing’s camber and thickness according to the thin airfoil theory, but it has limitations due to unclear application scope and effectiveness. This paper proposes an improved approach that determines the values of certain thickness variables based on a data-driven aerodynamic characteristics model before optimization, which considers longitudinal stability. By reducing the number of design variables, the dimensionality of optimization is decreased effectively. The derivation of the improved approach is accomplished through the design of experiments, parametric modeling, computational fluid dynamics, and sensitivity analysis. The effectiveness of the improved approach is validated by applying it to the aerodynamic optimization of an ONERA-M6 wing in subsonic flow based on the surrogate-based optimization algorithm. The results demonstrate that the improved approach significantly accelerates the optimization process while maintaining global effectiveness. Full article

(This article belongs to the Section Aeronautics)

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53 pages, 13613 KiB

Open AccessArticle

Flight-Data-Based High-Fidelity System Identification of DJI M600 Pro Hexacopter

by Péter Bauer and Mihály Nagy

Aerospace 2024, 11(1), 79; https://doi.org/10.3390/aerospace11010079 - 15 Jan 2024

Viewed by 1044

Abstract

Research and industrial application can require custom high-level controllers for industrial drones. Thus, this paper presents the high-fidelity dynamic and control model identification of the DJI M600 Pro hexacopter. This is a widely used multicopter in the research and industrial community due to [...] Read more.

Research and industrial application can require custom high-level controllers for industrial drones. Thus, this paper presents the high-fidelity dynamic and control model identification of the DJI M600 Pro hexacopter. This is a widely used multicopter in the research and industrial community due to its high payload capability and reliability. To support these communities, the focus of control model identification was on the exploration and implementation of DJI Onboard Software Development Kit (OSDK) functionalities, also including some unconventional special modes. Thus, the resulting model can be controlled with the same OSDK functionalities as the real drone, making control development and application time effective. First, the hardware and software structure of the additional DJI M600 onboard system are introduced. Then, the postulated dynamic and control system models are shown. Next, real flight test campaigns generating data for system identification are presented. Then, the mass and inertial properties are estimated for TB47S and TB48S battery sets and the custom Forerunner UAV payload. Dynamic system model identification includes the aerodynamic effects and considers hover, vertical, and horizontal forces together with static horizontal wind components and finally the rotational moments and dynamics. The control system components were identified following the structure of OSDK, including vertical, horizontal, and yaw loops. After identification, the model was validated and refined based on an unused flight test and software-in-the-loop simulation data. The simulation is provided by DJI and was also compared to real flight results. This comparison showed that the DJI simulation covers the dynamics of the real drone well, but it requires being connected to the drone and needs the controllers onboard to be implemented in advance, which limits applicability and increases development time. This was another motivation to introduce a standalone simulation in Matlab Simulink, which covers all the important modes of OSDK control and can be run solely in Matlab without any hardware support. The constructed model will be published for the benefit of the research and industrial community. Full article

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14 pages, 3811 KiB

Open AccessArticle

Prediction of Hourly Airport Operational Throughput with a Multi-Branch Convolutional Neural Network

by Huang Feng and Yu Zhang

Aerospace 2024, 11(1), 78; https://doi.org/10.3390/aerospace11010078 - 15 Jan 2024

Cited by 1 | Viewed by 970

Abstract

Extensive research in predicting annual passenger throughput has been conducted, aiming at providing decision support for airport construction, aircraft procurement, resource management, flight scheduling, etc. However, how airport operational throughput is affected by convective weather in the vicinity of the airport and how [...] Read more.

Extensive research in predicting annual passenger throughput has been conducted, aiming at providing decision support for airport construction, aircraft procurement, resource management, flight scheduling, etc. However, how airport operational throughput is affected by convective weather in the vicinity of the airport and how to predict short-term airport operational throughput have not been well studied. Convective weather near the airport could make arrivals miss their positions in the arrival stream and reduce airfield efficiency in terms of the utilization of runway capacities. This research leverages the learning-based method (MB-ResNet model) to predict airport hourly throughput and takes Hartsfield–Jackson Atlanta International Airport (ATL) as the case study to demonstrate the developed method. To indicate convective weather, this research uses Rapid Refresh model (RAP) data from the National Oceanic and Atmospheric Administration (NOAA). Although it is a comprehensive and powerful weather data product, RAP has not been widely used in aviation research. This study demonstrated that RAP data, after being carefully decoded, cleaned, and pre-processed, can play a significant role in explaining airfield efficiency variation. Applying machine learning/deep learning in air traffic management is an area worthy of the attention of aviation researchers. Such advanced artificial intelligence techniques can make use of big data from the aviation sector and improve the predictability of the national airspace system and, consequently, operational efficiency. The short-term airport operational throughput predicted in this study can be used by air traffic controllers and airport managers for the allocations of resources at airports to improve airport operations. Full article

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

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18 pages, 7275 KiB

Open AccessArticle

Comparative Study of Soft In-Plane and Stiff In-Plane Tiltrotor Blade Aerodynamics in Conversion Flight, Using CFD-CSD Coupling Approach

by Zhiyuan Hu, Peng Yu, Guohua Xu, Yongjie Shi, Feng Gu and Aijun Zou

Aerospace 2024, 11(1), 77; https://doi.org/10.3390/aerospace11010077 - 15 Jan 2024

Viewed by 836

Abstract

Tiltrotors permit aircrafts to operate vertically with lift, yet convert to ordinary forward flight with thrust. The challenge is to design a tiltrotor blade yielding maximum lift and thrust that converts smoothly without losing integrity or efficiency. The two types of blades, soft [...] Read more.

Tiltrotors permit aircrafts to operate vertically with lift, yet convert to ordinary forward flight with thrust. The challenge is to design a tiltrotor blade yielding maximum lift and thrust that converts smoothly without losing integrity or efficiency. The two types of blades, soft in-plane and stiff in-plane—the designation depending on the value of the blade’s natural lag frequency—exhibit different structural responses under the same flight conditions, differently affecting the aerodynamics of the blades, especially in the complex aerodynamic environment of conversion flight where the aerodynamic differences are significant. This phase of flight is not deeply researched, nor is the analytical coupling method much used. To study the influence of blade type on aerodynamics during conversion, models suitable for the conversion flight simulation are established for the application of coupled computational fluid dynamics and computational structural dynamics (CFD-CSD) methods. Each method is implemented with well-accepted techniques (the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations, the Reverse Overset Assembly Technique (ROAT), and the Timoshenko beam model. To improve the solving efficiency, a loose coupling strategy is used in constructing the two-way coupled model. The XV-15 tiltrotor is used for verification. The aeroelastic simulation of soft in-plane and stiff in-plane blades in conversion flight indicates an impactful role on the modal shapes, with a significant difference in the third flap modal shapes for the XV-15 rotor. However, the effect on aerodynamic performance is relatively small. In the first half of the flight conversion, the thrust of stiff in-plane blades is larger than that of soft in-plane blades, but in the last half, the influence of structural characteristics on aerodynamic performance is negligible and the thrust of the blades tends to be equal. Full article

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

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18 pages, 21772 KiB

Open AccessArticle

Flow Characteristics of Liquid Jet in Transverse Shear Crossflow

by Chi Zhang, Yaguo Lyu, Le Jiang and Zhenxia Liu

Aerospace 2024, 11(1), 76; https://doi.org/10.3390/aerospace11010076 - 13 Jan 2024

Viewed by 892

Abstract

The numerical simulation method was used to investigate the deflection and deformation process of a circular lubricating oil jet in transverse shear airflow. The numerical model was compared and validated against the experimental data. The physical parameters of Mobil jet Oil II were [...] Read more.

The numerical simulation method was used to investigate the deflection and deformation process of a circular lubricating oil jet in transverse shear airflow. The numerical model was compared and validated against the experimental data. The physical parameters of Mobil jet Oil II were utilized in this simulation with the nozzle diameter ranging from 0.5 to 2.5 mm, the maximum liquid/gas momentum ratios varying from 10.35 to 165.50, and the injection angle ranging from 0 to 30° in the opposite airflow direction. The results show that an increase in the nozzle diameter decreases the degree of jet deflection. The higher airflow velocity causes more fluctuations in the oil-jet trajectory, while the higher oil-injection velocity reduces fluctuations in the trajectory. The parabolic curve equations were used to derive the trajectory equations for the jet column’s pre-disintegration under both vertical incidence and a small angle of reverse airflow. The nozzle diameter and maximum oil/air momentum ratio were used to obtain a formula for the trajectory curve of the lubricating oil. Additionally, a formula for fitting the trajectory curve of oil injected in the opposite airflow direction regarding the injection angle was developed. Full article

(This article belongs to the Special Issue Jet Flows)

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51 pages, 6383 KiB

Open AccessArticle

Aerodynamic Instabilities in High-Speed Air Intakes and Their Role in Propulsion System Integration

by Aristia L. Philippou, Pavlos K. Zachos and David G. MacManus

Aerospace 2024, 11(1), 75; https://doi.org/10.3390/aerospace11010075 - 12 Jan 2024

Viewed by 1434

Abstract

High-speed air intakes often exhibit intricate flow patterns, with a specific type of flow instability known as ‘buzz’, characterized by unsteady shock oscillations at the inlet. This paper presents a comprehensive review of prior research, focused on unraveling the mechanisms that trigger buzz [...] Read more.

High-speed air intakes often exhibit intricate flow patterns, with a specific type of flow instability known as ‘buzz’, characterized by unsteady shock oscillations at the inlet. This paper presents a comprehensive review of prior research, focused on unraveling the mechanisms that trigger buzz and its implications for engine stability and performance. The literature survey delves into studies concerning complex-shaped diffusers and isolators, offering a thorough examination of flow aerodynamics in unstable environments. Furthermore, this paper provides an overview of contemporary techniques for mitigating flow instability through both active and passive flow control methods. These techniques encompass boundary layer bleeding, the application of vortex generators, and strategies involving mass injection and energy deposition. The study concludes by discussing future prospects in the domain of engine-intake aerodynamic compatibility. This work serves as a valuable resource for researchers and engineers striving to address and understand the complexities of high-speed air induction systems. Full article

(This article belongs to the Special Issue Vortex Flow Phenomena and Physics of Aerospace Engineering Applications)

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16 pages, 1251 KiB

Open AccessArticle

Autonomous Shape Decision Making of Morphing Aircraft with Improved Reinforcement Learning

by Weilai Jiang, Chenghong Zheng, Delong Hou, Kangsheng Wu and Yaonan Wang

Aerospace 2024, 11(1), 74; https://doi.org/10.3390/aerospace11010074 - 12 Jan 2024

Viewed by 876

Abstract

The autonomous shape decision-making problem of a morphing aircraft (MA) with a variable wingspan and sweep angle is studied in this paper. Considering the continuity of state space and action space, a more practical autonomous decision-making algorithm framework of MA is designed based [...] Read more.

The autonomous shape decision-making problem of a morphing aircraft (MA) with a variable wingspan and sweep angle is studied in this paper. Considering the continuity of state space and action space, a more practical autonomous decision-making algorithm framework of MA is designed based on the deep deterministic policy gradient (DDPG) algorithm. Furthermore, the DDPG with a task classifier (DDPGwTC) algorithm is proposed in combination with the long short-term memory (LSTM) network to improve the convergence speed of the algorithm. The simulation results show that the shape decision-making algorithm based on the DDPGwTC enables MA to adopt the optimal morphing strategy in different task environments with higher autonomy and environmental adaptability, which verifies the effectiveness of the proposed algorithm. Full article

(This article belongs to the Special Issue Cross-Domain Intelligent Flight Vehicle Design)

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16 pages, 2721 KiB

Open AccessArticle

Enhancing Planetary Exploration through Digital Twins: A Tool for Virtual Prototyping and HUMS Design

by Lucio Pinello, Lorenzo Brancato, Marco Giglio, Francesco Cadini and Giuseppe Francesco De Luca

Aerospace 2024, 11(1), 73; https://doi.org/10.3390/aerospace11010073 - 12 Jan 2024

Cited by 1 | Viewed by 1051

Abstract

In recent times, the demand for resilient space rovers has surged, which has been driven by the amplified exploration of celestial bodies such as the Moon and Mars. Recognising the limitations of direct human intervention in such environments, these rovers have gained a [...] Read more.

In recent times, the demand for resilient space rovers has surged, which has been driven by the amplified exploration of celestial bodies such as the Moon and Mars. Recognising the limitations of direct human intervention in such environments, these rovers have gained a great deal of importance. Our proposal introduces a digital twin for space exploration rovers that seamlessly integrates intricate geometric, kinematic, and dynamic models, along with sensor and control systems. It faithfully emulates genuine real-world scenarios, providing an authentic testing ground for rover prototypes and the development of damage detection algorithms. Its flexibility in replicating diverse terrains, environmental conditions, and operational scenarios significantly expedites rover development. The digital twin serves as a valuable tool in the perfecting of damage detection systems, allowing engineers to efficiently craft diagnostic algorithms. This innovative approach not only conserves valuable resources but also ensures the robustness of space mission systems, thus enhancing the overall success and safety of planetary exploration endeavours. Full article

(This article belongs to the Special Issue Space Systems Preliminary Design)

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21 pages, 15263 KiB

Open AccessArticle

Evaluation of Mixing Effect on Coupled Heat Release and Transfer Performance of a Novel Segregated Solid Rocket Motor

by Shuyuan Liu, Yu Zhang, Limin Wang, Zhengchun Chen and Songqi Hu

Aerospace 2024, 11(1), 72; https://doi.org/10.3390/aerospace11010072 - 12 Jan 2024

Viewed by 950

Abstract

The effect of mixing on coupled heat release and transfer performance of a novel segregated solid motor is numerically evaluated with a transient two-dimensional combustion model. The results show that vortex structures are formed and evolved in the combustion chamber. Quantitative calculation of [...] Read more.

The effect of mixing on coupled heat release and transfer performance of a novel segregated solid motor is numerically evaluated with a transient two-dimensional combustion model. The results show that vortex structures are formed and evolved in the combustion chamber. Quantitative calculation of the mixing effect shows the inhomogeneous distribution of oxidant and fuel species. The well-mixing area is located in a narrow belt-like coupled combustion region near the burning surface of the propellant. Heat transfer coefficient decreases greatly due to lower combustion reaction rate and enlarged flow channel area. Heat transfer coefficients near the two ends of the propellant grain are higher than other parts due to the influence of vortex mixing. Raising the inlet mass flow rate leads to enhanced mixing and heat transfer, which results in a lower temperature and regression rate of the propellant with combustion time. Temperature and oxidation rates of H₂ and CO are unevenly distributed in the boundary layer of coupled combustion. Increasing the mass flux of inlet oxidizer gas leads to a higher combustion heat release rate. Therefore, the gas-phase temperature increases significantly. The heat release rate reaches the maximum near the ends of the propellant grain, where vortex mixing strengthens the coupled combustion process in the motor. Full article

(This article belongs to the Special Issue Space Propulsion: Advances and Challenges)

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