Aerospace

17 pages, 6366 KiB

Open AccessArticle

Observability-Driven Path Planning Design for Securing Three-Dimensional Navigation Performance of LiDAR SLAM

by Donggyun Kim, Byungjin Lee and Sangkyung Sung

Aerospace 2023, 10(5), 492; https://doi.org/10.3390/aerospace10050492 - 22 May 2023

Cited by 4 | Viewed by 1633

This paper presents an efficient method for securing navigation performance by suppressing divergence risk of LiDAR SLAM through a newly proposed geometric observability analysis in a three-dimensional point cloud map. For this, observability characteristics are introduced that quantitatively evaluate the quality of the [...] Read more.

This paper presents an efficient method for securing navigation performance by suppressing divergence risk of LiDAR SLAM through a newly proposed geometric observability analysis in a three-dimensional point cloud map. For this, observability characteristics are introduced that quantitatively evaluate the quality of the geometric distribution of the features. To be specific, this study adapts a 3D geometric observability matrix and the associated condition number for developing numerical benefit. In an extensive application, we implemented path planning in which the enhanced SLAM performs smoothly based on the proposed method. Finally, to validate the performance of the proposed algorithm, a simulation study was performed using the high-fidelity Gazebo simulator, where the path planning strategy of a drone depending on navigation quality is demonstrated. Additionally, an indoor autonomous vehicle experimental result is presented to support the effectiveness of the proposed algorithm. Full article

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21 pages, 7344 KiB

Open AccessArticle

A New Approach for Deviation Modeling in Compressors: Sensitivity-Correlated Principal Component Analysis

by Mingzhi Li, Xianjun Yu, Dejun Meng, Guangfeng An and Baojie Liu

Aerospace 2023, 10(5), 491; https://doi.org/10.3390/aerospace10050491 - 22 May 2023

Cited by 3 | Viewed by 1552

Abstract

Studies on the geometry variation-related compressor uncertainty quantification (UQ) have often used dimension reduction methods, such as the principal component analysis (PCA), for the modeling of deviations. However, in the PCA method, the main eigenmodes were determined based only on the statistical behavior [...] Read more.

Studies on the geometry variation-related compressor uncertainty quantification (UQ) have often used dimension reduction methods, such as the principal component analysis (PCA), for the modeling of deviations. However, in the PCA method, the main eigenmodes were determined based only on the statistical behavior of geometry variations. While this process can cause some missing modes with a small eigenvalue, it is much more sensitive to blade aerodynamic performances, and thereby reducing the reliability of the UQ analysis. Hence, a novel geometry variation modeling method, named sensitivity-correlated principal component analysis (SCPCA), has been proposed. In addition, by means of the blade sensitivity analysis, the weighting factors for each eigenmode were determined and then used to modify the process of the PCA. As a result, by considering the covariance of geometry variations and the performance sensitivity, the main eigenmodes could be determined and used to reconstruct the blade samples in the UQ analysis. With 98 profile samples measured at the midspan of a high-pressure compressor rotor blade, both the PCA and SCPCA methods were employed for the UQ analysis. The results showed that, compared to the PCA method, the SCPCA method provided a more accurate reconstruction of sensitive deviations, leading to an 11.8% improvement in evaluating the scatter of the positive incidence range, while also maintaining the accuracy of the uncertainty assessment for other performances. Full article

(This article belongs to the Special Issue Aerodynamic Shape Optimization)

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25 pages, 1000 KiB

Open AccessArticle

A Virtual Simulation-Pilot Agent for Training of Air Traffic Controllers

by Juan Zuluaga-Gomez, Amrutha Prasad, Iuliia Nigmatulina, Petr Motlicek and Matthias Kleinert

Aerospace 2023, 10(5), 490; https://doi.org/10.3390/aerospace10050490 - 22 May 2023

Cited by 13 | Viewed by 4052

Abstract

In this paper we propose a novel virtual simulation-pilot engine for speeding up air traffic controller (ATCo) training by integrating different state-of-the-art artificial intelligence (AI)-based tools. The virtual simulation-pilot engine receives spoken communications from ATCo trainees, and it performs automatic speech recognition and [...] Read more.

In this paper we propose a novel virtual simulation-pilot engine for speeding up air traffic controller (ATCo) training by integrating different state-of-the-art artificial intelligence (AI)-based tools. The virtual simulation-pilot engine receives spoken communications from ATCo trainees, and it performs automatic speech recognition and understanding. Thus, it goes beyond only transcribing the communication and can also understand its meaning. The output is subsequently sent to a response generator system, which resembles the spoken read-back that pilots give to the ATCo trainees. The overall pipeline is composed of the following submodules: (i) an automatic speech recognition (ASR) system that transforms audio into a sequence of words; (ii) a high-level air traffic control (ATC)-related entity parser that understands the transcribed voice communication; and (iii) a text-to-speech submodule that generates a spoken utterance that resembles a pilot based on the situation of the dialogue. Our system employs state-of-the-art AI-based tools such as Wav2Vec 2.0, Conformer, BERT and Tacotron models. To the best of our knowledge, this is the first work fully based on open-source ATC resources and AI tools. In addition, we develop a robust and modular system with optional submodules that can enhance the system’s performance by incorporating real-time surveillance data, metadata related to exercises (such as sectors or runways), or even a deliberate read-back error to train ATCo trainees to identify them. Our ASR system can reach as low as 5.5% and 15.9% absolute word error rates (WER) on high- and low-quality ATC audio. We also demonstrate that adding surveillance data into the ASR can yield a callsign detection accuracy of more than 96%. Full article

(This article belongs to the Special Issue Automatic Speech Recognition and Understanding in Air Traffic Management)

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17 pages, 14502 KiB

Open AccessArticle

The Study of Selected Aspects of the Suborbital Vehicle Return Flight Trajectory

by Agnieszka Kwiek, Marcin Figat and Tomasz Goetzendorf-Grabowski

Aerospace 2023, 10(5), 489; https://doi.org/10.3390/aerospace10050489 - 22 May 2023

Cited by 3 | Viewed by 1798

Abstract

The article presents the results of preliminary studies of the parameters of the return flight trajectory of a rocket plane for suborbital tourist flights into space. The rocket plane is designed as a tailless vehicle and has an unconventional arrangement of control surfaces: [...] Read more.

The article presents the results of preliminary studies of the parameters of the return flight trajectory of a rocket plane for suborbital tourist flights into space. The rocket plane is designed as a tailless vehicle and has an unconventional arrangement of control surfaces: elevons and side plates that can rotate. The main aim of the research presented in this paper is to investigate the dynamic stability of the rocket plane and the response to control in the return suborbital flight. The secondary objective is to study the behavior of the rocket plane with respect to the initial state of the return flight. The key parameters taken into account in this study are the Mach number and G-load. Moreover, a study of the trim condition, dynamic stability and response to control of a rocket plane in the low part of the stratosphere is presented. The tests were carried out using a numerical simulation of the flight of a rocket plane. Dynamic stability was determined on the basis of time history analysis, and the results were compared with the results obtained by solving the eigenvalues problem. The results revealed that the rocket plane should be equipped with a Stability Augmentation System to improve short period damping at supersonic speeds at moderate altitudes. It can also be concluded that the maximum load G and Ma do not occur at the same height of flight. In terms of the effectiveness of the control surfaces, they start working at an altitude of 55 km. Due to the speed regime, the obtained results can be useful in the design of such objects as rocket planes, highly maneuverable and supersonic aircraft. Full article

(This article belongs to the Section Aeronautics)

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10 pages, 2319 KiB

Open AccessArticle

Three-Dimensional Drone Exploration with Saliency Prediction in Real Unknown Environments

by Ming-Ru Xie, Shing-Yun Jung and Kuan-Wen Chen

Aerospace 2023, 10(5), 488; https://doi.org/10.3390/aerospace10050488 - 22 May 2023

Cited by 1 | Viewed by 1811

Abstract

In this paper, we propose a three-dimensional autonomous drone exploration system (ADES) with a lightweight and low-latency saliency prediction model to explore unknown environments. Several studies have applied saliency prediction in drone exploration. However, these studies are not sufficiently mature. For example, the [...] Read more.

In this paper, we propose a three-dimensional autonomous drone exploration system (ADES) with a lightweight and low-latency saliency prediction model to explore unknown environments. Several studies have applied saliency prediction in drone exploration. However, these studies are not sufficiently mature. For example, the computational complexity and the size of the developed prediction models have not been considered. In addition, some studies have only proposed saliency prediction models without actually applying them to drones. The ADES system proposed in this paper has a small and fast saliency prediction model and uses a novel drone exploration approach based on visual-inertial odometry to solve the practical problems encountered during drone exploration, such as collisions with and the repeated exploration of salient objects. The proposed ADES system performs comparably to the state-of-the-art, multiple-discontinuous-image saliency prediction network TA-MSNet and enables drones to explore unknown environments with high efficiency. Full article

(This article belongs to the Special Issue Applications of Drones (Volume II))

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30 pages, 12016 KiB

Open AccessArticle

Path Planning of an Unmanned Combat Aerial Vehicle with an Extended-Treatment-Approach-Based Immune Plasma Algorithm

by Selcuk Aslan and Tugrul Oktay

Aerospace 2023, 10(5), 487; https://doi.org/10.3390/aerospace10050487 - 21 May 2023

Cited by 4 | Viewed by 2008

Abstract

The increasing usage of unmanned aerial vehicles (UAVs) and their variants carrying complex weapon systems, known as unmanned combat aerial vehicles (UCAVs), has triggered a global revolution in complex military and commercial operations and has attracted researcher attention from different engineering disciplines in [...] Read more.

The increasing usage of unmanned aerial vehicles (UAVs) and their variants carrying complex weapon systems, known as unmanned combat aerial vehicles (UCAVs), has triggered a global revolution in complex military and commercial operations and has attracted researcher attention from different engineering disciplines in order to solve challenging problems regarding these modern vehicles. Path planning is a challenging problem for UAV and UCAV systems that requires the calculation of an optimal solution by considering enemy threats, total flight length, fuel or battery consumption, and some kinematic properties such as turning or climbing angles. In this study, the immune plasma (IP or IPA) algorithm, one of the most recent nature-inspired intelligent optimization methods, was modified by changing the default plasma transfer operations with a newly proposed technique called the extended treatment approach; extended IPA (ExtIPA) was then introduced as a path planner. To analyze the solving capabilities of the ExtIPA, 16 cases from five battlefield scenarios were tested by assigning different values to the algorithm-specific control parameters. The paths calculated with ExtIPA were compared with the paths found by planners on the basis of other intelligent optimization techniques. Comparative studies between ExtIPA and other techniques allowed for stating that the extended treatment approach significantly contributes to both the convergence speed and qualities of the obtained solutions and helps ExtIPA in performing better than its rivals in most cases. Full article

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

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21 pages, 7715 KiB

Open AccessArticle

Study on Optimization Design of Airfoil Transonic Buffet with Reinforcement Learning Method

by Hao Chen, Chuanqiang Gao, Jifei Wu, Kai Ren and Weiwei Zhang

Aerospace 2023, 10(5), 486; https://doi.org/10.3390/aerospace10050486 - 20 May 2023

Cited by 2 | Viewed by 2513

Abstract

Transonic buffet is a phenomenon of large self-excited shock oscillations caused by shock wave-boundary layer interaction, which is one of the common flow instability problems in aeronautical engineering. This phenomenon involves unsteady flow, which makes optimal design more difficult. In this paper, aerodynamic [...] Read more.

Transonic buffet is a phenomenon of large self-excited shock oscillations caused by shock wave-boundary layer interaction, which is one of the common flow instability problems in aeronautical engineering. This phenomenon involves unsteady flow, which makes optimal design more difficult. In this paper, aerodynamic shape optimization design is combined with reinforcement learning to address the problem of transonic buffet. Using the deep deterministic policy gradient (DDPG) algorithm, a reinforcement learning-based design framework for airfoil shape optimization was constructed to achieve effective suppression of transonic buffet. The aerodynamic characteristics of the airfoil were calculated by the computational fluid dynamics (CFD) method. After optimization, the buffet onset angles of attack of the airfoils NACA0012 and RAE2822 were improved by 2° and 1.2° respectively, and the lift-drag ratios improved by 83.5% and 30% respectively. Summarizing and verifying the optimization results, three general conclusions can be drawn to improve the buffet performance: (1) narrowing of the leading edge of the airfoil; (2) situating the maximum thickness position at approximately 0.4 times the chord length; (3) increasing the thickness of the trailing edge within a certain range. This paper established a reinforcement learning-based unsteady optimal design method that enables the optimization of unsteady problems, including buffet. Full article

(This article belongs to the Special Issue Aerodynamic Design with Machine Learning)

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17 pages, 8548 KiB

Open AccessArticle

A Flexible Dynamic Reliability Simulation Approach for Predicting the Lifetime Consumption of Extravehicular Spacesuits during Uncertain Extravehicular Activities

by Yuehang Sun, Yun-Ze Li and Man Yuan

Aerospace 2023, 10(5), 485; https://doi.org/10.3390/aerospace10050485 - 20 May 2023

Viewed by 1555

Abstract

The special use environment and uncertainty of extravehicular activities (EVAs) make it difficult to predict the lifetime consumption of extravehicular spacesuits in the traditional way. This paper presents a flexible reliability dynamic simulation model to predict the life loss of extravehicular spacesuits. Based [...] Read more.

The special use environment and uncertainty of extravehicular activities (EVAs) make it difficult to predict the lifetime consumption of extravehicular spacesuits in the traditional way. This paper presents a flexible reliability dynamic simulation model to predict the life loss of extravehicular spacesuits. Based on the images of traditional reliability change curves, new life assessment parameters, based on geometric analysis, are proposed as indicators of spacesuit life loss. Multiple influence factors are used to correct the spacesuit failure rate. The results of the study show that mission intensity is the main factor affecting the health status of the spacesuit, and the higher the mission intensity, the higher the failure rate. Additionally, the more frequently the spacesuit is used, the more times it is available, however, the overall service time will decrease. Concentrating on the mission at an early stage would lead to a significant and irreversible loss of life. Reliability is higher when more intense work is scheduled later in the EVA. Therefore, it is important to rationalize the mission duration, frequency, and work intensity of spacesuits. These reliability models predict the health status of the spacesuit and assist in optimizing the scheduling of EVA. Full article

(This article belongs to the Topic Perspectives in Fault Diagnosis and Fault Tolerant Control)

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16 pages, 5238 KiB

Open AccessArticle

Buckling Analysis and Structure Improvement for the Afterburner Cylinder of an Aero-Engine

by Xiaoxia Zheng, Yu Zou, Bohan He, Jixin Xiang, Zhiqiang Li and Qiao Yang

Aerospace 2023, 10(5), 484; https://doi.org/10.3390/aerospace10050484 - 20 May 2023

Cited by 1 | Viewed by 1480

Abstract

The buckling failure of the afterburner cylinder is a serious safety concern for aero-engines. To tackle this issue, the buckling simulation analysis of the afterburner cylinder was carried out by using finite element method (FEM) software to obtain the buckling mode and critical [...] Read more.

The buckling failure of the afterburner cylinder is a serious safety concern for aero-engines. To tackle this issue, the buckling simulation analysis of the afterburner cylinder was carried out by using finite element method (FEM) software to obtain the buckling mode and critical buckling loads. It was found that the afterburner cylinder was susceptible to buckling when subjected to differential pressure or the compressive force of the rear flange. Buckling would occur when the differential pressure reached 0.4 times the atmospheric pressure or when the axial compressive force on the rear flange reached 222.8 kN. Buckling was also found at the front of the cylinder under the auxiliary mount load. Additionally, under various loads on the rear flange, buckling occurred in the rear section, with the buckling mode being closely related to the load characteristics. Based on the simulation results and structural design requirements, two structural improvements were proposed, including the wall-thickening scheme and the grid reinforcement scheme. FEM simulation analysis results showed that both schemes would improve the rigidity and stability of the afterburner cylinder. For the 0.3 mm increase in the wall thickness scheme, the critical buckling load increased by 17.86% to 66.4%; for the grid reinforcement scheme, the critical buckling load increased by 169% to 619%. Therefore, the grid reinforcement scheme had a stronger anti-buckling ability and was deemed the optimal solution. The findings of this paper could provide technical support for the structural design of large-sized and thin-walled components of aero-engines. Full article

(This article belongs to the Topic Advanced Technologies and Methods in the Energy System)

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20 pages, 5339 KiB

Open AccessArticle

Using Catalyst Mass-Based Clustering Analysis to Identify Adverse Events during Approach

by Zhiwei Xiang, Zhenxing Gao, Jiming Liu and Yangyang Zhang

Aerospace 2023, 10(5), 483; https://doi.org/10.3390/aerospace10050483 - 19 May 2023

Viewed by 1322

Abstract

Discovering and mitigating potential risks in advance is essential for preventing aviation accidents on routine flights. Although anomaly detection-based explanation techniques have successfully uncovered potential risks for proactive flight safety management, explaining group-scale precursors using these methods is challenging due to the assumption [...] Read more.

Discovering and mitigating potential risks in advance is essential for preventing aviation accidents on routine flights. Although anomaly detection-based explanation techniques have successfully uncovered potential risks for proactive flight safety management, explaining group-scale precursors using these methods is challenging due to the assumption that risky flights are significantly fewer in number than normal flights, as well as the reliance on non-domain knowledge for hyperparameter adjustment. To characterize the group-scale precursors more accurately, we propose a novel technique called Catalyst Mass-Based Clustering Analysis (CMCA), which employs a composite entropy-energy dissipation index during approach to evaluate the energy management performance. On this basis, an optimization objective is constructed to identify clusters exhibiting significant energy management differences during the approach phase. We successfully identify group-scale precursors with energy management issues by applying CMCA to a combination of minority-labeled and majority-unlabeled flights. Comparative experiments show that these precursors have energy levels that deviate from normal flights by 5.83% and 10.93%, respectively, 1000 ft above touchdown, demonstrating the effectiveness of our method. The analysis suggests that poor energy management awareness on the part of pilots could be responsible for these group-scale precursors. Notably, the results obtained using CMCA are comprehensible for Subject Matter Experts, making the method a valuable tool for proactive flight safety management. Full article

(This article belongs to the Section Aeronautics)

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34 pages, 8147 KiB

Open AccessArticle

Performance and Weight Parameters Calculation for Hydrogen- and Battery-Powered Aircraft Concepts

by Michal Janovec, Viktor Babčan, Branislav Kandera, Kristína Šajbanová, Filip Škultéty and Ľuboš Halvoň

Aerospace 2023, 10(5), 482; https://doi.org/10.3390/aerospace10050482 - 18 May 2023

Cited by 2 | Viewed by 2907

Abstract

This article describes the creation of a program that would be useful for calculating mathematical models in order to estimate the weight of aircraft components. Using several parameters, it can calculate other parameters of civil transport aircraft powered by batteries or fuel cells. [...] Read more.

This article describes the creation of a program that would be useful for calculating mathematical models in order to estimate the weight of aircraft components. Using several parameters, it can calculate other parameters of civil transport aircraft powered by batteries or fuel cells. The main goals of this research were to add the missing dimensions and parameters to the aircraft database, create a simple but effective program for creating mathematical models, and use this program to find technological barriers to battery or hydrogen fuel-cell-powered aircraft concepts. The article introduces the reader to the problem of calculating OEW (operating empty weight) using Breguet–Leduc equations. A calculation model was created for OEW calculation. The result of this work is the verification of a mathematical model for battery-powered electric aircraft of the CS-23 (European Aviation Safety Agency Certification Specification for Normal, Utility, Aerobatic, and Commuter Category Aeroplanes) category by comparing the program’s outputs with real aircraft. Subsequently, the results of mathematical models are shown in graphs that specify the space of possible concepts of aircraft powered by batteries or fuel cells, sorted by the number of passengers and the range of the aircraft, delimited by two or three criteria, respectively. Full article

(This article belongs to the Topic Theoretical, Numerical and Experimental Studies on Clean Energy and Combustion)

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19 pages, 650 KiB

Open AccessArticle

Aeroelastic Stability of an Aerial Refueling Hose–Drogue System with Aerodynamic Grid Fins

by Keyvan Salehi Paniagua, Pablo García-Fogeda and Félix Arévalo

Aerospace 2023, 10(5), 481; https://doi.org/10.3390/aerospace10050481 - 18 May 2023

Cited by 2 | Viewed by 1460

Abstract

In this work, the aeroelastic stability of an aerial refueling system is investigated. The system is formed by a classical hose and drogue, and the novelty of our work is the inclusion of a grid fin configuration to improve its stability. The unsteady [...] Read more.

In this work, the aeroelastic stability of an aerial refueling system is investigated. The system is formed by a classical hose and drogue, and the novelty of our work is the inclusion of a grid fin configuration to improve its stability. The unsteady aerodynamic forces on the grid fins are determined using the concept of a unit grid fin (UGF). For each UGF, the unsteady aerodynamic forces are computed using the Doublet-Lattice Method, and the forces on the complete grid fins are calculated using interfering factors obtained from wind tunnel measurements for the steady case. The static equilibrium position of the system influences the linearized perturbed unsteady motion of the ensemble. This effect, together with the phase lag angle introduced to account for the unsteady aerodynamic forces in the hose, makes the flutter computation of the complete system a non-typical one. The results show that, by adding the grid fins, the stability of the refueling system is improved, delaying or annulling flutter occurrence. Full article

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10 pages, 4169 KiB

Open AccessArticle

Rotating Machinery State Recognition Based on Mel-Spectrum and Transfer Learning

by Fan Li, Zixiao Lu, Junyue Tang, Weiwei Zhang, Yahui Tian, Zhongyu Cui, Fei Jiang, Honglang Li and Shengyuan Jiang

Aerospace 2023, 10(5), 480; https://doi.org/10.3390/aerospace10050480 - 18 May 2023

Cited by 2 | Viewed by 1523

Abstract

During drilling into the soil, the rotating mechanical structure will be affected by soil particles and external disturbances, affecting the health of the rotating mechanical structure. Therefore, real-time monitoring of the operational status of rotating mechanical structures is of great significance. This paper [...] Read more.

During drilling into the soil, the rotating mechanical structure will be affected by soil particles and external disturbances, affecting the health of the rotating mechanical structure. Therefore, real-time monitoring of the operational status of rotating mechanical structures is of great significance. This paper proposes a working state recognition method based on Mel-spectrum and transfer learning, which uses the mechanical vibration signal’s time domain and frequency domain information to identify the mechanical structure’s working state. Firstly, we cut the signal at window length, and then the Mel-spectrum of the truncated signal is obtained through the Fourier transform and Mel-scale filter bank. Finally, we adopted the method of transfer learning. The pre-trained model VGG16 is adjusted to extract and classify the features of the Mel-spectrum. Experimental results show that the framework maintains an accuracy of more than 90% for vibration signals under minor window conditions, which verifies the real-time reliability of the method. Full article

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

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27 pages, 10331 KiB

Open AccessArticle

Numerical Study on Asteroid Deflection by Penetrating Explosion Based on Single-Material ALE Method and FE-SPH Adaptive Method

by Pengfei Han, Qiguang He, Xiaowei Chen and He Lv

Aerospace 2023, 10(5), 479; https://doi.org/10.3390/aerospace10050479 - 18 May 2023

Cited by 4 | Viewed by 2458

Abstract

An asteroid impact can potentially destroy life on this planet. Therefore, asteroids should be prevented from impacting the Earth to impede severe disasters. Nuclear explosions are currently the only option to prevent an incoming asteroid impact when the asteroid is large or the [...] Read more.

An asteroid impact can potentially destroy life on this planet. Therefore, asteroids should be prevented from impacting the Earth to impede severe disasters. Nuclear explosions are currently the only option to prevent an incoming asteroid impact when the asteroid is large or the warning time is short. However, asteroids exist in an absolute vacuum, where the explosion energy propagation mechanism differs from that in an air environment. It is difficult to describe this process using standard numerical simulation methods. In this study, we used the single-material arbitrary Lagrangian–Eulerian (ALE) method and the finite element-smoothed particle hydrodynamics (FE-SPH) adaptive method to simulate the process of deflecting hazardous asteroids using penetrating explosions. The single-material ALE method can demonstrate the expansion process of explosion products and energy coupling in absolute vacuum. The FE-SPH adaptive method can transform failed elements into SPH particles during the simulation, avoiding system mass loss, energy loss, and element distortion. We analyzed the shock initiation and explosion damage process and obtained an effective simulation of the damage evolution, stress propagation, and fragment distribution of the asteroid. In addition, we decoupled the penetrating explosion into two processes: kinetic impact and static explosion at the impact crater. The corresponding asteroid damage modes, velocity changes, and fragmentation degrees were simulated and compared. Finally, the high efficiency of the nuclear explosion was confirmed by comparing the contribution rates of the kinetic impact and nuclear explosion in the penetrating explosion scheme. Full article

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

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29 pages, 13557 KiB

Open AccessArticle

Structural Scalability Preliminary Studies for the Next Generation Civil Tiltrotor Composite Wing

by Aniello Daniele Marano, Gianluca Diodati, Nicola Paletta, Luigi Di Palma, Marika Belardo and Pierre Abdel Nour

Aerospace 2023, 10(5), 478; https://doi.org/10.3390/aerospace10050478 - 18 May 2023

Cited by 3 | Viewed by 2299

Abstract

This paper is focused on structural scalability studies of a new generation of civil tiltrotor wingbox structures. Starting from a reference wingbox, developed under the H2020 Clean Sky 2 NGCTR-TD T-WING project, a geometric scaling was performed to upscale the concept up to [...] Read more.

This paper is focused on structural scalability studies of a new generation of civil tiltrotor wingbox structures. Starting from a reference wingbox, developed under the H2020 Clean Sky 2 NGCTR-TD T-WING project, a geometric scaling was performed to upscale the concept up to a larger class tiltrotor named “NGCTR”. Given the wing and the wingbox geometry, a multi-objective optimization, based on genetic algorithms, was performed to find for the NGCTR, among different materials and layups, the best composite wing in terms of weight that satisfies stiffness and crash requirements. The crash requirement plays an important role in regards to wing weight performance. It was found that not all materials investigated in this study succeeded in satisfying both stiffness and crash requirements. The results in terms of minimum structural mass as the target of the optimization process show that the mass ratio of the optimized up-scaled wing is near the geometrical scale factor: 1.58 vs. 1.29. Furthermore, the solution found by the optimizer NGCTR upscaled wing is comparable with other tiltrotor data coming from a literature study. The difference in terms of the ratio between wing structural weight and tiltrotor MTOW is Δ% = +1.4: an acceptable small overestimation of weight compared to a design, optimization, and scalability method that is easily adaptable and effective. The study presented in this work is, in fact, part of a broader activity on scalability and constitutes its first phase, based on low-fidelity models. The scalability study will continue with a further phase (indicated as “phase 2”), in which more reliable models will be set up, allowing a better estimation of the wing’s structural weight and further optimization. The results shown in this manuscript concern phase 1 only and can be considered a starting point at the System Requirements Review level of the up-scaled wing. This phase allowed for a fast exploration of the available solutions by making a first assessment of the main requirements and by aiding in the material choice at the very beginning of the design. Full article

(This article belongs to the Section Aeronautics)

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17 pages, 435 KiB

Open AccessArticle

A Geometrical, Reachable Set Approach for Constrained Pursuit–Evasion Games with Multiple Pursuers and Evaders

by Olli Jansson and Matthew W. Harris

Aerospace 2023, 10(5), 477; https://doi.org/10.3390/aerospace10050477 - 18 May 2023

Cited by 2 | Viewed by 2074

Abstract

This paper presents a solution strategy for deterministic time-optimal pursuit–evasion games with linear state constraints, convex control constraints, and linear dynamics that is consistent with linearized relative orbital motion models such as the Clohessy–Wiltshire equations and relative orbital elements. The strategy first generates [...] Read more.

This paper presents a solution strategy for deterministic time-optimal pursuit–evasion games with linear state constraints, convex control constraints, and linear dynamics that is consistent with linearized relative orbital motion models such as the Clohessy–Wiltshire equations and relative orbital elements. The strategy first generates polytopic inner approximations of the players’ reachable sets by solving a sequence of convex programs. A bisection method then computes the optimal termination time, which is the least time at which a set containment condition is satisfied. The pursuit–evasion games considered are games with (1) a single pursuer and single evader, (2) multiple pursuers and a single evader, and (3) a single pursuer and multiple evaders. Compared to variational methods, this reachable set strategy leads to a tractable formulation even when there are state and control constraints. The efficacy of the strategy is demonstrated in three numerical simulations for a constellation of satellites in close proximity in low earth orbit. Full article

(This article belongs to the Special Issue Convex Optimization for Aerospace Guidance and Control Applications)

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20 pages, 6315 KiB

Open AccessArticle

Effect of Temperature on the Functionalization Process of Structural Self-Healing Epoxy Resin

by Luigi Vertuccio, Elisa Calabrese, Marialuigia Raimondo, Michelina Catauro, Andrea Sorrentino, Carlo Naddeo, Raffaele Longo and Liberata Guadagno

Aerospace 2023, 10(5), 476; https://doi.org/10.3390/aerospace10050476 - 18 May 2023

Cited by 3 | Viewed by 1835

Abstract

This work deals with developing a self-healing resin designed for aeronautical and aerospace applications. The bifunctional epoxy precursor was suitably functionalized to enhance its toughness to realize good compatibilization with a rubber phase dispersed in the hosting epoxy resin. Subsequently, the resulting mixture [...] Read more.

This work deals with developing a self-healing resin designed for aeronautical and aerospace applications. The bifunctional epoxy precursor was suitably functionalized to enhance its toughness to realize good compatibilization with a rubber phase dispersed in the hosting epoxy resin. Subsequently, the resulting mixture was loaded with healing molecules. The effect of the temperature on the epoxy precursor’s functionalization process was deeply studied. Fourier trans-former infrared (FT-IR) spectroscopy and dynamic mechanical analyses (DMA) evidenced that the highest temperature (160 °C) allows for obtaining a bigger amount of rubber phase bonded to the matrix. Elastomeric domains of dimensions lower than 500–600 nanometers were found well distributed in the matrix. Self-healing efficiency evaluated with the tapered double cantilever beam (TDCB) method evidenced a healing efficiency for the system functionalized at 160 °C higher than 69% for all the explored fillers. The highest value was detected for the sample with DBA, for which 88% was found. The healing efficiency of the same sample functionalized at 120 °C was found to decrease to the value of 52%. These results evidence the relevant role of the amount and distribution of rubber domains into the resin for improving the resin’s dynamic properties. The adopted strategy allows for optimizing the self-healing performance. Full article

(This article belongs to the Special Issue 12th EASN International Conference on Innovation in Aviation & Space for Opening New Horizons)

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20 pages, 4601 KiB

Open AccessArticle

Time-Inclined Method for High-Fidelity Rotor/Stator Simulations

by Miguel Montiel and Roque Corral

Aerospace 2023, 10(5), 475; https://doi.org/10.3390/aerospace10050475 - 18 May 2023

Cited by 1 | Viewed by 1996

Abstract

The application of the time-inclined method in a fourth-order unstructured flux-reconstruction code for turbomachinery is demonstrated. Inviscid and viscous unsteady results due to the interaction of an incoming gust of total pressure with a linear cascade of flat plates and a linear cascade [...] Read more.

The application of the time-inclined method in a fourth-order unstructured flux-reconstruction code for turbomachinery is demonstrated. Inviscid and viscous unsteady results due to the interaction of an incoming gust of total pressure with a linear cascade of flat plates and a linear cascade of T106A low-pressure turbine airfoils are reported. The agreement between the time-inclined method and the equivalent full-annulus multipassage solution is very high for both cases. Viscous solutions at Reynolds numbers of

10^{4}

and

10^{5}

were conducted. A high degree of matching was obtained between the time-inclined and the whole annulus approaches. The limitations of the method are explored and discussed. While the evolution of the unsteady boundary layers created by the interaction with the incoming wakes was very well captured, the mixing associated with the trailing edge vortex shedding was less accurate. The critical parameter controlling the method’s accuracy is the local Strouhal number. It was demonstrated that the benefit of retaining the exact blade count in the simulations overcomes the slight differences in the mixing due to the limitation of the time-inclined method to model viscous effects accurately in all situations. Full article

(This article belongs to the Section Aeronautics)

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23 pages, 1496 KiB

Open AccessArticle

An Explainable Artificial Intelligence Approach for Remaining Useful Life Prediction

by Genane Youness and Adam Aalah

Aerospace 2023, 10(5), 474; https://doi.org/10.3390/aerospace10050474 - 18 May 2023

Cited by 9 | Viewed by 3242

Abstract

Prognosis and health management depend on sufficient prior knowledge of the degradation process of critical components to predict the remaining useful life. This task is composed of two phases: learning and prediction. The first phase uses the available information to learn the system’s [...] Read more.

Prognosis and health management depend on sufficient prior knowledge of the degradation process of critical components to predict the remaining useful life. This task is composed of two phases: learning and prediction. The first phase uses the available information to learn the system’s behavior. The second phase predicts future behavior based on the available information of the system and estimates its remaining lifetime. Deep learning approaches achieve good prognostic performance but usually suffer from a high computational load and a lack of interpretability. Complex feature extraction models do not solve this problem, as they lose information in the learning phase and thus have a poor prognosis for the remaining lifetime. A new prepossessing approach is used with feature clustering to address this issue. It allows for restructuring the data into homogeneous groups strongly related to each other using a simple architecture of the LSTM model. It is advantageous in terms of learning time and the possibility of using limited computational capabilities. Then, we focus on the interpretability of deep learning prognosis using Explainable AI to achieve interpretable RUL prediction. The proposed approach offers model improvement and enhanced interpretability, enabling a better understanding of feature contributions. Experimental results on the available NASA C-MAPSS dataset show the performance of the proposed model compared to other common methods. Full article

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

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18 pages, 8428 KiB

Open AccessArticle

A Coupled Heat Transfer Calculation Strategy for Composite Cooling Liquid Rocket Engine

by Bo Xu, Bing Chen, Jian Peng, Wenyuan Zhou and Xu Xu

Aerospace 2023, 10(5), 473; https://doi.org/10.3390/aerospace10050473 - 17 May 2023

Cited by 2 | Viewed by 3286

Abstract

To better understand the characteristics of coupled heat transfer in liquid rocket engines, a calculation scheme is proposed in this paper. This scheme can simulate the coupled heat transfer processes, including combustion and flow in the thrust chamber, radiation heat transfer, heat conduction [...] Read more.

To better understand the characteristics of coupled heat transfer in liquid rocket engines, a calculation scheme is proposed in this paper. This scheme can simulate the coupled heat transfer processes, including combustion and flow in the thrust chamber, radiation heat transfer, heat conduction in the wall, heat transfer of coolant flow in the cooling channel, and gas film cooling in the thrust chamber wall. The numerical method used in each physical area, the data transfer method between each computing module, the strategy of data transfer on the coupling interface, the calculation process, and the convergence criterion are all introduced in detail. The calculation scheme was verified by analyzing a water-cooled nozzle. Then, the coupled heat transfer calculation was carried out for a liquid rocket engine using a propellant composed of unsymmetrical dimethylhydrazine and dinitrogen tetroxide. Two working conditions were analyzed: whether the gas film cooling was performed or not. The results showed that the algorithm successfully indicated the protective effect of the gas film on the wall surface, and the calculation results were reasonable. It played a guiding role for the coupled heat transfer of the liquid rocket engine using a composite cooling method. Full article

(This article belongs to the Special Issue Film Cooling in Aerospace Applications)

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17 pages, 7987 KiB

Open AccessArticle

Numerical Modeling of Thermal Behavior during Lunar Soil Drilling

by Deming Zhao, Zhisheng Cheng, Weiwei Zhang, Jinsheng Cui and He Wang

Aerospace 2023, 10(5), 472; https://doi.org/10.3390/aerospace10050472 - 17 May 2023

Cited by 5 | Viewed by 1787

Abstract

This paper presents a detailed thermal simulation analysis of the drilling process for icy soil in the lunar polar region. The aim is to investigate the temperature changes that occur in the debris removal area during the drilling process. We developed a multi-level [...] Read more.

This paper presents a detailed thermal simulation analysis of the drilling process for icy soil in the lunar polar region. The aim is to investigate the temperature changes that occur in the debris removal area during the drilling process. We developed a multi-level particle size simulation model that includes a thermal sieve based on geometric constraints to evaluate the influence of specific heat capacity and thermal conductivity on particle temperature. Using the central composite design method, we carried out the simulation test design and analyzed the average temperature difference of particles within and outside the range of the thermal sieve. The parameters of the discrete element model were determined by comparing the temperature of the debris removal zone in the lunar environment with the temperature simulated by the discrete element method. The results show that the thermal conductivity of the sieve ranges from 100 to 400 W/m, and the average temperature inside the thermal sieve is negatively related to the specific heat capacity. The temperature deviation of the chip removal area is ±10 °C, which is consistent with the temperature deviation observed in the lunar environment and the lunar icy regolith drilling test. Furthermore, the addition of the thermal sieve to the multi-stage particle size simulation modeling significantly reduces the calculation time by 86%. This reduction in computational time may potentially increase the efficiency of drilling operations in the future. Our study provides insights into the thermal behavior of lunar icy regolith during drilling, and proposes a numerical model of heat transfer with a thermal sieve that can effectively reduce computational time while ensuring accurate temperature calculations. Full article

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

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18 pages, 1642 KiB

Open AccessArticle

Full State Constrained Flight Tracking Control for Helicopter Systems with Disturbances

by Yankai Li, Yulong Huang, Han Liu and Dongping Li

Aerospace 2023, 10(5), 471; https://doi.org/10.3390/aerospace10050471 - 17 May 2023

Cited by 1 | Viewed by 1353

Abstract

In this paper, a full state-constrained anti-disturbance dynamic surface control method is proposed for six-degree-of-freedom unmanned helicopter systems under full state constraints and disturbances. Firstly, due to the underactuated characteristics of six-degree-of-freedom unmanned helicopter systems, an input–output feedback linearization method is used to [...] Read more.

In this paper, a full state-constrained anti-disturbance dynamic surface control method is proposed for six-degree-of-freedom unmanned helicopter systems under full state constraints and disturbances. Firstly, due to the underactuated characteristics of six-degree-of-freedom unmanned helicopter systems, an input–output feedback linearization method is used to transform the complex nonlinear systems into facilitated-control nonlinear ones. Based on the transformed systems, the nonlinear disturbance-observer-based control, backstepping control and Barrier Lyapunov function methods are used to construct the flight controller via uniting the state constraint control and dynamic surface control technologies. Then, Lyapunov stability theory is adopted for analysing the closed-loop tracking error systems, which confirms that the tracking errors are bounded under the proposed flight control scheme. Finally, a simulation in the MATLAB/Simulink environment verifies that the unmanned helicopter system can constrain all states under the action of the designed controller, with good dynamic performance. Full article

(This article belongs to the Special Issue Advanced Motion Planning and Control in Aerospace Applications)

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16 pages, 36603 KiB

Open AccessArticle

Nonintrusive Aerodynamic Shape Optimisation with a POD-DEIM Based Trust Region Method

by Simão Marques, Lucas Kob, Trevor T. Robinson and Weigang Yao

Aerospace 2023, 10(5), 470; https://doi.org/10.3390/aerospace10050470 - 17 May 2023

Cited by 2 | Viewed by 1612

Abstract

This work presents a strategy to build reduced-order models suitable for aerodynamic shape optimisation, resulting in a multifidelity optimisation framework. A reduced-order model (ROM) based on a discrete empirical interpolation (DEIM) method is employed in lieu of computational fluid dynamics (CFD) solvers for [...] Read more.

This work presents a strategy to build reduced-order models suitable for aerodynamic shape optimisation, resulting in a multifidelity optimisation framework. A reduced-order model (ROM) based on a discrete empirical interpolation (DEIM) method is employed in lieu of computational fluid dynamics (CFD) solvers for fast, nonlinear, aerodynamic modelling. The DEIM builds a set of interpolation points that allows it to reconstruct the flow fields from sets of basis obtained by proper orthogonal decomposition of a matrix of snapshots. The aerodynamic reduced-order model is completed by introducing a nonlinear mapping function between surface deformation and the DEIM interpolation points. The optimisation problem is managed by a trust region algorithm linking the multiple-fidelity solvers, with each subproblem solved using a gradient-based algorithm. The design space is initially restricted; as the optimisation trajectory evolves, new samples enrich the ROM. The proposed methodology is evaluated using a series of transonic viscous test cases based on wing configurations. Results show that for cases with a moderate number of design variables, the approach proposed is competitive with state-of-the-art gradient-based methods; in addition, the use of trust region methodology mitigates the likelihood of the optimiser converging to, shallower, local minima. Full article

(This article belongs to the Section Aeronautics)

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17 pages, 7523 KiB

Open AccessArticle

On the Possibility of Cross-Flow Vortex Cancellation by Plasma Actuators

by Amir Abdullaev, Alexander Kotvitskii, Ivan Moralev and Maxim Ustinov

Aerospace 2023, 10(5), 469; https://doi.org/10.3390/aerospace10050469 - 17 May 2023

Cited by 2 | Viewed by 1731

Abstract

Cancellation of the cross-flow vortices in a swept-wing boundary layer is attempted by plasma actuator array in numerical simulation. The response of the boundary layer to the stationary excitation by a single actuator section is measured experimentally and compared to the response obtained [...] Read more.

Cancellation of the cross-flow vortices in a swept-wing boundary layer is attempted by plasma actuator array in numerical simulation. The response of the boundary layer to the stationary excitation by a single actuator section is measured experimentally and compared to the response obtained from the solution to the parabolized stability equations. A linear approach is shown to be held within the peak-to-peak magnitude of the stationary cross-flow vortices below 10% of the local potential flow velocity. Within the linear model, an optimal control strategy and a faster suboptimal one are developed to calculate voltage amplitude distribution across the electrodes, taking into account the forcing constraints. Simulation of the cancellation process is performed, showing up to a 20 dB reduction in the initial spanwise velocity modulation in the boundary layer. The minimal actuator resolution required for the successive implementation of the control is shown to be in the order of a quarter of the most amplified wavelength, or 3–4 displacement thickness of the boundary layer. Linear estimates predict up to a 150 mm (22% of flow acceleration region length) transition delay for an actuator momentum coefficient of 0.005%. Full article

(This article belongs to the Special Issue Plasma Actuator)

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22 pages, 4975 KiB

Open AccessArticle

Comparative Cost Functions Analysis in the Construction of a Reference Angular Motion Implemented by Magnetorquers

by Anna Okhitina, Stepan Tkachev and Dmitry Roldugin

Aerospace 2023, 10(5), 468; https://doi.org/10.3390/aerospace10050468 - 17 May 2023

Cited by 1 | Viewed by 1241

Abstract

This paper considers a construction procedure of a satellite reference angular motion in the vicinity of an unstable gravitational equilibrium position. The satellite is stabilized on the reference trajectory by the magnetic coils. The problem is solved in several stages. An optimization problem [...] Read more.

This paper considers a construction procedure of a satellite reference angular motion in the vicinity of an unstable gravitational equilibrium position. The satellite is stabilized on the reference trajectory by the magnetic coils. The problem is solved in several stages. An optimization problem to be solved by the particle swarm optimization method is formulated at each stage. Cost functions are based on the linearized model analysis. The main stage is the construction of a special reference motion, which provides the minimum control torque projection on the geomagnetic induction vector. Optimal geomagnetic field dipole approximation for a given time interval is considered to reduce tracking errors. The paper compares combinations of different cost functions in terms of the terminal attitude accuracy in the presence of perturbations. Full article

(This article belongs to the Collection Space Systems Dynamics)

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19 pages, 8674 KiB

Open AccessArticle

Rapid Parametric CAx Tools for Modelling Morphing Wings of Micro Air Vehicles (MAVs)

by Ángel Antonio Rodríguez-Sevillano, María Jesús Casati-Calzada, Rafael Bardera-Mora, Javier Nieto-Centenero, Juan Carlos Matías-García and Estela Barroso-Barderas

Aerospace 2023, 10(5), 467; https://doi.org/10.3390/aerospace10050467 - 17 May 2023

Cited by 4 | Viewed by 1545

Abstract

This paper shows a series of tools that help in the research of morphing micro air vehicles (MAVs). These tools are aimed at generating parametric CAD models of wings in a few seconds that can be used in aerodynamic studies, either via CFD [...] Read more.

This paper shows a series of tools that help in the research of morphing micro air vehicles (MAVs). These tools are aimed at generating parametric CAD models of wings in a few seconds that can be used in aerodynamic studies, either via CFD directly using the model obtained or via wind tunnel through rapid prototyping with 3D printers. It also facilitates the analysis of morphing wings by allowing for the continuous parametric deformation of the airfoils and the wing geometry. In addition, one of the tools greatly simplifies the purely experimental design of this type of vehicle, allowing the transfer of experimental measurements to the computer, generating virtual models with the same deformation as the physical model. This software has two fundamental parts. The first one is the parameterization of the airfoils, for which the CST (Class-Shape Transformation) method will be used. CST coefficients can be modified according to the actuator variable that changes the wing geometry. The second part is the generation of a three-dimensional parametric model of the wing. We used OpenCASCADE technology in its Python version called PythonOCC, which enables the generation of geometries with good surface quality for typical and non-standard wing shapes. Finally, the use of this software for the study of a morphing aircraft will be shown, as well as improvements that could be incorporated in the future to increase its capabilities for the design and analysis of MAVs. Full article

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

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17 pages, 6750 KiB

Open AccessArticle

Space Robot On-Orbit Operation of Insertion and Extraction Impedance Control Based on Adaptive Neural Network

by Dongbo Liu and Li Chen

Aerospace 2023, 10(5), 466; https://doi.org/10.3390/aerospace10050466 - 16 May 2023

Cited by 6 | Viewed by 1488

Abstract

The on-orbit operation of insertion and extraction of space robots is a technology essential to the assembly and maintenance in orbit, satellite fuel filling, failed satellite recovery, especially modular in-orbit assembly of micro-spacecraft. Therefore, the force/posture impedance control for the on-orbit operation of [...] Read more.

The on-orbit operation of insertion and extraction of space robots is a technology essential to the assembly and maintenance in orbit, satellite fuel filling, failed satellite recovery, especially modular in-orbit assembly of micro-spacecraft. Therefore, the force/posture impedance control for the on-orbit operation of insertion and extraction is studied. Firstly, the dynamic model of space robots’ system in the form of uncontrolled carrier position and controlled attitude is derived by using the momentum conservation principle. Through the kinematic constraints of the replacement component plug, the Jacobi relationship of the plug motion in the base coordinate system is established. Secondly, to achieve the output force control of the plug during the on-orbit operation of insertion and extraction, a second-order linear impedance model is established based on the dynamic relationship between the plug posture and its output force and the impedance control principle. Then, in order to improve the stability, robustness, and adaptability of the controller, an adaptive Radial Basis Function Neural Network (RBFNN) is used to approximate the uncertainties in the dynamic model for the force/posture control of the plug. Finally, the stability of the system is verified by the Lyapunov principle. The simulation results show that the designed neural network impedance control strategy can achieve a control accuracy of less than

10^{- 3}

rad for the plug’s attitude tracking error, less than

10^{- 3}

m for its position tracking error, and less than 0.5 N for its output force tracking error. Full article

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

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18 pages, 1648 KiB

Open AccessArticle

A Flexible Code Review Framework for Combining Defect Detection and Review Comments

by Xi Chen, Lei Dong, Hong-Chang Li, Xin-Peng Yao, Peng Wang and Shuang Yao

Aerospace 2023, 10(5), 465; https://doi.org/10.3390/aerospace10050465 - 16 May 2023

Cited by 1 | Viewed by 1796

Abstract

Defects and errors in code are different in that they are not detected by editors or compilers but pose a potential risk to software operation. For safety-critical software such as airborne software, the code review process is necessary to ensure the proper operation [...] Read more.

Defects and errors in code are different in that they are not detected by editors or compilers but pose a potential risk to software operation. For safety-critical software such as airborne software, the code review process is necessary to ensure the proper operation of software applications and even an aircraft. The traditional manual review method can no longer meet the current needs with the dramatic increase in code sizes and variety. To this end, we propose Deep Reviewer, a general and flexible code review framework that automatically detects code defects and correlates the review comments of the defects. The framework first preprocesses the data using several methods, including the proposed D2U flow. Then, features are extracted and matched by the detector, which contains a pair of twin LSTM models, one for code defect type detection and the other for review comment retrieval. Finally, the review comment output function is implemented based on the masks generated by the code defect types. The method is validated using a large public dataset, SARD. For the binary-classification task, the test results of the proposed are 98.68% and 98.67% in terms of precision and F1 score, respectively. For the multi-classification task, the proposed framework shows a significant advantage over other methods. Full article

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

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16 pages, 1972 KiB

Open AccessArticle

Applied Trajectory Design for CubeSat Close-Proximity Operations around Asteroids: The Milani Case

by Claudio Bottiglieri, Felice Piccolo, Carmine Giordano, Fabio Ferrari and Francesco Topputo

Aerospace 2023, 10(5), 464; https://doi.org/10.3390/aerospace10050464 - 16 May 2023

Cited by 4 | Viewed by 1929

Abstract

In this paper, a practical approach to trajectory design for asteroid exploration missions with CubeSats is presented. When applied trajectories are sought, operative concerns and uncertainties affecting the spacecraft dynamics must be considered during the preliminary design process. Otherwise, trajectories that are possible [...] Read more.

In this paper, a practical approach to trajectory design for asteroid exploration missions with CubeSats is presented. When applied trajectories are sought, operative concerns and uncertainties affecting the spacecraft dynamics must be considered during the preliminary design process. Otherwise, trajectories that are possible on paper might become infeasible when real-world constraints are considered. The risk of such eventualities leads to the need to extend the trajectory design to focus on the uncertainties affecting the dynamics and on the operative constraints derived by ground operations. This is especially true when targeting highly perturbed environments such as small bodies with low-cost solutions such as CubeSats, whose capabilities in deep space are still unknown. The case study presented is the Milani CubeSat, which will be launched in 2024 with Hera in the frame of the AIDA mission. Full article

(This article belongs to the Special Issue Dynamics and Control Problems on Asteroid Explorations)

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24 pages, 8749 KiB

Open AccessArticle

Flow Characterization of the UTSA Hypersonic Ludwieg Tube

by Eugene N. A. Hoffman, Elijah J. LaLonde, Angelina Andrade, Ivana Chen, Hayden A. Bilbo and Christopher S. Combs

Aerospace 2023, 10(5), 463; https://doi.org/10.3390/aerospace10050463 - 16 May 2023

Cited by 10 | Viewed by 2967

Abstract

The characterization of a hypersonic impulse facility is performed using a variety of methods including Pitot probe scans, particle image velocimetry, and schlieren imaging to verify properties such as the velocity, Mach number, wall boundary layer thickness, and freestream turbulence intensity levels. The [...] Read more.

The characterization of a hypersonic impulse facility is performed using a variety of methods including Pitot probe scans, particle image velocimetry, and schlieren imaging to verify properties such as the velocity, Mach number, wall boundary layer thickness, and freestream turbulence intensity levels. The experimental results are compared to the numerical simulations of the facility performed with Ansys Fluent to compare the design and operational conditions. The presentation of results in this manuscript is prefaced by a description of the facility and its capabilities. The UTSA Ludwieg tube facility can produce a hypersonic freestream flow with a Mach number of 7.2 ± 0.2 and unit Reynolds numbers of up to 200 × 10⁶ m⁻¹. The Pitot probe profiles of the 203-mm-square test section indicate a 152 ± 10 mm square freestream core with turbulence intensity values ranging from 1% to 2%. Schlieren imaging of the oblique shockwaves on a 15° wedge model provided an alternate means of verifying the Mach number. Particle image velocimetry and previous molecular tagging velocimetry results showed a good agreement with the Pitot probe data and numerical simulations in the key parameters including freestream velocity, wall boundary layer velocity profiles, and wall boundary layer thickness. Full article

(This article belongs to the Section Aeronautics)

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