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Aerospace
Volume 8
Issue 6
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Aerospace, Volume 8, Issue 6 (June 2021) – 25 articles

Cover Story (view full-size image): The ingestion of dust particles by aero-engines results in reduced efficiency, performance and engine life. Predicting the rate at which this deterioration occurs requires knowledge of the engine operating state and particle properties, the latter of which are often unknown or poorly constrained. Coupling reduced-order component damage models with engine performance predictions allows a Monte Carlo analysis to be undertaken and performance degradation rates to be predicted with calculated levels of confidence. The coupled approach can also be used to predict the uncertain dust properties by correlation with measured engine performance degradation. This will ultimately enable the use of the model to predict future engine degradation and, therefore, aid progress towards more predictive maintenance strategies. View this paper.
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26 pages, 5585 KiB  
Article
Modular Impulsive Green Monopropellant Propulsion System (MIMPS-G): For CubeSats in LEO and to the Moon
by Ahmed E. S. Nosseir, Angelo Cervone and Angelo Pasini
Aerospace 2021, 8(6), 169; https://doi.org/10.3390/aerospace8060169 - 19 Jun 2021
Cited by 14 | Viewed by 6634
Abstract
Green propellants are currently considered as enabling technology that is revolutionizing the development of high-performance space propulsion, especially for small-sized spacecraft. Modern space missions, either in LEO or interplanetary, require relatively high-thrust and impulsive capabilities to provide better control on the spacecraft, and [...] Read more.
Green propellants are currently considered as enabling technology that is revolutionizing the development of high-performance space propulsion, especially for small-sized spacecraft. Modern space missions, either in LEO or interplanetary, require relatively high-thrust and impulsive capabilities to provide better control on the spacecraft, and to overcome the growing challenges, particularly related to overcrowded LEOs, and to modern space application orbital maneuver requirements. Green monopropellants are gaining momentum in the design and development of small and modular liquid propulsion systems, especially for CubeSats, due to their favorable thermophysical properties and relatively high performance when compared to gaseous propellants, and perhaps simpler management when compared to bipropellants. Accordingly, a novel high-thrust modular impulsive green monopropellant propulsion system with a micro electric pump feed cycle is proposed. MIMPS-G500mN is designed to be capable of delivering 0.5 N thrust and offers theoretical total impulse Itot from 850 to 1350 N s per 1U and >3000 N s per 2U depending on the burnt monopropellant, which makes it a candidate for various LEO satellites as well as future Moon missions. Green monopropellant ASCENT (formerly AF-M315E), as well as HAN and ADN-based alternatives (i.e., HNP225 and LMP-103S) were proposed in the preliminary design and system analysis. The article will present state-of-the-art green monopropellants in the (EIL) Energetic Ionic Liquid class and a trade-off study for proposed propellants. System analysis and design of MIMPS-G500mN will be discussed in detail, and the article will conclude with a market survey on small satellites green monopropellant propulsion systems and commercial off-the-shelf thrusters. Full article
(This article belongs to the Special Issue Green Propulsion: Present Solutions and Perspectives for Powering Environmentally Friendly Space Missions)
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18 pages, 13452 KiB  
Article
Online Model-Based Remaining-Useful-Life Prognostics for Aircraft Cooling Units Using Time-Warping Degradation Clustering
by Mihaela Mitici and Ingeborg de Pater
Aerospace 2021, 8(6), 168; https://doi.org/10.3390/aerospace8060168 - 17 Jun 2021
Cited by 10 | Viewed by 3309
Abstract
Remaining-useful-life prognostics for aircraft components are central for efficient and robust aircraft maintenance. In this paper, we propose an end-to-end approach to obtain online, model-based remaining-useful-life prognostics by learning from clusters of components with similar degradation trends. Time-series degradation measurements are first clustered [...] Read more.
Remaining-useful-life prognostics for aircraft components are central for efficient and robust aircraft maintenance. In this paper, we propose an end-to-end approach to obtain online, model-based remaining-useful-life prognostics by learning from clusters of components with similar degradation trends. Time-series degradation measurements are first clustered using dynamic time-warping. For each cluster, a degradation model and a corresponding failure threshold are proposed. These cluster-specific degradation models, together with a particle filtering algorithm, are further used to obtain online remaining-useful-life prognostics. As a case study, we consider the operational data of several cooling units originating from a fleet of aircraft. The cooling units are clustered based on their degradation trends and remaining-useful-life prognostics are obtained in an online manner. In general, this approach provides support for intelligent aircraft maintenance where the analysis of cluster-specific component degradation models is integrated into the predictive maintenance process. Full article
(This article belongs to the Special Issue Fault Detection and Prognostics in Aerospace Engineering)
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21 pages, 8763 KiB  
Article
Fixed Wing Aircraft Automatic Landing with the Use of a Dedicated Ground Sign System
by Bartłomiej Brukarczyk, Dariusz Nowak, Piotr Kot, Tomasz Rogalski and Paweł Rzucidło
Aerospace 2021, 8(6), 167; https://doi.org/10.3390/aerospace8060167 - 16 Jun 2021
Cited by 13 | Viewed by 4157
Abstract
The paper presents automatic control of an aircraft in the longitudinal channel during automatic landing. There are two crucial components of the system presented in the paper: a vision system and an automatic landing system. The vision system processes pictures of dedicated on-ground [...] Read more.
The paper presents automatic control of an aircraft in the longitudinal channel during automatic landing. There are two crucial components of the system presented in the paper: a vision system and an automatic landing system. The vision system processes pictures of dedicated on-ground signs which appear to an on-board video camera to determine a glide path. Image processing algorithms used by the system were implemented into an embedded system and tested under laboratory conditions according to the hardware-in-the-loop method. An output from the vision system was used as one of the input signals to an automatic landing system. The major components are control algorithms based on the fuzzy logic expert system. They were created to imitate pilot actions while landing the aircraft. Both systems were connected with one another for cooperation and to control an aircraft model in a simulation environment. Selected results of tests presenting control efficiency and precision are shown in the final section of the paper. Full article
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13 pages, 8019 KiB  
Article
Effect of a Circular Slot on Hybrid Airship Aerodynamic Characteristics
by Sekar Mano, RadhaKrishnan Ajay Sriram, Ganesan Vinayagamurthy, Subramania Nadaraja Pillai, Amjad Ali Pasha, Dwarshala Siva Krishna Reddy and Mustafa Mutiur Rahman
Aerospace 2021, 8(6), 166; https://doi.org/10.3390/aerospace8060166 - 15 Jun 2021
Cited by 2 | Viewed by 3148
Abstract
This numerical study reports the aerodynamic properties of a hybrid airship. The hybrid airships were designed by combining two semi-ellipsoids with a semi-discoid as the base model. From the base model, three different geometrics were identified to study their aerodynamic characteristics. A circular [...] Read more.
This numerical study reports the aerodynamic properties of a hybrid airship. The hybrid airships were designed by combining two semi-ellipsoids with a semi-discoid as the base model. From the base model, three different geometrics were identified to study their aerodynamic characteristics. A circular slot was provided between the pressure side and the suction side of the airship. The objective of this study was to realize the flow behavior, aerodynamic characteristics, and stability properties of such slotted hybrid flying vehicles. Interestingly, the results imply that the lift coefficient increases with an increase in the angle of attack for the slotted configurations; this is because the flow separation is delayed due to the slot opening, which in turn is due to the flow of energies from the high-pressure region to the bottom through the slots. The delayed stall angle was 50 degrees, which was 10% more than that of the base model. Aerodynamic characteristics are discussed based on surface pressure, coefficient of lift, and coefficient of drag for various slotted hybrid airships. Full article
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23 pages, 2179 KiB  
Article
Data-Driven Simulation for Evaluating the Impact of Lower Arrival Aircraft Separation on Available Airspace and Runway Capacity at Tokyo International Airport
by Katsuhiro Sekine, Furuto Kato, Kota Kageyama and Eri Itoh
Aerospace 2021, 8(6), 165; https://doi.org/10.3390/aerospace8060165 - 13 Jun 2021
Cited by 19 | Viewed by 4529
Abstract
Although the application of new wake turbulence categories, the so-called “RECAT (wake turbulence category re-categorization)”, will realize lower aircraft separation minima and directly increase runway throughput, the impacts of increasing arrival traffic on the surrounding airspace and arrival traffic flow as a whole [...] Read more.
Although the application of new wake turbulence categories, the so-called “RECAT (wake turbulence category re-categorization)”, will realize lower aircraft separation minima and directly increase runway throughput, the impacts of increasing arrival traffic on the surrounding airspace and arrival traffic flow as a whole have not yet been discussed. This paper proposes a data-driven simulation approach and evaluates the effectiveness of the lower aircraft separation in the arrival traffic at the target airport. The maximum runway capacity was clarified using statistics on aircraft types, stochastic distributions of inter-aircraft time and runway occupancy time, and the levels of the automation systems that supported air traffic controllers’ separation work. Based on the estimated available runway capacity, simulation models were proposed by analyzing actual radar track and flight plan data during the 6 months between September 2019 and February 2020, under actual operational constraints and weather conditions. The simulation results showed that the application of RECAT would reduce vectoring time in the terminal area by 7% to 10% under the current airspace and runway capacity when following a first-come first-served arrival sequence. In addition, increasing airspace capacity by 10% in the terminal area could dramatically reduce en-route and takeoff delay times while keeping vectoring time the same as under the current operation in the terminal area. These findings clarified that applying RECAT would contribute to mitigating air traffic congestion close to the airport, and to reducing delay times in arrival traffic as a whole while increasing runway throughput. The simulation results demonstrated the relevance of the theoretical results given by queue-based approaches in the authors’ past studies. Full article
(This article belongs to the Collection Air Transportation—Operations and Management)
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13 pages, 299 KiB  
Article
Theory of Contrail Formation for Fuel Cells
by Klaus Gierens
Aerospace 2021, 8(6), 164; https://doi.org/10.3390/aerospace8060164 - 10 Jun 2021
Cited by 29 | Viewed by 5924
Abstract
The theory of contrail formation for fuel cells is derived. It is a variant of the well-known Schmidt-Appleman theory. The contrail factor or G-factor for fuel cells is much larger than for jet engines, such that condensation of the exhaust water vapour can [...] Read more.
The theory of contrail formation for fuel cells is derived. It is a variant of the well-known Schmidt-Appleman theory. The contrail factor or G-factor for fuel cells is much larger than for jet engines, such that condensation of the exhaust water vapour can happen even at the Earth’s surface in sufficiently cold (a few degrees above zero) weather. Contrail formation from fuel cells will occur frequently in the lower troposphere and is unavoidable below moderate temperature limits, in the upper troposphere and in the stratosphere. Despite the high frequency of contrail formation from fuel cells, their climate impact is lower than that of contrails from jet engines. Most fuel cell contrails will be short and those persistent ones will be optically thinner and have on average a shorter lifetime than traditional persistent contrails. From a climate point of view, the introduction of fuel cells into aviation can be recommended. Full article
(This article belongs to the Special Issue Aircraft Emissions and Climate Impact)
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29 pages, 1836 KiB  
Article
Influence of Novel Airframe Technologies on the Feasibility of Fully-Electric Regional Aviation
by Stanislav Karpuk and Ali Elham
Aerospace 2021, 8(6), 163; https://doi.org/10.3390/aerospace8060163 - 10 Jun 2021
Cited by 49 | Viewed by 9453
Abstract
The feasibility of regional electric aviation to reduce environmental impact highly depends on technological advancements of energy storage techniques, available battery energy density, and high-power electric motor technologies. However, novel airframe technologies also strongly affect the feasibility of a regional electric aircraft. In [...] Read more.
The feasibility of regional electric aviation to reduce environmental impact highly depends on technological advancements of energy storage techniques, available battery energy density, and high-power electric motor technologies. However, novel airframe technologies also strongly affect the feasibility of a regional electric aircraft. In this paper, the influence of novel technologies on the feasibility of regional electric aviation was investigated. Three game-changing technologies were applied to a novel all-electric regional aircraft: active flow control, active load alleviation, and novel materials and structure concepts. Initial conceptual design and mission analysis of the aircraft was performed using the aircraft design framework SUAVE, and the sensitivity of the most important technologies on the aircraft characteristics and performance were studied. Obtained results were compared against a reference ATR-72 aircraft. Results showed that an all-electric aircraft with airframe technologies might be designed with the maximum take-off weight increase of 50% starting from the battery pack energy density of 700 Wh/kg. The overall emission level of an all-electric aircraft with novel technologies is reduced by 81% compared to the ATR-72. On the other hand, novel technologies do not contribute to the reduction in Direct Operating Costs (DOC) starting from 700 Wh/kg if compared to an all-electric aircraft without technologies. An increase in DOC ranges from 43% to 30% depending on the battery energy density which creates a significant market obstacle for such type of airplanes. In addition, the aircraft shows high levels of energy consumption which concerns its energy efficiency. Finally, the sensitivity of DOC to novel technologies and sensitivities of aircraft characteristics to each technology were assessed. Full article
(This article belongs to the Special Issue Aircraft Design (SI-3/2021))
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22 pages, 584 KiB  
Article
Systemic Agent-Based Modeling and Analysis of Passenger Discretionary Activities in Airport Terminals
by Adin Mekić, Seyed Sahand Mohammadi Ziabari and Alexei Sharpanskykh
Aerospace 2021, 8(6), 162; https://doi.org/10.3390/aerospace8060162 - 9 Jun 2021
Cited by 7 | Viewed by 3909
Abstract
Discretionary activities such as retail, food, and beverages generate a significant amount of non-aeronautical revenue within the aviation industry. However, they are rarely taken into account in computational airport terminal models. Since discretionary activities affect passenger flow and global airport terminal performance, discretionary [...] Read more.
Discretionary activities such as retail, food, and beverages generate a significant amount of non-aeronautical revenue within the aviation industry. However, they are rarely taken into account in computational airport terminal models. Since discretionary activities affect passenger flow and global airport terminal performance, discretionary activities need to be studied in detail. Additionally, discretionary activities are influenced by other airport terminal processes, such as check-in and security. Thus, discretionary activities need to be studied in relation to other airport terminal processes. The aim of this study is to analyze discretionary activities in a systemic way, taking into account interdependencies with other airport terminal processes and operational strategies used to manage these processes. An agent-based simulation model for airport terminal operations was developed, which covers the main handling processes and passenger decision-making with discretionary activities. The obtained simulation results show that operational strategies that reduce passenger queue time or increase passenger free time can significantly improve global airport terminal performance through efficiency, revenue, and cost. Full article
(This article belongs to the Special Issue Application of Multiagent Systems and Artificial Intelligence Techniques in Aviation (Volume II))
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9 pages, 210 KiB  
Article
Monte Carlo Analysis: An Application to Aircraft Design and Crash
by Emre Soydemir and Panagiotis Petratos
Aerospace 2021, 8(6), 161; https://doi.org/10.3390/aerospace8060161 - 9 Jun 2021
Viewed by 5175
Abstract
The current study investigates the application of statistical methods to flight, which have been used in science over time to understand complex physical and mathematical systems by using randomly generated numbers as input into those systems to generate a range of solutions and, [...] Read more.
The current study investigates the application of statistical methods to flight, which have been used in science over time to understand complex physical and mathematical systems by using randomly generated numbers as input into those systems to generate a range of solutions and, specifically, how mathematics is used to examine airplane design and crash frequency. In order to make very accurate predictions, one also requires an appropriate mathematical model. Using randomly selected numbers, the Monte Carlo statistical method is able to make very accurate predictions. With the Monte Carlo statistical method, by using significantly larger numbers of trials, the likelihood of the solutions can be determined very accurately. Currently, Monte Carlo methods are widely used and play a key part in various fields of science. Monte Carlo methods have vast uses in trials with limited observations that cannot be replicated many times. This paper adds new findings to the knowledge base on causes of crashes by airplane design. First, mathematical methods are used in this paper to investigate what the most likely casualty number and range are in the five years after the first flight based on 5000 simulations. Second, an investigation is performed to determine if certain casualty numbers are outliers of certain airplane designs based on the number of casualties reported using Monte Carlo analysis. Full article
20 pages, 3947 KiB  
Article
The Effect of Manufacturing Quality on Rocket Precision
by Zvonko Trzun, Milan Vrdoljak and Hrvoje Cajner
Aerospace 2021, 8(6), 160; https://doi.org/10.3390/aerospace8060160 - 4 Jun 2021
Cited by 3 | Viewed by 4239
Abstract
The effect of manufacturing quality on rocket impact point dispersion is analyzed. The approach presented here applies to any type of rocket. Here, manufacturing quality is demonstrated for the unguided rocket, and by simulating four typical manufacturing errors: erroneously manufactured warhead, misalignment between [...] Read more.
The effect of manufacturing quality on rocket impact point dispersion is analyzed. The approach presented here applies to any type of rocket. Here, manufacturing quality is demonstrated for the unguided rocket, and by simulating four typical manufacturing errors: erroneously manufactured warhead, misalignment between the warhead and engine chamber, asymmetrically installed propellant, and error in nozzle manufacturing. A new methodology is proposed, which combines a 3D CAD model of the asymmetrical projectile (due to manufacturing errors) and the improved Six-degrees-of-freedom (6DOF) model of its flight into a comprehensive Monte-Carlo simulation. In that way, the rocket trajectory dispersion is correlated directly to the imperfection of the manufacturing process. Three quality levels are simulated (low, standard, and high quality), and each of the analyzed manufacturing errors depends on the chosen quality. The results show how important it is to impose the highest quality on nozzle manufacturing, and if this condition is not met, reveal if strict tolerances applied to other steps of the manufacturing process can compensate for the consequential drop of precision. Full article
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17 pages, 9851 KiB  
Article
Design of Software-Defined Radio-Based Adaptable Packet Communication System for Small Satellites
by Yasir M. O. ABBAS and Kenichi Asami
Aerospace 2021, 8(6), 159; https://doi.org/10.3390/aerospace8060159 - 4 Jun 2021
Cited by 2 | Viewed by 4566
Abstract
Software-defined radio (SDR) devices have made a massive contribution to communication systems by reducing the cost and development time for radio frequency (RF) designs. SDRs opened the gate to programmers and enabled them to increase the capabilities of these easily manipulated systems. The [...] Read more.
Software-defined radio (SDR) devices have made a massive contribution to communication systems by reducing the cost and development time for radio frequency (RF) designs. SDRs opened the gate to programmers and enabled them to increase the capabilities of these easily manipulated systems. The next step is to upgrade the reconfigurability into adaptability, which is the focus of this paper. This research contributes to improving SDR-based systems by designing an adaptable packet communication transmitter and receiver that can utilize the communication window of CubeSats and small satellites. According to the feedback from the receiver, the transmitter modifies the characteristics of the signal. Theoretically, the system can adopt many modes, but for simplicity and to prove the concept, here, the changes are limited to three data rates of the Gaussian minimum shift keying (GMSK) modulation scheme, i.e., 2400 bps GMSK, 4800 bps GMSK and 9600 bps GMSK, which are the most popular in amateur small satellites. The system program was developed using GNU Radio Companion (GRC) software and Python scripts. With the help of GRC software, the design was simulated and its behavior in simulated conditions observed. The transmitter packetizes the data into AX.25 packets and transmits them in patches. Between these patches, it sends signaling packets. The patch size is preselected. Alternatively, the receiver extracts the data and saves it in a dedicated file. It directly replies with a feedback message whenever it gets the signaling packets. Based on the content of the feedback message, the characteristics of the transmitted signal are altered. The packet rate and the actual useful data rate are measured and compared with the selected data rate, and the packet success rate of the system operating at a fixed data rate is also measured while simulating channel noise to achieve the desired Signal-to-Noise Ratio (SNR). Full article
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18 pages, 3123 KiB  
Article
Design of the Electronic Engine Control Unit Performance Test System of Aircraft
by Seonghee Kho and Hyunbum Park
Aerospace 2021, 8(6), 158; https://doi.org/10.3390/aerospace8060158 - 3 Jun 2021
Cited by 4 | Viewed by 4156
Abstract
In this study, a real-time engine model and a test bench were developed to verify the performance of the EECU (electronic engine control unit) of a turbofan engine. The target engine is a DGEN 380 developed by the Price Induction company. The functional [...] Read more.
In this study, a real-time engine model and a test bench were developed to verify the performance of the EECU (electronic engine control unit) of a turbofan engine. The target engine is a DGEN 380 developed by the Price Induction company. The functional verification of the test bench was carried out using the developed test bench. An interface and interworking test between the test bench and the developed EECU was carried out. After establishing the verification test environments, the startup phase control logic of the developed EECU was verified using the real-time engine model which modeled the startup phase test data with SIMULINK. Finally, it was confirmed that the developed EECU can be used as a real-time engine model for the starting section of performance verification. Full article
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11 pages, 5361 KiB  
Article
The Effect of Vortex Generators on Shock-Induced Boundary Layer Separation in a Transonic Convex-Corner Flow
by Kung-Ming Chung, Kao-Chun Su and Keh-Chin Chang
Aerospace 2021, 8(6), 157; https://doi.org/10.3390/aerospace8060157 - 2 Jun 2021
Cited by 15 | Viewed by 3371
Abstract
Deflected control surfaces can be used as variable camber control in different flight conditions, and a convex corner resembles a simplified configuration for the upper surface. This experimental study determines the presence of passive vortex generators, VGs (counter-rotating vane type), on shock-induced boundary [...] Read more.
Deflected control surfaces can be used as variable camber control in different flight conditions, and a convex corner resembles a simplified configuration for the upper surface. This experimental study determines the presence of passive vortex generators, VGs (counter-rotating vane type), on shock-induced boundary layer separation for transonic convex-corner flow. The mean surface pressure distributions in the presence of VGs for h/δ = 0.2 and 0.5 are similar to those for no flow control. If h/δ = 1.0 and 1.5, there is an increase in the amplitude of the mean surface pressure upstream of the corner’s apex, which corresponds to greater device drag and less downstream expansion. There is a decrease in peak pressure fluctuations as the value of h/δ increases, because there is a decrease in separation length and the frequency of shock oscillation. The effectiveness of VGs also depends on the freestream Mach number. For M = 0.89, there is an extension in the low-pressure region downstream of a convex corner, because there is greater convection and induced streamwise vorticity. VGs with h/δ ≤ 0.5 are preferred if deflected control surfaces are used to produce lift. Full article
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17 pages, 6863 KiB  
Article
Research on Task Satellite Selection Method for Space Object Detection LEO Constellation Based on Observation Window Projection Analysis
by Shengyu Zhang, Zhencai Zhu, Haiying Hu and Yuqing Li
Aerospace 2021, 8(6), 156; https://doi.org/10.3390/aerospace8060156 - 31 May 2021
Cited by 6 | Viewed by 2625
Abstract
Aiming at the task planning and scheduling problem of space object detection LEO constellation (SODLC) for detecting space objects in deep space background, a method of SODLC task satellite selection based on observation window projection analysis is proposed. This method projects the spatial [...] Read more.
Aiming at the task planning and scheduling problem of space object detection LEO constellation (SODLC) for detecting space objects in deep space background, a method of SODLC task satellite selection based on observation window projection analysis is proposed. This method projects the spatial relative relationships of the SODLC observation blind zone, observation range, and the initial spatial position of the objects onto the surface of the earth for detectable analysis of satellites and targets and binds the dynamic observation conditions to the satellite trajectory after projection calculation of the visible relationship between target changes. On this basis, combined with the features of SODLC with high orbital symmetry, the task satellite selection is divided into two steps: orbit plane selection and task satellite selection. The orbit planes are selected based on the longitude range of the ascending node with the geographic location of the targets, and the task satellites are selected according to the relative motion relationship between the satellites and the targets together with the constraints of observable conditions. The selection method simplifies the calculation process of scheduling and selecting task satellites. Simulation analysis prove the method has better task satellite selection efficiency. The method has high practical value for task planning and scheduling for event-driven SODLC. Full article
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20 pages, 9327 KiB  
Article
Air Traffic Management during Rare Events Such as a Pandemic: Paris Charles de Gaulle Case Study
by Paolo Scala, Miguel Mujica Mota and Daniel Delahaye
Aerospace 2021, 8(6), 155; https://doi.org/10.3390/aerospace8060155 - 29 May 2021
Cited by 2 | Viewed by 4139
Abstract
Paris Charles de Gaulle Airport was the second European airport in terms of traffic in 2019, having transported 76.2 million passengers. Its large infrastructures include four runways, a large taxiway network, and 298 aircraft parking stands (131 contact) among three terminals. With the [...] Read more.
Paris Charles de Gaulle Airport was the second European airport in terms of traffic in 2019, having transported 76.2 million passengers. Its large infrastructures include four runways, a large taxiway network, and 298 aircraft parking stands (131 contact) among three terminals. With the current pandemic in place, the European air traffic network has declined by −65% flights when compared with 2019 traffic (pre-COVID-19), having a severe negative impact on the aviation industry. More and more often taxiways and runways are used as parking spaces for aircraft as consequence of the drastic decrease in air traffic. Furthermore, due to safety reasons, passenger terminals at many airports have been partially closed. In this work we want to study the effect of the reduction in the physical facilities at airports on airspace and airport capacity, especially in the Terminal Manoeuvring Area (TMA) airspace, and in the airport ground side. We have developed a methodology that considers rare events such as the current pandemic, and evaluates reduced access to airport facilities, considers air traffic management restrictions and evaluates the capacity of airport ground side and airspace. We built scenarios based on real public information on the current use of the airport facilities of Paris Charles de Gaulle Airport and conducted different experiments based on current and hypothetical traffic recovery scenarios. An already known optimization metaheuristic was implemented for optimizing the traffic with the aim of avoiding airspace conflicts and avoiding capacity overloads on the ground side. The results show that the main bottleneck of the system is the terminal capacity, as it starts to become congested even at low traffic (35% of 2019 traffic). When the traffic starts to increase, a ground delay strategy is effective for mitigating airspace conflicts; however, it reveals the need for additional runways. Full article
(This article belongs to the Special Issue Aircraft Operations and CNS/ATM)
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19 pages, 1884 KiB  
Article
A Web-Based Decision Support System for Aircraft Dispatch and Maintenance
by Hemmo Koornneef, Wim J. C. Verhagen and Richard Curran
Aerospace 2021, 8(6), 154; https://doi.org/10.3390/aerospace8060154 - 28 May 2021
Cited by 3 | Viewed by 4335
Abstract
Aircraft dispatch involves determining the optimal dispatch option when an aircraft experiences an unexpected failure. Currently, maintenance technicians at the apron have limited access to support information and finding the right information in extensive maintenance manuals is a time-consuming task, often leading to [...] Read more.
Aircraft dispatch involves determining the optimal dispatch option when an aircraft experiences an unexpected failure. Currently, maintenance technicians at the apron have limited access to support information and finding the right information in extensive maintenance manuals is a time-consuming task, often leading to technically induced delays. This paper introduces a novel web-based prototype decision support system to aid technicians during aircraft dispatch decision-making and subsequent maintenance execution. A system architecture for real-time dispatch decision support is established and implemented. The developed system is evaluated through a case study in an operational environment by licensed maintenance technicians. The system fully automates information retrieval from multiple data sources, performs alternative identification and evaluation for a given fault message, and provides the technician with on-site access to relevant information, including the related maintenance tasks. The case study indicates a potential time saving of up to 98% per dispatch decision. Moreover, it enables digitalization of the—currently mostly paper-based—dispatch decision process, thereby reducing logistics and paper waste. The prototype is the first to provide operational decision support in the aircraft maintenance domain and addresses the lack of correlation between theory and practice often found in decision support systems research by providing a representative case study. The developed custom parser for SGML-based documents enables efficient identification and extraction of relevant information, vastly contributing to the overall reduction of the decision time. Full article
(This article belongs to the Special Issue Digitalization and Decision Support in Aerospace Maintenance Applications)
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22 pages, 5123 KiB  
Article
From the Martian Surface to Its Low Orbit in a Reusable Single-Stage Vehicle—Charon
by Jérémie Gaffarel, Afrasiab Kadhum, Mohammad Fazaeli, Dimitrios Apostolidis, Menno Berger, Lukas Ciunaitis, Wieger Helsdingen, Lasse Landergren, Mateusz Lentner, Jonathan Neeser, Luca Trotta and Marc Naeije
Aerospace 2021, 8(6), 153; https://doi.org/10.3390/aerospace8060153 - 28 May 2021
Viewed by 6325
Abstract
With Mars colonisation becoming a reality for the near future, it is of importance to analyse how crew and cargo can be transported between Earth and a colony on Mars. This article is a feasibility and design study of a launch vehicle whose [...] Read more.
With Mars colonisation becoming a reality for the near future, it is of importance to analyse how crew and cargo can be transported between Earth and a colony on Mars. This article is a feasibility and design study of a launch vehicle whose mission is to shuttle crew and cargo from Low Mars Orbit to a colony on the Martian surface. A single-stage reusable rocket has been selected to fulfil this mission, code-named Charon. The mission profile of such a vehicle was created, leading to a Maximum Growth Allowance (MGA) Delta-V budget of 6.2 km/s. With the mission profile in mind, each subsystem underwent a preliminary design. With reliability and maintainability in mind, subsystems were designed for redundancy and modularity, and an abort system was included for an added level of safety. The iterative design process resulted in a vehicle with a MGA mass of 198.7 tons, capable of transporting 1200 kg of cargo and a crew of 6 people to a 500 km orbit and back. The preliminary design of the vehicle is deemed safe. Following a fault tree analysis, the Single Launch Loss of Mission, Vehicle and Crew (SL-LOM, SL-LOV, SL-LOC) probabilities are computed to be of 0.975%, 0.12%, and 0.079%. Finally, from the vehicle’s constraints on the base, the feasibility of the project has been reflected upon. It is deemed that such a concept is of high interest only when the base is already operational, due to the launch and maintenance infrastructure that it requires, as well as the power it requires from the Martian base. Full article
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20 pages, 1979 KiB  
Article
Probabilistic Flight Delay Predictions Using Machine Learning and Applications to the Flight-to-Gate Assignment Problem
by Micha Zoutendijk and Mihaela Mitici
Aerospace 2021, 8(6), 152; https://doi.org/10.3390/aerospace8060152 - 28 May 2021
Cited by 32 | Viewed by 9731
Abstract
The problem of flight delay prediction is approached most often by predicting a delay class or value. However, the aviation industry can benefit greatly from probabilistic delay predictions on an individual flight basis, as these give insight into the uncertainty of the delay [...] Read more.
The problem of flight delay prediction is approached most often by predicting a delay class or value. However, the aviation industry can benefit greatly from probabilistic delay predictions on an individual flight basis, as these give insight into the uncertainty of the delay predictions. Therefore, in this study, two probabilistic forecasting algorithms, Mixture Density Networks and Random Forest regression, are applied to predict flight delays at a European airport. The algorithms estimate well the distribution of arrival and departure flight delays with a Mean Absolute Error of less than 15 min. To illustrate the utility of the estimated delay distributions, we integrate these probabilistic predictions into a probabilistic flight-to-gate assignment problem. The objective of this problem is to increase the robustness of flight-to-gate assignments. Considering probabilistic delay predictions, our proposed flight-to-gate assignment model reduces the number of conflicted aircraft by up to 74% when compared to a deterministic flight-to-gate assignment model. In general, the results illustrate the utility of considering probabilistic forecasting for robust airport operations’ optimization. Full article
(This article belongs to the Special Issue Application of Data Science to Aviation)
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20 pages, 5063 KiB  
Article
Numerical Investigation on the Thermal Behaviour of a LOx/LCH4 Demonstrator Cooling System
by Daniele Ricci, Francesco Battista and Manrico Fragiacomo
Aerospace 2021, 8(6), 151; https://doi.org/10.3390/aerospace8060151 - 27 May 2021
Cited by 9 | Viewed by 3098
Abstract
Reliability of liquid rocket engines is strictly connected with the successful operation of cooling jackets, able to sustain the impressive operative conditions in terms of huge thermal and mechanical loads, generated in thrust chambers. Cryogenic fuels, like methane or hydrogen, are often used [...] Read more.
Reliability of liquid rocket engines is strictly connected with the successful operation of cooling jackets, able to sustain the impressive operative conditions in terms of huge thermal and mechanical loads, generated in thrust chambers. Cryogenic fuels, like methane or hydrogen, are often used as coolants and they may behave as transcritical fluids flowing in the jackets: after injection in a liquid state, a phase pseudo-change occurs along the chamber because of the heat released by combustion gases and coolants exiting as a vapour. Thus, in the development of such subsystems, important issues are focused on numerical methodologies adopted to simulate the fluid thermal behaviour inside the jackets, design procedures as well as manufacturing and technological process topics. The present paper includes the numerical thermal analyses regarding the cooling jacket belonging to the liquid oxygen/liquid methane demonstrator, realized in the framework of the HYPROB (HYdrocarbon PROpulsion test Bench) program. Numerical results considering the nominal operating conditions of cooling jackets in the methane-fuelled mode and the water-fed one are included in the case of the application of electrodeposition process for manufacturing. A comparison with a similar cooling jacket, realized through the conventional brazing process, is addressed to underline the benefits of the application of electrodeposition technology. Full article
(This article belongs to the Special Issue Advances in Computational Methodologies for Aerospace Propulsion)
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24 pages, 11702 KiB  
Article
Novel Structure and Thermal Design and Analysis for CubeSats in Formation Flying
by Yeon-Kyu Park, Geuk-Nam Kim and Sang-Young Park
Aerospace 2021, 8(6), 150; https://doi.org/10.3390/aerospace8060150 - 26 May 2021
Cited by 12 | Viewed by 6122
Abstract
The CANYVAL-C (CubeSat Astronomy by NASA and Yonsei using a virtual telescope alignment for coronagraph) is a space science demonstration mission that involves taking several images of the solar corona with two CubeSats—1U CubeSat (Timon) and 2U CubeSat (Pumbaa)—in formation flying. In this [...] Read more.
The CANYVAL-C (CubeSat Astronomy by NASA and Yonsei using a virtual telescope alignment for coronagraph) is a space science demonstration mission that involves taking several images of the solar corona with two CubeSats—1U CubeSat (Timon) and 2U CubeSat (Pumbaa)—in formation flying. In this study, we developed and evaluated structural and thermal designs of the CubeSats Timon and Pumbaa through finite element analyses, considering the nonlinearity effects of the nylon wire of the deployable solar panels installed in Pumbaa. On-orbit thermal analyses were performed with an accurate analytical model for a visible camera on Timon and a micro propulsion system on Pumbaa, which has a narrow operating temperature range. Finally, the analytical models were correlated for enhancing the reliability of the numerical analysis. The test results indicated that the CubeSats are structurally safe with respect to the launch environment and can activate each component under the space thermal environment. The natural frequency of the nylon wire for the deployable solar panels was found to increase significantly as the wire was tightened strongly. The conditions of the thermal vacuum and cycling testing were implemented in the thermal analytical model, which reduced the differences between the analysis and testing. Full article
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24 pages, 14536 KiB  
Article
Innovative Mechanical Design Strategy for Actualizing 80 kg-Class X-Band Active SAR Small Satellite of S-STEP
by Seong-Cheol Kwon, Ji-Hae Son, Sung-Chan Song, Jin-Han Park, Kyung-Rae Koo and Hyun-Ung Oh
Aerospace 2021, 8(6), 149; https://doi.org/10.3390/aerospace8060149 - 26 May 2021
Cited by 18 | Viewed by 7532
Abstract
The Small SAR Technology Experimental Project (S-STEP) mission aims to develop a new (space-based 80 kg-class active X-band synthetic aperture radar (SAR)) satellite with a main imaging mode of 1 m resolution stripmap. In the S-STEP mission, to achieve the design goal of [...] Read more.
The Small SAR Technology Experimental Project (S-STEP) mission aims to develop a new (space-based 80 kg-class active X-band synthetic aperture radar (SAR)) satellite with a main imaging mode of 1 m resolution stripmap. In the S-STEP mission, to achieve the design goal of developing faster, cheaper, better, and lighter small SAR satellite systems, innovative thermo-mechanical design approaches have been proposed and investigated. The major design approaches are the bus-payload integrated flat plate-type structure, multifunctional transmit/receive (TR) module, and dedicated vibration-free orbit deployer (VFOD) with the function of whole spacecraft vibration isolation. To validate the feasibility of the innovative mechanical design of S-STEP, a structural analysis considering launch and on-orbit environments is performed. In addition, development test results are presented to confirm the effectiveness of the proposed design approach for VFOD. Full article
(This article belongs to the Special Issue New Space: Advances in Space Science and Engineering)
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23 pages, 1225 KiB  
Article
Numerical and Experimental Investigation of Longitudinal Oscillations in Hall Thrusters
by Vittorio Giannetti, Manuel Martín Saravia, Luca Leporini, Simone Camarri and Tommaso Andreussi
Aerospace 2021, 8(6), 148; https://doi.org/10.3390/aerospace8060148 - 26 May 2021
Cited by 10 | Viewed by 3865
Abstract
One of the main oscillatory modes found ubiquitously in Hall thrusters is the so-called breathing mode. This is recognized as a relatively low-frequency (10–30 kHz), longitudinal oscillation of the discharge current and plasma parameters. In this paper, we present a synergic experimental and [...] Read more.
One of the main oscillatory modes found ubiquitously in Hall thrusters is the so-called breathing mode. This is recognized as a relatively low-frequency (10–30 kHz), longitudinal oscillation of the discharge current and plasma parameters. In this paper, we present a synergic experimental and numerical investigation of the breathing mode in a 5 kW-class Hall thruster. To this aim, we propose the use of an informed 1D fully-fluid model to provide augmented data with respect to available experimental measurements. The experimental data consists of two datasets, i.e., the discharge current signal and the local near-plume plasma properties measured at high-frequency with a fast-diving triple Langmuir probe. The model is calibrated on the discharge current signal and its accuracy is assessed by comparing predictions against the available measurements of the near-plume plasma properties. It is shown that the model can be calibrated using the discharge current signal, which is easy to measure, and that, once calibrated, it can predict with reasonable accuracy the spatio-temporal distributions of the plasma properties, which would be difficult to measure or estimate otherwise. Finally, we describe how the augmented data obtained through the combination of experiments and calibrated model can provide insight into the breathing mode oscillations and the evolution of plasma properties. Full article
(This article belongs to the Special Issue Advances in Computational Methodologies for Aerospace Propulsion)
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17 pages, 10528 KiB  
Article
Study on Film Cooling Performance of Round Hole Embedded in Different Shaped Craters and Trenches
by Xiaojun Wu, Xin Du and Chunhua Wang
Aerospace 2021, 8(6), 147; https://doi.org/10.3390/aerospace8060147 - 25 May 2021
Cited by 3 | Viewed by 2607
Abstract
Film cooling effectiveness can be improved significantly by embedding a round hole in trenches or craters. In this study, film cooling performances of a transverse trench, W-shaped trench and elliptic trench were compared and analyzed in detail. The CFD models for trench film [...] Read more.
Film cooling effectiveness can be improved significantly by embedding a round hole in trenches or craters. In this study, film cooling performances of a transverse trench, W-shaped trench and elliptic trench were compared and analyzed in detail. The CFD models for trench film cooling were established and validated via the experimental results. Inside the transverse trench, a pair of recirculating vortices is formed, which promotes the coolant spreading in a lateral direction. The decrease of trench width and increase of trench depth both improve the film cooling effectiveness of the transverse trench. For the W-shaped trench, the guide effect of the corner angle further improves the lateral spreading capability of coolant and generates higher cooling effectiveness than a transverse trench with the same depth and width. The flow characteristics of the elliptic trench are similar to that of the round hole, and the kidney vortex pair takes a dominant role in the flow fields downstream of the coolant exit. Accordingly, the elliptic trench generates the worst cooling performance in these shaped trenches. The increase of trench depth and decrease of trench width both result in an increase of the discharge coefficient for trench film cooling. For the W-shaped trench, the increase of the corner angle causes a decrease of the discharge coefficient. For the elliptic trench, the discharge coefficient increases with the decrease of the elliptic aspect ratio (major axis/minor axis). Full article
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24 pages, 4309 KiB  
Article
Monte Carlo Predictions of Aero-Engine Performance Degradation Due to Particle Ingestion
by Matthew Ellis, Nicholas Bojdo, Antonio Filippone and Rory Clarkson
Aerospace 2021, 8(6), 146; https://doi.org/10.3390/aerospace8060146 - 25 May 2021
Cited by 17 | Viewed by 4937
Abstract
Aero-engines, which encounter clouds of airborne particulate, experience reduced performance due to the deposition of particles on their high-pressure turbine nozzle guide vanes. The rate of this degradation depends on particle properties, engine operating state and the duration of exposure to the particle [...] Read more.
Aero-engines, which encounter clouds of airborne particulate, experience reduced performance due to the deposition of particles on their high-pressure turbine nozzle guide vanes. The rate of this degradation depends on particle properties, engine operating state and the duration of exposure to the particle cloud, variables that are often unknown or poorly constrained, leading to uncertainty in model predictions. A novel method coupling one-dimensional gas turbine performance analysis with generalised predictions of particle deposition is developed and applied through the use of Monte Carlo simulations to better predict high-pressure turbine degradation. This enables a statistical analysis of deterioration from which mean performance losses and confidence intervals can be defined, allowing reductions in engine life and increased operational risk to be quantified. The method is demonstrated by replicating two particle cloud encounter events for the Rolls-Royce RB211-524C engine and is used to predict empirical particle properties by correlating measured engine performance data with Monte Carlo model inputs. Potential improvements in the confidence of these predictions due to more tightly constrained input and validation data are also demonstrated. Finally, the potential combination of the Monte Carlo coupled degradation model with in-service engine performance data and particle properties determined through remote or in situ sensing is outlined and its role in a digital twin to enable a predictive approach to operational capability is discussed. Full article
(This article belongs to the Special Issue Life Cycle Modeling of Aircraft Propulsion Systems)
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18 pages, 5993 KiB  
Article
Engineering Comprehensive Model of Complex Wind Fields for Flight Simulation
by Jianwei Chen, Liangming Wang, Jian Fu and Zhiwei Yang
Aerospace 2021, 8(6), 145; https://doi.org/10.3390/aerospace8060145 - 24 May 2021
Cited by 2 | Viewed by 5031
Abstract
A complex wind field refers to the typical atmospheric disturbance phenomena existing in nature that have a great influence on the flight of aircrafts. Aimed at the issues involving large volume of data, complex computations and a single model in the current wind [...] Read more.
A complex wind field refers to the typical atmospheric disturbance phenomena existing in nature that have a great influence on the flight of aircrafts. Aimed at the issues involving large volume of data, complex computations and a single model in the current wind field simulation approaches for flight environments, based on the essential principles of fluid mechanics, in this paper, wind field models for two kinds of wind shear such as micro-downburst and low-level jet plus three-dimensional atmospheric turbulence are established. The validity of the models is verified by comparing the simulation results from existing wind field models and the measured data. Based on the principle of vector superposition, three wind field models are combined in the ground coordinate system, and a comprehensive model of complex wind fields is established with spatial location as the input and wind velocity as the output. The model is applied to the simulated flight of a rocket projectile, and the change in the rocket projectile’s flight attitude and flight trajectory under different wind fields is analyzed. The results indicate that the comprehensive model established herein can reasonably and efficiently reflect the influence of various complex wind field environments on the flight process of aircrafts, and that the model is simple, extensible, and convenient to use. Full article
(This article belongs to the Special Issue Aircraft Modeling for Design, Simulation and Control)
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