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Volume 7
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Aerospace, Volume 7, Issue 8 (August 2020) – 17 articles

Cover Story (view full-size image): The inductive pulsed plasma thruster (IPPT) represents a promising and scalable technology for electric propulsion that could be extremely useful in the mission planning trade space due to a demonstrated ability to achieve high efficiency over a range of specific impulse values and to operate over a wide input power range. An IPPT pulses high current through an inductor, producing an electromagnetic field that drives current in a plasma, expelling it at high speed. The IPPT is electrodeless, eliminating electrode erosion found in other electric thrusters and making operation possible in a wide range of propellants. View this paper
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25 pages, 5205 KiB  
Article
Aerostructural Design Exploration of a Wing in Transonic Flow
by Nicolas P. Bons and Joaquim R. R. A. Martins
Aerospace 2020, 7(8), 118; https://doi.org/10.3390/aerospace7080118 - 14 Aug 2020
Cited by 14 | Viewed by 4409
Abstract
Multidisciplinary design optimization (MDO) has been previously applied to aerostructural wing design problems with great success. Most previous applications involve fine-tuning a well-designed aircraft wing. In this work, we broaden the scope of the optimization problem by exploring the design space of aerostructural [...] Read more.
Multidisciplinary design optimization (MDO) has been previously applied to aerostructural wing design problems with great success. Most previous applications involve fine-tuning a well-designed aircraft wing. In this work, we broaden the scope of the optimization problem by exploring the design space of aerostructural wing design optimization. We start with a rectangular wing and optimize the aerodynamic shape and the sizing of the internal structure to achieve minimum fuel burn on a transonic cruise mission. We use a multi-level optimization procedure to decrease computational cost by 40%. We demonstrate that the optimization can transform the rectangular wing into a swept, tapered wing typical of a transonic aircraft. The optimizer converges to the same wing shape when starting from a different initial design. Additionally, we use a separation constraint at a low-speed, high-lift condition to improve the off-design performance of the optimized wing. The separation constraint results in a substantially different wing design with better low-speed performance and only a slight decrease in cruise performance. Full article
(This article belongs to the Special Issue Aeroelasticity, Volume II)
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2 pages, 129 KiB  
Editorial
Postscript for Special Issue “Advances in Hybrid Rocket Technology and Related Analysis Methodologies”
by Carmine Carmicino
Aerospace 2020, 7(8), 117; https://doi.org/10.3390/aerospace7080117 - 14 Aug 2020
Viewed by 1948
Abstract
Since the Editorial [...] Full article
(This article belongs to the Special Issue Advances in Hybrid Rocket Technology and Related Analysis Methodologies)
26 pages, 11509 KiB  
Article
Identification of Fixed-Wing Micro Aerial Vehicle Aerodynamic Derivatives from Dynamic Water Tunnel Tests
by Krzysztof Sibilski, Mirosław Nowakowski, Dariusz Rykaczewski, Paweł Szczepaniak, Andrzej Żyluk, Anna Sibilska-Mroziewicz, Michał Garbowski and Wiesław Wróblewski
Aerospace 2020, 7(8), 116; https://doi.org/10.3390/aerospace7080116 - 13 Aug 2020
Cited by 10 | Viewed by 3987
Abstract
A micro air vehicle (MAV) is a class of miniature unmanned aerial vehicles that has a size restriction and may be autonomous. Fixed-wing MAVs are very attractive for outdoor surveillance missions since they generally offer better payload and endurance capabilities than rotorcraft or [...] Read more.
A micro air vehicle (MAV) is a class of miniature unmanned aerial vehicles that has a size restriction and may be autonomous. Fixed-wing MAVs are very attractive for outdoor surveillance missions since they generally offer better payload and endurance capabilities than rotorcraft or flapping-wing vehicles of equal size. This research paper describes the methodology applying indicial function theory and artificial neural networks for identification of aerodynamic derivatives for fixed-wing MAV. The formulation herein proposed extends well- known aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to strake wing planforms. Using results from dynamic water tunnel tests and indicial functions approach allowed to identify MAV aerodynamic derivatives. The experiments were conducted in a water tunnel in the course of dynamic tests of periodic oscillatory motion. The tests program range was set at high angles of attack and a wide scope of reduced frequencies of angular movements. Due to a built-in propeller, the model’s structure test program was repeated for a turned-on propelled drive system. As a result of these studies, unsteady aerodynamics characteristics and aerodynamic derivatives of the micro-aircraft were identified as functions of state parameters. At the Warsaw University of Technology and the Air Force Institute of Technology, a “Bee” fixed wings micro aerial vehicle with an innovative strake-wing outline and a propeller placed in the wing gap was worked. This article is devoted to the problems of identification of aerodynamic derivatives of this micro-aircraft. The result of this research was the identification of the aerodynamic derivatives of the fixed wing MAV “Bee” as non-linear functions of the angle of attack, and reduced frequency. The identification was carried out using the indicial function approach. Full article
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19 pages, 925 KiB  
Article
Unsupervised Anomaly Detection in Flight Data Using Convolutional Variational Auto-Encoder
by Milad Memarzadeh, Bryan Matthews and Ilya Avrekh
Aerospace 2020, 7(8), 115; https://doi.org/10.3390/aerospace7080115 - 08 Aug 2020
Cited by 59 | Viewed by 9714
Abstract
The modern National Airspace System (NAS) is an extremely safe system and the aviation industry has experienced a steady decrease in fatalities over the years. This is in part due the airlines, manufacturers, FAA, and research institutions all continually working to improve the [...] Read more.
The modern National Airspace System (NAS) is an extremely safe system and the aviation industry has experienced a steady decrease in fatalities over the years. This is in part due the airlines, manufacturers, FAA, and research institutions all continually working to improve the safety of the operations. However, the current approach for identifying vulnerabilities in NAS operations leverages domain expertise using knowledge about how the system should behave within the expected tolerances to known safety margins. This approach works well when the system has a well-defined operating condition. However, the operations in the NAS can be highly complex with various nuances that render it difficult to assess risk based on pre-defined safety vulnerabilities. Moreover, state-of-the-art machine learning models that are developed for event detection in aerospace data usually rely on supervised learning. However, in many real-world problems, such as flight safety, creating labels for the data requires specialized expertise that is time consuming and therefore largely impractical. To address this challenge, we develop a Convolutional Variational Auto-Encoder (CVAE), an unsupervised deep generative model for anomaly detection in high-dimensional time-series data. Validating on Yahoo’s benchmark data as well as a case study of identifying anomalies in commercial flights’ take-offs, we show that CVAE outperforms both classic and deep learning-based approaches in precision and recall of detecting anomalies. Full article
(This article belongs to the Special Issue Machine Learning Applications in Aviation Safety)
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10 pages, 1371 KiB  
Technical Note
Oxygen–Methane Torch Ignition System for Aerospace Applications
by Olexiy Shynkarenko and Domenico Simone
Aerospace 2020, 7(8), 114; https://doi.org/10.3390/aerospace7080114 - 07 Aug 2020
Cited by 2 | Viewed by 4800
Abstract
A new ignition system, based on a CH4/O2 torch has been developed by the Chemical Propulsion Laboratory of the University of Brasilia. Designed to ignite a hybrid rocket, this device has been improved to be used in testing of solid [...] Read more.
A new ignition system, based on a CH4/O2 torch has been developed by the Chemical Propulsion Laboratory of the University of Brasilia. Designed to ignite a hybrid rocket, this device has been improved to be used in testing of solid and liquid ramjet engines under development in our lab. The capability to provide multiple ignitions and to cool-down its combustion chamber walls by using a swirled injection of the oxidizer, along with a very low weight to power ratio, makes this device versatile. The igniter is controlled by a feedback system, developed by our group, which guarantees the possibility of operating in different design conditions enabling, therefore, complete integration with systems of different nature. The main characteristics of the igniter and the design solutions are presented including some considerations about the tests performed to evaluate the quality and performance of the ignition system. Full article
(This article belongs to the Special Issue Advances in Hybrid Rocket Technology and Related Analysis Methodologies)
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18 pages, 1336 KiB  
Article
Multi-Axis Inputs for Identification of a Reconfigurable Fixed-Wing UAV
by Piotr Lichota
Aerospace 2020, 7(8), 113; https://doi.org/10.3390/aerospace7080113 - 05 Aug 2020
Cited by 15 | Viewed by 3355
Abstract
Designing a reconfiguration system for an aircraft requires a good mathematical model of the object. An accurate model describing the aircraft dynamics can be obtained from system identification. In this case, special maneuvers for parameter estimation must be designed, as the reconfiguration algorithm [...] Read more.
Designing a reconfiguration system for an aircraft requires a good mathematical model of the object. An accurate model describing the aircraft dynamics can be obtained from system identification. In this case, special maneuvers for parameter estimation must be designed, as the reconfiguration algorithm may require to use flight controls separately, even if they usually work in pairs. The simultaneous multi-axis multi-step input design for reconfigurable fixed-wing aircraft system identification is presented in this paper. D-optimality criterion and genetic algorithm were used to design the flight controls deflections. The aircraft model was excited with those inputs and its outputs were recorded. These data were used to estimate stability and control derivatives by using the maximum likelihood principle. Visual match between registered and identified outputs as well as relative standard deviations were used to validate the outcomes. The system was also excited with simultaneous multisine inputs and its stability and control derivatives were estimated with the same approach as earlier in order to assess the multi-step design. Full article
(This article belongs to the Special Issue Flight Simulation)
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24 pages, 10037 KiB  
Article
A Comparison of Isolated and Ducted Fixed-Pitch Propellers under Non-Axial Inflow Conditions
by Michael Cerny and Christian Breitsamter
Aerospace 2020, 7(8), 112; https://doi.org/10.3390/aerospace7080112 - 03 Aug 2020
Cited by 7 | Viewed by 6573
Abstract
A strong interest in highly-efficient, small-scale propeller configurations can be recognized, especially due to the currently growing number of and usage possibilities for unmanned aerial vehicles (UAVs). Although a variety of different propulsion concepts already exist on the market or are discussed in [...] Read more.
A strong interest in highly-efficient, small-scale propeller configurations can be recognized, especially due to the currently growing number of and usage possibilities for unmanned aerial vehicles (UAVs). Although a variety of different propulsion concepts already exist on the market or are discussed in the literature, there is still a demand for a systematic investigation to compare such configurations, in particular, small-scale propellers with a fixed pitch, which are analyzed in this work. Therefore, different configurations of small-scale propellers with a fixed pitch are analyzed in this paper. They were operated as isolated single propellers and as ducted propellers in a cylindrical wing. Furthermore, due to their flight envelope, UAVs are likely to operate at highly inclined inflow conditions and even under reverse inflow. These non-axial inflow conditions have a major influence on the flow field around a propeller. In order to investigate this influence, all analyses were performed at a range of inflow angles in relation to the propeller axis from αdisc=0° to 180°. Full article
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14 pages, 4005 KiB  
Article
Numerical/Experimental Validation of Thin-Walled Composite Box Beam Optimal Design
by Enrico Cestino, Giacomo Frulla, Paolo Piana and Renzo Duella
Aerospace 2020, 7(8), 111; https://doi.org/10.3390/aerospace7080111 - 31 Jul 2020
Cited by 2 | Viewed by 3793
Abstract
Thin-walled composite box beam structural configuration is representative of a specific high aspect ratio wing structure. The optimal design procedure and lay-up definition including appropriate coupling necessary for aerospace applications has been identified by means of “ad hoc” analytical formulation and by application [...] Read more.
Thin-walled composite box beam structural configuration is representative of a specific high aspect ratio wing structure. The optimal design procedure and lay-up definition including appropriate coupling necessary for aerospace applications has been identified by means of “ad hoc” analytical formulation and by application of commercial code. The overall equivalent bending, torsional and coupled stiffness are derived and the accuracy of the simplified beam model is demonstrated by the application of Altair Optistruct. A simple case of a coupled cantilevered beam with load at one end is introduced to demonstrate that stiffness and torsion angle distribution does not always correspond to the trends that one would intuitively expect. The maximum of torsional stiffness is not obtained with fibers arranged at 45° and, at the maximum torsional stiffness, there is no minimum rotation angle. This observation becomes essential in any design process of composite structures where the constraints impose structural couplings. Furthermore, the presented theory is also extended to cases in which it is necessary to include composite/stiffened hybrid configurations. Good agreement has been found between the theoretical simplified beam model and numerical analysis. Finally, the selected composite configuration was compared to an experimental test case. The numerical and experimental validation is presented and discussed. A good correlation was found confirming the validity of the overall optimization for the optimal lay-up selection and structural configuration. Full article
(This article belongs to the Special Issue Aeroelasticity, Volume II)
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21 pages, 2541 KiB  
Article
Dynamic Lifecycle Cost Modeling for Adaptable Design Optimization of Additively Remanufactured Aeroengine Components
by Lydia Lawand, Massimo Panarotto, Petter Andersson, Ola Isaksson and Michael Kokkolaras
Aerospace 2020, 7(8), 110; https://doi.org/10.3390/aerospace7080110 - 31 Jul 2020
Cited by 10 | Viewed by 3462
Abstract
Additive manufacturing (AM) is being used increasingly for repair and remanufacturing of aeroengine components. This enables the consideration of a design margin approach to satisfy changing requirements, in which component lifespan can be optimized for different lifecycle scenarios. This paradigm requires lifecycle cost [...] Read more.
Additive manufacturing (AM) is being used increasingly for repair and remanufacturing of aeroengine components. This enables the consideration of a design margin approach to satisfy changing requirements, in which component lifespan can be optimized for different lifecycle scenarios. This paradigm requires lifecycle cost (LCC) modeling; however, the LCC models available in the literature consider mostly the manufacturing of a component, not its repair or remanufacturing. There is thus a need for an LCC model that can consider AM for repair/remanufacturing to quantify corresponding costs and benefits. This paper presents a dynamic LCC model that estimates cumulative costs over the in-service phase and a nested design optimization problem formulation that determines the optimal component lifespan range to minimize overall cost while maximizing performance. The developed methodology is demonstrated by means of an aeroengine turbine rear structure. Full article
(This article belongs to the Special Issue Ageing Aircraft and Additive Manufacturing)
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15 pages, 495 KiB  
Article
Plant Model-Based Fault Detection during Aircraft Takeoff Using Non-Deterministic Finite-State Automata
by Ferdinand Settele, Alexander Weber and Alexander Knoll
Aerospace 2020, 7(8), 109; https://doi.org/10.3390/aerospace7080109 - 31 Jul 2020
Cited by 2 | Viewed by 2643
Abstract
In this note, the application of a plant model-based fault detection method for nonlinear control systems on aircraft takeoff is introduced. This method utilizes non-deterministic finite-state automata, which approximate the fault-free dynamics of the plant. The aforementioned automaton is computed in a preliminary [...] Read more.
In this note, the application of a plant model-based fault detection method for nonlinear control systems on aircraft takeoff is introduced. This method utilizes non-deterministic finite-state automata, which approximate the fault-free dynamics of the plant. The aforementioned automaton is computed in a preliminary step while during evolution of the plant the automaton is continually evaluated to detect discrepancies between the actual and the nominal dynamics. In this way the fault detection module itself can be implemented on simpler hardware on board of the plant. Moreover, an implementation technique is presented that allows the use of the proposed fault detection method when the plant dynamics is given only by means of a graphical programming script. The great potential and practicality of the used method are demonstrated on a simulated takeoff manoeuvre of a battery-electrically driven aircraft. Full article
(This article belongs to the Special Issue Fault Detection and Prognostics in Aerospace Engineering)
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18 pages, 889 KiB  
Article
Lifetime Considerations for Electrospray Thrusters
by Anirudh Thuppul, Peter L. Wright, Adam L. Collins, John K. Ziemer and Richard E. Wirz
Aerospace 2020, 7(8), 108; https://doi.org/10.3390/aerospace7080108 - 29 Jul 2020
Cited by 39 | Viewed by 6309
Abstract
Ionic liquid electrospray thrusters are capable of producing microNewton precision thrust at a high thrust–power ratio but have yet to demonstrate lifetimes that are suitable for most missions. Accumulation of propellant on the extractor and accelerator grids is thought to be the most [...] Read more.
Ionic liquid electrospray thrusters are capable of producing microNewton precision thrust at a high thrust–power ratio but have yet to demonstrate lifetimes that are suitable for most missions. Accumulation of propellant on the extractor and accelerator grids is thought to be the most significant life-limiting mechanism. In this study, we developed a life model to examine the effects of design features, operating conditions, and emission properties on the porous accelerator grid saturation time of a thruster operating in droplet emission mode. Characterizing a range of geometries and operating conditions revealed that modifying grid aperture radius and grid spacing by 3–7% can significantly improve thruster lifetime by 200–400%, though a need for explicit mass flux measurement was highlighted. Tolerance analysis showed that misalignment can result in 20–50% lifetime reduction. In addition, examining the impact of electron backstreaming showed that increasing aperture radius produces a significant increase in backstreaming current compared to changing grid spacing. A study of accelerator grid bias voltages revealed that applying a reasonably strong accelerator grid potential (in the order of a kV) can minimize backstreaming current to negligible levels for a range of geometries. Full article
(This article belongs to the Special Issue Electric Propulsion)
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28 pages, 14790 KiB  
Article
Comparative Analysis and Optimization of Technical and Weight Parameters of Turbo-Electric Propulsion Systems
by Mykhaylo Filipenko, Stefan Biser, Martin Boll, Matthias Corduan, Mathias Noe and Peter Rostek
Aerospace 2020, 7(8), 107; https://doi.org/10.3390/aerospace7080107 - 27 Jul 2020
Cited by 16 | Viewed by 5736
Abstract
According to Flightpath 2050, the aviation industry is aiming to substantially reduce emissions over the coming decades. One possible solution to meet these ambitious goals is by moving to hybrid-electric drivetrain architectures which require the electric components to be extremely lightweight and efficient [...] Read more.
According to Flightpath 2050, the aviation industry is aiming to substantially reduce emissions over the coming decades. One possible solution to meet these ambitious goals is by moving to hybrid-electric drivetrain architectures which require the electric components to be extremely lightweight and efficient at the same time. It has been claimed in several publications that cryogenic and in particular superconducting components can help to fulfill such requirements that potentially cannot be achieved with non-cryogenic components. The purpose of this work was to make a fair comparison between a cryogenic turbo-electric propulsion system (CEPS) and a non-cryogenic turbo-electric propulsion system (TEPS) on a quantitative level. The results on the CEPS were presented in detail in a previous publication. The focus of this publication is to present the study on the TEPS, which in conclusion allows a direct comparison. For both systems the same top-level aircraft requirements were used that were derived within the project TELOS based on an exemplary mission profile and the physical measures of a 220-passenger aircraft. Our study concludes that a CEPS could be 10% to 40% lighter than a TEPS. Furthermore, a CEPS could have a total efficiency gain of up to 18% compared to a similar TEPS. Full article
(This article belongs to the Special Issue Hybrid-Electric Distributed-Propulsion Aircraft)
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16 pages, 864 KiB  
Article
Static Aeroelastic Beam Model Development for Folding Winglet Design
by Bereket Sitotaw Kidane and Enrico Troiani
Aerospace 2020, 7(8), 106; https://doi.org/10.3390/aerospace7080106 - 25 Jul 2020
Cited by 4 | Viewed by 5061
Abstract
Wing shape adaptability during flight is the next step towards the greening of aviation. The shape of the wing is typically designed for one cruise point or a weighted average of several cruise points. However, a wing is subjected to a variety of [...] Read more.
Wing shape adaptability during flight is the next step towards the greening of aviation. The shape of the wing is typically designed for one cruise point or a weighted average of several cruise points. However, a wing is subjected to a variety of flight conditions, which results in the aircraft flying sub-optimally during a portion of the flight. Shape adaptability can be achieved by tuning the shape of the winglet during flight. The design challenge is to combine a winglet structure that is able to allow the required adaptable shape while preserving the structural integrity to carry the aerodynamic loads. The shape changing actuators must work against the structural strains and the aerodynamic loads. Analyzing the full model in the preliminary design phase is computationally expensive; therefore, it is necessary to develop a model. The goal of this paper is to derive an aeroelastic model for a wing and winglet in order to reduce the computational cost and complexity of the system in designing a folding winglet. In this paper, the static aeroelastic analysis is performed for a regional aircraft wing at sea level and service ceiling conditions with three degree and eight degree angle of attack. MSC Nastran Aeroelastic tool is used to develop a Finite Element Model (FEM), i.e., beam model and the aerodynamic loads are calculated based on a doublet lattice panel method (DLM). Full article
(This article belongs to the Special Issue Aeroelasticity, Volume II)
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67 pages, 10190 KiB  
Review
State-of-the-Art and Advancement Paths for Inductive Pulsed Plasma Thrusters
by Kurt Polzin, Adam Martin, Justin Little, Curtis Promislow, Benjamin Jorns and Joshua Woods
Aerospace 2020, 7(8), 105; https://doi.org/10.3390/aerospace7080105 - 24 Jul 2020
Cited by 22 | Viewed by 7569
Abstract
An inductive pulsed plasma thruster (IPPT) operates by pulsing high current through an inductor, typically a coil of some type, producing an electromagnetic field that drives current in a plasma, accelerating it to high speed. The IPPT is electrodeless, with no direct electrical [...] Read more.
An inductive pulsed plasma thruster (IPPT) operates by pulsing high current through an inductor, typically a coil of some type, producing an electromagnetic field that drives current in a plasma, accelerating it to high speed. The IPPT is electrodeless, with no direct electrical connection between the externally applied pulsed high-current circuit and the current conducted in the plasma. Several different configurations were proposed and tested, including those that produce a plasma consisting of an accelerating current sheet and those that use closed magnetic flux lines to help confine the plasma during acceleration. Specific impulses up to 7000 s and thrust efficiencies over 50% have been measured. The present state-of-the-art for IPPTs is reviewed, focusing on the operation, modeling techniques, and major subsystems found in various configurations. Following that review is documentation of IPPT technology advancement paths that were proposed or considered. Full article
(This article belongs to the Special Issue Electric Propulsion)
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25 pages, 836 KiB  
Article
OpenAP: An Open-Source Aircraft Performance Model for Air Transportation Studies and Simulations
by Junzi Sun, Jacco M. Hoekstra and Joost Ellerbroek
Aerospace 2020, 7(8), 104; https://doi.org/10.3390/aerospace7080104 - 23 Jul 2020
Cited by 57 | Viewed by 11212
Abstract
Air traffic simulations serve as common practice to evaluate different concepts and methods for air transportation studies. The aircraft performance model is a key element that supports these simulation-based studies. It is also an important component for simulation-independent studies, such as air traffic [...] Read more.
Air traffic simulations serve as common practice to evaluate different concepts and methods for air transportation studies. The aircraft performance model is a key element that supports these simulation-based studies. It is also an important component for simulation-independent studies, such as air traffic optimization and prediction studies. Commonly, contemporary studies have to rely on proprietary aircraft performance models that restrict the redistribution of the data and code. To promote openness and research comparability, an alternative open performance model would be beneficial for the air transportation research community. In this paper, we introduce an open aircraft performance model (OpenAP). It is an open-source model that is based on a number of our previous studies, which were focused on different components of the aircraft performance. The unique characteristic of OpenAP is that it was built upon open aircraft surveillance data and open literature models. The model is composed of four main components, including aircraft and engine properties, kinematic performances, dynamic performances, and utility libraries. Alongside the performance model, we are publishing an open-source toolkit to facilitate the use of this model. The main objective of this paper is to describe each main component, their connections, and how they can be used for simulation and research in practice. Finally, we analyzed the performance of OpenAP by comparing it with an existing performance model and sample flight data. Full article
(This article belongs to the Collection Air Transportation—Operations and Management)
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11 pages, 2267 KiB  
Article
Thermoelastic Response of Closed Cylindrical Shells in a Supersonic Gas Flow
by Marine Mikilyan
Aerospace 2020, 7(8), 103; https://doi.org/10.3390/aerospace7080103 - 22 Jul 2020
Cited by 3 | Viewed by 2502
Abstract
The work is devoted to the investigation of flutter oscillations and the stability of the closed cylindrical shell in supersonic gas flow in an inhomogeneous temperature field. It is assumed that supersonic gas flows on the outside of the shell with an unperturbed [...] Read more.
The work is devoted to the investigation of flutter oscillations and the stability of the closed cylindrical shell in supersonic gas flow in an inhomogeneous temperature field. It is assumed that supersonic gas flows on the outside of the shell with an unperturbed velocity U, directed parallel to the cylinder generatrix. Under the action of an inhomogeneous temperature field the shell bulges out, this deformed state is accepted as unperturbed, and the stability of this state is studied. The main nonlinear equations and relationships describing the behavior of the examined system are derived. The formulated boundary value problem is solved using the Galerkin method. The joint influence of the flow and the temperature field on the relationship between the amplitude of nonlinear oscillations of a cylindrical shell and the speed of the flowing stream is studied. The critical velocity values are calculated from the corresponding linear system and are given in tables. The numerical results show that: (a) the surrounding flow significantly affects the nature of the investigated relationship; (b) a certain interval of supersonic velocity exists where it is impossible to excite steady-state flutter oscillations (the silence zone); (c) the dependence of amplitude on the supersonic velocity can be either multivalued or single-valued. Full article
(This article belongs to the Special Issue Aeroelasticity, Volume II)
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13 pages, 5401 KiB  
Communication
Hybrid System Combining Ice-Phobic Coating and Electrothermal Heating for Wing Ice Protection
by Katsuaki Morita, Shigeo Kimura and Hirotaka Sakaue
Aerospace 2020, 7(8), 102; https://doi.org/10.3390/aerospace7080102 - 22 Jul 2020
Cited by 20 | Viewed by 5401
Abstract
In-flight icing for aircraft is a large concern for all those involved in aircraft operations. Generally, an electric heater has been used to prevent in-flight icing. A hybrid anti-icing system combining ice-phobic coating and electrothermal heating (ICE-WIPS) has been proposed by the Japan [...] Read more.
In-flight icing for aircraft is a large concern for all those involved in aircraft operations. Generally, an electric heater has been used to prevent in-flight icing. A hybrid anti-icing system combining ice-phobic coating and electrothermal heating (ICE-WIPS) has been proposed by the Japan Aerospace Exploration Agency (JAXA) to reduce the power consumption in the heating unit. In order to validate the effectiveness of ICE-WIPS, validation and demonstration tests are conducted using icing wind tunnels at the Kanagawa Institute of Technology (KAIT) and at the Icing Research Tunnel in the NASA Glenn Research Center. Using a NACA0012 airfoil as a test model, ICE-WIPS demonstrates substantial reduction in power consumption as compared to the existing heating system. The reduction depends on the in-flight icing conditions; more than a 70% reduction is achieved at a liquid-water content (LWC) of 0.6 g/m3 and a median-volume diameter (MVD) of 15 μm at 75 m/s with zero angle of attack. In wet-icing conditions, more than a 30% reduction in power is achieved. Full article
(This article belongs to the Special Issue Deicing and Anti-Icing of Aircraft)
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