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Aerospace, Volume 6, Issue 9 (September 2019)

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Cover Story (view full-size image) Electromechanical actuators are progressively replacing older technologies in aircraft flight [...] Read more.
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Open AccessArticle
Dot Product Equality Constrained Attitude Determination from Two Vector Observations: Theory and Astronautical Applications
Aerospace 2019, 6(9), 102; https://doi.org/10.3390/aerospace6090102 - 12 Sep 2019
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Abstract
In this paper, the attitude determination problem from two vector observations is revisited, incorporating the redundant equality constraint obtained by the dot product of vector observations. Analytical solutions to this constrained attitude determination problem are derived. It is found out that the studied [...] Read more.
In this paper, the attitude determination problem from two vector observations is revisited, incorporating the redundant equality constraint obtained by the dot product of vector observations. Analytical solutions to this constrained attitude determination problem are derived. It is found out that the studied two-vector attitude determination problem by Davenport q-method under the dot product constraint has deterministic maximum eigenvalue, which leads to its advantage in error/perturbation analysis and covariance determination. The proposed dot product constrained two-vector attitude solution is applied then to solve several engineering problems. Detailed simulations on spacecrafts attitude determination indicate the efficiency of the proposed theory. Full article
(This article belongs to the Special Issue Spacecraft Attitude Determination and Control)
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Open AccessArticle
Design of a Reduced SpaceFibre Interface: An Enabling Technology for Low-Cost Spacecraft High-Speed Data-Handling
Aerospace 2019, 6(9), 101; https://doi.org/10.3390/aerospace6090101 - 11 Sep 2019
Viewed by 338
Abstract
SpaceFibre is an upcoming on-board high-speed communication protocol for space applications. It has been developed in collaboration with the European Space Agency to answer the growing data-rate requirement of satellite payloads such as Synthetic Aperture Radars or hyper-spectral imagers. SpaceFibre offers a complete [...] Read more.
SpaceFibre is an upcoming on-board high-speed communication protocol for space applications. It has been developed in collaboration with the European Space Agency to answer the growing data-rate requirement of satellite payloads such as Synthetic Aperture Radars or hyper-spectral imagers. SpaceFibre offers a complete set of features (i.e., Fault Detection, Isolation and Recovery, and Quality of Service) that guarantees robust communication at the price of higher complexity. This article proposes an innovative modified implementation of the SpaceFibre standard: R-SpaceFibre. It has been designed to reduce hardware resources while keeping high data-rate capability and flow control. Attention is given to the trade-off between Data link layer complexity reduction and protocol features. The proposed protocol is particularly suitable in scenarios where very low bit error rate is foreseen and data integrity is not critical, for example in imaging instruments. The main advantage is a reduction of more than 40% of logical resources required per single interface. R-SpaceFibre may be a suitable solution for several applications, such as low earth orbit CubeSats, which have strict requirements in terms of available logic resources, mass, volume and cost, and more relaxed constraints in terms of upset immunity. Full article
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Open AccessArticle
Trajectory Optimization of Extended Formation Flights for Commercial Aviation
Aerospace 2019, 6(9), 100; https://doi.org/10.3390/aerospace6090100 - 09 Sep 2019
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This paper presents a trajectory optimization study that has been conducted using a recently developed tool for the synthesis and analysis of extended flight formations of long-haul commercial aircraft, with the aim to minimize overall fuel consumption. In extended flight formations, trailing aircraft [...] Read more.
This paper presents a trajectory optimization study that has been conducted using a recently developed tool for the synthesis and analysis of extended flight formations of long-haul commercial aircraft, with the aim to minimize overall fuel consumption. In extended flight formations, trailing aircraft can attain an appreciable reduction in induced drag and associated reduction in fuel burn by flying in the upwash of the lead aircraft’s wake. In the present study, a previously developed multi-phase optimal control (MOC) framework for the synthesis of two-ship flight formations has been extended to include the assembly of three-ship flight formations. Using the extended tool, various numerical experiments have been conducted in relation to the assembly of two-ship and three-ship flight formations in long-haul operations across the North-Atlantic Ocean. Additionally, numerical experiments have been carried out to examine the impact of wind fields on the synthesis and performance of flight formations. Additionally, a parametric investigation has been conducted to assess the sensitivity of the solutions with respect to the degree of the induced drag reduction that might be attained by the trailing aircraft in a formation. The results of the various numerical experiments reveal that formation flight can result in appreciable reductions in fuel burn in comparison to flying solo—particularly when larger formation strings are permitted. Full article
(This article belongs to the Special Issue Aircraft Trajectory Design and Optimization)
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Open AccessArticle
Validation of a Test Platform to Qualify Miniaturized Electric Propulsion Systems
Aerospace 2019, 6(9), 99; https://doi.org/10.3390/aerospace6090099 - 04 Sep 2019
Viewed by 351
Abstract
Miniaturized electric propulsion systems are one of the main technologies that could increase interest in CubeSats for future space missions. However, the integration of miniaturized propulsion systems in modern CubeSat platforms presents some issues due to the mutual interactions in terms of power [...] Read more.
Miniaturized electric propulsion systems are one of the main technologies that could increase interest in CubeSats for future space missions. However, the integration of miniaturized propulsion systems in modern CubeSat platforms presents some issues due to the mutual interactions in terms of power consumption, chemical contamination and generated thermal and electro-magnetic environments. The present paper deals with the validation of a flexible test platform to assess the interaction of propulsion systems with CubeSat-technologies from mechanical, electrical, magnetic, and chemical perspectives. The test platform is a 6U CubeSat hosting an electric propulsion system and able to manage a variety of electric propulsion systems. The platform can regulate and distribute electric power (up to 60 W), exchange data according to several protocols (e.g., CAN bus, UART, I2C, SPI), and provide different mechanical layouts in 4U box completely dedicated to the propulsion system. Moreover, the data gathered by the onboard sensors are combined with the data from external devices and tools providing unprecedented information about the mutual behavior of a CubeSat platform and an electric propulsion system. Full article
(This article belongs to the Special Issue Verification Approaches for Nano- and Micro-Satellites)
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Open AccessArticle
Non-Symmetric Gyroscope Skewed Pyramids
Aerospace 2019, 6(9), 98; https://doi.org/10.3390/aerospace6090098 - 04 Sep 2019
Cited by 1 | Viewed by 316
Abstract
The novel contribution in this manuscript is an expansion of the current state-of-the-art in the geometric installation of control moment gyroscopes beyond the benchmark symmetric skewed arrays and the four asymmetric arrays presented in recent literature. The benchmark pyramid symmetrically skewed at 54.73 [...] Read more.
The novel contribution in this manuscript is an expansion of the current state-of-the-art in the geometric installation of control moment gyroscopes beyond the benchmark symmetric skewed arrays and the four asymmetric arrays presented in recent literature. The benchmark pyramid symmetrically skewed at 54.73 degrees mandates significant attention to singularity avoidance, escape, and penetration, while the most recent four asymmetric arrays are strictly useful in instances where space is available to mount at least one gyro orthogonal to the others. Skewed arrays of gyros and the research-benchmark are introduced, followed by the present-day box-90 and “roof” configurations, where the roof configuration is the first prevalently used asymmetric geometry. Six other asymmetric options in the most recent literature are introduced, where four of the six options are obviously quite useful. From this inspiration, several dozen discrete options for asymmetric installations are critically evaluated using two figures of merit: maximum momentum (saturation) and maximum singularity-free momentum. Furthermore, continuous surface plots are presented to provide readers with countless (infinite) options for geometric installations. The manuscript firmly establishes many useful options for engineers who learn that the physical space on their spacecraft is insufficient to permit standard installations. Full article
(This article belongs to the Special Issue Spacecraft Attitude Determination and Control)
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Open AccessArticle
Thermal Numerical Analysis of the Primary Composite Structure of a CubeSat
Aerospace 2019, 6(9), 97; https://doi.org/10.3390/aerospace6090097 - 04 Sep 2019
Viewed by 441
Abstract
A thermal computational analysis for the composite structure of a CubeSat is presented. The main purpose of this investigation is to study the thermal performance of carbon fibre/epoxy resin composite materials with Zinc Oxide nanoparticles in order to be used in the panels [...] Read more.
A thermal computational analysis for the composite structure of a CubeSat is presented. The main purpose of this investigation is to study the thermal performance of carbon fibre/epoxy resin composite materials with Zinc Oxide nanoparticles in order to be used in the panels of the primary structure of a CubeSat. The radiative heat fluxes over each composite panel are computed according to the orbit trajectory and they are utilized as boundary conditions for the analysis. The direct solar, albedo and Earth infrared radiation fluxes are considered in this study. The model implementation, including the computation of the orthotropic thermal conductivity of the composite material is presented. The thermal simulations were performed for three different orbit inclination angles: the selected mission ( β = 57 ), the worst hot ( β = 90 ) and the worst cold ( β = 0 ). The temperature ranges in the electronic boards are analyzed in order to show that are into the operating limits of each electronic component. Full article
(This article belongs to the Special Issue Verification Approaches for Nano- and Micro-Satellites)
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Open AccessArticle
A Test-Bed For Measuring UAS Servo Reliability
Aerospace 2019, 6(9), 96; https://doi.org/10.3390/aerospace6090096 - 03 Sep 2019
Viewed by 385
Abstract
Extant literature suggests minimal research on the reliability of Commercial off-the-shelf (COTS) components used in fabricating non-military Unmanned Aerial System (UAS). Stochastic failures of components during operational cycles over time poses a safety hazard to flight operations. The purpose of the study was [...] Read more.
Extant literature suggests minimal research on the reliability of Commercial off-the-shelf (COTS) components used in fabricating non-military Unmanned Aerial System (UAS). Stochastic failures of components during operational cycles over time poses a safety hazard to flight operations. The purpose of the study was to critically assess the operational performance standards (reliability) of a laboratory designed UAS component test-bed operated using real-world data collected from a Boeing Scan Eagle® UAS aileron servo unit via a flight data recorder. The study hypothesized that the test-bed’s reliability, in terms of a measured encoder output of commanded servo positions, will not be significantly different after double and triple periods of time for continuous operations compared to a base-line mean position. Results suggested that test-bed operated within reliability criteria for a baseline period but there were significant differences in the mean of the reliability after the operational cycles were doubled and tripled in time. This study adds to paucity of extant research on UAS COTS reliability and recommends further studies on reliability of other small UAS components within periods of time. Full article
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Open AccessArticle
Development of a Head Injury Criteria-Compliant Aircraft Seat by Design of Experiments
Aerospace 2019, 6(9), 95; https://doi.org/10.3390/aerospace6090095 - 03 Sep 2019
Viewed by 499
Abstract
This paper deals with the redesign of an aircraft passenger seat, placed at the first seat row, which was not compliant with Federal Aviation Regulations FAR 25.562 “Emergency landing dynamic conditions” regulation (due to a high value for the Head Injury Criterion (HIC)) [...] Read more.
This paper deals with the redesign of an aircraft passenger seat, placed at the first seat row, which was not compliant with Federal Aviation Regulations FAR 25.562 “Emergency landing dynamic conditions” regulation (due to a high value for the Head Injury Criterion (HIC)) and related guidelines. Starting from an accurate analysis of some results obtained via an experimental seat sled test, a numerical procedure was developed in order to improve the passenger safety with respect to head injury. Specifically, the proposed numerical procedure, using the advantages of a Finite Element (FE) model and a Design of Experiment (DoE) approach for simulation modeling, was aimed at identifying a new design solution to avoid the impact between the passenger’s head and the bulkhead. The redesign of the passenger seat was validated against an experimental test carried out at Geven S.p.A. Company by demonstrating, consequently, the compliance of the modified seat-belt system with the regulations. Full article
(This article belongs to the Special Issue Crashworthiness Design for Aviation Safety)
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Open AccessArticle
Model-Based Fault Detection and Identification for Prognostics of Electromechanical Actuators Using Genetic Algorithms
Aerospace 2019, 6(9), 94; https://doi.org/10.3390/aerospace6090094 - 31 Aug 2019
Viewed by 497
Abstract
Traditional hydraulic servomechanisms for aircraft control surfaces are being gradually replaced by newer technologies, such as Electro-Mechanical Actuators (EMAs). Since field data about reliability of EMAs are not available due to their recent adoption, their failure modes are not fully understood yet; therefore, [...] Read more.
Traditional hydraulic servomechanisms for aircraft control surfaces are being gradually replaced by newer technologies, such as Electro-Mechanical Actuators (EMAs). Since field data about reliability of EMAs are not available due to their recent adoption, their failure modes are not fully understood yet; therefore, an effective prognostic tool could help detect incipient failures of the flight control system, in order to properly schedule maintenance interventions and replacement of the actuators. A twofold benefit would be achieved: Safety would be improved by avoiding the aircraft to fly with damaged components, and replacement of still functional components would be prevented, reducing maintenance costs. However, EMA prognostic presents a challenge due to the complexity and to the multi-disciplinary nature of the monitored systems. We propose a model-based fault detection and isolation (FDI) method, employing a Genetic Algorithm (GA) to identify failure precursors before the performance of the system starts being compromised. Four different failure modes are considered: dry friction, backlash, partial coil short circuit, and controller gain drift. The method presented in this work is able to deal with the challenge leveraging the system design knowledge in a more effective way than data-driven strategies, and requires less experimental data. To test the proposed tool, a simulated test rig was developed. Two numerical models of the EMA were implemented with different level of detail: A high fidelity model provided the data of the faulty actuator to be analyzed, while a simpler one, computationally lighter but accurate enough to simulate the considered fault modes, was executed iteratively by the GA. The results showed good robustness and precision, allowing the early identification of a system malfunctioning with few false positives or missed failures. Full article
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Open AccessArticle
Optimization Provenance of Whiplash Compensation for Flexible Space Robotics
Aerospace 2019, 6(9), 93; https://doi.org/10.3390/aerospace6090093 - 30 Aug 2019
Cited by 1 | Viewed by 476
Abstract
Automatic controls refer to the application of control theory to regulate systems or processes without human intervention, and the notion is often usefully applied to space applications. A key part of controlling flexible space robotics is the control-structures interaction of a light, flexible [...] Read more.
Automatic controls refer to the application of control theory to regulate systems or processes without human intervention, and the notion is often usefully applied to space applications. A key part of controlling flexible space robotics is the control-structures interaction of a light, flexible structure whose first resonant modes lie within the bandwidth of the controller. In this instance, the designed-control excites the problematic resonances of the highly flexible structure. This manuscript reveals a novel compensator capable of minimum-time performance of an in-plane maneuver with zero residual vibration (ZV) and zero residual vibration-derivative (ZVD) at the end of the maneuver. The novel compensator has a whiplash nature of first commanding maneuver states in the opposite direction of the desired end state. For a flexible spacecraft simulator (FSS) free-floating planar robotic arm, this paper will first derive the model of the flexible system in detail from first principles. Hamilton’s principle is augmented with the adjoint equation to produce the Euler–Lagrange equation which is manipulated to prove equivalence with Newton’s law. Extensive efforts are expended modeling the free–free vibration equations of the flexible system, and this extensive modeling yields an unexpected control profile—a whiplash compensator. Equations of motion are derived using both the Euler–Lagrange method and Newton’s law as validation. Variables are then scaled for efficient computation. Next, general purposed pseudospectral optimization software is used to seek an optimal control, proceeding afterwards to validate optimality via six theoretical optimization necessary conditions: (1) Hamiltonian minimization condition; (2) adjoint equations; (3) terminal transversality condition; (4) Hamiltonian final value condition; (5) Hamiltonian evolution equation; and lastly (6) Bellman’s principle. The results are novel and unique in that they initially command full control in the opposite direction from the desired end state, while no such results are seen using classical control methods including classical methods augmented with structural filters typically employed for controlling highly flexible multi-body systems. The manuscript also opens an interesting question of what to declare when the six optimality necessary conditions are not necessarily in agreement (we choose here not to declare finding the optimal control, instead calling it suboptimal). Full article
(This article belongs to the Special Issue Control and Optimization Problems in Aerospace Engineering)
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Open AccessEditorial
Special Issue: Aeroelasticity
Aerospace 2019, 6(9), 92; https://doi.org/10.3390/aerospace6090092 - 23 Aug 2019
Viewed by 585
Abstract
Aeroelasticity belongs to the larger family of fluid-structure interaction problems that are characterized by the interplay between a fluid and deforming body [...] Full article
(This article belongs to the Special Issue Aeroelasticity)
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