Aerospace

18 pages, 2052 KiB

Open AccessArticle

A Multi-Fidelity Approach for Aerodynamic Performance Computations of Formation Flight

by Diwakar Singh, Antonios F. Antoniadis^*, Panagiotis Tsoutsanis, Hyo-Sang Shin

, Antonios Tsourdos

, Samuel Mathekga and Karl W. Jenkins

School of Aerospace, Transport and Manufacturing, Cranfield University, Cranfield, Bedfordshire MK43 0AL, UK

Aerospace 2018, 5(2), 66; https://doi.org/10.3390/aerospace5020066 - 15 Jun 2018

Cited by 13 | Viewed by 8185

Abstract

This paper introduces a multi-fidelity computational framework for the analysis of aerodynamic performance of flight formation. The Vortex Lattice and Reynolds Averaged Navier–Stokes methods form the basis of the framework, as low- and high-fidelity, respectively. Initially, the computational framework is validated for an [...] Read more.

This paper introduces a multi-fidelity computational framework for the analysis of aerodynamic performance of flight formation. The Vortex Lattice and Reynolds Averaged Navier–Stokes methods form the basis of the framework, as low- and high-fidelity, respectively. Initially, the computational framework is validated for an isolated wing, and then two rectangular NACA23012 wings are considered for assessing the aerodynamic performance of this formation; the optimal relative position is through the multi-fidelity framework based on the total drag reduction. The performance estimates are in good agreement with experimental measurements of the same configuration. Total aerodynamic performance of formation flight is also assessed with respect to attitude variations of the lifting bodies involved. The framework is also employed to determine the optimal position of blended-wing-body unmanned aerial vehicles in tandem formation flight. Full article

(This article belongs to the Special Issue Computational Aerodynamic Modeling of Aerospace Vehicles)

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9 pages, 4083 KiB

Open AccessArticle

Development of Bio-Sourced Epoxies for Bio-Composites

by Xiao-Su Yi^1,2,*, Xvfeng Zhang^2,†, Fangbo Ding^3,† and Jianfeng Tong^2,†

¹ Advanced Materials and Composites Department, Faculty of Science & Engineering, University of Nottingham (UNNC), Ningbo 315100, China

² AVIC Composite Corporation Ltd. (ACC), Beijing 101300, China

³ AVIC XAC, Commercial Aircraft Co., Ltd., Xi’an 710000, China

^† These authors contributed equally to this work.

Aerospace 2018, 5(2), 65; https://doi.org/10.3390/aerospace5020065 - 15 Jun 2018

Cited by 12 | Viewed by 6939

Abstract

In the air and ground transportation sectors, new environmental regulations and societal concerns have triggered a search for new products and processes that complement resources and the environment. To address these issues, this article reports on current R&D efforts to develop bio-sourced materials [...] Read more.

In the air and ground transportation sectors, new environmental regulations and societal concerns have triggered a search for new products and processes that complement resources and the environment. To address these issues, this article reports on current R&D efforts to develop bio-sourced materials by an international joint project. Novel bio-sourced epoxies and biocomposites were developed, characterized, modified and evaluated in terms of the mechanical property levels. Quasi-structural composite parts were finally trial-manufactured and demonstrated. Full article

(This article belongs to the Special Issue ECO-COMPASS: Ecological and Multifunctional Composites for Application in Aircraft Interior and Secondary Structures)

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15 pages, 13553 KiB

Open AccessArticle

ReDSHIFT: A Global Approach to Space Debris Mitigation

by Alessandro Rossi^1,*

, Camilla Colombo², Kleomenis Tsiganis³

, James Beck⁴, Jonathan Becedas Rodriguez⁵, Scott Walker⁶, Federico Letterio⁷

, Florio Dalla Vedova⁸, Volker Schaus⁹

, Rada Popova¹⁰, Alessandro Francesconi¹¹, Hedley Stokes¹², Thorn Schleutker¹³

, Elisa Maria Alessi¹

, Giulia Schettino¹

, Ioannis Gkolias²

, Despoina K. Skoulidou³, Ian Holbrough⁴, Franco Bernelli Zazzera²

, Enrico Stoll⁹

and Youngkyu Kim¹⁰ Show full author list Hide full author list

¹ IFAC-CNR, 50019 Sesto Fiorentino (FI), Italy

² Dipartimento di Scienze e Tecnologie Aerospaziali, Politecnico di Milano, 20156 Milano, Italy

³ Department of Physics, Section Astrophysics, Astronomy and Mechanics, Aristotle University, 54006 Thessaloniki, Greece

⁴ Belstead Research Ltd., Ashford TN25 4PF, UK

⁵ Elecnor Deimos Satellite Systems, 13500 Puertollano, Spain

⁶ Astronautics Research Group, University of Southampton, Southampton SO17 1BJ, UK

⁷ Deimos Space, Tres Cantos, 28760 Madrid, Spain

⁸ LuxSpace Sarl, 6832 Betzdorf, Luxemburg

⁹ Institute of Space Systems, Technische Universität Carolo-Wilhemina zu Braunschweig, 38108 Braunschweig, Germany

¹⁰ Institute of Air and Space Law, University of Cologne, 50923 Cologne, Germany

¹¹ Dipartimento di Ingegneria Industriale, University of Padova, 35131 Padova, Italy

¹² PHS Space Ltd., Cerne Abbas DT2 7GW, UK

¹³ DLR (German Aerospace Center), 51147 Koeln, Germany

Show full affiliation list Hide full affiliation list

Aerospace 2018, 5(2), 64; https://doi.org/10.3390/aerospace5020064 - 13 Jun 2018

Cited by 37 | Viewed by 10427

Abstract

The H2020 ReDSHIFT project aims at finding passive means to mitigate the proliferation of space debris. This goal is pursued by a twofold research activity based on theoretical astrodynamics, computer simulations and the analysis of legal aspects of space debris, coupled with an [...] Read more.

The H2020 ReDSHIFT project aims at finding passive means to mitigate the proliferation of space debris. This goal is pursued by a twofold research activity based on theoretical astrodynamics, computer simulations and the analysis of legal aspects of space debris, coupled with an experimental activity on advanced additive manufacturing (3D printing) applied to the production of a novel small satellite. Several different aspects related to the design and production of a debris compliant spacecraft are treated, including shielding, area augmentation devices for deorbiting (solar and drag sails) and design for demise. A strong testing activity, mainly based on design for demise wind tunnel experiments and hypervelocity impacts is performed as well. The main results obtained so far in the project are outlined. Full article

(This article belongs to the Special Issue Space Debris: Impact and Remediation)

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68 pages, 19331 KiB

Open AccessArticle

Design of Power, Propulsion, and Thermal Sub-Systems for a 3U CubeSat Measuring Earth’s Radiation Imbalance

by Jack Claricoats^1,† and Sam M. Dakka^2,*,†

¹ Department of Engineering and Math, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK

² Department of Mechanical, Materials and Manufacturing Engineering, The University of Nottingham, University Park, Nottingham NG7 2RD, UK

^† These authors contributed equally to this work.

Aerospace 2018, 5(2), 63; https://doi.org/10.3390/aerospace5020063 - 11 Jun 2018

Cited by 20 | Viewed by 21214

Abstract

The paper presents the development of the power, propulsion, and thermal systems for a 3U CubeSat orbiting Earth at a radius of 600 km measuring the radiation imbalance using the RAVAN (Radiometer Assessment using Vertically Aligned NanoTubes) payload developed by NASA (National Aeronautics [...] Read more.

The paper presents the development of the power, propulsion, and thermal systems for a 3U CubeSat orbiting Earth at a radius of 600 km measuring the radiation imbalance using the RAVAN (Radiometer Assessment using Vertically Aligned NanoTubes) payload developed by NASA (National Aeronautics and Space Administration). The propulsion system was selected as a Mars-Space PPTCUP -Pulsed Plasma Thruster for CubeSat Propulsion, micro-pulsed plasma thruster with satisfactory capability to provide enough impulse to overcome the generated force due to drag to maintain an altitude of 600 km and bring the CubeSat down to a graveyard orbit of 513 km. Thermal analysis for hot case found that the integration of a black high-emissivity paint and MLI was required to prevent excessive heating within the structure. Furthermore, the power system analysis successfully defined electrical consumption scenarios for the CubeSat’s 600 km orbit. The analysis concluded that a singular 7 W solar panel mounted on a sun-facing side of the CubeSat using a sun sensor could satisfactorily power the electrical system throughout the hot phase and charge the craft’s battery enough to ensure constant electrical operation during the cold phase, even with the additional integration of an active thermal heater. However, when the inevitable end-of-life degradation of the solar cell was factored into the analysis, an approximate power deficit of 2 kJ was found. This was supplemented by additional solar cell integrated into the antenna housing face. Full article

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23 pages, 292 KiB

Open AccessArticle

Differences in Risk Perception Factors and Behaviours amongst and within Professionals and Trainees in the Aviation Engineering Domain

by Dimitrios Chionis^1,*,†

and Nektarios Karanikas^2,†

¹ Department of Psychology, University of Bolton, Bolton BL3 5AB, UK

² Aviation Academy, Amsterdam University of Applied Sciences, 1097 DZ Amsterdam, The Netherlands

^† Both authors contributed equally to writing the paper.

Aerospace 2018, 5(2), 62; https://doi.org/10.3390/aerospace5020062 - 10 Jun 2018

Cited by 18 | Viewed by 8832

Abstract

In the aviation sector, the variability in the appreciation of safety risk perception factors and responses to risk behaviours has not been sufficiently studied for engineers and technicians. Through a questionnaire survey, this study investigated differences amongst professionals and trainees across eleven risk [...] Read more.

In the aviation sector, the variability in the appreciation of safety risk perception factors and responses to risk behaviours has not been sufficiently studied for engineers and technicians. Through a questionnaire survey, this study investigated differences amongst professionals and trainees across eleven risk perception factors and five indicative risk behaviour scenarios. The findings indicated significant differences between the two groups in four factors and three scenarios as well as within groups. Moreover, age, years of work and study and educational level were other factors accounting for such differences within each group of professionals and trainees. The results showing these significant differences are aligned with relevant research about pilots and indicate that the appreciation of risk perception factors by aviation engineers and the development of their risk behaviours deserves more attention. Our findings cannot be generalised due to the small sample and its distribution across the demographic variables. However, the results of this study suggest the need tailoring risk communication and training to address the different degrees to which influences of risk perception factors are comprehended, and risk behaviours emerge in aviation engineering trainees and professionals. Further research could focus on the development of a respective uniform framework and tool for the specific workforce group and could administer surveys to more extensive and more representative samples by including open-ended questions and broader social, organisational and systemic factors. Full article

(This article belongs to the Special Issue Civil and Military Airworthiness: Recent Developments and Challenges)

3 pages, 615 KiB

Open AccessEditorial

Aerospace Best Paper Awards 2017

by Aerospace Editorial Office

MDPI, St. Alban-Anlage 66, 4052 Basel, Switzerland

Aerospace 2018, 5(2), 61; https://doi.org/10.3390/aerospace5020061 - 8 Jun 2018

Viewed by 5096

Abstract

n/a Full article

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18 pages, 6963 KiB

Open AccessReview

Shock-Wave Structure of Supersonic Jet Flows

by Valery Zapryagaev^*

, Nikolay Kiselev and Dmitry Gubanov

Experimental AeroGazDynamics Laboratory, Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk, Russia

Aerospace 2018, 5(2), 60; https://doi.org/10.3390/aerospace5020060 - 7 Jun 2018

Cited by 27 | Viewed by 10947

Abstract

In the present paper, we give a brief overview of the studies of supersonic jet flows which were performed recently with the aim of gaining experimental data on the formation of the shock-wave structure and jet mixing layer in such flows. Considerable attention [...] Read more.

In the present paper, we give a brief overview of the studies of supersonic jet flows which were performed recently with the aim of gaining experimental data on the formation of the shock-wave structure and jet mixing layer in such flows. Considerable attention is paid to a detailed description of discharge conditions for supersonic jets, to enable the use of measured data for making a comparison with numerical calculations. Data on the 3D flow structure in the mixing layer of the initial length of a supersonic jet are reported. Scientific interest in this phenomenon is due to its practical significance in studying the possibility of intensifying the mixing process as well as in studying the sound-generation process. Full article

(This article belongs to the Special Issue Under-Expanded Jets)

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31 pages, 9849 KiB

Open AccessArticle

Uncertainty Management at the Airport Transit View

by Álvaro Rodríguez-Sanz^1,*

, Fernando Gómez Comendador¹

, Rosa Arnaldo Valdés¹

, Jose Manuel Cordero García² and Margarita Bagamanova³

¹ Department of Aerospace Systems, Air Transport and Airports, Universidad Politécnica de Madrid (UPM), Plaza Cardenal Cisneros N3, 28040 Madrid, Spain

² CRIDA A.I.E. (Reference Center for Research, Development and Innovation in ATM), Avenida de Aragón N402 Edificio Allende, 28022 Madrid, Spain

³ Department of Telecommunications and Systems Engineering, Universitat Autònoma de Barcelona (UAB), Carrer de Emprius N2, 08202 Sabadell, Spain

Aerospace 2018, 5(2), 59; https://doi.org/10.3390/aerospace5020059 - 1 Jun 2018

Cited by 7 | Viewed by 9029

Abstract

Air traffic networks, where airports are the nodes that interconnect the entire system, have a time-varying and stochastic nature. An incident in the airport environment may easily propagate through the network and generate system-level effects. This paper analyses the aircraft flow through the [...] Read more.

Air traffic networks, where airports are the nodes that interconnect the entire system, have a time-varying and stochastic nature. An incident in the airport environment may easily propagate through the network and generate system-level effects. This paper analyses the aircraft flow through the Airport Transit View framework, focusing on the airspace/airside integrated operations. In this analysis, we use a dynamic spatial boundary associated with the Extended Terminal Manoeuvring Area concept. Aircraft operations are characterised by different temporal milestones, which arise from the combination of a Business Process Model for the aircraft flow and the Airport Collaborative Decision-Making methodology. Relationships between factors influencing aircraft processes are evaluated to create a probabilistic graphical model, using a Bayesian network approach. This model manages uncertainty and increases predictability, hence improving the system’s robustness. The methodology is validated through a case study at the Adolfo Suárez Madrid-Barajas Airport, through the collection of nearly 34,000 turnaround operations. We present several lessons learned regarding delay propagation, time saturation, uncertainty precursors and system recovery. The contribution of the paper is two-fold: it presents a novel methodological approach for tackling uncertainty when linking inbound and outbound flights and it also provides insight on the interdependencies among factors driving performance. Full article

(This article belongs to the Collection Air Transportation—Operations and Management)

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17 pages, 16452 KiB

Open AccessArticle

Effects of the Back Plate Inner Diameter on the Frictional Heat Input and General Performance of Brush Seals

by Manuel Hildebrandt^1,*,†, Heiko Schwarz^2,†, Corina Schwitzke¹, Hans-Jörg Bauer¹ and Jens Friedrichs²

¹ Institute of Thermal Turbomachinery (ITS), Karlsruhe Institute of Technology, Kaiserstraße 12, 76131 Karlsruhe, Germany

² Institute of Jet Propulsion and Turbomachinery, Technical University Braunschweig, Hermann-Blenk-Str. 37, 38108 Braunschweig, Germany

^† These authors contributed equally to this work.

Aerospace 2018, 5(2), 58; https://doi.org/10.3390/aerospace5020058 - 25 May 2018

Cited by 13 | Viewed by 6624

Abstract

Reducing losses in the secondary air system of gas and steam turbines can significantly increase the efficiency of such machines. Meanwhile, brush seals are a widely used alternative to labyrinth seals. Their most valuable advantage over other sealing concepts is the very small [...] Read more.

Reducing losses in the secondary air system of gas and steam turbines can significantly increase the efficiency of such machines. Meanwhile, brush seals are a widely used alternative to labyrinth seals. Their most valuable advantage over other sealing concepts is the very small gap between the sealing package and the rotor and thus reduced leakage mass flow. This small gap can be achieved due to the great radial flexibility without running the risk of severe detrimental deterioration in case of rubbing. Rubbing between rotor and seal during operation might occur as a result of e.g., an unequal thermal expansion of the rotor and stator or a rotor elongation due to centrifugal forces or manoeuvre forces. Thanks to the flexible structure of the brush seal, the contact forces during a rubbing event are reduced; however, the frictional heat input can still be considerable. Particularly in aircraft engines with their thin and lightweight rotor structures, the permissible material stresses can easily be exceeded by an increased heat input and thus harm the engine’s integrity. The geometry of the seal has a decisive influence on the resulting contact forces and consequently the heat input. This paper is a contribution to further understand the influence of the geometrical parameters of the brush seal on the heat input and the leakage during the rubbing of the seal on the rotor. In this paper, a total of three seals with varied back plate inner diameter are examined in more detail. The experimental tests were carried out on the brush seal test rig of the Institute of Thermal Turbomachinery (ITS) under machine-relevant conditions. These are represented by pressure differences of 1 to 7 bar, surface speeds of 30 to 180 m/s and radial interferences of 0.1 to 0.4 mm. For a better interpretation, the results were compared with those obtained at the static test rig of the Institute of Jet Propulsion and Turbomachinery (IFAS) at the Technical University of Braunschweig. The stiffness, the blow-down and the axial behaviour of the seals as a function of the differential pressure can be examined at this test rig. It could be shown that the back plate inner diameter has a decisive influence on the overall operating behaviour of a brush seal. Full article

(This article belongs to the Special Issue Secondary Air Systems in Gas Turbine Engines)

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11 pages, 8351 KiB

Open AccessArticle

The Random Walk of Cars and Their Collision Probabilities with Planets

by Hanno Rein^1,2,3,*, Daniel Tamayo^1,3,4 and David Vokrouhlický⁵

¹ Department of Physical and Environmental Sciences, University of Toronto at Scarborough, Toronto, ON M1C 1A4, Canada

² Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4, Canada

³ Centre for Planetary Sciences, University of Toronto at Scarborough, Toronto, ON M1C 1A4, Canada

⁴ Canadian Institute for Theoretical Astrophysics, 60 St. George St, University of Toronto, Toronto, ON M5S 3H8, Canada

⁵ Institute of Astronomy, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Prague, Czech Republic

Aerospace 2018, 5(2), 57; https://doi.org/10.3390/aerospace5020057 - 23 May 2018

Cited by 4 | Viewed by 11500

Abstract

On 6 February 2018, SpaceX launched a Tesla Roadster on a Mars-crossing orbit. We perform N-body simulations to determine the fate of the object over the next 15 Myr. The orbital evolution is initially dominated by close encounters with the Earth. While [...] Read more.

On 6 February 2018, SpaceX launched a Tesla Roadster on a Mars-crossing orbit. We perform N-body simulations to determine the fate of the object over the next 15 Myr. The orbital evolution is initially dominated by close encounters with the Earth. While a precise orbit can not be predicted beyond the next several centuries due to these repeated chaotic scatterings, one can reliably predict the long-term outcomes by statistically analyzing a large suite of possible trajectories with slightly perturbed initial conditions. Repeated gravitational scatterings with Earth lead to a random walk. Collisions with the Earth, Venus and the Sun represent primary sinks for the Roadster’s orbital evolution. Collisions with Mercury and Mars, or ejections from the Solar System by Jupiter, are highly unlikely. We calculate a dynamical half-life of the Tesla of approximately 15 Myr, with some 22%, 12% and 12% of Roadster orbit realizations impacting the Earth, Venus, and the Sun within one half-life, respectively. Because the eccentricities and inclinations in our ensemble increase over time due to mean-motion and secular resonances, the impact rates with the terrestrial planets decrease beyond a few million years, whereas the impact rate on the Sun remains roughly constant. Full article

(This article belongs to the Special Issue Space Debris: Impact and Remediation)

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7 pages, 192 KiB

Open AccessEditorial

Aerospace Mission Outcome: Predictive Modeling

by Ephraim Suhir^1,2

¹ Department of Mechanics and Materials, Portland State University, Portland, OR 97207, USA

² Department of Electronic Materials, Technical University, A-1040 Vienna, Austria

Aerospace 2018, 5(2), 56; https://doi.org/10.3390/aerospace5020056 - 22 May 2018

Cited by 3 | Viewed by 4592

Abstract

n/a Full article

(This article belongs to the Special Issue Challenges in Reliability Analysis of Aerospace Electronics)

17 pages, 270 KiB

Open AccessArticle

The Legal Framework for Space Debris Remediation as a Tool for Sustainability in Outer Space

by Rada Popova^1,* and Volker Schaus²

¹ Institute of Air and Space Law, University of Cologne, 50923 Köln, Germany

² Institute of Space Systems, Technische Universität Carolo-Wilhemina zu Braunschweig, 38108 Braunschweig, Germany

Aerospace 2018, 5(2), 55; https://doi.org/10.3390/aerospace5020055 - 9 May 2018

Cited by 28 | Viewed by 13293

Abstract

The growth of orbital space debris is both a consequence of and a potential hindrance to space activities. The risks posed by space debris propagation in the most used orbital regions highlight the need to adequately address the challenges posed to the sustainability [...] Read more.

The growth of orbital space debris is both a consequence of and a potential hindrance to space activities. The risks posed by space debris propagation in the most used orbital regions highlight the need to adequately address the challenges posed to the sustainability in outer space. The preservation of the access to and usability of outer space in the long-term requires that action is taken which has to be the result of both mitigation and remediation measures for existing and future space missions. As the enforcement of such technical measures will depend on adequate regulation, they need to be approached also from a legal perspective. The deficiencies in law for space debris remediation mechanisms originate from the fact that although technical concepts have been developed, the legal framework for space activities does not impose any legal obligations for debris removal and on-orbit servicing. Nevertheless, an overview of the relevant legal framework shows that there is a legal basis for the protection of the outer space environment which can, as has already been the case with space debris mitigation guidelines, be substantiated in more concrete terms by the formulation of voluntary, non-binding instruments and included in national legislation. Full article

(This article belongs to the Special Issue Space Debris: Impact and Remediation)

18 pages, 4179 KiB

Open AccessArticle

Faster Command Input Using the Multimodal Controller Working Position “TriControl”

by Oliver Ohneiser^1,*

, Malte Jauer¹

, Jonathan R. Rein² and Matt Wallace³

¹ German Aerospace Center (DLR), Institute of Flight Guidance, Lilienthalplatz 7, 38108 Braunschweig, Germany

² Federal Aviation Administration (FAA), William J. Hughes Technical Center, Atlantic City International Airport, Egg Harbor Township, NJ 08405, USA

³ Deutsche Flugsicherung GmbH, Academy, Am DFS-Campus, 63225 Langen, Germany

Aerospace 2018, 5(2), 54; https://doi.org/10.3390/aerospace5020054 - 8 May 2018

Cited by 4 | Viewed by 6874

Abstract

TriControl is a controller working position (CWP) prototype developed by German Aerospace Center (DLR) to enable more natural, efficient, and faster command inputs. The prototype integrates three input modalities: speech recognition, eye tracking, and multi-touch sensing. Air traffic controllers may use all three [...] Read more.

TriControl is a controller working position (CWP) prototype developed by German Aerospace Center (DLR) to enable more natural, efficient, and faster command inputs. The prototype integrates three input modalities: speech recognition, eye tracking, and multi-touch sensing. Air traffic controllers may use all three modalities simultaneously to build commands that will be forwarded to the pilot and to the air traffic management (ATM) system. This paper evaluates possible speed improvements of TriControl compared to conventional systems involving voice transmission and manual data entry. 26 air traffic controllers participated in one of two air traffic control simulation sub-studies, one with each input system. Results show potential of a 15% speed gain for multimodal controller command input in contrast to conventional inputs. Thus, the use and combination of modern human machine interface (HMI) technologies at the CWP can increase controller productivity. Full article

(This article belongs to the Collection Air Transportation—Operations and Management)

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17 pages, 4544 KiB

Open AccessArticle

Simulation of Random Events for Air Traffic Applications

by Stéphane Puechmorel^1,*, Guillaume Dufour² and Romain Fèvre³

¹ Ecole nationale de l’aviation civile (ENAC), Université Fédérale de Toulouse, 7 Avenue Edouard Belin, FR-31055 Toulouse CEDEX, France

² Office Nationale d’études et de recherches aérospatiales (ONERA), DTIM, 2 Avenue Edouard Belin, FR-31055 Toulouse CEDEX 4, France

³ Swiss Air Navigation Services Ltd. (Skyguide), Route de Pré-Bois 15-17, CH-1215 Geneva 15, Switzerland

Aerospace 2018, 5(2), 53; https://doi.org/10.3390/aerospace5020053 - 3 May 2018

Cited by 4 | Viewed by 5789

Abstract

Resilience to uncertainties must be ensured in air traffic management. Unexpected events can either be disruptive, like thunderstorms or the famous volcano ash cloud resulting from the Eyjafjallajökull eruption in Iceland, or simply due to imprecise measurements or incomplete knowledge of the environment. [...] Read more.

Resilience to uncertainties must be ensured in air traffic management. Unexpected events can either be disruptive, like thunderstorms or the famous volcano ash cloud resulting from the Eyjafjallajökull eruption in Iceland, or simply due to imprecise measurements or incomplete knowledge of the environment. While human operators are able to cope with such situations, it is generally not the case for automated decision support tools. Important examples originate from the numerous attempts made to design algorithms able to solve conflicts between aircraft occurring during flights. The STARGATE (STochastic AppRoach for naviGATion functions in uncertain Environment) project was initiated in order to study the feasibility of inherently robust automated planning algorithms that will not fail when submitted to random perturbations. A mandatory first step is the ability to simulate the usual stochastic phenomenons impairing the system: delays due to airport platforms or air traffic control (ATC) and uncertainties on the wind velocity. The work presented here will detail algorithms suitable for the simulation task. Full article

(This article belongs to the Collection Air Transportation—Operations and Management)

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22 pages, 7900 KiB

Open AccessArticle

A Dual Mode Propulsion System for Small Satellite Applications

by Kevin R. Gagne^1,‡, M. Ryan McDevitt² and Darren L. Hitt^1,*

¹ Department of Mechanical Engineering, University of Vermont, Burlington, VT 05405, USA

² Benchmark Space Systems Inc., South Burlington, VT 05403, USA

^‡ Current address: Blue Origin, Kent, WA 98032, USA.

Aerospace 2018, 5(2), 52; https://doi.org/10.3390/aerospace5020052 - 2 May 2018

Cited by 15 | Viewed by 11781

Abstract

This study focused on the development of a chemical micropropulsion system suitable for primary propulsion and/or attitude control for a nanosatellite. Due to the limitations and expense of current micropropulsion technologies, few nanosatellites with propulsion have been launched to date; however, the availability [...] Read more.

This study focused on the development of a chemical micropropulsion system suitable for primary propulsion and/or attitude control for a nanosatellite. Due to the limitations and expense of current micropropulsion technologies, few nanosatellites with propulsion have been launched to date; however, the availability of such a propulsion system would allow for new nanosatellite mission concepts, such as deep space exploration, maneuvering in low gravity environments and formation flying. This work describes the design of “dual mode” monopropellant/bipropellant microthruster prototype that employs a novel homogeneous catalysis scheme. Results from prototype testing are reported that validate the concept. The micropropulsion system is designed to be fabricated using a combination of additively-manufactured and commercial off the shelf (COTS) parts along with non-toxic fuels, thus making it a low-cost and environmentally-friendly option for future nanosatellite missions. Full article

(This article belongs to the Special Issue Micro-Propulsion Systems and Components for Small Spacecraft—Current Trends, Innovations and Challenges)

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17 pages, 34725 KiB

Open AccessArticle

Prediction of Heat Transfer in a Jet Cooled Aircraft Engine Compressor Cone Based on Statistical Methods

by Fabian Bleier^*, Corina Schwitzke and Hans-Jörg Bauer

Karlsruhe Institute of Technology (KIT), Institut für Thermische Strömungsmaschinen (ITS), 76131 Karlsruhe, Germany

Aerospace 2018, 5(2), 51; https://doi.org/10.3390/aerospace5020051 - 1 May 2018

Cited by 1 | Viewed by 6605

Abstract

The paper presents the setup and analysis of an experimental study on heat transfer of a jet cooled compressor rear cone with adjacent conical housing. The main goal of the paper is to describe the systematic derivation of empirical correlations for global Nusselt [...] Read more.

The paper presents the setup and analysis of an experimental study on heat transfer of a jet cooled compressor rear cone with adjacent conical housing. The main goal of the paper is to describe the systematic derivation of empirical correlations for global Nusselt numbers to be used in the design process of a jet engine secondary air system. Based on the relevant similarity parameters obtained from literature, operating points are deduced leading to a full factorial design experiment to identify all effects and interactions. The varied similarity parameters are the circumferential Reynolds number, the non-dimensional mass flow, the non-dimensional spacing between rotor and stator, and the jet incidence angle. The range of the varied similarity parameters covers engine oriented operating conditions and is therefore suitable to predict Nusselt numbers in the actual engine component. In order to estimate measurement uncertainties, a simplified model of the test specimen, consisting of a convectively cooled flat plate, has been derived. Uncertainties of the measured quantities and derived properties are discussed by means of a linear propagation of uncertainties. A sensitivity study shows the effects of the input parameters and their interactions on the global Nusselt number. Subsequently, an empirical correlation for the global Nusselt numbers is derived using a multivariate non-linear regression. The quality of the empirical correlation is assessed by means of statistical hypotheses and by a comparison between measured and predicted data. The predicted values show excellent agreement with experimental data. In a wide range, accuracies of 15% can be reached when predicting global Nusselt numbers. Furthermore, the results of the sensitivity study show that pre-swirled cooling air does not have a positive effect on heat transfer. Full article

(This article belongs to the Special Issue Secondary Air Systems in Gas Turbine Engines)

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22 pages, 6370 KiB

Open AccessArticle

Single-Sensor Acoustic Emission Source Localization in Plate-Like Structures Using Deep Learning

by Arvin Ebrahimkhanlou^*

and Salvatore Salamone^*

Smart Structures Research Group (SSRG), Department of Civil Architectural and Environmental Engineering, The University of Texas at Austin, 10100 Burnet Rd, Bldg. 177, Austin, TX 78758, USA

Aerospace 2018, 5(2), 50; https://doi.org/10.3390/aerospace5020050 - 1 May 2018

Cited by 151 | Viewed by 17831

Abstract

This paper introduces two deep learning approaches to localize acoustic emissions (AE) sources within metallic plates with geometric features, such as rivet-connected stiffeners. In particular, a stack of autoencoders and a convolutional neural network are used. The idea is to leverage the reflection [...] Read more.

This paper introduces two deep learning approaches to localize acoustic emissions (AE) sources within metallic plates with geometric features, such as rivet-connected stiffeners. In particular, a stack of autoencoders and a convolutional neural network are used. The idea is to leverage the reflection and reverberation patterns of AE waveforms as well as their dispersive and multimodal characteristics to localize their sources with only one sensor. Specifically, this paper divides the structure into multiple zones and finds the zone in which each source occurs. To train, validate, and test the deep learning networks, fatigue cracks were experimentally simulated by Hsu–Nielsen pencil lead break tests. The pencil lead breaks were carried out on the surface and at the edges of the plate. The results show that both deep learning networks can learn to map AE signals to their sources. These results demonstrate that the reverberation patterns of AE sources contain pertinent information to the location of their sources. Full article

(This article belongs to the Special Issue Selected Papers from IWSHM 2017)

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26 pages, 4793 KiB

Open AccessArticle

Energy-Dynamics Resulting in Turbulent and Acoustic Phenomena in an Underexpanded Jet

by Unnikrishnan Sasidharan Nair^*,†, Kalyan Goparaju^† and Datta Gaitonde^†

¹ Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA

^† These authors contributed equally to this work.

Aerospace 2018, 5(2), 49; https://doi.org/10.3390/aerospace5020049 - 1 May 2018

Cited by 11 | Viewed by 6512

Abstract

Underexpanded jets exhibit interactions between turbulent shear layers and shock-cell trains that yield complex phenomena that are absent in the more commonly studied perfectly expanded jets. We quantitatively analyze these mechanisms by considering the interplay between hydrodynamic (turbulence) and acoustic modes, using a [...] Read more.

Underexpanded jets exhibit interactions between turbulent shear layers and shock-cell trains that yield complex phenomena that are absent in the more commonly studied perfectly expanded jets. We quantitatively analyze these mechanisms by considering the interplay between hydrodynamic (turbulence) and acoustic modes, using a validated large-eddy simulation. Using momentum potential theory (MPT) to achieve energy segregation, the following observations are made. The sharp gradients in fluctuations introduced by the shock-cell structure are captured mostly in the hydrodynamic mode, whose amplitude is an order of magnitude larger than the acoustic mode. The acoustic mode has a relatively smoother distribution, exhibiting a compact wavepacket form. Proper orthogonal decomposition (POD) identifies the third-to-sixth cells as the most dynamic structures. The imprint of shock cells is discernible in the nearfield of the acoustic mode, primarily along the sideline direction. Energy interactions that feed the acoustic mode remain compact in nature, facilitating a simple propagation technique for farfield noise prediction. The farfield sound spectra show peak directivity at 30

^{\circ}

to the downstream axis. The POD modes of the acoustic component also identify two main energetic components in the wavepacket: one representative of the periodic internal structure and the other of intermittent downstream lobes. The latter component occurs at exactly the same frequency as, and displays high correlation with, the farfield peak noise spectra, making the acoustic mode a better predictor of the dynamics than velocity fluctuations. Full article

(This article belongs to the Special Issue Under-Expanded Jets)

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12 pages, 12497 KiB

Open AccessArticle

Interfacing Sail Modules for Use with “Space Tugs”

by Florio Dalla Vedova^1,*, Pierre Morin¹, Thibault Roux¹, Roberta Brombin¹, Alberto Piccinini² and Nigel Ramsden²

¹ LuxSpace S.à.r.l (OHB S.E. Group), Betzdorf 6832, Luxembourg

² FANUC Luxembourg, Echternach 6468, Luxembourg

Aerospace 2018, 5(2), 48; https://doi.org/10.3390/aerospace5020048 - 1 May 2018

Cited by 10 | Viewed by 6615

Abstract

The paper introduces and describes the recent and still ongoing development activities performed in Luxembourg for In-Orbit Attach Mechanisms for (Drag) Sails Modules to be operated from Space Tugs. After some preparatory work aiming at understanding the possible operational aspects and implications [...] Read more.

The paper introduces and describes the recent and still ongoing development activities performed in Luxembourg for In-Orbit Attach Mechanisms for (Drag) Sails Modules to be operated from Space Tugs. After some preparatory work aiming at understanding the possible operational aspects and implications of mating interfaces between these space systems, three possible designs of In-Orbit Attach Mechanisms have been proposed and completed for their 3D (Metal and Plastic) Printing, a new manufacturing technology assessed within this project. The Plastic-printed prototype underwent a series of automated tests in which a robotic arm, equipped with an advanced force sensor, replicated four docking scenarii in ideal and degraded modes. The observation of the forces and torque behaviors at and after impact allowed one to characterize the typical patterns for the various contacts but also, to identify a type of potentially dramatic impact for the safety of the docking and its equipment: in the case of the off-axis approach, “point” contacts shall be avoided, as they instantaneously transfer the total kinetic energy in a small area that could break. Full article

(This article belongs to the Special Issue Space Debris: Impact and Remediation)

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22 pages, 4269 KiB

Open AccessProject Report

Aircraft Geometry and Meshing with Common Language Schema CPACS for Variable-Fidelity MDO Applications

by Mengmeng Zhang^1,*

, Aidan Jungo², Alessandro Augusto Gastaldi¹ and Tomas Melin¹

¹ Airinnova AB, 18248 Stockholm, Sweden

² CFS Engineering, 1015 Lausanne, Switzerland

Aerospace 2018, 5(2), 47; https://doi.org/10.3390/aerospace5020047 - 24 Apr 2018

Cited by 9 | Viewed by 11460

Abstract

This paper discusses multi-fidelity aircraft geometry modeling and meshing with the common language schema CPACS. The CPACS interfaces are described, and examples of variable fidelity aerodynamic analysis results applied to the reference aircraft are presented. Finally, we discuss three control surface deflection models [...] Read more.

This paper discusses multi-fidelity aircraft geometry modeling and meshing with the common language schema CPACS. The CPACS interfaces are described, and examples of variable fidelity aerodynamic analysis results applied to the reference aircraft are presented. Finally, we discuss three control surface deflection models for Euler computation. Full article

(This article belongs to the Special Issue Computational Aerodynamic Modeling of Aerospace Vehicles)

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11 pages, 9423 KiB

Open AccessArticle

The Public Safety Zones around Small and Medium Airports

by Paola Di Mascio^1,†

, Giuseppe Perta^2,†, Giuseppe Cantisani^1,†

and Giuseppe Loprencipe^1,*

¹ Department of Civil, Constructional and Environmental Engineering, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy

² Via Luigi Pirandello, 30, 71042 Cerignola, Italy

^† These authors contributed equally to this work.

Aerospace 2018, 5(2), 46; https://doi.org/10.3390/aerospace5020046 - 23 Apr 2018

Cited by 6 | Viewed by 8208

Abstract

Proper planning around airports safeguards the surrounding territory from risks of air accidents. Many countries have defined Public Safety Zones (PSZs) beyond the runway thresholds as a result of targeted risk assessment methods. Therefore, national aviation Authorities could limit building construction and industrial [...] Read more.

Proper planning around airports safeguards the surrounding territory from risks of air accidents. Many countries have defined Public Safety Zones (PSZs) beyond the runway thresholds as a result of targeted risk assessment methods. Therefore, national aviation Authorities could limit building construction and industrial development in order to contain the risk for dwellers to be involved in aircraft accidents. The number of people who live, work or congregate in these areas should be limited. The procedure to set Public Safety Zones is based on advanced technical analyses for major infrastructures. For smaller airports, simplified schemes are used, but, sometimes, they are not as effective when considering the actual safety conditions. This article aims to identify the shape and size of the Public Safety Zones for small and medium one-runway airports. The influence of the volume and mix of traffic on the PSZ geometry has been evaluated using the program named SARA (Sapienza Airport Risk Analysis); the results are correlated with the current Risk Plans generally adopted in Italy. According to the air traffic, the Risk Plans are characterized by a dynamic definition and fit the results obtained from risk assessment. Full article

(This article belongs to the Collection Air Transportation—Operations and Management)

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19 pages, 2374 KiB

Open AccessArticle

Uncertainty Evaluation in the Design of Structural Health Monitoring Systems for Damage Detection^†

by Christine Schubert Kabban^1,*, Richard Uber¹

, Kevin Lin¹, Bin Lin², Md Yeasin Bhuiyan²

and Victor Giurgiutiu²

¹ Department of Mathematics and Statistics, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson AFB, OH 45433-7765, USA

² Department of Mechanical Engineering, University of South Carolina, 300 Main Street A237, Columbia, SC 29208-0001, USA

^† This paper is an extended version of our paper published in 11th International Workshop on Structural Health Monitoring (IWSHM), Stanford, CA, USA, 12–14 September 2017.

Aerospace 2018, 5(2), 45; https://doi.org/10.3390/aerospace5020045 - 21 Apr 2018

Cited by 8 | Viewed by 6267

Abstract

The validation of structural health monitoring (SHM) systems for aircraft is complicated by the extent and number of factors that the SHM system must demonstrate for robust performance. Therefore, a time- and cost-efficient method for examining all of the sensitive factors must be [...] Read more.

The validation of structural health monitoring (SHM) systems for aircraft is complicated by the extent and number of factors that the SHM system must demonstrate for robust performance. Therefore, a time- and cost-efficient method for examining all of the sensitive factors must be conducted. In this paper, we demonstrate the utility of using the simulation modeling environment to determine the SHM sensitive factors that must be considered for subsequent experiments, in order to enable the SHM validation. We demonstrate this concept by examining the effect of SHM system configuration and flaw characteristics on the response of a signal from a known piezoelectric wafer active sensor (PWAS) in an aluminum plate, using simulation models of a particular hot spot. We derive the signal responses mathematically and through the statistical design of experiments, we determine the significant factors that affect the damage indices that are computed from the signal, using only half the number of runs that are normally required. We determine that the transmitter angle is the largest source of variation for the damage indices that are considered, followed by signal frequency and transmitter distance to the hot spot. These results demonstrate that the use of efficient statistical design and simulation may enable a cost- and time-efficient sequential approach to quantifying sensitive SHM factors and system validation. Full article

(This article belongs to the Special Issue Selected Papers from IWSHM 2017)

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18 pages, 2904 KiB

Open AccessArticle

Simulation-Based Virtual Cycle for Multi-Level Airport Analysis

by Miguel Mujica Mota^1,*,†, Alejandro Di Bernardi^2,†, Paolo Scala^1,† and Gabriel Ramirez-Diaz^3,†

¹ Aviation Academy, Amsterdam University of Applied Sciences, Weesperzijde 190, 1097 DZ Amsterdam, The Netherlands

² Grupo Transporte Aéreo—UIDET GTA-GIAI, Departamento de Aeronáutica, Facultad de Ingeniería, Universidad Nacional de La Plata. Calle 116 e/47 y 48, 1900 La Plata, Pcia. Buenos Aires, Argentina

³ Grupo Transporte Aéreo—UIDET GTA-GIAI, Departamento de Aeronáutica, Facultad de Ingeniería, Universidad Nacional de La Plata, CONICET. Calle 116 e/47 y 48, 1900 La Plata, Pcia. Buenos Aires, Argentina

^† These authors contributed equally to this work.

Aerospace 2018, 5(2), 44; https://doi.org/10.3390/aerospace5020044 - 19 Apr 2018

Cited by 10 | Viewed by 7735

Abstract

The aeronautical industry is expanding after a period of economic turmoil. For this reason, a growing number of airports are facing capacity problems that can sometimes only be resolved by expanding infrastructure, with the inherent risks that such decisions create. In order to [...] Read more.

The aeronautical industry is expanding after a period of economic turmoil. For this reason, a growing number of airports are facing capacity problems that can sometimes only be resolved by expanding infrastructure, with the inherent risks that such decisions create. In order to deal with uncertainty at different levels, it is necessary to have relevant tools during an expansion project or during the planning phases of new infrastructure. This article presents a methodology that combines simulation approaches with different description levels that complement each other when applied to the development of a new airport. The methodology is illustrated with an example that uses two models for an expansion project of an airport in The Netherlands. One model focuses on the operation of the airport from a high-level position, while the second focuses on other technical aspects of the operation that challenge the feasibility of the proposed configuration of the apron. The results show that by applying the methodology, analytical power is enhanced and the risk of making the wrong decisions is reduced. We identified the limitations that the future facility will have and the impact of the physical characteristics of the traffic that will operate in the airport. The methodology can be used for tackling different problems and studying particular performance indicators to help decision-makers take more informed decisions. Full article

(This article belongs to the Collection Air Transportation—Operations and Management)

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20 pages, 2290 KiB

Open AccessArticle

Simulation and Modeling of Rigid Aircraft Aerodynamic Responses to Arbitrary Gust Distributions

by Mehdi Ghoreyshi^1,*

, Ivan Greisz²

, Adam Jirasek¹ and Matthew Satchell¹

¹ High Performance Computing Research Center, U.S. Air Force Academy, Air Force Academy, CO 80840, USA

² Department of Mechanical and Aerospace Engineering, University of Colorado at Colorado Springs, Colorado Springs, CO 80918, USA

Aerospace 2018, 5(2), 43; https://doi.org/10.3390/aerospace5020043 - 18 Apr 2018

Cited by 16 | Viewed by 7480

Abstract

The stresses resulting from wind gusts can exceed the limit value and may cause large-scale structural deformation or even failure. All certified airplanes should therefore withstand the increased loads from gusts of considerable intensity. A large factor of safety will make the structure [...] Read more.

The stresses resulting from wind gusts can exceed the limit value and may cause large-scale structural deformation or even failure. All certified airplanes should therefore withstand the increased loads from gusts of considerable intensity. A large factor of safety will make the structure heavy and less economical. Thus, the need for accurate prediction of aerodynamic gust responses is motivated by both safety and economic concerns. This article presents the efforts to simulate and model air vehicle aerodynamic responses to various gust profiles. The computational methods developed and the research outcome will play an important role in the airplane’s structural design and certification. Cobalt is used as the flow solver to simulate aerodynamic responses to wind gusts. The code has a user-defined boundary condition capability that was tested for the first time in the present study to model any gust profile (intensity, direction, and duration) on any arbitrary configuration. Gust profiles considered include sharp edge, one minus cosine, a ramp, and a 1-cosine using tabulated data consisting of gust intensity values at discrete time instants. Test cases considered are a flat plate, a two-dimensional NACA0012 airfoil, and the high Reynolds number aero-structural dynamics (HIRENASD) configuration, which resembles a typical large passenger transport aircraft. Test cases are assumed to be rigid, and only longitudinal gust profiles are considered, though the developed codes can model any gust angle. Time-accurate simulation results show the aerodynamic responses to different gust profiles including transient solutions. Simulation results show that sharp edge responses of the flat plate agree well with the Küssner approximate function, but trends of other test cases do not match because of the thin airfoil assumptions made to derive the analytical function. Reduced order aerodynamic models are then created from the convolution integral of gust amplitude and the time-accurate responses to sharp-edge gusts. Convolution models are next used to predict aerodynamic responses to arbitrary gust profiles without the need of running time-accurate simulations for every gust shape. The results show very good agreement between developed models and simulation data. Full article

(This article belongs to the Special Issue Computational Aerodynamic Modeling of Aerospace Vehicles)

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22 pages, 10131 KiB

Open AccessArticle

Flight Load Assessment for Light Aircraft Landing Trajectories in Windy Atmosphere and Near Wind Farms

by Carmine Varriale¹

, Agostino De Marco¹

, Elia Daniele^2,*

, Jonas Schmidt²

and Bernhard Stoevesandt²

¹ Department of Industrial Engineering, University of Naples Federico II, Via Claudio 21, 80125 Naples, Italy

² Fraunhofer Institute for Wind Energy Systems, IWES, Küpkersweg 70, 26129 Oldenburg, Germany

Aerospace 2018, 5(2), 42; https://doi.org/10.3390/aerospace5020042 - 10 Apr 2018

Cited by 5 | Viewed by 10769

Abstract

This work focuses on the wake encounter problem occurring when a light, or very light, aircraft flies through or nearby a wind turbine wake. The dependency of the aircraft normal load factor on the distance from the turbine rotor in various flight and [...] Read more.

This work focuses on the wake encounter problem occurring when a light, or very light, aircraft flies through or nearby a wind turbine wake. The dependency of the aircraft normal load factor on the distance from the turbine rotor in various flight and environmental conditions is quantified. For this research, a framework of software applications has been developed for generating and controlling a population of flight simulation scenarios in presence of assigned wind and turbulence fields. The JSBSim flight dynamics model makes use of several autopilot systems for simulating a realistic pilot behavior during navigation. The wind distribution, calculated with OpenFOAM, is a separate input for the dynamic model and is considered frozen during each flight simulation. The aircraft normal load factor during wake encounters is monitored at different distances from the rotor, aircraft speeds, rates of descent and crossing angles. Based on these figures, some preliminary guidelines and recommendations on safe encounter distances are provided for general aviation aircraft, with considerations on pilot comfort and flight safety. These are needed, for instance, when an accident risk assessment study is required for flight in proximity of aeolic parks. A link to the GitHub code repository is provided. Full article

(This article belongs to the Special Issue Feature Papers in Aerospace)

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18 pages, 3929 KiB

Open AccessArticle

AEROM: NASA’s Unsteady Aerodynamic and Aeroelastic Reduced-Order Modeling Software

by Walter A. Silva

NASA Langley Research Center, Hampton, VA 23681, USA

Aerospace 2018, 5(2), 41; https://doi.org/10.3390/aerospace5020041 - 10 Apr 2018

Cited by 42 | Viewed by 9485

Abstract

The origins, development, implementation, and application of AEROM, NASA’s patented reduced-order modeling (ROM) software, are presented. Using the NASA FUN3D computational fluid dynamic (CFD) code, full and ROM aeroelastic solutions are computed at several Mach numbers and presented in the form of root [...] Read more.

The origins, development, implementation, and application of AEROM, NASA’s patented reduced-order modeling (ROM) software, are presented. Using the NASA FUN3D computational fluid dynamic (CFD) code, full and ROM aeroelastic solutions are computed at several Mach numbers and presented in the form of root locus plots. The use of root locus plots will help reveal the aeroelastic root migrations with increasing dynamic pressure. The method and software have been applied successfully to several configurations including the Lockheed-Martin N+2 supersonic configuration and the Royal Institute of Technology (KTH, Sweden) generic wind-tunnel model, among others. The software has been released to various organizations with applications that include CFD-based aeroelastic analyses and the rapid modeling of high-fidelity dynamic stability derivatives. We present recent results obtained from the application of the method to the AGARD 445.6 wing that reveal several interesting insights. Full article

(This article belongs to the Special Issue Computational Aerodynamic Modeling of Aerospace Vehicles)

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13 pages, 30717 KiB

Open AccessArticle

Damage Detection in a Composite T-Joint Using Guided Lamb Waves

by Marilyne Philibert^1,2

, Constantinos Soutis³

, Matthieu Gresil^1,3,*

and Kui Yao²

¹ i-Composites Lab, School of Materials, University of Manchester, Manchester M13 9PL, UK

² Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore 138634, Singapore

³ Aerospace Research Institute, University of Manchester, Manchester M13 9PL, UK

Aerospace 2018, 5(2), 40; https://doi.org/10.3390/aerospace5020040 - 9 Apr 2018

Cited by 36 | Viewed by 7208

Abstract

Low velocity impact induces barely visible damage in the form of matrix cracking or delamination that can grow under hydro-thermo-mechanical loading and possibly lead to catastrophic failure if not detected at an early stage. A network of piezoelectric transducers can be used to [...] Read more.

Low velocity impact induces barely visible damage in the form of matrix cracking or delamination that can grow under hydro-thermo-mechanical loading and possibly lead to catastrophic failure if not detected at an early stage. A network of piezoelectric transducers can be used to monitor a structure over time for life prognosis through generation and sensing of guided ultrasonic waves. The aim of this study is to design and develop such a sensing method for damage assessment in a composite T-joint subjected to mechanical impacts. In this context, monitoring of Lamb waves in a carbon fibre reinforced polymer (CFRP) T-joint has been completed where dispersion and tuning curves have been obtained. Guided waves are transmitted into the structure through different specified pairs of surface-bonded lead-zirconate-titanate (PZT) transducers in a pitch–catch active structural health monitoring (SHM) approach. With these experiments, Lamb wave fundamental modes (A₀ and S₀) are identified for monitoring impact damage by signal comparison with a prior obtained baseline. Detecting 4J and 10J inner impacts within the central region of the specimen is challenging when using conventional non-destructive techniques (NDT) because of the complex geometry and interference with the web. Signals are compared for the same selected sensing path; and amplitude differences have been observed in tuning curves after the 10J impact, which implies the occurrence of a structural change related to the impact. Full article

(This article belongs to the Special Issue Selected Papers from IWSHM 2017)

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17 pages, 79176 KiB

Open AccessArticle

Transducer Placement Option of Lamb Wave SHM System for Hotspot Damage Monitoring

by Vincentius Ewald^1,*, Roger M. Groves¹

and Rinze Benedictus²

¹ Aerospace Non-Destructive Testing Laboratory, Faculty of Aerospace Engineering, Delft University of Technology, 2628 CD Delft, The Netherlands

² Chair of Structural Integrity and Composites, Faculty of Aerospace Engineering, Delft University of Technology, 2628 CD Delft, The Netherlands

Aerospace 2018, 5(2), 39; https://doi.org/10.3390/aerospace5020039 - 4 Apr 2018

Cited by 16 | Viewed by 7730

Abstract

In this paper, we investigated transducer placement strategies for detecting cracks in primary aircraft structures using ultrasonic Structural Health Monitoring (SHM). The approach developed is for an expected damage location based on fracture mechanics, for example fatigue crack growth in a high stress [...] Read more.

In this paper, we investigated transducer placement strategies for detecting cracks in primary aircraft structures using ultrasonic Structural Health Monitoring (SHM). The approach developed is for an expected damage location based on fracture mechanics, for example fatigue crack growth in a high stress location. To assess the performance of the developed approach, finite-element (FE) modelling of a damage-tolerant aluminum fuselage has been performed by introducing an artificial crack at a rivet hole into the structural FE model and assessing its influence on the Lamb wave propagation, compared to a baseline measurement simulation. The efficient practical sensor position was determined from the largest change in area that is covered by reflected and missing wave scatter using an additive color model. Blob detection algorithms were employed to determine the boundaries of this area and to calculate the blob centroid. To demonstrate that the technique can be generalized, the results from different crack lengths and from tilted crack are also presented. Full article

(This article belongs to the Special Issue Selected Papers from IWSHM 2017)

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16 pages, 11238 KiB

Open AccessArticle

Maintenance Model of Digital Avionics

by Ahmed Raza

Department of Electronics, National Aviation University, 03058 Kiev, Ukraine

Aerospace 2018, 5(2), 38; https://doi.org/10.3390/aerospace5020038 - 2 Apr 2018

Cited by 5 | Viewed by 7363

Abstract

The cost of avionics maintenance is extremely high for modern aircraft. It can be as high as 30% of the aircraft maintenance cost. A great impact on the cost of avionics maintenance is provided by a high level of No Fault Found events [...] Read more.

The cost of avionics maintenance is extremely high for modern aircraft. It can be as high as 30% of the aircraft maintenance cost. A great impact on the cost of avionics maintenance is provided by a high level of No Fault Found events (NFF). Intermittent faults are the leading cause of the NFF appearance in avionics. The NFF rate for avionics systems is between 20% and 50%. The practice of avionics operation and maintenance confirms the relevance of assessing the impact of intermittent faults on the maintenance cost and the choice of such option of the maintenance management, in which the negative impact of the intermittent faults is minimized. In this paper, a new mathematical model of digital avionics maintenance is developed. Key maintenance effectiveness indicators are selected. General mathematical expressions are obtained for the average availability, mean time between unscheduled removals (MTBUR), and expected maintenance cost of single unit and redundant avionics systems, which are subject to permanent failures and intermittent faults. The dependence of the maintenance effectiveness indicators on the rate of permanent failures and intermittent faults is investigated for the case of exponential distribution of time to failures and faults. The dependence of average availability on the number of spare units in the airline’s warehouse is also analyzed. On the base of the proposed maintenance model, different options of avionics maintenance management are considered. Numerical examples illustrate how to reduce the expected maintenance cost of avionics systems. Full article

(This article belongs to the Special Issue Challenges in Reliability Analysis of Aerospace Electronics)

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21 pages, 4532 KiB

Open AccessReview

Survey of the Current Activities in the Field of Modeling the Space Debris Environment at TU Braunschweig

by André Horstmann, Christopher Kebschull, Sven Müller, Eduard Gamper, Sebastian Hesselbach, Kerstin Soggeberg, Mohamed Khalil Ben Larbi, Marcel Becker, Jürgen Lorenz, Carsten Wiedemann and Enrico Stoll^*

Institute of Space Systems, Technische Universität Braunschweig, Hermann-Blenk-Str. 23, 38108 Braunschweig, Germany

Aerospace 2018, 5(2), 37; https://doi.org/10.3390/aerospace5020037 - 2 Apr 2018

Cited by 19 | Viewed by 10002

Abstract

The Institute of Space Systems at Technische Universität Braunschweig has long-term experience in the field of space debris modeling. This article reviews the current state of ongoing research in this area. Extensive activities are currently underway to update the European space debris model [...] Read more.

The Institute of Space Systems at Technische Universität Braunschweig has long-term experience in the field of space debris modeling. This article reviews the current state of ongoing research in this area. Extensive activities are currently underway to update the European space debris model MASTER. In addition to updating the historical population, the future evolution of the space debris environment is also being investigated. The competencies developed within these activities are used to address current problems with regard to the possibility of an increasing number of catastrophic collisions. Related research areas include, for example, research in the field of orbit determination and the simulation of sensor systems for the acquisition and cataloging of orbital objects. In particular, the ability to provide simulated measurement data for object populations in almost all size ranges is an important prerequisite for these investigations. Some selected results on the distribution of space debris on Earth orbit are presented in terms of spatial density. Furthermore, specific fragmentation events will be discussed. Full article

(This article belongs to the Special Issue Space Debris: Impact and Remediation)

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Aerospace, Volume 5, Issue 2 (June 2018) – 34 articles

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