Topical Collection "Feature Papers in Aerospace"

Editor

Guest Editor
Prof. Dr. Konstantinos Kontis

Mechan Chair of Engineering, School of Engineering, University of Glasgow, James Watt Building South, University Avenue, Glasgow G12 8QQ, Scotland, UK
Website | E-Mail
Interests: aerodynamic technologies; flow and flight control systems; shock physics; aerospace design and optimization; flow diagnostics

Topical Collection Information

Dear Colleagues,

This Topical Collection collects high quality papers (original research articles or comprehensive review papers) in aerospace research fields. Highly experienced practitioners from various fields within the journal’s scope are welcome to contribute papers, highlighting the latest developments in their research area or the detailed summary of their own work done thus far. The papers would be published, free of charge, in Open Access after peer review.

Potential topics include, but are not limited to: aerospace design and optimization; aerospace propulsion; advances in space sciences; spacecrafts; aircrafts; aerospace sensors, devices and engines; smart materials and structures; energy harvesting; alternative fuels; flow and flight control systems; aerodynamics; traffic management; navigation and control; mission design and analysis; computational techniques.

The submission deadline for this round of call for papers is 31 October 2017.

Prof. Dr. Konstantinos Kontis
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Aerospace is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 550 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • aerospace
  • aeronautics
  • astronautics

Published Papers (21 papers)

2018

Jump to: 2017, 2016, 2015

Open AccessArticle Leading-Edge Roughness Affecting Diamond-Wing Aerodynamic Characteristics
Received: 1 August 2018 / Revised: 27 August 2018 / Accepted: 29 August 2018 / Published: 19 September 2018
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Abstract
Diamond wing configurations for low signature vehicles have been studied in recent years. Yet, despite numerous research on highly swept, sharp edged wings, little research on aerodynamics of semi-slender wings with blunt leading-edges exists. This paper reports on the stall characteristics of the
[...] Read more.
Diamond wing configurations for low signature vehicles have been studied in recent years. Yet, despite numerous research on highly swept, sharp edged wings, little research on aerodynamics of semi-slender wings with blunt leading-edges exists. This paper reports on the stall characteristics of the AVT-183 diamond wing configuration with variation of leading-edge roughness size and Reynolds number. Wind tunnel testing applying force and surface pressure measurements are conducted and the results presented and analysed. For the investigated Reynolds number range of 2.1 × 10 6 R e 2.7 × 10 6 there is no significant influence on the aerodynamic coefficients. However, leading-edge roughness height influences the vortex separation location. Trip dots produced the most downstream located vortex separation onset. Increasing the roughness size shifts the separation onset upstream. Prior to stall, global aerodynamic coefficients are little influenced by leading-edge roughness. In contrast, maximum lift and maximum angle of attack is reduced with increasing disturbance height. Surface pressure fluctuations show dominant broadband frequency peaks, distinctive for moderate sweep vortex breakdown. The experimental work presented here provides insights into the aerodynamic characteristics of diamond wings in a wide parameter space including a relevant angle of attack range up to post-stall. Full article
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Open AccessArticle On Four New Methods of Analytical Calculation of Rocket Trajectories
Received: 15 June 2018 / Revised: 20 July 2018 / Accepted: 27 July 2018 / Published: 15 August 2018
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Abstract
The calculation of rocket trajectories is most often performed using purely numerical methods that account for all relevant parameters and provide the required results. There is a complementary need for analytical methods that make more explicit the effect of the various rocket and
[...] Read more.
The calculation of rocket trajectories is most often performed using purely numerical methods that account for all relevant parameters and provide the required results. There is a complementary need for analytical methods that make more explicit the effect of the various rocket and atmospheric parameters of the trajectory and can be used as test cases with unlimited accuracy. The available analytical methods take into account (i) variable rocket mass due to propellant consumption. The present paper includes four new analytical methods taking into account besides (i) also (ii) nonlinear aerodynamic forces proportional to the square of the velocity and (iii) exponential dependence of the mass density with altitude for an isothermal atmospheric layer. The four new methods can be used in “hybrid analytical-numerical” approach in which: (i) the atmosphere is divided into isothermal rather than homogeneous layers for greater physical fidelity; and (ii) in each layer, an exact analytical solution of the equations of motion with greater mathematical accuracy than a numerical approximation is used. This should allow a more accurate calculation of rocket trajectories while discretizing the atmosphere into a smaller number of layers. The paper therefore concentrates on four analytical methods of calculation of rocket trajectories in an isothermal atmospheric layers using new exact solutions of the equations of motion beyond those currently available in the literature. The four methods are developed first for the simpler case of a vertical climb and will be subsequently extended to the practically more relevant case of a gravity turn. Full article
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Open AccessArticle Flight Load Assessment for Light Aircraft Landing Trajectories in Windy Atmosphere and Near Wind Farms
Received: 16 February 2018 / Revised: 4 April 2018 / Accepted: 5 April 2018 / Published: 10 April 2018
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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
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Open AccessArticle Wake-Model Effects on Induced Drag Prediction of Staggered Boxwings
Received: 30 November 2017 / Revised: 23 December 2017 / Accepted: 12 January 2018 / Published: 24 January 2018
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Abstract
For staggered boxwings the predictions of induced drag that rely on common potential-flow methods can be of limited accuracy. For example, linear, freestream-fixed wake models cannot resolve effects related to wake deflection and roll-up, which can have significant affects on the induced drag
[...] Read more.
For staggered boxwings the predictions of induced drag that rely on common potential-flow methods can be of limited accuracy. For example, linear, freestream-fixed wake models cannot resolve effects related to wake deflection and roll-up, which can have significant affects on the induced drag projection of these systems. The present work investigates the principle impact of wake modelling on the accuracy of induced drag prediction of boxwings with stagger. The study compares induced drag predictions of a higher-order potential-flow method that uses fixed and relaxed-wake models, and of an Euler-flow method. Positive-staggered systems at positive angles of attack are found to be particularly prone to higher-order wake effects due to vertical contraction of wakes trajectories, which results in smaller effective height-to-span ratios than compared with negative stagger and thus closer interactions between trailing wakes and lifting surfaces. Therefore, when trying to predict induced drag of positive staggered boxwings, only a potential-flow method with a fully relaxed-wake model will provide the high-degree of accuracy that rivals that of an Euler method while being computationally significantly more efficient. Full article
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Open AccessArticle Preliminary Correlations for Remotely Piloted Aircraft Systems Sizing
Received: 28 October 2017 / Revised: 20 December 2017 / Accepted: 5 January 2018 / Published: 8 January 2018
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Abstract
The field of Remotely Piloted Aircraft Systems (RPAS) is currently undergoing a noteworthy expansion. The diverse types of missions that these aircraft can accomplish, both in military and civil environments, have motivated an increase of interest in their study and applications. The methods
[...] Read more.
The field of Remotely Piloted Aircraft Systems (RPAS) is currently undergoing a noteworthy expansion. The diverse types of missions that these aircraft can accomplish, both in military and civil environments, have motivated an increase of interest in their study and applications. The methods chosen to develop this study are based on the statistical analysis of a database including numerous models of RPAS and the estimation of different correlations in order to develop a design method for rapid sizing of H-tail RPAS. Organizing the information of the database according to relevant characteristics, information relative to the state-of-the-art design tendencies can be extracted, which can serve to take decisions relative to the aerodynamic configuration or the power plant in the first phases of the design project. Furthermore, employing statistical correlations estimated from the database, a design method for rapid-sizing of H-tail RPAS has been conducted, which will be focused on the sizing of the wing and tail surfaces. The resulting method has been tested by applying it to an example case so as to validate the proposed procedure. Full article
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Open AccessArticle Application of an Efficient Gradient-Based Optimization Strategy for Aircraft Wing Structures
Received: 8 December 2017 / Revised: 26 December 2017 / Accepted: 2 January 2018 / Published: 4 January 2018
Cited by 2 | PDF Full-text (4446 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a practical optimization framework and enhanced strategy within an industrial setting are proposed for solving large-scale structural optimization problems in aerospace. The goal is to eliminate the difficulties associated with optimization problems, which are mostly nonlinear with numerous mixed continuous-discrete
[...] Read more.
In this paper, a practical optimization framework and enhanced strategy within an industrial setting are proposed for solving large-scale structural optimization problems in aerospace. The goal is to eliminate the difficulties associated with optimization problems, which are mostly nonlinear with numerous mixed continuous-discrete design variables. Particular emphasis is placed on generating good initial starting points for the search process and in finding a feasible optimum solution or improving the chances of finding a better optimum solution when traditional techniques and methods have failed. The efficiency and reliability of the proposed strategy were demonstrated through the weight optimization of different metallic and composite laminated wingbox structures. The results show the effectiveness of the proposed procedures in finding an optimized solution for high-dimensional search space cases with a given level of accuracy and reasonable computational resources and user efforts. Conclusions are also inferred with regards to the sensitivity of the optimization results obtained with respect to the choice of different starting values for the design variables, as well as different optimization algorithms in the optimization process. Full article
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Open AccessReview Modeling Plasma via Electron Impact Ionization
Received: 17 November 2017 / Revised: 26 December 2017 / Accepted: 28 December 2017 / Published: 2 January 2018
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Abstract
Variable and potential plasma applications in aerospace engineering are exemplified by ion thrusters, flow control by plasma actuator, enhanced ignition and combustion stability. The operational environments span a range from the rarefied to continuum gasdynamic regimes; however, the ionization process in practical applications
[...] Read more.
Variable and potential plasma applications in aerospace engineering are exemplified by ion thrusters, flow control by plasma actuator, enhanced ignition and combustion stability. The operational environments span a range from the rarefied to continuum gasdynamic regimes; however, the ionization process in practical applications is mostly by electron impact. The fundamental ionization mechanisms by electron impact consist of electron secondary mission and the cascading process. In an alternating electric field, unsteady and random micro discharges or streamers are always presented; therefore the discharge physics imposes a formidable challenge for incisive understanding. Meanwhile, the ionized species constitute hundreds of metastable chemical species; under this circumstance the physics-based modeling for analyzing the inhomogeneous medium becomes necessary. A summary of the physics-based modeling for electron impact ionization from the Boltzmann distribution equation to the inelastic particle kinetics formulation is delineated. Full article
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2017

Jump to: 2018, 2016, 2015

Open AccessArticle The Impact of Volute Aspect Ratio on the Performance of a Mixed Flow Turbine
Received: 27 October 2017 / Revised: 16 November 2017 / Accepted: 20 November 2017 / Published: 23 November 2017
Cited by 1 | PDF Full-text (11367 KB) | HTML Full-text | XML Full-text
Abstract
Current trends in the automotive industry towards engine downsizing mean turbocharging now plays a vital role in engine performance. A turbocharger increases charge air density using a turbine to extract waste energy from the exhaust gas to drive a compressor. Most turbocharger applications
[...] Read more.
Current trends in the automotive industry towards engine downsizing mean turbocharging now plays a vital role in engine performance. A turbocharger increases charge air density using a turbine to extract waste energy from the exhaust gas to drive a compressor. Most turbocharger applications employ a radial inflow turbine. However, mixed flow turbines can offer non-zero blade angles, reducing leading edge (LE) separation at low velocity ratios. The current paper investigates the performance of a mixed flow turbine with three different volute aspect ratio (AR) designs (AR = 0.5, 1 and 2). With constant A/r (ratio of volute area to centroid radius), the AR = 0.5 volute design produced a 4.3% increase in cycle averaged mass flow parameter (MFP) compared to the AR = 2 design. For the purpose of performance comparison, it was necessary to manipulate the volute A/r’s to ensure constant MFP for aerodynamic similarity. With the volute A/r’s manipulated to ensure constant MFP for aerodynamic similarity, the maximum variation of cycle averaged normalized efficiency measured between the designs was 1.47%. Purely in the rotor region, the variation in normalized cycle averaged efficiency was 1%. The smallest tested volute aspect ratio showed a significant increase in volute loss while the ARs of 1 and 2 showed similar levels of loss. The smallest AR volute showed significant secondary flow development in the volute. The resulting variation in LE incidence was found to vary as a result. Full article
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Open AccessArticle Air Traffic Security: Aircraft Classification Using ADS-B Message’s Phase-Pattern
Received: 27 September 2017 / Revised: 20 October 2017 / Accepted: 27 October 2017 / Published: 30 October 2017
Cited by 1 | PDF Full-text (7996 KB) | HTML Full-text | XML Full-text
Abstract
Automatic Dependent Surveillance-Broadcast (ADS-B) is a surveillance system used in Air Traffic Control. With this system, the aircraft transmits their own information (identity, position, velocity, etc.) to any equipped listener for surveillance scope. The ADS-B is based on a very simple protocol and
[...] Read more.
Automatic Dependent Surveillance-Broadcast (ADS-B) is a surveillance system used in Air Traffic Control. With this system, the aircraft transmits their own information (identity, position, velocity, etc.) to any equipped listener for surveillance scope. The ADS-B is based on a very simple protocol and does not provide any kind of authentication and encryption, making it vulnerable to many types of cyber-attacks. In the paper, the use of the airplane/transmitter carrier phase is proposed as a feature to perform a classification of the aircraft and, therefore, distinguish legitimate messages from fake ones. The feature extraction process is described and a classification method is selected. Finally, a complete intruder detection algorithm is proposed and evaluated with real data. Full article
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Open AccessArticle Evolutionary Approach to Lambert’s Problem for Non-Keplerian Spacecraft Trajectories
Received: 11 July 2017 / Revised: 30 August 2017 / Accepted: 31 August 2017 / Published: 11 September 2017
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Abstract
In this paper, we use differential evolution (DE), with best-evolved results refined using a Nelder–Mead optimization, to solve boundary-value complex problems in orbital mechanics relevant to low Earth orbits (LEO). A class of Lambert-type problems is examined to evaluate the performance of this
[...] Read more.
In this paper, we use differential evolution (DE), with best-evolved results refined using a Nelder–Mead optimization, to solve boundary-value complex problems in orbital mechanics relevant to low Earth orbits (LEO). A class of Lambert-type problems is examined to evaluate the performance of this evolutionary method in its application to solving nonlinear boundary value problems (BVP) arising in mission planning. In this method, we evolve impulsive initial velocity vectors giving rise to intercept trajectories that take a spacecraft from given initial position in space to specified target position. The positional error of the final position is minimized subject to time-of-flight and/or energy (fuel) constraints. The method is first validated by demonstrating its ability to recover known analytical solutions obtainable with the assumption of Keplerian motion; the method is then applied to more complex non-Keplerian problems incorporating trajectory perturbations arising in low Earth orbit (LEO) due to the Earth’s oblateness and rarefied atmospheric drag. The viable trajectories obtained for these challenging problems demonstrate the ability of this computational approach to handle Lambert-type problems with arbitrary perturbations, such as those occurring in realistic mission trajectory design. Full article
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Open AccessArticle Effects of Wake Shapes on High-Lift System Aerodynamic Predictions
Received: 25 February 2017 / Revised: 8 April 2017 / Accepted: 14 April 2017 / Published: 19 April 2017
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Abstract
High-lift devices are commonly modelled using potential flow methods at the conceptual design stage. Often, these analyses require the use of prescribed wake shapes in order to avoid numerical stability issues. The wake type used, however, has an impact on the absolute aerodynamic
[...] Read more.
High-lift devices are commonly modelled using potential flow methods at the conceptual design stage. Often, these analyses require the use of prescribed wake shapes in order to avoid numerical stability issues. The wake type used, however, has an impact on the absolute aerodynamic load predictions, which is why, in general, these methods are used to assess performance changes due to configuration variations. Therefore, a study was completed that compared the predicted aerodynamic performance changes of such variations of high-lift configurations using different wake types. Lift and induced drag results are compared with the results that were obtained using relaxed wakes and various prescribed wake shapes. Specific attention is given to predictions of performance changes due to changes in geometry. It was found that models with wakes that are prescribed below the freestream direction yield the best results when investigating performance changes due to flap deflections and flap-span changes. The effect of flap-gap sizes is best evaluated using a fully-relaxed model. The numerically most stable approach of wakes that are prescribed leaving the trailing edge upwards seems to be least reliable in predicting performance changes. Full article
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Open AccessArticle Design and Performance of Modular 3-D Printed Solid-Propellant Rocket Airframes
Received: 23 February 2017 / Revised: 18 March 2017 / Accepted: 20 March 2017 / Published: 23 March 2017
Cited by 1 | PDF Full-text (6039 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Solid-propellant rockets are used for many applications, including military technology, scientific research, entertainment, and aerospace education. This study explores a novel method for design modularization of the rocket airframes, utilizing additive manufacturing (AM) technology. The new method replaces the use of standard part
[...] Read more.
Solid-propellant rockets are used for many applications, including military technology, scientific research, entertainment, and aerospace education. This study explores a novel method for design modularization of the rocket airframes, utilizing additive manufacturing (AM) technology. The new method replaces the use of standard part subsystems with complex multi-function parts to improve customization, design flexibility, performance, and reliability. To test the effectiveness of the process, two experiments were performed on several unique designs: (1) ANSYS CFX® simulation to measure the drag coefficients, the pressure fields, and the streamlines during representative flights and (2) fabrication and launch of the developed designs to test their flight performance and consistency. Altitude and 3-axis stability was measured during the eight flights via an onboard instrument package. Data from both experiments demonstrated that the designs were effective, but varied widely in their performance; the sources of the performance differences and errors were documented and analyzed. The modularization process reduced the number of parts dramatically, while retaining good performance and reliability. The specific benefits and caveats of using extrusion-based 3-D printing to produce airframe components are also demonstrated. Full article
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2016

Jump to: 2018, 2017, 2015

Open AccessArticle Continuation Methods for Nonlinear Flutter
Received: 27 October 2016 / Revised: 3 December 2016 / Accepted: 5 December 2016 / Published: 9 December 2016
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Abstract
Continuation methods are presented that are capable of treating frequency domain flutter equations, including multiple nonlinearities represented by describing functions. A small problem demonstrates how a series of continuation processes can find all limit-cycle oscillations within a specified region with a reasonable degree
[...] Read more.
Continuation methods are presented that are capable of treating frequency domain flutter equations, including multiple nonlinearities represented by describing functions. A small problem demonstrates how a series of continuation processes can find all limit-cycle oscillations within a specified region with a reasonable degree of confidence. Curves of the limit-cycle amplitude variation with velocity, indicating regions of stability and instability with colors, give a compact view of the nonlinear behavior throughout the flight regime. A continuation technique for reducing limit-cycle amplitudes by adjusting various system parameters is presented. These processes are economical enough to be a routine part of aircraft design and certification. Full article
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Open AccessFeature PaperCommunication Exploring Civil Drone Accidents and Incidents to Help Prevent Potential Air Disasters
Received: 11 May 2016 / Revised: 19 July 2016 / Accepted: 19 July 2016 / Published: 22 July 2016
Cited by 13 | PDF Full-text (2387 KB) | HTML Full-text | XML Full-text
Abstract
A recent alleged “drone” collision with a British Airways Airbus A320 at Heathrow Airport highlighted the need to understand civil Remotely Piloted Aircraft Systems (RPAS) accidents and incidents (events). This understanding will facilitate improvements in safety by ensuring efforts are focused to reduce
[...] Read more.
A recent alleged “drone” collision with a British Airways Airbus A320 at Heathrow Airport highlighted the need to understand civil Remotely Piloted Aircraft Systems (RPAS) accidents and incidents (events). This understanding will facilitate improvements in safety by ensuring efforts are focused to reduce the greatest risks. One hundred and fifty two RPAS events were analyzed. The data was collected from a 10-year period (2006 to 2015). Results show that, in contrast to commercial air transportation (CAT), RPAS events have a significantly different distribution when categorized by occurrence type, phase of flight, and safety issue. Specifically, it was found that RPAS operations are more likely to experience (1) loss of control in-flight, (2) events during takeoff and in cruise, and (3) equipment problems. It was shown that technology issues, not human factors, are the key contributor in RPAS events. This is a significant finding, as it is contrary to the industry view which has held for the past quarter of a century that human factors are the key contributor (which is still the case for CAT). Regulators should therefore look at technologies and not focus solely on operators. Full article
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Open AccessArticle Suppression of Low-Frequency Shock Oscillations over Boundary Layers by Repetitive Laser Pulse Energy Deposition
Received: 28 March 2016 / Revised: 18 April 2016 / Accepted: 22 April 2016 / Published: 27 April 2016
Cited by 4 | PDF Full-text (4124 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The effect of repetitive energy deposition on low Strouhal number oscillations of the shock wave induced by boundary-layer interaction over a cylinder-flare model was studied. The fluctuation of the energy deposition frequency was induced in the flow, because the bubble generated by the
[...] Read more.
The effect of repetitive energy deposition on low Strouhal number oscillations of the shock wave induced by boundary-layer interaction over a cylinder-flare model was studied. The fluctuation of the energy deposition frequency was induced in the flow, because the bubble generated by the energy deposition flowed downstream along the surface repeatedly. The region before the bubble size was affected by the energy deposition directly, so the fluctuation frequency was equal to the energy deposition frequency. However, the flare shock behavior at a position farther from the surface than the bubble size was also affected strongly by the energy deposition. For low-frequency unsteadiness and the effect of energy deposition on its unsteadiness, two categories have been observed. In the relatively small flare angle case, the flare shock was oscillated owing to the fluctuation induced by the boundary-layer interaction at the shock foot, and its oscillation occurred at 2.1 kHz with a small amplitude. The amplitude of this oscillation was decreased by highly repetitive energy depositions, and its amplitude could not be detected at a highly repetitive energy deposition. In the longer cylinder section case, the region of the shock-wave interaction was widened, and the amplitude of the flare shock oscillation was increased. In this case, the amplitude drastically decreased because of energy deposition. Full article
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Open AccessCommunication Semi-Empirical Prediction of Airfoil Hysteresis
Received: 25 February 2016 / Revised: 17 March 2016 / Accepted: 18 March 2016 / Published: 24 March 2016
Cited by 4 | PDF Full-text (721 KB) | HTML Full-text | XML Full-text
Abstract
A semi-empirical method is presented to estimate the angular excursion and the lift loss associated with static hysteresis on an airfoil. Wind tunnel data of various airfoils is used to define and validate the methodology. The resulting equation provides a relationship between the
[...] Read more.
A semi-empirical method is presented to estimate the angular excursion and the lift loss associated with static hysteresis on an airfoil. Wind tunnel data of various airfoils is used to define and validate the methodology. The resulting equation provides a relationship between the size of the hysteresis loop and characteristics of the airfoil. Comparisons of the equation with experiment show encouraging agreement both in terms of the magnitude of the lift loss and the extent of the loop. Full article
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Open AccessFeature PaperArticle Analysis of Radio Frequency Blackout for a Blunt-Body Capsule in Atmospheric Reentry Missions
Received: 9 December 2015 / Revised: 25 December 2015 / Accepted: 31 December 2015 / Published: 6 January 2016
Cited by 4 | PDF Full-text (5366 KB) | HTML Full-text | XML Full-text
Abstract
A numerical analysis of electromagnetic waves around the atmospheric reentry demonstrator (ARD) of the European Space Agency (ESA) in an atmospheric reentry mission was conducted. During the ARD mission, which involves a 70% scaled-down configuration capsule of the Apollo command module, radio frequency
[...] Read more.
A numerical analysis of electromagnetic waves around the atmospheric reentry demonstrator (ARD) of the European Space Agency (ESA) in an atmospheric reentry mission was conducted. During the ARD mission, which involves a 70% scaled-down configuration capsule of the Apollo command module, radio frequency blackout and strong plasma attenuation of radio waves in communications with data relay satellites and air planes were observed. The electromagnetic interference was caused by highly dense plasma derived from a strong shock wave generated in front of the capsule because of orbital speed during reentry. In this study, the physical properties of the plasma flow in the shock layer and wake region of the ESA ARD were obtained using a computational fluid dynamics technique. Then, electromagnetic waves were expressed using a frequency-dependent finite-difference time-domain method using the plasma properties. The analysis model was validated based on experimental flight data. A comparison of the measured and predicted results showed good agreement. The distribution of charged particles around the ESA ARD and the complicated behavior of electromagnetic waves, with attenuation and reflection, are clarified in detail. It is suggested that the analysis model could be an effective tool for investigating radio frequency blackout and plasma attenuation in radio wave communication. Full article
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2015

Jump to: 2018, 2017, 2016

Open AccessArticle C0 Layerwise Model with Fixed Degrees of Freedom and Variable In- and Out-of-Plane Kinematics by Strain Energy Updating Technique
Aerospace 2015, 2(4), 637-672; https://doi.org/10.3390/aerospace2040637
Received: 19 October 2015 / Revised: 11 November 2015 / Accepted: 11 November 2015 / Published: 17 November 2015
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Abstract
Physically based zigzag models have the merit of giving accurate stress predictions for laminates and sandwiches keeping fixed the functional degrees of freedom, though at the expense of the introduction of their derivatives. In the present paper, a technique that enables deleting these
[...] Read more.
Physically based zigzag models have the merit of giving accurate stress predictions for laminates and sandwiches keeping fixed the functional degrees of freedom, though at the expense of the introduction of their derivatives. In the present paper, a technique that enables deleting these derivatives is developed. The objective is finding a priori corrections of displacements, which make the energy of the model with all the derivatives neglected equivalent to that of its initial counterpart model containing all the derivatives. Numerical applications show that this technique can obtain accurate results, even for strongly asymmetrical lay-ups, keeping low the computational cost. Full article
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Open AccessArticle East–West GEO Satellite Station-Keeping with Degraded Thruster Response
Aerospace 2015, 2(4), 581-601; https://doi.org/10.3390/aerospace2040581
Received: 6 April 2015 / Revised: 21 August 2015 / Accepted: 11 September 2015 / Published: 29 September 2015
Cited by 1 | PDF Full-text (1459 KB) | HTML Full-text | XML Full-text
Abstract
The higher harmonic terms of Earth’s gravitational potential slowly modify the nominal longitude of geostationary Earth orbit (GEO) satellites, while the third-body presence (Moon and Sun) mainly affects their latitude. For this reason, GEO satellites periodically need to perform station-keeping maneuvers, namely, east–west
[...] Read more.
The higher harmonic terms of Earth’s gravitational potential slowly modify the nominal longitude of geostationary Earth orbit (GEO) satellites, while the third-body presence (Moon and Sun) mainly affects their latitude. For this reason, GEO satellites periodically need to perform station-keeping maneuvers, namely, east–west and north–south maneuvers to compensate for longitudinal and latitudinal variations, respectively. During the operational lifetime of GEO satellites, the thrusters’ response when commanded to perform these maneuvers slowly departs from the original nominal impulsive behavior. This paper addresses the practical problem of how to perform reliable east–west station-keeping maneuvers when thruster response is degraded. The need for contingency intervention from ground-based satellite operators is reduced by breaking apart the scheduled automatic station-keeping maneuvers into smaller maneuvers. Orbital alignment and attitude are tracked on-board during and in between sub-maneuvers, and any off nominal variations are corrected for with subsequent maneuvers. These corrections are particularly important near the end of the lifetime of GEO satellites, where thruster response is farthest from nominal performance. Full article
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Open AccessArticle CFD Study of an Annular-Ducted Fan Lift System for VTOL Aircraft
Aerospace 2015, 2(4), 555-580; https://doi.org/10.3390/aerospace2040555
Received: 6 August 2015 / Revised: 17 September 2015 / Accepted: 22 September 2015 / Published: 29 September 2015
Cited by 5 | PDF Full-text (6081 KB) | HTML Full-text | XML Full-text
Abstract
The present study aimed at assessing a novel annular-ducted fan lift system for VTOL aircraft through computational fluid dynamics (CFD) simulations. The power and lift efficiency of the lift fan system in hover mode, the lift and drag in transition mode, the drag
[...] Read more.
The present study aimed at assessing a novel annular-ducted fan lift system for VTOL aircraft through computational fluid dynamics (CFD) simulations. The power and lift efficiency of the lift fan system in hover mode, the lift and drag in transition mode, the drag and flight speed of the aircraft in cruise mode and the pneumatic coupling of the tip turbine and jet exhaust were studied. The results show that the annular-ducted fan lift system can have higher lift efficiency compared to the rotor of the Apache helicopter; the smooth transition from vertical takeoff to cruise flight needs some extra forward thrust to overcome a low peak of drag; the aircraft with the lift fan system enclosed during cruise flight theoretically may fly faster than helicopters and tiltrotors based on aerodynamic drag prediction, due to the elimination of rotor drag and compressibility effects on the rotor blade tips; and pneumatic coupling of the tip turbine and jet exhaust of a 300 m/s velocity can provide enough moment to spin the lift fan. The CFD results provide insight for future experimental study of the annular-ducted lift fan VTOL aircraft. Full article
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Open AccessReview The Flight of Birds and Other Animals
Aerospace 2015, 2(3), 505-523; https://doi.org/10.3390/aerospace2030505
Received: 9 July 2015 / Revised: 24 August 2015 / Accepted: 26 August 2015 / Published: 1 September 2015
Cited by 2 | PDF Full-text (6550 KB) | HTML Full-text | XML Full-text
Abstract
Methods of observing birds in flight now include training them to fly under known conditions in wind tunnels, and fitting free-flying birds with data loggers, that are either retrieved or read remotely via satellite links. The performance that comes to light depends on
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Methods of observing birds in flight now include training them to fly under known conditions in wind tunnels, and fitting free-flying birds with data loggers, that are either retrieved or read remotely via satellite links. The performance that comes to light depends on the known limitations of the materials from which they are made, and the conditions in which the birds live. Bird glide polars can be obtained by training birds to glide in a tilting wind tunnel. Translating these curves to power required from the flight muscles in level flight requires drag coefficients to be measured, which unfortunately does not work with bird bodies, because the flow is always fully detached. The drag of bodies in level flight can be determined by observing wingbeat frequency, and shows CD values around 0.08 in small birds, down to 0.06 in small waders specialised for efficient migration. Lift coefficients are up to 1.6 in gliding, or 1.8 for short, temporary glides. In-flight measurements can be used to calculate power curves for birds in level flight, and this has been applied to migrating geese in detail. These typically achieve lift:drag ratios around 15, including allowances for stops, as against 19 for continuous powered flight. The same calculations, applied to Pacific Black-tailed Godwits which start with fat fractions up to 0.55 at departure, show that such birds not only cross the Pacific to New Zealand, but have enough fuel in hand to reach the South Pole if that were necessary. This performance depends on the “dual fuel” arrangements of these migrants, whereby they use fat as their main fuel, and supplement this by extra fuel from burning the engine (flight muscles), as less power is needed later in the flight. The accuracy of these power curves has never been checked, although provision for stopping the bird, and making these checks at regular intervals during a simulated flight was built into the original design of the Lund wind tunnel. The Flight programme, which does these comparisons, also had provision for including contributions due to extracting energy from the atmosphere (soaring), or intermittent bounding flight in small birds (Passerines). It has been known for some time that the feathered surface allows the bird to delay or reverse detachment of the boundary layer, although exactly how this works remains a mystery, which might have practical applications. The bird wing was in use in past times, when birds were still competing with pterosaurs, although these had less efficient wings. The birds that survived the extinction that killed the pterosaurs and dinosaurs have (today) an automatic spherical navigator, which enables them to cross the Pacific and find New Zealand on the other side. Bats have never had such a device, and pterosaurs probably did not either. Animals, when seen from a zoological point of view, are adapted to whatever problems they had to deal with in earlier times. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: On the Study of Ground Station Architectures for Multi-Mission Support
Authors: Miguel A. Salas-Natera 1; Ramón Martínez Rodríguez-Osorio 2; Leandro de Haro Ariet 2
Affiliation: 1 Adjunct Professor at Universidad Autónoma de Madrid; 2 Professor at Universidad Politécnica de Madrid, Madrid, Spain
Abstract: Ground stations which integrate the control segment of a satellite mission have as a common feature, the use of large reflector antennas for space communication. Apart from many advantages, large dishes pose a number of impairments regarding their mechanical complexity, low flexibility, and high operation and maintenance costs. Thus, reflector antennas are expensive and require the installation of a complex mechanical system to track only one satellite at the same time reducing the efficiency of the earth segment [1, 2].
With the increase of new satellite launches, as well as new satellites and constellation of low earth orbit (LEO), medium earth orbit (MEO), and geostationary earth orbit (GEO), not only the data download capacity will be saturated for some satellite communication systems and applications but also the uplink for TT&C will require novel architectures. One alternative is the use of antenna arrays with smaller radiating elements combined with signal processing and beamforming [3]. Thus, the feasibility of other antenna technologies have been evaluated during last years to improve the performance of traditional earth stations to serve satellite tracking, telemetry and command (TT&C) operation, payload and payload message or data routing [4].
Technological challenges have been faced during the implementation of satellite communication systems in the last decades. The design of a Test-Bed flexible and modular for testing or debugging beamforming algorithms and receiver architectures is an invaluable contribution in the educational, research and development area on satellite communication systems [5].
The aim of using a single antenna for tracking many satellites at the same time avoiding mechanical movements as well as its inexpensive cost make these antennas an alternative to be considered [5]. Multi-beam ability and interference rejection are facilitated thanks to the electronic control system of such antennas that improves the versatility of the ground stations.
Main advantages of antenna arrays over large reflectors are the higher flexibility, lower production and maintenance cost, modularity and a more efficient use of the spectrum. Moreover, multi-mission stations can be designed to track different satellites simultaneously by dividing the array in sub-arrays with simultaneous beamforming processes. However, some issues must be considered during the design and implementation of a ground station antenna array: first of all, the architecture (geometry, number of antenna elements) and the beamforming process (optimization criteria, algorithm) must be selected according to the specifications of the system: gain requirements, interference cancellation capabilities, reference signal, complexity, etc. During implementation, deviations will appear as compared to the design due to the manufacturing process: sensor location deviation and sensor gain and phase errors [6]. In an antenna array, the computation of a close approach of the direction of arrival (DoA) and the correct performance of the beamforming algorithm depends on the calibration procedure results.
In this sense, exhaustive errors analyses of antenna arrays have been done identifying main issues of arraying and challenges for calibration process [7]. In the literature, after the analyses of calibration techniques, novel proposal for calibration assessment has been presented [8, 9].
In recent effort, new antenna array architectures have been under analyses and development. In [4] a highly effective, multi-function, low cost spherical phased array antenna design that provides hemispherical coverage is analyzed. This kind of novel architecture design, as the geodesic dome phased array antenna (GDPAA) presented in [4] preserves all the advantages of spherical phased array antennas while the fabrication is based on well-developed, easily manufacturable and affordable planar array technology [10, 11]. This antenna architecture consists of a number of planar phased sub-arrays arranged in an icosahedral geodesic dome configuration.
In contrast to the about 10 m diameters dome of the GDPAA, there is the geodesic dome array (GEODA) [12] with 5 m diameters dome. The GEODA was initially specified for satellite tracking at 1.7 GHz, including multi-mission and multi-beam scenarios [6]. Subsequently, the system of the GEODA has been upgraded also for transmission [13].
As explained, novel systems are more and more size reduced, and new trends and available technologies encourage to the development of lighter and handle systems for satellite communications opening a bridge from the technical viability to the presence of novel light multi-mission systems and multiplatform devices.
This paper will present a full review of the actual requirements for small ground station aimed at multi-mission purposes, the challenges to be achieved in the early future, and error analysis method review for a realistic case study.
References: [1] A. Torre, J. Gonzalo, M. Pulido and R. Martínez Rodríguez-Osorio, "New generation Ground Segment Architecture for LEO satellites," in 57th International Astronautical Congress, Valencia, October 2006.
[2] M. A. Salas Natera, A. García Aguilar, J. Mora Cuevas, J. M. Fernández, P. Padilla de la Torre, J. García-Gasco Trujillo, R. Martínez Rodríguez-Osorio, M. Sierra-Pérez, L. De Haro Ariet and M. Sierra Castañer, "New Antenna Array Architectures for Satellite Communications," in Advences in Satellite Communications, InTech, 2011, pp. 167 - 194.
[3] L. C. Godara, "Application of Antenna Arrays to Mobile Communication, Part II: Beamforming and Direction of Arrival Considerations," Proc. IEEE, vol. 85, no. 8, pp. 1195-1245, August 1997.

[4] B. Tomasic, J. Turtle and S. Liu, "A Geodesic Sphere Phased Array Antenna for satellite control and communication," in XXVII General Assembly of the International Union of Radio Science, Maastricht, August 2002.
[5] M. A. Salas Natera, R. Martínez Rodríguez-Osorio, A. Antón Sánchez, I. García-Rojo and L. Cuellar, "A3TB: Adaptive Antenna Array test-bed for tracking LEO satellites based on software defined radio," in 59th International Astronautical Congress, Glasgow, 2008.
[6] R. Martínez and M. A. Salas Natera, "On the use of Ground Antenna Arrays for Satellite Tracking: Architecture, Beamforming, Calibration and Measurements," in 61st International Astronautical Congress, Prague, 2010.
[7] M. Salas Natera and R. Martínez, "Analytical Evaluation of Uncertainty on Active Antenna Arrays," IEEE Transaction on Aerospace and Electronic Systems , vol. Accepted for publication, pp. 1 - 8, March 2011.
[8] M. A. Salas Natera, R. Martínez, L. De Haro Ariet and M. Sierra Pérez, "Calibration Proposal for New Antenna Array Architectures and Technologies for Space Communications," IEEE Antennas and Wireless Propagation Letters, vol. 11, pp. 1129 - 1132, August 2012.
[9] M. A. Salas Natera, R. Martínez and L. De Haro Ariet, "Procedure for Measurement, Characterization, and Calibration of Active Antenna Arrays," IEEE Transactions on Intrumentation and Measurement, vol. 62, no. 2, pp. 377 - 391, September 2012.
[10] S. Liu, B. Tomasic, S. Hwang and J. Turtle, "The Geodesic Dome Phased Array Antenna (GDPAA) for Satellite Operations Support," in IEEE 18th International Conference on Applied Electromagnetics and Communications, Dubrovnik, April 2006.
[11] B. Tomasic, "Analysis and Design Trade-Offs of Candidate Phased Array Architectures for AFSCN Application," in Second AFSCN Phased Array Antenna Workshop, Hanscom, April 1998
[12] M. Sierra Pérez, A. Torre, J. L. Masa Campos, D. Ktorza and I. Montesinos, "GEODA: Adaptive Antenna Array for Metop Satellite Signal Reception," in 4th ESA International Workshop on Tracking, Telemetry and Command System for Space Application, Darmstadt, September 2007.
[13] M. Arias Campo, I. Montesinos Ortego, J. L. Fernández Jambrina and M. Sierra Pérez, "GEODA – GRUA: Diseño del módulo T/R," in XXIV Simposium Nacional de la Unión Científica de Radio, Santander, Septiembre 2009.
[14] M. A. Salas Natera, R. Martínez Rodríguez-Osorio and I. García-Rojo López, "Design of an Adaptive Antenna Array Test-Bed based on Software Radio for Tracking LEO Satellites," in IEEE EuCAP, Edinburgh, 2007.
[15] M. A. Salas Natera, I. Montesinos, M. Sierra Pérez, J. L. Fernández-Jambrina and R. Martínez Rodríguez-Osorio, "Desarrollo de Sistemas de Medidas y caracterización automatizado para la Antena GEODA," in XXIV Simposium Nacional de la Unión Científica Internacional de Radio, URSI2009, Santander, Spain, 2009.
[16] M. A. Salas Natera, R. Martínez, L. De Haro Ariet and J. Fernández Jambrina, "Automated System for Measurement and Characterization of Planar Active Arrays," in IEEE Internationa Symposium on Phase Array Systems and Technology, Boston, 2010.
[17] M. A. Salas Natera, R. Martínez and L. De Haro Ariet, "Automated Procedure for Measurement, Characterization and Calibration of Active Antenna Arrays," IEEE Transactions on Intrumentation and Measurement, vol. Acepted for publication, pp. 1 - 8, 2011.
[18] M. A. Salas Natera, R. Martínez and L. De Haro Ariet, "Automated measurement procedure for the calibration of planar active arrays," in Proceedings of the Fourth European Conference on Antennas ans Propagation EuCAP, Barcelona, Spain, 2010.
[19] M. Salas Natera and R. Martínez, "Analytical Evaluation of Uncertainty on Active Antenna Arrays," IEEE Transactions on Aerospace and Electronic Systems, vol. Accepted for publication, March 2011.
[20] M. A. Salas Natera, R. Martínez Rodríguez-Osorio and L. de Haro Ariet, "Analysis of antenna array receivers configurations for satellite earth station modems," in International Symposium on Wireless Communication systems, ISWCS2007, Trondheim, 2007.
[21] M. A. Salas Natera, R. Martínez Rodríguez-Osorio, A. Antón Sánchez, I. García-Rojo and L. Cuellar, "A3TB: Adaptive Antenna Array test-bed for tracking LEO satellites based on software-defined radio," in 59th International Astronautical Congress, Glasgow, 2008.
[22] M. A. Salas Natera, R. Martínez Rodríguez-Osorio and L. de Haro Ariet, "Preliminary Analysis of the Calibration Procedures for a Geodesic Antenna Array (GEODA)," in IEEE International Symposium on Antennas and Propagation, AP-S 2008, San Diego, USA, 2008.
[23] M. A. Salas Natera and R. Martínez Rodríguez-Osorio, "Prototipo Software Radio de receptor CFD-FED para seguimiento de satélites," in XXII Simposium Nacional de la Unión Científica Internacional de Radio, URSI2007, Tenerife, Spain, 2007

 

 

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