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  • 1.
    Alepuz, Javier Pérez
    et al.
    University of Alicante.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Pomares, Jorge
    University of Alicante.
    Direct image-based visual servoing of free-floating space manipulators2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 55, 1-9 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents an image-based controller to perform the guidance of a free-floating robot manipulator. The manipulator has an eye-in-hand camera system, and is attached to a base satellite. The base is completely free and floating in space with no attitude control, and thus, freely reacting to the movements of the robot manipulator attached to it. The proposed image-based approach uses the system's kinematics and dynamics model, not only to achieve a desired location with respect to an observed object in space, but also to follow a desired trajectory with respect to the object. To do this, the paper presents an optimal control approach to guiding the free-floating satellite-mounted robot, using visual information and considering the optimization of the motor commands with respect to a specified metric along with chaos compensation. The proposed controller is applied to the visual control of a four-degree-of-freedom robot manipulator in different scenarios.

  • 2.
    Andersson, Kent
    Swedish Defence University, Department of Military Studies, Military-Technology Division.
    Modeling the impact of surface emissivity on the military utility of attack aircraft2017In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 65, 133-140 p.Article in journal (Refereed)
    Abstract [en]

    An analysis scheme and a mission system model were applied to the evaluation of the military utility of efforts to reduce infrared signature in the conceptual design of survivable aircraft. The purpose is twofold: Firstly, to contribute to the development of a methodological framework for assessing the military utility of spectral design, and secondly to assess the threat from advances in LWIR sensors and their use in surface-to-air-missile systems. The modeling was specifically applied to the problem of linking the emissivity of aircraft coatings to mission accomplishment. The overall results indicate that the analysis scheme and mission system model applied are feasible for assessing the military utility of spectral design and for supporting decision-making in the concept phase. The analysis of different strike options suggests that LWIR sensors will enhance the military utility of low emissive paint, at least for missions executed in clear weather conditions. Furthermore, results corroborate and further clarify the importance of including earthshine when modeling.

  • 3.
    Andersson, Kent
    Swedish Defence University, Department of Military Studies, Military-Technology Division. National Defence University, P.O. Box 7, FI-00861 Helsinki, Finland.
    Modeling the impact of surface emissivity on the military utility of attack aircraft2017In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 65, 133-140 p.Article in journal (Refereed)
    Abstract [en]

    An analysis scheme and a mission system model were applied to the evaluation of the military utility of efforts to reduce infrared signature in the conceptual design of survivable aircraft. The purpose is twofold: Firstly, to contribute to the development of a methodological framework for assessing the military utility of spectral design, and secondly to assess the threat from advances in LWIR sensors and their use in surface-to-air-missile systems. The modeling was specifically applied to the problem of linking the emissivity of aircraft coatings to mission accomplishment. The overall results indicate that the analysis scheme and mission system model applied are feasible for assessing the military utility of spectral design and for supporting decision-making in the concept phase. The analysis of different strike options suggests that LWIR sensors will enhance the military utility of low emissive paint, at least for missions executed in clear weather conditions. Furthermore, results corroborate and further clarify the importance of including earthshine when modeling.

  • 4.
    Berggren, Daniel
    KTH, Superseded Departments, Aeronautical Engineering.
    Investigation of limit cycle oscillations for a wing section with nonlinear stiffness2004In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 8, no 1, 27-34 p.Article in journal (Refereed)
    Abstract [en]

    A wind tunnel experiment is designed with the objective to obtain well-behaved limit cycle oscillations for a wing section with two degrees of freedom, translation and rotation, in two-dimensional flow. This is accomplished using a setup of linear springs so that the resulting moment is a nonlinear function of the rotation angle. The experimental setup is designed so that the amplitudes of the limit cycle oscillations are sufficiently low to motivate the use of linear aerodynamics in the analysis. The experimental results are compared to analyses for two different configurations, and the agreement is fairly good.

  • 5.
    Carlsson, Martin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Cronander, Carin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efficient roll control using distributed control surfaces and aeroelastic effects2005In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 9, no 2, 143-150 p.Article in journal (Refereed)
    Abstract [en]

    The potential of using multiple leading and trailing edge control surfaces and aeroelastic effects for efficient roll manoeuvring is investigated. Numerical optimization in combination with a simulation model including aeroelastic dynamics is used to design a controller for roll angle tracking. The controller distributes the control power to the individual surfaces such that it minimizes the control effort yet fulfilling roll performance requirements in a wide airspeed envelope. The controller is implemented and experimentally validated using an elastic wind-tunnel model equipped with 16 individual control surfaces. Good correlation between simulations and experiments is obtained although some deviations are observed and discussed. Finally, the choice of the most efficient control surface layout is investigated by evaluating control laws which utilize a subset of the available control surfaces.

  • 6. Cronander, C.
    et al.
    Ringertz, Ulf
    KTH, Superseded Departments, Vehicle Engineering.
    Closed loop roll control using aeroelastic information2000In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 4, no 7, 481-494 p.Article in journal (Refereed)
    Abstract [en]

    A mathematical model of the rolling dynamics of a flexible wing is derived by experimental measurements and 3D potential flow analysis. Based on the mathematical model which includes one aeroelastic parameter, control laws are designed which almost completely eliminate the problem of reduced aileron efficiency for increasing airspeed. Finally, the control laws are tested on the model in the wind tunnel, and good correlation with computer simulations is achieved, except when a structural mode is excited.

  • 7. Ericsson, A.
    et al.
    Rumpler, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Sjöberg, D.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Wellander, N.
    Johansson, J.
    A combined electromagnetic and acoustic analysis of a triaxial carbon fiber weave for reflector antenna applications2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 58, 401-417 p.Article in journal (Refereed)
    Abstract [en]

    Fiber composites are widely used for space applications such as antennas, solar panels and spacecraft support structures. This paper presents a combined electromagnetic and acoustic analysis of a triaxial carbon fiber weave structure, designed for ultra lightweight reflector antennas in satellite communication systems. The electromagnetic and acoustic performance of the structure are analyzed over a wide range of parametric studies, both at a microscopic and mesoscopic length scale. The electromagnetic study indicates that the main parameter governing the electromagnetic reflection performance of the weave is the electric conductivity of the carbon fibers, given that the weave structure is significantly smaller than the wavelength of the incident signals. The acoustic study identifies a critical threshold in the mesoscale geometry in order to avoid a critically high resistive behavior of the weave structure, driven by viscous effects. Design guidelines are drawn from these analyses in order to achieve a trade-off between the electromagnetic reflection properties and the resistance to acoustic loading of such composite materials. These combined analyses allow to deepen the understanding from both an electromagnetic and acoustic perspective in order to open for some new design possibilities.

  • 8.
    Felicetti, Leonard
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Palmerini, Giovanni B.
    Sapienza Università di Roma, Dipartimento di Ingegneria Astronautica Elettrica Ed Energetica (DIAEE).
    Three spacecraft formation control by means of electrostatic forces2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 48, 261-271 p.Article in journal (Refereed)
    Abstract [en]

    This paper focuses on electrostatic orbital control in formation flying by using switching strategies for charge distribution. Natural and artificial charging effects are taken into account, and limits in charging technology and in power requirements are also considered. The case of three spacecraft formation, which is intrinsically different and more difficult than the two spacecraft problem often analyzed in literature, has been investigated. A Lyapunov based global control strategy is presented and applied to perform formation acquisition and maintenance maneuvers, producing as output the required overall charge. Then, a selective and optimized charge distribution process among the satellites is discussed for avoiding charge breakdowns to surrounding plasma, for reducing the power requirements and the number of charge switches. The results of numerical simulations show the advantages and drawbacks of the selected control technique

  • 9.
    Felicetti, Leonard
    et al.
    University of Rome la Sapienza.
    Santoni, Fabio
    Università di Roma la Sapienza, Dipartimento di Ingegneria Astronautica Elettrica Ed Energetica (DIAEE).
    Nanosatellite swarm missions in low Earth orbit using laser propulsion2013In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 27, no 1, 179-187 p.Article in journal (Refereed)
    Abstract [en]

    Many missions could benefit from the exploitation of very low height orbits, including Earth observation, atmospheric measurement and space weather research missions. However satellite's lifetime decreases very quickly when the mission requires to orbit into the dense layers of the atmosphere. The mission performance could be enhanced using innovative propulsion techniques, counteracting the effect of atmospheric drag. Among these, laser propulsion potentially offers great weight and power savings, obtained by separating the propulsion system energy source from the propelled satellite. The energy source for the propulsion system is a pulsed laser beam generated remotely, while only collecting mirrors and ablative material are necessary on the target spacecraft. A mission architecture for very low altitude nanosatellite swarms using a space-based pulsed laser propulsion is described. A simplified laser-sustained re-orbiting maneuver sequence is proposed, leading to a straightforward evaluation of the maneuver times, showing that the laser propulsion system is suitable for low altitude nanosatellite missions

  • 10. Franke, M.
    et al.
    Wallin, Stefan
    Thiele, F.
    Assessment of explicit algebraic Reynolds-stress turbulence models in aerodynamic computations2005In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 9, no 7, 573-581 p.Article in journal (Refereed)
    Abstract [en]

    In the aerodynamic industrial design process, the use of numerical simulation, including viscous effects, is of ever increasing importance. As simple, standard Boussinesq-viscosity turbulence models have proven insufficient to correctly predict complex flow situations, attention is drawn to more reliable approaches towards the modelling of turbulence. This work aims at assessing the potential of Explicit Algebraic Reynolds Stress Models (EARSM) for application-oriented aerodynamic computations. To this end, two different EARSM are investigated on a variety of configurations in sub- and transonic steady flow, ranging from 2D aerofoils to 3D wing/body-configurations. Is is demonstrated that an increased over-all simulation quality is achieved. Thus, while their overhead with respect to standard linear approaches remains limited, EARSM constitute a valuable extension to the model range available to the aerodynamic design engineer.

  • 11. Frink, N. T.
    et al.
    Tomac, Maximillian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Collaborative study of incipient separation on 53°-swept diamond wing2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219Article in journal (Refereed)
    Abstract [en]

    A systematic analysis of incipient separation and subsequent vortex formation from moderately-swept blunt leading edges is presented for a 53°-swept diamond wing. This work contributes to a collective body of knowledge generated within the multinational NATO/STO AVT-183 Task Group titled "Reliable Prediction of Separated Flow Onset and Progression for Air and Sea Vehicles". Details of vortex formation are inferred from numerical solutions of two flow solvers after establishing a good correlation of the global flow field and surface pressure distributions with those from wind tunnel measurements. From this, significant and sometimes surprising insights into the nature of incipient separation and part-span vortex formation are derived from the wealth of information available in the computational solutions.

  • 12.
    Girodroux-Lavigne, P.
    et al.
    ONERA, DDSS/MS, BP72, 92322 Châtillon Cedex, France.
    Grisval, J.P.
    ONERA, DDSS/MS, BP72, 92322 Châtillon Cedex, France.
    Guillemot, S.
    DASSAULT Aviation, DGT/DTA/IAP, 92214, Saint-Cloud Cedex, France.
    Henshaw, M.
    BAE Systems, Aerodynamic Technology Dept., Brough, E. Yorks, United Kingdom.
    Karlsson, A.
    Selmin, V.
    ALENIA Aeronautica, 10146 Torino, Italy.
    Smith, J.
    FOI Swedish Defence Research Agency, FFA Aeronautics Division, 17290 Stockholm, Sweden.
    Teupootahiti, E.
    DASSAULT Aviation, DGT/DTA/IAP, 92214, Saint-Cloud Cedex, France.
    Winzell, B.
    Comparison of static and dynamic fluid-structure interaction solutions in the case of a highly flexible modern transport aircraft wing2003In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 7, no 2, 121-133 p.Article in journal (Refereed)
    Abstract [en]

    This paper describes the computational work performed by five of the fifteen partners in the Brite-Euram project UNSI, for the prediction of static aeroelastic configurations and dynamic flutter response at transonic conditions, using advanced time-domain fluid-structure coupling methods. The aerodynamic models, mechanical models, and coupling strategies implemented in the different solvers are presented. A code to code validation of the fluid-structure coupled solvers has been achieved in the case of the highly flexible MDO wing. The coupled codes have each been used first for the computation of steady state flow and static deformations at different flight conditions. The investigation of flutter has been carried out for off-design, heavy-cruise flight conditions, using time-consistent numerical simulations. Dynamic responses have been recorded and compared for stable and flutter conditions. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

  • 13. Gledhill, Igle M. A.
    et al.
    Forsberg, Karl
    Eliasson, Peter
    Baloyi, Jeffrey
    Nordström, Jan
    Uppsala universitet, Avdelningen för teknisk databehandling.
    Investigation of acceleration effects on missile aerodynamics using computational fluid dynamics2009In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 13, 197-203 p.Article in journal (Refereed)
  • 14. Gledhill, Igle M. A.
    et al.
    Forsberg, Karl
    Eliasson, Peter
    Baloyi, Jeffrey
    Nordström, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Investigation of acceleration effects on missile aerodynamics using computational fluid dynamics2009In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 13, 197-203 p.Article in journal (Refereed)
  • 15.
    Göransson, Peter
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Tailored acoustic and vibrational damping in porous solids - Engineering performance in aerospace applications2008In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 12, no 1, 26-41 p.Article in journal (Refereed)
    Abstract [en]

    A porous solid, saturated with fluid, may be described as an elastic-viscoelastic and acoustic-viscoacoustic medium. The transport of vibroacoustic energy is carried both through the sound pressure waves propagating through the fluid in the pores, and through the elastic stress waves, carried through the solid frame of the material. For most porous materials, used to reduce sound and vibration, these waves are coupled to each other, i.e. they simultaneously propagate in both the fluid and the solid frame but with different strengths. A characteristic of this coupled wave propagation, is that the vibroacoustic energy is dissipated and converted into heat as the wave travels through the material. Clearly for a given situation, the balance between energy dissipated through vibration of the solid frame and changes in the acoustic pressure varies with the topological arrangement, choice of material properties, interfacial conditions, etc. This paper illustrates the influence such a balancing has on the performance of a multi-layer sound proofing arrangement applicable for an aircraft interior.

  • 16. Haggmark, C. P.
    et al.
    Hildings, C.
    Henningson, Dan S.
    KTH, Superseded Departments, Mechanics.
    A numerical and experimental study of a transitional separation bubble2001In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 5, no 5, 317-328 p.Article in journal (Refereed)
    Abstract [en]

    A combined numerical and experimental study of a two-dimensional transitional separation bubble due to an adverse pressure gradient is reported. The experiments have been performed in the MTL wind tunnel with a contoured wall imposing an adverse pressure gradient on the flow over a flat plate. The separated shear-layer is highly unstable and transition to turbulence occurs in the flow. The experimental separation bubble flow is modelled numerically using two-dimensional direct numerical simulations (DNS). Prescribing free stream boundary conditions in the wall normal velocity the experimental bubble is reproduced. The development of artificially forced two-dimensional instability waves is investigated and good agreement is found between experiments, simulations and linear stability theory (LST). The performance of several engineering transition prediction methods applied on the present separation bubble is presented and compared. Methods based on simplifications of the e(n)-method yield predictions in accordance with experiments and DNS.

  • 17.
    Jacobsen, Marianne
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Real time drag minimization using redundant control surfaces2006In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 10, no 7, 574-580 p.Article in journal (Refereed)
    Abstract [en]

    A method for minimizing the drag of a wind tunnel model with multiple control surfaces is presented. The minimization is performed in the wind tunnel and measurements are performed in real time. Real time measurements introduce difficulties such as noise in the signals, hysteresis and problems with repeatability of the function evaluations. The lack of a numerical function to minimize therefore puts certain demands on the optimization method, and hence a derivative free method, often referred to as a generating set search method, is used. The proposed method is generalized to take both linear equality constraints as well as linear inequality constraints into account. The generating set search method is implemented in the wind tunnel and tests show that the drag can be decreased while satisfying the constraints.

  • 18.
    Jacobsen, Marianne
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Ringertz, Ulf
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Flight Dynamics.
    Reducing emissions using aircraft trajectory optimizationIn: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219Article in journal (Other academic)
    Abstract [en]

    Optimal aircraft trajectories reducing engine emissions are computed using numerical optimization. The emissions from the jet engine are modeled as functions of the aircraft altitude, airspeed and throttle setting. Combining the emission models with a performance model of the aircraft, the optimization problem is formulated with the objective of reducing emissions for a given distance flight. The resulting problem, involving a system of differential and algebraic equations, is discretized using collocation and the optimization problem is solved using sequential quadratic programming. Different objectives are investigated, such as minimizing the total emissions of carbon dioxide, carbon monoxide, oxides of nitrogen and hydrocarbons during a flight. Methods from life cycle impact assessment are used to weigh the different emissions to an index and several different indices are used and compared. A model of the Boeing 737-600 is used to illustrate the developed optimization method. The results show that the trajectories differ significantly depending on the chosen objective. Using a combination of objectives at different altitudes may give the most appropriate problem formulation.

  • 19.
    Kapidzic, Zlatan
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Nilsson, Larsgunnar
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
    Ansell, Hans
    Saab AB, Linköping, Sweden.
    Conceptual studies of a composite-aluminum hybrid wing box demonstrator2014In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 32, no 1, 42-50 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a study of two different hybrid composite-aluminum concepts applied to a winglike structure which is exposed to mechanical  and thermal load. The aim of the study is to determine the most suitable  hybrid concept to later on be used in structural fatigue and static testing. In both concepts, the mass is optimized with respect to two different sets of requirements, one of which is currently in use in the fighter aircraft industry and one which is a modified version of the current requirement set. The issues considered in the study are mass, thermal behavior, buckling, bolted joints, failure criteria and fatigue damage, and they are examined in the frame of both requirement sets. The results clearly indicate the order of criticality between the different criteria in the different parts of each concept. Also, the comparison of two requirement sets gives an idea of the degree of influence of the modified criteria on the hybrid concepts and their mass. Based on the mass and the structural behavior in a thermal-mechanical loading one of the hybrid concepts is chosen for further studies and testing.

  • 20.
    Majić, Frane
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Efraimsson, Gunilla
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Potential improvement of aerodynamic performance by morphing the nacelle inlet2016In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 54, 122-131 p.Article in journal (Refereed)
    Abstract [en]

    In this work numerical investigations of the aerodynamic performance of an adaptive turbofan-engine inlet is performed. The adaptation is made on the inner front part of the symmetric inlet by changing the positions of two contour knots, which acts as a possible inlet struc- ture morphing. The contour knots are moved in the axisymmetric and radial directions of the inlet, respectively. The numerical calcula- tions are performed using Reynolds Averaged Navier-Stokes (RANS) simulations and are made for climb and cruise flight conditions. The evaluation of the aerodynamic performance is based on the absolute total pressure recovery at the fan plane. The results show that the adaptation of only a small part of the inlet contour gives benefits in the performance at different flight conditions. The radial position in- crease of the knot closer to the leading edge gives overall increase of the pressure recovery level for both flight conditions. The radial posi- tion change of the knot close to the throat diameter leads to the global maximum of absolute total pressure recovery almost independent of the axial position change of the same knot, for both flight conditions. These maximums are attained at different radial positions of the knot close to the throat diameter, for the two flight conditions.

  • 21.
    Marcus, Carina
    et al.
    Saab AB, Linköping, Sweden; Linköpings Universitet, Sweden.
    Andersson, Kent
    Swedish Defence University, Department of Military Studies, Military-Technology Division. Swedish Defence University, Department of Military Studies, Science of Command and Control and Military Technology Division, Military Technology Systems Section. National Defence University, Helsinki, Finland.
    Åkerlind, Christina
    Försvarets Forskningsinstitut, FOI, Sweden; Linköping University, Linköping, Sweden.
    Balancing the radar and long wavelength infrared signature properties in concept analysis of combat aircraft – A proof of concept2017In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 71, 733-741 p.Article in journal (Refereed)
    Abstract [en]

    Designing combat aircraft with high military effectiveness, affordability and military suitability requires balancing the efforts of many engineering disciplines during all phases of the development. One particular challenge is aircraft survivability, the aircraft's ability to avoid or withstand hostile actions. Signature management is one way of increasing the survivability by improving the ability to avoid detection. Here, the long-wave infrared and radar signatures are studied simultaneously in a mission context. By establishing a system of systems approach at mission system level, the risk of sub optimization at a technical level is greatly reduced. A relevant scenario is presented where the aim is to incapacitate an air-defense system using three different tactics: A low-altitude cruise missile option, a low and medium altitude combat aircraft option. The technical sub-models, i.e. the properties of the signatures, the weapons and the sensors are modeled to a level suitable for early concept development. The results from the scenario simulations are useful for a relative comparison of properties. Depending on the situation, first detection is made by either radar or infrared sensors. Although the modeling is basic, the complexity of the infrared signature and detection chain is demonstrated and possible pivot points for the balancing of radar and IR signature requirements are identified. The evaluation methodology can be used for qualitative evaluation of aircraft concepts at different design phases, provided that the technical models are adapted to a suitable level of detail.

  • 22.
    Marcus, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Saab AB, SE-58188 Linkoping, Sweden.
    Andersson, Kent
    Swedish Def University, Sweden; National Def University, Finland.
    Åkerlind, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Swedish Def Research Agency, Sweden.
    Balancing the radar and long wavelength infrared signature properties in concept analysis of combat aircraft - A proof of concept2017In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 71, 733-741 p.Article in journal (Refereed)
    Abstract [en]

    Designing combat aircraft with high military effectiveness, affordability and military suitability requires balancing the efforts of many engineering disciplines during all phases of the development. One particular challenge is aircraft survivability, the aircrafts ability to avoid or withstand hostile actions. Signature management is one way of increasing the survivability by improving the ability to avoid detection. Here, the long-wave infrared and radar signatures are studied simultaneously in a mission context. By establishing a system of systems approach at mission system level, the risk of sub optimization at a technical level is greatly reduced. A relevant scenario is presented where the aim is to incapacitate an air-defense system using three different tactics: A low-altitude cruise missile option, a low and medium altitude combat aircraft option. The technical sub-models, i.e. the properties of the signatures, the weapons and the sensors are modeled to a level suitable for early concept development. The results from the scenario simulations are useful for a relative comparison of properties. Depending on the situation, first detection is made by either radar or infrared sensors. Although the modeling is basic, the complexity of the infrared signature and detection chain is demonstrated and possible pivot points for the balancing of radar and IR signature requirements are identified. The evaluation methodology can be used for qualitative evaluation of aircraft concepts at different design phases, provided that the technical models are adapted to a suitable level of detail. (C) 2017 Elsevier Masson SAS. All rights reserved.

  • 23. Mendenhall, M.R.
    et al.
    Perkins, S.C.
    Tomac, Maximilian
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Rizzi, Arthur
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
    Nangia, Raj K.
    Nangia Aero Research Associates.
    Comparing and benchmarking engineering methods for the prediction of X-31 aerodynamics2012In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 20, no 1, 12-20 p.Article in journal (Refereed)
    Abstract [en]

    A number of useful engineering methods are available for fast and economic estimates of the aerodynamic characteristics of complex flight vehicles. This article investigates the application of three specific engineering methods to the X-31 fighter configuration, and CFD, wind tunnel, and flight test data are used for comparison and evaluation purposes. The emphasis is on static longitudinal stability aspects up to high angles of attack; however, selected asymmetric and unsteady effects are considered. Results from the engineering methods are in good agreement with experiment and CFD for angles of attack up to 15° for most cases and higher angles for some cases. Results for pitching moment are in good agreement with CFD, but many of the nonlinear characteristics of the airplane are not predicted by the engineering methods. The quality of the longitudinal stability results is discussed in terms of the prediction of the center of pressure on the vehicle. The results provide improved understanding of the continued usefulness of engineering methods as an analysis tool during the design phase and into the flight test diagnostic phase of a new aircraft.

  • 24.
    Niemi, Antti
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Ghommem, Mehdi
    Collier, Nathan
    Calo, Victor
    On the shape optimization of flapping wings and their performance analysis2014In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, 274-292 p.Article in journal (Refereed)
    Abstract [en]

    The present work is concerned with the shape optimization of flapping wings in forward flight. The analysis is performed by combining a gradient-based optimizer with the unsteady vortex lattice method (UVLM). We describe the UVLM simulation procedure and provide the first methodology to select properly the mesh and time-step sizes to achieve invariant UVLM simulation results under mesh refinement. Our objective is to identify a set of optimized shapes that maximize the propulsive efficiency, defined as the ratio of the propulsive power over the aerodynamic power, under lift, thrust, and area constraints. Several parameters affecting flight performance are investigated and their impact is described. These include the wingʼs aspect ratio, camber line, and curvature of the leading and trailing edges. This study provides guidance for shape design of engineered flying systems.

  • 25.
    Pisculli, Andrea
    et al.
    University of Rome la Sapienza, Dipartimento di Ingegneria Meccanica e Aeronautica (DIMA), University of Rome la Sapienza.
    Felicetti, Leonard
    Dipartimento di Ingegneria Astronautica Elettrica Ed Energetica (DIAEE).
    Gasbarri, Paolo
    University of Rome la Sapienza, Dipartimento di Ingegneria Meccanica e Aeronautica (DIMA), University of Rome la Sapienza.
    Palmerini, Giovanni B.
    Sapienza Università di Roma, Dipartimento di Ingegneria Astronautica Elettrica Ed Energetica (DIAEE).
    Sabatini, Marco
    University of Rome la Sapienza, Dipartimento di Ingegneria Astronautica Elettrica Ed Energetica (DIAEE).
    A reaction-null/Jacobian transpose control strategy with gravity gradient compensation for on-orbit space manipulators2014In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 36, 30-40 p.Article in journal (Refereed)
    Abstract [en]

    The dynamics and the control of space manipulators floating in 3D space is analyzed in this paper. A minimum state variable approach for describing the dynamics of a free-floating space manipulator under gravity and gravity gradient forces is presented. A new control strategy involving a combination of Reaction Null and Jacobian Transpose controllers, including also the gravity gradient compensation, is suggested and compared with the Jacobian Transpose control and the conventional Proportional Derivative control. Several numerical examples will be presented and discussed, considering platforms with single and double manipulators, showing the advantages and drawbacks related to these control strategies.

  • 26.
    Tomac, Maximilian
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Stenfelt, Gloria
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Predictions of stability and control for a flying wing2014In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 39, 179-186 p.Article in journal (Refereed)
    Abstract [en]

    The numerical simulation of a generic reduced radar signature tailless aircraft is considered. Investigation compares simulated data to low-speed wind tunnel experiments. Focus is on numerical predictions of steady longitudinal and lateral aerodynamics and influence of control surfaces on aerodynamic forces. Fully turbulent and transitional Reynolds Averaged Navier-Stokes (RANS) simulations predicted in agreement with experiment unstable pitch characteristics for low angles of attack (alpha), this was not the case for inviscid or laminar simulations. However, all simulations captured a sudden rapid increase in nose up pitch moment at higher angles of attack compared to experiments. Time accurate computations (URANS) captured non-linearity and unsteadiness in yaw moment with respect to differential split flap deflections for the studied angles of attack.

  • 27.
    Young, T.
    et al.
    Department of Mechanical Engineering, University of Limerick, Limerick, Ireland.
    Mahony, B.
    Department of Mechanical Engineering, University of Limerick, Limerick, Ireland.
    Humphreys, B.
    Aerospace Systems and Technology, Consett, Durham, United Kingdom.
    Totland, E.
    McClafferty, A.
    Department of Mechanical Engineering, University of Limerick, Limerick, Ireland.
    Corish, J.
    Department of Mechanical Engineering, University of Limerick, Limerick, Ireland.
    Durability of hybrid laminar flow control (HLFC) surfaces2003In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 7, no 3, 181-190 p.Article in journal (Refereed)
    Abstract [en]

    As a part of the European Commission sponsored HYLTEC (Hybrid Laminar Flow Technology) project, a SAAB 2000 aircraft - fitted with a number of small laser drilled panels on the wing leading edge - completed 20 months of routine service, the objective being to investigate contamination and durability aspects of Hybrid Laminar Flow Control (HLFC) suction surfaces. A post-flight test investigation of these panels, manufactured from Nd-YAG laser drilled titanium, aluminium and carbon fibre polyetheretherketone (PEEK) composite, has been conducted. Using Scanning Electron Microscopy (SEM), evidence of corrosion and damage was investigated. An optical inspection technique was used to measure hole geometries and the results were compared to pressure loss measurements through the panels. Titanium was found to be the most robust material, displaying no adverse affect from this exposure, whilst aluminium was found to be substantially less durable. The PEEK carbon fibre composite showed signs of surface degradation after only two months of flight trials. © 2003 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.

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