http://www.hindawi.comThe latest articles from Hindawi Publishing Corporation© 2012, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/ijae/2012/191879/Intergranular attack (IG) and exfoliation corrosion (EC) have a detrimental impact on the structural integrity of aircraft structures of all types. Understanding the mechanisms and methods for dealing with these processes and with corrosion in general has been and is critical to the safety of critical components of aircraft. Discussion of cases where IG attack and exfoliation caused issues in structural integrity in aircraft in operational fleets is presented herein along with a much more detailed presentation of the issues involved in dealing with corrosion of aircraft. Issues of corrosion and fatigue related to the structural integrity of aging aircraft are introduced herein. Mechanisms of pitting nucleation are discussed which include adsorption-induced, ion migration-penetration, and chemicomechanical film breakdown theories. In addition, pitting corrosion (PC) fatigue models are presented as well as a critical assessment of their application to aircraft structures and materials. Finally environmental effects on short crack behavior of materials are discussed, and a compilation of definitions related to corrosion and fatigue are presented.David W. Hoeppner and Carlos A. ArriscorretaCopyright © 2012 David W. Hoeppner and Carlos A. Arriscorreta. All rights reserved.http://www.hindawi.com/journals/ijae/2012/597930/Numerical rebuilding of two trajectory points (t=1634 s and t=1643 s) of the Fire II mission has been carried out to predict the radiative heat flux for nonequilibrium and close-to-equilibrium conditions. The simulations have been performed with eilmer3 in an uncoupled way and using a tangent slab method for the radiation transport. Different population models (QSS and Boltzmann) have been compared, and the influence of catalytic wall condition was taken into account. An analysis on the spectral range and on the spectral resolution has also been carried out.Romain Savajano, Daniel F. Potter, Ojas Joshi, and Pénélope LeylandCopyright © 2012 Romain Savajano et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/874375/Improvement of ductility at room temperature has been a major concern on processing and application of Ti aluminides over the years. Modifications in alloy chemistry of binary alloy (Ti48 Al) and processing conditions were suggested through experimental studies with limited success. Using the reported data, the present paper aims to optimize the experimental conditions through computational modeling using artificial neural network (ANN). Ductility database were prepared, and three parameters, namely, alloy type, grain size, and heat treatment cycle were selected for modeling. Additionally, ductility data were generated from the literature for training and validation of models on the basis of linearity and considering the primary effect of these three parameters. Model was trained and tested for three different datasets drawn from the generated data. Possibility of improving ductility by more than 5% is observed for multicomponent alloy with grain size of 10–50 μm following a multistep heat treatment cycle.R. K. Gupta, Rama Mehta, Vijaya Agarwala, Bhanu Pant, and P. P. SinhaCopyright © 2011 R. K. Gupta et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/154798/Reengineering of the aircraft structural life prediction process to fully exploit advances in very high performance digital computing is proposed. The proposed process utilizes an ultrahigh fidelity model of individual aircraft by tail number, a Digital Twin, to integrate computation of structural deflections and temperatures in response to flight conditions, with resulting local damage and material state evolution. A conceptual model of how the Digital Twin can be used for predicting the life of aircraft structure and assuring its structural integrity is presented. The technical challenges to developing and deploying a Digital Twin are discussed in detail.Eric J. Tuegel, Anthony R. Ingraffea, Thomas G. Eason, and S. Michael SpottswoodCopyright © 2011 Eric J. Tuegel et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/941872/Previous studies of transonic swept rotors in single stage fans have demonstrated the potential of significant improvements in both efficiency and stall margin with forward swept blading. This paper extends the assessment of the payoff derived from forward sweep to multistage configurations. The experimental investigation compare two builds of an advanced two-stage fan configuration tested alternately with a radial and a forward swept stage 1 blade. In the two-stage evaluations, the testing was extended to include the effect on inlet flow distortion. While the common second stage among the two builds prevented the overall fan from showing clean inlet performance and stability benefits with the forward swept rotor 1, this configuration did demonstrate superior front stage efficiency and tolerance to inlet distortion. Having obtained already low distortion sensitivity with the radial rotor 1 configuration relative to current production military fan standards, the sensitivity to inlet distortion was halved with the forward swept rotor 1 configuration. In the case of the 180-degree one-per-rev distortion pattern, the two-stage configuration was evaluated both with and without inlet guide vanes (IGVs). The presence of the inlet guide vanes had a profound impact in lowering the two-stage fan's sensitivity with inlet distortion.Aspi R. WadiaCopyright © 2011 Aspi R. Wadia. All rights reserved.http://www.hindawi.com/journals/ijae/2011/896836/Evaluated atomic data concerning the 4s and 4p configurations of Ar I are averaged in order to simplify their use in various cases of Ar plasma modeling and diagnostics. These data are used here to model a low-power arcjet, running with Argon at low pressure. In so doing, they are explicitly introduced in the chemical processes included in a fluid Navier-Stokes type code, allowing for evaluation of the spectroscopically measurable level populations and of the electronic temperatures. The characteristics of the model are described and the main processes are discussed in view of the results of the calculations.K. Katsonis, Ch. Berenguer, A. Kaminska, and M. DudeckCopyright © 2011 K. Katsonis et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/247294/This paper represents an efficient technique for neural network modeling of flight and space dynamics simulation. The technique will free the neural network designer from guessing the size and structure for the required neural network model and will help to minimize the number of neurons. For linear flight/space dynamics systems, the technique can find the network weights and biases directly by solving a system of linear equations without the need for training. Nonlinear flight dynamic systems can be easily modeled by training its linearized models keeping the same network structure. The training is fast, as it uses the linear system knowledge to speed up the training process. The technique is tested on different flight/space dynamic models and showed promising results.Ayman Hamdy KassemCopyright © 2011 Ayman Hamdy Kassem. All rights reserved.http://www.hindawi.com/journals/ijae/2011/156796/This paper presents a successful approach in designing a Fuzzy Logic Controller (FLC) for a specific Jet Engine. At first, a suitable mathematical model for the jet engine is presented by the aid of SIMULINK. Then by applying different reasonable fuel flow functions via the engine model, some important engine-transient operation parameters (such as thrust, compressor surge margin, turbine inlet temperature, etc.) are obtained. These parameters provide a precious database, which train a neural network. At the second step, by designing and training a feedforward multilayer perceptron neural network according to this available database; a number of different reasonable fuel flow functions for various engine acceleration operations are determined. These functions are used to define the desired fuzzy fuel functions. Indeed, the neural networks are used as an effective method to define the optimum fuzzy fuel functions. At the next step, we propose a FLC by using the engine simulation model and the neural network results. The proposed control scheme is proved by computer simulation using the designed engine model. The simulation results of engine model with FLC illustrate that the proposed controller achieves the desired performance and stability.M. Bazazzadeh, H. Badihi, and A. ShahriariCopyright © 2011 M. Bazazzadeh et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/157590/Motivated by the idea of multiplexed model predictive control (MMPC), this paper introduces a new framework for unmanned aerial vehicles (UAVs) formation flight and coordination. Formulated using MMPC approach, the whole centralized formation flight system is considered as a linear periodic system with control inputs of each UAV subsystem as its periodic inputs. Divided into decentralized subsystems, the whole formation flight system is guaranteed stable if proper terminal cost and terminal constraints are added to each decentralized MPC formulation of the UAV subsystem. The decentralized robust MPC formulation for each UAV subsystem with bounded input disturbances and model uncertainties is also presented. Furthermore, an obstacle avoidance control scheme for any shape and size of obstacles, including the nonapriorily known ones, is integrated under the unified MPC framework. The results from simulations demonstrate that the proposed framework can successfully achieve robust collision-free formation flights.Zhao Weihua and Tiauw Hiong GoCopyright © 2011 Zhao Weihua and Tiauw Hiong Go. All rights reserved.http://www.hindawi.com/journals/ijae/2011/824591/Indoor-cross infection of expiratory contaminants is still a concern, worsened by the SARS outbreak in 2003 and recent cases of influenza strains (H1N1, avian flu, etc.). A variety of methods to study the airborne spread of expiratory contaminants have been worked out, including the use of tracer gas, particle generators, and CFD simulations. In this context, the main objective of this work is reviewing methods to evaluate airborne dispersion of contaminants, more specifically those related to cross infection of expiratory droplets inside aircraft cabins. This literature review provides guidance in developing methods and choosing equipment for future studies.This study gathers knowledge developed so far in a common source, serving as a guideline for researchers who work in this area.Sandro Tavares Conceição, Marcelo Luiz Pereira, and Arlindo TribessCopyright © 2011 Sandro Tavares Conceição et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/937629/In the frame of future sample return missions to Mars, asteroids, and comets, investigated by the European Space Agency, a review of the actual aerodynamics and aerothermodynamics capabilities in Europe for Mars entry of large vehicles and high-speed Earth reentry of sample return capsule has been undertaken. Additionally, capabilities in Canada and Australia for the assessment of dynamic stability, as well as major facilities for hypersonic flows available in ISC, have been included. This paper provides an overview of European current capabilities for aerothermodynamics and testing of thermal protection systems. This assessment has allowed the identification of the needs in new facilities or upgrade of existing ground tests for covering experimentally Mars entries and Earth high-speed reentries as far as aerodynamics, aerothermodynamics, and thermal protection system testing are concerned.Mathilde Bugel, Philippe Reynier, and Arthur SmithCopyright © 2011 Mathilde Bugel et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/549131/We apply eigenstructure assignment to the design of a flight control system for a wind tunnel model of a tailless aircraft. The aircraft, known as the innovative control effectors (ICEs) aircraft, has unconventional control surfaces plus pitch and yaw thrust vectoring. We linearize the aircraft in straight and level flight at an altitude of 15,000 feet and Mach number 0.4. Then, we separately design flight control systems for the longitudinal and lateral dynamics. We use a control allocation scheme with weights so that the lateral pseudoinputs are yaw and roll moment, and the longitudinal pseudoinput is pitching moment. In contrast to previous eigenstructure assignment designs for the ICE aircraft, we consider the phugoid mode, thrust vectoring, and stability margins. We show how to simultaneously stabilize the phugoid mode, satisfy MIL-F-8785C mode specifications, and satisfy MIL-F-9490D phase and gain margin specifications. We also use a cstar command system that is preferable to earlier pitch-rate command systems. Finally, we present simulation results of the combined longitudinal/lateral flight control system using a full 6DOF nonlinear simulation with approximately 20,000 values for the aerodynamic coefficients. Our simulation includes limiters on actuator deflections, deflection rates, and control system integrators.Clara Nieto-Wire and Kenneth SobelCopyright © 2011 Clara Nieto-Wire and Kenneth Sobel. All rights reserved.http://www.hindawi.com/journals/ijae/2011/985871/The Council of Scientific and Industerial Research National Aerospace Laboratories (CSIR-NAL), Bangalore, India has been engaged in the research of autoclaves for the past three decades and has pioneered their development and usage in India for aerospace/aircraft structural applications. The autoclaves at CSIR-NAL have played a significant role in all the major national aircraft/aerospace programs. The largest aerospace autoclave in India (working size of 4.4 m diameter and 9.0 m length) has been successfully commissioned at CSIR-NAL. This paper gives the technological challenges faced and the innovative concepts that were introduced in these autoclaves.A. R. Upadhya, G. N. Dayananda, G. M. Kamalakannan, J. Ramaswamy Setty, and J. Christopher DanielCopyright © 2011 A. R. Upadhya et al. All rights reserved.http://www.hindawi.com/journals/ijae/2011/635750/A set of systematical optimum operational parameters for wind turbines under various wind directions is derived by using combined momentum-energy and blade-element-energy concepts. The derivations are solved numerically by fixing some parameters at practical values. Then, the interactions between the produced power and the influential factors of it are generated in the figures. It is shown that the maximum power produced is strongly affected by the wind direction, the tip speed, the pitch angle of the rotor, and the drag coefficient, which are specifically indicated by figures. It also turns out that the maximum power can take place at two different optimum tip speeds in some cases. The equations derived herein can also be used in the modeling of tethered wind turbines which can keep aloft and deliver energy.David A. Peters and Xi RongCopyright © 2011 David A. Peters and Xi Rong. All rights reserved.http://www.hindawi.com/journals/ijae/2011/361215/The increasing application of microsatellites (from 10 kg up to 100 kg) as well as CubeSats for a rising number of various missions demands the development of miniaturized propulsion systems. Fotec and The University of Applied Sciences at Wiener Neustadt is developing a number of micropropulsion technologies including both electric and chemical thrusters targeting high performance at small scales. Our electric propulsion developments include a series of FEEP (field emission electric propulsion) thrusters, of which the thrust ranges from μN to mN level. The thrusters are highly integrated into clusters of indium liquid-metal-ion sources that can provide ultralow thrust noise and long-term stability. We are also developing a micro PPT thruster that enables pointing capabilities for CubeSats. For chemical thrusters, we are developing novel micromonopropellant thrusters with several hundred mN as well as a 1–3 N bipropellant microrocket engine using green propellants and high specific impulse performance. This paper will give an overview of our micropropulsion developments at Fotec, highlighting performance as well as possible applications.M. Tajmar and C. A. ScharlemannCopyright © 2011 M. Tajmar and C. A. Scharlemann. All rights reserved.http://www.hindawi.com/journals/ijae/2011/476197/Using a solar sail, a spacecraft orbit can be offset from a central body such that the orbital plane is displaced from the gravitational center. Such a trajectory might be desirable for a single-spacecraft relay to support communications with an outpost at the lunar south pole. Although trajectory design within the context of the Earth-Moon restricted problem is advantageous for this problem, it is difficult to envision the design space for offset orbits. Numerical techniques to solve boundary value problems can be employed to understand this challenging dynamical regime. Numerical finite-difference schemes are simple to understand and implement. Two augmented finite-difference methods (FDMs) are developed and compared to a Hermite-Simpson collocation scheme. With 101 evenly spaced nodes, solutions from the FDM are locally accurate to within 1740 km. Other methods, such as collocation, offer more accurate solutions, but these gains are mitigated when solutions resulting from simple models are migrated to higher-fidelity models. The primary purpose of using a simple, lower-fidelity, augmented finite-difference method is to quickly and easily generate accurate trajectories.Geoffrey G. Wawrzyniak and Kathleen C. HowellCopyright © 2011 Geoffrey G. Wawrzyniak and Kathleen C. Howell. All rights reserved.http://www.hindawi.com/journals/ijae/2011/214549/Micro- and nano air vehicles are defined as “extremely small and ultra-lightweight air vehicle systems” with a maximum wingspan length of 15 cm and a weight less than 20 grams. Here, we provide a review of the current state of the art and identify the challenges of design and fabrication. Different configurations are evaluated, such as fixed wings, rotary wings, and flapping wings. The main advantages and drawbacks for each typology are identified and discussed. Special attention is given to rotary-wing vehicles (helicopter concept); including a review of their main structures, such as the airframe, energy storage, controls, and communications systems. In addition, a review of relevant sensors is also included. Examples of existing and future systems are also included. Micro- and nano-vehicles with rotary wings and rechargeable batteries are dominating. The flight times of current systems are typically around 1 hour or less due to the limited energy storage capabilities of the used rechargeable batteries. Fuel cells and ultra capacitors are promising alternative energy supply technologies for the future. Technology improvements, mainly based on micro- and nanotechnologies, are expected to continue in an evolutionary way to improve the capabilities of future micro- and nano air vehicles, giving improved flight times and payload capabilities.Luca Petricca, Per Ohlckers, and Christopher GrindeCopyright © 2011 Luca Petricca et al. All rights reserved.http://www.hindawi.com/journals/ijae/2010/874586/Unmanned aerial vehicles (UAVs) have the potential of creating an ad hoc communication network in the air. Most UAVs used in communication networks are equipped with wireless transceivers using omnidirectional antennas. In this paper, we consider a collection of UAVs that communicate through wireless links as a mobile ad-hoc network using directional antennas. The network design goal is to maximize the throughput and minimize the end-to-end delay. In this respect, we propose a new medium access control protocol for a network of UAVs with directional antennas. We analyze the communication channel between the UAVs and the effect of aircraft attitude on the network performance. Using the optimized network engineering tool (OPNET), we compare our protocol with the IEEE 802.11 protocol for omnidirectional antennas. The simulation results show performance improvement in end-to-end delay as well as throughput.Abdel Ilah Alshbatat and Liang DongCopyright © 2010 Abdel Ilah Alshbatat and Liang Dong. All rights reserved.http://www.hindawi.com/journals/ijae/2010/762329/The Routh criterion is used to assess longitudinal dynamic stability of a propeller-driven aircraft. Under a few plausible assumptions on possible ranges of the pertinent stability derivatives, it reduces to a pair of simple conditions imposing a traditional aft limit (the forward of the maneuver and the neutral-speed-stability points) on the center-of-gravity position and an upper limit on the longitudinal moment of inertia. It is demonstrated that most aircraft have sufficiently small inertia to remain stable as long as their center-of-gravity is properly placed. At the same time, sailplane-like aircraft (as, e.g., long endurance UAVs), with an engine installed at the rear extremity of the aircraft, may have sufficiently high inertia to become unstable regardless of their center-of-gravity placement.Gil IosilevskiiCopyright © 2010 Gil Iosilevskii. All rights reserved.http://www.hindawi.com/journals/ijae/2010/940528/Wind tunnel experiments were conducted on NACA-0015 airfoil model to investigate the effect of the reduced frequency (κ=0.0001 to 0.5) and that Reynolds number (Re=0.2E06 to 0.7E06) on the aerodynamic characteristics and hysteresis behavior associated with the oscillating motion of the airfoil. Pressure measurements were conducted on the midspan of the airfoil for quantitative results. Although dynamic stall study has been conducted to greater extent of reduced frequencies, for current work, emphasis is made on investigating the low reduced frequency regimes up to which the steady conditions prevail under dynamic mode of operation. In present investigations of oscillating sinusoidal α=10∘+15∘sin(ωt) motion, the airfoil was allowed to execute oscillating motion from static to almost steady (quasi-steady) conditions with the incremental increase in the reduced frequency. The limiting conditions of κ and Re for quasi-steady state are carefully extracted and analyzed. Static and quasi-steady conditions are critically assessed in context of the existence of laminar separation bubble within the opted Re regime. The flow separation was found to be trailing edge flow separation with existence of LSB upstream towards the leading edge with no evidence of unsteady flow reversals. Normal force defect and pitch damping factor are estimated for varied range of Re and κ within the quasi-steady conditions. Re effect is dominant at steady and quasi-steady regimes while the effect of reduced frequency is negligible in this domain. Minor hysteresis effect associated with the stalling and reattachment point is due to existence of weak stall flutter which is further restrained by the oscillatory motion of the airfoil. Laminar separation bubble traced during steady condition is conserved in quasi-steady domain as well.Deepakkumar M. Sharma and Kamal PoddarCopyright © 2010 Deepakkumar M. Sharma and Kamal Poddar. All rights reserved.http://www.hindawi.com/journals/ijae/2010/364859/Effects of amplitude and frequency of synthetic jet on the characteristics of induced jet are investigated. To estimate effects of the parameters, flow inside the synthetic jet cavity and orifice and the outer flow is simultaneously simulated using large-eddy simulation (LES). Comparison of the present LES result with the experimental data shows that three-dimensional LES of the flow inside the cavity is essential for accurate estimation of the velocity and velocity fluctuation of the synthetic jet. Comparison of the present results under various flow conditions shows that amplitude and frequency can control profiles of time-averaged vertical velocity and fluctuation of the vertical velocity as well as damping rate of the induced velocity and fluctuation.Koichi Okada, Akira Oyama, Kozo Fujii, and Koji MiyajiCopyright © 2010 Koichi Okada et al. All rights reserved.http://www.hindawi.com/journals/ijae/2010/156281/The paper deals with chemical contamination monitoring in phosphate-ester-based hydraulic fluids using nondispersive infrared (NDIR) optical absorption. Our results show that NDIR monitoring allows detecting the take-up of water into such fluids and their hydrolytic disintegration as these become additionally stressed by Joule heating. Observations on the O–H stretching vibration band (3200–3800 cm−1) are used for determining the free water content (0–1.5%) and the Total Acid Number (0–1 mgKOH/g). Both quantities can be assessed by monitoring the strength and the asymmetry of the O–H vibration band with regard to the free water absorption band centred around 3500 cm−1. As such optical parameters can be assessed without taking fluid samples from a pressurised hydraulic system, fluid degradation trends can be established based on regular measurements, before irreversible damage to the fluid has occurred. Therefore maintenance actions can be planned accordingly, which is very important for the airline, as unscheduled maintenance disturbs the flights organisation and often generates money loss.Sumit Paul, Wolfgang Legner, Angelika Krenkow, Gerhard Müller, Thierry Lemettais, Francois Pradat, and Delphine HertensCopyright © 2010 Sumit Paul et al. All rights reserved.http://www.hindawi.com/journals/ijae/2010/474537/Design and synthesis of a nonlinear generic supersonic flight vehicle longitudinal dynamics control for angle-of-attack, AOA, output tracking in the atmospheric flight is presented based on sliding mode control. A sliding mode observer is invoked to estimate AOA which is difficult to measure in practice. Large parameter uncertainties accommodation envisaged by designing adaptive mechanisms for both the control and observer and high chattering authority due to large deviations of aerodynamic coefficients arising from wind-tunnel measurements are inhibited. The employed method enables the sliding mode control design to exhibit the desired dynamic properties during the entire output-tracking process. Simulations results are presented to demonstrate the performance, robustness, and stability.M. Bahrami, B. Ebrahimi, and G. R. AnsarifarCopyright © 2010 M. Bahrami et al. All rights reserved.http://www.hindawi.com/journals/ijae/2010/389832/The paper deals with the evaluation of the expected performance of aircraft approaches and landings operated with different navigation systems, both traditional and satellite-based. Flight dynamics characteristics and control authority of the approaching aircraft are considered in order to obtain an overall manoeuvre evaluation. The technique from the presented analysis applies to different operative conditions, taking into account aircraft requirements, navigation systems features, and environmental constraints. The aim is to offer a tool to be used in the very preliminary design phase for system performance analysis in different scenarios, such as airport ground systems adoption and air traffic control requirements compliance; later, the same tool can be tuned to complement and direct the required real flight trials to validate an already fielded solution. A numerical code referring to the presented analytical model has been implemented and some applications concerning the system's performance evaluation and planning are proposed to illustrate the algorithm capabilities. The tool and the proposed analysis technique indeed are successful in providing a quantitative assessment of the differences among several possible approaches.Pier Domenico Tromboni and Giovanni B. PalmeriniCopyright © 2010 Pier Domenico Tromboni and Giovanni B. Palmerini. All rights reserved.http://www.hindawi.com/journals/ijae/2010/257957/This paper is concerned with modeling of ablation behavior of carbon-carbon composites used in hot spot areas of reentry space and hypersonic vehicles. Of the three modes of ablation (thermal, chemical and mechanical), the chemical (oxidation) is considered to influence the performance of the material. Aerodynamic heat flux need to be computed separately and is the input for this. The thermal field is obtained by 3D finite element method. Nonlinear transient thermal analysis is carried out, as the material properties are dependent on temperatures. Oxidation rates are computed using the analytical relations available in literature. The oxidation is divided into two regimes: reaction rate and diffusion rate controlled. Mainly the surface temperature controls the regime. The oxidation protected materials are considered by using the parameter “activation energy.” The variations of ambient temperature, pressure and oxygen concentration with altitude are taken into consideration. As the recession takes place, newer surfaces are exposed to aerodynamic heating. Numerical examples are presented to show the effects of: heat flux, altitude and oxidation protection on the recession characteristics. Change of regime from reaction to diffusion rate control depends on parameters such as flow velocity and altitude. The latter has significant influence on ablation rate.R. PalaninathanCopyright © 2010 R. Palaninathan. All rights reserved.http://www.hindawi.com/journals/ijae/2009/793647/This paper considers the numerical optimization of a double ramp scramjet inlet using magnetohydrodynamic (MHD) effects together with inlet ramp angle changes. The parameter being optimized is the mass capture at the throat of the inlet, such that spillage effects for less than design Mach numbers are reduced. The control parameters for the optimization include the MHD effects in conjunction with ramp angle changes. To enhance the MHD effects different ionization scenarios depending upon the alignment of the magnetic field are considered. The flow solution is based on the Advection Upstream Splitting Method (AUSM) that accounts for the MHD source terms as well. A numerical Broyden-Flecher-Goldfarb-Shanno- (BFGS-) based procedure is utilized to optimize the inlet mass capture. Numerical validation results compared to published results in the literature as well as the outcome of the optimization procedure are summarized to illustrate the efficacy of the approach.Kamesh Subbarao and Jennifer D. GossCopyright © 2009 Kamesh Subbarao and Jennifer D. Goss. All rights reserved.http://www.hindawi.com/journals/ijae/2009/409529/This paper compares the analysis of systems from two different perspectives: an energy-based focus and an exergy-based focus. A complex system was simply modeled as interacting thermodynamic systems to illustrate the differences in analysis methodologies and results. The energy-based analysis had combinations of calculated states that are infeasible. On the other hand, the exergy-based analyses only allow feasible states. More importantly, the exergy-based analyses provide clearer insight to the combination of operating conditions for optimum system-level performance. The results strongly suggest changing the analysis/design paradigm used in aerospace engineering from energy-based to exergy-based. This methodology shift is even more critical in exploratory research and development where previous experience may not be available to provide guidance. Although the models used herein may appear simplistic, the message is very powerful and extensible to higher-fidelity models: the 1st Law is only a necessary condition for design, whereas the 1st and 2nd Laws provide the sufficiency condition.John H. Doty, José A. Camberos, and David J. MoorhouseCopyright © 2009 John H. Doty et al. All rights reserved.http://www.hindawi.com/journals/ijae/2009/561495/This paper introduces a new set of orbits, the “Repeated Shadow Track Orbits.” In these orbits, the shadow of a spacecraft on the Earth visits the same locations periodically every desired number of days. The J2 perturbation is utilized to synchronize the spacecraft shadow motion with both the Earth rotational motion and the Earth-Sun vector rotation. Motivation for the design of new shadow track orbits comes from the need to save energy. The general mathematical model to design a Repeated Shadow Track Orbit (RSTO) is presented within this paper. RSTOs' conditions are formulated and numerically solved. Results show the feasibility of RSTOs. An optimization process is also developed to maximize the shadow duration over a given site. A Genetic Algorithm (GA) technique is utilized for optimization.Ahmed Gad and Ossama AbdelkhalikCopyright © 2009 Ahmed Gad and Ossama Abdelkhalik. All rights reserved.http://www.hindawi.com/journals/ijae/2009/531358/A new approach to optimize the geometry of a turbine airfoil by simultaneously designing multiple 2D sections of the airfoil is presented in this paper. The complexity of 3D geometry modeling is circumvented by generating multiple 2D airfoil sections and constraining their geometry in the radial direction using first- and second-order polynomials that ensure smoothness in the radial direction. The flow fields of candidate geometries obtained during optimization are evaluated using a quasi-3D, inviscid, CFD analysis code. An inviscid flow solver is used to reduce the execution time of the analysis. Multiple evaluation criteria based on the Mach number profile obtained from the analysis of each airfoil cross-section are used for computing a quality metric. A key contribution of the paper is the development of metrics that emulate the perception of the human designer in visually evaluating the Mach Number distribution. A mathematical representation of the evaluation criteria coupled with a parametric geometry generator enables the use of formal optimization techniques in the design. The proposed approach is implemented in the optimal design of a low-pressure turbine nozzle.Sanjay GoelCopyright © 2009 Sanjay Goel. All rights reserved.http://www.hindawi.com/journals/ijae/2009/735680/We address the design of a flight vehicle from the viewpoint of a system of systems and we discuss the integration of the individual technical disciplines. Then a conceptual fundamental methodology and tools required for the analysis, design, and optimization of aerospace vehicles in terms of the efficient use of on-board energy are discussed. This suggests changing the design paradigm to the optimization of a system of energy systems. We propose a foundation for system-level design with optimization based on minimum exergy destruction.José A. Camberos and David J. MoorhouseCopyright © 2009 José A. Camberos and David J. Moorhouse. All rights reserved.