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Abstract In recent years, dynamics and control of satellite formation flying have been active areas of research. From the mission planning perspective, three main areas namely formation establishment, maintenance and reconfiguration have been discussed. In this paper, a study of formation establishment under initial uncertainty is presented. In this regard, dynamics of low Earth orbit satellite formation is discussed. Control Lyapunov function approach is adopted to bring a deputy satellite, with perturbed initial conditions into formation with a chief satellite. In order to take account of the initial orbit insertion error, uncertainty in initial conditions of the deputy satellite is considered. For a case study, a relatively small formation is adopted, with air-launched Pegasus as the launch vehicle. For several initial conditions, control function and required time to achieve a given mission accuracy are determined, and results are provided as illustration.Resumo em Inglês:
Abstract: This article has discussed the development of a three-axis attitude digital controller for an artificial satellite using a digital signal processor. The main motivation of this study is the attitude control system of the satellite Multi-Mission Platform, developed by the Brazilian National Institute for Space Research for application in different sort of missions. The controller design was based on the theory of the Linear Quadratic Gaussian Regulator, synthesized from the linearized model of the motion of the satellite, i.e., the kinematics and dynamics of attitude. The attitude actuators considered in this study are pairs of cold gas jets powered by a pulse width/pulse frequency modulator. In the first stage of the project development, a system controller for continuous time was studied with the aim of testing the adequacy of the adopted control. The next steps had included an analysis of discretization techniques, the setting time of sampling rate, and the testing of the digital version of the Linear Quadratic Gaussian Regulator controller in the MATLAB/SIMULINK. To fulfill the study, the controller was implemented in a digital signal processor, specifically the Blackfin BF537 from Analog Devices, along with the pulse width/pulse frequency modulator. The validation tests used a scheme of co-simulation, where the model of the satellite was simulated in MATLAB/SIMULINK, while the controller and modulator were processed in the digital signal processor with a tool called Processor-In-the-Loop, which acted as a data communication link between both environments.function and required time to achieve a given mission accuracy are determined, and results are provided as illustration.Resumo em Inglês:
Abstract: This paper has described the radar absorbing materials characterization and radar cross section measurements, in the frequencyrange of 8 to 12 GHz, using a very simple setup. Simple targets like sphere, cylinder, flatplate, and dihedral comer were characterized by measuring the backscattered radiation patterns when these targets were illuminated by monostatic microwave radiation. Measurements were carried out inside an anechoic chamber (9x5x4m3). Typical radar cross section patterns were obtained in different aspect angles, by rotating the targets around their vertical axes. The measured values and the theoretical previsions for each metallic target showed that the used setup guarantees a good precision of the obtained data. By recovering one of the targets, a cylinder, with a specific radar absorbing material developed at Materials Division of the Brazilian Aeronautics and Space lnstitute, it was possible to compare the obtained patterns and to discuss the influence of radar absorbing materiais on the observed radar cross section reduction patterns. The used methodology showed to be useful for attending aeronautical and telecommunication applications.Resumo em Inglês:
Abstract: The combustion simulation of ammonium perchlorate was carried out with the software Chemkin, in two steps: the burning behavior of pure ammonium perchlorate and the one of formulated ammonium perchlorate with hydroxyl terminated polybutadiene binder. In both cases, the room pressure varied in order to verify its influence in the system. The burning environment conditions were diverse. During the combustion process, the data obtained from the kinetic chemistry simulation software were compiled. The flame structure can be described by the molar fraction of the burning products and the temperature evolution from the surface of the material.Resumo em Inglês:
Abstract: Poly(epichlorohydrin) was synthesized using anhydrous and hydrate stannic chloride, separately, as initiator. Reactions were conducted in the presence of a diolat 70°C. Polymers were characterized by Fourier Transform Infrared I Spectroscopy (FT-IR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and hydroxyl value determination. It was observed that water has influence in growing chain, but not in its structural backbone. Besides, the monomer/initiator relationship has a higher influence in overall poly(epichlorohydrin) properties.Resumo em Inglês:
Abstract: Electro-explosive devices (an electric resistance encapsulated by a primary explosive) fundamentally convert electrical energy into thermal energy, to start off an explosive chemical reaction. Obviously, the activation of those devices shall not happen by accident or, even worse, by intentional exogenous influence. From an ordinary differential equation, which describes the electro-explosive thermal behavior, a remarkable, but certainly not intuitive, dependence of the temperature response on the time constant of the heat transfer process is verified: the temperature profile dramatically changes as the time constant spans a wide range of values, from much lesser than the pulse width to much greater than the pulse period. Based on this dependence, important recommendations, concerning the efficient and safety operation of electro-explosive devices, are proposed.Resumo em Inglês:
Abstract: One of the major sources of stress arising in turbomachinery blades are the centrifugal loads acting at any section of the airfoil. Accounting for this phenomenon stress evaluation of the blade attachment region in the disc has to be performed in order to avoid blade failure. Turbomachinery blades are generally twisted, and the cross section area varies from the root of the blade to the tip. The blade rootshape at the attachment region is of great concern. Stress concentrations are predictable at this contact region. In this paper, a finite element model has been created for the purpose of assessing stress at the joint region connecting the blade to the disc slot. Particular attention was paid to the geometric modeling of the "fir-tree" fixing, which is now used in the majority of gas turbine engines. This study has been performed using the commercial software ANSYS13.0. The disc and blade assembly are forced to move with a certain rotational velocity. Contact connections are predicted on the common faces of the blade and on the disc at the root. Solutions can be obtained to allow the evaluation of stresses. Results can be compared with the mechanical properties of the adopted material..Resumo em Inglês:
Abstract: The purpose of this study was the temperature monitoring at bonding interface during the rotary friction welding process of dissimilar materiais: AA1050 aluminum with AISI 304 stainless steel. As it is directly related to the mechanical strenght of the junction, its experimental determination in real time is of fundamental importance for understanding and characterizing the main process steps, and the definition and optimization of parameters. The temperature gradients were obtained using a system called Thermocouple Data-Logger, which allowed monitoring and recording data in real-time operation. In the graph temperature versus time obtained, the heating rates, cooling were analyzed, and the maximum temperature was determined that occurred during welding, and characterized every phases of the process. The efficiency of this system demonstrated by experimental tests and the knowledge of the temperature at the bonding interface open new Unes of research to understand the process of friction welding.Resumo em Inglês:
Abstract: We present wind data collected for ten days during the dry season in 2008 during the Murici II Campaign, which was carried out in the area of the Centro de Lançamento de Alcântara (CLA). The main goals are to better understand processes governing the wind regime in the CLA and the development of tools for analyzing the impact of wind on rocket structure and on the dispersion of pollutants released during the launch. A set of 11 aerovanes (ten at 10-m heightandone at 1.5-m height) plus a sonic anemometer at 1.5-m heightwere deployed to measure Wind speed and direction, which were stored as ten-minute data. Turbulence intensity, gust factor, and gust amplitude were computed from the available dataset. Statistical analysis shows that the wind direction is predominant from East-Northeast (ENE), with the mean vector wind direction of 60º, in agreement with the trade wind regime. The diurnal cycle of ali statistical properties ofthe wind are strongly marked. Wind speed, turbulence intensity, and gusts are peaked at about 1000 LST. The presence of a non-diurnal cycle off our days has been noticed and might be associated with synoptic systems acting on the region. A simple heuristic formula was proposed to compute Lagrangian time-scalefrom Eulerian time-scale, and from which we compute the Lagragian standard deviation, afinal product to be used as input in diffusion models.Resumo em Inglês:
Abstract: The present work is concerned with the preliminary design of a new galley concept for long-haul airliners. Usually, galley systems are placed in the main deck of airliners or even in some cases in the lower-deck cargo compartment. The present concept considers placing trolleys, components that occupy significant room in galley installations, in the lower-deck compartment and transport them to the passenger deck by a dedicated lift system. The main advantage of this proposal is that more room becomes available in the passenger cabin for the accommodation of additional passengers. By a careful analysis, which considers the required structural modifications that must be incoporated into the airplane configuration to accommodate the new concept, the payoff of the present proposal is investigated. This was carried out by using the PADLAB® 2.4 software package, written for MATLAB®, and an in-house routine to evaluate aircraftperformance and calculation of direct operating costs per seat mile. PADLAB® is tailored to the design of the cabin and the device and systems aimed at operating the trolleys by the passenger cabin crew; the in-house routine was validated against data obtained for the category of airliners under consideration.Resumo em Inglês:
Abstract: To ensure the continuity and growth of space activities in Brazil, it is fundamental to persuade the Brazilian society and its representatives in Government about the importance of investments in space activities. Also, it is important to convince talented professionals to place space activities as an object of their interest; the best schools should also be convinced to offer courses related to the space sector; finally, innovative companies should be convinced to take part in space sector activities, looking to returns, mainly in terms of market differentiation and qualification, as a path to take part in high-technology and high-complexity projects. On the one hand, this process of convincing or, more importantly, committing these actors to space activities, implies a thorough understanding of their expectations and needs, in order to plan how the system/organization can meet them. On the other hand, if stakeholders understand how much they can benefit from this relationship, their consequent commitment will very much strengthen the action of the system/organization. With this framework in perspective, this paper proposes a methodology of stakeholder analysis for the Brazilian satellite space program. In the exercise developed in the article, stakeholders have been identified from a study of the legal framework of the Brazilian space program. Subsequently, the proposed methodology has been applied to the planning of actions by a public organization.Resumo em Inglês:
Abstract: This article is focused on the space sector, mainly due to the devices developed and marketed that require high investments in research, development and technological innovation, supported by a permanent need to meet the standard requirement to guarantee their effectiveness, among ali the correct certification. In such scenario, this article has examined, highlighting technological innovation, which are the context and elements involved in the certification of the Vehicle Survey Booster - 30 (VSB-30). The research is characterized as a case study, conducted in the first semester of 2011, and it consisted of reviewing the literature on technological innovation and certification as well as information available in various reports, some of which were public, and interviews. The article presents a brief description of the development of the VSB-30, its importance to the market and the relevant aspects of the certification and the Certification Body of Brazil. The conclusion is that the certification is a contribution to technological innovation for it provides benefits in process improvement, especially regarding the question of documentation, creating conditions for the industry to adapt to formal established and qualified processes and, in return, to become restricted to trade companies unable to adjust to these requirements.