Resumo em Inglês:

Abstract: In this paper, two classic direct methods for numerical computation of optimal trajectories were revisited: the steepest descent method and the direct one based upon the second variation theory. The steepest descent method was developed for a Mayer problem of optimal control, with free final state and fixed terminal times. Terminal constraints on the state variables were considered through the penalty function method. The second method was based upon the theory of second variation and it involves the closed-loop solutions of a linear quadratic optimal control problem. The algorithm was developed for a Bolza problem of optimal control, with fixed terminal times and constrained initial and final states. Problems with free final time are also considered by using a transformation approach. An algorithm that combines the main characteristics of these methods was also presented. The methods were applied for solving two classic optimization problems - Brachistochrone and Zermelo - and their main advantages and disadvantages were discussed. Finally, the optimal space trajectories transference between coplanar circular orbits for different times of flight was calculated, using the proposed algorithm.

Resumo em Inglês:

Abstract: A multistage adaptive fast multipole method is used to accelerate the matrix-vector products arising from the Burton-Miller boundary integral equations, which are formed in a boundary element method. The present study considers the scattering of acoustic waves, generated by localized sources from bodies with rigid surfaces. Details on the implementation of a multistage adaptive fast multipole method are described for two and three-dimensional formulations. The code is verified through the solution of well documented test cases. The fast multipole method is tested for acoustic scattering problems of single and multiple bodies, and a discussion is provided on the performance of the method. Results for engineering problems with complex geometries, such as a multi-element wing, are presented in order to assess the implemented capability.

Resumo em Inglês:

Abstract: The aim of this paper was to present a calibration procedure applied to an inertial measurement unit composed of a triad of accelerometers and four gyros in a tetrad configuration. The procedure has taken into account a technique based on least-square methods and wavelet denoising to perform the best estimate of the sensor axis misalignments. The wavelet analysis takes place in order to remove undesirable high frequency components via multi-resolution signal decomposition analysis applied gyro signals. Equations for the least-square methods and wavelets analysis are presented, and the procedure is experimentally verified.

Resumo em Inglês:

Abstract: The sustained increase of the air transportation sector over the last decades has led to traffic saturated situations, inducing higher costs for airlines and important negative impacts for airport surrounding communities. The efficient management of air traffic supposes that aircraft trajectories are fully mastered and their impacts can be accurately forecasted. Inversion of aircraft flight dynamics, which are essentially nonlinear, appears necessary. Aircraft flight dynamics is shown to be differentially flat, which is a property that I has enabled the development of new numerical tools for the management of complex nonlinear dvnamic systems. I However, since in the case of aircraft flight dynamics this differential flatness property is implicit, a neural I network is introduced to deal with its numerical inversion. Results related to the developed neural network I training are displaved, while potential uses of the proposed tool are discussed.

Resumo em Inglês:

Abstract: This work has presented the first stage performance at design and off-design operating points of an axial turbine, with two stages using a numerical simulation. Experimental methods of predicting the performance of axial turbine is costly and time consuming compared to the computationalfluid dynamics approach. Therefore, computational techniques were adopted to determine the stage performance. This stuãy analyzed the first stage performance of an axial flow turbine, using a computational tool for simulating the steady state two/three-dimensional viscous flow. A computational fluid dynamics software was used to solve the rans equations with the spalart-allmaras turbulence model. The computational fluid dynamics results were compared with those obtained from the mean line loss model code. The comparisons have been conducted to provide a pretest performance for the turbine first stage.

Resumo em Inglês:

Abstract: In this paper, we have used the differential evolution to optimize the design of a Micro Air Launch Vehicle and its launch trajectory. Since trajectory design of a launch vehicle requires prior knowledge of the masses and propulsion performance parameters of the Micro Air Launch Vehicle, whereas the vehicle design requires prior knowledge of the required velocity (ΔV) to insert the required payload into the target orbit, a two-step optimization cycle was adopted. A Micro Air Launch Vehicle was designed to launch a 20-kg payload into a 400-km circular polar orbit. The preliminary design of the Micro Air Launch Vehicle was conducted given the required ΔV, which was obtained from trajectory optimization, and then applied in mission analysis to obtain the initial masses. These initial masses were used in the vehicle design to get the performance and geometry parameters. The objective function of the Micro Air Launch Vehicle design optimization is to minimize the initial mass under specified constraints on the insertion orbit. The objective of trajectory optimization is to maximize the payload mass under constraints on orbit specifications and design variables. For the 20-kg payload mass, the optimal initial mass is 1267.8 kg and optimal payload is 20.6 kg, which slightly exceeds the mission requirements.

Resumo em Inglês:

Abstract: Rockets are powered by composite solid propellant, which is a heterogeneous system consisting of solid oxidizer and metallic fuel dispersed in a polymeric fuel binder matrix. The slurry casting technique under vacuum/gravity condition is well-established for performing a different class of large sized case bonded rocket motors. During propellant casting, the flow rate of slurry is a very critical parameter as it affects the product quality. The casting rate is governed by sufficient degassing and viscosity buildup due to the progress of cure reaction. In the present study, casting rate and casting time have been numerically evaluated for fixed and varying percentages of valve opening, different viscosity of slurry, and different pressure drop (driving force). The velocity profile of propellant slurry inside feeding pipe and valve has also been evaluated. Furthermore, to get a flawless grain and to predict the slurry casting rate, a microscopic analysis has been carried out to model the flow behaviour of composite propellant slurry, where the momentum conservation law has been applied to express the mathematical model in an analytical form. The resulting differential and algebraic equations have been solved numerically using MATLAB, computing software. The numerical analysis is useful for designing new casting set-up and for giving the idea of maximum casting rate, which is achievable for given casting set-up and rheological properties of propellant slurry.

Resumo em Inglês:

Abstract: This paper has described a method to accomplish the Ground-Based Augmentation System signal-in-space integrity risk monitoring for a ground station specified by ICAO, Annex 10, Vol. 1 and RTCA DO-245A, which is a mandatory requirement to meet the certification aspects for a Ground-Based Augmentation System station. The proposed methodology was based on the Risk Tree Analysis technique, which is an optional way to design and develop an engineering solution named as integrity risk monitor that assures the integrity risk requirement for standard system architecture. The achieved results concern the qualitative and quantitative aspects of solution, which are met through the system architecture and the system safety assessment process, in special by risk assessment concepts. Finally, the integrity risk monitor is an optional architectural solution (a practical way) that has demonstrated a satisfactory result to meet the certification basis of the Brazilian Aeronautical Authorities.

Resumo em Inglês:

Abstract: This paper has discussed the guidelines included in the documents of the International Commission on Radiological Protection (ICRP) on radiation protection applicable to aircraft and crew, and this is a brief report of the evolution of studies in this field of activity, as well as the regulations and recommendations already adopted by member countries of the European Union, Canada, and the United States of America. Some peculiarities of the Brazilian airspace and legislation applicable to the work with ionizing radiation are also presented, discussing the general aspects of radiological protection applicable to aircraft crew in Brazil.

Resumo em Inglês:

Abstract: A statistical analysis of precipitation at Rio Grande do Sul State was presented in this article. The aim of this work was to identify spatial and temporal patterns of maximum precipitation, which was achieved by fitting a theoretical variogram in maximum annual rainfalls and its times of occurrence. In the literature, it was found that this pattern occurs according to phenomena typical from middle latitude, such as low and high level jet, and interactions between them. Some years ago, the relationship between maximum annual rainfalls and synoptic predominant configurations was found. Therefore, this work sought on understanding the climatic characteristics that are important in Aerospace and Aeronautics, as extreme weather can cause numerous consequences in these activities. The use and validation of this proposed method would make possible its application in other regions of interest in the Brazilian Aerospace. Understanding these climatological features of the atmospheric circulation dynamics, and analyzing maximum annual rainfall would allow a more efficient and appropriate climate trend forecast and its application in aerospace activities.

Resumo em Inglês:

Abstract: The Brazilian Microgravity Program is mainly based on experiments carried out on sounding rockets. Up to present days, three missions carrying a total of 25 experiments were made. In all flights, a fast solidification furnace, capable of producing temperatures up to 900º C, was used to process metal and semiconductor alloys in microgravity environment. This paper has described the furnace and the solidification experiment made during the last parabolic flight, called Maracati Mission, which has occurred in December, 2010.