Optimization of satellite constellations in the moon

Nowadays, we return to live a period of lunar exploration. China, Japan and India heavily invest in missions to the moon, and then try to implement manned bases on this satellite. These bases must be installed in polar regions due to the apparent existence of water. Therefore, the study of the feasibility of satellite constellations for navigation, control and communication recovers importance. The Moon's gravitational potential and resonant movements due to the proximity to Earth as the Kozai-Lidov resonance, must be considered in addition to other perturbations of lesser magnitude. The usual satellite constellations provide, as a basic feature, continuous and global coverage of the Earth. With this goal, they are designed for the smallest number of objects possible to perform a specific task and this amount is directly related to the altitude of the orbits and visual abilities of the members of the constellation. However the problem is different when the area to be covered is reduced to a given zone. The required number of space objects can be reduced. Furthermore, depending on the mission requirements it may be not necessary to provide continuous coverage. Taking into account the possibility of setting up a constellation that covers a specific region of the Moon on a non-continuous base, in this study we seek a criterion of optimization related to the time between visits. The propagation of the orbits of objects in the constellation in conjunction with the coverage constraints, provide information on the periods of time in which points of the surface are covered by a satellite, and time intervals in which they are not. So we minimize the time between visits considering several sets of possible constellations and using genetic algorithms.

ASTER: A Brazilian mission to an asteroid

The first Brazilian mission to an asteroid is being planned. The target is the asteroid 2001 SN263, which has a NEA orbit of class AMOR. Spectral analysis indicated that this is a C-type asteroid. This type of asteroids are dark and difficult to be studied from Earth. They hold clues of the initial stages of planetary formation and also the origin of water and life on Earth. In fact, radar data showed that 2001 SN263 is composed of three bodies with diameters of about 2.8 km, 1.1 km and 0.4 km. Therefore, the spacecraft will have the opportunity to explore three bodies on the same trip. The mission is scheduled to be launched in 2015, reaching the asteroid in 2018. It will be used a small spacecraft (150 kg) with 30 kg for the payload. The set of scientific instruments being considered to explore the target of this mission include an Imaging Camera, a Laser Rangefinder, an Infrared Spectrometer, a Synthetic Aperture Radar and a Mass Spectrometer. The main measurements to be made include the bulk properties (size, shape, mass, density, dynamics, spin state), the internal properties (structure, gravity field) and surface properties (mineralogy, morphology, elemental composition). The mission also opens an opportunity for some relevant experiments, not directly related to the target. Two such experiments will take benefit from being on board of the spacecraft along the journey to the asteroid system, which will take about three years. The first is an astrobiology experiment. The main goal of this experiment is to determine the viability of the microorganisms survival in extraterrestrial environments simulated in laboratory (chemical atmosphere, temperature, desiccation, vacuum, microgravity and radiation). The second experiment is a plasma package. The main objectives of this experiment are to study the structure and electrodynamics of plasma along the trajectory, the plasma instability processes and the density and temperature of plasma of solar wind origin along the trajectory and near the asteroids. This mission represents a great challenge for the Brazilian space program. It is being structured to allow the full engagement of the Brazilian universities and technological companies in all the necessary developments to be carried out. In this paper, we present some aspects of this mission and details of the payload that will be used and the scientific expectations. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

The aster mission: Exploring for the first time a triple system asteroid

2001 SN263 is a triple system asteroid. Although it was discovery in 2001, in 2008 astronomical observation carried out by Arecibo observatory revealed that it is actually a system with three bodies orbiting each other. The main central body is an irregular object with a diameter about 2.8 km, while the other two are small objects with less than 1 km across. This system presents an orbital eccentricity of 0.47, with perihelion of 1.04 and aphelion of 1.99, which means that it can be considered as a Near Earth Object. This interesting system was chosen as the target for the Aster mission - first Brazilian space exploration undertaking. A small spacecraft with 150 kg of total mass, 30 kg of payload with 110 W available for the instruments, is scheduled to be launched in 2015, and in 2018 it will approach and will be put in orbit of the triple system. This spacecraft will use electric propulsion and in its payload it will carry image camera, laser rangefinder, infrared spectrometer, mass spectrometer, and experiments to be performed in its way to the asteroid. This mission represents a great challenge for the Brazilian space program. It is being structured to allow the full engagement of the Brazilian universities and technological companies in all the necessary developments to be carried out. In this paper, we present some aspects of this mission, including the transfer trajectories to be used, and details of buss and payload subsystems that are being developed and will be used. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

Influence of nonsphericity of planetary satellites and perturbation of the third-body on the artificial satellites motion

Some orbital characteristics of lunar artificial satellites is presented taking into account the perturbation of the third-body in elliptical orbit and the non-uniform distribution of mass of the Moon. We consider the development of the non-sphericity of the Moon in zonal spherical harmonics up to the ninth order and sectorial harmonic C 22 due to the lunar equatorial ellipticity. The motion of the artificial satellite is studied under the single-averaged analytical model. The average is applied to the mean anomaly of the satellite to analyze low-altitude orbits which are of highest importance for future lunar missions. We found families of frozen orbits with long lifetimes for the problem of an orbiter travelling around the Moon.

Optimal low cost transfer to L4 and L5 lagrangian points

Lagrangian points L4 and L5 lie at 60 degrees ahead of and behind Moon in its orbit with respect to the Earth. Each one of them is a third point of an equilateral triangle with the base of the line defined by those two bodies. These Lagrangian points are stable for the Earth-Moon mass ratio. Because of their distance electromagnetic radiations from the Earth arrive on them substantially attenuated. As so, these Lagrangian points represent remarkable positions to host astronomical observatories. However, this same distance characteristic may be a challenge for periodic servicing mission. In this work, we introduce a new low-cost orbital transfer strategy that opportunistically combine chaotic and swing-by transfers to get a very efficient strategy that can be used for servicing mission on astronomical mission placed on Lagrangian points L4 or L5. This strategy is not only efficient with respect to thrust requirement, but also its time transfer is comparable to others known transfer techniques based on time optimization. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

Optimal low-cost transfer to L4 and L5 lagrangian points based on G-family of periodic orbits

An alternative transfer strategy to send spacecrafts to stable orbits around the Lagrangian equilibrium points L4 and L5 based in trajectories derived from the periodic orbits around LI is presented in this work. The trajectories derived, called Trajectories G, are described and studied in terms of the initial generation requirements and their energy variations relative to the Earth through the passage by the lunar sphere of influence. Missions for insertion of spacecrafts in elliptic orbits around L4 and L5 are analysed considering the Restricted Three-Body Problem Earth- Moon-particle and the results are discussed starting from the thrust, time of flight and energy variation relative to the Earth. Copyright© (2012) by the International Astronautical Federation.

Fatigue Behavior of Weld Repaired AISI 4130 Aeronautic Steel Used in Critical Flight Safety Structures

Since the 1950s, fatigue is the most important project and operational consideration for both civil and military aircrafts. For some aircraft models the most loaded component is one that supports the motor: the Motor Cradle. Because they are considered critical to the flight safety the aeronautic standards are extremely rigorous in manufacturing them by imposing a zero index of defects on the final weld quality (Safe Life), which is 100% inspected by Non-Destructive Testing/NDT. This study has as objective to evaluate the effects of up to four successive TIG welding repairs on the axial fatigue strength of an AISI 4130 steel. Tests were conducted on hot-rolled steel plate specimens, 0.89 mm thick, with load ratio R = 0.1, constant amplitude, at 20 Hz frequency and in room temperature, in accordance with ASTM E466 Standard. The results were related to microhardness and microstructural and geometric changes resulting from welding cycles.

Fatigue crack growth rate in mode I of a carbon fiber 5HS weave composite laminate processed via RTM

Delamination or crack propagation between plies is a critical issue for structural composites. In viewing this issue and the large application of woven fabrics in structural applications, especially the ones that requires high drapeability to be preformed in a RTM mold cavity such as the asymmetric ones, e.g HS series, this research aimed in dynamically testing the carbon fiber 5HS/RTM6 epoxy composites under opening mode using DCB set up in order to investigate the crack growth rate behavior in an irregular surface produced by the fabric waviness. The evaluation of the energy involved in each crack increment was based on the Irwin-Kies equation using compliance beam theory. The tests were conducted at constant stress ratio of R=0.1 with displacement control, frequency of 10 Hz, in accordance to ASTM E647-00 for measurement of crack growth rate. The results showed large scatter when compared to unidirectional carbon fiber composites due to damage accumulation at the fill tows.

INFLUENCE OF HVOF COATING ON THE FATIGUE STRENGTH OF 15-5 PH STAINLESS STEEL

Structural component failures due to cyclic loading are associated to surface damage of materials and its interaction with environment. Fatigue failure occurs with stresses below the yield strength of each material and is a result of crack initiation and propagation. In aeronautical components is an important parameter to be considered in project, as well as the corrosion and wear resistance. Thermally sprayed HVOF coatings have been considered to replace galvanic chromium deposits with comparable performance for wear and corrosion resistance. The aim of present research is to study the influence of WC-13Co-4Cr applied by HVOF, on the axial fatigue strength of 15-5 PH stainless steel. The shot peening treatment was used to restore fatigue performance.

Influence of shot peening on the fatigue strength of Custom 465 stainless steel for aeronautic application

This project was originated from the national aircraft industry requirements to reduce the use of coated materials with electroplated chromium or cadmium that produce waste, which is harmful to health or the environment. The selected material is a Custom 465 stainless steel used in the aeronautical field due to its high mechanical strength. Considering the load sustained by the wheel axis of the landing gear, the Custom 465 is tested in axial fatigue. The objective is to compare the behavior of the Custom 465 with plated AISI 4340 steel coated with cadmium. X-ray diffraction method was used to determine the residual stress field induced by shot peening.

Artemídia preferente: fenômeno jogar & ler nas histórias em quadrinhos interativas (HQI) com os games de RPG

This artistic-scientific process aims to innovate the concept of Interactive Comics by adding them into the concept of RPG games and Single-Adventures. To make it properly done, there will be some issues about Interactivity, history of the Comic Strip and Mangas, and their techniques of use. Also, there will be other issues involving Electronic Comics and Interactive Comics, in addition to the concept of the RPG games and Single-Adventures, so that the reader of this paper could understand the practical result of every issue combined into one. The identification of these issues is made from a bibliographic and iconographic research, and it will also be displayed throughout the content. Some decisions will be thrown along this paper for the reader to decide and, therefore, understand the Interactivity process in a better way. The combined issues’ result will be presented in my interactive website, http://a3studios.com.br/iss/home (address not final) or http://amstarproductions.net (final address), where the readers will have to experience the “Play&Read” phenomenon. Furthermore, this work is inserted in the line of the research Artistic Processes and Procedures of the Department of Fine Arts from the Art Institute of UNESP, whose methodology used was the Freinet Educational Cybernetics, developed in the research group Media Arts and Videoclip leaded by the leading advisor for this Final Course Work. The result and discussion of artistic and scientific research were reported in monographs such as this that I present, with the following versions: PDF version for dissemination in the virtual repository of the Institute of Arts’ Library; hardcover version for physical collection at the Library of Institute of Arts; The Printed Version for the board of examiners; and an appropriated template version for submission to International Scientific Congress in the area of Arts.

HQtrônica: atividade programada e curso de extensão

This Final Course Work’s main subject comes from a study made on my previous Final Course Work titled “Artemídia Preferente: Fenômeno ‘Jogar&Ler’ nas Histórias em Quadrinhos Interativas (HQI) com os games do RPG”, and it is fed by the shortage of Electronical Comic publications, classes, courses and activities that could suit for educational purposes and experiences for a capable kind of audience to learn it and do it. Specific issues about Electronic Comic will be presented, based on Célestin Freinet’s Pedagogy, on some books about Methodology and on the Brazilian Curriculum Guidelines required for graduation. After that, a Lesson Plan will be developed for a 14 year-old-or-older kind of audience where they will be capable of making their own Electronic Comic, being it educational-themed or not. This study also cares about the participants’ influences on their lives to be completed. Furthermore, this work is inserted in the line of the research “Artistic Processes and Procedures” of the Department of Fine Arts from the Art Institute of UNESP, whose methodology used was the Freinet Educational Cybernetics, developed in the research group “Media Arts and Videoclip” leaded by the leading advisor for this Final Course Work. The result and discussion of artistic and scientific research were reported in monographs such as this that I present, with the following versions: PDF version for dissemination in the virtual repository of the Institute of Art’s Library; hardcover version for physical collection at the Institute of Art’s Library; the printed version for the board of examiners, and an appropriated template version for submission to the International Scientific Congress in the area of Arts.

Artemidia independente: Vidas Imperfeitas, o quadrinho em um diálogo entre linguagem e suporte

The term “independent media art” expresses an artistic-scientific process performed in the Art- Science Communication interface presented as Final Paper in Visual Arts baccalaureate modality. The first part consists in gather, in artisticscientific research, an overview of the production of independent comics, mainly in Brazil, as well as some of the manifestations that were derived from it. The identification is made from bibliographical and iconographical survey, both printed and virtual materials. The second part discusses the production of a comic of my own - Imperfect Lives - published independently. This work is inserted in the line of research “Artistic Processes and Procedures” of the Department of Fine Arts of the Art Institute of UNESP and describes: Creative process, production, dissemination and influences. The third and final section brings together the work done by me during the four-year course, whose theme has some relation with comics. Experiments are in various media, using one or another characteristic intrinsic to them. The monography includes as an appendix a copy of each issue of the fanzine Imperfect Lives. The methodology used was Freinetiana Educational Cybernetics, developed in the research group “Art media and Videoclip”, whose leading advisor is the one from this Final Paper. The result and discussion of the artistic research and scientific monography were reported in the following versions: PDF File repository for dissemination in the virtual library of the Institute of Arts. Hardcover version for physical collection in the Library of the Institute of Arts. Paper version for the committee. Template version appropriate for submission to International Scientific Congress in the area of Arts

Artemídia escrevente: a caligrafia entre a arte e o design

The term “writing media art” expresses an artisticscientific process performed in the Art-Science Communication interface presented as Final Paper in Visual Arts baccalaureate modality. The first part gathers, in artistic-scientific research, a historical overview of the relation between image and writing, which its main focus is calligraphy and its different expressions in art and design, including their interrelations. The identification is made from bibliographical and iconographical survey, both printed and virtual materials. This approach involves the selection of authors’ statements and comments in order to offer a deeper historical basis, since it comes to facts and events. The second part relates to the set of works produced during the four-year period of the Visual Arts course, including a reflection about the creation process and all that surrounds it – influences, memories, visions etc. – to finally establish a connection between all these elements in order to make clear this incredible web of creation. This work is inserted in the line of research “Artistic Processes and Procedures” of the Department of Fine Arts of the Art Institute of UNESP and describes: creative process, production and influences. The methodology used was Freinetiana Educational Cybernetics, developed in the research group “Art media and Videoclip”, whose leading advisor is the one from this Final Paper. The result and discussion of the artistic-scientific research were reported in monography in the following versions: PDF File repository for dissemination in the virtual library of the Institute of Arts; hardcover version for physical collection in the Library of the Institute of Arts; paper version for the committee; template version appropriate for submission to International Scientific Congress in the area of Arts