Cette thèse étudie la problématique d'un atterrissage sur un astéroïde. Le lander est un paquet scientifique dépourvu de plateforme de navigation. Il est placé dans une région dont la dynamique est favorable à l'atterrissage. Une étude de l'interaction entre le lander et la surface permet de comprendre quels critères physiques du lander affectent son atterrissage. / This dissertation investigates landings on an asteroid. The lander is a scientific package devoid of any navigation platform. It is released in a region dynamically favorable to landing. The study of the interaction between the lander and the surface shows the possible trade-offs on the lander physical properties that may affect its landing.

<p> The last decade has seen a proliferation of spaceflight ventures, sparking a new commercial Space Race. Companies ranging in size from SpaceX, Blue Origin, and Virgin Galactic to startups with just a few employees have submitted designs for a Lunar Lander. As the world shifts its attention back to the Moon, reducing mass and increasing safety in these systems has become vital. One avenue to weight reduction may be the legs of the lander. This experiment measures the heating of lunar lander legs from interaction with the lander’s rocket exhaust plume. The temperature of the legs was measured using thermocouples and thermochromic paint. Thirty-two thermocouples were attached in a grid pattern to generate a temperature map of the leg. Removable thermochromic paint shields provide an immediate temperature indicator so that leg distance and angle can be quickly adjusted without having to view the thermocouple temperature data. Heat transfer is also measured on the shield, finding radiation and convection. Ground tests show that the test methods, instruments, and hardware are reliable. Ground tests also show that the most significant heating and convection in ground-leg interactions occur on the bottom foot of the lander, with little heating on the top half of the leg. Further study of this heating will be vital for the future of lunar research </p>

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Orientador: Douglas Soares Galvão / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-10T18:28:40Z (GMT). No. of bitstreams: 1 Sato_Fernando_D.pdf: 7711328 bytes, checksum: 22c01d9be26cdd21cf062f6b8f62cde0 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho utilizamos métodos de física computacional para descrever o comportamento estrutural de formação de cadeias atômicas lineares suspensas (LACs) (i ) e de uma estrutura orgânica sobre superfície metálica (ii ). Ambos os temas foram desenvolvidos sobre o ponto de vista de física computacional e comparados com resultados experimentais específicos provenientes da estreita colaboração em grupos experimentais. Desenvolvemos uma metodologia para estudo sistemático da formação de nanofios (i ) metálicos a partir de aglomerados (clusters) compostos por átomos puros (Au, Ag, Cu) e a partir de ligas bi-metálicas (Au-Ag). A metodologia se baseou nas equações de movimento de Newton (método de dinâmica molecular clássica) utilizando um potencial parametrizado de origem quântica, denominado potencial de ligações fortes com aproximação de segundos momentos (TB-SMA). Com a metodologia desenvolvida foi possível realizar um estudo estatístico da formação de cadeias atômicas lineares suspensas, a verificação de aglomerados até então somente vistos em estudos direcionados a clusters, a observação de defeitos de empilhamento e a previsão de novas estruturas. Estudamos aspectos da geometria de uma molécula orgânica denominada Violeta Lander (ii ) (VL) com métodos clássicos e semi-empíricos no vácuo. A VL é uma das moléculas da classe das moléculas de Lander. Após a descrição geométrica, colocamos a VL sobre uma superfície de Cu[110] para verificar posições e conformações de estabilidade através de métodos clássicos de mecânica molecular. Para entender o comportamento dinâmico da VL sobre uma superfície de Cu[110] utilizamos um método clássico de dinâmica molecular utilizando o potencial Universal Force Field (UFF). A relevância desta parte do trabalho reside no fato de investigarmos, pela primeira vez, um caso análogo ao efeito chave-fechadura não biológico estudado no ambiente experimental e teórico de simulação. Ambos os trabalhos nos remetem para o campo da nanociência, servindo de base para futuras aplicações em nanotecnologia, tais como contatos elétricos e interação de sistemas orgânicos sobre superfície metálica / Abstract: In this work we use tools of computational physics to describe the structural and formation behavior of metallic nanowires (i ) and an organic structure on metallic surface (ii ). Both subjects had been developed under computational physics point of view and compared to specific experimental data from our close collaborations with experimental and theoretical groups. In this part of the work we developed a methodology for systematic study of the formation of metallic nanowires (i ) from clusters composed by pure atoms (Au, Ag and Cu) and from bi-metallic alloys (Au-Ag). The methodology was based on the Newton equations of motion (traditional method of molecular dynamics) together with a parametrized potential of quantum origin, named Tight-binding potential with second moment approximations (TB-SMA). With the developed methodology it was possible to carry out a statistical study of suspended linear atomic chains formation from clusters and to predict new structures and defects, stacking faults, among others. We also studied aspects of the geometry of an organic molecule called Violet Lander (VL) (ii ) with classic and semi-empirical methods in vacuum and also deposited over copper [110]. The VL is one of molecules of the Lander molecules class. The great relevance of this part of the work is because we addressed and explained the rst non-biological lock-key eect in the experimental and theoretical environment. Both the works have a great nanoscience appeal, being one of its bases. It will have great importance in future applications of nanotechnology as electric contacts and organic-metallic interaction based devices / Doutorado / Física da Matéria Condensada / Doutor em Ciências

The ISAS/JAXA Solar Power Sail mission, bound to explore the Jupiter trojans, will face many challenges during its journey. The landing manoeuvre is one of the most critical parts of any space mission that plans to investigate the surface of celestial bodies. Asteroids are mostly unknown bodies and in order to plan a successful landing on their surface, a great number of landing scenarios need to be taken into account. For the future mission to the Jupiter trojans, a study of the landing dynamics and their effects on the lander has to be done. A simple model of a lander has been created based on a design for the ISAS/JAXA Solar Power Sail mission, and the possible landing scenarios have been simulated. For this case, only the last part of the landing, which will be a free-fall has been taken into account. The lander is modelled as a rigid structure with a landing gear composed of four legs. The surface has been modelled as a flat plane with different inclinations and the possibility of including small obstacles or terrain roughness has been implemented. In the model, the lander is allowed 6 degrees of freedom. Several landing possibilities are tested with residual velocities and deviations in the starting point, and the stability of the lander is evaluated respect its geometry. Damping strategies have been considered to protect the instruments and reduce the impact, allowing for a safer landing. The effect of including crushable honeycomb dampers in the legs is also implemented, simulated and evaluated, by using a model of crushable honeycombs with different characteristics. In addition, the model includes also the position, direction and characteristics of the thrusters. Thus, it could be used to study other phases of the landing sequence where active control of the lander is needed, and evaluate the behaviour and response of different control-loop algorithms for attitude and position control of the lander.

Observing seafloor crustal deformation is often composed of acoustic ranging and GPS positioning techniques, which involves positioning of a single seabed transponder. Generally, the positional uncertainty of the seabed transponder is evaluated in terms of the slant range residuals. In order to further verify the relative positioning accuracy between seabed transponders, this study designed and fabricated a transponder lander. Three transponders were mounted on the lander to form a triangle with sides 1.505, 1.505 and 1.160 m. In addition, a data acquisition and logging system is developed to collect the lander¡¦s attitude, including pitch, roll, heading, and accelerations in three orthogonal axes. A field experiment to verify the relative positioning accuracy between seabed transponders was carried out off the coast of Kaohsiung Harbor, Taiwan. The transponder lander was deployed on the seabed at a water depth of about 300 m. Based on the attitude data collected by the logging system, the heading, pitch and roll of the transponder lander on the seabed are 123.5 degrees, 0.63 degrees and 0.62 degrees, respectively. A vessel was sailed along predetermined paths to collect observations of GPS and acoustic slant range. Then, an optimization technique combined with ray tracing method was used to estimate the positions of three transponders. The position estimates of the three transponders form a triangle with sides 1.533, 1.518 and 1.184 m, which shows that, comparing with the true values, the relative positioning error between transponders is less than 3 cm. Furthermore, based on the estimates of the transponder positions, the heading, pitch and roll of the transponder lander are calculated as 120.45 degrees, 6.43 degrees and 2.51 degrees, respectively, which are in good agreement with that measured by the attitude logging system. The experimental and evaluation results indicate that the optimization technique along with the ray tracing method is practical for precisely estimating the transponder position.

This thesis explores the significance of the journey to Poland in contemporary German literature by women. The texts are Bronjas Erbe (2001) by Beate Rygiert, Himmelskörper (2003) by Tanja Dückers, Pawels Briefe (1999) by Monika Maron, Die Töchter (1976) by Jeannette Lander, and Kindheitsmuster (1976) by Christa Wolf. I argue that Poland, as the site of the Holocaust and of the expulsions, serves as a site of memory in these texts, and that the journey to Poland allows the Jewish and non-Jewish protagonists to come to terms with the past. During their journey, most of the protagonists find what they were looking for. Further, through direct contact with Poles and Polish culture, most of the protagonists are able to overcome prejudice and stereotypical thinking. Since both the authors and their protagonists belong to different generations, i.e., those who experienced WWII directly and their children and grandchildren, the ways in which family history is passed on from one generation to the next and how it is re-collected within the German Polish context is the major concern of these texts. The immediate contact with the Polish sites triggers a process of remembering in the first-generation protagonists who are then able to pass it on to their children to fill the gaps in the family’s collective memory. The members of the younger generations become actively involved in helping to restore this memory. While conflicts between the generations escalate in Poland, the process of working through these conflicts on Polish ground helps the family members to better understand each other. I read the texts through anthropologist Victor Turner’s three-phase model of separation, liminality, and reaggregation. Poland in the five texts can thus be interpreted as a liminal space or, to use Mary Louise Pratt’s term, a contact zone. Since the texts focus on the experience of the female protagonist and traveler, the role of women as keepers of family memory is also stressed. Because of their intense probing of ethnic stereotypes and the legacy of the past, the five texts can be seen as contributing significantly to fostering a better understanding between Germans and Poles and non-Jewish and Jewish Poles. / Thesis (Ph.D, German) -- Queen's University, 2009-04-21 19:51:55.603

Cette thèse étudie la problématique d'un atterrissage sur un astéroïde. Le lander est un paquet scientifique dépourvu de plateforme de navigation. Il est placé dans une région dont la dynamique est favorable à l'atterrissage. Une étude de l'interaction entre le lander et la surface permet de comprendre quels critères physiques du lander affectent son atterrissage.

oTUS is a Long Term Underwater Sensing, bottom landing, node for observations of ocean water temperatures. LoTUS measures temperature (moored to the seafloor) according to a spec-ified time schedule until, at the end of the mission, it surfaces to transmit the collected data to on shore recipients using an Iridium link. The paper presents an extension of the sensing capability to include water current velocity (speed and direction) using a robust, reliable and inexpensive Eulerian method. The method is based on the "tilting stick" principle where a combination of inertia measurement data and magnetic sensor data is used. The paper discusses the principal technique, the modeling of the system, practical considerations, and optimization of the setup for specific flow conditions along with verifying experimental data.

One of the biggest challenges of putting a robot on an extraterrestrial surface is the entry, descent and landing. By making the robot impact resistant, the need for landing thrusters and parachutes is reduced, lowering the weight and cost of an interplanetary robotic mission. The Dynamic Tensegrity Research Lab at the NASA Ames Research Center in Mountain View, California, is currently doing research in tensegrity robots, consisting of bars and cables creating a complex dynamic system. With motors on the cables, the system can shift its center of mass to create a ”rolling” locomotion and explore remote and dangerous areas. For octahedron tensegrities with 12 bars, intuitive locomotion patterns have been explored previously. The findings included difficulties in keeping the momentum, resulting in the robot getting stuck. In this thesis, over 7.000 configurations of a central pattern generator were tested. The parameters were generated with the Monte Carlo method, with the aim to allow the robot of keeping its momentum in the motion. The resulting locomotion behavior was simulated in NASA Tensegrity Robotic Toolkit. With the method described above, a central pattern generator for a 0.5 m in diameter 12 bar tensegrity of octahedron shape was found, capable of moving 10 m during the course of a 60 s simulation. This is about four times faster than traditional rovers such as NASA’s Curiosity, indicating the need of smaller, faster robots in addition to traditional types. This, together with the impact resistance resulting in a capability of moving in difficult terrain, makes this type of robot an integral part in any future space exploration mission.