EXAMENSARBETE. Dark Ages Lunar Interferometer. Deployment Rover - Suspension System and Transition Mecanism. Björn Bernfort och Haris Pasalic - PDF

Maskiningenjörsprogrammet 180 Hp EXAMENSARBETE Dark Ages Lunar Interferometer Deployment Rover - Suspension System and Transition Mecanism Björn Bernfort och Haris Pasalic Examensarbete 15 Hp Halmstad

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Maskiningenjörsprogrammet 180 Hp EXAMENSARBETE Dark Ages Lunar Interferometer Deployment Rover - Suspension System and Transition Mecanism Björn Bernfort och Haris Pasalic Examensarbete 15 Hp Halmstad Preface This is a degree thesis done by two mechanical engineer students on Halmstad University during the spring of It is an education that lasts 3 years. The degree theses are often in collaboration with a company. The company of this thesis is Nasa. The project in this thesis is a part in the development of a rover whit purpose to operate on the far side of the moon, deploying an instrument for science research. Abstract This thesis is a continuation of last year's work and it builds on earlier construction of a rover that will deploy an interferometer on the far side of the moon. The project is done in collaboration with (JPL) Jet Propulsion Laboratory in Pasadena, California. Given the size of the mission, accuracy and time limit project has been split into several smaller projects. The areas that are the focus of this project are the suspension and the transition system. The transition system that is originated from the stage when the rover transforms from the transit mode to ready mode, and the suspension system, are in this thesis work presented by detailed conceptual design. The next step, not mentioned this thesis work, will be to perform a primary structure design on the details. The project owner s ultimate goal is to create a better understanding about the origins of the universe and its continual changing. This would give scientists an opportunity to study some of the most fundamental questions that are still are waiting for answers. Together with a group of energy engineers, Gustav Andersson and Emil Ericsson, we were caught by the very attractive project assignment, well aware that not many people get the chance or the opportunity to be involved or work with projects like this. Sammanfattning Detta examensarbete är en fortsättning av förra årets arbete som bygger vidare på att konstruera en månrover som ska placera ut ett radioteleskop på månens baksida. Projektet görs i samarbete med (JPL) Jet Propulsion Labaratory i Pasadena, Kalifornien. Med tanke på uppdragets storlek, noggrannhet samt tidsbegränsning har man valt att delat upp projektet i flera mindre projekt. Det som vi kommer att koncentrera oss på i detta arbete är en detaljerad principkonstruktion på hjulupphängningen samt lösning på kör- och transport läge för en månrover. Nästa steg blir att utföra en primärkonstruktion på dessa detaljer. Projektets slutliga mål är att få bättre förståelse om universums ursprung och dess kontinuerliga förnedring. Detta skulle ge forskarna en möjlighet att studera några av de mest grundläggande frågor som fortfarande väntar på svar. Vi har tillsammans med en grupp energiingenjörer, Gustav Andersson och Emil Ericsson, tagit del av detta mycket intressanta och speciella projekt som inte många personer i världen har chans eller möjlighet att jobba med. Vi ska i slutet av läsperioden presentera en prototyp som kommer att byggas tillsammans, där vi visar våra moduler och även dess funktion i verkligheten. Contents 1 Introduction Background Company presentation Goal and objective Problem formulation Limitations Method Method discussion Methodology Theoretical frame of reference Lunar landscape Lunar surface material Radiation Moons potential Previous mobility system designs Sojourner The Rocky 7 rover The LEMUR robots (I, II a, II b) ATHLETE Results Criteria Explanation of the criteria Comparative weight table First evaluation: Suspension principle Concept definition and basic evaluation Table over fulfilled requirements Concept selection table Summary of evaluation Second evaluation: Transition mechanism Concept definition and basic evaluation Table over fulfilled requirements... 28 4.4.3 Concept selection table Summary of evaluation Discussion Conclusions Final solution Future work Critical Review Community, environment and economy References Appendix 1- Concepts of Suspension Appendix 2-Concepts of transition mechanism Appendix 3 Technical data of rover... 43 Introduction 1 Introduction NASA s future mission uses assets from both NASA s human and robotic programs to join together both exploration and science work in order to address fundamental questions about the universe. The mission involves an autonomous rover that will be capable of deploying a concept of a radio telescope on the far side of the Moon surface. The radio telescope is known as the most scientifically valuable and technically viable instrument of all instruments proposed for early deployment on the Moon. The lunar telescope is constructed out of a large low frequency lunar array. The lunar array will be created by a large number of antenna stations, constructed out of polyimide film antennas in where dipoles will be the fundamental collecting element. Each antenna station will have a defined number of extended polyimide antenna arms, at the moment a number of 6 arms have been proposed to be appropriate for the task. The polyamide films are found to be flexible enough to be stored in a roll during transportation. The rovers missions is to fetch polyimide films, each 1 m wide and 100 m in length from a Lunar Lander 100 1km from the deployment site. 1.1 Background NASA mission called the Dark Ages Lunar Interferometer is about placing a measuring instrument on the Moon s far side with the help of an unmanned rover. The measuring instrument is a form of telescope, specially developed for collecting information from the deep universe. Using the instrument will allow better understanding of different phenomena, such as birth of stars, the dark matter and possibly even the universe s expansion. The far side of the Moon is assumed to be the only place in our solar system that is not affected by interferences from the earth, and the solar radio emissions during the night. The deployment site is depended on a number of factors and parameters such as temperature, surface irregularity and extension of the efficient surface area. These parameters have shortened the list of deployment sites to only three suitable places, all three falling in the category of craters and called Mare Moscoviense, Aiteken and the Tsiolkovsky crater Company presentation This project is carried out in collaboration with NASA and Jet Propulsion Laboratory (JPL), a world-leading manufacturer of space-related products. The headquarters is based in California, USA. NASA s latest exploration task was a mission to Mars during The mission was executed with help of a Mars rover named Curiosity. 1 Introduction 1.2 Goal and objective The goal of the thesis is to develop some parts of a robot, a rover that is planned to be used for the far side lunar mission. The rover should be capable of moving around on the lunar surface and overcome the obstacles that may arise from the surface irregularities and the assignment itself. A basic idea for the suspension system has earlier been established by other projects; however the idea was not evaluated and studied further in depth. The objective of this thesis work will be to establish a solution for the suspension system and also to find and establish a solution for the transition stage. A transition stage is originated from the rover transit mode to the action mode. It is a primary stage, necessary for the rover to perform due to the lack of space in the rocket that will ship the rover to the moon Problem formulation For the necessary task, derived from rolling out the rolls of polyamide antennas on lunar surface, a rover has to be designed that will be able to operate and get around smoothly. Difficulties in the task may arise from the obstructions of the lunar environment, from cosmic radiation, large temperature fluctuations and the lack of atmosphere which already at this stage excludes any cooling of systems by airflow. Another problem may occur when placing the antenna roll, while the weight varies in the antenna roll, it can affect negative on the stability system of the rover if the system is not properly designed. 1.3 Limitations This work will to some extend be executed in a collaboration with thesis working students from energy engineering. The complete work has been divided into two projects where students from energy engineering will focus on the development of the motors, solar panels, batteries and the general power supply. The areas that will be the focus of this thesis work are the suspension system, including connection to the chassis and the transition system from the standby mode during transportation and the ready mode when ready for action. Furthermore, balancing of the chassis while the rover is operating will also be a part of this thesis work. The depth of the work will be set to the detail level. Due to the lack of time, other areas such as the steering and the steering system, motor and gearing, framework/chassis and wheels will not be within the scope of this thesis work. 2 Method 2 Method In this case, constructing a new part of the suspension, the decision was made to work within the embodiment design of construction by (Freddy Olsson, 1995) as a method which we are familiar and use to working with. The reason that working with conceptual design is remaining even this year is that fundamental parts in the embodiment design of the suspension that we find in last year s results seems to be missing (Dark Ages Lunar Interferometer (DALI): Deployment-Rover, (Mobility System, Chassis, Deployment mechanism), (E. Andersson; P-J. Bengtsson; T. Johannesson,; K. Hansson,; T. Stanimirovic,; J. Winberg,, 2013). When this project which includes designing of suspension at principle level is finished, the remaining work is suitable for further studies in detail design. 2.1 Method discussion Different methods that exist in embodiment design are compared to each other (Freddy Olsson, 1995), Total Design (Stuart Pugh, 1991) and Product Design and Development (Karl Urlich, Steven D. Eppinger, 2011) and a quite similar methodology is described and presented in these books. (Freddy Olsson, 1995) have more concrete examples of different stages in design that have to be made for a successful construction. Due to that and also from earlier experience with similar projects according to this philosophy, we choose to simply follow these methods basic and relevant parts. 2.2 Methodology Embodiment design that stands for a development and assumes appropriate solution to the problem, find its way through different methods to a principle solution to the problem. Embodiment design stands for a development which assumes an appropriate solution to the problem, finds its way through different methods to a principle solution to its ultimate goal. The embodiment design is performed in few steps: Product definition. The product definition covers multiple areas. These are; field of application, main assignment, environment, human impacts and possibly, the economic conditions. The product definition will not be described in this thesis work due to the reason that it already has been described in previous works which in this work only would be recognized as a repetitive content. Product research and criterion 3 Method Product research has been made to some extend on earlier thesis works that were related to the rover, but it has also been made on the research level through scientific journals about earlier rovers. Some criteria that were found to be relevant from last year s thesis work will together with a number of new suitable requirements and desires be incorporated and evaluated in this work. Development of product proposals For generating product proposals, brainstorming will mainly be used as the method for obtaining different proposals. When brainstorming is used in an early stage of a project, it is important to be open minded and to accept all suggestions. One should have the assumption that there are no bad ideas and the mentioned proposals should not be criticized. The reason for this is that many an idea may seem to be too complicated, or not relevant in the beginning, but when further evaluated it may prove that the idea was a good one after all. In this stage of the project, the quantity of ideas was considered to be important as quantity often generates later on to a qualitative proposal. The ideas were subsequently further developed, finalized and described in more detail. Evaluation of product proposals In this stage the product proposals are evaluated against the established criteria. The different product proposals advantages, disadvantages, strengths, weaknesses and deficiencies against the lined-up requirements will in this stage be shown. The evaluation process can be made on some different levels and applied by various methods. With the help of evaluations that will be made, the most appropriate proposal will subsequently be used for further work. Presentation of a selected product The selected product proposal is often presented in freehanded drawings or as physical models. Since proposal is in its basic element some additions may occur if that seems to be needed for products further development. Finally should product proposals meet all requirements and match previously established preferences. In the presentation of selected product pros and cons are presented and even technical and economic aspects are noted. 4 Theoretical frame of reference 3 Theoretical frame of reference Theoretical research on the present and past studies is a necessary stage to perform in order to gain a better understanding of the project framework and the areas involved. A good understanding of the different areas and parameters will consequently be of great help when the stage of generating ideas comes to question. Therefore, the following subchapters are presenting studies of the lunar environment, characteristics of the lunar surface and some noteworthy parts of the rover for this work. 3.1 Lunar landscape The terrain of the moon can be divided into highlands and lowlands. The difference in altitude lies between approximately m in the highland and around m in the depths, which is quite similar to the one on earth. But the geology is anyway very different. The moon does not have an atmosphere. That makes it exposed to meteor impacts, but it also eliminates erosion due to water. A long time ago the moon was volcanic active, and it is volcanism and meteor impacts that have formed the lunar landscape. This makes the lunar surface mainly very rough, but there are also some smoother areas. There are some darker areas of the moon which represent lowlands. These are called lunar maria (latin for seas). There are however no seas, and have ever been, on the moon, but the early astronomers thought that, and therefore it is still called lunar maria or seas. Most of the lunar marias is located on the close side of the moon. Less than one percent of the far side of the moon is covered by lunar maria. The lunar marias consist of a relatively flat area compared to the surrounding areas, because these areas are much younger. (figure 3.1-1) These areas are made from volcanic activity, and the dark areas consist of solidified lava. Figure flat mare (dark area) in Tsiolkovsky crater surrounded by rough terrain (NASA, 1968) 5 Theoretical frame of reference 3.2 Lunar surface material The material which covers the moon s surface is called regolith. It consists of broken rock, soil, dust particles and other related materials. Regolith can also be found on earth, mars and other terrestrial planets, but each one has its own specific properties. The regolith on the moon consists of a composition of oxygen, silicon, iron, calcium, aluminum, magnesium and other materials in smaller concentrations. The regolith represents/makes up a quite compact soil with a fine and powdery texture. It is able to support a wide variety of roving vehicles according to Lunar sourcebook: A users guide to the moon (Grant H. Heiken, David T. Vaniman och Bevan M. French(eds.), 1991), It has a density of about 1.5 g/cm 3. Figure 3.2-1: Footprint in regolith taken on the Apollo 11 Mission (NASA, 1969) 3.3 Radiation The moon has no protection from radiation like earth has. The strong magnetic field and the thick atmosphere protect earth from a wide range of the radiation from space. There are mainly three types of radiation on the moon: solar cosmic rays, solar wind and galactic cosmic rays. These radiations consist of protons and electrons with extremely high energy. The penetration can vary from micrometers to meters depending on their energy and composition (Heiken et al., 1991, p.47). 3.4 Moons potential National Aeronautics and Space Administration (NASA) plans to return humans to the Moon. It may be the place where astronauts are preparing for upcoming journeys to Mars but it is also an established place for the scientific investigations that will be made on the deep universe. The moon is potentially the only site in the inner solar system for special scientific investigations like the ones that will 6 Theoretical frame of reference emerge with the use of ROLLS instrument. There are several reasons found to be the source for this statement, noted and shortly presented in this subchapter. No human generated interference: Means that the relevant frequencies used by both civil and military communication transmitters may interfere in the range of Dark Ages frequencies as well. Those signals are much stronger than the HI signals and detectable even at remote locations above the Earth. However, lunar far side is protected by the Moon itself which consequently is reducing such interferences to a more negligible level (Alexander & Kaiser 1976). No (Permanent) Ionosphere: Ionosphere produced by the Earth is limiting radio observation that simply is reflecting interference from distant transmitters. On the Moon those errors are occurring only during the day time due to the solar irradiation that ionized plasma layer witch disappears during the night. Shielding from Solar Radio Emissions; the Sun is the strongest celestial source at the frequencies when it is bursting. The physical shielding is the only way to mitigate solar radiation effect within our solar system. Such shielding is possible by observation during lunar night at a point when the moon is physically protecting the surface. 3.5 Previous mobility system designs In order to create a better understanding of the planetary environments in our Solar system, explorations on planetary basis are necessary for the scientific research. Prior to sending a robot for scientific research on a planetary surface, background studies should be made on the robots and the devices that have been used for similar kind of missions. The experience with the previous robots ought to be analyzed and considered for the upcoming missions. However, a chance for new ideas and different solutions should be given for development purposes of the robots and for increasing the chances of success for future missions. Up to now, every scientific research on a planetary surface was executed with a multi-wheeled rover. In order to have successful missions even in rough environments such as Mars mountain cliffs or low gravitational places such as asteroids and comets, other mobility solutions should be considered. Also robots with multiple capabilities such as drilling, digging, lifting etc. should also be considered for development purposes in order to be able to extract even better information from the surfaces and environments. In the following background research, past and current designs of mobility systems developed for planetary explorations at JPL are presented. Some of robots have been used for different missions and some have been used as prototype 7 Theoretical frame of reference models for test purposes. Multi-wheeled mobility syste
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