Advances in Spacecraft Systems and Orbit Determination

"Advances in Spacecraft Systems and Orbit Determinations", discusses the development of new technologies and the limitations of the present technology, used for interplanetary missions. Various experts have contributed to develop the bridge between present limitations and technology growth to overcome the limitations. Key features of this book inform us about the orbit determination techniques based on a smooth research based on astrophysics. The book also provides a detailed overview on Spacecraft Systems including reliability of low-cost AOCS, sliding mode controlling and a new view on attitude controller design based on sliding mode, with thrusters. It also provides a technological roadmap for HVAC optimization. The book also gives an excellent overview of resolving the difficulties for interplanetary missions with the comparison of present technologies and new advancements. Overall, this will be very much interesting book to explore the roadmap of technological growth in spacecraft systems

NASA/Howard University Large Space Structures Institute

Basic research on the engineering behavior of large space structures is presented. Methods of structural analysis, control, and optimization of large flexible systems are examined. Topics of investigation include the Load Correction Method (LCM) modeling technique, stabilization of flexible bodies by feedback control, mathematical refinement of analysis equations, optimization of the design of structural components, deployment dynamics, and the use of microprocessors in attitude and shape control of large space structures. Information on key personnel, budgeting, support plans and conferences is included

Guidebook for analysis of tether applications

This guidebook is intended as a tool to facilitate initial analyses of proposed tether applications in space. The guiding philosophy is that a brief analysis of all the common problem areas is far more useful than a detailed study in any one area. Such analyses can minimize the waste of resources on elegant but fatally flawed concepts, and can identify the areas where more effort is needed on concepts which do survive the initial analyses. The simplified formulas, approximations, and analytical tools included should be used only for preliminary analyses. For detailed analyses, the references with each topic and in the bibliography may be useful

Deorbiting Algorithms Development for CubeSats using Propulsion and Sails

CubeSats are becoming increasingly popular within the scientific and commercial community, as they provide relatively cheap and quick access to space. However, as their launching rates increase rapidly, the concern that they may have a negative impact in the space debris problem also increases. This calls for the development of novel deorbiting technologies for CubeSats. In a response to this need, this thesis presents two new attitude controllers and deorbiting algorithms, which enable ionic thrusters, as well as drag sails, in order to accelerate CubeSat orbital disposal. These algorithms are designed with nanosatellites capabilities in mind, requiring minimum attitude determination and control. Their efficacy is demonstrated through numerical models in all cases. In the first approach, a geomagnetic field tracker controller is presented. This controller aligns the thrusting carrying axis of the satellite with the local magnetic field vector. The only sensors and actuators required are magnetometers and magnetorquers respectively. A suitable deorbiting algorithm is also presented, which is activated once the CubeSat is tracking the geomagnetic vector. This algorithm determines the portions of the orbit in which thrust must be applied, and it only requires a model of Earth's magnetic field. This approach is simulated with ionic thrusters, obtaining deorbiting rates between 0.35 km/day and 50 km/day, depending on the type of engine used. Proof of stability is provided through Floquet theory, while robustness analysis is executed through Monte Carlo simulations. This approach has advantages such as minimum sensing and actuating requirements, and it doesn't require movable parts nor deployables, minimizing the probability of failures in orbit. In the second approach, a gyroless spin-stabilization controller is proposed. This algorithm fixes the thrusting carrying axis of the CubeSat in the inertial frame. Just as the first approach, this controller only requires magnetometers and magnetorquers. Once the satellite is stabilized, an orbit sampling algorithm is introduced. This algorithm is able to determine the portions of the orbit where to apply thrust, using only Global Positioning System inputs. This approach is simulated with electrospray thrusters, achieving deorbiting rates in the order of 45 km/day. Stability analysis is provided through Lyapunov theory, while Monte Carlo simulations are used to prove the robustness of the algorithm. The attitude stabilization phases of both approaches are very flexible, in that they can work with a variety of thrusters, as well as non propulsive technologies. Dragsails are often proposed as means for deorbiting CubeSats, however, there is a gap in the literature when it comes to their stabilization in orbit. Therefore, the efficacy of these stabilization approaches when used in conjunction with drag sails is analysed. In the case of the geomagnetic field tracking algorithm, deorbiting rates in the order of 19 km/day are attained. In the case of the gyroless spin-stabilization algorithm, deorbiting times of up to 12.5 km/day are achieved. These algorithms provide convenient means for CubeSat deorbiting, contributing to space debris mitigation efforts. They require minimum hardware and software capabilities, and because of this the probability of failures is low, and they provide excellent deorbiting rates

Tethers in Space Handbook

A new edition of the Tethers in Space Handbook was needed after the last edition published in 1989. Tether-related activities have been quite busy in the 90's. We have had the flights of TSSI and TSSI-R, SEDS-1 and -2, PMG, TIPS and OEDIPUS. In less than three years there have been one international Conference on Tethers in Space, held in Washington DC, and three workshops, held at ESA/Estec in the Netherlands, at ISAS in Japan and at the University of Michigan, Ann Harbor. The community has grown and we finally have real flight data to compare our models with. The life of spaceborne tethers has not been always easy and we got our dose of setbacks, but we feel pretty optimistic for the future. We are just stepping out of the pioneering stage to start to use tethers for space science and technological applications. As we are writing this handbook TiPs, a NRL tether project is flying above our heads. There is no emphasis in affirming that as of today spacebome tethers are a reality and their potential is far from being fully appreciated. Consequently, a large amount of new information had to be incorporated into this new edition. The general structure of the handbook has been left mostly unchanged. The past editors have set a style which we have not felt needed change. The section on the flights has been enriched with information on the scientific results. The categories of the applications have not been modified, and in some cases we have mentioned the existence of related flight data. We felt that the section contributed by Joe Carroll, called Tether Data, should be maintained as it was, being a "classic" and still very accurate and not at all obsolete. We have introduced a new chapter entitled Space Science and Tethers since flight experience has shown that tethers can complement other space-based investigations. The bibliography has been updated. Due to the great production in the last few years %e had to restrict our search to works published in refereed journal. The production, however, is much more extensive. In addition, we have included the summary of the papers presented at the last International Conference which was a forum for first-hand information on all the flights

Technology for large space systems: A bibliography with indexes (supplement 10)

The bibliography lists 408 reports, articles and other documents introduced into the NASA scientific and technical information system to provide helpful information to the researcher, manager, and designer in technology development and mission design in the area of large space system technology. Subject matter is grouped according to systems, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

Tethers in space handbook, second edition

The Tethers in Space Handbook, Second Edition represents an update to the initial volume issued in September 1986. As originally intended, this handbook is designed to serve as a reference manual for policy makers, program managers, educators, engineers, and scientists alike. It contains information for the uninitiated, providing insight into the fundamental behavior of tethers in space. For those familiar with space tethers, it includes a summary of past and ongoing studies and programs, a complete bibliography of tether publications, and names, addresses, and phone numbers of workers in the field. Perhaps its most valuable asset is the brief description of nearly 50 tether applications which have been proposed and analyzed over the past 10 years. The great variety of these applications, from energy generation to boosting satellites to gravity wave detection is an indication that tethers will play a significant part in the future of space development. This edition of the handbook preserves the major characteristics of the original; however, some significant rearrangements and additions have been made. The first section on Tether Programs has been brought up to date, and now includes a description of TSS-2, the aerodynamic NASA/Italian Space Agency (ASI) mission. Tether Applications follows, and this section has been substantially rearranged. First, the index and cross-reference for the applications have been simplified. Also, the categories have changed slightly, with Technology and Test changed to Aerodynamics, and the Constellations category removed. In reality, tether constellations may be applicable to many of the other categories, since it is simply a different way of using tethers. Finally, to separate out those applications which are obviously in the future, a Concepts category has been added. A new section included here on Conference Summaries recognizes the fact that the tether community is growing internationally, and that meetings provide a means of rapid communication and interaction. Finally, the Bibliography section has been considerably updated to include all known references. These are listed by author and by subject and include the papers to be presented at the Third International Conference in May 1989

Proceedings of a Workshop on the Applications of Tethers in Space, Volume 1

Project overview; tether deployment; satellite system description; tether fundamentals; science applications; electrodynamic interactions; transportation; artificial gravity; and constellations; were described

Optimal Control of Electrodynamic Tethers

Low thrust propulsion systems such as electrodynamic tethers offer a fuel-efficient means to maneuver satellites to new orbits, however they can only perform such maneuvers when they are continuously operated for a long time. Such long-term maneuvers occur over many orbits often rendering short time scale trajectory optimization methods ineffective. An approach to multi-revolution, long time scale optimal control of an electrodynamic tether is investigated for a tethered satellite system in Low Earth Orbit with atmospheric drag. Control is assumed to be periodic over several orbits since under the assumptions of a nearly circular orbit, periodic control yields the only solution that significantly contributes to secular changes in the orbital parameters. The optimal control problem is constructed in such a way as to maneuver the satellite to a new orbit while minimizing a cost function subject to the constraints of the time-averaged equations of motion by controlling current in the tether. To accurately capture the tether orbital dynamics, libration is modeled and controlled over long time scales in a similar manner to the orbital states. Libration is addressed in two parts; equilibrium and stability analysis, and control. Libration equations of motion are derived and analyzed to provide equilibrium and stability criteria that define the constraints of the design. A new libration mean square state is introduced and constrained to maintain libration within an acceptable envelope throughout a given maneuver. A multiple time scale approach is used to capture the effects of the Earth’s rotating tilted magnetic field. Optimal control solutions are achieved using a pseudospectral method to maneuver an electrodynamic tether to new orbits over long time scales while managing librational motion using only the current in the tether wire

Study of Low Earth Orbit impact on ORCA2SAT subsystems

Mission planning of CubeSats can be very challenging due to their mass, volume and power constraints. In addition, the majority of CubeSat projects are done at a University level, which can also mean constraints in terms of budget. In order to guarantee the mission’s success, several aspects must be studied prior to launch. Firstly, it must be assured that the satellite has enough accesses to the desired ground stations in order to establish communications while in orbit. However, to keep the satellite operational power generation is required. The profile of power generation varies throughout the year and is heavily dependent on the CubeSat’s orbit. Thus, it is crucial to assess the power generation for a long period in order to guarantee the operation of the satellite and help set limits for systems design and hardware selection. The constraints mentioned above make use of magnetorquers as the main attitude actuators, which require a study of the Earth’s magnetic field in order to compare the generated torques with the perturbative torques inherent to the space environment. Another concern are temperature limits of the components, therefore, the temperatures experienced by the satellite in orbit must be computed and decisions must be taken to allow for the mission’s success. As in the previous analysis, the dynamic behavior of the CubeSat under launch conditions can also draw the line between success and failure. This work describes the steps taken in order to simulate all the aforementioned aspects for the computed mission lifetime, in order to mitigate inherent risks and guarantee mission success for ORCA2Sat, a two unit Cube- Sat. The simulations were done through pertinent finite elements models and space environment computational models, for a deployment from the International Space Station. It was proved, with this comprehensive mission analysis, that for the studied critical factors ORCA2Sat’s mission can be accomplished for the desired period of time, keeping the satellite operational throughout its life in orbit.O planeamento de missões de CubeSats pode ser bastante desafiante devido às suas restrições de massa, volume e energia. Além disso, a maioria dos projetos de CubeSats são a nível universitário, o que pode também significar restrições de orçamento. De modo a garantir o sucesso da missão, vários aspetos devem ser estudados antes do lançamento. Primeiramente, deve-se certificar que o satélite tem tempos de acesso suficientes às estações em solo desejadas de modo a estabelecer comunicações enquanto em órbita. Contudo, para manter o satélite operacional, é necessário gerar energia. O perfil da produção de energia varia ao longo do ano e é profundamente dependente da órbita do CubeSat. Portanto, é crucial avaliar a produção de energia durante um longo período de modo a garantir a operação do satélite e ajudar a definir limites no design de sistemas e seleção de componentes. As restrições mencionadas acima fazem com que sejam usados magnetorquers como principais atuadores de atitude, os quais requerem um estudo do campo magnético da Terra de modo a comparar os torques gerados com os torques perturbativos inerentes do ambiente espacial. Outro cuidado a ter são os limites de temperatura dos componentes, assim, é necessário calcular as temperaturas experienciadas em órbita pelo satélite e decisões têm que ser tomadas para garantir o sucesso da missão. Tal como nas análises anteriores, o comportamento dinâmico do CubeSat sob condições de lançamento pode também definir a linha entre sucesso e fracasso. Este trabalho descreve os passos seguidos para simular todos os aspetos supracitados, para o tempo da missão estimado, de modo a minimizar os riscos associados e garantir o sucesso da missão do ORCA2Sat, um CubeSat de duas unidades. Simulações foram feitas através de modelos de elementos finitos pertinentes e modelos computacionais do ambiente espacial, para um lançamento desde a Estação Espacial Internacional. Foi provado, através de uma abrangente análise da missão, que para os fatores críticos estudados a missão do ORCA2Sat poder ser efetuada para o período de tempo desejado, mantendo o satélite operacional ao longo do seu tempo em órbita