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Author: Karl E. Jensen Publisher: ISBN: 9781423559764 Category : Languages : en Pages : 127
Book Description
First-order solutions indicate that a forced Keplerian trajectory (FKT) obtained by thrust-drag cancellation is as fuel-efficient as a Hohmann transfer. Further analysis has shown that the FKT is not Mayer-optimal. Therefore there must exist another trajectory that matches or exceeds the efficiency of the Hohmann transfer. The application of this result to the fuel- optimal orbit maintenance problem implies that periodic reboosts must be more efficient than an WT profile. This research begins with the formulation of an optimal periodic control (OPC) problem to determine the minimum fuel-reboost strategy. The problem is numerically solved by a spectral collocation method. The optimization code is further modified to increase accuracy and reduce sensitivity to initial guesses. The results of this effort identified a trajectory for a sample satellite that was 3.5% more efficient than an ideal impulsive Hohmann transfer over the same period of time. From the optimal code, a maximum thruster size is also identifiable for a set of initial conditions. The optimal trajectory can save as much as 10% of the propellant budget when compared to finite-bum Hohmann transfers.
Author: Karl E. Jensen Publisher: ISBN: 9781423559764 Category : Languages : en Pages : 127
Book Description
First-order solutions indicate that a forced Keplerian trajectory (FKT) obtained by thrust-drag cancellation is as fuel-efficient as a Hohmann transfer. Further analysis has shown that the FKT is not Mayer-optimal. Therefore there must exist another trajectory that matches or exceeds the efficiency of the Hohmann transfer. The application of this result to the fuel- optimal orbit maintenance problem implies that periodic reboosts must be more efficient than an WT profile. This research begins with the formulation of an optimal periodic control (OPC) problem to determine the minimum fuel-reboost strategy. The problem is numerically solved by a spectral collocation method. The optimization code is further modified to increase accuracy and reduce sensitivity to initial guesses. The results of this effort identified a trajectory for a sample satellite that was 3.5% more efficient than an ideal impulsive Hohmann transfer over the same period of time. From the optimal code, a maximum thruster size is also identifiable for a set of initial conditions. The optimal trajectory can save as much as 10% of the propellant budget when compared to finite-bum Hohmann transfers.
Author: Lawrence E. Halbach Publisher: ISBN: 9781423532118 Category : Languages : en Pages : 92
Book Description
This thesis studies the fuel optimal periodic reboost profile required to maintain a spacecraft experiencing drag in low-earth-orbit (LEO). Recent advances in computational optimal control theory are employed, along with a Legendre-Gauss-Lobatto Pseudospectral collocation code developed at the Naval Postgraduate School, to solve the problem. Solutions obtained by this method are compared against a previous study. Key issues were checking the optimality of the solutions by way of the necessary conditions and the behavior of the solution to changes in the thruster size. The results confirmed Jensen's findings of propellant savings of one to five percent when compared against a middle altitude Forced Keplerian Trajectory (FKT). Larger savings are predicted if compared against a finite-burn Hohmann transfer with drag. The costates estimates compared favorably against necessary conditions of Pontryagin's Minimum Principle. Analysis of the switching flinction yielded periods of thrust-modulated arcs. The optimal thrust profile appears to be a thrust- modulated burn to raise the orbit followed by an orbital decay and a terminating thrust-modulated arc. For a sufficiently low thrust-control authority, the switching structure includes a maximum thrust arc. Indirect optimization techniques to confirm these findings were unsuccessful.
Author: American Astronautical Society Contributors Publisher: Univelt Incorporated ISBN: 0877035970 Category : Technology & Engineering Languages : en Pages : 175
Book Description
Advances in the Astronautical Sciences Series Volume 148 is a collection of scientific papers that were presented at the American Astronautical Society/American Institute of Aeronautics and Astronautics Spaceflight Mechanics Meeting held February 10-14, 2013, in Kauai, Hawaii.
Author: National Research Council Publisher: National Academies Press ISBN: 0309306590 Category : Technology & Engineering Languages : en Pages : 413
Book Description
Created in 1982 through the Small Business Innovation Development Act, the Small Business Innovation Research (SBIR) program remains the nation's single largest innovation program for small business. The SBIR program offers competitive awards to support the development and commercialization of innovative technologies by small private-sector businesses. At the same time, the program provides government agencies with technical and scientific solutions that address their different missions. SBIR at the Department of Defense considers ways that the Department of Defense SBIR program could work better in addressing the congressional objectives for the SBIR program to stimulate technological innovation, use small businesses to meet federal research and development (R & D) needs, foster and encourage the participation of socially and economically disadvantaged small businesses, and increase the private sector commercialization of innovations derived from federal R&D. An earlier report, An Assessment of the Small Business Innovation Research Program at the Department of Defense, studied how the SBIR program has stimulated technological innovation and used small businesses to meet federal research and development needs. This report builds on the previous one, with a revised survey of SBIR companies. SBIR at the Department of Defense revisits some case studies from the 2009 study and develops new ones, and interviews agency managers and other stakeholders to provide a second snapshot of the program's progress toward achieving its legislative goals.
Author: Wade H. Shafer Publisher: Springer Science & Business Media ISBN: 1461303931 Category : Science Languages : en Pages : 427
Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS)* at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dis semination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volumes were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 39 (thesis year 1994) a total of 13,953 thesis titles from 21 Canadian and 159 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this impor tant annual reference work. While Volume 39 reports theses submitted in 1994, on occasion, certain uni versities do report theses submitted in previous years but not reported at the time.
Author: Kyle Alfriend Publisher: Elsevier ISBN: 0080559654 Category : Technology & Engineering Languages : en Pages : 403
Book Description
Space agencies are now realizing that much of what has previously been achieved using hugely complex and costly single platform projects—large unmanned and manned satellites (including the present International Space Station)—can be replaced by a number of smaller satellites networked together. The key challenge of this approach, namely ensuring the proper formation flying of multiple craft, is the topic of this second volume in Elsevier's Astrodynamics Series, Spacecraft Formation Flying: Dynamics, control and navigation. In this unique text, authors Alfriend et al. provide a coherent discussion of spacecraft relative motion, both in the unperturbed and perturbed settings, explain the main control approaches for regulating relative satellite dynamics, using both impulsive and continuous maneuvers, and present the main constituents required for relative navigation. The early chapters provide a foundation upon which later discussions are built, making this a complete, standalone offering. Intended for graduate students, professors and academic researchers in the fields of aerospace and mechanical engineering, mathematics, astronomy and astrophysics, Spacecraft Formation Flying is a technical yet accessible, forward-thinking guide to this critical area of astrodynamics. - The first book dedicated to spacecraft formation flying, written by leading researchers and professors in the field - Develops the theory from an astrodynamical viewpoint, emphasizing modeling, control and navigation of formation flying satellites on Earth orbits - Examples used to illustrate the main developments, with a sample simulation of a formation flying mission included to illustrate high fidelity modeling, control and relative navigation
Author: William Emery Publisher: Elsevier ISBN: 0128092599 Category : Science Languages : en Pages : 872
Book Description
Introduction to Satellite Remote Sensing: Atmosphere, Ocean and Land Applications is the first reference book to cover ocean applications, atmospheric applications, and land applications of remote sensing. Applications of remote sensing data are finding increasing application in fields as diverse as wildlife ecology and coastal recreation management. The technology engages electromagnetic sensors to measure and monitor changes in the earth's surface and atmosphere. The book opens with an introduction to the history of remote sensing, starting from when the phrase was first coined. It goes on to discuss the basic concepts of the various systems, including atmospheric and ocean, then closes with a detailed section on land applications. Due to the cross disciplinary nature of the authors' experience and the content covered, this is a must have reference book for all practitioners and students requiring an introduction to the field of remote sensing. - Provides study questions at the end of each chapter to aid learning - Covers all satellite remote sensing technologies, allowing readers to use the text as instructional material - Includes the most recent technologies and their applications, allowing the reader to stay up-to-date - Delves into laser sensing (LIDAR) and commercial satellites (DigitalGlobe) - Presents examples of specific satellite missions, including those in which new technology has been introduced
Author: Karl E. Jensen
Author: Karl E. Jensen
Author: Lawrence E. Halbach
Author: 
Author: United States. Naval Postgraduate School, Monterey, CA.
Author: 
Author: American Astronautical Society Contributors
Author: National Research Council
Author: Wade H. Shafer
Author: Kyle Alfriend
Author: William Emery