The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Joseph H. Saleh - One of the best experts on this subject based on the ideXlab platform.
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toward a new spacecraft optimal Design Lifetime impact of marginal cost of durability and reduced launch price
Acta Astronautica, 2016Co-Authors: Kailah B Snelgrove, Joseph H. SalehAbstract:Abstract The average Design Lifetime of satellites continues to increase, in part due to the expectation that the satellite cost per operational day decreases monotonically with increased Design Lifetime. In this work, we challenge this expectation by revisiting the durability choice problem for spacecraft in the face of reduced launch price and under various cost of durability models. We first provide a brief overview of the economic thought on durability and highlight its limitations as they pertain to our problem (e.g., the assumption of zero marginal cost of durability). We then investigate the merging influence of spacecraft cost of durability and launch price, and we identify conditions that give rise cost-optimal Design Lifetimes that are shorter than the longest Lifetime technically achievable. For example, we find that high costs of durability favor short Design Lifetimes, and that under these conditions the optimal choice is relatively robust to reduction in launch prices. By contrast, lower costs of durability favor longer Design Lifetimes, and the optimal choice is highly sensitive to reduction in launch price. In both cases, reduction in launch prices translates into reduction of the optimal Design Lifetime. Our results identify a number of situations for which satellite operators would be better served by spacecraft with shorter Design Lifetimes. Beyond cost issues and repeat purchases, other implications of long Design Lifetime include the increased risk of technological slowdown given the lower frequency of purchases and technology refresh, and the increased risk for satellite operators that the spacecraft will be technologically obsolete before the end of its life (with the corollary of loss of value and competitive advantage). We conclude with the recommendation that, should pressure to extend spacecraft Design Lifetime continue, satellite manufacturers should explore opportunities to lease their spacecraft to operators, or to take a stake in the ownership of the asset on orbit.
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Durability choice and optimal Design Lifetime for complex engineering systems
Journal of Engineering Design, 2008Co-Authors: Joseph H. SalehAbstract:This paper addresses the durability choice problem of complex engineering systems, as seen from the customer's perspective and in the face of network externalities and obsolescence effects. Economists have investigated the impact of market structure on manufacturers’ durability choice (under monopolistic or competitive market conditions); this paper departs from the literature on the subject by addressing the durability choice problem from the customer's perspective, and an ‘optimal’ durability is sought that maximises the Net Present Value of an asset for the customer (as opposed to maximising the profits of the manufacturer). First, the various qualitative implications for reducing or extending a system's durability are discussed. Second, analytical results for the optimal durability are derived under steady-state and deterministic assumptions. Trends and functional dependence of the optimal durability on various parameters are identified and discussed. Third, the durability choice problem is explored w...
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Analyses for Durability and System Design Lifetime: A Multidisciplinary Approach
2007Co-Authors: Joseph H. SalehAbstract:An issue in engineering Design is a system's Design Lifetime. This book provides a systemic qualitative and quantitative approach to these problems addressing, first, the technicality of durability, second, the marginal cost of durability, and, third, the durability choice problem for complex systems with network externalities (competition and market uncertainty) and obsolescence (technology evolution). Also addressed is the increasing tension between the Design Lifetimes of complex systems and the shortening time scales associated with the obsolescence of the technology. The book ends with a discussion of flexibility in system Design. Dr. Joseph H. Saleh is an Assistant Professor of Aerospace Engineering at the Georgia Institute of Technology. He received his Ph.D. from the Department of Aeronautics and Astronautics at MIT and served as the Executive Director for the Ford-MIT Alliance. His research focuses on issues of Design Lifetime and how to embed flexibility in the Design of complex engineering systems in general and in aerospace system in particular. Dr. Saleh is the author or co-author of 50 technical publications and the recipient of numerous awards for his teaching and research contributions. He served as a technical consultant to NASA's Jet Propulsion Laboratory and has collaborated on research projects with various aerospace companies.
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To reduce or to extend a spacecraft Design Lifetime
Journal of Spacecraft and Rockets, 2006Co-Authors: Joseph H. Saleh, Daniel E. Hastings, Juan-pablo Torres-padilla, Dava J. NewmanAbstract:The engineering and economic issues at stake for reducing or extending a complex system’s Design Lifetime are investigated using a spacecraft as an example. These issues are examined from an operator perspective, a manufacturer’s perspective, as well as from the perspective of society at large. The question of whether there is an optimal Design Lifetime for complex engineering systems in general, and spacecraft in particular, and what it takes to answer this question is addressed. Preliminary results indicate that optimal Design Lifetimes do exist that maximize a system’s value metric. Therefore, even if it is technically feasible to field a system or launch spacecraft with a longer Lifetime, it is not necessarily in the best interest of an operator, and definitely not in the interest of the manufacturer, to do so. Preliminary results also show that the Design Lifetime is, in the case of a spacecraft, a key requirement in sizing various subsystems and, consequently, has a significant impact on the overall cost of the spacecraft. Additionally, at the level of the entire space industry value chain, the spacecraft Design Lifetime is a powerful lever that can significantly impact the whole space industry’s performance. Overall, it is shown that the selection of a spacecraft Design Lifetime begs careful consideration and requires much more attention than it has received so far in the literature because its impact will ripple throughout an entire industry value chain.
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Beyond cost models: communications satellite revenue models. Integrating cost considerations into a value‐centric mindset
International Journal of Satellite Communications and Networking, 2006Co-Authors: Joseph H. Saleh, J. P. Torres PadillaAbstract:While satellite cost models are pervasive throughout the aerospace industry, revenue models or utility models of space systems are quasi-inexistent. This situation perhaps conveys the false impression that satellites are either cost sinks or expensive artefacts whose value or utility profile over their Design Lifetime is difficult to quantify. In this paper, we propose that satellites, like any other complex engineering systems, should be perceived as value delivery artefacts, and the value delivered, or the flow of service that the spacecraft delivers over its Design Lifetime, deserves as much effort to quantify as the system's cost. To this effect, we build, in the case of a GEO communications satellite, revenue models based on (1) statistical analyses of spacecraft loading dynamics and (2) historical trends of market prices for the communications services provided. Results and discussions presented here should prove useful to satellite operators and industry observers. Copyright © 2006 John Wiley & Sons, Ltd.
Dava J. Newman - One of the best experts on this subject based on the ideXlab platform.
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To reduce or to extend a spacecraft Design Lifetime
Journal of Spacecraft and Rockets, 2006Co-Authors: Joseph H. Saleh, Daniel E. Hastings, Juan-pablo Torres-padilla, Dava J. NewmanAbstract:The engineering and economic issues at stake for reducing or extending a complex system’s Design Lifetime are investigated using a spacecraft as an example. These issues are examined from an operator perspective, a manufacturer’s perspective, as well as from the perspective of society at large. The question of whether there is an optimal Design Lifetime for complex engineering systems in general, and spacecraft in particular, and what it takes to answer this question is addressed. Preliminary results indicate that optimal Design Lifetimes do exist that maximize a system’s value metric. Therefore, even if it is technically feasible to field a system or launch spacecraft with a longer Lifetime, it is not necessarily in the best interest of an operator, and definitely not in the interest of the manufacturer, to do so. Preliminary results also show that the Design Lifetime is, in the case of a spacecraft, a key requirement in sizing various subsystems and, consequently, has a significant impact on the overall cost of the spacecraft. Additionally, at the level of the entire space industry value chain, the spacecraft Design Lifetime is a powerful lever that can significantly impact the whole space industry’s performance. Overall, it is shown that the selection of a spacecraft Design Lifetime begs careful consideration and requires much more attention than it has received so far in the literature because its impact will ripple throughout an entire industry value chain.
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weaving time into system architecture satellite cost per operational day and optimal Design Lifetime
Acta Astronautica, 2004Co-Authors: Joseph H. Saleh, Daniel E. Hastings, Dava J. NewmanAbstract:Abstract An augmented perspective on system architecture is proposed (diachronic) that complements the traditional views on system architecture (synchronic). This paper proposes to view in a system architecture the flow of service (or utility) that the system will provide over its Design Lifetime. It suggests that the Design Lifetime is a fundamental component of system architecture although one cannot see it or touch it. Consequently, cost, utility, and value per unit time metrics are introduced. A framework is then developed that identifies optimal Design Lifetimes for complex systems in general, and space systems in particular, based on this augmented perspective of system architecture and on these metrics. It is found that an optimal Design Lifetime for a satellite exists, even in the case of constant expected revenues per day over the system's Lifetime, and that it changes substantially with the expected Time to Obsolescence of the system and the volatility of the market the system is serving in the case of a commercial venture. The analysis thus proves that it is essential for a system architect to match the Design Lifetime with the dynamical characteristics of the environment the system is/will be operating in. It is also shown that as the uncertainty in the dynamical characteristics of the environment the system is operating in increases, the value of having the option to upgrade, modify, or extend the Lifetime of a system at a later point in time increases depending on how events unfold.
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To Reduce or to Extend a Spacecraft Design Lifetime? What is at Stake, for Whom, and How to Resolve the Dilemma
2004Co-Authors: Joseph H. Saleh, Daniel E. Hastings, Juan-pablo Torres-padilla, Dava J. NewmanAbstract:∗The attitude towards systems Design Lifetime has often been ambiguous, and at times uninformed. Although the issue has received almost no attention in the technical literature, there have been a few qualitative arguments fraught with subjectivity for or against extending a system Design Lifetime. In this paper, we explore the engineering and economic issues at stake for reducing or extending a complex system’s Design Lifetime using spacecraft as example. The study examines these issues from an operator/customer’s perspective, a manufacturer’s perspective as well as from the perspective of society at large. We address the question of whether there is an optimal Design Lifetime for complex engineering systems in general, and spacecraft in particular, and what it takes to answer this question. Our approach constitutes a fundamental addition to the traditional thinking about system Design and architecture, and involves quantitative analyses of both dynamics and volatility of the market the system is serving in the case of a commercial venture, and the obsolescence of the system’s technology base. Preliminary results indicate that optimal Design Lifetimes do exist that maximizes a system’s financial/value metric. Therefore even if it is technically feasible to field a system or launch spacecraft with a longer Lifetime, it is not necessarily in the best interest of an operator, and definitely not in the interest of the manufacturer, to do so. Preliminary results also show that the Design Lifetime is, in the case of a spacecraft, a key requirement in sizing various subsystems‐and consequently has a significant impact on the overall cost of the spacecraft. Additionally, at the level of the entire space industry value chain, i.e., the spacecraft manufacturers, launch industry and the operators, the Design Lifetime is a powerful lever that can significantly impact the whole industry’s performance, financial health, and employment. Overall, we show that the specification or selection of a complex engineering system’s Lifetime begs careful consideration and requires much more attention than it has received so far in the literature as its impact will ripple throughout an entire industry value chain.
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Spacecraft Design Lifetime
Journal of Spacecraft and Rockets, 2002Co-Authors: Joseph H. Saleh, Daniel E. Hastings, Dava J. NewmanAbstract:A general discussion of issues that drive and limit spacecraft Design Lifetime is presented. The effects of varying the spacecraft Lifetime requirement on different subsystems are explored, and typical spacecraft mass andcost profiles are deduced. Quantitative analyses confirm that the Design Lifetime is a key requirement in sizing various subsystems and significantly affects the spacecraft mass and cost to initial operating capability. The analysis introduces a formally defined economic metric, the cost per operational day, to help guide the specification of the Design Lifetime requirement. Preliminary results suggest that other factors should also be taken into account in specifying the Design Lifetime, namely, the loss of value resulting from technology obsolescence as well as the volatility of the market the system is serving in the case of a commercial satellite.
N. Schartel - One of the best experts on this subject based on the ideXlab platform.
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XMM-Newton operations beyond the Design Lifetime
Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, 2012Co-Authors: Arvind Parmar, Marcus Kirsch, J. Ramon Muñoz, Maria Santos-lleo, N. SchartelAbstract:After more than twelve years in orbit and two years beyond the Design Lifetime, XMM-Newton continues its near faultless operations providing the worldwide astronomical community with an unprecedented combination of imaging and spectroscopic X-ray capabilities together with simultaneous optical and ultra-violet monitoring. The interest from the scientific community in observing with XMM-Newton remains extremely high with the last annual Announcement of Observing Opportunity (AO-11) attracting proposals requesting 6.7 times more observing time than was available. Following recovery from a communications problem in 2008, all elements of the mission are stable and largely trouble free. The operational Lifetime if currently limited by the amount of available hydrazine fuel. XMM-Newton normally uses reaction wheels for attitude control and fuel is only used when offsetting reaction wheel speed away from limiting values and for emergency Sun acquisition following an anomaly. Currently, the hydrazine is predicted to last until around 2020. However, ESA is investigating the possibility of making changes to the operations concept and the onboard software that would enable lower fuel consumption. This could allow operations to well beyond 2026.
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XMM‐Newton operations beyond the 10‐year Design Lifetime
Astronomische Nachrichten, 2008Co-Authors: A.n. Parmar, D. Heger, L. Metcalfe, R. Muñoz, N. SchartelAbstract:In preparation for XMM-Newton operations beyond the 10-year Design Lifetime ESA instigated an independent review of all aspects of the mission. Unsurprisingly, the review found that the scientific interest in extending the mission is very high and likely to remain so in the foreseeable future. Most importantly, all the elements of the XMM-Newton mission were found to be stable and trouble free with sufficient consumables and life-limited items to allow operations of the mission until at least 2018. The review endorsed the proposal to combine elements of the Flight Control Team with those from INTEGRAL and remove real-time instrument monitoring from ESAC in order to reduce costs and improve efficiency. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
A. Kryukov - One of the best experts on this subject based on the ideXlab platform.
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PALS combined with Charpy-V tests at WWER reactor pressure vessel steels
Journal of Physics: Conference Series, 2013Co-Authors: Vladimír Slugeň, Stanislav Sojak, Martin Petriska, V. Sabelová, A. Kryukov, Jana Veterníková, R. HincaAbstract:This paper presents results from our long-term studies of irradiated, commercially used WWER reactor pressure vessel steels. Results from Charpy-V tests and positron annihilation spectroscopy techniques are compared and discussed in details, having in mind actual state of art and other microstructural studies in this area. The optimal region for annealing of irradiation induced defects was analyzed. It was shown that WWER steel with low impurity contents has good radiation stability and operation these reactor pressure vessels could be extended beyond a Design Lifetime.
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Microstructural study of WWER reactor pressure vessel steels
Nuclear Engineering and Design, 2013Co-Authors: Vladimír Slugeň, A. KryukovAbstract:Abstract This paper presents results from our long-term studies of irradiated, commercially used WWER reactor pressure vessel steels. Results from Charpy-V tests and positron annihilation spectroscopy techniques are compared and discussed in details, having in mind actual state of art and other microstructural studies in this area. The optimal region for annealing of irradiation induced defects was analysed. It was shown that WWER steel with low impurity contents has good radiation stability and operation these reactor pressure vessels could be extended beyond a Design Lifetime.
Vladimír Slugeň - One of the best experts on this subject based on the ideXlab platform.
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PALS combined with Charpy-V tests at WWER reactor pressure vessel steels
Journal of Physics: Conference Series, 2013Co-Authors: Vladimír Slugeň, Stanislav Sojak, Martin Petriska, V. Sabelová, A. Kryukov, Jana Veterníková, R. HincaAbstract:This paper presents results from our long-term studies of irradiated, commercially used WWER reactor pressure vessel steels. Results from Charpy-V tests and positron annihilation spectroscopy techniques are compared and discussed in details, having in mind actual state of art and other microstructural studies in this area. The optimal region for annealing of irradiation induced defects was analyzed. It was shown that WWER steel with low impurity contents has good radiation stability and operation these reactor pressure vessels could be extended beyond a Design Lifetime.
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Microstructural study of WWER reactor pressure vessel steels
Nuclear Engineering and Design, 2013Co-Authors: Vladimír Slugeň, A. KryukovAbstract:Abstract This paper presents results from our long-term studies of irradiated, commercially used WWER reactor pressure vessel steels. Results from Charpy-V tests and positron annihilation spectroscopy techniques are compared and discussed in details, having in mind actual state of art and other microstructural studies in this area. The optimal region for annealing of irradiation induced defects was analysed. It was shown that WWER steel with low impurity contents has good radiation stability and operation these reactor pressure vessels could be extended beyond a Design Lifetime.
