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Saleh,
Joseph H.
Saleh,
Joseph H.
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ItemSurvivability and Resiliency of Spacecraft and Space-Based Networks: a Framework for Characterization and Analysis, Version 2(Georgia Institute of Technology, 2008-09-09) Castet, Jean-Francois ; Saleh, Joseph H.Considerations of survivability and resiliency have always been of importance in the design and analysis of military systems. Over the past two decades, the importance of survivability and resiliency has expanded beyond military systems to include public networks and infrastructure systems. The analysis and assessment of networked systems with respect to survivability has become particularly acute in recent years, as attested to by a growing technical literature on the subject. In this paper, we bring these considerations of survivability and resiliency to bear on spacecraft and space-based networks. We develop a framework for comparing the survivability and resiliency of different space architectures, namely that of a monolithic design and a distributed (or networked) space system architecture. There are multiple metrics along which different space architectures can be benchmarked and compared. We argue that if survivability and resiliency are not accounted for, then the evaluation process is likely to be biased in favor of monolithic spacecraft. We show that if in a given context survivability and resiliency are an important requirement for a particular customer, then a distributed architecture is more likely to satisfy this requirement than a monolithic spacecraft design. We discuss in the context of our framework different classes of threats, as well as the high-frequency and low-frequency system response to (or coping strategies with) these shocks or damaging events. We illustrate the importance of this characterization for a formal definition of survivability and resiliency and a proper quantitative analysis of the subject. Finally, we propose in future work to integrate our framework with a design tool that allows the exploration of the design trade-space of distributed space architecture and show how survivability can be “optimized” or traded against other system attributes.
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ItemSurvivability and Resiliency of Spacecraft and Space-Based Networks: a Framework for Characterization and Analysis, Version 1(Georgia Institute of Technology, 2008-09) Castet, Jean-Francois ; Saleh, Joseph H.Considerations of survivability and resiliency have always been of importance in the design and analysis of military systems. Over the past two decades, the importance of survivability and resiliency has expanded beyond military systems to include public networks and infrastructure systems. The analysis and assessment of networked systems with respect to survivability has become particularly acute in recent years, as attested to by a growing technical literature on the subject. In this paper, we bring these considerations of survivability and resiliency to bear on spacecraft and space-based networks. We develop a framework for comparing the survivability and resiliency of different space architectures, namely that of a monolithic design and a distributed (or networked) space system architecture. There are multiple metrics along which different space architectures can be benchmarked and compared. We argue that if survivability and resiliency are not accounted for, then the evaluation process is likely to be biased in favor of monolithic spacecraft. We show that if in a given context survivability and resiliency are an important requirement for a particular customer, then a distributed architecture is more likely to satisfy this requirement than a monolithic spacecraft design. We discuss in the context of our framework different classes of threats, as well as the high-frequency and low-frequency system response to (or coping strategies with) these shocks or damaging events. We illustrate the importance of this characterization for a formal definition of survivability and resiliency and a proper quantitative analysis of the subject. Finally, we propose in future work to integrate our framework with a design tool that allows the exploration of the design trade-space of distributed space architecture and show how survivability can be “optimized” or traded against other system attributes.
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ItemResponsive Space: Concept Analysis, Critical Review, and Theoretical Framework(Georgia Institute of Technology, 2007-09) Saleh, Joseph H. ; Dubos, GregoryCustomers’ needs are dynamic and evolve in response to unfolding environmental uncertainties. The ability of a company or an industry to address these changing customers’ needs in a timely and cost-effective way is a measure of its responsiveness. In the space industry, a systemic discrepancy exists between the time constants associated with the change of customers’ needs, and the response time of the industry in delivering on-orbit solutions to these needs. Increasingly, the penalties associated with such delays are becoming unacceptable, and space responsiveness is recognized as a strategic imperative in commercial competitive and military environments. In this paper, we provide a critical assessment of the literature on responsive space and introduce a new multi-disciplinary framework for thinking about and addressing issues of space responsiveness. Our framework advocates three levels of responsiveness: a global industry-wide responsiveness, a local stakeholder responsiveness, and an interactive or inter-stakeholder responsiveness. We introduce and motivate the use of “responsiveness maps” for multiple stakeholders. We then identify “levers of responsiveness,” technical spacecraft- and launch-centric, as well as “soft” levers (e.g., acquisition policies) for improving the responsiveness of the space industry. Finally, we propose a series of research questions to aggressively tackle problems associated with space responsiveness.
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ItemTechnology Readiness Level, Schedule Risk and Slippage in Spacecraft Design: Data Analysis and Modeling(Georgia Institute of Technology, 2007-09) Dubos, Gregory F. ; Saleh, Joseph H. ; Braun, Robert D.Schedule slippage plagues the space industry, and is antinomic with the recent emphasis on space responsiveness. The Government Accountability Office has repeatedly noted the difficulties encountered by the Department of Defense in keeping its acquisition of space systems on schedule, and identified the low Technology Readiness Level (TRL) of the system/payload under development as a principal culprit driving schedule risk and slippage. In this paper, we analyze based on data from past space programs the relationship between technology uncertainty and schedule risk in the acquisition of space systems, and propose an analytical framework to identify appropriate schedule margins for mitigating the risk of schedule slippage. We also introduce the TRL-schedule-risk curves to help program managers make riskinformed decisions regarding the appropriate schedule margins for a given program, or the appropriate TRL to consider should the program’s schedule be exogenously and rigidly constrained. We recommend based on our findings, that the industry adopts and develops schedule risk curves (instead of single schedule point estimates), 2) that these schedule risk curves be made available to policy- and decision-makers in acquisition programs; and 3) that adequate schedule margins be defined according to an agreed upon and acceptable schedule risk level.