Isoperformance An Alternative Design Methodology for Engineering Systems

Tradeoffs between performance, cost and risk frequently arise during architecting and design of complex Engineering Systems such as aerospace vehicles. A paradigm shift is occurring from the pure performance optimization approach of the past towards satisfying of performance targets under concurrent risk and cost minimization. This paper proposes “isoperformance” as a set based approach to designing engineering systems by first identifying the acceptable performance invariant set of designs from which a final design is chosen. This is in contrast to a multiobjective cost-risk minimization under performance equality constraints. This paper identifies a number of issues associated with finding the desired performance invariant set, I, given a deterministic or empirical system model that maps design variables x to objective variables J. Isoperformance is presented as a methodology that can quantify and visualize the tradeoffs between determinants (independent design variables) of a known or desired outcome. For deterministic systems the multivariable performance invariant contours can be computed using sensitivity analysis and a contour following algorithm, provided that a mathematical system model of appropriate fidelity exists. In the case of stochastic systems the isoperformance curves can be obtained via a regression analysis, given a statistically representative data set. Once isoperformance curves have been obtained, they are useful in extracting a set of performance invariant solutions. Applying additional objectives, other than performance, can then lead to a set of pareto-optimal designs. Specific examples from opto-mechanical space systems design and human factors are presented

A Classification of Uncertainty for Early Product and System Design

Complex systems and products evolve over years to meet new requirements, while applying tried and tested technology. To maximise the reuse of components through the life span, companies need to plan for the changes that they can anticipate, and facilitate accommodation of such changes in the original architecture and design of the system. Methods such as design for flexibility or design for changeability promote incorporation of future uncertain outcomes into system and product design in one way or another. However, the degree to which future product changes can be planned depends on the uncertainties that the system, product or product family is subject to. A deeper understanding of these uncertainties is the focus of this paper. The paper first provides a brief literature survey, and discusses the sources and nature of uncertainty. This is followed by a classification of the types of uncertainties that are often encountered and that should be considered, as well as methods and techniques for modelling these uncertainties for incorporation in system design. The paper also provides examples of uncertainties for a variety of systems and products throughout and concludes with an uncertainty checklist for system architects and product designers

Quantifying End-Use Energy Intensity of the Urban Water Cycle

The water end-use segment (WES), consisting of activities that utilize water in homes and buildings, has been identified as a major component of energy use in the urban water supply system. In this paper, an analytical framework is presented which can be used at the planning stages of new urban developments to assess future building-level water demands and associated energy requirements. The framework is applied to Masdar City, a new urban area in the United Arab Emirates, which has been targeted in its design to be a future zero-carbon and zero-waste city. Results show that the energy intensity (in electric kWh) in WES for Masdar City may range from 2.6 to 4 kWh=m3. The dominant use of energy in this segment is attributed to water heating requirements, and the total energy use for obtaining hot water is estimated to range from approximately 20 to 50 million kWh annually. It is found that the residential sector in the city can have the greatest impact in affecting energy requirements associated with water use. For every unit reduction (in L=person=day) of indoor residential water use, it is estimated that up to 225 MWh may be saved annually

Strategic Engineering Gaming for Improved Design and Interoperation of Infrastructure Systems

Large physical networks of interrelated infrastructure components support modern societies as a collaborative system with significant technical and social complexity. Design and evolution of infrastructure systems seeks to reduce wasted resources and maximize lifecycle value. Interdependencies between constituent systems call for an integrative approach to improve interoperation but many existing techniques rely on centralized development and emphasize technical aspects of design. This paper presents a simulation gaming approach to collaborative infrastructure system design leveraging the technical strengths of simulation models and the social strengths of multi-player engagement in a game execution. In a strategic engineering game, models representing each constituent infrastructure system share a common graph-theoretic modeling framework and are integrated using the HLA-Evolved standard for interoperable federated simulations. A prototype game instantiation based on a space-based resource economy supporting future space exploration is discussed with the objective of identifying how factors of game play influence insights to collaborative system design. Future work seeks to develop, execute, and evaluate the prototype game to further research the use of simulation games in supporting collaborative system design

An integrated modeling framework for infrastructure system-of-systems simulation

Design of future hard infrastructure must consider emergent behaviors from cross-system interdependencies. Understanding these interdependencies is challenging due to high levels of integration in high-performance systems and their operation as a collaborative system-of-systems managed by multiple organizations. Existing modeling frameworks have limitations for strategic planning either because important spatial structure attributes have been abstracted out or behavioral models are oriented to shorter-term analysis with a static network structure. This paper presents a formal modeling framework as a first step to integrating infrastructure system models in a system-of-systems simulation addressing these concerns. First, a graph-theoretic structural framework captures the spatial dimension of physical infrastructure. An element's simulation state includes location, parent, resource contents, and operational state properties. Second, a functional behavioral framework captures the temporal dimension of infrastructure operations at a level suitable for strategic analysis. Resource behaviors determine the flow of resources into or out of nodes and element behaviors modify other state including the network structure. Two application use cases illustrate the usefulness of the modeling framework in varying contexts. The first case applies the framework to future space exploration infrastructure with an emphasis on mobile system elements and discrete resource flows. The second case applies the framework to infrastructure investment in Saudi Arabia with an emphasis on immobile system elements aggregated at the city level and continuous resource flows. Finally, conclusions present future work planned for implementing the framework in a simulation software tool.American Society for Engineering Education. National Defense Science and Engineering Graduate Fellowshi

Limitations of Reliability for Long-Endurance Human Spaceflight

Long-endurance human spaceflight - such as missions to Mars or its moons - will present a never-before-seen maintenance logistics challenge. Crews will be in space for longer and be farther way from Earth than ever before. Resupply and abort options will be heavily constrained, and will have timescales much longer than current and past experience. Spare parts and/or redundant systems will have to be included to reduce risk. However, the high cost of transportation means that this risk reduction must be achieved while also minimizing mass. The concept of increasing system and component reliability is commonly discussed as a means to reduce risk and mass by reducing the probability that components will fail during a mission. While increased reliability can reduce maintenance logistics mass requirements, the rate of mass reduction decreases over time. In addition, reliability growth requires increased test time and cost. This paper assesses trends in test time requirements, cost, and maintenance logistics mass savings as a function of increase in Mean Time Between Failures (MTBF) for some or all of the components in a system, based on a review of reliability growth models in literature and a quantitative case study. In general, reliability growth results in superlinear growth in test time requirements, exponential growth in cost, and sublinear benefits in terms of maintenance logistics mass saved. In the Mars transit case study examined here, doubling the reliability of all components results in a 24% reduction in corrective maintenance mass requirements. However, if only some components experience improved reliability the benefits are reduced; if only the ten largest contributors to corrective maintenance requirements experience doubled reliability, the decrease in mass is reduced to 9%. These trends indicate that it is unlikely that reliability growth alone will be a cost-effective approach to maintenance logistics mass reduction and risk mitigation for long-endurance missions. This paper discusses these trends as well as other options to reduce logistics mass such as direct reduction of part mass, commonality, or In-Space Manufacturing (ISM). Overall, it is likely that some combination of all available options - including reliability growth - will be required to reduce mass and mitigate risk for future deep space missions.United States. National Aeronautics and Space Administration. Space Technology Research Fellowship (NNX14AM42H

Collaboration and complexity: an experiment on the effect of multi-actor coupled design

Design of complex systems requires collaborative teams to overcome limitations of individuals; however, teamwork contributes new sources of complexity related to information exchange among members. This paper formulates a human subjects experiment to quantify the relative contribution of technical and social sources of complexity to design effort using a surrogate task based on a parameter design problem. Ten groups of 3 subjects each perform 42 design tasks with variable problem size and coupling (technical complexity) and team size (social complexity) to measure completion time (design effort). Results of a two-level regression model replicate past work to show completion time grows geometrically with problem size for highly coupled tasks. New findings show the effect of team size is independent from problem size for both coupled and uncoupled tasks considered in this study. Collaboration contributes a large fraction of total effort, and it increases with team size: about 50–60 % of time and 70–80 % of cost for pairs and 60–80 % of time and 90 % of cost for triads. Conclusions identify a role for improved design methods and tools to anticipate and overcome the high cost of collaboration.American Society for Engineering Education. National Defense Science and Engineering Graduate Fellowshi

Federated Simulation and Gaming Framework for a Decentralized Space-Based Resource Economy

Future human space exploration will require large amounts of resources for shielding and building materials, propellants, and consumables. A space-based resource economy could produce, transport, and store resource at distributed locations such as the lunar surface, stable orbits, or Lagrange points to avoid Earth's deep gravity well. Design challenges include decentralized operation and management and socio-technical complexities not commonly addressed by modeling and simulation methods. This paper seeks to tackle these challenges by applying aspects of military wargaming to promote effective communication between decision-makers. A software architecture for federated simulation based on IEEE-1516 (HLA-Evolved) is presented in the context of multiple lunar in-situ resource production processes, resource depots, and intermediate transportation. The federation-level framework identifies interfaces between simulation models (federates), focusing on persistent assets (elements) and resources exchanged. Future work will develop the federated resource economy model and evaluate with decision-makers playing the roles of competing and collaborating players.United States. Dept. of DefenseUnited States. Air Force Office of Scientific ResearchAmerican Society for Engineering Education. National Defense Science and Engineering Graduate Fellowship (32 CFR 168a

Innovation Dynamics in the Development of Nuclear Energy and Electric Vehicles in France

Technological change is shaped by a confluence of processes that are governed by socio-political, economic, and regulatory factors within a region. In this paper we describe the transformation of the electricity generation system in France and the emerging changes in the transportation sector in the country. We trace the impact of national energy security policy in France after the 1973 oil crisis that catalyzed a shift from dependence on fossil fuel to nuclear power, and then examine the continuing impacts of that legacy that are now emerging through development and deployment of electric vehicles in the country. We examine the two cases of nuclear power and electric vehicles in France using processes of innovation, and discuss the interaction of these processes that formed reinforcing loops to advance these technologies in the country and highlight the role of sustained policy in initiating and driving the reinforcing cycles. We also discuss the issue of new emerging linkages between the electric power generation and transportation sectors that were traditionally decoupled due to use of different fuel sources. We expand the notion of path dependence, and discuss how established technologies in one sector can shape future technological trajectory in other sectors

Limitations of Reliability for Long-Endurance Human Spaceflight

Long-endurance human spaceflight - such as missions to Mars or its moons - will present a never-before-seen maintenance logistics challenge. Crews will be in space for longer and be farther way from Earth than ever before. Resupply and abort options will be heavily constrained, and will have timescales much longer than current and past experience. Spare parts and/or redundant systems will have to be included to reduce risk. However, the high cost of transportation means that this risk reduction must be achieved while also minimizing mass. The concept of increasing system and component reliability is commonly discussed as a means to reduce risk and mass by reducing the probability that components will fail during a mission. While increased reliability can reduce maintenance logistics mass requirements, the rate of mass reduction decreases over time. In addition, reliability growth requires increased test time and cost. This paper assesses trends in test time requirements, cost, and maintenance logistics mass savings as a function of increase in Mean Time Between Failures (MTBF) for some or all of the components in a system. In general, reliability growth results in superlinear growth in test time requirements, exponential growth in cost, and sublinear benefits (in terms of logistics mass saved). These trends indicate that it is unlikely that reliability growth alone will be a cost-effective approach to maintenance logistics mass reduction and risk mitigation for long-endurance missions. This paper discusses these trends as well as other options to reduce logistics mass such as direct reduction of part mass, commonality, or In-Space Manufacturing (ISM). Overall, it is likely that some combination of all available options - including reliability growth - will be required to reduce mass and mitigate risk for future deep space missions