Daniel DeLaurentis

Robust Design Simulation: A Probabilistic Approach to Multidisciplinary Design

Most current paradigms in multidisciplinary design analysis and optimization fail to address the presence of uncertainty at numerous levels of the design hierarchy and over the design process time line. Consequently, the issue of robustness of the design is neglected. An approach for the determination of robust design solutions is outlined in this paper, where uncertainty is quantified and its effects mitigated. The robust solution is found through maximization of the probability of an overall figure of merit achieving or exceeding a specified target. The proposed methodology is referred to as robust design simulation (RDS). Arguments as to why a probabilistic approach to aircraft design is preferable over the traditional deterministic approaches are presented, along with a step-by-step description of how one could implement the RDS. An application involving the high-speed civil transport is conducted as a case study to demonstrate the proposed method and to introduce an evaluation criterion that guarantees the highest customer satisfaction.

Understanding Transportation as a System-of-Systems Design Problem

*The purposes of this paper are to introduce an emerging class of problems called systemof-systems, present the primary traits of the class, and then described the relevant implications for the aerospace design community. Two primary traits, evolutionary and emergent behavior, are highlighted since they call attention to a network-of-systems, dynamic-behavior focus as opposed to an individual system, static-behavior focus. Further, methodological needs for investigation of these traits lie outside present capability in the community. To explore these implications in depth, the casting of future transportation concepts as a system-of-systems is described. A recently developed “proto-method” for this class of problems is presented and explored in the context of the transportation domain, including promising approaches for building effective modeling and simulation. The casting of civil transportation as a system-of-systems problem is important as much of the literature on system-of-systems (limited as it is) resides primarily in the defense systems domain. I. Introduction ROBLEMS of significant complexity are facing decision-makers within government and industry, and the moniker of “system-of-systems” (heretofore shortened to SoS) is increasingly being applied to problems of this type. Effective system analysis for decision-support quickly becomes unmanageable in this context, with multiple, heterogeneous, distributed systems involved and couched in networks at multiple levels. The situation is exacerbated by the fact that most organizations (and their processes) remain in the “stovepipe” mode- their people and tools are configured to study within narrow bins with little or no analysis across those bins. Current frames of reference, thought processes, analysis, and design methods are not complete for these SoS problems, exemplified in this paper by future national transportation system realizations. A holistic framework is needed that enables decision makers to discern whether related infrastructure, policy, and/or technology considerations together are good, bad (or indifferent) over time. 1 And this need is urgent, for the SoS type almost always involves decisions that commit large amounts of money, for which ultimate failure or success carries heavy consequences over several generations, and that impact large segments of the public. The costs associated with a chosen path may still be high, but the intent is to maximize the probability that these costs result in good consequences rather than bad. P

A Stochastic Approach to Multi-disciplinary Aircraft Analysis and Design

Presented at the 36th Aerospace Sciences Meeting and Exhibit, Reno, NV, January 12-15, 1998.

Life Cycle Assessment of Potential Biojet Fuel Production in the United States

The objective of this paper is to reveal to what degree biobased jet fuels (biojet) can reduce greenhouse gas (GHG) emissions from the U.S. aviation sector. A model of the supply and demand chain of biojet involving farmers, biorefineries, airlines, and policymakers is developed by considering factors that drive the decisions of actors (i.e., decision-makers and stakeholders) in the life cycle stages. Two kinds of feedstock are considered: oil-producing feedstock (i.e., camelina and algae) and lignocellulosic biomass (i.e., corn stover, switchgrass, and short rotation woody crops). By factoring in farmer/feedstock producer and biorefinery profitability requirements and risk attitudes, land availability and suitability, as well as a time delay and technological learning factor, a more realistic estimate of the level of biojet supply and emissions reduction can be developed under different oil price assumptions. Factors that drive biojet GHG emissions and unit production costs from each feedstock are identified and quantified. Overall, this study finds that at likely adoption rates biojet alone would not be sufficient to achieve the aviation emissions reduction target. In 2050, under high oil price scenario assumption, GHG emissions can be reduced to a level ranging from 55 to 92%, with a median value of 74%, compared to the 2005 baseline level.

Uncertainty Modeling and Management in Multidisciplinary Analysis and Synthesis

Presented at the 38th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, January 10-13, 2000.

Network-Theoretic Approach for Analyzing Connectivity in Air Transportation Networks

Research reported in this paper is motivated by the need to better understand the structure of connectivity in air transportation networks.Theaim istoinvestigateanalysismodelsandtechniquesfrom modernnetworktheoryas a framework to provide both characterization of network structure and a useful systems analysis approach to derive implications from both local and global topology characteristics. Recent developments in network theory establish meanstoquantifytopological structureinamannerthatmayindicateexpectedperformanceandrobustness.Inthis paper, a mathematical footing from network theory is introduced for examining transport networks in the U.S. domestic air transportation system. Using data for the 2004 travel year, the structure of the transport network (service routes between airports) and several subnetworks is exposed in terms of degree distribution, and the importance of airportsis assessed through several networkmeasures. Useful implications are drawn from measures andfurther analysis that directly maps these measures to system performance is presented. The general approachis found to merit further investigation as part of a larger, more comprehensive, and design-oriented systems analysis framework for air transportation.

A probabilistic approach for examining aircraft concept feasibility and viability

Abstract A novel approach to assessing aircraft system feasibility and viability is presented, with special emphasis on modeling and estimating the impact of new technologies. The approach is an integral part of an overall stochastic, life-cycle design process under development by the authors, which is to address the new measure for system value: affordability . Stochastic methods are proposed since the design process is immersed in ambiguity and uncertainty, both of which vary with time as knowledge increases about the system behavior. The specific task addressed in this paper of examining system feasibility and viability is encapsulated in the five steps of the Concept Feasibility Assessment approach. The rationale and technical foundations of each step are explained, and the approach is compared to more traditional, deterministic means for examining a design space and evaluating technology impacts. Finally, the techniques are implemented on a supersonic transport design problem to highlight the power of the approach on a problem of significant interest to the international aerospace community. Several innovative avenues for viewing the design and technology spaces are employed in assessing first feasibility and then viability for the problem.

Exploring the Dimensions of Systems of Innovation Analysis: A System of Systems Framework

The objective of this paper is to propose an analysis framework based on the System of Systems approach to overcome existing methodological problems in System of Innovation studies. The concept of System of Innovation has been an important focus of innovation policy studies over the last decade. These studies have concentrated on structuring theoretical frameworks to assess the determinants of innovation processes using systems analysis principles. Despite about 20 years of research, System of Innovation has yet to become a theoretical framework. This paper reviews the relevant literature in an attempt to identify the challenges that System of Innovation studies face in structuring theoretical frameworks. The primary reason for the challenges appears to be that Systems of Innovation have been analyzed as monolithic systems when, in reality, Systems of Innovation are Systems of Systems, which have different features than monolithic systems. Different dimensions of assessment of System of Systems analysis are therefore required in System of Innovation studies. Three dimensions of System of Innovation analysis (definition, abstraction, and modeling) are introduced here to provide an analysis framework for Systems of Innovation studies. The proposed system-of-systems-based analysis framework (called Innovation System of Systems) would resolve the methodological challenges that System of Innovation studies are confronting in developing theoretical frameworks. Thus, it is capable of being tested by other researchers in the area of Systems of Innovation to advance the state of knowledge.

Viable Designs Through a Joint Probabilistic Estimation Technique

Presented at the 4th World Aviation Congress and Exposition, San Francisco, CA, October 19-21, 1999.

Taxonomy to Guide Systems-of-Systems Decision-Making in Air Transportation Problems

a system of systems, many engineering methods and tools used to design and analyze large-scale, but monolithic, systems do not appear to work for systems of systems. This paper presents a three-axis taxonomy that can guide design method development and analysis of alternatives for aeronautical systems of systems. Based on this perspective, two experiments in applying the methods are presented for system-of-systems problems that involve aircraft and/or air transportation. Nomenclature AR = aspect ratio T=W = thrust-to-weight ratio W=S = wing loading