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

Economic Analysis of Strategies to Combat HLB in Florida Citrus

citrus greening, huanglongbing, asian citrus psyllid, Crop Production/Industries, Resource /Energy Economics and Policy,

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

Comparative Usability Study of Two Space Logistics Analysis Tools

Future space exploration missions and campaigns will require sophisticated tools to help plan and analyze logistics. To encourage their use, space logistics tools must be usable: a design concept encompassing terms such as efficiency, effectiveness, and satisfaction. This paper presents a usability study of two such tools: SpaceNet, a discrete event simulation tool and a comparable spreadsheet-based tool. The study follows a randomized orthogonal design having within-subjects evaluation of the two tools with 12 volunteer subjects (eight subjects with space backgrounds, four without). Each subject completed two sessions of testing, each with a 30-45 minute tutorial and a two-part space exploration scenario. The first part tests the creation a model to verify a simple uncrewed mission to lunar orbit. The second part tests the evaluation of an existing model to improve the effectiveness of a crewed mission to the lunar surface. The subjects completed a questionnaire after each session and a semi-structured interview following the second session. The study results indicate that the SpaceNet tool is more efficient for portions of the model creation task including modeling multi-burn transports and the spreadsheet tool is more effective for the model evaluation task. Qualitative evaluation indicates subjects liked the graphical nature and error-detection of the SpaceNet tool, but felt it took too long to edit information and appeared as a “black box.” Subjects liked the ability to view the entire model state within the spreadsheet tool, however were concerned with limited dynamic state feedback and underlying modeling assumptions. Future tools should combine the best features, including allowing modification of the entire model from a single interface, providing visibility of underlying logic, and integrated graphical and error-checking feedback.United States. Dept. of DefenseUnited States. Air Force Office of Scientific ResearchAmerican Society for Engineering Education. National Defense Science and Engineering Graduate Fellowship32 CFR 168aSamsung Fellowshi

Matrix Methods for Optimal Manifesting of Multinode Space Exploration Systems

http://www1.aiaa.org/content.cfm?pageid=318, Presented at the AIAA Space 2010 Conference and ExhibitionAnaheim, CA, 30 August–2 September 2010.This paper presents matrix-based methods for determining optimal cargo manifests for space exploration. An exploration system is defined as a sequence of in-space and on-surface transports between multiple nodes coupled with demands for resources. The goal is to maximize value and robustness of exploration while satisfying logistical demands and physical constraints at all times. To reduce problem complexity, demands are abstracted to a single class of resources, and one metric (e.g., mass or volume) governs capacity limits. Matrices represent cargo carried by transports, cargo used to satisfy demands, and cargo transferred to other transports. A system of equations enforces flow conservation, demand satisfaction, and capacity constraints. Exploration system feasibility is evaluated by determining if a solution exists to a linear program or network-flow problem. Manifests are optimized subject to an objective function using linear or nonlinear programming techniques. In addition to modeling the manifesting problem, a few metrics such as the transport criticality index are formulated to enable analysis and interpretation. The proposed matrix manifest modeling methods are demonstrated with a notional lunar exploration system composed of 32 transports, including eight cargo and nine crewed landings at an outpost at the lunar south pole and several surface excursions to Malapert Crater and Schrödinger Basin. It is found that carry-along and prepositioning logistics strategies yield different manifesting solutions in which transport criticality varies. For the lunar scenario, transport criticality is larger for a prepositioning strategy (mean value of 3.02), as compared with an alternative carry-along case (mean value of 1.99)

Process-oriented evaluation of user interactions in integrated system analysis tools

When computer-based tools are used for analysis of complex systems, the design of user interactions and interfaces becomes an essential part of development that determines the overall quality. The objective of this study is to investigate the processes and results of user interactions with integrated analysis tools to synthesize design implications for future tool development. In this study, two space exploration logistics tools are compared in a controlled user experiment. Through a comparative usability analysis, this study evaluated user performance and perception to provide design implications for future integrated analysis tools. For a comprehensive evaluation, multiple methods were used for data collection, including observation, questionnaire and interview. In addition to a result-oriented performance analysis, a process-oriented approach was used for analyzing patterns in user behaviors and errors. Results are presented with reference to the related features embedded in the interfaces of the two tools. Based on the comparative results, synthesized design insights for hierarchical structure, model transparency, automation, and visualization and feedback are discussed for integrated analysis tools in general.American Society for Engineering Education. National Defense Science and Engineering Graduate Fellowshi

Endocide-Induced Abnormal Growth Forms of Invasive Giant Salvinia (Salvinia molesta)

Giant salvinia (Salvinia molesta) is one of the most noxious invasive species in the world. The fern is known to have primary, secondary, and tertiary growth forms, which are also commonly hypothesized as growth stages. The identification of these forms is primarily based on the size and folding status of the floating leaves. However, we identified 12 forms in the greenhouse and the field. Our experiments showed that the folding of floating leaves is a reversible trait dependent on water access. The floating leaves quickly fold in response to water shortage, reducing water loss and needs, decreasing growth, and avoiding trichome damage. The leaves re-open to allow trichomes repel water and enhance growth when having adequate water supply. Larger secondary or tertiary forms do not produce small-leaf primary forms without high intensity stress. These results do not support the hypothesis that three growth forms represent sequential growth stages. The abnormal small-leaf forms are the result of endocide-induced autotoxicity and some of them never grow into other forms. The development of abnormal forms and reversible leaf folding strategy in response to high stress along with rapid asexual reproduction are major adaptive traits contributing to the invasiveness of S. molesta

Achieving sustainable irrigation water withdrawals: global impacts on food security and land use

Unsustainable water use challenges the capacity of water resources to ensure food security and continued growth of the economy. Adaptation policies targeting future water security can easily overlook its interaction with other sustainability metrics and unanticipated local responses to the larger-scale policy interventions. Using a global partial equilibrium grid-resolving model SIMPLE-G, and coupling it with the global Water Balance Model, we simulate the consequences of reducing unsustainable irrigation for food security, land use change, and terrestrial carbon. A variety of future (2050) scenarios are considered that interact irrigation productivity with two policy interventions— inter-basin water transfers and international commodity market integration. We find that pursuing sustainable irrigation may erode other development and environmental goals due to higher food prices and cropland expansion. This results in over 800 000 more undernourished people and 0.87 GtC additional emissions. Faster total factor productivity growth in irrigated sectors will encourage more aggressive irrigation water use in the basins where irrigation vulnerability is expected to be reduced by inter-basin water transfer. By allowing for a systematic comparison of these alternative adaptations to future irrigation vulnerability, the global gridded modeling approach offers unique insights into the multiscale nature of the water scarcity challenge

A flexible, modular approach to integrated space exploration campaign logistics modeling, simulation, and analysis

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 126-127).A space logistics modeling framework to support space exploration to remote environments is the target of research within the MIT Space Logistics Project. This thesis presents a revised and expanded framework providing capabilities to analyze a new set of explorations using a generalized resource flow through a time-expanded network to satisfy exploration demands. The framework is both flexible to model a wide range of destinations using mixed levels of fidelity and modular to enable future expansion through interfaces. The SpaceNet software tool implements the space logistics modeling framework, providing integrated modeling and simulation capabilities for quantitative space exploration campaign analysis. Discrete event simulation identifies logistical infeasibilities and provides quantitative measures of exploration effectiveness to guide trade studies or other campaign analyses. SpaceNet 2.5, a Java executable with an extensive graphical user interface, has been publicly released under an open source license. Four case studies are presented as examples of the modeling framework applied to relevant exploration campaigns. A resupply of the International Space Station from 2010-2015 includes 77 flights of seven different vehicles from six launch sites to investigate the supply capacity under existing resupply strategies. A near-Earth asteroid exploration details a two crew, 14-day tele-operated mission at 1999- AO10 to establish the feasibility requirements of using modified Constellation vehicle architectures. A lunar outpost exploration models the buildup of infrastructure and surface excursions leading to continuous human presence over 21 missions and seven years. Finally, a Mars surface exploration models the ten launches and in-space nuclear thermal rocket propulsion required to send a crew of four to the surface of Mars for a 531-day exploration. Finally, a usability experiment is presented to demonstrate the usability and efficiency of the SpaceNet tool as compared to independent analysis methods. Seven test subjects were tested, five using SpaceNet and two control subjects using spreadsheet-based methods, to analyze and establish the feasibility of a near-Earth object mission. The median SpaceNet subject required 35 minutes to complete the analysis, compared to a median of 113 minutes for the control subjects.by Paul Thomas Grogan.S.M

Multi-stakeholder Interactive Simulation for Federated Satellite Systems

Federated satellite systems (FSS) are a new class of space-based systems which emphasize a distributed architecture. New information exchanging functions among FSS members enable data transportation, storage, and processing as on-orbit services. As a system-of-systems, however there are significant technical and social barriers to designing a FSS. To mitigate these challenges, this paper develops a multi-stakeholder interactive simulation for use in future design activities. An FSS simulation interface is defined using the High Level Architecture to include orbital and surface assets and associated transmitters, receivers, and signals for communication. Sample simulators (federates) using World Wind and Orekit open source libraries are applied in a prototype simulation (federation). The application case studies a conceptual FSS using the International Space Station (ISS) as a service platform to serve Earth-observing customers in sun-synchronous orbits (SSO). Results identify emergent effects between FSS members including favorable ISS power conditions and potential service bottlenecks to serving SSO customers