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

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

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

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

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

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)

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

City.Net IES: A sustainability-oriented energy decision support system

A city's energy system processes, as well as the interactions of the energy system with other systems in a city are imperative in creating a comprehensive energy decision support system due to the interdependencies between critical segments of the system. City.Net is a sustainability-oriented decision support system that represents the energy, water, waste, transportation and building systems in a city while taking into consideration the integration and interdependencies that exist between these systems. This paper, which is focused on the integrated energy infrastructure system of a sustainable city, builds on the previous work which employs hierarchical decomposition and multi-domain formulation for the design of complex sustainable systems. The City.Net energy system encompasses the generation, transmission, distribution and consumption of energy in different forms, in several domains and at diverse scales in a city. Also, the interactions of the energy system with other aforementioned systems are incorporated in City.Net. The result is a scalable and flexible energy decision support system which can be simulated and used as a sustainability-analysis tool, encompassing environmental, social and economic sustainability

Silk fibroin scaffolds with muscle-like elasticity support in vitro differentiation of human skeletal muscle cells

Human adult skeletal muscle has a limited ability to regenerate after injury and therapeutic options for volumetric muscle loss are few. Technologies to enhance regeneration of tissues generally rely upon bioscaffolds to mimic aspects of the tissue extracellular matrix (ECM). In the present study, silk fibroins from four Lepidoptera (silkworm) species engineered into three-dimensional scaffolds were examined for their ability to support the differentiation of primary human skeletal muscle myoblasts. Human skeletal muscle myoblasts (HSMMs) adhered, spread and deposited extensive ECM on all the scaffolds, but immunofluorescence and quantitative polymerase chain reaction analysis of gene expression revealed that myotube formation occurred differently on the various scaffolds. Bombyx mori fibroin scaffolds supported formation of long, well-aligned myotubes, whereas on Antheraea mylitta fibroin scaffolds the myotubes were thicker and shorter. Myotubes were oriented in two perpendicular layers on Antheraea assamensis scaffolds, and scaffolds of Philosamia/Samia ricini (S. ricini) fibroin poorly supported myotube formation. These differences were not caused by fibroin composition per se, as HSMMs adhered to, proliferated on and formed striated myotubes on all four fibroins presented as two-dimensional fibroin films. The Young's modulus of A. mylitta and B. mori scaffolds mimicked that of normal skeletal muscle, but A. assamensis and S. ricini scaffolds were more flexible. The present study demonstrates that although myoblasts deposit matrix onto fibroin scaffolds and create a permissive environment for cell proliferation, a scaffold elasticity resembling that of normal muscle is required for optimal myotube length, alignment, and maturation

Plant traits poorly predict winner and loser shrub species in a warming tundra biome

Climate change is leading to species redistributions. In the tundra biome, shrubs are generally expanding, but not all tundra shrub species will benefit from warming. Winner and loser species, and the characteristics that may determine success or failure, have not yet been fully identified. Here, we investigate whether past abundance changes, current range sizes and projected range shifts derived from species distribution models are related to plant trait values and intraspecific trait variation. We combined 17,921 trait records with observed past and modelled future distributions from 62 tundra shrub species across three continents. We found that species with greater variation in seed mass and specific leaf area had larger projected range shifts, and projected winner species had greater seed mass values. However, trait values and variation were not consistently related to current and projected ranges, nor to past abundance change. Overall, our findings indicate that abundance change and range shifts will not lead to directional modifications in shrub trait composition, since winner and loser species share relatively similar trait spaces