WSC 2005 Final Abstracts

Toward Effective Depot Transformation: Leveraging Simulation to Enhance Transition Planning
Perakath Benjamin and Michael Graul (Knowledge Based Systems Inc), Michael Painter (knowledge Based Systems Inc) and Frank Boydstun (Oklahoma Air Logistics Center)

Abstract:
The goal of depot transformation is variability elimination over the production life-cycle. Forced to “ride the bike while we fix it,” the depot must transform the current batch and queue production style to a lean, cellular paradigm. Major challenges include transforming the infrastructure, work force, facilities, and supply chain. Further, unlike manufacturing production where the “work content” in a production item has been engineered from the ground up, work content for a repair item is highly variable and creates a ripple effect across the production system. This paper describes depot-MRO transformation according to a series of carefully designed transitions that mitigate variability and provide the modeling needs and requirements that, if met, would enable effective modeling and analysis of MRO production scenarios, providing engineers with a Transformation Design Assistant [TDA] for designing and testing production control strategies. TDA components are currently employed at OC-ALC, NASA-KSC, and within UH-60 MRO programs.

A Strategy for Autogeneration of Space Shuttle Ground Processing Simulation Models for Project Makespan Estimation
Michael G. Madden, Roberta Wyrick, and Dale E. O'Neill (United Space Alliance)

Abstract:
Space Shuttle Processing is a complicated and highly variable project. The planning and scheduling problem, categorized as a Resource Constrained – Stochastic Project Scheduling Problem (RC-SPSP), has a great deal of variability in the Orbiter Processing Facility (OPF) process flow from one flight to the next. Simulation Modeling is a useful tool in estimation of the makespan of the overall process. However, simulation requires a model to be developed, which itself is a labor and time consuming effort. With such a dynamic process, often the model would potentially be out of synchronization with the actual process, limiting the applicability of the simulation answers in solving the actual estimation problem. Integration of TEAMS model enabling software with our existing schedule program software is the basis of our solution. This paper explains the approach used to develop an auto-generated simulation model from planning and schedule efforts and available data.

A Discrete Event Simulation Model for Assembling the International Space Station
Grant R. Cates (NASA) and Mansooreh Mollaghasemi (University of Central Florida)

Abstract:
In late 2002 and early 2003, a discrete event simulation (DES) model was used to help NASA assess the viability of achieving a politically important goal. The goal was to complete the assembly of the International Space Station through the milestone known as United States Core Complete by February 19th, 2004. The analysis provided by the DES model was subsequently shown to be consistent with NASA’s official assessments regarding the completion date for U.S. Core Complete. The success of this DES model has led to further improvements in modeling NASA’s project to assemble the International Space Station.

Modeling and Parameter Estimation of Spacecraft Fuel Slosh Mode
Keith Schlee, James Ristow, and Sathya Gangadharan (Embry-Riddle Aeronautical University), Jim Sudermann and Charles Walker (NASA) and Carl Hubert (Hubert Astronautics)

Abstract:
The nutation (wobble) of a spinning spacecraft in the presence of energy dissipation is a well-known problem in dynamics and is of particular concern for space missions. Its rate of growth is characterized by the Nutation Time Constant (NTC). For analytical prediction of the NTC this fuel slosh is often modeled using simple mechanical analogs such as pendulums or rigid rotors coupled to the spacecraft. Identifying model parameter values which adequately represent the sloshing dynamics is the most important step in obtaining an accurate NTC estimate. Currently, the identification of the model parameters is a laborious trial-and-error process in which the equations of motion for the mechanical analog are hand-derived, evaluated, and their results are compared with the experimental results. The current research is an effort to automate the process of identifying the parameters of the slosh model using a MATLAB/SimMechanics based computer simulation of the experimental setup.

Estimating the Effects of Stress During Operational Conditions
Jon French (Embry Riddle Aeronautical University) and Jeff Miller (Micro Analysis and Design, Inc)

Abstract:
The Physiological Stress Index (PSI) was developed to provide a rational means for estimating the physiological and behavioral impact of exposure to physical stressors, in this case extreme temperatures and fatigue related to insufficient sleep. Stress can be life threatening and certainly threatens mission effectiveness. It is often derived from combinations of sources such as overheating and lack of sleep, particularly on individuals involved in physically demanding activities such as shipboard firefighting. The PSI was used as a performance modifying adjunct to existing discrete event simulation models designed to estimate shipboard manning requirements given various operational scenarios. Additionally, the PSI was used to estimate the most effective work rest cycles and recovery time required before selected crewmembers could be returned to duties involving significant levels of physical exertion.

Using Simulation for Launch Team Training and Evaluation
Cary J. Peaden (NASA)

Abstract:
This paper describes some of the history and uses of simulation systems and processes for the National Aeronautics and Space Administration’s (NASA’s) training and evaluation of launch, mission control, and mission management teams. It documents some of the types of simulations that are used at Kennedy Space Center (KSC) today. It provides an initial baseline and some recommendations for further research into simulation for launch team training and evaluation in the near future. A theme of this paper is that the use of simulation for the training and evaluation of launch teams is very important, and NASA should learn from and expand on these types of simulations especially as it prepares to develop new launch vehicles and processes under the Exploration program.

Distributed Web-based Expert System for Launch Operations
Jorge Bardina (NASA) and Rajkumar Thirumalainambi (SAIC)

Abstract:
The simulation and modeling of launch operations is based on a representation of the organization of the operations suitable to experiment of the physical, procedural, software, hardware and psychological aspects of space flight operations. The virtual test bed consists of a weather expert system to advice on the effect of weather to the launch operations. It also simulates toxic gas dispersion model, and the risk impact on human health. Since all modeling and simulation is based on the internet, it could reduce the cost of operations of launch and range safety by conducting extensive research before a particular launch. Each model has an independent decision making module to derive the best decision for launch.

Usability Study of the Virtual Test Bed and Distributed Simulation
Jeffrey W. Dawson, Ping Cheng, and Yanshen Zhu (University of Central Florida)

Abstract:
Improving the usability of a Distributed Simulation System (DSS) test bed is the focus of this paper. An introduction to the field of usability is given, followed by a discussion of the characteristics of DSSs. Then the usability of DSSs is considered. The Virtual Test Bed (VTB), a sample DSS we have improved the usability of, is described. The methodology used to improve the VTB’s usability is given. With the goal of improving usability for end users, prototyping of a graphical user interface is discussed; both software and paper prototypes are considered. Lessons learned provide insights into problems we encountered. Research on important aspects of DSSs that affect usability is reflected in a table that summarizes key issues. Our anticipated future research in this area is also discussed.

Supporting the Vision for Space with Discrete Event Simulation
Grant R. Cates (NASA) and Mansooreh Mollaghasemi (University of Central Florida)

Abstract:
On January 14, 2004 President George W. Bush announced a new Vision for Space Exploration. This vision called for NASA to complete the assembly of the International Space Station by 2010 and retire the Space Shuttle immediately thereafter. A discrete event simulation (DES) based tool has been built to assess the viability of NASA accomplishing all of the Space Shuttle missions required to assemble the Space Station by the end of the decade. This paper describes this DES tool i.e. the Manifest Assessment Simulation Tool (MAST).

Using System Dynamics for Safety and Risk Management in Complex Engineering Systems
Nicolas Dulac, Nancy Leveson, David Zipkin, Stephen Friedenthal, and Joel Cutcher-Gershenfeld (Massachusetts Institute of Technology)

Abstract:
This paper presents a new approach to modeling and analyzing organizational culture, particularly safety culture. We have been experimentally applying it to the NASA manned space program as part of our goal to create a powerful new approach to risk management in complex systems. We describe the approach and give sample results of its applications to understand the factors involved in the Columbia accident and to perform a risk analysis of the new Independent Technical Authority (ITA) structure for NASA, which was introduced to improve safety-related decision-making.

Health Systems: A Dynamic System—benefits From System Dynamics
Patrick Koelling and Michael J. Schwandt (Virginia Polytechnic Institute and State University)

Abstract:
Operations researchers, industrial engineers, and simulation analysts have applied their knowledge and skills to the health care system for a long time. This complex system needs their help today more than ever. The ever-growing need to understand and improve system performance challenges researchers to apply all the tools at their disposal. One of these tools that is getting increased attention is system thinking, with its application partner system dynamics. This paper presents a glimpse into the system thinking world as it is currently applied in the health care arena, and provides some thoughts on new directions for application. While there are other very useful tools, such as optimization and discrete-event simulation, that are effectively used for health care application, they should not always be the tools of choice, and suggestions are made for when system dynamics may be more appropriate for a particular application.

A Spatio Temporal Simulation Model for Evaluating Delinquency and Crime Policies
Sergio E. Quijada and Juan F. Arcas (Military Polytechnique Academy), Cristian Renner (University of the Andes) and Luis Rabelo (University of Central Florida)

Abstract:
System Dynamics as an arena building technique has been useful for a variety of disciplines; however, it has limitations when we want to show a geographical representation of the models under study. We propose a methodology which allows the use of census information from a city to feed a Geographic Information System (GIS), based on layer vectors. The objects located at coordinates X.Y.Z become the entry parameters for the simulation implemented into System Dynamics. The simulation outputs close an analysis cycle, by mean of new layers which are represented in the GIS. Consequently, the simulation provides feedback for vectorial representation. The technique was successfully used to simulate the best strategies to reduce criminality rates in a large city.