Mario Marin

System dynamics and agent-based simulations for workforce climate

Many factors currently influence the NASA Kennedy Space Center (KSC) workforce, including the drive for return to flight, a stated Shuttle Program end date of 2010, and the Vision for Space Exploration which calls for the development of a new launch vehicle. Additionally, external factors such as cost of living in Central Florida, availability of skilled technical hires, and unemployment rate affect the overall workforce climate. Managing human capital in a manner consistent with safety and mission success, and to strategically position the center to execute its future mission, it is necessary to understand how these different influencing factors work together to produce an overall workforce climate. We have been using system dynamics models to capture some of these factors. These models are also the starting point of agent-based models which can capture particular features not possible with the original system dynamics models. This paper introduces our simulation modeling efforts

Simulation modeling of space missions using the high level architecture

This paper discusses an environment being developed to model a mission of the Space Launch System (SLS) and the Multipurpose Crew Vehicle (MPCV) being launched from Kennedy Space Center (KSC) to the International Space Station (ISS). Several models representing different phases of the mission such as the ground operations processes, engineered systems, and range components such as failure tree, blast, gas dispersion, and debris modeling are explained. These models are built using different simulation paradigms such as continuous, system dynamics, discrete-event, and agent-based simulation modeling. The High Level Architecture (HLA) is the backbone of this distributed simulation. The different design decisions and the information fusion scheme of this unique environment are explained in detail for decision-making. This can also help in the development of exploration missions beyond the International Space Station.

Addressing complexity using distributed simulation: a case study in Spaceport modeling

As the size, complexity, and functionality of systems to model and simulate continue to increase, benefits such as interoperability and reusability enabled by distributed discrete event simulation are of interest, especially for distributed manufacturing and enterprise engineering. The high level architecture (HLA), a standard distributed simulation environment, is one technology that enables the interconnection of distributed model components. Many applications in industry are developed by a variety of commercial off-the-shelf (COTS) simulation tools, which require some form of gateway to integrate the models into the HLA component-based simulation. This paper summarizes a study conducted to integrate COTS simulation models using gateway tools and visualization of the system states running as part of other simulation models under HLA. The study focused on the prototype of a virtual engineering environment, called the Virtual Test Bed, designed to analyze operations of current and future space vehicles, spaceports, and ranges as a distributed simulation environment.

Supply chain and hybrid modeling: the Panama Canal operations and its salinity diffusion

This paper deals with the simulation modeling of the service supply chain and the salinity and its diffusion in the Panama Canal. An operational supply chain model was created using discrete-event simulation. Once complete, a component based on differential equations was added to the model to investigate the intrusion of salt and the resulting salinity diffusion into the lakes of the canal. This component was implemented in the AnyLogic simulation modeling environment by taking advantage of the concept of hybrid modeling that is embedded in AnyLogic.

Spaceport simulation models integration

The Virtual Test Bed (VTB) is a distributed simulation environment for spaceport modeling. Using the High-Level Architecture (HLA) and integration frameworks based on software agents and the eXtensible Modeling Language (XML), this environment presents the integration process and implementation of several models of the operations taking place at a National Space and Aeronautics Administration (NASA) spaceport, before, during and after a Space Shuttle launch. Having a distributed environment is a needed feature of the simulation system due to the nature of the models since the operations modeled can in many instances be based at different geographic locations. The following operations are modeled and integrated: weather operations, range operations, launch probability operations, control room operations, and space shuttle model hardware processes and operations.

A Distributed Environment for Spaceports

This paper describes the development of a distributed environment for spaceport simulation modeling. This distributed environment is the result of the applications of the High-Level Architecture (HLA) and integration frameworks based on software agents and XML. This distributed environment is called the Virtual Test Bed (VTB). A distributed environment is needed due to the nature of the different models needed to represent a spaceport. This paper provides two case studies: one related to the translation of a model from its native environment and the other one related to the integration of real-time weather.

Enterprise scheduling: hybrid and hierarchical issues

We build a hybrid discrete-continuous simulation model of the manufacturing enterprise system. This model consists of an overall system dynamics model of the manufacturing enterprise and connected to it are a number of discrete event simulations for selected operational and tactical functions. System dynamics modeling best fits the macroscopic nature of activities at the higher management levels while the discrete models best fit the microscopic nature of the operational and tactical levels. An advanced mechanism based on information theory is used for the integration of the different simulation modeling modalities. In addition, the impact of the decisions at the factory level in scheduling are analyzed at the management level. The different models of control are discussed.

Parallel discrete event simulation of space shuttle operations

This paper describes the application of parallel simulation techniques to represent structured functional parallelism present within the space shuttle operations flow, utilizing the synchronous parallel environment for emulation and discrete-event simulation (SPEEDES), an object-oriented multicomputing architecture. SPEEDES is a unified parallel simulation environment, which allocates events over multiple processors to get simulation speed up. Its optimistic processing capability minimizes simulation lag time behind wall clock time, or multiples of real-time. SPEEDES accommodates increases in processes complexity with additional parallel computing nodes to allow sharing of processing loads. This papers focuses on the whole process of translating a model of space shuttle operations flow represented in a process-driven approach to object oriented design, verification, validation, and implementation.

Multi resolution modeling

Multi-resolution modeling (MRM) includes many different approaches. It is very well known by the Distributed Simulation community that the High Level Architecture (HLA) is an architecture designed to facilitate interoperability and software reuse. Therefore, the unit of MRM is usually the federate. Multiresolution representation of entities consists in maintaining multiple and concurrent representations of entities. As such, several approaches may be used to manage the aggregation/disaggregation processes, according to the particular needs of the simulation exercised. However, we have found that there are many approaches presented in the literature. We have to weigh many considerations when comparing the different MRM approaches. This paper introduces the different approaches and provides an experiment using constructive simulation.

Modeling of complex scenarios using LVC simulation

Interoperation of simulation models is an important issue due to high level requirements of reusability, scalability, and eventually training effect. Achieving Live, Virtual and Constructive (LVC) simulation interoperability is a main goal and a major challenge for M&S community. High interoperability quality in LVC simulation environment is a technologically complex task, being affected by multiple factors, and the task is not yet satisfactorily characterized and studied. This research presents an experimental LVC simulation framework to model and simulate complex war fighting scenarios. Our experimental framework implementation discusses key issues for LVC interoperability encountered during our experimentation. A case study is presented to discuss LVC integration and interoperability challenges. Our experimental research aim is to contribute to the definition and design concepts of LVC simulation systems developments, technological considerations and adequate interoperability.