Design Engineering in Virtual Environments

The current Space Shuttle Orbital Maneuvering System (OMS) and the related Reaction Control System (RCS) make use of hydrazine as a propellant. Hydrazine, while high in energy content, is both corrosive and poisonous. As a result, its use in the OMS/RCS dictates that extreme caution be used in both the initial charging of the systems before launch and in their safetying after landing. Not only does the use of hydrazine increase the risk for those preparing and maintaining the Space Shuttle, but the procedures required for personnel safety during these processes add significant time to the preparation of each Space Shuttle for launch. As a result, the Space Shuttle Upgrade Board approved the design of a new OMS/RCS utilizing a non-toxic propellant. At the same time, this engineering design effort was recognized as an ideal opportunity to assess the overall maintainability of the OMS/RCS and to incorporate, where possible, design and vehicle integration features that would significantly reduce the personnel and time requirements for processing these systems between flights.

In an effort to reduce the overall engineering design time and costs, a partnership between the Propulsion Division and the Automation, Robotics, and Simulation Division of the NASA/Johnson Space Center (JSC) was formed to adapt and implement virtual environment technologies to reduce the length and cost of the engineering design process. At the heart of this effort was the use of real-time, 3D graphics to allow engineering teams to visualize the complex systems under development and to rapidly explore alternative design options.

Figure 1. A portion of the Space Shuttle with one of the OMS pods made transparent.

In addition, the virtual environments used for this purpose incorporated accurate human models to assess the visibility and accessibility of system elements that required routine inspection, removal, and/or replacement. Moreover, in the interest of improving the overall maintainability of the new systems, teams from NASA/Marshall Space Flight Center and NASA/Kennedy Space Center (KSC) participated materially in the design process, especially in design reviews intended to achieve the maximum possible quality in the finished design.

Figure 2. EAI Transom Jack human figure models were used to assess how many technicians were required to handle an OMS access panel.

Technologies developed and integrated by the Virtual Environments Research Institute of the University of Houston were employed to provide for high performance, 3D visualizations for the engineering design on platforms that ranged from the engineer’s desktop computer to a fully immersive CAVE. The EAI Transom Jack human model was integrated into this software environment to permit evaluation of inspection and access capabilities by technical staff over a range of human variability in height and arm length. Finally, with support from the Intelligent Synthesis Environment teams from both NASA/JSC and NASA/KSC, two or more display/interaction systems could be connected via existing communication channels to permit teams in different locations to be simultaneously involved in both the design and design review processes. The use of collaborative virtual environments was intended to achieve a significant reduction in the time and travel costs normally associated with the traditional engineering design process and a major improvement in the maintainability of the new systems.

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