Integrated Electrical System Testing and Modeling for Risk Mitigation 2008-01-2897

International Space Station (ISS) Payload Engineering Integration (PEI) organization adopted the advanced computation and simulation technology to develop integrated electrical system models based on the test data of various sub-units. This system model was used end-to-end to mitigate system risk for the integrated Space Shuttle Pre-launch and Landing configurations. The Space Shuttle carries the Multi-Purpose Logistics Module (MPLM), a pressurize transportation carrier, and the Laboratory Freezer for ISS, a freezer rack for storage and transport of science experiments from/to the ISS, is carried inside the MPLM. An end-to-end electrical system model for Space Shuttle Pre-Launch and Landing configurations, including the MPLM and Freezer, provided vital information for integrated electrical testing and to assess Mission success. The Pre-Launch and Landing configurations have different power supplies and cables to provide the power for the MPLM and the Freezer. The integrated system including Space Shuttle, MPLM and Freezer had never been tested. This approach significantly improved test planning and execution. Developing high-fidelity models from conventional test data will reduce the number of tests, lower cost and enhance data quality while maintaining comprehensive test coverage.

PEI utilizes ANSOFT Simplorer software for modeling and simulating the impedance, steady-state voltage, surge current, voltage transients, and ripple spectrum characteristics of the entire power bus based on the various sub-unit test data. Simplorer provides dynamic system modeling, simulation and data analysis for large-scale system integration. Modeling is valuable at the initial design stage since it enables experimentation, exploration and development without expensive and time-consuming modifications. However, with the complexity of the system interactions among all subunits provided by various developers and suppliers, it is difficult to model an integrated system or verify that a system model meets all the requirements of its design specifications. In addition, the changes to system requirements demand frequent redesigns and reimplementation of many systems and sub-unit components.

The benefits provided by modeling from conventional test data are: (1) Relatively low cost, (2) Identification of potential system integration problems early in the program, (3) Extrapolation of test data to verify system performance to cover the entire operating envelope, (4) Provide flexibility in development system integration modeling.

The modeling of an integrated system based on system and sub-unit test data enables organizations to predict and improve system performance and to conduct efficient trade studies of system architecture. This comprehensive model can then be used directly in standard downstream processes such as rapid prototyping and risk mitigation in the product life cycle. The detailed modeling from conventional test data will be discussed in the presentation.