1997-07-01

Solutions for the Exchange of Models and Results of Analysis and Tests in the Space Domain - STEP-TAS and STEP-NRF 972448

This paper presents the approach, the status and the future of two companion open standards for electronic exchange and archival of space engineering data:
  1. 1)
    STEP-NRF - Network-model Results Format -
    a discipline-independent protocol for the definitions of analysis, test or operation cases/models and the bulk results produced by running such cases/models. A generic network-model formulation is used to represent the different elements of an analysis model, a test article or an operational product and where applicable their environment. The results are stored as valued properties for particular network-model components for a particular state during a run. Properties can be of scalar, vector or tensor type. Special care is taken to ensure efficient storage of sparse data structures.
  2. 2)
    STEP-TAS - Thermal Analysis for Space -
    a protocol for the definitions of space missions and models used in thermal analysis.
    It comprises definitions of orbit, space thermal environment, material property environment and kinematic articulation. The model definition comprises surface geometry (including boolean constructive surface geometry), thermal-radiative properties and meshing, kinematic structure, materials and physical properties. STEP-TAS is a pure extension of STEP-NRF. It adds - or specialises - the specific constructs that are needed for space thermal analysis applications.
ESA initiated the development of both standards which follow the development methodology of the international STEP standard. STEP stands for the STandard for the Exchange of Product model data and is the casual name for ISO 10303. The actual work was performed by a consortium lead by Fokker Space (of The Netherlands), and with further partners: Association GOSET, ESPRI Concept, Epsilon Ingénierie (all of France) and European Gas Turbines' Mechanical Engineering Centre (of the UK).
For both standards the following deliverables are produced:
  • A so-called Application Protocol, which specifies the information that can be exchanged in a formal, computer-interpretable way;
  • A software library package with C and FORTRAN application programming interfaces, which facilitate the development of STEP-NRF and STEP-TAS import/export facilities for CAx applications.
And, in addition for STEP-TAS only:
• The first industrial release of the ESARAD/STEP-TAS converter.
Although the development of these STEP-based standards and software turned out to be a complicated undertaking and required a significant effort by a dedicated team over a period lasting more than three years, the effort is justified by the rewards it brings:
High quality, robust standards which are embedded in the framework of the ISO STEP standard for product model data exchange;
  • Implementation support through the availability of robust STEP development toolkits;
  • The possibility of connecting the specialist space thermal engineering tools - in a manageable and cost-effective way - to the major commercial CAx packages through the growing number of STEP-based product data exchange options in such packages.

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