# Presentation: 658985

## STEP Protocol Development and Converter Implementation Processes at ESA

- Hans Peter de Koning - ESA/ESTEC - The Netherlands
- Hans-Peter.de.Koning@esa.int
- Sandrine Fagot - Simulog - France
- Sandrine.Fagot@simulog.fr
- STEP for Aerospace Workshop, NASA-JPL, 16-19 January 2001

**Notes:**
<Simulog est une société fondée à l’initiative de l’INRIA (INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET AUTOMATIQUE) il y a plus de 10 ans, en 1984.
La définition de la mission de l’entreprise  est basée sur l’objectif initial de ses initiateurs: être un pont entre l’industrie et la recherche publique.

La mission de l’entreprise comporte deux points qui reflètent notre stratégie mais aussi le marché sur lequel Simulog évolue:
L’objectif numéro 1 est de fournir une gamme de prestation complète: Simulog doit intégrer les solutions proposées dans l’environnement industriel préexistant de ses clients.
Cette connaissance approfondie des besoins du client , de son métier et de son environnement permet d’atteindre plusieurs objectifs positifs: 1. la mise en confiance du client, qui facilite le dialogue lors de la phase de spécification des besoins (meilleure compréhension des besoins) et lors de l’apport des solutions nouvelles (plus grande facilité à obtenir l’adhésion du client). 2. la fidélisation du client, qui permet d'accroître l’efficacité et la rentabilité des études au fur et à mesure.
L’objectif numéro 2 consiste à s’adapter aux nouvelles technologies pour offrir au client une solution industrielle à un problème ne pouvant être traité par les méthodes classiques.
>

## Topics

- What is Europe doing w.r.t. standardisation of product data exchange & archival for space applications?
- How did we develop STEP based solutions?
- What successes?
- What lessons learned?
- Road ahead

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## What is Europe doing?

- ECSS E-10-07 WG “Exchange of Product Data”
- European Cooperation for Space Standardization
- High level ‘meta-standard’ like NASA-STD-2817
- www.estec.esa.int/ecss
- ftp://ftp.estec.esa.nl/pub/ecss-e-10-07-wg/index.html
- Specific standards
- STEP-TAS “Thermal Analysis for Space” (ESA)
- STEP-NRF “Network-model Results Format” (ESA)
- STEP-PRP “Propulsion” (CNES)            (CNES = French Space Agency)
- Active role AP232 “Technical Data Package” (CNES + Industry)
- Active role AP233 “System Engineering” (Aerospace Industry)

- w.r.t. standardisation of product data exchange & archival for space applications

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Focus of this presentation

- Development process of STEP-TAS and STEP-NRF
- Achievements, some metrics and lessons learned
- Objective: To provide useful feedback for others contemplating to develop similar ‘niche’/specific purpose standards

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Main characteristics NRF (1)Network-model Results Format

- Targets engineering-discipline independent exchange of bulk results data from analysis, test or operation
- Representation of engineering objects by network models consisting of discrete nodes and node-relationships
- Hierarchical tree of network models / submodels
- Definition of properties
- Quantitative, descriptive and functional properties
- Scalar, vector and tensor property values
- Property values only at discrete locations / discrete states
- Full annotation of  analysis / test / operation context
- Campaign, case, phase, run
- Facility/tool, environment, date and time, organisation, person, ...

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Main characteristics NRF (2)NRF dataspace

- abscissa_property

- model_component
- (model, node, node_relationship)

- state

- property_class

- Each gridpoint in the 3D dataspace is a property value
- Each can be scalar, vector, tensor
- Data model and implementation designed to handle  sparsely populated dataspace efficiently

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Main characteristics NRF (3)Proposed NRF/HDF architecture

- STEP-NRF
- protocol
- (discipline- independent)

- NRF
- Dictionary
- Structural

- NRF
- Dictionary
- Thermal

- NRF
- Dictionary
- Electrical

- NRF
- Dictionary
- ...

- STEP-NRF SDAI
- programming library

- HDF 5
- programming library

- NRF – HDF mapping

- HDF5
- binary
- results file

- User Application
- (Reading or Writing
- Results Data)

- AP203
- STEP file

- AP209
- STEP file
- (future)

- reference to product (-part),
- shape, location

- reference to FEM / FE

- COTS or PD
- Data Analysis / Visualisation Application with HDF i/f
- (also via WWW)

- discipline-specific dictionaries

- HDF5 = Hierachical Data Format v5
- - Public domain from NCSA
- - Efficient portable binary storage format
- - Full C, Fortran, Java libraries on >10 platforms
- - Standard for all NASA EOS missions
-   and some ESA earth observation
- - Info/downloads at hdf.ncsa.uiuc.edu
- - Many COTS / PD tools with HDF interface

- HDF5 as an efficient alternative for Part21
- for large amounts of similar data

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Main characteristics TAS (1)Thermal Analysis for Space

- Self contained, complete Application Protocol
- AAM, ARM, Mapping Table, AIM, Express-G
- Conforms to TC184/SC4 methods and guidelines
- Geometry defined conform AP203 CC4 surface model
- Thermal-radiative model faces added as associated features
- Including possibility to support hierarchical submodel tree
- Associated notional thickness, surface material and bulk material
- Thermo-optical, thermo-physical properties for named material
- Concept of material property environment (Part 45)
- Kinematic model conform STEP Part 105
- For articulated rigid bodies (e.g. rotating solar arrays, ...)

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Main characteristics TAS (2)

- Space mission aspects
- orbit arc (Keplerian and discrete ephemeris)
- space co-ordinate system, celestial bodies
- orientation, general and named pointing, spinning, linear rotation rates
- space thermal environment, including constant or lat/long dependent albedo / planetshine tables
- Boolean construction surfaces available for advanced tools
- STEP-TAS CC1 Abstract Test Suite
- conform STEP Part 3xx series
- test suite used in validation of TAS processors

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Main characteristics TAS (3)STEP-TAS Conformance Classes

- thermal-radiative model
- with basic geometry

- kinematic
- model

- constructive
- geometry

- space mission
- aspects

- CC-1

- CC-2

- CC-3

- CC-4

- CC-5

- CC-6

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- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Brief history TAS and NRF developments

**Brief history TAS and NRF developments**

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Challenge

- Find an effective development process
- Within modest budget constraints
- TAS for a ‘niche’ market
- Between 20 to ~300 real users per space thermal analysis tool
- Make sure that user requirements are well captured
- Ensure implementations can be, and are, validated
- Facilitate efficient and maintainable converters
- Attempt to obtain global consensus
- Ensure robustness and ease of use for end-users

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Incremental development scheme

- Define / Refine / Extend Protocol
- (ARM, AIM, Express)

- Develop / Upgrade
- Libraries

- Develop / Upgrade
- Converters
- & Test Suites

- Validate
- Converters
- with Test Suites

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Stable Team with Clear Roles

- Simulog (F, software engineering services)
- lead since 1998, implementation libraries and some converters
- Fokker Space (NL, space subsystems contractor)
- initial lead, user requirements, ARM, ATS
- GOSET (F, STEP standardisation experts)
- mapping table, AIM, EXPRESS/p21 verification
- Epsilon Ingénierie (F, thermal analysis services)
- check user requirements, converter implementation
- ALSTOM Power (UK, thermal tool vendor)
- converter implementation, distribution to end-user
- CNES (F, French Space Agency)
- Review requirements and model, generation of test suites

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Approach to Developing with STEP

- Be as precise as possible on semantics
- Regular feedback between protocol editor and implementors
- Minimise ARM - AIM mapping need as much as possible
- Use IR contructs where possible direct in ARM
- Automate generation of library APIs as much as possible
- Directly from EXPRESS model
- Design for simplicity, implementability and testability
- E.g. do not use EXPRESS ANDOR
- Use a high level programming interface to build converters
- Use an SDAI toolkit for low level interface

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## STEP-TAS High Level Libraries Toolkit

- High-level API to support efficient converter development
- Use ARM constructs - close to thermal developer’s data model
- Hide STEP complexity
- Full set of reading / writing functions in ANSI-C and F77
- Associated documentation, examples and test suite
- BagheraView (CNES) included to perform independent visual inspection and model reporting on PC/Windows
- Distribute toolkit at nominal cost to attract tool vendors

- API =
- Application Programming Interface

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## BagheraView Screenshot

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Benefits of High Level Libraries Approach

- Already ported and tested with target compilers
- PC/Windows, Sun/Solaris, HP/HP-UX, Compaq/Tru64, SGI/Irix
- Enables to jumpstart converter implementation
- Reduces converter validation / verification effort
- All converters share reading/writing interface
- implementation mismatch is minimised
- increased reliability
- Extensibility at affordable cost
- e.g. to add HDF or XML encoding

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## STEP-TAS Converter Architecture

**STEP-TAS**
**EXPRESS**
**data model**

**STEP-TAS**
**physical**
**file**
**(ISO 10303-21)**

**Thermal Analysis Tool**
**(ESARAD, THERMICA, TRASYS, ...)**

**STEP-TAS High Level Libraries**
**C and Fortran API**
**(Simulog, France)**

**SDAI C Library (ISO 10303-24)**
**ST-Developer**
**(STEP Tools Inc., USA)**

**STEP-TAS Converter Architecture**

**Native**
**Tool**
**Format**

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Successes ...

- Full implementation of converters at reasonable cost
- ESARAD/STEP-TAS-CC1 since mid 1999
- Thermica/STEP-TAS-CC1 since Dec 2000
- Broad awareness and (prototype) implementation in US
- JPL STEP-TAS demonstrator in 5 US thermal tools
- Full bi-directional implementation STEP-TAS-CC1 in Thermal Desktop 3.3Beta (Cullimore & Ring sponsored by NASA-LaRC)
- Reached almost 100% of space thermal tool vendors
- Very close to robust and reliable quality exchange for STEP-TAS-CC1 in production tools

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## ... Problems with STEP

- Bulkiness and incomprehensibility for humans of AIM
- Makes validation cumbersome and costly
- Causes large overheads
- Additional in-core storage
- Addition interface layer in library
- Part21 files much larger than really really necessary
- ARM to AIM mapping is not computer interpretable
- EXPRESS-X was not available for TAS: a lot of handwork for high level library interface mapping
- Conformance checking / Abstract Test Suite (Parts 3x)
- Very cumbersome and costly to develop and maintain
- Not well designed for automation of regression testing

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Lessons Learned

- Iterative, incremental development necessary
- Can not get things right in one go ...
- High level programming library very useful
- Greatly reduces converter development effort
- Speeds up standard penetration & increases exchange reliability
- Chosen API close to old SET-ATS interface needs reconsideration
- Continuous resource / funding level is needed
- To meet vendor expectations by providing timely support and library updates resolving SPRs
- Communication must be improved
- Start a ‘STEP-TAS implementors forum’ ?

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Metrics

- STEP-TAS took ~5 years from conception to CC1 industrial converter release
- Up to now funded with roughly 1 million Euro / USD
- Excluding US converter developments
- Appears to be a quite good price/performance ratio
- Approximately 20 different people have worked on different parts of STEP-TAS and STEP-NRF

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Why was STEP-TAS not yet submitted as an ISO TC184/SC4 work item? 

- Valid question
- Started as a European effort to follow up SET-ATS
- Limited resources prevented us to bear the additional effort of formal ISO standardisation - no added value yet
- With the good co-operation with NASA in place,nearly 100% of the space thermal tool vendors in the world were reached
- However it is agreed that a formal way of publishing and maintaining the standard is now needed imminently

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Road Ahead (1)

- Web-based collaboration on further development
- ftp://ftp.estec.esa.nl/step-tas/index.html as a start
- Publication of protocol, SPR list, test suite
- FTP distribution of STEP-TAS toolkit releases
- E-mail tech support
- Take European / US collaboration to a next stage
- Action ESA and NASA together with Simulog
- Clarify/establish intellectual property rights and support

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Road Ahead (2)

- Currently trade-off for ‘Return on Investment’ next 5 years
- Appropriate level of formal publishing (ISO?, ECSS?, NASA?)
- Select AIM or ARM based exchange?
- Upgrade high level API to support all STEP-TAS constructs
- e.g. submodelling, non-uniform meshing and node numbering
- Upgrade libraries to resolve all reported issues (SPRs)
- Upgrade converter options
- Consistently support length unit selection / conversion
- Meta data entry

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Road Ahead (3)

- TRASYS/STEP-TAS-CC1 bi-directional converter
- Stand-alone tool by Simulog on ESA funding
- Will be made available at nominal cost or preferrably free
- Upgrade BagheraView capabilities
- By Simulog sponsored by CNES
- PATRAN/STEP-TAS-CC1 interface
- By MSC sponsored by NASA-LaRC
- Continue NRF developments
- HDF5 binding (co-operation with EDF, NCSA and others)
- Assess links with Engineering Analysis modules, ISO 10303-50
- Pilot web-based remote consultation of structural test results

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001

## Acknowledgements

- STEP-TAS and STEP-NRF were developed under ESA contract by an industrial consortium, consisting of:
- Simulog (F, prime)
- Fokker Space (NL)
- Association GOSET (F)
- Epsilon Ingénierie (F)
- Alstom Power (UK)
- and supported by CNES (F)
- Special thanks to Georg Siebes (NASA-JPL) who is and has been the driving force for the development and acceptance of STEP-TAS in the US
- Also acknowledgements to Ruth Amundsen (NASA-LaRC)for actively promoting STEP-TAS implementations

- STEP for Aerospace Workshop - NASA-JPL

- 16-19 Jan 2001