# Presentation: 403846

## JWST Multi-Mega FE Model Studies

**Terry Fan/Swales Aerospace****Mark McGinnis/Swales Aerospace****Glenn Grassi/MSC.Software****John Johnston, PH. D./GSFC**
** **
**May 4 & May 5, 2005**

**FINITE ELEMENT MODELING CONTINUOUS IMPROVEMENT**
**FEMCI.GSFC.NASA.GOV**
**NASA Goddard Space Flight Center**
**Greenbelt, Maryland, USA**
**Mechanical Systems Analysis and Simulation Branch, Code 542**** **

## Objective & Summary 

**The objective of this study is to find an optimized computing solution **
- Enable Multi-mega model runs and,
- Shorten the iteration times to a reasonable time frame
**Summary**
- Benchmarking runs performed on several computer systems indicates that daily iteration is feasible
- Super-element can be used to alleviate the hardware demanding, however it might prolong the iteration time.
- Post processing of Mega-models may pose challenges. Well equipped computer will dramatically improve speed
- RAM
- CPU Speeds

## Introduction

**The James Webb Space Telescope (JWST) structure system is operated at 30 Kelvin with nanometer-level performance requirements. **
**The main structure of the JWST is made of composite tubular components with a near-zero axial CTE and significant transverse CTE. **
**The traditional so-called stick model composed of beam elements cannot capture the transverse CTE, adhesive, clips, gussets, and other effects, which preliminary analyses indicate will have an first-order impact on the prediction distortions.**
**8-noded brick elements were chosen to model the composite structures of JWST **
- To capture, transverse, through-the-thickness, and adhesive CTE effects
- 30 millions degrees of freedom FEM is expected

## Challenges & Issues

**These are the largest structural models run at GSFC to date and are pushing/exceeding the limits of our computational resources**
**Pre/post-processing cumbersome **
- e.g. 30 min. to load model & generate pictures (2) of 4 MDOF model in FEMAP w/ a 1.6 GHz, 1 G RAM, Dell M60 precision workstation
- Model loading time was reduced to 2 min. from 6 min. when RAM was increased to 2 GB compared
**Integrations of Subsystem FEMs**
- I/F definitions among subsystems
- Element types
- Coordinates
- Subsystems are modeled using MSC.Nastran and IDEAS
- Incompatibility issues caused by IDEAS converted Nastran model

## Challenges & Issues

**MSC/Nastran and Pre- & Post-processors**
- How to run the Multi-mega model efficiently in MSC/Nastran
- Super-element Analysis
- Modeling guidelines
- How to improve the pre- & post-processing time
- What pre- & post-processors to use (FEMAP & Patran)
- FEM mesh quality
**Hardwires Specifications**
- CPU architecture, i.e. parallel processing
- CPU speed
- RAM
- Disk Space & I/O configuration

## JWST Observatory Architecture

## JWST Telescope Architecture

_**Secondary Mirror Support Structure (SMSS) **_

_**Primary Mirror Segment Assemblies (PMSA) **_

_**PM BackPlane Assy (PMBA)**_

_**ISIM Enclosure (IEA)**_

_**Aft Optics Subsystem (A0S)**_

- Fixed tertiary mirror
- Fine steering mirror
- PM baffle/radiator

_**Secondary Mirror Assembly (SMA) **_

- Light-weighted, semi-rigid segments
- 18 modular units make up PM
- Hexapod rigid body actuation, one RoC actuator

- Supports 18 PMSAs, ISIM, IEC, Radiators, IOS, SMSS
- Torque Box BSF

_**Deployment Tower Subsystem (DTS)**_

## A PRELIMINARY 4 MDOF JWST FEM

**PMBA**

**ISIM**

- JWST system model
- Brick elements are used to model the tubular structure.
- Example shown is 4+ M DOFs model.

## MSC.Software Mega Models Benchmarking (1/2)

**Performed by MSC.Software **
**Three computing systems**
- Machine: Vesuvius
- speed: 900 MHzop sys: HP-UX B.11.22ram: 8 Gbcpus: 4 Mckinley cpus
- Machine: Sumatra - 4CPU - RAM=8Ggb
- Hewlett Packard 9000 MODEL 9000/800/N4000-55  HP-UX (64-bit) B.11.00
-  Machine: IA647
- Intel Itanium 2 /149  Linux 2.4.18-e.31smp
- Nastran Version 2005.0.3 BETA
- Residual Only - No Superelements
- TEMPD
- CPU=1
- SCR=YES
- Buffsize=65537

## MSC.Software Mega Models Benchmarking (2/2)