# Presentation: 514178

- Nonlinear Analysis of the ST5 Magnetometer Boom
- Wayne Chen/Code 542          NASA/GSFC

## 	Agenda

- Problem Description
- Linear Versus Nonlinear Analysis
- Typical Model
- Trial and Error, Part 1
- Trial and Error, Part 2
- Trial and Error, Part 3
- Refining the Design
- Latest Model
- Latest Results
- Current Status
- Conclusions / Lessons Learned

## 	Problem Description

- Boom mounted magnetometer is one of the primary instruments on ST5
- Mission consists of a three S/C constellation to test nanosatellite technologies
- Overall S/C dimensions ~ 18 in wide and ~ 10 in high
- Overall S/C weight ~ 50 lb

## 	Problem Description (continued)

- Because of postbuckling behavior, regular linear statics solution sequences not adequate

## 	 Linear Versus Nonlinear Analysis

- Linear analysis
- Comprises bulk of the work done at GSFC
- Useful for analysis of deployed boom (normal modes, thermal distortion, etc)
- Nonlinear analysis
- Minimal GSFC heritage, though capability has existed in various analysis codes
- Only recently has nonlinear analysis been used for thin membranes, MEMS, and postbuckling
- Analysis of the boom has been marked by steady progress through a lot of trial and error

## 	Typical Model

- Main items of interest are torque capability of joint and tape stresses
- Variables include material, radius of tapes, and size of windows

- Tube

- Tapes

- One [45] ply of 0.005” T300

## 	Trial and Error, Part 1

- Early runs did not take into account contact between the tapes and used rigid elements (RBE2) at each end to enforce a rotation
- Problem due to lack of contact between tapes is obvious
- Behavior of end moment after snap-thru does not seem correct
- Run time of 2.40 hrs

## 	Trial and Error, Part 2

- Contact between the tapes added and used rigid elements (RBE2) at each end to enforce a rotation
- Contact between tapes more correctly modeled
- Behavior of end moment after snap-thru still does not seem correct
- Run time of 9.50 hrs

## 	Trial and Error, Part 3

- Contact between the tapes retained and rigid elements (RBE2) at each end replaced with massless aluminum plate elements to enforce a rotation
- Contact between tapes and behavior of end moment after snap-thru both seem correct and clean
- Run time of 3.35 hrs
- Important result was that the steady-state torque was too low

## 	Refining the Design

- Because torques from integral boom designs using one to several plies of composite were not high enough, investigated other alternatives
- Went from integral boom design to assembled boom design
- Tube sections still made of composite
- Tape sections made of Be Cu strips bolted to tube sections

## 	Latest Model

- One 0.006” Be Cu tape

- Ti 6Al-4V shim

- Four [0] plies of 0.005” T300

## 	Latest Results

## 	Latest Results (continued)

- Run time of 6.64 hrs
- Important result was that the steady-state torque was increased by quite a bit (up to ~ 1.4 in-lb)
- Be Cu tapes stacked to nominally double steady-state torque (because of additional complexity and excessive CPU time, did not attempt to run; verifying by testing)

- Two stacked 0.006” Be Cu tapes

## 	Current Status

- Individual boom joints as well as full-length boom in fabrication
- Torque testing of individual joints to begin shortly followed by G-negated deployment tests of full-up boom mounted to a S/C mock-up

## 	Conclusions / Lessons Learned

- Significant progress made in performing and understanding the nonlinear analyses of the boom since the last FEMCI workshop
- Doing trade studies of the different variables in the problem not very efficient because of large CPU times needed for each run
- Future analysis to support test program as needed