1. FEMCI Workshop 2005
Poster Session
LaRC/Exploration Concepts Branch 3D Finite Element Based Structures Tools
May 4-5, 2005
Goddard Space Flight Center
Zoran N. Martinovic NASA/LaRC
Jeffrey A. Cerro NASA/LaRC
Lloyd B. Eldred / Swales Aerospace
Philip Su / Raytheon Corp.

2. Objective: FEMCI Workshop 2005
Poster Session
Objective:
• To quickly create coarse vehicle 3D models
which are subject to typical structural design loads
• To estimate Level 2 primary structure weights during
conceptual design phase
- Level 0 weight estimates are based on historical data
- Level 1 weight estimates are line model subject to shear,
moment and axial force estimates
- Level 2 coarse FEM structural weight estimates
- Level 3 detailed FEM structural weight estimates
• To do structural trade studies

3. FEMCI Workshop 2005 Tool Outline Poster Session
Semi-automated iterative procedure for structural weight estimation and trade studies of new vehicle design concepts
• JAVA - Object Oriented process control language (original
process was wrapped in Phoenix Integration/Model Center)
• UGS / I-DEAS - CAD/CAE
• Collier Research / HyperSizer - Structural component sizing
• LOFT - Swales code to quickly create FEMs with property assignment regions defined
• EXCEL Solver - utility used for balancing of flight loads
• HSLOAD - Swales code to automate the HyperSizer design process
• Multidisciplinary input from CONSIZ (Subsystem weights), POST (Trajectory), CBAERO (Aero)

4. FEMCI Workshop 2005 Process Outline
Poster Session
Process Outline
POST Flight Profile with Accelerations & CBAERO generated Aero-forces
Vehicle Geometry and Weights
CONSIZ
LOFT Generated Mesh
INPUT
Geometry
INPUT
Gs & Fs
INPUT
Lump Mass
INPUT
FE Mesh
Loaded I-DEAS FE Model
I-DEAS FE Model
Load Balancing
EXCEL Solver
[M], [K]
Finite elements
organized in
groups/Panels
I T E R A T I O N L O O P
Running loads [Nx, Ny, Nxy ……]
New [K] &
Struct. [M]
HSLoad / HYPERSIZER Model
Plans for the future
Apply a semi-automated iterative procedure for structural weight estimation of new launch vehicle designs within CoHAVE environment for Level 2 design.
Compare the estimated weight with the Level 1 predictions.
Panel sizing in
HYPERSIZER
Assign:
Panel/beam Concept
Material
Limits on design variables
Failure Criteria
Zoran N. Martinovic/VAB/NASA LaRC/ June 2004

5. Geometry, packaging and sub-system weights received …..
FEMCI Workshop 2005
Poster Session
Geometry, packaging and sub-system weights received …..

6. Automatic Finite Element Mesh Generation For Aerospace Vehicles
FEMCI Workshop 2005
Poster Session
LOFT
Automatic Finite Element Mesh Generation For Aerospace Vehicles
• Use supplied Geometric Dimensions
• Generate Panels, Frames, Beams/Bars
for a full or partial vehicle
• Mark each element with User Specified
component names and coordinates
• Attach to commercial codes for FEA
and sizing
• Post process sizing results

7. Extrudes between arbitrary cross sections
FEMCI Workshop 2005
Poster Session
LOFT
Extrudes between arbitrary cross sections
Builds objects using panels, beams and bars
Merges objects to form a single FE model
Portable C code with Text Input
# ISAT Reference Mach 3.4 TSTO Vehicle
# Our nose
object dome BST Nose
curve1 sc
c1_xscale
c1_yscale
length -36
taper para
nodes_circ 21
nodes_axial 20
droop line
zdroop 8

8. Example of LOFT input file
FEMCI Workshop 2005
Poster Session
Desired forms are programmed …
Example of LOFT input file

9. Create Physical and Material Property Names to mark
FEMCI Workshop 2005
Poster Session
Property Assignments
Create Physical and Material Property Names to mark
Engineering components
Allows easy application of sizing parameters to different
Vehicle sections and easy post processing
LOX FW Dome
LOX Longeron
LOX Ring Frame
LOX Barrel
LOX Aft Dome
Meaningful names allow different construction approaches across the vehicle

10. Proof of Concept: WingSizer
FEMCI Workshop 2005
Poster Session
High fidelity tool to estimate wing structural weights
Generates detailed FE mesh
Calls FEA solver
Calls and controls sizing program
Postprocesses results
Proof of Concept: WingSizer
If only wing needs
to be studied, user may
use a standalone
program: Wingsizer ….

11. FEMCI Workshop 2005
Poster Session
WingSizer Analysis
Mesh
FEA
Size

12. FEMCI Workshop 2005 Process Highlights Poster Session Geometry Model
LOFT FEM Mesh

13. LOFT generated model is imported to UGS/I-DEAS for static analysis …
FEMCI Workshop 2005
Poster Session
Nose
cone
LOFT generated model is imported
to UGS/I-DEAS for static analysis …
Nose gear
bulkhead
Fin
Nose skirt
Wing center section
LOX tank
Inter-tank
Wing
Aft transition skirt
Forward LH tank
Model consists of
shells (panels)
and …
Fwd. transition
skirt
Aft LH tank
Bay fwd. bulkhead
Payload bay
Thrust structure
Bay aft bulkhead
Thrust structure bulkhead
Zoran N. Martinovic/VAB/NASA LaRC/ June 2004

14. … beams (frames and longerones)
FEMCI Workshop 2005
Poster Session
Nose Skirt
… beams (frames and longerones)
LOX Tank
Bay
Inter tank
FWD LH Tank
Transition Skirts
Longerones
around
circumference
AFT LH tank
Thrust

15. FEMCI Workshop 2005 Poster Session
Sub-system masses are mapped and lumped to FEM …
CONSIZ output file
Mapping template file
Mapping file into FEM XB XE
Component mapping x
fofx mapping

16. FEMCI Workshop 2005 Poster Session Individual Unit Loads are applied
and model analyzed for each of them …
1 psi Unit load
… propellant loads are applied
for each flight point and model
analyzed for each of them …

17. FEMCI Workshop 2005 Scaling of unit Loads And Loads and Balancing
Poster Session
Scaling of unit Loads
And
Loads and Balancing
Aero
1 psi Unit load
Sum of balanced forces and moment
Objective function: Pitch moment = 0
Scaling factors
Constraints on axial and normal force, and other flight constraints
I-DEAS/EXCEL/Text/JAVA
Inertia
FzORB
FxORB
FzSRB
FxSRB
Unit load sets are scaled, combined and balanced to create actual design loads.
Inputs are vehicle accelerations from design conditions (POST)
and aero loads mapped from CBAERO (or user input fields in FEA)

18. to the FEM in UGS / I-DEAS and static analysis is done …
FEMCI Workshop 2005
Poster Session
Propellant Tanks with Head pressure and
Ullage pressure
Booster Wing Lift and Flap Lift
Orbiter ½
Wing Drag
Booster ½ Nose Drag
Orbiter ½
Fin Drag
Balanced flight loads
are applied
to the FEM in UGS / I-DEAS and
static analysis is done …
Booster ½ Wing Drag
Booster ½ Fin Drag az
Orbiter ½ Nose Drag ax T W
Booster Body Lift

19. FEMCI Workshop 2005 Poster Session
Model, subdivided into panels and beams,
is imported to
Collier Research / HyperSizer …
… with internal
running loads …
… and sized for minimum
weight with different
structural concepts and
materials

20. FEMCI Workshop 2005 Poster Session
Model with new structural mass and stiffness is imported
to UGS /I-DEAS and process iterates until converges.

21. FEMCI Workshop 2005 Summary Poster Session Complex vehicle designs
multiple body
ground/ascent/entry loads
Integral panels
Variety of panel and beam designs
metallic
composite
Frame Stiffened
Semi-monocoque shell

22. FEMCI Workshop 2005 Poster Session
Reference configurations in development
Atlas 5 Heavy
Space Shuttle
Shuttle Derived
Lifting Body
RLV – TSTO and OSP
RLV - SSTO

23. FEMCI Workshop 2005 Poster Session
Other applications under considerations
Launch vehicle payload fairings
Capsules