Mark E. McNelis and Vicente J. Suarez

Glenn Research Center, Cleveland, Ohio

Timothy L. Sullivan, Kim D. Otten, and James C. Akers

Analex Corporation, Brook Park, Ohio

Fluids and Combustion Facility: Fluids

Integrated Rack Modal Model Correlation

NASA/TM—2005-214056

December 2005

GRC–DEV–FCF–2005–002
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Mark E. McNelis and Vicente J. Suarez

Glenn Research Center, Cleveland, Ohio

Timothy L. Sullivan, Kim D. Otten, and James C. Akers

Analex Corporation, Brook Park, Ohio

Fluids and Combustion Facility: Fluids

Integrated Rack Modal Model Correlation

NASA/TM—2005-214056

December 2005

National Aeronautics and

Space Administration

Glenn Research Center

GRC–DEV–FCF–2005–002
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TABLE OF CONTENTS

1. Introduction ................................................................................................................ 1

1.1 Background........................................................................................................... 1 

1.2 Purpose of CIR Model Correlation ........................................................................ 3 

1.3 Applicable Documents .......................................................................................... 4 

2. Model Correlation....................................................................................................... 4 

2.1 Requirements........................................................................................................ 4 

2.2 Model Correlation Methodology ............................................................................ 5 

3. Test Hardware Configuration.................................................................................... 6

3.1 Hardware Mass and CG Summary ....................................................................... 7 

3.2 Rack Hardware Modifications ............................................................................... 8 

3.3 Mass Simulators ................................................................................................. 11 

3.4 Active Rack Isolation System (ARIS) .................................................................. 11 

4. FEM Model Description ........................................................................................... 12 

4.1 Rack Coordinate System .................................................................................... 13 

4.2 Rack Modal Test Fixture ..................................................................................... 13 

4.3 FEM Mass and CG Properties ............................................................................ 15 

5. Pre-Test Analysis..................................................................................................... 16 

6. Test Results.............................................................................................................. 24 

7. Model Correlation..................................................................................................... 33 

8. Conclusions.............................................................................................................. 42 

9. References................................................................................................................ 42

10. Acronym List ............................................................................................................ 43 

11. Appendices............................................................................................................... 44

Appendix A FIR Optics Bench with FSAP ....................................................................... 45 

Appendix B Air Thermal Control Unit (ATCU) ................................................................. 53 

Appendix C Rack Door.................................................................................................... 61 

Appendix D Lower Structure Assembly........................................................................... 69 

Appendix E FIR Rack Modal Instrumentation Plan........................................................... 77 

Appendix F FIR Rack Correlated Model Comparison of Frequency and CrossOrthogonality ..................................................................................................................... 91 

NASA/TM—2005-214056 iii

1. Introduction 

1.1 Background 

The Fluids and Combustion Facility (FCF – Figure 1) is a modular, multi-user, 

two-rack facility dedicated to combustion and fluids science in the US Laboratory 

Destiny on the International Space Station. FCF is a permanent facility that is 

capable of accommodating up to ten combustion and fluid science investigations 

per year. FCF research in combustion and fluid science supports NASA’s 

Exploration of Space Initiative for on-orbit fire suppression, fire safety, and space 

system fluids management. 

FIGURE 1 – FLUIDS AND COMBUSTION FACILITY

The Fluids Integrated Rack (FIR) is one of two racks in the FCF. The FIR major 

structural elements (Figure 2) include the International Standard Payload Rack 

(ISPR), Experiment Assembly (optics bench and combustion chamber), Air 

Thermal Control Unit (ATCU), Rack Door, Lower Structure Assembly 

(Input/Output Processor and Electrical Power Control Unit) and Active Rack 

Isolation System (ARIS). The load path through the rack structure is outlined in 

Figure 3. 

NASA/TM—2005-214056 1
Rack

Lower Structure 

Assembly

Rack 

Door

FIR Optics 

Bench

FIR Air Thermal Control Unit 

(top of rack)

FIGURE 2 – FLUIDS INTEGRATED RACK (FIR) 

FIGURE 3 – LOAD PATH DIAGRAM 

NASA/TM—2005-214056 2
1.2 Purpose of FIR Model Correlation 

The FIR modal survey was conducted to validate the load path predicted by the 

FIR finite element model (FEM). The rack FEM was provided by Boeing -

Houston; the FIR package FEMs and analytical integration into the rack was 

performed by ZIN Technologies. The modal survey is done by experimentally 

measuring the FIR frequencies and mode shapes. The FIR model was test 

correlated by updating the model to represent the test mode shapes. The 

correlated FIR model delivery is required by NASA JSC at Launch-10.5 months.

The test correlated FIR flight FEM is analytically integrated into the Shuttle for a 

coupled loads analysis of the launch configuration. The analysis frequency range 

of interest is 0-50 Hz. 

A coupled loads analysis is the analytical integration of the Shuttle with its cargo 

element, the Multi-Purpose Logistics Module (MPLM), in the Shuttle cargo bay 

(Figure 4). For each Shuttle launch configuration, a verification coupled loads 

analysis is performed to determine the loads in the cargo bay as part of the 

structural certification process (Figure 5). 

MPLM

Rack

Orbiter Y

X

Zo o

o

FIR

FIGURE 4 – ANALYTICAL INTEGRATION PROCESS FOR COUPLED LOADS ANALYSIS 

NASA/TM—2005-214056 3
• Preliminary Environmental Specifications

• Load Factors

• Preliminary Environmental Specifications

• Load Factors

• Design Coupled Loads

•MUF = 1.35

•Enveloping Technique

• Stress Analysis

• Minimum Margins of Safety

• Design Coupled Loads

•MUF = 1.35

•Enveloping Technique

• Stress Analysis

• Minimum Margins of Safety •Target Modes < 50 Hz •Target Modes < 50 Hz • Buckling Critical > 1.4 • Buckling Critical > 1.4

• Preliminary Design Review • Critical Design Review • Dynamic Testing

Modal Test

Sine Sweep

• Dynamic Testing

Modal Test

Sine Sweep

• Structural Strength Test

• No test required using FS=2.0

• Structural Strength Test

• No test required using FS=2.0

• Verified Dynamic 

and Stress Models

• Verified Dynamic 

and Stress Models • Verification Loads Cycle • Verification Loads Cycle • Final Stress Analysis

• Margins of Safety

• Final Stress Analysis

• Margins of Safety • Flight Certified Cargo Element • Flight Certified Cargo Element

• To NASA JSC • To NASA JSC • To NASA JSC • To NASA JSC

FIGURE 5 – STRUCTURAL CERTIFICATION PROCESS

1.3 Applicable Documents 

1. “Payload Verification Requirements,” NSTS 14046, Revision E, May 

2000.

2. “Rack to Mini Pressurized Logistics Module Interface Control 

Document,” SSP 41017, Part 1, Revision F, May 18, 2001.

3. “Rack to Mini Pressurized Logistics Module Interface Control 

Document,” SSP 41017, Part 2, Revision H, May 18, 2001.

4. “Payload Flight Equipment Requirements and Guidelines for SafetyCritical Structures,” SSP 52005, Revision C, Section 7.1 Verification 

Requirements for Dynamic Structural Models, December 18, 2002. 

5. “International Standard Payload Rack (ISPR) Structural Integrator’s 

Handbook,” SSP 57007, Revision A, October 31, 2001.

2. Model Correlation 

2.1 Requirements 

The math model verification requirements for FCF racks are defined in NSTS 

14046 and SSP 52005 (see 1.3 Applicable Documents). SSP 52005, Section 7.1 

defines that evidence for model correlation is provided through test based 

frequency and mode shape characterization. The correlation goal for each 

fundamental frequency is a frequency difference between model and test of less 

than +/- 5%. For higher order frequencies, the correlation goal is a frequency 

difference of less than +/- 10%. 

NASA/TM—2005-214056 4
Cross-orthogonality between the analytical and test mode shapes is evaluated 

based on the following calculation: 

The correlation goal for the diagonal values of the correlation matrix, [Cij], is a 

value greater than 0.9 for significant modes. For the off-diagonal terms, the 

correlation goal is a value of less than 0.1. 

2.2 Model Correlation Methodology 

The FIR model correlation methodology was based on modal testing and 

correlating each major structural assembly individually (Reference 1). This 

building block approach facilitates the model correlation process for the FIR. 

Previous testing by Boeing correlated the rack model in a configuration with 

various mass weighted horizontal shelves in the rack (Reference 2). The FCF 

rack structural configuration was different than the Boeing correlated rack 

configurations as the FCF racks have a vertical plate (optics bench) instead of 

horizontal shelves, creating a different load path in the rack. The final step in the 

correlation process was to modal test and model correlate the FIR. 

Model correlation for the major structural assemblies is summarized in the 

following appendices: 

Appendix A – FIR Optics Bench 

Appendix B – FIR ATCU 

Appendix C – Rack Door 

Appendix D – Lower Structure Assembly 

The Lower Structure Assembly model was not correlated as the test measured 

fundamental frequencies were greater than 100 Hz, outside the model correlation 

frequency range of interest (0-50 Hz). 

NASA/TM—2005-214056 5
3. Test Hardware Configuration 

FIR Ground Integration Unit (GIU) hardware was used for the FIR test 

configuration (Figure 6). The overall dimensions of the rack are given in Figure 7. 

The test rack was a modified 6-post International Standard Payload Rack (ISPR) 

made of carbon fiber composite material similar to the flight rack. The rack was 

supplied by Boeing. The FIR GIU hardware is a structural flight duplicate which 

will be used as an astronaut trainer and for troubleshooting on-orbit facility 

problems. The FIR test configuration did not include any wiring or harnessing, 

however, it did include the environmental control system plumbing. The Active 

Rack Isolation System (ARIS) was represented by a coldplate, hardback, and 

mass simulators for the major ARIS masses. 

FIGURE 6 – FLUIDS INTEGRATED RACK TEST CONFIGURATION

NASA/TM—2005-214056 6
Rack Origin

25.5 inches

77.5 inches

41.1 inches

Z

Y X

FIGURE 7 – RACK COORDINATE SYSTEM AND OVERALL DIMENSIONS

3.1 Hardware Mass and CG Summary 

The FIR test hardware weighs 1390.92 lbs and the FIR flight hardware 

configuration weighs 1471.03 lbs (Reference 3). The mass difference is 

80.11 lbs, representing a difference of 5.4%. A mass and CG summary of the 

test and flight rack hardware configurations are given in Table 1. The main 

difference between the test and flight hardware configurations is the test rack 

does not have wiring or harnessing. The CG properties between the FIR test and 

flight hardware are very comparable, as seen in Table 1. 

NASA/TM—2005-214056 7
Table 1 – FIR Hardware Mass and CG Summary 

Subsystems 

Weight 

(lbf) 

CGx 

(in) 

CGy 

(in) 

CGz 

(in) 

 ATCU 124.68 19.9 -12.9 69.2 

 Experiment Assembly 563.15 18.9 -8.3 41.2 

 Door 92.22 19.8 -27.9 43.7 

 Rack 305.76 19.3 -8.7 25.5 

 Lower Structure Assembly 

(Mass Simulator) 206.49 17.5 -12.6 15.1 

Tested FIR GIU 1390.92 18.9 -10.9 36.2 

FIR Flight 1471.03 18.6 -10.4 35.2 

3.2 Rack Hardware Modifications 

Test rack hardware modifications were made to reflect the flight rack structural 

changes. The modifications include removal of the rack center posts, 

replacement of pressure relief valve assemblies with closeout panels, installation 

of coldplate and hardback simulator at bottom of the rack, and removal of a blank 

Rack Utility Panel (RUP) and installation of a flight-like RUP and RUP extension. 

The rack modifications are shown in Figure 8. 

Structural attachment modifications were made to incorporate FCF hardware in 

the rack. The Lower Structure Assembly is attached to the rack using modified 

center-post attachment hardware at the bottom of the rack (Figure 9). 

NASA/TM—2005-214056 8
• Remove front and rear 

center posts

• Replace Pressure Relief 

Assemblies with closeout 

panels

• Remove blank rack utility 

panel and install RUP and 

RUP extension

• Install Hardback simulator 

at bottom of rack

A

B

A

B

C

C

D

D

FIR GIU

Install Coldplate and 

Hardback simulator at 

bottom of rack

Pressure Relief closeout panels RUP and RUP extension

Hardback mass simulator 

(looking down at bottom of rack)

RUP panel

B C

D

FIGURE 8 – RACK HARDWARE MODIFICATIONS

NASA/TM—2005-214056 9
FIR GIU

FIGURE 9 – RACK CENTER-POST STRUCTURAL ATTACHMENT MODIFICATION

NASA/TM—2005-214056 10
3.3 Mass Simulators 

The general criteria for using mass simulators in the FIR test configuration is 

based on providing mass representation for any components weighing greater 

than 5 lbs. For the FIR modal test the only mass simulators used were those 

associated with the Active Rack Isolation System. 

3.4 Active Rack Isolation System (ARIS) 

The FIR flight rack will be outfitted with the Active Rack Isolation System (ARIS). 

The ARIS components are shown in Figure 10. The purpose of ARIS is to isolate 

the FIR from ISS vibratory acceleration. For the FIR modal survey, mass 

simulators were used to represent the major ARIS masses. The components 

simulated and their masses are: 

• Three Remote Electronics Units (REU) 9.7 lb. ea 

• ARIS Controller 20.0 lb. 

• ARIS Actuator Driver 23.4 lb. 

The REUs are mounted on the ISPR intercostals with one on the upper 

intercostal and two on the lower intercostal. The ARIS structure in the lower part 

of the rack consists of a hardback on which is mounted a coldplate. The ARIS 

controller and actuator driver are mounted on the coldplate. 

Upper Intercostal REU

Lower Intercostal REU’s

ARIS Controller

ARIS Driver

FIGURE 10 – ARIS COMPONENTS

NASA/TM—2005-214056 11
4. FEM Model Description

The FIR modal test configuration finite element model (FEM) is shown in 

Figure 11. The finite element model was created using MSC/NASTRAN and has 

the following properties: 

M O D E L S U M M A R Y 

NUMBER OF GRID POINTS = 80313 

NUMBER OF CBAR ELEMENTS = 1023 

NUMBER OF CBUSH ELEMENTS = 4 

NUMBER OF CELAS1 ELEMENTS = 522 

NUMBER OF CHEXA ELEMENTS = 7613 

NUMBER OF CONM2 ELEMENTS = 123 

NUMBER OF CPENTA ELEMENTS = 12 

NUMBER OF CQUAD4 ELEMENTS = 53085 

NUMBER OF CQUADR ELEMENTS = 154 

NUMBER OF CTETRA ELEMENTS = 2932 

NUMBER OF CTRIA3 ELEMENTS = 7032 

NUMBER OF RBAR ELEMENTS = 81 

NUMBER OF RBE2 ELEMENTS = 1973 

NUMBER OF RBE3 ELEMENTS = 60 

NASA/TM—2005-214056 12
4.1 Rack Coordinate System 

The rack coordinate system for the finite element model and modal test is 

defined in Figure 7. The rack coordinate system is a local coordinate system 

invariant to the integration position of the rack into the MPLM. 

4.2 Rack Modal Test Fixture 

The rack modal test fixture is the structural hardware between the rack and the 

modal floor. The design intent for the rack fixture is to have the fundamental 

frequency ten times higher than the FIR fundamental frequency to prevent 

dynamic coupling between the FIR modes and the fixture. The fixture is a frame 

construction using welded tubular steel with 3/8” wall thickness. 

A modal test was conducted on the rack fixture to characterize the fundamental 

frequencies (Figure 12). The rack fixture finite element model was not correlated. 

Based on the fixture test results, the fixture stiffness was increased using 

bookend stiffeners to prevent deflection of the ends of the fixture. Figure 11 

illustrates the FEM with rack attachment to the fixture including bookend 

stiffeners. 

Rack Door

Rack

Rack Fixture

X Z

Y

FIGURE 11 – TEST CONFIGURATION FINITE ELEMENT MODEL (FEM) 

NASA/TM—2005-214056 13
Fixture

Z

Y

X

Mode Axis Freq (Hz)

1 X 196.6

2 X 201.1

3 Y 243.3

4 X 289.2

5 X 292.4

Fixture Modal Test Results

without Bookends

Bookend

Bookend

Bookend Fixture

Bookend

X

Y

FIGURE 12 – RACK MODAL TEST FIXTURE 

NASA/TM—2005-214056 14
4.3 FEM Mass and CG Properties 

A mass and CG summary is provided for the FIR test and flight finite element 

models (FEM) in Tables 2 and 3. The FIR test FEM weighs 1398.36 lbs and the 

FIR flight FEM weighs 1462.10 lbs. The mass difference between the two finite 

element models is 63.74 lbs, representing a difference of 4.4%. The CG 

properties between the test and flight rack are very comparable. 

Table 2 – FIR Test Finite Element Model Mass and CG Summary

Subsystems 

Weight 

(lbf) 

CGx 

(in) 

CGy 

(in) 

CGz 

(in) 

Ixx 

(lbm-in2) 

Iyy 

(lbm-in2) 

Izz 

(lbm-in2) 

 ATCU 120.52 20.0 -12.6 71.2 20.3 49.0 65.7 

 Experiment Assembly 553.32 18.5 -7.4 41.3 316.4 545.0 383.8 

 Door 108.08 19.7 -26.8 44.5 114.5 161.2 47.3 

 Rack 369.71 19.7 -7.8 24.4 767.9 859.5 323.1 

 Lower Structure Assembly 

(Mass Simulator) 139.64 20.2 -10.8 15.8 18.8 43.3 58.0 

 FIR Test FEM 1398.36 19.1 -9.6 36.1 2186.2 2539.3 1027.0 

Table 3 – FIR Flight Finite Element Model Mass and CG Summary

Subsystems 

Weight 

(lbf) 

CGx 

(in) 

CGy 

(in) 

CGz 

(in) 

Ixx 

(lbm-in2) 

Iyy 

(lbm-in2) 

Izz 

(lbm-in2) 

 ATCU 120.52 20.0 -12.6 71.2 20.3 49.0 65.8 

 Experiment Assembly 557.58 18.5 -7.5 41.4 322.0 551.3 388.8 

 Door 97.18 19.7 -26.9 45.1 107.4 145.6 38.5 

 Rack 435.47 19.4 -9.0 25.2 875.0 1028.0 411.3 

 Lower Structure Assembly 

(Mass Simulator) 139.64 20.2 -10.8 15.8 18.8 43.3 58.0 

 FIR Flight FEM 1462.10 19.1 -9.8 35.7 2296.3 2712.5 1101.9 

The mass difference between the FIR test hardware and the test FEM is 7.44 lbs, 

representing a 0.5% mass difference. The CG properties between the measured 

FIR test hardware and FEM are very comparable. 

The mass difference between the FIR flight hardware and the flight FEM is 

8.93 lbs, representing a 0.6% mass difference. The CG properties between the 

measured FIR flight hardware and FEM are very comparable. 

NASA/TM—2005-214056 15
5. Pre-Test Analysis 

Pre-test modal analysis was performed to identify target modes between 0-50 Hz 

and determine the accelerometer instrumentation layout. The methodology used 

to verify the finite element model is outlined in Figure 13. The general criterion 

used to define the primary target modes are modes with greater than 10% 

effective mass and a frequency less that 50 Hz. Secondary target modes are 

defined based on modes with less than 10% effective mass and frequencies 

greater than 50 Hz. Engineering judgment was also used to select target modes 

by visualizing animated mode shapes. 

Three modes were defined as target modes for the Fluids Integrated Rack (FIR) 

modal test. Two rack translational modes in the X, and Y axes were identified as 

primary target modes. A secondary target mode was identified as the FIR Z axis 

mode. 

The predicted X-axis FIR translational mode was 26.6 Hz, with an effective 

weight of 1229.2 lb. The predicted Y-axis FIR translational mode was 41.8 Hz, 

with an effective weight of 772.9 lbs. The predicted Z-axis FIR translational mode 

was 49.2 Hz, with an effective weight of 702.1 lb. Figures 14-16 illustrate the 

primary and secondary target modes for the FIR modal test. 

The target modes were compared between the FIR test FEM and TAM, with and 

without the test fixture, and flight FEM and flight ASET configurations to assure 

that the test configuration was representative of flight. These comparisons are 

summarized in Tables 4 and 5, and Figures 14–16 indicating that the test 

configuration modes are comparable to the flight modes. 

Selection of the accelerometer locations (NASTRAN A-SET) for the FIR modal 

test was based on a two-tiered approach using kinetic energy (choosing grid 

points from the finite element mode with high kinetic energy) and engineering 

judgment (visualizing the mode shape and placing instrumentation at high 

deformation locations). 

The criterion for selecting the final instrumentation was based on computing the 

cross-orthogonality between the test finite element model (FEM) and the Test 

Analysis Model (TAM - test finite element model including only the 

instrumentation locations). The cross-orthogonality between the test 

configuration FEM and the TAM are summarized in Table 6 and Figures 17-19. 

One hundred twenty six (126) degrees of freedom were used in the TAM. Crossorthogonality was greater than 90% for the primary target modes satisfying the 

criteria for instrumentation selection. The secondary target mode for the FIR Z 

axis had 93.8% cross-orthogonality. The final instrumentation plan is 

documented in Appendix E. 

NASA/TM—2005-214056 16
FIR flight 

dynamic FEM

Test configuration 

dynamic FEM

Modes

Effective Mass

Modes

Effective Mass

Assess change in target mode frequencies

Xortho Flight to Test with rigid BC

Component 

Test Results

Model 

Updates

Create test configuration by removing missing 

mass and stiffness. 

Determine mass simulators.

Test configuration 

dynamic FEM

Integrate test FIR FEM with fixture FEM

Modes

Effective Mass

Xortho Test FEM (rigid BC) to Test FEM (fixture)

Kinetic Energy

Visualize mode shapes

Select A-SET (accelerometer locations)

Select shaker and/or impact locations

Test configuration 

TAM

Xortho Test FEM (fixture) to TAM

Test Plan

Integrate/Instrument 

FIR Test Hardware

Conduct FIR 

Modal Test

Data Reduction 

Test Mode Shapes

Xortho TAM to Test

Update FIR Test FEM

Update FIR Flight Dynamic FEM

Deliver FIR Flight Dynamic FEM

To JSC-SWG 

Launch-10.5 months

FIGURE 13 – FIR MODEL VERIFICATION METHODOLOGY

NASA/TM—2005-214056 17
TABLE 4 – COMPARISON OF FLIGHT FEM (IN RIGID BOUNDARY CONDITIONS) AND TAM 

(IN RIGID BOUNDARY CONDITIONS) TARGET MODE FREQUENCY DIFFERENCE AND 

CROSS-ORTHOGONALITY

TABLE 5 – COMPARISON OF TEST FEM (IN RIGID BOUNDARY CONDITIONS) AND TEST 

FEM (IN FIXTURE) TARGET MODE FREQUENCY DIFFERENCE AND

CROSS-ORTHOGONALITY

TABLE 6 – COMPARISON OF TEST AND TAM TARGET MODE FREQUENCY DIFFERENCE 

AND CROSS-ORTHOGONALITY

TAM Delta Mode Shape

Mode 2 89 Freq Description

Freq (Hz) 27.1 42.4 50.2

Test FEM 1 26.6 0.931 0 0 -1.9% Rack X-axis Translation

w/Fixture 8 41.8 0 0.902 0 -1.4% Rack Y-axis Translation

9 49.2 0 0 -0.938 -2.0% Rack Z-axis Translation

Test FEM Rigid BC Delta Mode Shape

Mode 3 89 Freq Description

Freq (Hz) 30.6 45.6 52.4

Test FEM 1 26.6 0.878 0.100 0 -13.1% Rack X-axis Translation

w/Fixture 8 41.8 0 0.833 0.110 -8.3% Rack Y-axis Translation 

9 49.2 0 0 0.770 -6.1% Rack Z-axis Translation

FLIGHT ASET Rigid BC Delta Mode Shape

Mode 3 8 99 Freq Description

Freq (Hz) 30.3 47.5 57.1 57.1

TAM 3 31.2 100.26 0 0 0 3.0% Rack X-axis Translation

Rigid BC 8 46.3 0 0.931 0 0 -2.5% Rack Y-axis Translation

9 53.1 0 0 -0.713 0 -7.0% Rack Z-axis Translation

NASA/TM—2005-214056 18
Mode 3, 29.8 Hz

Effective Weight = 1238.6 lbs

Global X-axis rack translation

Flight FEM in Rigid BC

Mode 3, 30.6 Hz

Effective Weight = 931.1 lbs

Global X-axis rack translation

Test FEM in Rigid BC

Z

X

Z

X Mode 1, 26.6 Hz

Effective Weight = 1229.2 lbs

Global X-axis rack translation

Test FEM in Fixture

Z

X

FIGURE 14 – X-AXIS PRIMARY TARGET MODE

Mode 8, 46.7 Hz

Effective Weight = 529.2 lbs

Global Y-axis rack translation

Flight FEM in Rigid BC

Z

Y

Mode 8, 45.6 Hz

Effective Weight = 603.7 lbs

Global Y-axis rack translation

Test FEM in Rigid BC

Z

Y

Z X

Y

Z X

Y

Mode 8, 41.8 Hz

Effective Weight = 772.9 lbs

Global Y-axis rack translation

Test FEM in Fixture

Z

Y

Z X

Y

FIGURE 15 – Y-AXIS PRIMARY TARGET MODE

NASA/TM—2005-214056 19
FIGURE 16 – Z-AXIS SECONDARY TARGET MODE

Mode 12, 56.1 Hz

Effective Weight = 262.9 lbs

Global Z-axis rack translation

Flight FEM in Rigid BC

Z

Y

Z X

Y

Mode 9, 52.4 Hz

Effective Weight =127.3 lbs

Global Z-axis rack translation

Test FEM in Rigid BC

Z

Y

Z X

Y

Z X

Y

Z

Y

Mode 9, 49.2 Hz

Effective Weight = 702.1 lbs

Global Z-axis rack translation

Test FEM in Fixture

NASA/TM—2005-214056 20
Mode 2, 27.1 Hz

Effective Weight = 1218.2 lbs

Global X-axis rack translation

TAM in Fixture

(Back-Expanded)

Z

X Mode 1, 26.6 Hz

Effective Weight = 1229.2 lbs

Global X-axis rack translation

Test FEM in Fixture

Z

X

Cross-Orthogonality 93.1%

FIGURE 17 – COMPARISON OF TEST FEM TO TAM FOR THE X-AXIS TARGET MODE

Mode 8, 41.8 Hz

Effective Weight = 772.9 lbs

Global Y-axis rack translation

Test FEM in Fixture

Z

Y

Z X

Y

Mode 8, 42.4 Hz

Effective Weight = 567.9 lbs

Global Y-axis rack translation

TAM in Fixture (Back-Expanded)

Z X

Y

Z

Y

Cross-Orthogonality 90.2%

FIGURE 18 – COMPARISON OF TEST FEM TO TAM FOR THE Y-AXIS TARGET MODE

NASA/TM—2005-214056 21
Mode 9, 49.2 Hz

Effective Weight = 702.1 lbs

Global Z-axis rack translation

Test FEM in Fixture

Z

Y

Z X

Y

Cross-Orthogonality 93.8%

Mode 9, 50.3 Hz

Effective Weight = 616.6 lbs

Global Z-axis rack translation

Z X

Y

Z

Y

TAM in Fixture (Back-Expanded)

FIGURE 19 – COMPARISON OF TEST FEM TO TAM FOR THE Z-AXIS TARGET MODE

NASA/TM—2005-214056 22
Past experience in developing A-SETs for modal analysis has shown that it is 

important to include major masses. Therefore, the GRID points representing the 

3 REUs were included in the FIR A-set. 

When the model correlation effort was begun (see Sec. 7), there was difficulty in 

getting the cross orthogonality for the Y target mode above 75%. Based on 

viewing a comparison of the test mode shapes and the analytical mode shapes 

using the test display model, it was clear that there were significant differences in 

the lower part of the rack. Most obvious was the behavior of the lower intercostal 

with 2 REUs mounted to it. 

Because the poor cross orthogonality appeared to be associated with the ARIS 

hardware, a study was conducted to determine its influence on the results 

(Figure 20). When all the ARIS components were eliminated from the problem, 

the cross orthogonality of the Y mode increased from 70% to 92%. This change 

also had a beneficial effect on the X and Z modes. Then the effect of adding 

ARIS components back into the problem was determined. Optimum results were 

obtained when all ARIS components except the two REUs on the lower 

intercostal were included in the problem. 

The validity of removing the two lower REUs from the A-SET was determined by 

reviewing the frequency and effective mass with and without ARIS. Since there 

was no change in either of these two parameters when ARIS was removed from 

the A-SET, it was concluded the ARIS response was a local response and its 

removal did not affect the global modes of the rack. 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

X Mode Y Mode Z Mode

Cross-Orthogonality

All ARIS

No ARIS

Hardback and

Upper Intercostal

FIGURE 20 – EFFECT OF INCLUDING ARIS COMPONENTS ON FIR CROSS-ORTHOGONALITY 

(BEFORE OPTIMIZATION) 

NASA/TM—2005-214056 23
6. Test Results 

The Fluids Integrated Rack (FIR) modal test was conducted at the NASA Glenn 

Research Center Structural Dynamics Laboratory from May 16 – June 10, 2005. 

The test was performed using a fixed base interface between the test article and 

the modal floor. One-hundred twenty six (126) response accelerometers were 

used during the test. Four (4) load cells were mounted between the rack and 

fixture attachment locations to measure interface forces (Figure 21). Interface 

accelerometers were also used to monitor any relative motion between the fixture 

and rack. Minimal relative interface motion was observed, indicating that the 

fixture was not participating in the FIR target modes response. 

FIGURE 21 – LOAD CELLS

MB Dynamics (Modal 50) 50 lbrms shakers were used to excite the FIR. One 

shaker was used for X and Z-axis excitation. Two shakers were used in the Y 

and Z-axis to excite symmetric and anti-symmetric modes. Initially, impact tests 

were conducted to evaluate data quality, identify potential shaker locations, and 

to obtain preliminary modal data. Shaker locations were selected at hard points 

on the rack to optimally excite the target modes (Figures 23– 26). Multiple shaker 

excitation levels were used to address linearity of the FIR test configuration. Sine 

excitation levels included 1, 2, 5, 10, 15, and 20 lbpeak from 10-80 Hz. Burst 

random excitation levels included 1⁄2, 1, 2, 5, 10 and 15 lbrms. For the X-axis target 

mode a slight nonlinearity was observed, otherwise linearity was excellent for the 

primary target modes (Figures 26 and 27). The frequency shift observed was 

less than 1.5 Hertz (less than 5%). Linearity studies were not conducted for the 

Z-axis secondary target mode. 

NASA/TM—2005-214056 24
FIGURE 22 – X-AXIS SHAKER EXCITATION

FIGURE 23 – Y-AXIS SHAKER EXCITATION

NASA/TM—2005-214056 25
FIGURE 24 – Z-AXIS SHAKER EXCITATION

FIGURE 25 – DOOR SHAKER EXCITATION

NASA/TM—2005-214056 26
24.3

24.7

25.0

25.3

25.6 25.5 25.5

25.8 26.0

26.1

24.0

24.5

25.0

25.5

26.0

26.5

0 5 10 15 20 25

Shaker Force Level (lbs Pk)

Modal Frequency (Hz)

Sine Excitation Burst Random Excitation

Final Test Frequency 26.1 Hz

FIGURE 26 – LINEARITY OF X-AXIS RACK TRANSLATION MODE USING SINE SWEEP AND 

BURST RANDOM EXCITATION

41.5

41.2

40.7

40.1

39.6

41.2

41.5

41.8

41.9

39.5

40.0

40.5

41.0

41.5

42.0

42.5

0 5 10 15 20

Shaker Force Level (lbs Pk)

Modal Frequency (Hz)

Sine Excitation Burst Random Excitation

Final Test Frequency 41.9 Hz

FIGURE 27 – LINEARITY OF Y-AXIS RACK TRANSLATION MODE USING SINE SWEEP AND 

BURST RANDOM EXCITATION

NASA/TM—2005-214056 27
The FIR modal test had high data quality and low extraneous noise. Typical sine 

sweep excitation Frequency Response Functions (FRFs) and coherence graphs 

from the test are shown in Figures 28 – 31. Typical burst random excitation 

Frequency Response Functions (FRFs) and coherence graphs from the test are 

shown in Figures 32 – 35. Test data results can be found in the Structural 

Dynamics Laboratory test report number SDL-TR-05-12 (Reference 4). 

Three global rack translational modes were identified during FIR modal testing 

using burst random excitation. The X-axis mode occurred at 26.1 Hz, the Y-axis 

mode occurred at 41.9 Hz, and the Z-axis mode occurred at 51.9 Hz. 

NASA/TM—2005-214056 28
FIGURE 28 – TYPICAL DRIVE POINT FRF FROM X-AXIS SINE SWEEP EXCITATION

FIGURE 29 – TYPICAL DRIVE POINT COHERENCE FROM X-AXIS SINE SWEEP EXCITATION

NASA/TM—2005-214056 29
FIGURE 30 – TYPICAL FRF FROM X-AXIS SINE SWEEP EXCITATION

FIGURE 31 – TYPICAL COHERENCE FROM X-AXIS SINE SWEEP EXCITATION

NASA/TM—2005-214056 30
FIGURE 32 – TYPICAL DRIVE POINT FRF FROM X-AXIS BURST RANDOM EXCITATION

FIGURE 33 – TYPICAL DRIVE POINT COHERENCE FROM X-AXIS BURST RANDOM EXCITATION

NASA/TM—2005-214056 31
FIGURE 34 – TYPICAL FRF FROM X-AXIS BURST RANDOM EXCITATION

FIGURE 35 – TYPICAL COHERENCE FROM X-AXIS BURST RANDOM EXCITATION

NASA/TM—2005-214056 32
7. Model Correlation 

The FIR finite element model was updated based on initial low crossorthogonality of the primary target modes (rack X and Y translation) and the 

secondary mode (Z translation). 

FIR model correlation was accomplished using Attune (Reference 5) 

test/analysis correlation and model updating software. Attune uses design 

sensitivity and optimization methods to identify FEM model changes that 

minimize the difference between test and analysis results (objective function). 

Design sensitivity coefficients are used that identify important properties in the 

finite element model (FEM) for optimization. Upper and lower bounds are 

assigned to the design variables to account for parameter uncertainty. Weights 

can be assigned to the design variables to emphasize their importance on the 

objective function. State variables (design constraints) used in the optimization 

include frequency and cross-orthogonality. The Attune optimization flowchart is 

shown in Figure 36. After each iteration, the eigensolution is recalculated in 

NASTRAN using the updated design variables. 

Setup Nastran

Obtain Test Data

Run 

Nastran

Read Data 

in Attune

Modify State and 

Design Variables

Iterate Select New 

Design

Write New 

Attune Nastran Input

Correlation 

Satisfactory?

Correlation 

Satisfactory?

yes

yes

no

no

FIGURE 36 – ATTUNE OPTIMIZATION FLOWCHART

The FIR FEM was correlated using three different optimization algorithms: 

Genetic, Monte Carlo, and Gradient methods. 

The Genetic and Monte Carlo algorithms both utilize randomly generated 

candidate designs, and update the stiffness matrix based on modal matrix 

sensitivities. The Genetic algorithm evaluates a set of randomly chosen designs 

against the objective function, and then tries to systematically improve the 

designs through iteration. The advantage of the Genetic and Monte Carlo 

methods is that these methods are not trapped by local minima. The Genetic and 

NASA/TM—2005-214056 33
Monte Carlo algorithms are generally used to tune the FEM when the design 

properties are not well known, and there is a large design space. 

The Gradient method is best used when the design variables are well known, 

and only small changes are required to correlate the model. Problems associated 

with the Gradient method are encountered when the algorithm is trapped in local 

minima, causing inaccuracies in the linear approximation of the derivatives. 

The FIR model correlation methodology was based on modal testing and 

correlating each major structural assembly FEM individually (FIR Optics Bench, 

FIR Air Thermal Control Unit, Rack Door, and Lower Structure Assembly). This 

developed confidence that the major assemblies were correlated before the start 

of the FIR modal test. The final step in the correlation process was to modal test 

and model correlate the FIR. This building block approach facilitated the model 

correlation process. Once the major structure assemblies FEMs were individually 

correlated, the only areas of uncertainty in the fully populated FIR model were 

the structural connections between the assemblies, the rack, and the fixture. 

The FIR FEM was updated using the following design variables: 

• Load cell and attachment clevis (Figure 37) X, Y, Z-axes translational 

spring stiffness (PBUSH) 

• Door (Figure 38) Young’s Modulus 

• Coldplate (Figure 39) Young’s Modulus 

• Hardback (Figure 39) Young’s Modulus 

• Upper Intercostal (Figure 40) Bending Moment of Inertia 

In the Boeing rack with ARIS finite element model, the coldplate and hardback 

assembly representation is low fidelity. Based on hardware drawings, the 

coldplate and hardback assembly was replaced with a detailed finite element 

model (Figure 39) improving the characterization of the bending stiffness. 

Using the detailed FEM of the coldplate and hardback assembly, a final 

assessment was made comparing the target modes between the FIR test FEM 

and TAM, with and without the test fixture, and flight FEM and flight ASET 

configurations to assure that the test configuration was representative of flight. 

The cross-orthogonality between the test configuration FEM and the TAM were 

also re-evaluated. These comparisons are documented in Appendix F. 

In order to correlate the FIR FEM, two iterations were performed in Attune to 

update the design parameters. Table 7 summarizes the design parameter 

changes made between the pre-test and correlated FIR models. 

NASA/TM—2005-214056 34
Table 7 – Comparison of FIR FEM Design Variable Sensitivities Between the Pre-Test and Correlated Models

Design Design Pre-Test Correlated Percent

Description Type PID Property Variable Sensitivity Model Model Change

Load Cell Translational Spring Stiffness PBUSH 42122192 Stiffness (lb/in)at "A" fixture location Kx KABTX -9.358E-02 64382.5 64382.5 0.0%

Ky KABTY 6.077E-02 1.500E+05 1.500E+05 0.0%

Kz KABTZ 8.941E-02 5.850E+05 5.850E+05 0.0%

Load Cell Translational Spring Stiffness PBUSH 42122189 Stiffness (lb/in)

at "C" fixture location Kx KCTX 2.397E-05 8.529E+07 8.529E+07 0.0%

 Ky KCTY 1.840E-02 1.084E+06 1.084E+06 0.0%

 Kz KCTZ 5.603E-09 8.529E+07 8.529E+07 0.0%

Load Cell Translational Spring Stiffness PBUSH 42122190 Stiffness (lb/in)at "D" fixture location Kx KDTX 1.296E-09 1.050E+08 1.050E+08 0.0%

Ky KDTY 1.955E-05 1.230E+06 1.230E+06 0.0%

Kz KDTZ 2.154E-10 8.529E+07 8.529E+07 0.0%

Coldplate Young's Modulus MAT1 41459866 Modulus (lb/in2)

E COLDE -1.529E-01 9.900E+06 1.014E+07 2.3%

Door Young's Modulus MAT1 13129298 Modulus (lb/in2)

E DOORE 1.967E-01 1.140E+07 1.178E+07 3.2%

Hardback Young's Modulus MAT1 41459865 Modulus (lb/in2)

E HARDE -7.833E-02 9.900E+06 9.989E+06 0.9%

Upper Intercostal PSHELL 32 Bending Moment

Bending Moment of Inertia of Inertia UPPERBMI 7.542E-03 1.0 0.91529 -9.3%

NASA/TM—2005-214056 35
Z X

Y

Load Cell 

Translational 

Springs

Load Cell 

Translational 

Springs

FIGURE 37– LOAD CELL TRANSLATIONAL SPRINGS

Z

X

FIGURE 38– DOOR 

NASA/TM—2005-214056 36
Original FEM Detailed FEM

Solid Model of Hardware Assembly

Z

Y

X

FIGURE 39 – COMPARISON OF COLDPLATE AND HARDBACK HARDWARE ASSEMBLY TO 

THE ORIGINAL AND DETAILED FEM

Upper

Intercostal

Y

Z

X

FIGURE 40 – UPPER INTERCOSTAL

NASA/TM—2005-214056 37
Design variables having the greatest change from the pre-test model to the 

correlated model were the Upper Intercostal bending moment of inertia (-9.3% 

change), Door Young’s Modulus (3.2% change), Coldplate Young’s Modulus 

(2.3% change), and Hardback Young’s Modulus (0.9% change). The load cell 

interface spring stiffness properties were previously correlated during the CIR 

modal test. 

The Genetic algorithm was primarily used to correlate the model, with an overall 

RMS state variable error of 5.76% for the objective function (comparing the test 

and TAM target mode frequencies and cross-orthogonalities). The X-axis target 

mode frequency difference was -4.2%, the Y-axis target mode frequency 

difference was 2.1%, the Z-axis target mode frequency difference was 6.4%. All 

primary target mode cross-orthogonality values were greater than 90% 

(Figure 41). The Z-axis target mode was outside the frequency range of interest 

(0-50 Hz) for model correlation. These results are summarized in Table 8. 

Figures 42 – 44 illustrate a comparison between the test and TAM modes, 

effective weight, and cross-orthogonality. The test and TAM modes shapes are 

dynamically back-expanded to improve visualization. The correlated model has 

high cross-orthogonality (>90%) for the primary target modes, satisfying the ISS 

model correlation criteria. 

NASA/TM—2005-214056 38
0 0

0

0

57.2%

90.4%

98.1%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

TAM Modes

Test Modes

26.1 Hz

X-Axis

41.9 Hz

Y-Axis

51.9 Hz

Z-Axis

27.2 Hz

X-Axis 41.0 Hz

Y-Axis 48.6 Hz

Z-Axis

FIGURE 41 – FINAL CROSS-ORTHOGONALITY FOR TARGET MODES

NASA/TM—2005-214056 39
Table 8 – Comparison of Test and TAM Target Mode Frequency Difference 

and Cross-Orthogonality 

TAM in Fixture

(Back-Expanded)

Mode 1, 26.1 Hz

Effective Weight = 1289.5 lbs

Global X-axis rack translation

Test

(Back-Expanded)

Z

X

Z

X

Cross-Orthogonality 98.1%

Mode 1, 27.2 Hz

Effective Weight = 1311.5 lbs

Global X-axis rack translation

FIGURE 42 – X-AXIS TARGET MODE SHAPES, 

EFFECTIVE WEIGHT, AND CROSS-ORTHOGONALITY

TAM Delta Mode Shape

Mode 126 Freq Description

Freq (Hz) 27.2 41.0 48.6

Test 1 26.1 0.981 -0.037 -0.015 -4.2% Rack X-axis Translation

2 41.9 0.062 0.904 0.174 2.1% Rack Y-axis Translation

3 51.9 -0.102 0.36 -0.572 6.4% Rack Z-axis Translation

NASA/TM—2005-214056 40
TAM in Fixture (Back-Expanded)

Mode 2, 41.9 Hz

Effective Weight = 601.1 lbs

Global Y-axis rack translation

Test (Back-Expanded)

Z X

Y

Z X

Y

Z

Y

Z

Y

Cross-Orthogonality 90.4%

Mode 2, 41.0 Hz

Effective Weight = 1147.0 lbs

Global Y-axis rack translation

FIGURE 43 – Y-AXIS TARGET MODE SHAPES, EFFECTIVE WEIGHT, 

AND CROSS-ORTHOGONALITY

Test (Back-Expanded) TAM in Fixture (Back-Expanded)

Mode 3, 51.9 Hz

Effective Weight = 320.8 lbs

Global Z-axis rack translation

Z X

Y

Z X

Y

Z

Y

Z

Y

Cross-Orthogonality 57.2%

Mode 6, 48.6 Hz

Effective Weight = 425.0 lbs

Global Z-axis rack translation

FIGURE 44 – Z-AXIS TARGET MODE SHAPES, EFFECTIVE WEIGHT, 

AND CROSS-ORTHOGONALITY

NASA/TM—2005-214056 41
8. Conclusions 

The FIR rack finite element model was successfully correlated based on the 

International Space Station model correlation criteria. 

Three target modes were identified in test including two primary rack translation 

modes (X and Y axes) and a secondary Z axis mode. All model primary target 

modes had frequency differences less than 5% compared to test. The model 

secondary target mode has a frequency difference less than 6.4% compared to 

test (Table 8). The final cross-orthogonality between the correlated TAM and test 

mode shapes (Figure 41) was greater than 90% for all primary target modes. 

9. References 

1. “ISS Fluids and Combustion Facility Loads Model Verification Plan,” 

NASA GRC presentation to the NASA JSC Structures Working Group, 

September 24, 2003.

2. “ISPR Qualification Modal Test Correlation,” prepared by J. A. Knoll and 

H.A. Britt, Boeing rack model correlation report, 2-8F1A-HAB-049/95, 

Revision A, January 12, 1996.

3. “FIR Mass Properties Report,” FIR-RPT-1734, Final, April 20, 2005.

4. “FCF FIR GIU Rack Modal Survey Test Report,” SDL TR-05-12.

5. “Attune User’s Guide,” test/analysis correlation and modal updating 

software, Version 1.1, ATA Engineering, January 2005. 

NASA/TM—2005-214056 42
LED Light Emitting Diode 

LLL Low Light Level

LMM Light Microscopy Module

MDCA Multi-user Droplet Combustion Assembly

MEL Microgravity Emissions Laboratory

MFC Mass Flow Controller

MRDOC Microgravity Research, Development and Ops 

Contract

MCF Modal Confidence Factor

NGIT Northrop Grumman Information Technology

OB Optics Bench

OM Optics Module

OPI Optics Plate Interface

PaRIS Passive Rack Isolation System

PCS Portable Computer System

PFE Portable Fire Extinguisher

PI Principal Investigator

PIA Payload Integration Agreement

PPH Program-Provided Hardware

PSH Payload Support Hardware

PSR Pre-Ship Review

PTCU Payload Training Center Unit

Qual Qualification

REU Remote Electronic Unit

RFCA Rack Flow Control Assembly

RHA Rack Handling Adapter

RMSA Rack Maintenance Switch Assembly

RPC Remote Power Controller

RPCM Remote Power Controller Module

RUP Rack Utility Panel

SAMS Space Acceleration Measurement System

SDL Serial Data Link

SEI Software Engineering Institute

SMD Silicon Mountain

SPEL Station Power Electronics Laboratory

SSC Station Support Computer

Temp Temporary

TSC Telescience Support Center

TSH Tri-axial Sensor Head

T/O Turnover

UIP Utility Interface Panel

UF Utilization Flight

ULF Utilization and Logistics Flight

UV Ultraviolet 

VES Vacuum Exhaust System

VP Verification Plan

VRS Vacuum Resource System

VTR Verification and Test Readiness

VVS Vacuum Vent System

WFCA Water Flow Control Assembly

WTCS Water Thermal Control System

10. Acronym List 

ARIS Active Rack Isolation Subsystem

ATCS Air Thermal Control System

ATCU Air Thermal Control Unit

CDR Critical Design Review

CIR Combustion Integrated Rack

CSCI Computer Software Configuration Item

DCM Diagnostics Control Module

ECS Environmental Control Subsystem

EDA Engineering Development Article

EDU Experiment Development Unit

EM Engineering Model

EMI Electro- Magnetic Interference

EA Experiment Assembly

EPCU Electrical Power Control Unit

EVP Exhaust Vent Package

Fab Fabrication

FCF Fluids and Combustion Facility

FCU FOMA Control Unit

FDSS Fire Detection and Suppression System

FEA Fluids Experiment Assembly

FHA Flight Hardware Availability

FIR Fluids Integrated Rack

FMEA Failure Modes and Effects Analysis

FOMA Fuel/Oxidizer Management Assembly

FSAP Fluids Science Avionics Package

FSR Flight Safety Review

GCIP Gas Chromatograph Instrumentation Package

GN2 Gaseous Nitrogen

GIS Gas Interface System

GIU Ground Integration Unit

GSE Ground Support Equipment

HFR High Frame Rate

HiBMs High Bit depth Multi Spectral Camera Package

HR High Resolution

H/W Hardware

I&T Integration and Test

IAM Image Acquisition Module

ICD Interface Control Document

I/F Interface

IOP Input/ Output Processor

IPP Image Processing Package

IPSU Image Processing and Storage Unit

IPSU-A Image Processing and Storage Unit, Version A

IR Infrared

ISPR International Standard Payload Rack

ISS International Space Station

 

NASA/TM—2005-214056 43
11. Appendices 

Appendix A FIR Optics Bench Model Correlation 

Appendix B Air Thermal Control Unit (ATCU) Model Correlation 

Appendix C Rack Door Model Correlation

Appendix D Lower Package Structure Model Correlation 

Appendix E FIR Rack Modal Instrumentation Plan 

Appendix F FIR Rack Correlated Model Comparison of 

Frequency and Cross-Orthogonality 

NASA/TM—2005-214056 44
Appendix A 

FIR Optics Bench with FSAP

Model Correlation

Fluids Science 

Avionics Package 

(FSAP)

Y

Z

X

NASA/TM—2005-214056 45
X 

Y 

Z 

FIR Optics Bench with FSAP Test Configuration 

NASA/TM—2005-214056 46
FIR Optics Bench with FSAP

Comparison of FEM to TAM

BOLD INDICATES TARGET MODES

Mode Frequency (Hz) Effective Mass (%) Mode Frequency (Hz) Effective Mass (%)

1 119.57 35.5% - Y 1 122.3 52.2% - Y

2 146.67 71.2% - X 2 148.5 65.9% - X

3 155.42 18.3% - X 3 158.7 28.4% - X

4 198.65 4 215.1

5 220.76 5 242.4 17.3% - Y

6 261.86 6 300.5 35.6% - Z

7 263.41 7 327.3 37.7% - Z

8 267.77

9 280.35

10 281.44

11 283.59 23.8% - Z

FEM (65,568 DoF) TAM (29 DoF)

FIR Optics Bench with FSAP

Comparison of FEM to TAM

MODE SHAPE FEM TAM XORTHO % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF

Translation of FIR Optics Bench in Y-Axis 119.6 122.3 95.4 -2.30

Translation of FIR Optics Bench in X-Axis 146.7 148.5 96.7 -1.27

NASA/TM—2005-214056 47
FIR Optics Bench with FSAP

Cross Orthogonality

FEM vs TAM

TAM MODE FREQUENCIES

Mode 

Number 1 2 3 4 56

Hz 122.3 148.5 158.8 215.1 242.4 300.5

1 119.6 95.4 0.0 0.0 0.0 0.0 0.0

FEM 2 146.7 0.0 96.7 0.0 0.0 0.0 0.0

MODES 3 155.4 0.0 12.8 94.9 0.0 0.0 0.0

FREQUENCIES 4 198.7 0.0 0.0 0.0 84.3 13.6 0.0

5 220.8 0.0 0.0 0.0 0.0 80.8 0.0

6 261.9 0.0 0.0 11.4 0.0 14.1 61.4

FIR Optics Bench with FSAP

Cross Orthogonality Graph

FEM vs TAM

119.6 146.7 155.4 198.7 220.8 261.9

122.3

148.5

158.8

215.1

242.4

300.5

61.4

84.3 80.8

95.4 96.7 94.9

0.0

20.0

40.0

60.0

80.0

100.0

P e r c e nt a ge ( %)

FEM Fr e que nc ie s ( Hz )

TAM Fr e que nc ie s ( Hz )

NASA/TM—2005-214056 48
FIR Optics Bench with FSAP

Comparison of TAM to TEST

MODE SHAPE TAM TEST XORTHO % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF

Translation of FIR Optics Bench in Y-Axis 122.3 117.7 92.3 -3.91

Translation of FIR Optics Bench in X-Axis 148.5 135.0 71.8 -10.00

FIR Optics Bench with FSAP 

Cross Orthogonality

TAM vs TEST

TEST MODE FREQUENCIES

Mode 

Number 1 2

TAM Hz 117.7 135.0

MODE 1 122.3 92.3 27.7

FREQUENCIES 2 148.5 13.2 71.8

FIR Optics Bench with FSAP

Cross Orthogonality Graph

TAM vs TEST

117.7

135.0

122.3

148.5

71.8

92.3

0.0

20.0

40.0

60.0

80.0

100.0

Percentage (%)

Test Frequencies (Hz)

TAM Frequencies (Hz)

NASA/TM—2005-214056 49
FIR Optics Bench with FSAP

Comparison of FEM to TEST

MODE SHAPE FEM TEST % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) DIFF

Translation of FIR Optics Bench in Y-Axis 119.6 117.7 -1.59

Translation of FIR Optics Bench in X-Axis 146.7 135.0 -8.64

FEM

Mode 1, 119.6 Hz

35.5 % Effective Mass

FIR Optics Bench with FSAP

Comparison of FEM to Test

Mode Shapes - Y Axis

Cross-Orthogonality 92.3%

TEST

117.7 Hz

Damping = 4.22%, MCF = 0.487

Y

Z

X

1st Bending Mode of the Optics Bench in the Y-Axis

NASA/TM—2005-214056 50
FEM

Mode, 146.7 Hz

71.1% Effective Mass

FIR Optics Bench with FSAP 

Comparison of FEM to Test

Mode Shapes - X Axis

Cross-Orthogonality 71.8%

TEST

135.0 Hz

Damping = 3.99%, MCF = 0.898

Translation of the Optics Bench in the X-Axis

Y

Z

X

NASA/TM—2005-214056 51

Appendix B 

FIR ATCU 

Model Correlation

Z

Y X

NASA/TM—2005-214056 53
Y

X

X

Z

Y

ATCU Test Configuration 

NASA/TM—2005-214056 54
FIR ATCU

Comparison of FEM to TAM

BOLD INDICATES TARGET MODES

Mode Frequency (Hz) Effect Mass (%) Mode Frequency (Hz) Effect Mass (%)

1 60.9 94.8-X 1 61.4 99.7-X

2 77.0 27.1-X 2 85.5 46.2-Z

3 89.3 3 110.5 59.8-Y

4 93.2 16.1-Z

5 103.3 49.7-Y

FEM (20,392 DoF) TAM (55 DoF)

MODE SHAPE FEM TAM XORTHO % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF

Translation of the ATCU in the X-Axis 60.9 61.4 98.7 0.8

In Phase Translation of the ATCU Fans in the Z-Axis 77.0 85.5 94.9 9.9

Translation of the ATCU in the Y-Axis 103.3 110.5 80.7 6.5

FIR ATCU

Comparison of FEM to TAM

FIR ATCU

Cross Orthogonality

FEM vs TAM

TAM MODE FREQUENCIES

Mode 

Number 1 2 3 4 5 6 7 8 9 10

Hz 61.4 85.5 110.5 135.3 139.6 176.4 183.5 199.4 213.3 225.4

1 60.9 98.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

2 77.0 0.0 70.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

3 89.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

4 93.2 0.0 56.7 14.8 14.3 11.5 0.0 0.0 0.0 0.0 0.0

5 103.3 0.0 0.0 83.0 12.6 0.0 0.0 0.0 0.0 0.0 0.0

FEM 6 145.0 0.0 20.1 21.5 51.5 25.7 0.0 0.0 0.0 0.0 0.0

MODE 7 124.4 0.0 0.0 0.0 40.3 0.0 0.0 0.0 0.0 0.0 0.0

FREQUENCIES 8 155.5 0.0 29.6 0.0 0.0 0.0 10.5 10.2 0.0 0.0 0.0

9 157.2 0.0 0.0 0.0 28.4 36.7 0.0 0.0 0.0 0.0 0.0

10 161.1 0.0 0.0 0.0 0.0 0.0 66.5 12.2 0.0 21.0 0.0

11 167.2 0.0 0.0 0.0 14.4 12.5 25.8 28.0 18.1 38.2 14.4

12 168.5 0.0 0.0 0.0 16.1 13.4 26.2 25.7 48.8 15.3 0.0

13 175.1 0.0 0.0 0.0 0.0 0.0 29.3 0.0 0.0 0.0 0.0

14 180.9 0.0 0.0 0.0 13.2 13.3 0.0 54.5 35.5 17.3 0.0

15 184.5 0.0 0.0 0.0 20.3 17.4 0.0 20.0 27.6 0.0 0.0

NASA/TM—2005-214056 55
FIR ATCU

Cross Orthogonality Graph

FEM vs TAM

61.4

110.5

139.6

183.5

213.3

54.5

66.5

51.5

83.0

70.2

56.7

98.4

0.0

20.0

40.0

60.0

80.0

100.0

Percentage (%)

FEM Frequencies (Hz)

TAM Frequencies 

(Hz)

FIR ATCU

Comparison of TAM to TEST

MODE SHAPE TAM TEST XORTHO % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF

Translation of ATCU in the X-axis 61.4 59.7 99.8 -2.8

In Phase Translation of the ATCU Fans in the Z-Axis 85.5 79.6 94.3 -7.4

Translation of ATCU in Y-axis 110.5 109.2 97.6 -1.2

FIR ATCU

Cross Orthogonality

TAM vs TEST

TEST MODE FREQUENCIES

Mode 

Number 12 4

TAM Hz 59.7 76.9 109.2

MODE 1 61.4 99.8 0.7 0.4

FREQUENCIES 2 85.5 0.8 94.3 13.1

3 110.5 0.0 21.8 97.6

NASA/TM—2005-214056 56
FIR ATCU

Cross Orthogonality Graph

TAM vs TEST

59.7

76.9

109.2

61.4

85.5

110.5

97.6

94.3 99.8

0.0

20.0

40.0

60.0

80.0

100.0

Percentage (%)

Test Frequencies (Hz)

TAM Frequencies (Hz)

FIR ATCU

Comparison of FEM to TEST

MODE SHAPE FEM TEST % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) DIFF

Translation of the ATCU in the X-Axis 60.9 59.7 2.0

In Phase Translation of the ATCU Fans in the Z-Axis 77.0 76.9 0.1

Translation of the ATCU in the Y-Axis 103.3 109.2 5.4

NASA/TM—2005-214056 57
FEM

Mode 1, 60.9 Hz

94.8% Effective Mass

Comparison of FIR ATCU FEM with Test

Mode Shapes - X Axis

Cross-Orthogonality 99.8%

Z

Y X

TEST

59.7 Hz

Damping = 0.92, MCF = 1.000

Translation of the ATCU in the X-Axis 

NASA/TM—2005-214056 58
FEM

Mode 2, 77.0 Hz

27.1% Effective Mass

Comparison of FIR ATCU FEM with Test

Mode Shapes - Z Axis

Cross-Orthogonality 94.3%

TEST

76.9 Hz

Damping = 0.65, MCF = 1.000

Z

Y X

In Phase Translation of the ATCU Fans in the Z-Axis 

NASA/TM—2005-214056 59
FEM

Mode 5, 103.3 Hz

49.7% Effective Mass

Comparison of FIR ATCU FEM with Test

Mode Shapes - Y Axis

Cross-Orthogonality 92.3%

TEST

109.2 Hz

Damping = 1.88, MCF = 0.999

Z

Y X

Translation of the ATCU in the Y-Axis 

NASA/TM—2005-214056 60
Appendix C 

CIR Rack Door

Model Correlation

Z

Y

X

NASA/TM—2005-214056 61
X

Z

Rack Door Test Configuration 

NASA/TM—2005-214056 62
CIR Rack Door

Comparison of FEM to TAM

FEM (33,396 Grid Pts) TAM (39 DoF)

Mode Frequency (Hz) Effect Mass (%) Mode Frequency (Hz) Effect Mass (%)

1 57.9 33.3-Y 1 58.2 57.3-Y

2 90.1 1.6-Y 2 91.5 

3 99.7 12.3-Y 3 101.6 17.1-Y 

4 112.1 4 113.9 

BOLD INDICATES TARGET MODES

Comparison of CIR Rack Door

FEM with TAM

MODE SHAPE FEM TAM XORTHO % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF

Y-axis First Bending Mode of the Doors 57.9 58.2 99.0 0.5

Y-axis Second Bending Mode of the Doors 90.1 91.5 96.8 1.6

Y-axis Third Bending Mode of the Doors 99.7 101.6 96.1 1.9

NASA/TM—2005-214056 63
CIR Rack Door

Cross Orthogonality

FEM vs TAM

TAM MODE 

Mode 

Number 1 2 3 4 5 6 7 8 9 10

Hz 58.2 91.5 101.6 113.9 163.3 176.0 203.3 223.7 230.3 247.3

1 57.9 99.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

FEM 2 90.1 0.0 96.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

MODE 3 99.7 0.0 0.0 96.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

4 112.1 0.0 0.0 0.0 96.9 0.0 0.0 0.0 0.0 0.0 0.0

CIR Rack Door

Cross Orthogonality Graph

FEM vs TAM

58.2

91.5

101.6

113.9

57.9

90.1

99.7

112.1

96.9 96.8 96.1 99.0

0.00

20.00

40.00

60.00

80.00

100.00

Percentage (%)

TAM Frequency (Hz)

FEM Frequency (Hz)

NASA/TM—2005-214056 64
Comparison of CIR Rack Door

TAM with Test

MODE SHAPE TAM TEST XORTHO % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF

Y-axis First Bending Mode of the Doors 58.2 55.2 99.8 5.2

Y-axis Second Bending Mode of the Doors 91.5 81.4 97.0 11.1

Y-axis Third Bending Mode of the Doors 101.6 90.7 96.4 10.8 

CIR Rack Door

Cross Orthogonality

TAM vs TEST

TEST MODE 

Mode 

Number 123

TAM Freq (Hz) 55.2 81.4 90.7

MODE 1 58.2 99.8 1.7 17.5

2 91.5 0.4 97.0 13.7

3 101.6 4.9 19.7 96.4

CIR Rack Door

Cross Orthogonality Graph

TAM vs TEST

55.2

81.4

90.7

58.2

91.5

101.6

97.0 96.4 99.8

0.00

20.00

40.00

60.00

80.00

100.00

Percentage (%)

Test Frequencies (Hz)

TAM Frequencies 

(Hz)

NASA/TM—2005-214056 65
Comparison of CIR Rack Door

FEM with Test

MODE SHAPE FEM TEST % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) DIFF

Y-axis First Bending Mode of the Doors 57.9 55.2 4.9

Y-axis Second Bending Mode of the Doors 90.1 81.4 10.7

Y-axis Third Bending Mode of the Doors 99.7 90.7 9.9

FEM

Mode 1, 57.9 Hz

33.3 % Effective Mass

Comparison of CIR Rack Door

FEM with Test

Mode Shapes - Y Axis

Cross-Orthogonality 99.8%

TEST

55.2 Hz

Damping = 0.636 , MCF = 1.000 

Z

Y

X

Y-axis First Bending Mode of the Doors

NASA/TM—2005-214056 66
FEM

Mode 2, 90.1 Hz

1.6 % Effective Mass

Comparison of CIR Rack Door 

FEM with Test

Mode Shapes - Y Axis

Cross-Orthogonality 97.0%

TEST

81.4 Hz

Damping = 1.666 , MCF = 0.997 

Y-axis Second Bending Mode of the Doors

Z

Y

X

NASA/TM—2005-214056 67
Comparison of CIR Rack Door

FEM with Test

Mode Shapes - Y Axis

Cross-Orthogonality 96.4%

FEM

Mode 3, 99.7 Hz

12.3 % Effective Mass

TEST

90.7 Hz

Damping = 1.384, MCF = 0.999 

Z

Y

X

Y-axis Third Bending Mode of the Doors

NASA/TM—2005-214056 68
Appendix D

CIR Lower Structure Assembly 

Model Correlation

Z

Y

X

NASA/TM—2005-214056 69
EPCU

IOP

X

Z

Y

Lower Structure Assembly Test Configuration 

NASA/TM—2005-214056 70
CIR Lower Structure Assembly

Comparison of FEM to TAM

FEM (100,944 DoF) TAM (38 DoF)

Mode Frequency (Hz) Effect Mass (%) Mode Frequency (Hz) Effect Mass (%)

1 105.7 25.8-X 1 106.4 29.5-X

2 125.2 44.5-Z 2 127.3 55.7-Z

3 143.9 21.4-X 3 145.7 25.5-X

4 173.8 4 176.7

5 175.2 60.2-Y 5 177.9 56.3-Y

BOLD INDICATES TARGET MODES 

Comparison of CIR Lower Structure

FEM with TAM

MODE SHAPE FEM TAM XORTHO % FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF

Translation of the Lower Structure in the X-Axis 105.7 106.4 98.7 0.6

Translation of the EPCU in the Z-Axis 125.2 127.3 96.7 1.7

Translation of the Lower Structure in the Y-Axis 175.2 177.9 96.1 1.6

NASA/TM—2005-214056 71
CIR Lower Structure Assembly

Cross Orthogonality

FEM vs TAM

TAM MODE

Mode 

Number 1 2 3 4 5 6 7 8 9 10 11

Hz 106.4 127.3 145.7 176.5 177.9 192.4 202.4 219.0 229.7 331.5 350.2

1 105.7 98.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

2 125.2 0.0 96.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

3 143.9 0.0 0.0 97.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

FEM 4 173.8 0.0 0.0 0.0 96.1 11.0 0.0 0.0 0.0 0.0 0.0 0.0

MODE 5 175.2 0.0 0.0 0.0 11.3 96.1 0.0 0.0 0.0 0.0 0.0 0.0

6 189.1 0.0 0.0 0.0 0.0 0.0 96.3 0.0 0.0 0.0 0.0 0.0

7 198.5 0.0 0.0 0.0 0.0 0.0 0.0 96.0 0.0 0.0 0.0 0.0

8 212.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 93.2 0.0 0.0 0.0

9 224.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 95.4 0.0 0.0

10 290.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 67.7 30.1

11 311.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 30.4 54.7

CIR Lower Structure Assembly

Cross Orthogonality Graph 

FEM vs TAM

105.7

125.2

143.9

173.8

175.2

189.1

198.5

212.2

224.8

290.4

311.4

106.4

145.7

177.9

202.38

229.67

350.15

54.7

67.7

95.4

93.2

0.000.00

96.0

0.00

96.3

96.1

96.1

97.4

96.7

98.7

0.00

20.00

40.00

60.00

80.00

100.00

Percentage (%)

FEM Frequencies (Hz)

TAM Frequencies (Hz)

NASA/TM—2005-214056 72
CIR Lower Structure Assembly

Cross Orthogonality Graph 

TAM vs TEST

106.4

127.3

177.9

112.5

138.5

169.5

52.2

25.9

39.9

54.9

44.9

0.00

20.00

40.00

60.00

80.00

100.00

Percentage (%)

TAM Frequencies (Hz)

Test Frequencies (Hz)

Comparison of CIR Lower Structure

TAM with TEST

MODE SHAPE TAM TEST XORTHO FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) % DIFF (%)

Translation of the Lower Structure in the X-Axis 106.4 112.5 54.9 5.4

Translation of the EPCU in the Z-Axis 127.3 138.5 39.9 8.1

Translation of the Lower Structure in the Y-Axis 177.9 169.5 29.9 5.0

CIR Lower Structure Assembly

Cross Orthogonality

TAM vs TEST

TEST MODE

124

Freq (Hz) 112.5 138.5 169.5

TAM 1 106.4 54.9 44.9 14.9

MODE 2 127.3 0.0 39.9 15.9

5 177.9 0.3 52.2 25.9 

 

NASA/TM—2005-214056 73
Comparison of CIR Lower Structure

FEM with TEST

MODE SHAPE FEM TEST FREQ

DESCRIPTION FREQ (Hz) FREQ (Hz) DIFF (%)

Translation of the Lower Structure in the X-Axis 105.7 112.5 6.1

Translation of the EPCU in the Z-Axis 125.2 138.5 9.6

Translation of the Lower Structure in the Y-Axis 175.2 169.5 3.3

FEM

Mode 1, 105.7 Hz

25.8 % Effective Mass

Comparison of CIR Lower Structure Assembly

FEM with Test

Mode Shapes - X Axis

Cross-Orthogonality 54.9%

TEST

112.5 Hz

Damping = 1.46 %, MCF = 1.00

Z

Y

X

Translation of the Lower Structure in the X-Axis

EPCU

IOP

EPCU

IOP

NASA/TM—2005-214056 74
FEM

Mode 2, 125.2 Hz

44.5% Effective Mass

Comparison of CIR Lower Structure Assembly

FEM with Test

Mode Shapes - Z Axis

Cross-Orthogonality 39.9%

TEST

138.5 Hz

Damping = 0.95 , MCF = 1.00

Z

Y

X

Translation of the EPCU in the Z-Axis

EPCU

IOP

EPCU

IOP

NASA/TM—2005-214056 75
FEM

Mode 5, 175.2 Hz

60.2 % Effective Mass

Comparison of CIR Lower Structure Assembly

FEM with Test

Mode Shapes - Y Axis

Cross-Orthogonality 25.9%

TEST

169.5 Hz

Damping =1.08 , MCF = 1.00

Z

Y

X

Translation of the Lower Structure in the Y-Axis

EPCU

IOP

EPCU

IOP

 

NASA/TM—2005-214056 76
Appendix E 

FIR Rack

Modal Instrumentation Plan

NASA/TM—2005-214056 77
FIR Modal Rack Instrumentation Plan

ISPR (13 locations, 31 accels)

Rack Front View

Rear Right Post Locations

3008 xy Right Rear Post, 

Upper Position

3033 xy Right Rear Post, 

Upper Middle Position

3160 xy Right Rear Post, 

Lower Middle Position

3294 xy Right Rear Post, 

Lower Position

Rack Front View

Rear Left Post Locations

2602 xy Left Rear Post, 

Upper Position

2605 xy Right Rear Post, 

Upper Middle Position

2708 xy Right Rear Post, 

Lower Middle Position

2795 xy Right Rear Post, 

Lower Position

X

Z

Y

X

Y

Z

10128 xyz Left REU,

Lower Left Intercostal

10129 xyz Right REU,

Lower Intercostal

10125 xyz ARIS 

Controller, Lower Left 10126 xyz ARIS 

Actuator Driver, Lower Right 

NOTE: RUP Panel Not Shown for Clarity

10127 xyz REU,

Upper Intercostal

3081 x Right Front Post, 

Upper Middle Position

3179 x Right Front Post, 

Lower Middle Position

2572 x Right Front Post, 

Upper Middle Position

2769 x Right Front Post, 

Lower Middle Position

NASA/TM—2005-214056 78
Rack Top View

Top Panel

Rack Front

Rack Rear

Rack Left Side

Rack Right Side

642 z Rack Top: Center Middle

FIR Modal Rack Instrumentation Plan

ISPR (1 locations, 1 accel)

NASA/TM—2005-214056 79
FIR Modal Rack Instrumentation Plan

Blue Boy Control Accelerometers (6 locations, 24 accels)

Near Load Cell “D”

7001409 xyz

Near Load Cell “C”

7000537 xyz

Near Load Cell “B”

7000636 xyz

Near Load Cell “A”

7001508 xyz

On Rack Near Load Cell “A”

8418 xyz

On Rack Near Load Cell “B”

8439 xyz

NASA/TM—2005-214056 80
FIR Modal Rack Instrumentation Plan

Strut (5 locations, 12 accels)

8300 xyz Left upper 

kneebrace on knuckle

8327 xyz Right upper 

kneebrace on knuckle

7051 xz Right kneebrace

on center of span

7030 xz Diagonal kneebrace

at center of span

7007 xz Left kneebrace

on center of span

NASA/TM—2005-214056 81
FIR Modal Rack Instrumentation Plan

ATCU (2 locations, 2 accels)

ATCU Top View

Rack Front

Rack Rear

Rack Left Side

Rack Right Side

1022735 z

Left top fan

1021070 z

Right top fan

X

Y

Z (out of page)

NASA/TM—2005-214056 82
FIR Modal Rack Instrumentation Plan

ATCU (4 locations, 4 accels)

Rack Front

Rack Rear

Rack Left Side

Rack Right Side

1019261 x

ATCU: Left side 

bracket, Center

1000144 y

ATCU: Front Panel, Far 

Left Side, Middle Ht

1000056 y

ATCU: Front panel, Far 

Right Side, Middle Ht

1010912 y

ATCU: Front Panel, 

Center (behind EEU)

X

Y

Z

ATCU Top View

NASA/TM—2005-214056 83
FIR Modal Rack Instrumentation Plan

ATCU (4 locations, 4 accels)

Rack Front

Rack Left Side Rack Rear

Rack Right Side

1000144 y

Left front panel

1000056 y

Right front panel

1010912 y

Center front panel 

(behind EEU)

1019563 x

ATCU: Right side 

bracket, Center

X

Y

Z

ATCU Top View

NASA/TM—2005-214056 84
FIR Modal Rack Instrumentation Plan

ATCU (2 locations, 4 accels)

Rack Front

Rack Rear

Rack Right Side

Rack Left Side

1010912 y

Center Front Panel (behind 

EEU)

1001369 xyz

ATCU: Intersection of Cross 

Stiffeners

ATCU Bottom View

X

Z

Y

NASA/TM—2005-214056 85
FIR Modal Rack Instrumentation Plan

Door (16 locations, 16 accels)

3601855 y Frt Door: Lower 

Section, Center Left 3601747 y Frt Door: Lower 

Section, Center Right

3601956 y Frt Door: Lower 

Section, Center Top

3602637 y Frt Door: Lower Middle 

Section, Center Left

3602181 y Frt Door: Lower 

Middle Section, Center Bottom

3602340 y Frt Door: Lower 

Middle Section, “Center Right”

3602538 y Frt Door: Middle Lower 

Section, Center Top

3603381 y

3603936 y Frt Door: Upper Middle 

Section, “Center Left” 3603778 y Frt Door: Upper 

Middle Section, “Center Right”

3604131 y Frt Door: Upper 

Middle Section, “Center Top”

3604435 y Fnt Door: Top Section, 

“Center Bottom”

3604726 y Fnt Door: Top Section, 

“Center Left”

3604494 y Fnt Door: Top 

Section, “Center Right”

3605800 y Left Center Hinge

3605754 y Frt Door: Right 

Center Hinge

Rack Door 

Front View

Bottom front of rack

Top front of rack

Rack Left Side

Rack Right Side

X

Z

Y (into the page)

NASA/TM—2005-214056 86
FIR Modal Rack Instrumentation Plan

Lower Structure Assembly (5 locations, 9 accels)

1212784 xyz

Top of EPCU

1215282 xyz

Top of IOP

1207110 x

Lower Structure: Left 

rail, Center Middle

1201842 x

Lower Structure: Middle 

rail, Center Middle

1200977 x

Lower Structure: Right 

Rail, Center Middle

Front Perspective View of Lower Structure Assembly

Rack Front

Rack Right Side

Rack Left Side

Rack Rear

X

Y

Z

NASA/TM—2005-214056 87
Front Side of Optics Bench

Top

Bottom

Left Side Right Side

58338356 xyz

On FSAP Enclosure

X

Y

Z

5009061 xy

Front Bench, 

Top Left Corner 5009057 xy

Front Bench, 

Top Right Corner

5009349 x

Front Bench, 

Bottom Left Corner

5009332 x

Front Bench, Bottom 

Right Corner

5008385 y

Front Bench, 

Top Left

5009172 y

Front Bench, 

Top Middle

FIR Modal Rack Instrumentation Plan

Optics Bench (10 locations, 15 accels)

5008189 y

Front Bench, 

Top Right

5008784 y

Front Bench, 

Middle Right

5008992 y

Front Bench, 

Middle Right

5009190 y

Front Bench, 

Middle

NASA/TM—2005-214056 88
FIR Modal Rack Instrumentation Plan

Slide and Launch Brackets (5 locations, 8 accels)

Rack Top

Rack Bottom

Right Interior View of Rack

Rack Front

Rack Rear

5006153 xy

Right Interior 

Bench, Middle 

Lower Launch 

Bracket

5005344 x

Right Interior Bench, 

Top of Slide

5004106 xy

Right Interior Bench, 

Middle of Slide

5005271 x

Right Interior Bench, 

Bottom of Slide

7003900 xy

Right Interior 

Bench, Middle 

Upper Launch 

Bracket

NASA/TM—2005-214056 89
Rack Top

Rack Bottom

Left Interior View of Rack

Rack Front

Rack Rear

FIR Modal Rack Instrumentation Plan

Slide and Launch Brackets (5 locations, 8 accels)

7004067 xy

Left Interior 

Bench, Middle 

Upper Launch 

Bracket

5003776 x

Left Interior Bench, 

Top of Slide

5002541 xy

Left Interior Bench, 

Middle of Slide

5003703 x

Left Interior Bench, 

Bottom of Slide

5005732 xy

Left Interior 

Bench, Middle 

Lower Launch 

Bracket

NASA/TM—2005-214056 90
Appendix F 

 

FIR Rack Correlated Model Comparison of 

Frequency and Cross-Orthogonality

NASA/TM—2005-214056 91
TABLE F.1 – COMPARISON OF FLIGHT FEM (IN RIGID BOUNDARY CONDITIONS) AND 

TAM (IN RIGID BOUNDARY CONDITIONS) TARGET MODE FREQUENCY DIFFERENCE AND 

CROSS-ORTHOGONALITY 

TABLE F.2 – COMPARISON OF TEST FEM (IN RIGID BOUNDARY CONDITIONS) AND TEST 

FEM (IN FIXTURE) TARGET MODE FREQUENCY DIFFERENCE AND

CROSS-ORTHOGONALITY 

TABLE F.3 – COMPARISON OF TEST AND TAM TARGET MODE FREQUENCY 

DIFFERENCE AND CROSS-ORTHOGONALITY 

FLIGHT ASET Rigid BC Delta Mode Shape

Mode 1 56 Freq Description

Freq (Hz) 30.3 47.9 53.0

TAM 1 27.2 0.966 0 0 -10.2% Rack X-axis Translation

Rigid BC 5 46.7 0 -0.948 0 -2.5% Rack Y-axis Translation

6 51.1 0 0 -1.022 -3.6% Rack Z-axis Translation

Test FEM Rigid BC Delta Mode Shape

Mode 1 78 Freq Description

Freq (Hz) 29.8 46.1 50.8

Test FEM 1 26.8 -0.988 0.000 0 -10.1% Rack X-axis Translation

w/Fixture 5 41.1 0 0.700 0.236 -10.8% Rack Y-axis Translation 

8 47.9 0 0.403 -0.773 -5.7% Rack Z-axis Translation

TAM Delta Mode Shape

Mode 1 26 Freq Description

Freq (Hz) 27.2 41.0 48.6

Test FEM 1 26.8 -0.963 0 0 -1.5% Rack X-axis Translation

w/Fixture 5 41.1 0 0.914 0 0.2% Rack Y-axis Translation

8 47.9 0 0 0.961 -1.5% Rack Z-axis Translation

NASA/TM—2005-214056 92
Flight FEM in Rigid BC Test FEM in Rigid BC

Z

X

Z

X

Test FEM in Fixture

Z

X

Mode 1, 29.8 Hz

Effective Weight = 1303.7 lbs

Global X-axis rack translation

Mode 1, 29.8 Hz

Effective Weight = 1208.8 lbs

Global X-axis rack translation

Mode 1, 26.8 Hz

Effective Weight = 1329.4 lbs

Global X-axis rack translation

FIGURE F.1 – X-AXIS PRIMARY TARGET MODE 

Flight FEM in Rigid BC

Z

Y

Test FEM in Rigid BC

Z

Y

Z X

Y

Z X

Y

Test FEM in Fixture

Z

Y

Z X

Y

Mode 7, 47.2 Hz

Effective Weight = 554.6 lbs

Global Y-axis rack translation

Mode 7, 46.1 Hz

Effective Weight = 504.8 lbs

Global Y-axis rack translation

Mode 5, 41.1 Hz

Effective Weight = 1026.7 lbs

Global Y-axis rack translation

FIGURE F.2 – Y-AXIS PRIMARY TARGET MODE

NASA/TM—2005-214056 93
Flight FEM in Rigid BC

Z

Y

Z X

Y

Test FEM in Rigid BC

Z

Y

Z X

Y

Test FEM in Fixture

Z X

Y

Z

Y Mode 8, 50.8 Hz

Effective Weight = 95.1 lbs

Global Z-axis rack translation

Mode 8, 47.9 Hz

Effective Weight = 516.5 lbs

Global Z-axis rack translation

Mode 8, 52.0 Hz

Effective Weight = 82.0 lbs

Global Z-axis rack translation

FIGURE F.3 – Z-AXIS SECONDARY TARGET MODE 

NASA/TM—2005-214056 94
Flight ASET

(Back-Expanded)

Z

X

TAM Rigid BC

(Back-Expanded) 

Z

X

Cross-Orthogonality 96.6%

Mode 1, 30.4 Hz

Effective Weight = 1182.2 lbs

Global X-axis rack translation

Mode 1, 30.3 Hz

Effective Weight = 1291.1 lbs

Global X-axis rack translation

FIGURE F.4 – COMPARISON OF TEST FEM TO TAM FOR THE X-AXIS TARGET MODE 

TAM Rigid BC (Back-Expanded)

Z

Y

Z X

Y

Flight ASET (Back-Expanded)

Z X

Y

Z

Y

Cross-Orthogonality 102.2%

Mode 6, 51.1 Hz

Effective Weight = 71.0 lbs

Global Z-axis rack translation

Mode 6, 53.0 Hz

Effective Weight = 60.5 lbs

Global Z-axis rack translation

FIGURE F.5 – COMPARISON OF TEST FEM TO TAM FOR THE Y-AXIS TARGET MODE 

NASA/TM—2005-214056 95
TAM Rigid BC (Back-Expanded)

Z

Y

Z X

Y

Flight ASET (Back-Expanded)

Z X

Y

Z

Y

Cross-Orthogonality 102.2%

Mode 6, 51.1 Hz

Effective Weight = 71.0 lbs

Global Z-axis rack translation

Mode 6, 53.0 Hz

Effective Weight = 60.5 lbs

Global Z-axis rack translation

FIGURE F.6 – COMPARISON OF TEST FEM TO TAM FOR THE Z-AXIS TARGET MODE 

NASA/TM—2005-214056 96
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102

Fluids and Combustion Facility: Fluids Integrated Rack Modal Model Correlation

Mark E. McNelis, Vicente J. Suarez, Timothy L. Sullivan, Kim D. Otten,

and James C. Akers

Structural dynamics; Modal testing

Unclassified -Unlimited

Subject Category: 39

Mark E. McNelis and Vicente J. Suarez, NASA Glenn Research Center; Timothy L. Sullivan (Retired), Kim

D. Otten, and James C. Akers, Analex Corporation, 1100 Apollo Drive, Brook Park, Ohio 44142. Responsible

person, Mark E. McNelis, organization code DEV, 216–433–8395.

The Fluids Integrated Rack (FIR) is one of two racks in the Fluids and Combustion Facility on the International Space

Station. The FIR is dedicated to the scientific investigation of space system fluids management supporting NASA’s

Exploration of Space Initiative. The FIR hardware was modal tested and FIR finite element model updated to satisfy the

International Space Station model correlation criteria. The final cross-orthogonality results between the correlated model

and test mode shapes was greater than 90 percent for all primary target modes.