GLAST Large Area Telescope: Mechanical Systems Peer Review 27 March 2003

GLAST LAT Project DOE/NASA Mechanical Systems Peer Review, March 27, 2003

Section 4.2 - Mechanical Systems Radiator Assy 1

GLAST Large Area Telescope:GLAST Large Area Telescope:

Mechanical Systems Peer Review27 March 2003Radiator Structural Design

Parviz SharifiLockheed MartinStructural Analysis

[email protected]

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope



Radiator Level IV Design and Structural RequirementsRadiator Level IV Design and Structural Requirements

Parag. Parameter Requirement Design Margin ComplyVer.

Method3.3.3 Stiffness > 50 Hz > 60 Hz +10 Hz Y A, T

3.3.4 Dynamic Envelope Shown in ICD± 1.8 mm (Launch Loads) ± 3.2 mm (2mm misalign.)

-2.2 mmN (TBD),

working on ICD

A, T

3.3.6 Static LoadsSee Table 8

(TBR)Gx = 5.1 g, Gy = 30 g, and

Gz = 8.5 g

Core Shear MSu = 0.02; Brckt Inserts MSu = 0.03; Heat Pipes MSy = 0.39

Y (insert test TBD)

A

3.3.8 Acoustic Loads See Table 9 Included aboveLoads included in above margins

Y A, T

3.3.9 Shock Loads See Table 10 TBD TBD TBDA, Test at Obs. Level

3.3.10 Sinusoidal VibrationSee Table 11

(TBR)Enveloped by above

Enveloped by Static Loads

Y A, T

Based on: Radiator Level IV Design Specification, LAT-SS-00394-1-D6, Draft, Dated 5 Mar 2003

LAT Mechanical Systems Interface Definition Dwg, Radiator-LAT Interface, LAT-DS-01221, Draft, Dated 25 Feb 2003

Verification Methods A: Analysis, I: Inspection, T: Test



Finite Element Model of RadiatorFinite Element Model of Radiator• Honeycomb sandwich construction

– Modeled using 3 layer sandwich plate-shell elements

– Captures core shear deformation effects

• Heat pipes

– Modeled using beam elements

• Panel end-member and brackets

– Modeled using beam elements

• Tie downs

– Modeled using grounded springs

• Bolted connections

– Modeled with grounded or zero-length springs

• Model Size:

– Nodes 4840

– Shell elements: 4284

– Beam elements: 564

– Spring Elements: 38

• Analysis Weight: 36.0 kg (79.3lb) per radiator

Radiator FEA Mesh Radiator FEA Mesh

Coordinate axes indicate the Radiator Panel coordinate system, for use in FEA modeling

Shaded Areas Higher Densidy Core

VCHP Reservoirs 6 PLs

Edge Member

Axial Tie Downs 2 PLs

X

Y

Heat Pipes 6 PLs



Finite Element Model of RadiatorFinite Element Model of Radiator

X

End Member

End Fully Restrained Bracket, 2 PLs

Tie Downs, 2 PLs

Z

Y

Heat Pipes Bolted to Patch-Plate, 6 PLs


Isometric View of Radiator FEA ModelIsometric View of Radiator FEA Model



Launch Load EnvironmentLaunch Load Environment• Primary structure loads

– Static Equivalent• Acceleration loads from Radiator Level-IV LAT-SS-00394-1 (3/5/03)

– X-direction (transverse): ±3.375 g, – Y-direction (thrust): ± 8.5 g, – Z-direction (normal): ± 1.25 (1.7g + AF)

– Sinusoidal Vibration• Preliminary load cycle results indicate accelerations are enveloped by current specification limits

• Random vibration Acoustic loads– Finite element vibro-acoustic analysis

performed to define 3-sigma static-equivalent acceleration due to acousticloads on the Radiator panel

– Acoustic spectrum from RadiatorLevel-IV Spec

• Normal Load Factor = 25g x 1.2 (MUF) = 30g

– Revised Acoustic Levels (Fig.) producelower load factors

Static-Equivalent Accelerations under Static-Equivalent Accelerations under Launch Environment (Panel Coords) Launch Environment (Panel Coords)


Axial (Y) Transverse (X) Normal (Z)

8.5 g 5.1 g 30 g

Change in Acoustic Levels from PDRChange in Acoustic Levels from PDR

Acoustic Qual Levels (Old vs New)

90

95

100

105

110

115

120

125

130

135

140

10 100 1000 10000

Frequency (Hz)

So

un

d P

ress

ure

Lev

el (

db

)

Old

New



Revised Launch Load EnvironmentRevised Launch Load Environment

• Revised Acoustic Loads analysis– Single support system at radiator CG– Reactive loads indicate lower normal loads but higher in-plane loads

Reactions Power Spectral Density

0

500

1000

1500

2000

2500

3000

3500

4000

4500

10 100 1000

Frequency (Hz)

Fo

rce

^2

/Hz

FxFyFz

Mode 1 2 3 4 5 6 7f (Hz) 61.6 66.8 92.0 112.8 118.1 132.5 136.8



Revised Launch Load EnvironmentRevised Launch Load Environment

• Revised Acoustic Environment produces lower normal loads, but higher in-plane loads

• Stress analysis of the Radiator under the new combined load factors indicates somewhat smaller margins at all locations

Load Environment Gx Gy Gz

Acoustic 8.06 3.71 14.10Static-Equivalent Lf 3.38 8.50 1.70

Combined Load Factors 8.73 9.27 19.75



Modal Analysis, First 5 Stowed FrequenciesModal Analysis, First 5 Stowed Frequencies

• All stowed frequencies are above the 50 Hz requirement

No Shear Deformation

Including Shear

Deformation

Mode Frequency Frequency Mode Shape No. (HZ) (HZ) 1 62.4 61.6 1st YZ Bending Mode 2 70.5 66.8 1st XZ Bending Mode 3 93.6 92.0 1st Twisting Mode 4 118.9 112.8 2nd YZ Bending Mode 5 125.6 118.1 2nd Twisting Mode


Radiator First Five Natural FrequenciesRadiator First Five Natural Frequencies



Panel Mode ShapesPanel Mode Shapes

Normal Mode 1, fNormal Mode 1, f11 = 61.6 Hz, = 61.6 Hz,

11stst YZ Bending Mode YZ Bending Mode


11stst XZ Bending Mode XZ Bending Mode



Panel Mode ShapesPanel Mode Shapes


11stst Twisting Mode Twisting Mode

Mode 4, fMode 4, f44 = 112.8 Hz, = 112.8 Hz,

22ndnd YZ Bending Mode YZ Bending Mode


22ndnd Twisting Mode Twisting Mode



Radiator Deformed Shape Under Launch Loads

Deformed Shape Under Launch Loads

Max Normal Disp = 1.8 mm



Stress Analysis Results—Face Sheet MarginsStress Analysis Results—Face Sheet Margins

• Facesheet stress analysis indicates positive margins of safety for all high-stress regions• Facesheet material properties

– Material: 6061-T6 aluminum (Top: 0.060” thk, Btm: 0.030” thk)– Ftu = 296 MPa (43 ksi)– Fty = 255 MPa (37 ksi)

MSy = Fty/(1.25 i) –1

MSu = Ftu/(1.4 i) –1

Facesheet Stresses and Margins of SafetyFacesheet Stresses and Margins of Safety

Panel Location Elem Sxx Syy Sxy Seff MSy MSu Failure Location ( Pa) ( Pa) ( Pa) ( Pa) (FS=1.25) (FS=1.4) Mode

(ksi) (ksi) (ksi) (ksi)Near Brackt (HDC) 34.49 17.69 7.07 32.29 4.9 5.1 Tension

711 5.00 2.57 1.03 4.68At Brackt (Dblrs) 22.69 17.54 6.10 23.16 7.8 8.1 Tension

709 3.29 2.54 0.89 3.36FWD Cut-out region 26.62 2.13 3.78 26.45 6.7 7.0 Tension

315 3.86 0.31 0.55 3.84At Tie-Down 19.99 24.52 0.33 22.60 7.3 7.6 Tension

4660 2.90 3.56 0.05 3.28Aft Sq. hole 14.53 28.45 0.08 24.64 6.2 6.4 Tension

4915 2.11 4.13 0.01 3.57S/A hole region 19.57 -0.32 0.29 19.73 9.3 9.7 Tension

4638 2.84 -0.05 0.04 2.86Edge, Resvr_Cut_out 14.36 1.18 2.55 14.49 13.1 13.6 Tension

5946 2.08 0.17 0.37 2.10



Stress Analysis Results—Core Shear MarginsStress Analysis Results—Core Shear Margins• Core shear stress analysis indicates positive margins of safety for all high-stress regions

– Basic Core Material: 5000 series aluminum• Fsu12 = 35 kPa (5 psi)• Fsu13 = 1379 kPa (200 psi) Ribbon Dir; Fsu23 = 758 kPa (110 psi)

– Hi_Den Core Material: 5000 series aluminum, density is ~2*basic core density• Fsu12 = 69 kPa (10 psi)• Fsu13 = 3.62 MPa (525 psi) Ribbon Dir; Fsu23 = 2.10 MPa (305 psi)

Bi-axial quadratic failure criterion:

MSu = 1/SQRT((Fs.yz/(Ks*Fsu13))^2 + (Fs.xz/(Ks*Fsu23))^2) -1; Ks=0.9

Core Stresses and Margins of SafetyCore Stresses and Margins of Safety

Panel Location Elem Sxz Syz MSu Failure ModeLocation (k Pa) (k Pa) (1.4)

(psi) (psi)FWD Supprt 1094.0 1293.5 0.02 Core Shear (Qx, Qy)HD + Doublrs 709 158.7 187.6FWD End Cut-outs 340.2 260.4 0.32 Core Shear (Qx, Qy)LD 315 49.3 37.8FWD Sq. hole Edge 246.2 148.2 0.88 Core Shear (Qx, Qy)LD 1825 35.7 21.5AFT Sq. hole Edge 409.1 68.4 0.19 Core Shear (Qx, Qy)LD 4753 59.3 9.9AFT Circ. hole Edge 126.5 17.1 2.84 Core Shear (Qx, Qy)LD 4634 18.3 2.5at Tie-Down 804.0 794.9 0.46 Core Shear (Qx, Qy)HD + Doublr 4660 116.6 115.3Res_Cut_Edge 171.5 91.2 1.73 Core Shear (Qx, Qy)LD 6145 24.9 13.2

LD = Basic core materialHD = High density core material



Stress Analysis Results—Heat Pipe MarginsStress Analysis Results—Heat Pipe Margins• Heat pipe stress analysis indicates positive margins of safety for all stressed regions

• Heat pipe material properties

– Material: 6063-T6 aluminum

– Ftu = 241 MPa (35 ksi); Fty = 214 MPa (31 ksi)

MSy = Fty/(1.25 i) –1

MSu = Ftu/(1.4 i) –1

Heat Pipe Stresses and Margins of SafetyHeat Pipe Stresses and Margins of Safety (includes 170 psi int. pressure)(includes 170 psi int. pressure)

Panel Location Elem Axial Mz My Tq Sx(pi) MSy MSuLoc (N) (N-m) (N-m) (N-m) (N) ( Pa) ( Pa) (1.25) (1.4)

(lb) (in-lb) (in-lb) (in-lb) (ksi) (ksi) (ksi) H-Pipe at bolted suppt -32.4 -1.9 -0.2 0.0 2.4 6.0 0.1 13.6 13.8Single flanged 6805 -7.3 -17.1 -1.4 0.0 0.4 0.9 0.0H Pipes S-Shape 54.2 -3.6 -0.2 -0.2 2.4 29.4 1.1 3.9 4.0Bent, Round 6810 12.2 -31.6 -1.7 -1.5 0.4 4.3 0.2H Pipes (no flange), -44.4 2.1 0.0 0.4 2.4 17.1 2.2 6.5 6.6junction of panel 6820 -10.0 18.9 -0.2 3.8 0.4 2.5 0.3H Pipes in Panel -418.4 -2.9 0.4 0.2 2.4 11.7 0.5 9.0 9.1Single Flange 6967 -94.1 -25.4 3.7 2.2 0.4 1.7 0.1Extension @ Resrvr 18.1 0.5 -0.1 0.5 9.3 9.3 4.4 4.0 10.2304 CRES Tube 6877 4.1 4.8 -0.7 4.5 1.4 1.3 0.6Extension Aluminum -43.9 -0.1 0.0 -0.1 3.5 2.6 0.3 14.1 14.2Round 6875 -9.9 -1.2 0.1 -0.5 0.5 0.4 0.0



Stress Analysis Results—Bolt/Insert MarginsStress Analysis Results—Bolt/Insert Margins• Bolt and insert analysis indicates positive margins of safety• Bolt material properties

– Material: CRSS A-286 stainless steel– Ftu = 1.103 GPa (160 ksi); Fty = 0.827 GPa (120 ksi)– Fsu = 0.655 GPa (95 ksi)

• Insert ultimate strengths (Estimated from existing tests)– 5/16”-24 UNF insert

• Pull-out = 6.47 kN (1454 lb)• Shear = 7.16 kN (1610 lb)

– 10-32 UNF insert• Pull-out = 3.56 kN (800 lb)• Shear = 4.79 kN (1077 lb)

MSy = Fty/(1.25 i) –1

MSu = Ftu/(1.4 i) –1Bolt and Insert Stresses and Margins of SafetyBolt and Insert Stresses and Margins of Safety

* Note: Factor of safety on Ultimate = 1.4, Yield = 1.25, Fittng factor = 1.15

Bolt Loads Bolt Margins* Insert Margins*Location Bolt Dia PreLoad Axial Shear MSu MSy Tension Shear

Size (mm) (kN) (kN) (kN) (1.4) (1.25) (1.4) (1.4)(in) (lb) (lb) (lb)

Brackets 7.94 15.1 3.9 0.9 1.28 0.91 0.03 3.684 bolts 5/16"-24 0.3125 3400.0 873.9 213.6Tie-Down 4.83 5.1 0.8 0.4 0.53 0.29 1.69 8.364 bolts No. 10-32 0.190 1151.3 184.7 80.0



Summary and Further WorkSummary and Further Work• Summary

– Preliminary analysis indicates the revised Acoustic spectrum produce smaller loads than the assumed dynamic load factor of 30g

– Positive stress margins obtained for sandwich panel, bolts, inserts and heat pipes

– Stowed frequency requirements satisfied

– Dynamic envelope exceeds the spec req.

• Further Work

– Update analyses using static-equivalent loads from CDR CLA results

– Protoflight qualification testing will verify analysis results and models

– Detail design of brackets and tie-downs not completed yet

– Follow-on analysis to be completed• Structural assessment of integration and transportation loads – expected to be enveloped by the

launch load environment • Shock Analysis• Random Vibration Analysis (in view of lower acoustic loads)• On-orbit thermal distortion analysis• Fatigue analysis

Documents

GLAST Large Area Telescope: Mechanical Systems Peer Review 27 March 2003