GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
GLAST Large Area Telescope:
Gamma-ray Large
Area Space
Telescope
Mechanical Systems Peer Review
27 March 2003
Radiator Structural Design
Parviz Sharifi
Lockheed Martin
Structural Analysis
parviz.sharifi@lmco.com
Section 4.2 - Mechanical Systems Radiator Assy
1
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Radiator Level IV Design and Structural Requirements
Parag. Parameter
3.3.3 Stiffness
3.3.4 Dynamic Envelope
Requirement
Design
Margin
Comply
> 50 Hz
> 60 Hz
+10 Hz
Shown in ICD
± 1.8 mm (Launch Loads)
± 3.2 mm (2mm misalign.)
-2.2 mm
Y
N (TBD),
working on
ICD
Core Shear MSu = 0.02;
Gx = 5.1 g, Gy = 30 g, and
Y (insert
Brckt Inserts MSu = 0.03;
Gz = 8.5 g
test TBD)
Heat Pipes MSy = 0.39
3.3.6 Static Loads
See Table 8
(TBR)
3.3.8 Acoustic Loads
See Table 9
Included above
3.3.9 Shock Loads
See Table 10
TBD
3.3.10 Sinusoidal Vibration
See Table 11
(TBR)
Enveloped by above
Based on:
Loads included in above
margins
Ver.
Method
A, T
A, T
A
Y
A, T
TBD
TBD
A, Test at
Obs. Level
Enveloped by Static
Loads
Y
A, T
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
Section 4.2 - Mechanical Systems Radiator Assy
2
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Finite 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 zerolength springs
Model Size:
– Nodes 4840
– Shell elements: 4284
– Beam elements: 564
– Spring Elements: 38
Analysis Weight: 36.0 kg (79.3lb) per
radiator
Edge Member
VCHP Reservoirs 6 PLs
Axial Tie Downs
2 PLs
Y
X
Shaded Areas
Higher Densidy
Core
Heat Pipes 6 PLs
Radiator FEA Mesh
Coordinate axes indicate the Radiator Panel
coordinate system, for use in FEA modeling
Section 4.2 - Mechanical Systems Radiator Assy
3
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Finite Element Model of Radiator
End Member
Tie Downs, 2 PLs
Z
Y
X
Heat Pipes Bolted to
Patch-Plate, 6 PLs
End Fully Restrained
Bracket, 2 PLs
Coordinate axes indicate the Radiator Panel
coordinate system, for use in FEA modeling
Isometric View of Radiator FEA Model
Section 4.2 - Mechanical Systems Radiator Assy
4
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Launch Load Environment
Primary structure loads
– Static Equivalent
•
–
Sinusoidal Vibration
•
•
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)
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 staticequivalent acceleration due to acoustic
loads on the Radiator panel
– Acoustic spectrum from Radiator
Level-IV Spec
•
–
Normal Load Factor = 25g x 1.2 (MUF) = 30g
Revised Acoustic Levels (Fig.) produce
lower load factors
Axial (Y)
8.5 g
Transverse (X)
5.1 g
Normal (Z)
30 g
Acoustic Qual Levels (Old vs New)
140
Sound Pressure Level (db)
•
135
130
125
120
115
110
105
Old
100
New
95
90
10
100
1000
10000
Frequency (Hz)
Static-Equivalent Accelerations under
Launch Environment (Panel Coords)
Change in Acoustic Levels from PDR
Coordinate axes indicate the Radiator Panel
coordinate system, for use in FEA modeling
Section 4.2 - Mechanical Systems Radiator Assy
5
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Revised 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
4500
4000
Fx
Fy
Fz
3500
3000
Force^2/Hz
•
2500
2000
1500
1000
500
0
10
100
1000
Frequency (Hz)
Mode
f (Hz)
1
61.6
2
66.8
3
92.0
4
112.8
5
118.1
6
132.5
7
136.8
Section 4.2 - Mechanical Systems Radiator Assy
6
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Revised Launch Load Environment
•
Revised Acoustic Environment produces lower normal loads, but higher
in-plane loads
Load Environment
Acoustic
Static-Equivalent Lf
Combined Load Factors
•
Gx
8.06
3.38
8.73
Gy
3.71
8.50
9.27
Gz
14.10
1.70
19.75
Stress analysis of the Radiator under the new combined load factors
indicates somewhat smaller margins at all locations
Section 4.2 - Mechanical Systems Radiator Assy
7
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Modal Analysis, First 5 Stowed Frequencies
•
All stowed frequencies are above the 50 Hz requirement
No Shear
Deformation
Mode
No.
1
2
3
4
5
Frequency
(HZ)
62.4
70.5
93.6
118.9
125.6
Including
Shear
Deformation
Frequency
(HZ)
61.6
66.8
92.0
112.8
118.1
Mode Shape
1st YZ Bending Mode
1st XZ Bending Mode
1st Twisting Mode
2nd YZ Bending Mode
2nd Twisting Mode
Radiator First Five Natural Frequencies
Coordinate axes indicate the Radiator Panel
coordinate system, for use in FEA modeling
Section 4.2 - Mechanical Systems Radiator Assy
8
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Panel Mode Shapes
Normal Mode 1, f1 = 61.6 Hz,
1st YZ Bending Mode
Normal Mode 2, f2 = 66.8 Hz,
1st XZ Bending Mode
Section 4.2 - Mechanical Systems Radiator Assy
9
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Panel Mode Shapes
Mode 4, f4 = 112.8 Hz,
2nd YZ Bending Mode
Normal Mode 3, f3 = 92.0 Hz,
1st Twisting Mode
Normal Mode 5, f5 = 118.1 Hz,
2nd Twisting Mode
Section 4.2 - Mechanical Systems Radiator Assy 10
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Radiator Deformed Shape Under Launch Loads
Max Normal Disp = 1.8 mm
Deformed Shape Under Launch Loads
Section 4.2 - Mechanical Systems Radiator Assy 11
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Stress 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)
Panel Location
Elem
Location
Near Brackt (HDC)
711
At Brackt (Dblrs)
709
FWD Cut-out region
315
At Tie-Down
4660
Aft Sq. hole
4915
S/A hole region
4638
Edge, Resvr_Cut_out
5946
MSy = Fty/(1.25 si) –1
MSu = Ftu/(1.4 si) –1
Sxx
( Pa)
(ksi)
34.49
5.00
22.69
3.29
26.62
3.86
19.99
2.90
14.53
2.11
19.57
2.84
14.36
2.08
Syy
( Pa)
(ksi)
17.69
2.57
17.54
2.54
2.13
0.31
24.52
3.56
28.45
4.13
-0.32
-0.05
1.18
0.17
Sxy
( Pa)
(ksi)
7.07
1.03
6.10
0.89
3.78
0.55
0.33
0.05
0.08
0.01
0.29
0.04
2.55
0.37
Seff
MSy
MSu
Failure
( Pa) (FS=1.25) (FS=1.4) Mode
(ksi)
32.29
4.9
5.1
Tension
4.68
23.16
7.8
8.1
Tension
3.36
26.45
6.7
7.0
Tension
3.84
22.60
7.3
7.6
Tension
3.28
24.64
6.2
6.4
Tension
3.57
19.73
9.3
9.7
Tension
2.86
14.49
13.1
13.6
Tension
2.10
Facesheet Stresses and Margins of Safety
Section 4.2 - Mechanical Systems Radiator Assy 12
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Stress 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)
Panel Location
FWD Supprt
HD + Doublrs
FWD End Cut-outs
LD
FWD Sq. hole Edge
LD
AFT Sq. hole Edge
LD
AFT Circ. hole Edge
LD
at Tie-Down
HD + Doublr
Res_Cut_Edge
LD
Elem
Location
709
315
1825
4753
4634
4660
6145
Sxz
(k Pa)
(psi)
1094.0
158.7
340.2
49.3
246.2
35.7
409.1
59.3
126.5
18.3
804.0
116.6
171.5
24.9
Syz
(k Pa)
(psi)
1293.5
187.6
260.4
37.8
148.2
21.5
68.4
9.9
17.1
2.5
794.9
115.3
91.2
13.2
MSu
(1.4)
Failure Mode
0.02
Core Shear (Qx, Qy)
0.32
Core Shear (Qx, Qy)
0.88
Core Shear (Qx, Qy)
0.19
Core Shear (Qx, Qy)
2.84
Core Shear (Qx, Qy)
0.46
Core Shear (Qx, Qy)
1.73
Core Shear (Qx, Qy)
Core Stresses and Margins of Safety
Bi-axial quadratic failure criterion:
MSu = 1/SQRT((Fs.tyz/(Ks*Fsu13))^2 + (Fs.txz/(Ks*Fsu23))^2) -1; Ks=0.9
LD = Basic core material
HD = High density core material
Section 4.2 - Mechanical Systems Radiator Assy 13
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Stress 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)
Panel Location
H-Pipe at bolted suppt
Single flanged
H Pipes S-Shape
Bent, Round
H Pipes (no flange),
junction of panel
H Pipes in Panel
Single Flange
Extension @ Resrvr
304 CRES Tube
Extension Aluminum
Round
Elem
Loc
6805
6810
6820
6967
6877
6875
Axial
(N)
(lb)
-32.4
-7.3
54.2
12.2
-44.4
-10.0
-418.4
-94.1
18.1
4.1
-43.9
-9.9
Mz
(N-m)
(in-lb)
-1.9
-17.1
-3.6
-31.6
2.1
18.9
-2.9
-25.4
0.5
4.8
-0.1
-1.2
My
(N-m)
(in-lb)
-0.2
-1.4
-0.2
-1.7
0.0
-0.2
0.4
3.7
-0.1
-0.7
0.0
0.1
Tq
(N-m)
(in-lb)
0.0
0.0
-0.2
-1.5
0.4
3.8
0.2
2.2
0.5
4.5
-0.1
-0.5
Sx(pi)
s
t
MSy
(N)
( Pa) ( Pa) (1.25)
(ksi)
(ksi)
(ksi)
2.4
6.0
0.1
13.6
0.4
0.9
0.0
2.4
29.4
1.1
3.9
0.4
4.3
0.2
2.4
17.1
2.2
6.5
0.4
2.5
0.3
2.4
11.7
0.5
9.0
0.4
1.7
0.1
9.3
9.3
4.4
4.0
1.4
1.3
0.6
3.5
2.6
0.3
14.1
0.5
0.4
0.0
MSu
(1.4)
13.8
4.0
6.6
9.1
10.2
14.2
Heat Pipe Stresses and Margins of Safety
(includes 170 psi int. pressure)
MSy = Fty/(1.25 si) –1
MSu = Ftu/(1.4 si) –1
Section 4.2 - Mechanical Systems Radiator Assy 14
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Stress 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)
Bolt Loads
Location
Brackets
4 bolts
Tie-Down
4 bolts
Bolt
Size
Dia PreLoad
(mm)
(kN)
(in)
(lb)
7.94
15.1
5/16"-24 0.3125
3400.0
4.83
5.1
No. 10-32 0.190
1151.3
Bolt Margins*
Axial Shear
(kN)
(kN)
(lb)
(lb)
3.9
0.9
873.9 213.6
0.8
0.4
184.7
80.0
Insert Margins*
MSu
MSy
Tension Shear
(1.4)
(1.25)
(1.4)
(1.4)
1.28
0.91
0.03
3.68
0.53
0.29
1.69
8.36
* Note: Factor of safety on Ultimate = 1.4, Yield = 1.25, Fittng factor = 1.15
MSy = Fty/(1.25 si) –1
MSu = Ftu/(1.4 si) –1
Bolt and Insert Stresses and Margins of Safety
Section 4.2 - Mechanical Systems Radiator Assy 15
GLAST LAT Project
DOE/NASA Mechanical Systems Peer Review, March 27, 2003
Summary 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
Section 4.2 - Mechanical Systems Radiator Assy 16