GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy1 GLAST Large Area Telescope: Mechanical Systems Peer Review 27 March 2003 Radiator Structural Design Parviz Sharifi Lockheed Martin Structural Analysis Gamma-ray Large Area Space Telescope

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy2 Radiator Level IV Design and Structural Requirements Based on:Radiator Level IV Design Specification, LAT-SS 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy3 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 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 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy4 Finite 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 Coordinate axes indicate the Radiator Panel coordinate system, for use in FEA modeling Isometric View of Radiator FEA Model

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy5 Launch Load Environment Primary structure loads –Static Equivalent Acceleration loads from Radiator Level-IV LAT-SS (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 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 Static-Equivalent Accelerations under Launch Environment (Panel Coords) Coordinate axes indicate the Radiator Panel coordinate system, for use in FEA modeling Axial (Y)Transverse (X)Normal (Z) 8.5 g5.1 g30 g Change in Acoustic Levels from PDR

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy6 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy7 Revised 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy8 Modal Analysis, First 5 Stowed Frequencies All stowed frequencies are above the 50 Hz requirement Coordinate axes indicate the Radiator Panel coordinate system, for use in FEA modeling Radiator First Five Natural Frequencies

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy9 Panel Mode Shapes Normal Mode 1, f 1 = 61.6 Hz, 1 st YZ Bending Mode Normal Mode 2, f 2 = 66.8 Hz, 1 st XZ Bending Mode

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy10 Panel Mode Shapes Normal Mode 3, f 3 = 92.0 Hz, 1 st Twisting Mode Mode 4, f 4 = Hz, 2 nd YZ Bending Mode Normal Mode 5, f 5 = Hz, 2 nd Twisting Mode

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy11 Radiator Deformed Shape Under Launch Loads Deformed Shape Under Launch Loads Max Normal Disp = 1.8 mm

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy12 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) MSy = Fty/( 1.25  i ) –1 MSu = Ftu/( 1.4  i ) –1 Facesheet Stresses and Margins of Safety

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy13 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) 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 Safety LD = Basic core material HD = High density core material

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy14 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) MSy = Fty/( 1.25  i ) –1 MSu = Ftu/( 1.4  i ) –1 Heat Pipe Stresses and Margins of Safety (includes 170 psi int. pressure)

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy15 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 = GPa (160 ksi); Fty = GPa (120 ksi) –Fsu = 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 ) –1 Bolt and Insert Stresses and Margins of Safety * Note: Factor of safety on Ultimate = 1.4, Yield = 1.25, Fittng factor = 1.15

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems Radiator Assy16 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