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GLAST Large Area Telescope: Mechanical Systems Peer Review 27 March 2003 Section 4.5 X-LAT Design and Structural Analysi

Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope: Mechanical Systems Peer Review 27 March 2003 Section 4.5 X-LAT Design and Structural Analysis Larry Sokolsky Lockheed Martin Advanced Technology Center Staff Engineer larry.sokolsky@lmco.com.

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GLAST Large Area Telescope: Mechanical Systems Peer Review 27 March 2003 Section 4.5 X-LAT Design and Structural Analysi

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  1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Mechanical Systems Peer Review 27 March 2003 Section 4.5 X-LAT Design and Structural Analysis Larry Sokolsky Lockheed Martin Advanced Technology Center Staff Engineer larry.sokolsky@lmco.com

  2. Driving Structural Requirements Based on: X-LAT Plate Performance Specification, LAT-TD-01240-D2, Draft, Dated 6 Mar 2003 X-LAT Plate Assy Source Control Drawing, LAT-DS-01247, Draft, Dated 7 Mar 2003 Mid-Plate Assy Source Control Drawing, LAT-DS-01257, Draft, Dated 7 Mar 2003 Verification Methods A: Analysis, T: Test, I: Inspection

  3. Driving Design Requirements Based on: X-LAT Plate Performance Specification, LAT-TD-01240-D2, Draft, Dated 6 Mar 2003 X-LAT Plate Assy Source Control Drawing, LAT-DS-01247, Draft, Dated 7 Mar 2003 Mid-Plate Assy Source Control Drawing, LAT-DS-01257, Draft, Dated 7 Mar 2003 Verification Method I: Inspection

  4. Driving Miscellaneous Requirements Based on: X-LAT Plate Performance Specification, LAT-TD-01240-D2, Draft, Dated 6 Mar 2003 X-LAT Plate Assy Source Control Drawing, LAT-DS-01247, Draft, Dated 7 Mar 2003 Mid-Plate Assy Source Control Drawing, LAT-DS-01257, Draft, Dated 7 Mar 2003 Verification Methods A: Analysis T: Test I: Inspection

  5. X-LAT Plate Design Drivers • Provide cooling path to LAT electronics boxes • Must have sufficient margin to cool boxes if one heat pipe fails • Act as EMI –Z closeout • Include adjustable spacers to allow for tolerance build-up in box height • Allow for lateral slip at spacer locations to limit stress to boxes • Accommodate attachment to thermal link to Grid electronics boxes • Have removable plates for easier box servicing • Make side plate/heat pipe assemblies rotationally symmetric so one spare can function in both locations • Survive inertial and acoustic loading from launch

  6. X-LAT Plate Design (1 of 2) • Plate is not structural (no need for honey comb). Plate thickness is sized for thermal considerations • Mid-plate 4.76 mm (0.1875 in) thick • X-LAT (side) plates are 3.18 mm (0.125 in) thick • Material is aluminum 6061-T6 • Heat pipes are bonded to plates with NuSil CV-2942 conductive RTV and riveted every 50.9 mm (2 in) • The two X-LAT plates are bolted to the mid-plate at SLAC with #6 bolts every 25.4 mm (1.0 In) to provide a thermally adequate joint between the plates • X-LAT assembly is bolted to the EMI skirt around the perimeter with #8 bolts. Oversized holes allow for adjustment. • The X-LAT assembly is pinned to the grid attachment bracket to ensure alignment of 3-way heat pipe interface.

  7. X-LAT Plate Design (2 of 2) • An alignment template will be produced along with the X-LAT plates and mid-plate to allow installation of the electronics boxes in the correct position and to allow integration of the X-LAT assembly. • Spacers adjustable in the Z direction are bolted to the X-LAT plate at the corners of the electronics boxes. These spacers allow for tolerance build-up in the Z direction between the boxes and the X-LAT plate, and slippage in the X-Y direction to prevent excess force build-up as Grid flexes under launch loading

  8. X-LAT Panel Assembly Lifting Interface Hole, 4X X-LAT Plate Spacer Interface Hole Bolt hole Interface to Mid-Plate Rivet Hole for assembly of heat pipe to X-LAT plate Heat Pipe Interface to Radiator flange and EMI skirt Radiator Bracket alignment Pin Hole

  9. Mid-Plate Interface Spacer Holes, 20X Lift Pin Holes, 4X Mid-Plate Interface To X-LAT Plate (both sides) #6-32 Interface Holes (both sides)

  10. X-LAT Assembly (Without Heat Pipes) X-LAT Plate Mid-Plate X-LAT Plate X-LAT/Mid-Plate Interface

  11. Mid-Plate Handling • Mid-Plate sling is designed to attach to the -Z surface

  12. X-LAT Panel Handling • X-LAT sling is designed to pick up one X-LAT panel from the -Z surface

  13. X-LAT Plate Stress Analysis (1 of 2) • Finite Element model of X-LAT plate assembly was built • Model was simply supported at the edges, and constrained in the Z direction only at each of the spacer locations • Factors of safety (tested hardware) • Yield F.S. = 1.1 • Ultimate F.S. = 1.4 • Material strength – Al 6061-T6 • Yield 36 ksi • Ultimate 42 ksi • Modal analysis run – first mode = 97.7 hz

  14. X-LAT First Mode – 97.7 Hz

  15. X-LAT Plate Stress Analysis (2 of 2) • Loads • Highest load on plate is random vibration load • Calculate 3s random vibration load factor in g using Miles’ equation => 3*sqrt((p/2)*PSD*Q*f)), where: • PSD at first resonant frequency is 0.08 g**2/Hz (source – LAT-TD-01240) • Q = 50 (1% damping) • F = 97.7 Hz • Load cases run • 74.4 g acceleration normal to plate • 74.4 g g lateral in plane of plate • Load case not run • Load applied as Grid-mounted electronics boxes move normal to plate relative to EMI skirt. • Needs to be run at LAT level

  16. X-LAT Plate Stress Analysis Results Stress for 74.4 g normal load

  17. X-LAT Drawing Tree

  18. Further Work • Update design and analysis to reflect finalized ICD, specification, and design • Verify final load case once results from coupled LAT stress analysis is complete • Perform heat pipe stress analysis for combined loads • Optimize local plate thickness to accommodate thermal requirements while minimizing mass

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