GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy1 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 Gamma-ray Large Area Space Telescope

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy2 Driving Structural Requirements Based on:X-LAT Plate Performance Specification, LAT-TD 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy3 Driving Design Requirements Based on:X-LAT Plate Performance Specification, LAT-TD 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy4 Driving Miscellaneous Requirements Based on:X-LAT Plate Performance Specification, LAT-TD 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy5 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy6 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 ( 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.

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy7 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy8 X-LAT Panel Assembly Radiator Bracket alignment Pin Hole X-LAT Plate Bolt hole Interface to Mid-Plate Heat Pipe Interface to Radiator flange and EMI skirt Rivet Hole for assembly of heat pipe to X-LAT plate Spacer Interface Hole Lifting Interface Hole, 4X

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy9 Mid-Plate #6-32 Interface Holes (both sides) Mid-Plate Interface To X-LAT Plate (both sides) Interface Spacer Holes, 20X Lift Pin Holes, 4X

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy10 X-LAT Assembly (Without Heat Pipes) X-LAT Plate Mid-Plate X-LAT/Mid-Plate Interface

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy11 Mid-Plate Handling Mid-Plate sling is designed to attach to the -Z surface

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy12 X-LAT Panel Handling X-LAT sling is designed to pick up one X-LAT panel from the -Z surface

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy13 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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy14 X-LAT First Mode – 97.7 Hz

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy15 X-LAT Plate Stress Analysis (2 of 2) Loads –Highest load on plate is random vibration load –Calculate 3  random vibration load factor in g using Miles’ equation => 3*sqrt((  /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

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy16 X-LAT Plate Stress Analysis Results Load CaseStress (KSI) Yield Safety Margin Ultimate Safety Margin 1: 74.4 g Normal Load : 74.4 g In-Plane Load Stress for 74.4 g normal load

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy17 X-LAT Drawing Tree

GLAST LAT ProjectDOE/NASA Mechanical Systems Peer Review, March 27, 2003 Section Mechanical Systems X-LAT Assy18 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