MAXIM Periscope Module

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MAXIM Periscope Module

• Structural Analysis
• Jeff Bolognese
• 25 April 2003

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Structural Analysis Outline

• Structural Analysis Goals
• Finite Element Models
• Analysis Results
• Issues and Future Work
• Conclusions
• Detailed Analysis Results
• Mirror Analyses
• Thermal Deformation
• 20g Quasi Static Load Stresses
• Optical Bench Analyses
• Normal Modes Analysis
• Thermal Distortion
• Gravity Loading
• 1 DOF Actuation

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Analysis Goals

• For Mirror and Mount
• Mass properties of lightweight ULE mirror
• Fixed base dynamics assessment
• Minimize thermal deformations of mirror surface
• Ti stresses lt yield for 20g loading
• ULE stresses small for 20g loading
• For Optical Bench
• Fundamental Frequency gt 50 Hz
• Sensitivity of bench to thermal distortion
• Gravity sag distortions
• Bench distortions due to 1 DOF actuator actuation
• Material trade studies

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Finite Element Models

• MSC/NASTRAN format
• Optics model
• ULE used for detailed optics model
• 3.5mm face sheet
• 2.5mm back sheet
• 1.27mm thick core
• 20mm cell size (from vertex to vertex)
• Ti for flexures
• Analysis mass of optic 2.1 Kg
• Optical bench model
• Titanium for mounts and flexures
• Invar for bench
• Lumped masses for optics
• Simplified representation of optics mounts
• 2D representation of 3d bench
• Plate elements with bars for stiffeners
• Analysis mass 68.8 Kg

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Mirror FEM
Mirror Face
Mirror Back
3pt Ti Flexure Mount
Optic w/Face Sheet Removed
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Optical Bench FEM
Daughter Benches
Main Bench
Fixed Mount
Flexure
Simplified Optics Mounts
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Mirror Analysis Summary
1cZ Mirror Deformations (mm)
20gY Mirror Back Stresses (MPa)
Mirror First Mode 278 Hz
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Optical Bench Analysis Summary
Deformation Due to Single Actuation
Deformation Due to 1c Y Gradient
Deformation Due to 1g Z
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Issues and Future Work

• Further optimization of bench design is necessary
  to minimize weight and increase fundamental
  frequency
• Better understanding of thermal environment to
  quantify allowable material CTE
• More detailed modeling of the mirrors and mounts
  necessary to understand overall mount stiffness
  as well as quantify local stresses and
  deformations
• Interfaces between mount and mirror will require
  specific attention
• More detailed analysis of daughter bench
  flexures to balance stiffness vs. potential to
  impose distortions to benches during 1 DOF
  actuations
• Preliminary analyses show coupling between
  actuations and bench distortions which could
  complicate control of optics pointing
• Better understanding of which displacements of
  optics can be corrected by mechanisms is needed
  to be folded into analysis efforts. Calculated
  displacements should then be considered to
  determine if, for flight load cases, mechanisms
  have the range to correct the errors.
• More detailed, 3D model of bench is required to
  fully capture thermal deformations and the
  complexities of optical mount interfaces when
  predicted flight loads are applied.
• Quantify jitter sources and verify that they are
  not pose a pointing issue due to dynamic coupling
  with structure.

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Conclusions

• Proposed design looks promising but requires
  further analysis to verify that thermal control
  is adequate and mechanisms robust enough to
  correct for launch shifts and on-orbit
  transients.
• Still lots of analysis work to be done!

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Backup Slides

• TBD

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Mirror and Mount ThermalDeformations
Plot showing Z translations of mirror surface (in
mm) after rigid body motion effects are removed
1c Bulk Temp Increase
1c X Gradient
1c Y Gradient
1c Z Gradient
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Mirror and Mount 20g Stresses
20 G Y Loading
20 G X Loading
20 G Z Loading
Mirror Back Stresses (in MPa)
Mirror Flexure Stresses (in MPa)
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Optical Bench Fixed Base Dynamics
Bench Mode 1 49 Hz
Bench Mode 3 65 Hz
Bench Mode 2 56 Hz
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Bench Bulk Thermal Deformations
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Bench 1c X Gradient Deformations
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Bench 1c Y Gradient Deformations
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Bench 1g X Deformations
1g X Deformed Plot
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Bench 1g Y Deformations
1g Y Deformed Plot
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Bench 1g Z Deformations
1g Z Deformed Plot
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.001mm Motion of Z Side Daughter Board Actuator
Deformation Due to .001mm Y Motion of Z Side
Actuator
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.001mm Motion of -Z Side Daughter Board Actuator
Deformation Due to .001mm Y Motion of -Z Side
Actuator
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.001mm Motion of Both Daughter Board Actuators
Deformation Due to .001mm Y Motion of Both
Actuators