NASA TECHNOLOGY DAYS

1
NASA TECHNOLOGY DAYS

• Structural Analysis of a 50 cm Diameter Open-back
  Triangular Cell Beryllium Mirror in a Cryogenic
  Environment

2
SBMD Structural Analysis

• PATRAN is the Pre and Post-Processor
• NASTRAN is the Analyzer
• Thermal analysis predicts negligible temperature
  gradients
• Ambient analysis results agree with measured data
• Cryogenic low frequency surface error analysis
  results agree with measured data

3
SBMD Structural Analysis

• High frequency surface error (print-thru or
  dimpling) discrepancies between analysis and
  measured data is being investigated.
• Numerous CTE variation attempts did not
  accurately predict print-thru

4
NASTRAN Model Description
Total model has 10321 Grids and 9975 elements
Mirror model has 9195 Grids and 8970 elements
Mirror surface has 5051 Grids and 4945 elements
5
-1G Vertical Gravity Sag
Legend units are inches
6
-1G Vertical Gravity Sag
7
Ambient RoC change
Legend units are inches
8
Ambient RoC change
9
Ambient RoC change
P-V 18 microns, 0 Zernikes removed
P-V 0.87 microns, piston, tip and tilt removed
P-V 0.203 microns, power removed
Legend units are inches
10
Ambient RoC change
P-V 0.074 microns 42 Zernikes removed
P-V 0.135 microns 36 Zernikes removed
Legend units are inches
11
Cryogenic Cases Investigated

• Ambient-30K nominal CTE (5.13ppm/K)
• Ambient-30K 1 radial CTE variation on facing
• Ambient-30K 3 CTE increase across facing
• Ambient-30K ?3 facing CTE coupled with ?3 core
  CTE
• Ambient-30K ?3 facing CTE coupled with ?3 core
  depth CTE
• Ambient-Predicted temperatures Nominal CTE

12
Ambient-30K nominal CTE (5.13ppm/K)
13
Ambient-30K 3 CTE increase across facing
14
Ambient-30K 3 increased facing CTE coupled with
3 decreased core CTE
15
Thermal Analysis
16
XRCF Mirror Testing Thermal Analysis
Tim Page/ED26 Steve Sutherlin/Sverdrup
17
XRCF Mirror Testing Integrated Analysis
FINITE ELEMENT MODEL NASTRAN/PATRAN
Optical Analysis
Deformed Geometry Grid Points Elements
Geometry Grid Points Elements
Temperatures
Thermal Desktop
Thermal Desktop
SINDA
Radiation Conductors Free-Molecular
Transfer Nodal Capacitance Conduction Network
Temperatures
18
XRCF Mirror Testing Thermal Analysis
19
XRCF Mirror Testing Thermal Analysis