1. Space Frame Structures for SNAP: Another secondary structure…
Bruce C. Bigelow
University of Michigan
Department of Physics
9/16/04

2. Secondary Structure Motivations:
Minimize pupil obscuration by secondary structures
Increase first telescope resonance frequency
Minimize structure mass

3. Secondary Structure

4. Secondary Structure FEA model features: TMA-65 optics
Secondary structures only
Design is not optimized
Light-weighted ULE secondary – 9.7 kg
6 actuators - (MZT for mass) – 6 kg total
Total mass numbers in table include mirror and actuator mass
CF tubing secondary cage
M55J composite tubes, 1-2mm wall thickness typical
Dynamic analyses only so far
Ring elevation is approximate, relative to primary
Constant diameter tubes, wall thicknesses

5. Secondary Structure
Trial 9, ring at 2.85m elev.

6. Secondary Structure
Trial
ring elev
hex dia
hex wall
ring width
ring ht
ring walls
vane dia
vane wall
cage dia
cage wall
tot mass f1 f3 M mm kg Hz 1
2.85 60
100 25
28.3
40.0
59.0 2
126
28.9
47.0
58.0 3
34.3
53.0 4
50.0 5
39.7 6
40.4
60.0
74.0 7 30
40.7
88.0 8
150
41.5
66.0 9
47.4
69.0 10
46.8
67.0 11
45.6
63.0 12 75
43.2
62.0 13
2.65
28.6
57.0 14
72.0 15
70.5
72.3 16
2.00
38.0
52.0
54.0 17
38.5

7. Blue/green hexapod struts are outside of CA
Secondary Structure
Blue/green hexapod struts are outside of CA

8. Secondary Structure

9. Secondary Structure
Trial 15, ring at 2.65m height

10. Secondary Structure
Trial 16, ring at 2.0m elev.

11. Secondary Structure Conclusions: Yet another structure option…
Smallest secondary obscuration to date?
Natural frequencies are easily tuned up or down from 70 Hz