TABLE OF CONTENTS In this section, the critical component technologies identified earlier are explored in more depth through a combination of technical explanations of progress and references to the source material. Recent experiment achievements reported in Table 2 provide a context for this section. Much progress has been made in recent years toward the realization of meter-class membrane mirrors. Focal ratios between 1 and 10 have been used with diameters as large as 1.0 m. While none of the membranes has had the quality afforded by traditional ultra-low-expansion (ULE) glass as noted in Table 6, wavefront-correction technology has enabled imaging performance tests. Significant shape quality and correction have therefore been demonstrated.
| Material | Process | Materials to date | Elastic modulus, GPa | Strength, MPa | Relative stiffness, MPa-m 3/kg | CTE, 10 ?6/ C | Measured figure, nm @ shape | Measured roughness, nm | Comments |
|---|---|---|---|---|---|---|---|---|---|
| Space-durable plastic (polymide or other) | a) Flow-cast against high-quality mold55 | CP-DE (polyimide) | 2.17 | 100 | 1.5 | 50 | ~500 @ 1.0 m flat | 1 | Scalable fabrication process; current materials have very high CTE |
| b) Commercial fabrication + non-contact forming | Various kapton grades | 2.5 to 5.3 | 110 to 340 (ultimate) | 2.0 to 3.3 | 16 to 40 | >1000 | 3 to 5 | Used in spacecraft thermal protection; exploits commercial product; not... |
