http://disc.yourwebapps.com/discussion.cgi?disc=159729;article=102431mip
Galactic Life Imager
Fri Jul 2, 2010 11:45pm
67.193.52.10
Mission - To image 1-meter-sized features including life, on planets up to 550 lightyears away. This volume of space contains an estimated 89,000 G-type stars like ours, and 1.8 million stars of all types. It would take many decades of operation to survey all of them.
Mirror Segments - A parabolic bowl with a 1000-meter focal length is very shallow having a surface area only 2 percent larger than a flat circular disk of the same diameter. If we construct the parabola out of equilateral triangular segments with 1.0392-meter edge length, which are then assembled into hexagonal mirrors 1.8-meters across the flats, then it would require 2,145,432 triangular segments. With a thickness of 7.5-centimeters the total mass of fused silica glass would be 167,805-tonnes. A 300-nanometer thick reflective aluminum coating would have a mass of 813-kg.
Assembly - About 3000 of the small mirror segments can be fitted into a larger triangular sheet with an edge length of about 57 meters. These large sheets can be stacked 54 meters high for transport. The 715 layers that comprise this stack can be unstacked again when the spacecraft reaches the 208-AU destination point, and re-assembled into an expansive array of mirrors, connected edge-to-edge, forming a parabolic reflector 1119-meters in diameter.
