The James Webb Space Telescope, targeted for launch in 2013, is already taking an incredible journey right here on Earth.To get ready for space, the 18 mirror segments that will ultimately form the Webb telescope’s huge primary mirror are trucked from pit stop to pit stop in tandem cross-country for careful processing and polishing.The story begins in a Utah beryllium mine. Beryllium is one of the lightest of all metals, and the “stuff” of the telescope’s mirrors.
Technicians in Ohio sift and purify the gritty beryllium powder from Utah into an extremely uniform optical grade especially for the Webb mirror. Then they pour the powder in a big, flat can, apply heat and pressure, and pump out the residual gas to create a large slab called a mirror billet. They bathe the billet in acid to burn off any stainless steel stuck to the billet when the can is removed. Next they split the billet in half Oreo-cookie-style to form two mirror blanks (no cream!). These mirror blanks are the largest ever produced in beryllium.
Workers in Alabama machine the back of each blank into a honeycomb structure to make the blanks lighter without reducing stiffness. The machined ribs are less than 1 millimeter thick — almost paper cut thin!