New techniques for fusion bonding and replication for large glass reflectors

Lengths of glass tubing are used as the starting point of a new method to make light-weight glass honeycomb. The tubes are packed together and filled with free flowing refrac-tory sand. On heating to the softening point of the glass the sand pressure forces the tubes into contact. Close packed round tubes yield hexagonal glass honeycomb. Face plates can be incorporated in the same fusion step. The method has been demonstrated for borosilicate glass, but should be applicable also to fused silica. A method for accurate repli-cation of borosilicate glass off a fused silica master has also been demonstrated. It is shown that gold is an effective parting layer, and small scale replicas have been measured to have about 1μ FMS accuracy. It is suggested that honeycomb panels made by the sand fusion method and replicated off fused silica may make ideal panels for precision deployable reflectors like LDR.