Scattering from Infrared Missile Domes

Abstract

An automated system for scanning missile domes under computer control at an arbitrary number of points and determining both forward scattering and transmittance from 0 degrees to over 60 degrees from the dome axis is now in operation. Measurements at 3.39 pm have been made on both new and used domes, artificially eroded domes, and also on pieces of spinel, which is a possible replacement for the magnesium fluoride now used as an infrared dome material. A total of 18 new, 1 used, and 2 artificially eroded domes have been measured. Data indicate that (1) the scattering and transmission is nearly uniform as a function of angle away from the dome axis for the used dome as well as for new domes, (2) the scatter from the used dome was higher than that from 16 of the 18 new domes, but less than that for two of the new domes (26% more scatter than the average of all the new domes), and (3) a sample of press-forged, single-crystal spinel scattered five times less than the average of the new domes, while a fusion-cast polycrystalline spinel sample scattered 2.5 times more than the average.