Scattering From Infrared Missile Domes

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° to over 60° from the dome axis is now in operation. Measurements at 3.39 pm have been made on both unused 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 15 of the 18 new domes, but less than that for 3 of the new domes (26% more scatter than the average of all the new domes), and (3) the sample of pressforged, singlecrystal spinel scattered 5 times less than the average of the new domes, while the fusion -cast polycrystalline spinel sample scattered 2.5 times more than the average.