Advanced Inertial Reference Sphere (1997)
The AIRS is the most accurate inertial navigation system ever developed, and perhaps marks the end of a long process of continuous refinement of INS technology. Very little of the precision of this guidance system is even exploited during a ballistic missile flight, it is mostly used simply to maintain guidance system alignment on the ground during missile alert without needing an external reference through precision gyrocompassing. The AIRS is probably as good as any INS for ICBM guidance needs to get. The proposed BIOS, a glide-bomb adaptation of the B-61, has proposed using GPS for guidance instead of an INS. Given the competition from advanced external reference based approaches, INS technology has probably reached the end of the line as far as accuracy goes. In May 1975 the AIRS was transferred from the Draper Laboratory to Northrop for advanced development. Accordingly, between 1998 and 2002, 652 new AIRS guidance units will be purchased and fitted to the existing Minuteman III.Features. The AIRS consists of a beryllium sphere that floats in a fluorocarbon fluid within an outer shell and can thus rotate in any direction.