Advanced Inertial Reference Sphere
The Advanced Inertial Reference Sphere is a highly accurate inertial navigation system designed for use in the LGM-118 Peacekeeper ICBM, which was intended for precision nuclear strikes against Soviet missile silos.
Details
AIRS is a fluid-suspended gyrostabilized platform system, as opposed to one using a gimballed gyrostabilized platform. It consists of a beryllium sphere floating in fluid. Jet nozzles are used to stabilize the inertial platform as commanded from the sensors to increase accuracy. This design not only eliminates the problem of gimbal lock, but also makes it extremely accurate, to the point that any further improvement would give a negligible benefit to the missile's CEP.The sensors used in AIRS are floated gas bearing gyroscopes and SFIR accelerometers, which are derivatives of PIGA accelerometers. Although this type of accelerometer is most accurate, it contains many precise parts, making it very expensive to build. PIGA/SFIR accelerometers are also very susceptible to failure due to the complex design.