Advanced Inertial Reference Sphere
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The Advanced Inertial Reference Sphere, or AIRS, is a highly accurate inertial guidance system designed for use in the LGM-118A Peacekeeper ICBM.
[edit] Details
AIRS is a fluid stabilized system, as opposed to one using gimbals. It consists of a beryllium sphere floating in fluid. Jet nozzles are used to stabilize the inertial platform as commanded from the sensors. This design not only eliminates the problem of gimbal lock, but also makes it extremely accurate, accurate enough so 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 which makes them very expensive to build (approximately $300 000 per unit). PIGA/SFIR accelerometers are also very susceptible to failure because of complicated design.
[edit] Usage
The AIRS was originally developed for the LGM-118A Peacekeeper. The first AIRS's were manufactured by Northrop. They are used in Minuteman III ICBM after Peacekeeper missiles were retired in 2005.
