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The Advanced Inertial Reference Sphere (AIRS) is a highly accurate
Detailed description
Military electronics of the United States Missile guidance Navigational equipment {{Missile-stub
The Advanced Inertial Reference Sphere (AIRS) is a highly accurate inertial navigation system
An inertial navigation system (INS; also inertial guidance system, inertial instrument) is a navigation device that uses motion sensors (accelerometers), rotation sensors (gyroscopes) and a computer to continuously calculate by dead reckoning th ...
designed for use in the LGM-118 Peacekeeper
The LGM-118 Peacekeeper, originally known as the MX for "Missile, Experimental", was a Multiple independently targetable reentry vehicle, MIRV-capable intercontinental ballistic missile (ICBM) produced and deployed by the United States from 1986 ...
ICBM
An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...
, 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 aberyllium
Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...
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
Gimbal lock is the loss of one degree of freedom (mechanics), degree of freedom in a multi-dimensional mechanism at certain alignments of the axes. In a three-dimensional three-gimbal mechanism, gimbal lock occurs when the axes of two of the gi ...
, but also makes it extremely accurate (drift less than 1.5×10−5 °/h), 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 gyroscope
A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining Orientation (geometry), orientation and angular velocity. It is a spinning wheel or disc in ...
s and SFIR accelerometers, which are derivatives of PIGA accelerometer
A PIGA (''Pendulous Integrating Gyroscopic Accelerometer'') is a type of accelerometer that can measure acceleration and simultaneously integrates this acceleration against time to produce a speed measure as well. The PIGA's main use is in Inertia ...
s. Although this type of accelerometer
An accelerometer is a device that measures the proper acceleration of an object. Proper acceleration is the acceleration (the rate of change (mathematics), rate of change of velocity) of the object relative to an observer who is in free fall (tha ...
is most accurate, it contains many precise parts, making it very expensive to build (approximately $6,000,000 per AIRS unit in 1987, not including development costs). PIGA/SFIR accelerometers are also very susceptible to failure due to the complex design.
Usage
The AIRS was originally developed for the LGM-118A Peacekeeper. The first AIRS units were manufactured by Northrop.References
*External links
Detailed description
Military electronics of the United States Missile guidance Navigational equipment {{Missile-stub