Advanced Inertial Reference Sphere (AIRS)

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Advanced Inertial Reference Sphere (AIRS)
Advanced Inertial Reference Sphere (AIRS)

Hill Aerospace Museum

PEACEKEEPER ADVANCED INERTIAL REFERENCE SPHERE (AIRS)
The Advanced Inertial Reference Sphere (AIRS) was part of a highly accurate inertial guidance system designed for use in the LGM-118A Peacekeeper missile for precision nuclear strikes against enemy targets.

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The AIRS (Advanced Inertial Reference Sphere) is the most accurate inertial navigation (INS) system ever developed, and perhaps marks the end of a long process of continuous refinement of INS technology. The AIRS was designed for use in the LGM-118A Peacekeeper ICBM.

The most novel aspect of the AIRS is that it has no gimbals. Gimbals are pivots that are provided for each of three spatial axes so that the guidance platform can move freely in all directions (and thus maintain its absolute alignment with the outside world). The AIRS consists of a beryllium sphere that floats in a fluorocarbon fluid within an outer shell and can thus rotate in any direction. The importance of this innovation is that it eliminates the possibility of gimbal lock (where the axes of two gimbals line up and destroy the three-dimensional freedom of motion), and is free from arbitrary limits to range of motion found in some gimbal designs.

The temperature of the fluid is controlled with extreme accuracy by transfer of heat from the fluid through "Power shells" to freon-cooled heat exchangers. The alignment of the sphere is controlled by three hydraulic thrust valves directed by the inertial sensors in the sphere.

Like other INS systems, the sphere houses three accelerometers and three gyroscopes. The accelerometer design is called a SFIR (specific force integrating reciever). This is essentially the same approach as the pendulous integrating gyro accelerometer (of PIGA) used in the Minuteman II. The SFIR/PIGA works by measuring the rate of precession (and thus force applied) to a gyroscope at right angles to its axis of rotation. The gyroscope is a floated gas bearing gyroscope design.

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Taken on: December 13, 2022
Tags: Everybody's photos tagged with INS INS Everybody's photos tagged with beryllium beryllium Everybody's photos tagged with LGM-118 LGM-118 more » Everybody's photos tagged with Peacekeeper Peacekeeper Everybody's photos tagged with peacekeeper missile peacekeeper missile « less
Sets appears in:   • Inertial Guidance System    • Hill Aerospace Museum - Lindquist Stewart Gallery    more » • LGM-118 Peacekeeper Missile    « less
Camera: Canon PowerShot G7 X Mark II, f/3.2, 1/60 sec, 8.8mm, ISO 250 (more info) (hide info)
Camera: Canon PowerShot G7 X Mark II
Aperture: f/3.2
Exposure Time: 0.017 sec (1/60)
Focal Length: 8.8mm
ISO: 250
Exposure Bias: -1/3 EV
Flash: Off, Did not fire
Exposure Program: Aperture-priority AE
Exposure Mode: Manual
Metering Mode: Center-weighted average
White Balance: Auto
Color Space: sRGB
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