Definition: 
~ gyroscopes were initially a French specialty (first gyroscope invented by Léon Foucault in  1850s) 
~ they can be classed in order of their precision, expressed in terms of drift measured in °/h (degrees per hour) 
~ drift is  degree of error in  fixed direction  gyroscope is supposed to provide with regard to  stars
~ example drifts 100 °/h "flight control" or "short-range tactical weapons" class to  better than 0.0001°/h : "star in a bottle" class 
~ different technologies are implemented for  various precision classes and operating constraints of  vehicle 
~ (can  gyroscope be separated from  vehicle through gimbal suspension or 
~ can it/must it be part of  vehicle structure – strap-down mounting ) 
~ these include:
~  * Floating gyroscopes: the beginnings of the "great inertia" of the 1950s
~  * Dynamically tuned wheel gyroscopes – platform or strap-down
~  * Vibrating gyroscopes (tuning-fork/quapason; hemispherical resonator gyroscope) – strap-down 
~     hemispherical resonator gyroscope, in particular, is set to offer significant cost reductions for equal performance, 
~    including true "inertial" capacity
~  * Ring-laser gyros, the most popular "strap-down" gyroscope of the decade
~  * Fiber optic gyros in  "fly-by-wire" or "short-range tactical weapons" class
~  * Electric suspension (electrostatic) gyroscopes: "star in a bottle" class
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