TABLE OF CONTENTS One of the most demanding applications of inertial systems for achieving very high accuracy is the navigation of naval ships and submarines, which may be required to operate covertly for long periods of time in any part of the ocean, including the polar regions. Early work in the United Kingdom at the Admiralty Compass Observatory (ACO), Slough (formerly part of the Defence Evaluation and Research Agency), led to the development of very stable platform systems: these devices provided an autonomous navigation capability in the 1 nautical mile per day class, incorporating gyroscopes with residual biases of less than 0.001 /h. The single-axis rate-integrating gyros used for these applications were highly sophisticated instruments with gas bearings, which needed to operate in a closely controlled temperature environment to achieve the level of performance required for highly accurate navigation.
A British programme to develop a ship's inertial navigation system at the ACO dates from the mid-1950s. The initial system design incorporated rate-integrating gyroscopes developed by the Charles Stark Draper Laboratory in the United States, where the rotor was supported by high-precision ball bearings. This project led to laboratory tests and initial sea trials in 1961. The system became fully operational in 1968. During this time, ACO played a major part in the development of a new rate-integrating gyroscope for SINS in which the rotor was supported by a gas bearing, which resulted in an order of magnitude improvement in performance. SINS Mk. 1 was a completely analogue design,...
