Abstract
RECENT ADVANCES in atmospheric and space flight have increased the need for reliable and accurate instrumentation for sensing the angular motions of aircraft, missiles, and space ships. Such measurements are especially needed for guidance and control purposes. At the present time, the preferred devices for measuring angular motion are based on the rotating-wheel gyroscope. By the expenditure of much research and development effort these gyroscopic devices have been brought to a state of perfection which makes inertial navigation technically feasible but very expensive. The present reliance on the rotating wheel does not mean that other devices have not been considered. Over the years a number of alternatives to the rotating wheel have been devised and some of these have been developed to the point where practical limitations on performance were found. In general, however, the total research and development effort that has been devoted to these alternatives has been rather small compared with the effort that has been expended in the refinement of the rotating-wheel gyroscope.