Inertial-Guidance Limitations Imposed by Fluctuation Phenomena in Gyroscopes

Because of recent improvements, inertial guidance is becoming increasingly important to space and missile programs in connection with the navigation of mobile bases and the launching of vehicles. Gyroscopes are an important component of inertial systems. In order to see if much room remains for further improvement, the performance limitation imposed by thermal fluctuations in gyroscopes is examined. This is done because experience in electronics shows that thermal noise is the ultimate performance limitation in sensitive instruments such as radio receivers and galvanometers. It is found that a system limited only by thermal noise in its gyroscopes would have several orders of magnitude more precision than that indicated in published performance data. This must mean that other factors are limiting performance of gyroscopes, and investigation of several of these shows that bearing noise may be an important one. In conclusion, since gyroscopes do not yet come near to attaining the performance limits set by thermal noise, there may be much room left for their further improvement.