Testing electrostatically suspended gyroscopes using trapped magnetic flux and superconducting sensors

Abstract

This paper presents the results of dynamical testing of an electrostatically levitated, spherical gyroscope that has a superconducting coating. These results are used to verify and to assess the characteristics and the performance of these gyroscopes in preparation for the Stanford Relativity Experiment (also known as Gravity Probe B) space mission intended for 1996. During this mission the angular drift of the spin axis of a spinning gyroscope will be measured during a period of one full year or more in orbit. This measured drift rate will be compared with the theoretical drift rate as predicted by the general theory of relativity. Research presented here shows that it is possible to measure the time history of the spin vector of a spherical gyroscope with respect to two mutually perpendicular pickup loops in a Helmholtz configuration using the dipole component of the magnetic trapped flux inside the gyroscope. With the use of the time history of the gyroscope spin axis, it is possible to estimate the gyroscope characteristics, in particular its mass unbalance. The measurements recorded during this research are unique in a sense that it is the first time a superconducting sensor in conjunction with trapped magnetic flux was used to determine the orientation of the spin vector of a nearly perfect spherical gyroscope.