Development of a Fiber-Optic Gas Bearing-Balance

A one degree of freedom high-frequency aerodynamic bearing-balance will be developed for force, moment, and orientation measurements under non-steady-state flight conditions. A cylindrical bearing-balance three inches in diameter using displacement sensing will be considered as the best candidate for the design. To satisfy the requirement for achieving a natural frequency of 800Hz, the balance must be designed with very stiff gas bearings. The displacement of the sensing elements due to the loads imposed on them will be sensed with a fiber-optic sensing technique. Because the bearings are stiff, the displacements are small and require amplification. The small displacements of the fiber-optic bearing-balance will be sensed and amplified with a modified and upgraded commercial fiber-optic sensor, which is currently being used in a fiber-optic pressure transducer developed at QUEST. Orientation sensing will also use the fiber-optic displacement measuring technique. This will be accomplished by sensing a reflector ring located off center to the bearing axis. During Phase I, we will develop and test a one degree of freedom laboratory bearing-balance. A three degree of freedom prototype bearing-balance will then be designed and tested in Phase II.