Monitoring multi-axial vibrations of flexible rockets using sensor-instrumented reference strain structures

Strain sensors (e.g., fiber optic strain sensors) can be used to measure the deformation of flexible rockets during launches, in order to monitor and control rocket flight attitude. In this paper, strain sensors are instrumented on multi-axial reference strain structures for a convenient monitor of rocket bending vibrations. Reference strain structures are attached longitudinally along the outer surface of thin-walled flexible rockets. As the medium between the sensors and rocket, the structural design of reference strain structures, as well as the sensor spacing along them, is optimized using an integrated multi-objective optimization approach, which ensures that the reference strain structures will accurately track the deformation of the rocket surface. In addition, kinematic equations are developed to allow for an accurate prediction of the bending deflection of the rocket center axis by using the strain data measured on the rocket surface. Finally, the performance of the optimal reference strain structure is evaluated using different numerical simulations of the flexible rocket.