COMPARISON OF ANALYTICAL MODELING OF OEDIPUS TETHERS WITH DATA FROM TETHER LABORATORY

The OEDIPUS missions employ suborbital rocket flights to study the spa ce plasma of the ionosphere. An OEDIPUS payload comprises two spinning subpayloads that are connected by a tether that is up to 1000 m in le ngth. Experiments that were undertaken with a Tether Laboratory Demons tration facility (TE-LAB) to confirm mathematical modeling of OEDIPUS are reported. A linear mathematical model of the dynamics of the groun dbased configuration is outlined. The modeling entails the same method s that are used for the in-space OEDIPUS configuration and, in additio n, includes effects important to the l-g laboratory environment. An ei genvalue analysis of the model is presented that is based on damped gy roscopic natural modes. Stability criteria are obtained from analysis of positive definiteness of the stiffness matrix. Data from test cases obtained with the TE-LAB facility are presented. The data include exp erimental modal parameters obtained using a charge-coupled device came ra and fast Fourier transform-based processing. The eigenvalues from t he analytical model compare well over the parameter range investigated . The analytical stability criteria also match with TE-LAB results for end-body dynamics. However, modeling of nonlinearities would be requi red to explain some of the dynamics phenomena of the tether that are i n evidence in the TE-LAB data.