To validate flight loads predictions, a modal test is required to verify the structural dynamic model of a spacecraft used in loads analyses. Traditionally, modal testing of shuttle payloads is performed with the payload in its fixed-base configuration, i.e., constraining all the payload/orbiter interface degrees of freedom. Practically, the fixed boundary conditions are quite difficult to achieve with large and massive payloads, such as the Shuttle Imaging Radar-C. This leads to the consideration of testing payloads in a free-free configuration, or other alternatives. In this paper, it will be shown analytically how free-free modes and residual flexibility data can be adequate to characterize the significant fixed-base modes. As a result, the fixed-base modes can be verified indirectly from the measurements of free-free modes and residual flexibility.
展开▼
