Modal analysis of the dynamic mockup of “AIST–2D” small spacecraft

The article describes a methodology of experimental determination of dynamic behavior of rocket and space equipment, using the example of AIST-2D small spacecraft. Experimentally obtained modal characteristics (natural modes and frequencies) are compared with modal characteristics calculated for the said spacecraft using a finite element model (FEM). The natural modes and frequencies of the spacecraft were experimentally obtained using scanning laser vibrometry; the modal analysis was performed using finite elements and the MSC. Patran / Nastran FEM package. The objectives and tasks are formulated; the main stages of modal analysis are described. It is necessary to update the finite-element models of spacecraft parts to obtain precise loads applied to such parts. During the tests target resonance frequencies of the test object were obtained for the 5-130 Hz range, as this range contains the first modes of the structure. Since the spacecraft is characterized by many uncertainties in stiffness parameters, the error of determining own frequencies was as high as 45.75% at the first stage of the research, which confirms the necessity of carrying out modal analysis. Dynamic characteristics of spacecraft structural elements obtained during the research will allow creating more precise and reliable spacecraft dynamic models at the design stage; this, in its turn, will improve precision of load calculations and reliability of the spacecraft in general.