Modal diagnostics of transient processes during evaluation of results of tests on rocket and space hardware

One of the main tasks of technical diagnostics when evaluating the results of tests on hardware for various applications is to determine (identify) their key parameters and characteristics, comparing obtained estimates against design values and identifying anomalous (dangerous) discrepancies. The importance of such tasks is highlighted by the fact that they are addressed by the modern theory of solving inverse ill-posed problems, the methods of which are used in various branches of engineering, including rocket and space technology. Practical application of these methods often occasions the question of what are the advantages and difficulties inherent in solving inverse problems of this kind on unsteady-state modes? Such processes have an obvious advantage - a richer spectrum of loads exciting natural oscillations of the object under study, and, accordingly, greater amount of information as compared with steady-state (forced) processes. The paper demonstrates how, all methodological difficulties notwithstanding, the use of the state-of-the-art methods of studying the dynamics of complex engineering systems allows to solve problems of this kind as well. These methods are based on modal diagnostics and singular decomposition of matrices of transient processes. The paper provides examples of such diagnostics of transient processes for two products of rocket and space technology - an upper stage and a descent vehicle.