Rybalka A. Dynamics and strength of nanosatellite PolyItan-2-SAU under stage of flying

The thesis for a candidate of technical science degree in the specialty 05.02.09 – dynamics and strength of machines.– National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Ministry of Education and Science of Ukraine, Kyiv, 2018. The dissertation is devoted to the solution of the actual scientific and practical problem - development of the PolyItan-2-SAU nanosatellite construction (NS) with the help of a complex simulation-experimental methodology of studying the dynamics and strength of the structural elements on the stage of flying. The scientific and practical significance of the obtained results consists in improved methods of calculation and experimental estimation of the dynamics and strength of NS for the creation of a rational design of the NS, the creation of a method for assessing the strength of the structural elements of the NS on the basis of the recommendations of NASA and the European Space Agency and expanding the representation of the stress state of the NS structural elements during the stage of flying. In the work was created the general methodology of simulation-experimental estimation of the strength of the NS which based on the method of through-design, which includes the definition of dynamic characteristics, deterministic and probabilistic characteristics of the stress-strain state (SSS) in the design elements of the NS based on a single simulation model (SM). For the study of dynamic characteristics and SSS, the single SM of the NS and its discrete analog, which create by using the standard finite elements of various type (solid, plate and beam), have been developed. On the basis of it, for the first time the dynamic characteristics and numerical regularities of the distribution of the SST characteristics in the constructive elements of the NS under the influence of quasi-static overloads, harmonic and random vibrations are obtained. The analysis of the results of the design study on the basis of a single SM showed that the strength of the design of the NS during the stage of flying to the orbit is confirmed. The results of the design study of dynamic characteristics and SSS were used in conducting an experimental study of dynamic characteristics and strength of NS, and verification of its SM. Based on the requirements of QB50 System Requirements and Recommendations and the results of the preliminary simulation research, a shortened program of the experimental study of dynamics and strength of the NS has been developed. Analyzing of the experimental study results on the determination of amplitude-frequency characteristics, was established their natural frequency of oscillations in the frequency range of the acting NS’s loads. Determined the most loaded elements of the design of the NS under the action of harmonic and random vibrations. The conducted experimental study confirmed that the strength of the structure of the NS at the stage of flying to the near-Earth orbit is aproved. The results of experimental studies showed the difference between the received dynamic characteristics of the design elements of the NS with the estimated before data. Therefore, according to the recommendations of the European Space Agency, the SM’s verification was carried out on frequency characteristics. The verification of the SM consisted of adjusting the stiffness of the contact elements in the SM, specifying the coefficients of damping the structural elements of the NS. Loads characteristics and kinematic constraints correspond to previously accepted. As a result of simulation on the basis of the verified SM of the NS, dynamic characteristics and SSS in the design elements of the NS were determined at the action of loads corresponding to the stage of the flying into orbit. According to the results of the verification it was established that the own natural frequency of the SM now corresponds to the experimental data. In the case of the action of harmonic and random vibrations, the place of maximum magnitudes of equivalent Mises stresses has not changed. According to the simulation-experimental study of dynamics and strength of the NS which based on a using the single SM was created a rational design of the NS PolyItan-2-SAU. NS was launched on April 18, 2017 by carrier Atlas V. The NS has been successfully operating in Earth's orbit for 20 months at a specified resource of 6 months