The effect of thrust cut-off of the third stage of the launch vehicle on the loading and strength of the transport cargo vehicle structure

This paper presents a study of the structural dynamic response of the Progress transport cargo vehicle (TCV) to a trust cut-off of the final stage of the Soyuz launch vehicle. The impulse effect on the structure consisting of TCV and launch vehicle third stage was studied in the following two cases: the first case with a typical thrust cut-off, and the second case with a reduced gradient of the thrust decay. The studies were performed based on a multilevel dynamical modeling of the structures. The implemented technology made it possible to obtain the following results, i.e. to determine the configuration of the transformed impact reduced to any cross section of the vehicle; give an exhaustive estimation of the dynamic structural response to an impulse action; categorize the structures with the most intensive response to the impulse action; localize the area of the TCV structure with the highest level of the strain-stress state. The studies made it possible to make the following main conclusions: the thrust cut-off of the final stage does not generate energy-intensive dynamic effects; the reduction of the thrust decay gradient reduces the structural loading level of by a factor of 1,5; a maximum stress level appears in a narrow area on one of the beams of the instrument compartment frame with a number of cycles less than 10; for the typical engine thrust cut-off the safety margin for peak stresses is more than two, and for a modified thrust cut-off it is more than three. The results presented in the paper show that the LV third engine thrust cut-off is not a design case. It does not create a stress condition close to a critical state and does not affect the strength of TCV