PSI - Issue 40

N.A. Makhutov et al. / Procedia Structural Integrity 40 (2022) 264–274 Nikolay A.Makhutov at al. / Structural Integrity Procedia 00 (2022) 000 – 000

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where n σ and n e are the stress and strain safety factors, respectively (1 ≤ n σ ≤ n e ). The values fracture stresses σ c and strains e c are in a complex functional dependence on the operational factors:     c c , , , , Ф е F N t    , (3) where Ф are flows of liquids, (oxygen, hydrogen) and gas combustion products. The scientifically rigorous implementation of analytical expressions (1) – (3) implies the development of: - knowledge bases about fundamental laws of propagation of hazardous processes in liquid-propellant rocket engines; - computerized data banks on the systematized parameters of the design dependencies, based on the results of special experiments in laboratories, bench, and field conditions. The creation of the rocket and space industry in the 50s-70s of the twentieth century in the USSR and the USA showed that the operational reliability P of carrier rockets could not be provided only by normative calculations. The increase in reliability was also caused by the increase in the number of launches N l , during which various damages and failures were detected and gradually eliminated, and also various scenarios of failures, accidents, and catastrophes were analyzed.

Fig. 3. The relationship between the probability of safe operation and the number of launches of carrier rockets: 1- Saturn; 2- Shuttle; 3- Blocks; 4- Centaurus; 5- Titanium -3; 6 - Arian; 7 - Delta; 8- Zenith; 9- Atlas; 10 – Proton. As the methods of designing and testing carrier rockets of the first, second and third generations improved, an increase in reliability was achieved at lower N l . (Fig. 3). 3. Experimental studies of the states of stresses The development of rocket and space technology and computer technologies made it possible to comprehensively apply not only analytical solutions of strength and service life problems according to expressions (1) - (3), but also to move to a scientifically valid approach to new verification calculations using mathematical and physical modeling (Makhutov, 2008; Makhutov, 2011; Makhutov, 2013; Makhutov, 2017; Makhutov, 2018) for the most critical components of a liquid-propellant engine - first of all, rotors and blades of turbopump units (Fig. 4).