Annotation: In the present-day rocket engineering, the liquid rocket engines with pump feed system have gained wide acceptance. As a rule, the pumps used in liquid rocket engines are screw-axifugal. The screw serves to increase pressure upstream of the axifugal wheel, thus ensuring its cavitation-free operation. The screws used in the screw-axifugal pumps of liquid rocket engines may be of two types: with constant and variable step. The screws with constant step are easier to calculate, profile and manufacture as compared to the screws with variable step. As known from the literature, the use of the screw with variable step increases power characteristics of the screw-axifugal pump. The purpose of investigation is comparative analysis of cavitation and power characteristics of the following high-speed low-consumption screw-axifugal pumps of liquid rocket engines with jointed screws, screws of constant and variable step:  RD868 engine oxidizer and fuel pumps;  RD859 engine fuel pumps;  RD861K engine fuel pumps. Besides, the analysis has been made of the impact of design features and geometrical dimensions of the screws with variable and constant step on power characteristics of the screw-axifugal high-speed lowconsumption pumps of liquid rocket engines. Special attention has been given to the analysis of anticavitation properties of the pumps with screws of variable step and pumps with jointed screws. Based on the results of investigation, it has been ascertained that when using the joint screws and screws with variable step instead of the screws with constant step in the high-speed low-consumption screw-axifugal pumps of liquid rocket engines, the pump delivery head increases from 0.65 to 3.83%, the efficiency increases up to 1.7%. The use of jointed screw and screw of variable step as compared with the screw of constant step does not have any impact on cavitation properties of low-consumption crew-axifugal pumps of liquid rocket engines.

Annotation: When accomplishing the task of spacecraft orbital injection, the necessity arises of main engine multiple ignitions and consequently, long pauses between the ignitions are possible. As the propellant during pauses between ignitions is in the conditions of practically full absence of gravitation and can freely move over entire tank volume taking practically any spatial position, to ensure main engine guaranteed ignition the necessity arises to move the propellant into pre-start position. The propellant is moved to the supply lines by way of creating longitudinal acceleration which is done using inertial continuity ensuring means (thrusters). The time of full liquid displacement from one position into another is the most important parameter having an impact on propellant amount in the tanks and accordingly, on power characteristics of a stage. The theoretical calculations of hydrodynamic processes are connected with considerable mathematical difficulties caused by complexity of solving hydrodynamic problems of determination of liquid flowing with free surface taking into account surface tension of the liquid and many other geometrical, kinematic, and dynamic factors. Therefore, the most reliable data from solving these problems are currently obtained only on model hydrodynamic stands where it is possible to model liquid behavior in tanks in the conditions of variable gravitation. The paper presents the authors-developed procedure of calculating the full time required for propellant components deposition during rocket’s apogee stage flight and the procedure of selecting the modeling parameters (scale, time, and acсeleration) to ensure development testing in the conditions of limited test stand base. The use of the proposed procedure allows (in initial phase of launch vehicle development) determining the full time required to perform deposition with sufficient accuracy and thus optimizing the propellant mass required for operation of inertial continuity ensuring system, which in its turn, will allow increasing the payload mass to be injected.