To execute program motions, the space stages of liquid-propellant launch vehicles are equipped with restartable propulsion engines. On the shutdown of the propulsion engine of a space stage, the liquid propellant in the tank in microgravity conditions moves by inertia upwards as far as possible away from the intake. This results in the potential possibility of the pressurizing gas penetrating into the engine inlet in quantities that make an engine restart impossible. Because of this, motion parameter determination for a liquid moving in propellant tanks in microgravity conditions is a topical problem to be solved in the designing of liquid-propellant rocket engines. This paper presents a technique for the calculation of the parameters of motion of the gas-liquid interface in the propellant tanks of modern liquid-propellant launch vehicle space stages in microgravity conditions (between a start and a shutdown of their propulsion engines) taking into account the design features of in-tank propellant management devices. The technique is based on the use of the finite-element method, the volume-of-fluid method, and modern finite-element CAE systems. It allows one to determine the parameters of motion and the shape of the free liquid surface in the tank, the parameters of free gas inclusions formed in the liquid, and the efficiency of the in-tank propellant management devices in the passive portion of the launch vehicle flight for the normal operation of the propulsion system. For the conditions of motion of a prototype propellant tank with a liquid in a drop tower, which simulates microgravity, the motion of a liquid in a cylindrical tank was simulated numerically accounting for the deformation of its free surface. The computed motion parameters of the liquid and the gas-liquid interface agree with the experimental data. The technique developed will allow one to reduce the extent of testing of newly developed and upgraded launch vehicle space stages.

The methodical approach to the determination of the initial kinematics and geometrical characteristics of the fuel components droplet cloud derived from the liquid-propellant carrier rocket (CR) explosion at the atmospheric trajectory leg is developed. The phenomenological analogy of the transient-load damage processes in the fractured solids and a mass of a gas-saturated cavitation liquid is taken as a basis of the approach. The droplet cloud characteristics obtained by this means can be used as the reference data for calculating the subsequent transformation of the cloud when it moves in the gravitation field taking into account heat-mass exchange with an atmosphere, as well as for estimating the ecological risks in the ground area of the CR fallout.

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The aim of this work is to develop a methodological approach to simulating the evolution of a droplet cloud (DC) formed as a result of an explosion of a launch vehicle with self-inflammable propellant components in the initial portion of the flight trajectory and thrown into the atmosphere with initial motion parameters that correspond to the launch vehicle position at the time of the explosion. The proposed approach, which is based on a phenomenological analogy with the motion of a fuel spray injected in the combustion chamber of a diesel, takes into account the fragmentation and tracing of droplets and the effect of their collisions and possible coalescence on the structure and parameters of the propellant component DC, which undergoes a transformation as it moves. The proposed model of the DC evolution, which is due to droplet interaction in the DC and its structuring in the process of motion, reflects the most important, in terms of the environmental consequences of the explosion, processes in the DC and allows one to estimate its basic kinematic and geometric characteristics required for solving the ballistic problem of the motion of the suspended DC droplets in the atmosphere and their precipitation onto the ground surface.