A dynamical model describing the multi-stage process of rocket propellant loading has been developed. It accounts for both the nominal and faulty regimes of cryogenic fuel loading when liquid hydrogen is moved from a storage tank to an external tank via a transfer line. By employing basic conservation laws, the reduced, lumped-parameter model takes into consideration the major multi-phase mass and energy exchange processes involved, such as highly non-equilibrium condensation-evaporation of hydrogen, pressurization of the tanks, and liquid hydrogen and hydrogen vapor flows in the presence of pressurizing helium gas. A self-consistent theory of dynamical condensation-evaporation has been developed that incorporates heat flow by both conduction and convection through the liquid-vapor interface inside the tanks. A simulation has been developed in Matlab for a generic refueling system that involves the solution of a system of ordinary integro-differential equations. The results of these simulations are in good agreement with the Space Shuttle refueling data.