Propulsion units on the International Space Station

The paper provides a brief description of propulsion units (PUs) installed on modules of the Russian Segment of the International Space Station (ISS). It discusses the purpose of the PUs, their configuration and performance data. Fluid circuits of the PUs are similar, and consist, on the whole, of the pressurization and propellant supply system, as well as liquid-propellant rocket engines. Propellant systems of PUs of the ISS modules are interconnected, enabling engines of one module to run on propellant from another module, while pass-through propellant lines of the modules make it possible to refuel PU tanks from any port to which a cargo transportation spacecraft Progress is docked. The paper examines specific issues regarding the PU bellows tanks that are used, some aspects related to propellant and environment on the ISS, experimental units that are PU analogues.