NOVELTY - The spacecraft has coupling units for coupling fuel, oxidizer and reaction product tanks (1-3) of an energy storage system (20) i.e. regenerative fuel cell, with pressurization tanks (4, 5) of propellants of a chemical propulsion system (10). The reaction product tank contains product resulting from reaction of an oxidizer and fuel. The coupling units comprise discharge units for emptying the pressurization tanks, and connection units for connecting the fuel and oxidizer tanks respectively to the pressurization tanks when the pressurization tanks do not contain pressurization gas.    USE - Spacecraft i.e. telecommunication satellite (claimed), for observation missions or mission dedicated to a terrestrial communication network.    ADVANTAGE - The connection units connect the fuel and oxidizer tanks of the regenerative fuel cell respectively to the pressurization tanks of the chemical propulsion system when the pressurization tanks do not contain pressurization gas, thus reducing mass of the fuel and oxidizer tanks of the fuel cell to reduce impact mass and masse of the spacecraft, and hence improving electrical performances of the fuel cell for rapidly adopting of the fuel cell in the satellite, and permitting dimensions of the fuel and oxidizer tanks to provide sufficient energies to electronic systems of the satellite during launching.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for coupling tanks of an energy storage system i.e. regenerative fuel cell, with pressurization tanks of propellants of a chemical propulsion system of a spacecraft.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view illustrating coupling between an energy storage system i.e. regenerative fuel cell, and a chemical propulsion system of a satellite without representing other functional systems of the satellite.    Fuel tank (1)    Oxidizer tank (2)    Reaction product tank (3)    Pressurization tanks (4, 5)    Chemical propulsion system (10)    Energy storage system (20)