Filling of Liquid Oxygen and Methane in cryogenic condition and venting of gaseous boil-off for a large ESA launcher stage were developed based on a new quick-disconnect umbilical system. Optimisation of the flow channels and valve details were made using ANSYS-CFX. Heat transfer to the fluids, pressure drop, local flow velocity and thermal stress in the connector bodies were analysed, support to systems engineering, mechanisms and stress analysis, test plan and test set-up were provided.