EN 14607 Part 5.1 of Space engineering - Mechanical defined the requirements for the discipline liquid and electric propulsion for spacecraft This document belongs to the propulsion field of the mechanical discipline, as defined in EN 13292, and defines the regulatory aspects applicable to elements and processes for liquid, including cold gas, and electrical propulsion for spacecraft. It specifies the activities to perform in the engineering of such propulsion systems, their applicability, and defines the requirements for the engineering aspects: functional, configurational, interfaces, physical, environmental, quality factors, operational and verification.