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. General requirements relating to Mechanical Engineering are defined in EN 14607 Part 1. This document applies only to liquid, including cold gas, and electrical propulsion systems used in spacecraft and to related mechanical parts. Solid propulsion for spacecraft, and solid and liquid propulsion for launchers are not covered by this document. Other forms of propulsion currently under development (e.g. nuclear, nuclear-electric, solar-thermal and hybrid propulsion) are not presently covered by this document. When viewed in a specific project context, the requirements defined in this document should be tailored to match the genuine requirements of a particular profile and circumstances of a project.