This Master's thesis contributes to the Deep Space Platform (DSP) Phase A study, conducted in collaboration with Thales Alenia Space Italy (TASI) for the Technical Offer commissioned by the Italian Space Agency: "Phase A Industrial Activities of the Deep Space Platform Programme for Multi-Mission Activities Beyond Low Earth Orbit". The company's objective is to deliver a low-cost, high-flexibility, multi-mission platform tailored for the New Space Economy and designed to support future missions to the Moon, Mars, and Near-Earth Asteroids (NEAs). The primary focus of this work is the development of the platform's Chemical Propulsion Subsystem (S/S) numerical model, utilising the EcosimPro simulation environment and its leverage of the specialized European Space Propulsion System Simulation (ESPSS) libraries.