The Spacecoach : A scalable and upgradable platform for long duration crewed flights based on electric propulsion using water rich propellant Author: Brian McConnell, BSci, Founder, Open SETI Data Archive Abstract Background: The spacecoach, first described by authors Brian McConnell and Alex Tolley in JBIS in 2010, uses water and waste gases as propellant in a solar electric propulsion system. This radically improves the mass budget for long duration crewed missions by transforming consumables that would otherwise be dead weight into propellant mass. A good overview with additional references can be found here. Recent modeling shows that the same approach can be used with a fusion powerplant to drive an electric propulsion system to achieve 0.1c transit speeds while providing a large mass budget for water and other consumables that would be needed for a long duration flight. Abstract Objectives: While the spacecoach was originally conceived as a platform for exploration within the solar system, it can be upgraded as new power and propulsion technologies become available. First generation ships, starting with scaled down robotic systems, can be flown with present day solar electric propulsion technology, while providing an evolutionary pathway to inter-planetary and eventually interstellar flight as lightweight nuclear electric power plants become available. Abstract Methods: The authors developed a detailed parametric model for platforms designed for missions within the solar system, and demonstrated that order of magnitude improvements in payload mass budgets are enabled by using consumables as propellant. In this workshop, we will model the performance of a spacecoach that is outfitted with a nuclear electric propulsion system. Abstract Results: We modeled a spacecoach with a mass ratio of 100:1, where most (> 90%) of the propellant mass is water or water equivalent material, and the remainder fusion reactant. A fusion powerplant drives an electric propulsion system that accelerates this material to 0.01-0.1c. We show that the system can reach transit speeds of 0.1c or greater while providing a large mass budget for water and consumables. Abstract Conclusions: The spacecoach architecture, by allowing for generous consumable budgets, is a promising approach for long duration crewed flight, and can be validated in near earth missions and upgraded as new power and propulsion technologies become available.