###### Abstract  
Green propellants are currently considered as enabling technology that is revolutionizing the development of high-performance space propulsion, especially for small-sized spacecraft. Modern space missions, either in LEO or interplanetary, require relatively high-thrust and impulsive capabilities to provide better control on the spacecraft, and to overcome the growing challenges, particularly related to overcrowded LEOs, and to modern space application orbital maneuver requirements. Green monopropellants are gaining momentum in the design and development of small and modular liquid propulsion systems, especially for CubeSats, due to their favorable thermophysical properties and relatively high performance when compared to gaseous propellants, and perhaps simpler management when compared to hippellants. Accordingly, a novel high-thrust modular impulsive green monopropellant propulsion system with a micro electric pump feed cycle is proposed. MIMPS-G500 mN is designed to be capable of delivering 0.5 N thrust and offers theoretical total impulse \(I_{\text{tot}}\) from 850 to 1350 N s per 1U and \(>\)3000 N s per 2U depending on the burnt monopellant, which makes it a candidate for various LEO satellites as well as future Moon missions. Green monopropellant ASCENT (formerly AF-M315E), as well as HAN and ADN-based alternatives (i.e., HNP225 and LMP-103S) were proposed in the preliminary design and system analysis. The article will present state-of-the-art green monopropellants in the (EIL) Energetic Ionic Liquid class and a trade-off study for proposed propellants. System analysis and design of MIMPS-G500 mN will be discussed in detail, and the article will conclude with a market survey on small satellites green monopropellant propulsion systems and commercial off-the-shelf thrusters. green monopropellant; chemical rocket propulsion; CubeSats; small satellites; micro electric pump feed cycle +
Footnote †: journal: 19 June 2021  
subsystems and components, which usually reduce development costs and time. Miniaturization of components is crucial to the space industry in general, since nowadays every gram of payload mass to orbit may have a significant monetary value, adding to that the presence of onboard size restrictions. Design modularity and miniaturization is a major point of focus for various research work in the space propulsion field in general, either for electric propulsion [4; 5] or for chemical propulsion in standalone systems or in multimode systems, as extensively studied by [PERSON] et al. [6]. On another note, green monoprellants are the current trend in liquid propellant propulsion for small satellites, either in scientific or industrial research and development as well as commercial activities, due to their safety, stability, storability, relative design simplicity, as well as high performance, and may soon face global legal regulations for a greener environment-as expected by the authors. These facts were the motive behind the design of (MIMPS-G) the Modular Impulsive Propulsion System to utilize Green monoprellants and is a prospective system for micro and nano spacecraft, particularly CubeSats, requiring a modular propulsion system for high-thrust impulsive orbital maneuvers. From the study of the market and the current state-of-the-art products in the green propulsion industry, it was deemed necessary to design a green monoprellant propulsion system that would help in solving several challenges related to acquiring higher performances and lower costs as well as demonstrating competitive advantages to currently proposed systems, as will be discussed in Sections 4 and 5 of this manuscript. The design and development plans have taken place within a research work carried out at the beginning of the year 2020 between the Department of Aerospace Engineering in the University of Pisa and the Department of Space Engineering of the Aerospace Engineering Faculty in TU Delft.