## 6 Conclusions  
MIMPS-G500 mN is a green monopropellant propulsion system that was designed for small-size spacecraft in CubeSat architecture. The propulsion system employs a novel autogenously pressurized micro electric pump feed system which is believed, from the author's point of view, to have a great impact on the propulsion system miniaturization and maximizing performance. Such propulsion systems may offer flexibility and adaptability toward the space mission requirements. One of the major capabilities that this system will provide, when compared to other market available monopropellant systems, is the non-degrading thrust performance for almost the whole mission lifetime which is accredited to the unconventional micro electric pump feed cycle that is employed in the proposed novel feed and pressurization system. Another compelling aspect that is solely associated with MIMPS-G design over any available green monopropellant propulsion system is allowing thrust expandability and clustering of several propulsion modules that will work synchronously to fulfill different maneuver requirements for larger size CubeSats. Despite the obvious complexity, such complex systems can be one step closer \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Thruster (HPGP)** & **0.1 N** & **0.5 N** & **1 N** \\ \hline Thrust Range & 30–100 mN & 0.12–0.5 N & 0.25–1 N \\ Inlet Pressure Range (MPa) & 0.23–0.45 & 0.2–0.9 & 0.45–2.2 \\ Nozzle \(A_{e}/A_{t}\) & 100:1 & 100:1 & 100:1 \\ Steady state vacuum \(I_{sp}\) (s) & 196–209 & 178–219 & 204–231 \\ MIB \({}^{\star}\) (mNs) & \(\leq\)5 & \(\leq\)35 & \(\leq\)70 \\ OAL \({}^{\star\star}\) (mm) & 55 ex. FCV & 155 & 178 \\ Mass (g) & 40 ex. FCV & 180 & 380 \\ Pull-in Voltage (VDC) & 10 \(\pm\) 2.5 & 28 \(\pm\) 4 & 28 \(\pm\) 4 \\ Holding Voltage (VDC) & 3.3 & 10 \(\pm\) 1 & 10 \(\pm\) 1 \\ Reactor & 9 & 28 & 28 \\ Pre-heating Volt (nominal) (VDC) & & & \\ Reactor & 6.3–8 & 8–10 & 8–10 \\ Pre-heating Power (regulated) (W) & & & \\ \hline \hline \end{tabular} \({}^{\star}\) Minimum Impulse Bit; \({}^{\star\star}\) Over All Length.  
\end{table} 
Table 13: HPGP thrusters: performance and specifications [59]. toward their realization due to the existence of modern technologies, such as rapid additive manufacturing, advanced materials for space-use (i.e., carbon fiber and high heat resistance superalloys), and most importantly the technological advancements that lead to the availability of affordable suitable microvalves and micro electric pumps. With the existence of advanced onboard computers, real-time onboard control of such multivariable system shall demonstrate technical and operational feasibility. Pump feed and autogenous pressurization are considered unconventional and an undeveloped concept for small-sized spacecraft liquid propulsion, due to their high complexity, especially with green energetic ionic liquid monopropellants. However, this novel approach for propellant feed and tank pressurization can be a drastic change towards high-performance miniaturized spacecraft and small satellites. The MIMPS-G class of propulsion systems is pending the realization phase. The first model, namely MIMPS-G500 mN, is currently in a TRL 2-3; prototyping and testing phases are planned for fall 2021. A short review for state-of-the-art Energetic Ionic Liquid EIL green monopropellants was presented, and a detailed trade-off study was performed to propose the three candidate green monopropellants for MIMPS-G (i.e., ASCENT, LMP-103S, HNP225). The article extensively discussed the system analysis and design methodology as well as the concept of operations of the proposed propulsion system. The preliminary design study was elaborated, and relevant process diagrams and flowcharts were shown to provide more clarification for the reader. Results were quantitatively tabulated and qualitatively assessed, and 3D CAD models and renders were presented within the article body and in the appendix to provide visualization for the reader.