### Unconventional Feed and Pressurization Systems  
Autogenous pressurization is an old concept that has been utilized in space systems since 1968 [30] and it is mainly used in medium to large size pump-fed engines. The system uses vaporized propellants to pressurize tanks by passing streams of cool propellant through a heat source that can be the thrust chamber cooling jackets or heat exchangers. This term was sometimes paired with turbopump feed cycles, especially in launcher engines. Nowadays, electric pump feed cycles are a major focal point in various current research work, especially after being successfully utilized in the Rutherford engines of the Electron launch vehicle developed by Rocket Lab [31] and started to be more frequently proposed nowadays for small and medium rocket engines.  
Micro electric pump feed cycle can be considered unconventional from the perspective of micro and nanosatellite development. In such a system, low voltage pressure is maintained in a way to provide propellant to the pump at required pump suction conditions, which is essential for stable feed operation and to protect against pump cavitation and pressure pulsation. Low propellant storage pressure levels are needed for pump-fed systems in general, typically 0.07 to 0.34 MPa [32; 33; 34] and these values may slightly increase in the case of CubeSat small tanks. Much lighter tank structures are used in the case of pump-fed systems due to this required low storage pressure but they still come at the cost of high system complexity of the pump operation and the accommodated propellant feed lines. Although pump-fed systems are not widely used in the current time for CubeSats, possibly only proposed, the technological advancements in micro electric pumps development, such as the relatively low-cost micro electric pump [35] used in the proposed design, show the possibility to use this feed and pressurization technique on the scale of micro and nano spacecraft.  
Autogenous-pressurization will impose challenges especially considering the nature of EIL salt solutions. The observed fact of slow decomposition of some propellant mixtures, such as the ADN-based LMP-103S, leading to salt residues and solid particles precipitation in thrusters' valves impose design challenges and limitations that need to be carefully addressed. In the case of vaporization of propellant streams, the risks relating to operation stability are amplified due to the expected precipitation of salts, especially in the small feed tubing, microvalves, and pump. A range of solutions was proposed during the preliminary design and analysis phases, that are of a mechanical nature, such as adding proper filtration, incorporating synchronous flushing procedures, or more dedicated and accurate sizing for the tubes and piping in more sensitive areas to avoid such problems. EIL propellants with significantly high solubility and non-detonable nature would be highly appreciated, which was one of the reasons HNP225 was chosen for the development phases. However, more insights will be gained during the development and testing phases and more design iterations are expected to be carried out in the feed and pressurization system to counter development challenges.