Review and Perspectives of “green” Self-Pressurizing Propellants for In-Space Propulsion and Their Applicability to Orbital Stages

Green Propulsion is an increasingly prevalent trend in the space industry that has experienced significant growth in recent decades.The shared objective of researchers is to identify suitable alternatives to existing liquid propellants for space applications, which are toxic and difficult to manage during ground operations.Research and industry have explored a wide range of options and, especially in the last few years, there has been a clear push from the market and the overall space sector to utilize cheaper and simpler systems.Numerous alternatives are emerging as advantageous for a variety of applications.Green propellants are typically utilized for in-space propulsion applications that necessitate high thrust and short transfer durations and over the years, around the world, researchers and industries have tested dozens of different propellants.Recently there is an increased interest in exploiting a particular characteristic of some compounds, the so-called self-pressurization, i.e. the property of compounds with a high vapor pressure at conventional operating temperatures of possessing an inherent feeding pressure.The principal advantage of systems based on these propellants is their self-pressurizing capability, which eliminates the need for external pressurization sub-systems, resulting in simpler and more compact designs.The present study evaluates the relative performance of many of these compounds as propellants for an Orbital Stage reference scenario.