High-energy fuels for enhanced propulsion
Current rocket propulsion systems can be divided into three main categories based on the type of fuel used: liquid, solid and hybrid. While each has its share of advantages making them suitable for certain space applications, solid propellants are relatively stable and easy to store. However, their performance is still lower than that of liquid propellants. Recent breakthroughs in materials with high-energy–density have made the development of high-performance solid propellants a viable proposition. European researchers initiated the 'High performance solid propellants for in-space propulsion' (HISP)(opens in new window) project to exploit their full potential. The goal was a similar performance to the most efficient liquid propellants and an increase of 10 % compared to existing solid ones. The HISP researchers experimentally analysed four aluminium-based high-energy–density fuels: micrometric aluminium, nanometric aluminium, activated aluminium and aluminium hydride. To overcome intrinsic performance limitations, ammonium dinitramide(ADN) as oxidising agent seemed a promising alternative to the commonly usedammonium perchlorate. One of the combustion products of propellants containing AP is hydrogen chloridethat causes corrosion around the launch base and is harmful to the environment. On the other hand, ADN is highly reactive with some polymeric binders. Glycidylazide polymer, as the most suitable binder, allowed development of a propellant with the potential to increase by more than 30 % the payload mass of the Vega launcher. The HISP industrial partners have made improvements in the manufacturing methods for these materials to enhance their chemical stability and achieve the desirable compatibility. Although not ready to be scaled up, the prospect of their industrialisation was evaluated. Still, reference missions have been selected to determine overall mission benefits of the new solid propellants. HISP has strengthened the competitiveness of the European space propulsion industry. By increasing the technological readiness level of solid propellants containing high-energy–density compounds, it will help make new missions to distant destinations possible, thus helping the EU to push the frontiers of space exploration.
