Green Comparable Alternatives of Hydrazines-Based Monopropellant and Bipropellant Rocket Systems

Concepts are presented for “green” (with reduced hazards) replacements for monopropellant hydrazine propulsion systems and for hypergolic bipropellant systems while maintaining similar performance. At the onset of the “green propulsion” age, “green” alternatives to hydrazine propulsion have been emerging. The introduction rate of these into space systems is very slow due to the conservatism of the space propulsion industry. The concept presented here for monopropellant hydrazine systems offers gradual conversion to “green propellants” by dual capability of conventional hydrazine systems and ammonium dinitramide (ADN)-based systems. An initial risk reduction program has been carried out for materializing the concept. It includes proof of concept of dual use of all propulsion system parts. Materials compatibility and actual operation have been demonstrated. For bipropellants, we present the emerging “green” hypergolic system based on kerosene and peroxide, similar in performance to MMH/N2O4. Results of the proof-of-concept and development model systems are presented. The experimental results of various engine types demonstrate the capability to operate in both pulse and steady-state modes and the ability to produce different thrust levels. The fuel and oxidizer show very robust hypergolicity and short ignition delay times, as well as characteristic velocity efficiency exceeding 98%

An Overview of Recent Investigations on Gel Fuels

Gel fuels are interesting candidates for ramjet propulsion systems due to their performance, safety and handling benefits. The addition of metal particles such as aluminum or boron offers the possibility to increase the flight performances due to their high volumetric energy content. On the other hand, in comparison to typically used Newtonian liquid fuels, significant differences in flow, atomization and combustion behavior exist. The paper presents a survey of various studies on main aspects of gel propulsion, i.e. rheology, sedimentation, flow properties, spray behavior, single droplet combustion and spray combustion and concentrates in investigations conducted by the research groups of the authors

An Overview of Investigations on Gel Fuels for Ramjet Applications

Gel fuels are interesting candidates for ramjet propulsion systems due to their performance, safety and handling benefits. The addition of metal particles such as aluminum or boron offers the possibility to increase the flight performances due to their high volumetric energy content. On the other hand, in comparison to typically used Newtonian liquid fuels, significant differences in flow, atomization and combustion behavior exist. The paper presents a survey of various studies on main aspects of gel propulsion, i.e. rheology, sedimentation, flow properties, spray behavior, single droplet combustion and spray combustion and concentrates in investigations conducted by the research groups of the authors