Fundamental Architecture and Analysis of Photofission Ramjet Propulsion

Abstract

The ramjet demonstrates considerable utility for air-breathing propulsion systems. The ramjet benefits from air-breathing performance and minimal complexity in terms of moving parts. The conventional ramjet system functions based on stored chemical propellant. However, non-chemical strategies of imparting energy to the propulsive fluid, such as nuclear fission offer the advantage of increased energy density relative to chemical schemes. The concept of incorporating nuclear fission into a ramjet propulsion system has been a subject of interest from a historical perspective. Traditional fission occurs through neutrons with an appropriate kinetic energy interacting with heavy nuclei, such as uranium. However, there are many issues inherent with neutron-initiated fission. The fission reactions must be sustained by a source of neutrons with suitable kinetic energy. Neutron moderation involves the additional incorporation of various materials for modifying their respective energy kinetic levels, which can negatively impact the propulsion system in terms of both mass and system complexity. Therefore, photofission constitutes a paradigm shift relative to traditional neutron initiated nuclear fission. The proposed architecture advocates photofission derived by an ultra-intense laser as an energy source for the propulsive fluid of a ramjet. The primary physics that elucidate the phenomena of photofission are comprehensively entailed. With the foundation of the physics describing photofission presented, a fundamental analysis of the proposed photofission ramjet is incorporated. A suitable application for a photofission ramjet propulsion system would be integral with an Unmanned Autonomous Vehicle (UAV). The resulting fundamental analysis of the photofission ramjet successfully demonstrates potential feasibility for future research, development, test, and evaluation. Introduction The design and development of a nuclear fission derived ramjet may be advanced in terms of feasibility through the incorporation of photofission. Photofission has been recently demonstrated relative to neutron-induced fission, which has existed as a preliminary aspect of the nuclear era. Photofission is initiated by an ultra-intense laser order of order of approximately 10W/cm targeting a heavy nuclei target, such as uranium-238 [Cowan et al. 2000, Ledingham et al. 2000, Schwoerer et al. 2003]. The photofission process involves the initiation of high-energy electrons, bremsstrahlung, and nuclear interactions [Cowan et al. 2000]. A notable advantage of photofission is that the target material can be uranium-238, which is the predominant isotope of uranium. By contrast, traditional neutron derived nuclear fission requires the use of uranium-235, which is a relatively much more scarce isotope of uranium. Another advantage of the photofission application is the observation that fission events are a direct consequence of targeted laser activity, not a difficult to control