State of Research in a Pulsed Hybrid Nuclear Propulsion Engine Author: Rob Adams / Propulsion Research Engineer / NASA Background: There is great potential in nuclear reactions as a source of energy for driving an in space propulsion system. Many studies, models, and experiments have been conducted over the preceding decades and while much has been learned, significant obstacles remain to be resolved to realize a nuclear propulsion system. Proposed fusion systems are particularly attractive due to their high specific power and efficiency but have been hampered by instabilities and the high energy density barrier for breakeven energy production. It may be possible to use a coupling effect between fission and fusion reactions to lower the energy barrier to breakeven for a hybrid nuclear reaction. It may also be possible to generate this type of reaction in a pulsed power z-pinch system capable of being flown on a deep space exploration vehicle. Objectives: The objective of this author’s work is to explore the physics of fuel implosion and identify a potential parameters space in which breakeven hybrid nuclear reactions can be achieved at minimal peak driving current. This ties into the larger effort of the associated research team of demonstrating the key technologies for a pulsed fission fusion engine. Methods: The author makes use of multi-physics modeling software to simulate the physical processes of the implosion of candidate fuel configurations. This is coupled to theoretical analysis and anchored to empirical data from literature. Results: The author presents current progress in fuel configuration design, parameter space assessment, analysis, and model anchoring to literature. The author also presents progress of the greater pulsed fission fusion engine team. Conclusions: While there is still work to be done to refine various aspects of a pulsed fission fusion engine, the concept shows promise. The potential is for a specific power on the order of 10-20 KW/kg and a specific impulse of a few 10,000’s of seconds. This could be a tremendous step forward in capability and would open up many exciting new possibilities for the exploration of deep space.