A Half-Gigawatt Space Power System using Dusty Plasma Fission Fragment Reactor Robert B. Sheldon 1,2 , Rodney L. Clark 1 1 Grassmere Dynamics, LLC, Gurley, AL 35748-8909 256-776-9471 rod.clark@grassmeredynamics.com 1,2 RB Sheldon Consulting, Huntsville, AL 35803 256-6538592; rbs@rbsp.info Abstract. A dusty plasma nuclear fission fragment reactor employs a cloud of nanometer-sized dust of fissionable material inside a magnetized moderator. The negatively charged dust, free electrons, and positively charged ions form a 3-component “dusty plasma” that can be confined and manipulated as charged fluid. The nanometer dust has such a large surface to volume ratio, that it is capable of remaining solid at 3000K while radiating 10-100 GW of radiant power, as discussed in previous work. This ``nuclear light bulb” power source solves the intractable problems of previous designs: confining charged dust rather than hot gas; eliminating the need for quartz windows; and not requiring gas cooling. Unlike previous designs the radiation is in the near-infrared, so that conversion to electricity is inefficient. While Brayton-cycle power converters are often advertised as a space power solution, they require additional radiators and additional mass. Several recent technologies, however, can convert NIR into electric power at improved efficiency and with no moving parts. We model the conversion efficiency of a space system consisting of radiators, moderator, direct fission-fragment converter, and IR converter panels as a viable solution to the growing need for MW space power systems. Keywords: Fission fragment nuclear reactor, dusty plasma, mass to power ratio, infrared power conversion INTRODUCTION This paper complements the paper “A Six Component Model for Dusty Plasma Nuclear Fission Fragment Propulsion” by Clark and Sheldon (CS16) [1], where we look at the advantages of nuclear energy for space electric-power generation. The nucleonics and thermal design of a dusty plasma fission fragment reactor are discussed there, while this paper addresses the application of a DPFFR to a space power system. The two competing technologies for in-space power are currently solar and radioisotope thermal, which we discuss in turn. While various schemes have been proposed to extract the ~1.3kW/m 2 of solar radiant energy at Earth orbit, the relatively low power density combined with the ~30% efficiency of advanced solar panels, limit spacecraft to <100 kW power plants. Solar power drops another 75% if the spacecraft is to go to Mars, or 96% if it is headed for Jupiter, making solar panels infeasible for outer planet missions, for manned flight, for Discovery class spacecraft using electric propulsion, and in particular, for the VASIMR electric plasma propulsion engine [2]. Currently, missions to the outer planets use radioisotope generators based on Pu238, Sr90, or ESA’s proposed Am241 [3]. The power/mass ratios range between 2-5 W/kg, and the efficiency of the current generation of radioisotope thermal generators (RTG) hover around 7%, with improvements using either thermovoltaics or Stirling engines expected to achieve ~20%.[4] In either case, some 80-93% of the heat must be rejected by the in-space radiators, at the relatively low temperatures of the “cold” side, generally around 350K. A 100kWe (electricity generation), would then weigh some 20-50 tons, and must radiate somewhere between 500-