Abstract
Fission is a high power density energy source for space applications capable of enabling high power levels for long durations which is desirable for surface power and in-space propulsion methods for crewed missions. Nuclear thermal propulsion (NTP) and nuclear electric propulsion (NEP) are advanced, in-space propulsion technologies capable of higher efficiencies than traditional chemical engines, making them well suited to enable crewed interplanetary missions. In NTP systems, the reactor acts as a heat exchanger and directly heats a hydrogen propellant to provide high thrust (10s – 100s klbf) at high efficiencies, i.e. specific impulse (> 800 s). NEP systems use a reactor to generate electricity to power high-efficiency electric propulsion thrusters which enable nearly a magnitude greater specific impulse (> 2000 s), but at reduced thrust (0.001 – 1 lbf). Because of these attributes, space nuclear propulsion technologies have the capability to reduce trip times on the order of half of that compared to the highest performance chemical systems and there has been renewed interest in the development of these systems for future NASA or defense applications within the U.S. There has been extensive development for both NTP and NEP systems through historic space nuclear propulsion programs, however none of these programs have quite reached the development status desired for implementation of either system in modern missions. Primary hurdles to reactor development have centered around materials development for the extreme operating conditions desired for high-performance space reactors. In this presentation, the state of the art, lessons learned, and remaining knowledge gaps from historic NTP and NEP development programs are summarized. Based on this overview, critical components for each reactor and remaining materials development challenges are identified.

Keywords: nuclear thermal propulsion, nuclear electric propulsion, technology maturation, reactor, testing

Bio
Kelsa Benensky Palomares, Ph.D. is the Nuclear Systems Engineering Lead for the Advanced Projects Group of Analytical Mechanics Associates, Inc. (AMA). Dr. Palomares has a background in the design, testing, and experimental investigation of new and novel concepts for nuclear thermal propulsion (NTP) through NTP development programs at NASA Marshall Space Flight Center, Oak Ridge National Laboratory, and the Center for Space Nuclear Research. Activities have included re-design and operational verification of MSFC’s compact fuel element environmental test (CFEET) and co-authoring ORNL/LTR-2017/119, “A Preliminary Nuclear Thermal Propulsion Fuel Qualification Plan”, to guide the production, irradiation testing, and verification of NTP fuel elements for the Department of Energy. She has recently participated as the reactor-subsystem lead for an industry nuclear thermal propulsion flight demonstration study commissioned by NASA and led by AMA and served as a peer reviewer for the National Academy of Science Engineering and Medicine’s report “Space Nuclear Propulsion for Human Mars Exploration”. She currently provides subject matter expertise to ongoing reactor development efforts for NASA’s space nuclear propulsion (SNP) project. Dr. Palomares has received degrees in Mechanical Engineering (B.S.), Nuclear Engineering (B.S.) from the Pennsylvania State University, as well as Materials Science and Engineering (MS) and Nuclear Engineering (Ph.D.) from University of Tennessee.

Advanced Projects Group, Analytical Mechanics Associates, Huntsville, AL, 35806