Effect of NTP technology levels on engine sizing for a 2005 piloted Mars mission

Previous vehicle mass studies were performed for Mars launch windows in the 2010--2018 time frame. Within the last year, a study was performed to determine the effects of various Nuclear Thermal Propulsion (NTP) engine and mission parameters on Initial Mass in Low Earth Orbit (MLEO) for a piloted Mars mission during the 2005 opportunity. Particle Bed Reactor (PBR) and Enabler-type reactors were compared. Parameters evaluated included engine thrust, number of engines, number of Trans-Mars Injection (TMI) burns, engine thrust/weight, engine out capability, engine burn time, and Isp. Earth and Mars departure dates and outbound and return travel times were optimized for a 240-day total interplanetary transfer time (long-duration stay mission). Parameters which were seen to reduce IMLEO included a greater number of perigee burns, multiple engines, and higher Isp. Optimum engine thrust varied substantially depending on the configuration. Engine models developed jointly by Rocketdyne and Westinghouse within the last year formed the basis for the Enabler thrust optimization study