ANALYZING MISSION OPPORTUNITIES FOR EARTH TO MARS ROUNDTRIP MISSIONS

NASA and industry are studying future human exploration missions to Mars that occur across multiple mission opportunities between 2030 to the late 2050's. Aerojet Rocketdyne (AR) has been analyzing ballistic transfers for Earth to Mars for roundtrip missions over an even grid of departure dates and transfer times during those opportunities. Aerojet Rocketdyne's efforts are an attempt to ensure the most optimum planetary alignment conditions were characterized in order to explore the performance capabilities for hybrid solar electric -chemical, chemical, and nuclear thermal propulsion. AR has been working with NASA on several approaches to Mars mission architectures that use various forms of the three propulsion systems. All three of these propulsion systems employ trajectories that are semi -ballistic or ballistic during the Earth departure, Mars arrival/departure, or Earth return arrival. A combination of the NASA Copernicus trajectory program and orbital mechanics calculations are used to determine the delta-velocity (delta-V) values that will be used in mission architecture trades. Departure dates and transfer times are utilized as inputs into NASA's Copernicus trajectory design software suite and used to solve Lambert's boundary-value problem to fmd the optimal and non -optimal transfers between the two planets. The Copernicus Lambert solver gives four solutions. The solution with the least total delta-V is the objective for the analysis that has been performed over several 7-8 year planetary synodic alignments. Both conjunction and opposition class trajectories have been analyzed with Copernicus to develop a Mars mission data book going out to 2055. This paper will discuss the results of preparing this mission data book in order to provide the needed information for analyzing the impact of propulsion system performance on Earth-Mars missions into the 2050's and beyond. Some trade study results based on using the methodology developed with the Earth -Mars mission data book are in the final section of the paper for a Nuclear Thermal Propulsion (NTP) system and Mars crew vehicle architecture.