A trade study on radiation exposure for a crewed mission to the jovian moon callisto

In support of the NASA Revolutionary Aerospace Systems Concepts (RASC) Human Outer Planet Exploration (HOPE) activity goal to investigate the technology required for future crewed missions to the outer solar system, a trade study for a mission to the Jovian moon Callisto was performed. Three different mission scenarios were developed, each with a different propulsion method, resulting in different mission durations. Nuclear thermal, nuclear electric, and fusion propulsion systems were considered. While the three mission scenarios were different in several ways including trajectory, spacecraft configuration, and whether or not an initial vessel was used to deliver supplies, each scenario included a crewed trip to Callisto beginning in late 2044 or early 2045 and a short surface stay, 29 to 120 days. For each scenario, the crew radiation exposure was evaluated. The radiation analysis for this trade study is described here. The effects of trip duration on the exposure levels are discussed as well as the advantages of avoiding solar minimum, i.e. the time in the solar cycle when the solar wind is at its minimum and interplanetary galactic cosmic ray (GCR) radiation is at its maximum. The benefits of choosing shielding material containing hydrogen and the possibility of using the hydrogen fuel tanks to shield the crew quarters are also discussed.