Pourable and destroyable Cosmic Ray radiation shield for spacecraft
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Historically, materials such as lead, tungsten, and iron have been used in spacecraft to shield scientific detectors from Cosmic Rays. These materials work well when re-entry to Earth is not an issue. The typical strategy is to have a controlled descent of the spacecraft or to have extremely limited shielding, if any, due to NASA's requirement that all impacting parts must impact with no greater than 15J of energy. Given the nature of this mission neither a controlled descent nor having no shielding was not an option. This is the issue Wichita State University (WSU) nuSOL (Neutrino Solar Orbiting Laboratory) team is facing for its 3U CubeSat demonstrator. The CubeSat will be equipped with scientific equipment with the purpose of detecting solar neutrinos, and the less background noise from Cosmic Rays the better the study will be. Through simulations, density tests, and burn tests, WSU was able to develop an epoxy-based shield doped with either iron or tungsten powder. The simulations were conducted by firing electrons, protons, alpha particles, and oxygen and iron nuclei into the shield material with energies ranging from 1MeV until consistent failure rate using Geant4 (Geometry and Tracking). The standards for these simulations are the base epoxy at 1.15g/cm3 to solid steel at 8g/cm3. Mixing tests have determined for iron, a density of 4g/cm3 is achievable, which is 53% iron by volume. tungsten epoxy with a density of 7.5g/cm3 is more easily achieved, and results in 40% tungsten by volume. These ratios are concrete in texture, pourable, and homogeneous. With the data collected, several prototypes of varying densities were made by pouring the mixture into molds. The results indicate that the 4g/cm3 iron doped epoxy does not have a 90% punch-through until 40MeV for electrons and 74MeV for protons. The tungsten fared better at 1GeV and 90MeV respectively, with the proton never exceeding 94% punch-through at 1GeV. The steel 90% fail are 250MeV for electron and 125MeV for proton. Due to the current requirements of the mission, the densities of iron 4g/cm3 and tungsten 7.5g/cm3 have been determined to be the best fit for the nuSOL project. Both materials have been tested to determine if they burn upon re-entry and neither shield survived past 425°C. A vibration test is planned to ensure survival of launch along with a test to measure the science package and shielding capabilities for accelerator particles to ensure efficiency.
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Presented at the 73rd International Astronautical Congress, IAC 2022, 18 -22 September 2022.
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2022-September

