Space Radiation Risk Reduction through Prediction, Detection and Protection
Paper i proceeding, 2021
To enable the planned rapid growth of both government and private operators in space, including satellites, space tourism and manned missions to the Moon and to Mars, a realistic and holistic approach to radiation risk reduction is needed. In deep space, ionizing radiation from Galactic Cosmic Rays (GCRs), which originate outside the solar system and Solar Energetic Particles (SEPs) from the sun pose a critical threat to human life and equipment. The composition and energy spectra of the radiation from these two sources are different and must be considered separately. GCRs provide a chronic, slowly varying, highly energetic background source of High-Z high-Energy (HZE) particles, while the Sun's activity varies with an 11-year cycle during which the Sun produces Solar Wind (SW) at varying intensities. The SW influences GCRs, since the GCRs are at maximum intensity during solar minimum when the decreased intensity of the solar wind causes less attenuation. In addition to the SW, there are solar events such as solar flares and coronal mass ejections (CMEs), which increase during solar max. These events give rise to SEPs, which pose a danger both to humans and electronics in space. It is therefore very important to be able to predict, forecast and measure the SEPs to apply the best possible protection for humans and electronics. Currently, the only proven and practical countermeasure to reduce the exposure to GCRs and SEPs is passive shielding. However, the presence of passive shielding does not always reduce the radiation risks for HZE particle exposure, e.g. metal shielding can increase the effective dose behind the shielding. The basic physics to estimate the shielding efficiency is straightforward as the energy loss of heavy ions in the shield is caused by electron and nuclear interactions, which can be approximated by simple stopping power and total reaction cross section formulas. It is therefore easy to show that a hydrogen rich material is best for charge particle protection. To increase shielding against secondary neutrons, the shielding material should also contain additives with high neutron capture cross section, e.g. Boron-10. Cosmic Shielding Corporation (CSC) provides the first holistic commercial solution to radiation risk reduction for both humans and electronics. CSC can predict SEPs using a modified version of MAG4 program, developed for the NASA Space Radiation Analysis Group (SRAG), which gives the likelihood of major solar flares, CMEs, and SEPs occurring up to 48 hours in advance. Furthermore, simulations of radiation transport through the spacecraft material, electronics and crew can be performed to estimate what possible damage an event can cause. Finally, we offer an improved version of a state-of-the-art, ultra-high molecular weight (UHMW) polyethylene composite material RFX-1, developed by NASA and assigned to CSC, which can either act as the main structural element of a spacecraft or habitat, or as a shielding layer on top of other structural materials. The improved version of RFX-1 is a lightweight Polyethylene composite with multifunctional strength, thermal management, ballistic impact resistance, low flammability, a high melting point and almost three times higher Ultimate Tensile Strength (UTS) then traditional Al alloys used in spacecraft. We also offer sophisticated embedded radiation detectors systems and Fiber-Optic Bragg Grating sensors for real time Prognostics and Health Management (PHM) of the shielding efficiency and mechanical strength.