Whole body effective dose equivalent dataset for MAX and FAX shielded with Common Aerospace Materials in deep space

Materials have a primary purpose in the design of space vehicles, such as fuels, walls, racks, windows, etc. Additionally, each will also affect space radiation protection. Using the On-Line Tool for the Assessment of Radiation in Space (OLTARIS), version 3.5, analysis package, this article includes the whole body effective dose equivalent (ED) data from human phantoms being shielded by 59 aerospace materials for deep space travel. To represent the average anatomy of an astronaut, the Female Adult voXel (FAX), 2005 version, and the Male Adult voXel (MAX), 2005 version, human phantoms are used. A simple spherical geometry, which is composed of a spherical shell with the human phantom placed in the center, is also used. Eighteen shielding thicknesses ranging from 0.01 to 1000 g per centimetres squared are evaluated and the ray distribution used in this study is the 1002 geodesic. All aerospace materials are categorized into four groups: metals, polymers, composites, and fuels, hydrides, and liquid gases. These materials include common fuels and propellants used in space travel, engineered materials developed to significantly increase the absorption of secondary radiation, and materials in the early stages of development for the purpose of meeting both shielding and structural needs of future spacecraft missions. The data in this article is used for the paper, “Evaluating the Effectiveness of Common Aerospace Materials at Lowering the Whole Body Effective Dose Equivalent in Deep Space,” [13].

Common Aerospace Materials at Lowering the Whole Body Effective Dose Equivalent in Deep Space," [13].
© 2019 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).

Data
The data compiled in this article is the whole body effective dose equivalent (E D ) absorbed within the male adult voxel (MAX) [1] and female adult voxel (FAX) [2]human phantom calculated using the On-Line Tool for the Assessment of Radiation in Space (OLTARIS) [3e5], version 3.5. The 59 shielding materials (Table 1) evaluated are separated into four categories: metals, polymers, composites and fuels, hydrides and liquid gases.
The metals evaluated were chosen as structural materials that can resist, without excessive deformation or failure, stresses that occur during launch, re-entry, deployment and service. Martian and Lunar regloith were included in this category due to their large metals components and similar densities. The fuels, hydrides and liquid gases include common fuels and propellants that will be needed on deep space missions. This category also includes the shielding materials that have been shown to have the ability to efficiently absorb the energy of the solar and cosmic radiation particles, as well as minimize the formation of secondary radiation. The Polymers and composites include the materials that have been suggested as potential materials for deep space missions [6]. This category also includes engineered materials developed to significantly increase the absorption of secondary Specifications Table   Subject Aerospace  Table 2 shows the E D using galactic cosmic rays (GCR) boundary condition and Table 3 shows the E D using the solar particle events (SPE) boundary condition.

Model descriptions and geometry
OLTARIS, version 3.5, analysis package is used to evaluate this detailed radiation field. Developed by the National Aeronautics and Space Administration's (NASA) Langley Research Center to enable engineering and research related space radiation calculations. This tool allows the user to easily choose the boundary condition, shielding material and geometry, mission duration, response function and human phantom. Advanced space vehicles and structures can also be evaluated using their thickness distribution analysis tools. Each simulation used the 1002 geodesic ray distribution and was run using OLTARIS 0 Ray-by-Ray method. The model geometry included a human phantom placed in the center of a hollow spherical shell. Each material is defined within OLTARIS using its composition and density. Materials compositions and densities can be requested by contacting the corresponding author. Because the energy of the GCR and SPE particles are measured in MeV and atomic bonding is in the eV range, the atomic arrangement of the material is not used in the defining of a material.

GCR boundary condition
Galactic cosmic rays (GCRs) are composed of fully ionized stable and meta-stable isotopes. Although they include every naturally formed element, not all elements are in high abundance. Protons account for roughly 91% of the total flux, alpha particles account for approximately 8%, and heavier particles account for less than 1% of the total flux. Even though the abundance of heavy ions is relatively low (<1%), they can contribute approximately 86% of the dose equivalent in a lightly shielded vehicle like a space suit [7]. For heavier shielded vehicles, this percentage drops off due to energetic light ions created from nuclear fragmentation of these heavy ions from interaction with spacecraft materials.
The GCR model used in this study is the Badhwar-O'Neill 2010 [8,9] model, which is based on the fitting of existing balloon and satellite measured energy spectra to accurately account for the solar modulation of each element through the heliosphere. This model determines the GCR differential energy spectrum for elements from hydrogen to nickel at any given radial distance from the sun.
The 1977 solar minimum boundary condition, with particles ranging from hydrogen to 58 Ni, is the event used in this research. The abundances for species heavier than nickel (Z > 28) are typically four orders of magnitude less than that of 56 Fe [10] and therefore are not included in this boundary condition. During a solar minimum, the sun's magnetic field is stable which allows for infiltration of GCRs into the solar system and increases the flux of GCRs. During a solar maximum, the chaotic magnetic fields decreases the flux of GCRs but increases SPEs.

SPE boundary condition
Solar particle events (SPEs) are composed of a large number of protons accelerated by the Sun's magnetic field and released as coronal mass ejections. Very large coronal mass ejections are relatively rare with less than three events occurring within an 11-year solar cycle [6]; however, SPEs are sporadic in nature. There are smaller, more frequent coronal mass ejections that occur throughout a solar cycle. With such a wide variance in magnitude, duration and composition of SPE protons, a large historical SPE was chosen as the design basis event for this study.
The SPE event used in this article was recorded by the GOES 7 spacecraft and occurred between the October 19e24, 1989 [11]. This event includes the recorded proton flux for energies greater than 10, 50 and 100 MeV and is one of the highest magnitude SPE events observed in the past 30 years. Heavier elements and electrons were also measured as part of the SPE flux, but due to their limited abundances only protons are included in this model.