Gap Cancer 12: What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)?
Last Published:  11/23/20 11:55:10 AM (Central)
Responsible Element: Space Radiation (SR)
Status: Closed
Closure Rationale
Domain transferred to NASA's Advanced Exploration Systems - Space Radiation Analysis Group.
Closure Documentation:
No Closure Documentation Available
Description

Initial State of Gap:

 

Cancer risk projection models rely on an accurate description of the particle fluxes found throughout critical body tissues during spaceflight missions.  As external space radiation passes through spacecraft walls and structures and through tissues of the body, the radiation that impacts target cells is considerably different from the external radiation environment. It is essential to understand both the primary space radiation environments and radiation transport to predict and assess risk. The new NASA quality factors are described as a function of charge and energy rather than the integrative quantity of LET.  Radiation transport codes require an accurate nuclear cross section database, accurate and efficient numerical methods, and in-flight measurements to validate code predictions. While, the overall heavy ion flux and integrated dose and dose equivalent are well described at this time, the evaluation of particles of Z<1 including neutron, pion, muon, electron and positron production and transport as well as light charged particle production and transport requires further refinement. These particles are particularly important in assessing the radiation field in thick target configurations such as ISS, Mars transfer vehicles, and the Martian atmosphere.  Simulation of in-space environments at ground based facilities relating crew exposure to cell and animal models is essential in reducing uncertainties and validating countermeasures related to mixed field chronic exposures. 

For current astronaut risk assessment, end-to-end model results are normalized to area dosimeters on the International Space Station (ISS).  The Cancer risk models require more detailed information than area dosimeters provide with respect to secondary radiation including neutrons, pions, muons, electrons and positrons.  The normalization procedures ensure cancer risk estimates are consistent with available dosimetry providing an end-to-end model uncertainty within 15%.  When direct model evaluation (without normalization) is used in validation and uncertainty quantification efforts or projection of exposures, integrated model uncertainties ranged from 10% - 50% and includes uncertainties associated with GCR and geomagnetic field models, nuclear physics and transport codes, shielding mass distribution of the ISS and dosimeter response.  Improvements in environmental models in coordination with the Science Mission Directorate and improvement in transport codes especially with the transport and production of neutrons, light ions, and other particles on Z<1 will improve the predictive capability of exposure risk and support verification of design requirements.

 

Approach:

Research supports the development and validation of an accurate nuclear cross section database and numerical transport methods with an emphasis on neutrons and other Z<1 particles as well as light ions. Operational, experimental, and pre-cursor measurements are used to extensively validate radiation transport code predictions and identify major knowledge gaps. SR relies on data from ISS operations, scientific pre-cursor planetary missions and ground-based cross section and thick target experiments for validation. Estimates of particle tissue environments found in space must be adequately simulated in ground based facilities to support extrapolation of experimental results to mission relevant exposures. 

 

 

Target for Closure
       
    • Development and/or validation of environmental models, nuclear cross section models and databases, and numerical transport methods for accurate assessment of secondary radiation environment within tissue with projected/predictive accuracy of +/- 15%.   
    • Integration of methods into a collaborative design and analysis framework (Cancer 13).
    • Development of requirements and methods to simulate induced radiation tissue particle environments in ground based experiments including GCR simulations.

Mappings
Risk Risk of Radiation Carcinogenesis
You are here! Gap Cancer 12: What quantitative models, numerical methods, and experimental data are needed to accurately describe the primary space radiation environment and transport through spacecraft materials and tissue to evaluate dose composition in critical organs for mission relevant radiation environments (ISS, Free-space, Lunar, or Mars)?
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Documentation:
No Documentation Available