Author ORCID Identifier

0000-0003-4639-7990

Date of Graduation

8-2020

Document Type

Dissertation (PhD)

Program Affiliation

Medical Physics

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

Stephen Kry

Committee Member

Charles Willis

Committee Member

Fada Guan

Committee Member

Jingfei Ma

Committee Member

Leif Peterson

Abstract

Exploration of interplanetary space presents dramatic hazards to human survival.

Space radiation hazards outside the protection of the Earth’s magnetosphere can

produce both acute and chronic health risks and thus become limiting factors for

NASA’s planned mission to Mars by the 2030s. Radiation exposure on a Mars mission

is delivered primarily by high energy ions from galactic cosmic rays and moderate

energy protons from solar particle events. The chronic radiation dose due to galactic

cosmic rays on a typical Mars mission is on the order of 1 Sv, and additional acute

radiation dose from solar flares can reach over 4 Sv, which is a potentially lethal dose.

Hence radiation protection is a critical concern on these types of missions.

Various methods of radiation shielding have been proposed, from simple passive

shielding via materials such as water, polyethylene, or aluminum, to active shielding

systems comprised of electromagnetic fields. The concept of active magnetic shielding

is to use high-temperature superconducting coils to induce very high magnetic fields

around the spacecraft. The induced magnetic field will deflect incoming charged

particles (solar particles and galactic cosmic rays), thereby reducing the particle

fluence rate and radiation dose to astronauts behind the shield.

This project developed a model for determining the effectiveness of active

magnetic shielding in reducing radiation dose to astronauts on an interplanetary

mission. This research includes Monte Carlo simulations to determine the

effectiveness of magnetic shielding in decreasing effective dose to astronauts in a

variety of mission scenarios. Dozens of permutations of mission type, mission

duration, solar cycle, shielding configuration, magnetic field, crew sex, crew age, and

phantom type were simulated in GEANT4 to conduct a sensitivity analysis on the effect

of varying each parameter on total crew effective dose for the mission.

Results indicate that magnetic shielding can reduce effective dose to astronauts

on an interplanetary mission to within NASA’s current limits, given a magnetic field of

7 T and/or advanced astronaut age. The detailed results serve to inform the human

spaceflight community on the utility of active magnetic shielding as compared to

passive or no shielding, based upon an end-to-end system model and comparison of

several active magnetic shielding strategies.

Keywords

space radiation, radiation protection, radiation shielding, human spaceflight

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