Polyethylene (PE), due to its high hydrogen content relative to its weight, has been identified by NASA as a promising radiation shielding material against galactic cosmic rays and solar energetic particles. Carbon nanotubes (CNTs), due to their small diameter, high-mechanical strength, and high-electrical and thermal conductivity, are recognized as the ultimate carbon fibers for high performance, multifunctional composites. Prior studies failed to produce the CNT/polymer composites that fully exploit nanotubes' outstanding mechanical, electrical and thermal properties because of poor dispersion of nanotubes in polymer matrices and poor adhesion between nanotubes and the polymer matrix,. Zyvex has developed a versatile and non-damaging chemical platform that allows us to engineer specific nanotube surface properties to permit homogeneous dispersion of nanotubes in various solvents and polymer matrices, and enables the significantly enhanced adhesion between nanotubes and the polymer matrix. The major innovation of our technical approach is to marry these two outstanding materials using Zyvex's chemical platform technology to produce a novel CNT/PE complex composite that not only has high radiation shielding performance, but also has high mechanical strength, high electrical conductivity, and improved thermal stability. Multifunctional CNT/PE complex composite will find broad applications in shielding humans in spacecrafts and habitats.