Radiation shields could be fabricated in situ at relatively low cost.
It has been proposed to fabricate polymer/soil composites primarily from extraterrestrial resources, using relatively lowenergy processes, with the original intended application being that habitat structures constructed from such composites would have sufficient structural integrity and also provide adequate radiation shielding for humans and sensitive electronic equipment against the radiation environment on the Moon and Mars. The proposal is a response to the fact that it would be much less expensive to fabricate such structures in situ as opposed to transporting them from Earth.
Prototype polymer/soil composite bricks have been fabricated on Earth. Transport calculations have shown that the addition of polymeric materials to soil significantly improves the radiation-shielding properties of the resulting composites due to the high hydrogen content of the polymeric constituent. Mechanical testing and hypervelocity-ballistic testing of the proposed composites have demonstrated that structural properties can be improved by a factor of 10 when compared to bricks consisting of only the planetary soil.
A typical composite of this type consists of 5-to 95-weight percent polymeric material and 95-to-5-weight percent of the local planetary soil. The polymeric and soil constituents are thoroughly mixed, heated to slightly over the melting point of the polymeric constituent and pressure is applied to ensure complete infiltration of the polymeric material within the pores of the soil particles. Through suitable choice of pressure and temperature, the resulting polymer/soil composite can be made nearly free of voids.
This work was done by Subhayu Sen of BAE Systems for Marshall Space Flight Center. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Manufacturing & Prototyping category.