Description: Long duration exploration vessels, staging stations such as the Lunar Orbital Platform-Gateway, and sustained Lunar or Martian surface operations will benefit from an on-demand fabrication process that incorporates recycling for material reuse. On a 1,100-day mission to Mars and back, for example, an estimated 30% of all components are amenable to in-space fabrication. With a recyclable feedstock, this would yield a 97.7% reduction in the required spare parts mass. The goal of this project is to develop and demonstrate a novel reversible material system that constitutes reusable feedstock for in-space fabrication. The proposed material is composed of microparticles that bond and debond using a reversible chemical process. Two microparticle feedstocks are required, each functionalized with complementary chemistries of the reversible reaction. When mixed in a mold, the microparticles bond spontaneously via a ‘click’ reaction, with a rapid reaction rate and high efficiency to form a consolidated article. To return the article back to feedstock, the microparticles can be debonded via the reversible click reaction though application of modest heat and separated for storage before reuse. The state-of-the-art for in-space recycling and fabrication is the Refabricator, which combines a plastic recycling system with a 3D printer. Recently installed on the International Space Station, it allows astronauts to recycle plastic waste into 3D printer filament to use for article fabrication. Unfortunately, most 3D printed plastics have highly anisotropic material properties. As a result, 3D printed objects are generally not subjected to high loads or used for critical sub-assemblies. The proposed reversible material system represents a fundamentally different, innovative approach for in-space recycling and fabrication. As the material is composed of bonded microparticles consolidated into an article, the properties of the developed material should be isotropic, facilitating their use in a broader range of applications. Initial material development efforts have been carried out in FY19 (LaRC IRAD, $86K). These efforts have focused on early development of the reversible material system through progress of several key components. Continued work is still needed to bring all the components together and optimize the system parameters of the reversible material. This work intends to closely couple computational materials modeling with the ongoing experimental efforts to accelerate the materials development process.

Benefits: Fundamentally different approach from 3D printing, which is limited by isotropic mechanical properties and high energetic costs for recyclability. Microparticle synthesis has been demonstrated, but optimization of polymer coating is needed to improve bonding of microparticles for article formation