Regolith-Polymer 3D Printing

NASA's new technique for generating recyclable feedstocks for on-demand additive manufacturing employs the high-yield reversibility of the Diels-Alder reaction between maleimide and furan functionalities, utilizing the exceedingly favorable interaction between specific chemical functionalities, often termed "click reactions" due to their rapid rate and high efficiency. Integration of these moieties within a polymer coating on epoxy microparticle enables reversible assembly into macroscopic, free-standing articles. This click chemistry can be activated and reversed through the application of heat. Monomer species can be used to incorporate these functionalities into polyimide materials, which provide excellent mechanical, thermal, and electrical properties for space applications. Copoly (carbonate urethane) has been shown to be a viable coating material in the generation of polymer-coated epoxy microparticle systems and is amenable to being processed through a variety of approaches (e.g., filaments and slurries for 3D printing, compression molding, etc.). The polymeric materials are grown from the surfaces of in-house fabricated epoxy microparticles. The thermal and mechanical properties of the microparticles can be readily tuned by changes in composition. There are a number of potential applications for this NASA technology ranging from use of these materials for recyclable/repurpose-able articles (structural, decorative, etc.) to simple children's toys. More demanding uses such as for replacement parts in complex industrial systems are also possible. For long term space missions, it is envisioned that these feedstocks would be integrated into secondary spacecraft structures such that no additional concerns would be introduced due to in-space chemical reactions and no additional mass would be required.

The Polymer Composite Material provides a method for using comingled plastics in a way that is not greatly impacted by changes in composition. Comingled plastics are used as a combination filler/binder material where low melting plastics are converted into binders with higher melting plastics serving as filler and structural reinforcements. The Polymer Composite Material is made by feeding the source materials into an extruder - a solid polymeric binder at a first feed rate and a solid filler at a second feed rate. The extruder (a) melts the solid polymeric binder, (b) mixes the melted solid polymeric binder with the solid filler, and (c) extrudes an extrudate of the solid polymeric binder and solid filler to form the composite material. The composite material has a binder to filler ratio determined by the first feed rate and second feed rate. The solid filler may be granular glass and the solid polymeric binder may be at least one of polypropylene, polyethylene, polyvinyl chloride, and polyethylene terephthalate. The material can be created in a range of densities using foaming techniques.

The technology is a method to increase automation of Additive Manufacturing (AM) through augmentation of the Fused Filament Fabrication (FFF) process. It can significantly increase the speed of 3D printing by automating the removal of printed components from the build platform without the need for additional hardware, which increases printing throughput. The method can also be leveraged to perform automated object testing and characterization. The method includes embedding into the manufacturing instructions methods to fabricate directly onto the build platform an actuator tool, such as a linear spring. The deposition head can be leveraged as a robotic manipulator of the actuator tool to bend, cock, and release the linear spring to strike the target manufactured object and move it off the build platform of the machine they were manufactured on. The ability for an object to 'fly off of the machine that made it' essentially enables automated clearing of the processed build volume. The technology can also be used for testing the AM machine or the feedstock material by successively fabricating prototypes of the manufactured object, and taking measurements from sensors as the actuator strikes the prototype. This provides automated testing for quality control, machine calibration, material origins, and counterfeit detection.

Researchers and other technology developers require regolith simulants that accurately emulate the properties of lunar, Martian, and asteroid soils to ensure that the processes, devices, tools, and sensors being developed will be usable in an active mission environment. To move toward higher fidelity regolith simulants, NASA has developed a system that takes typical regolith simulants and implants ions of relevant elements to better simulate the conditions of extraterrestrial soils. The ion implantation device developed here is composed of three key elements as shown in the figure below: two hopper and rotary valve elements and the acceleration grid structure. To perform the ion implantation, the system is first placed within a vacuum chamber, pumped down, and gases of the elements of interest are pumped into the chamber. The system then first passes a mass of granulated lunar regolith simulant through two stages of hoppers and rotary valves to condition the material. Key to the system is a process for interstitial gas removal (a source of contamination) as shown in the figure on the right. After conditioning, the regolith simulant is passed between two parallel electrodes under a high voltage, accelerating ions of the process gas and implanting those ions within the regolith simulant at controllable depths. The related patent is now available to license. Please note that NASA does not manufacturer products itself for commercial sale.

The NASA innovation is based on a tessellation algorithm to break up a curved surface into identically sized equilateral surface polygons. Tessellation is a term used in mathematics that describes the process of deconstructing a surface into non-overlapping shapes with no gaps. Using this NASA innovation enables a curved-surface truss structure to be designed and built using all identical module and strut components. A key feature of this innovation is the use of a “multi-nut” connector, which enables curved surface truss structures to be assembled from identical truss modules. Uniform truss modules with customizable multi-nut connectors can be used to construct a curved-surface structure. The algorithm is a design approach for any size or surface shape. The NASA innovation represents a major breakthrough due to: • Versatility to a variety of planar and curved structure shapes (cylinder, sphere, etc.) • Ability to change the shape simply by updating the “multi-nut” connectors • Commonality of truss modules and components • Ease of assembly • Efficiency of construction and weight • Robotic assembly and servicing. In addition to a range of space related applications – mirrors, antennas, habitats, storage containers, etc. – the innovation is also directly applicable to general terrestrial assembly of systems with curvature, including for example sports stadiums, airports, aquariums, convention centers, or bridges.