In-Space Manufacturing from Recyclable Feedstocks

How it Works: Long duration exploration vessels, such as the Lunar Orbital Platform-Gateway or sustained Lunar or Martian surface operations, will have evolving needs. This technology would enable on-demand fabrication of components to address these changing needs from a renewable feedstock. The feedstock for making these components on-demand could be integrated into the launch vehicle as secondary structure. Thus, once the secondary structure use has been realized, it could be returned to feedstock for subsequent component manufacturing needs. \n\nThe proposed system of materials generating the feedstock utilizes exceedingly favorable interaction between specific chemical functionalities, often termed click reactions due to their rapid rate and high efficiency. Click reaction between furan and maleimidemoieties is often utilized and will be integral to this work. This reaction can be considered as a lock-and-key with the furan being the lock (Functionality A) and themaleimide being the key (Functionality B). Monomer species will be utilized to incorporate these functionalities into polyimide materials, which have an extensive space heritage and provide excellent mechanical, thermal, and electrical properties for extra-terrestrialapplications. See attached documents for preliminary work conducted on this and literature related to it. This click chemistry can be activated and reversed through the application of heat. The entirety of the chemical structures that will be used in the proposed reactions is included in the attached documents. \n\nThese polymeric materials will be grown from the surfaces of in-house fabricated epoxy microparticles. Epoxies have excellent mechanical properties and are used extensively in aerospac eapplications. These microparticles will be generated using literature procedures. It is envisioned that these feedstocks would be generated terrestrially and integrated into secondary structure such that no additional concerns would be introduced due to in-space chemical reactions and no additional mass would be required. \n\nThis technology will require a mold for on-demand manufacturing. Digitally reconfigurable mold technology would enable fabrication of multiple geometries from a single mold. This approach replaces a solid surface with a multipoint surface consisting of actuating pins to enable changes in geometryand has been demonstrated for fabrication of glass, metal, and composite articles. This will be investigated in the future with subsequent funding. \n\nThe first year will have an initial period of steady, but slower productivity. A high performance period will occur from January-May, 2019 with two interns and significant contributions from civil servants, i.e., consolidated FTE over a smallerportion of the FY. Funding to retainthis level of effort through the entire FY would exceed available resources.\n\nKey Activities include:\nPreparing the lock and key functionalized epoxy microparticles\nCharacterizing polymer and particle interactions\nDesign of a digitally reconfigurable mold (to be pursued in 2nd year) \nProject Scope: Demonstration of a recyclable feedstock utilized to fabricate a secondary structure and a reconfigurable mold for on-demand fabrication would require significantly more time and resources than provided in a single year of IRAD funding. However, through the use of Agile Project Management, the greatest value activities will be the first pursued. This would result in likely demonstration of lock and key functionalized epoxy microparticles and a preliminary assessment of interaction strengths.\nRisks and Risk Mitigation: Interaction strength between functionalized epoxy microspheres high enough to enable fabrication of a useful article will be requisite for this technology. A series of parameters can be investigated to mitigate this risk including, among other possibilities: polyimide molecular weight, polyimide coating thickness, epoxy microsphere composition, size and size differences, thermal cycle. Beyond this, alternative shapes, i.e., materials with at least two unique axes, will be explored.

Description: Secondary structures on an exploration vessel, such as the Lunar Orbital Platform-Gateway, fabricated from reversible assembling materials could be repurposed for other mission needs once their utility was fully realized. This would be achieved through reducing the recycled component, e.g. a shelf surface, to a feedstock material through modest heating and separation. The feedstock, when confined in a mold environment, would retain the mold shape yielding a new component. \n\nThe Challenge: Missions beyond low-Earth orbit will have increasing demands on payload weight and multifunctional materials. One current approach toward reducing mission risk, especially for long-duration missions, is additive manufacturing techniques to enable generation of mission-critical articles (tools, infrastructure, etc.) on-demand; a supply of starting material that can be efficiently packed and the necessary processing equipment to manufacture articles would likely take up less space than individual articles. One limitation of this though, is that the current assessments treat the starting feedstock as finite. Thus, a manufacturing technique where articles could be generated, utilized, and returned to feedstock, without a significant energy budget requirement, for additional use would be highly beneficial. Multi-functional materials to enable exploration are core componentsof NASA's mission (see Technology Roadmap TA 07, TA10, and TA12) and align with Langley's Strategic Investment Plan. \n\nState-of-the-Art Additive Manufacturing: Additive manufacturing is a rapidly advancing art with significant advances toward generation of materials from organic and metallic starting materials. Most additive manufacturing techniques involve a material (or energy) source that is raster scanned across an objective area. Resultant articles are generated layer-by-layer, which often results in anisotropic mechanical properties. This limitation can be mitigated through the use of secondary processing requiring additional processing infrastructure and energy. Another restriction is articles, once generated, cannot be returned to starting material without energetic cost. Research is currently underway toward recycling thermoplastic materials and the Refabricator will be launched to the International Space Station in the near future. Although this approach shows promise, it is anticipated that the work proposed here would extend capabilities for in-space manufacturing to broader feedstocks, more extensive article geometries, and potentially greater throughput. Recently, the use of in-space manufacturing along with recyclable feedstocks for a nominal 1,100 day mission to Mars and back was determined to enable a reduction in required mass for spare parts amenable to in-space manufacturing (approximately 30% of all required spare components) of 97.7% (AIAA Space 2016,https://arc.aiaa.org/doi/10.2514/6.2016-5394). Development of a manufacturing technique that can generate precise, mechanically robust articles that could be returned to feedstock for use in subsequent article manufacture would be highly desired for exploration mission planning. This could reduce payload and energy requirements without sacrificing mission capabilities. Development of a manufacturing technique that can generate precise, mechanically robust articles that could be returned to feedstock for use in subsequent article manufacture would be highly desired for exploration mission planning. This could reduce payload and energy requirements without sacrificing mission capabilities.

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