A Microwave Sinter System for Lunar Regolith Studies
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
As the international space station ISS is approaching end of life in the next decade, ESA, like other space agencies around the globe, is doing studies about a successor project. A lunar base is one of the possibilities. Using lunar regolith as a resource would cut down the mass to be transported from earth and hence the cost of a station. One way of using lunar regolith could be additive manufacturing of housings or other infrastructure elements. To do so, microwave heating and sintering is an option. Also for extraction of oxygen or other useful elements, microwave heating would be useful. With computer simulations, different mechanisms acting during microwave heating of regolith are illustrated. Because absorption rates increase with temperature, thermal runaway of hot areas appears. As heat is generated inside the material, whilst energy is lost through surface radiation, temperature gradients and heat distribution inside the material are not trivial. The influences of additives and IR preheating are also studied in this simulations. In order to study microwave heating of regolith in the laboratory, a test bench based on a multimode cavity has been built. It enables experiments in air, vacuum or any desired atmosphere. As the power distribution in a multimode microwave is not uniform, the test bench offers different possibilities to modify the electromagnetic wave pattern and its irradiation direction. Samples can be preheated using an IR radiator. Finally,the heating process is monitored and controlled with an IR camera. Experiments using D-NA-1 regolith simulant show the feasibility of microwave heating. Pure regolith simulant, under certain conditions, already couples well enough to heat up to sintering temperature. In contradiction to findings in earlier research papers, np-Fe has not been identified as a prerequisite for successful heating. Nevertheless, additional ilmenite and IR preheating both enhance the reliability and controllability of the process. Heatingratesof7K/s are obtained with the system, resulting in subsurface sintering and melting of regolith within 2 minutes of microwave application. In air, such quick heating leads to a brittle glass full of embedded gas bubbles. Best results are obtained with a heating rate of 0.1 to 0.15 K/s. Suitable heating rates could presumably be higher in vacuum, as trapped air might be less of a problem. The experiments show that microwave sintering is a feasible approach to 3D-printing in lunar environment. Proper control of the sintering process is vital to obtain useful results.
Place, publisher, year, edition, pages
2016. , 96 p.
Technology, Regolith, Sintering, Microwave, Moon, Habitat, 3D-printing
IdentifiersURN: urn:nbn:se:ltu:diva-59088Local ID: f9cf7e39-fb4c-4a2e-852b-eb6ce42a7404OAI: oai:DiVA.org:ltu-59088DiVA: diva2:1032476
Subject / course
Student thesis, at least 30 credits
Space Engineering, master's level
Validerat; 20150913 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved