Investigation of friction stir welding for lunar applications

Abstract

Novel aerospace technology research has been driven by increased interest in governmental and privatized space travel efforts. One such technology is friction stir welding (FSW), often promoted as a capable in-space manufacturing process. FSW literature currently has gaps regarding its operation in lunar conditions. As an initial approximation, this study simulated lunar cooling heat fluxes via a controlled furnace. Regulating the heating and cooling of AA6061-T6 allowed an evaluation of material property changes caused by the lunar cooling rate. Sample analysis utilizing energy dispersive spectroscopy (EDS) showed silicon, magnesium, and iron precipitate growth in the friction stir welds due to simulated lunar cooling. Mechanical testing of the samples showed a minor strength decrease of 6.8% from the ambient condition weld to the simulated lunar cooling weld. The associated in-process torque variations created by heat accumulation suggest reduced energy requirements for FSW compared to terrestrial operation. While a strength decrease was observed, it is minor. The strength and the reduction of in-situ power consumption supports FSW as a valid lunar technology and warrants future work on this subject.