Aluminum-nickel combustion for joining lunar regolith ceramic tiles

Combustion-based methods are attractive for space manufacturing because the use of chemical energy stored in reactants dramatically decreases the required external energy input. Recently, a sintering technique has been developed for converting lunar/Martian regolith into ceramic tiles, but it is unclear how to build a reliable launch/landing pad from these tiles with small amounts of energy and materials. Here we explored the feasibility of joining the regolith tiles using self-propagating high-temperature reactions between two metal powders. Combustion of an aluminum/nickel mixture placed in a gap between two tiles, made of JSC-1A lunar regolith simulant, was studied in an argon environment at 1 kPa pressure. Stable propagation of the combustion front was observed over the tested range of distances between the tiles, 2-8 mm. The front velocity increases with increasing the distance between the tiles. Joining of the tiles was achieved in several experiments and improvement with increasing the tile thickness was observed. Thermophysical properties of the tiles, the reactive mixture, and the reaction product were determined using differential scanning calorimetry and laser flash analysis. A model for steady propagation of the combustion wave over a condensed substance layer placed between two inert media was applied for analysis of the investigated system. Testing the model has resulted in reasonable agreement between the experimental and modeling dependencies. Both experimental and modeling results indicate a narrow quenching distance in the investigated system, which implies that a small amount of the reactive mixture would be required for sintering regolith tiles on the Moon.