Lower Cost Lunar Bricks: Energetics of Melting and Sintering Lunar Regolith Simulants

Abstract

To determine the range of energy consumption required for the production of construction materials from lunar regolith, we conducted heating experiments on a series of lunar simulants. The compositional end-members are anorthosite, from Stillwater MT, and basaltic JSC-1A simulant, and remelted glasses of each. We then studied the energy required to melt 10 combinations of anorthosite and basalt, with different degrees of crystallinity, using differential scanning calorimetry, heating ∼30 mg of sample at 30°C/min. Enthalpies required to go from 50°C to complete melting are 1775 Jg⁻¹ for JSC-1A and ∼1890 Jg⁻¹ for a 50–50 mixture by weight of JSC-1A and anorthosite. The total enthalpies required to achieve melting are systematically lower for glassier starting materials, for example, 1564 Jg⁻¹ for remelted JSC-1A and 1669 Jg⁻¹ for a 50–50 mixture. Starting materials containing glass undergo crystallization above the glass transition (∼650°C for JSC-1A glass and ∼850°C for anorthosite glass), releasing up to 250 Jg⁻¹ of latent heat. Sintering can produce crystalline samples without needing to heat much above ∼1000°C, and the release of latent heat of crystallization makes this a very energetically efficient approach, with enthalpies required to heat to 1000°C as low as ∼810 Jg⁻¹ (Ag50Jg50). We conclude that bricks could be produced at low energy cost by sintering starting materials with a glassy component, sourced from volcanic or impact melt deposits. The tendency for finer grained lunar regolith to also be more feldspathic and glassy raises the possibility that physical sorting by size can also sort for composition and crystallinity, facilitating brick production in locations where the bulk regolith is less suitable.