LUNAR REGOLITH CEMENT MIXER

PUBLICATION

Lunar Regolith Cement Mixer (LRCM): A Governed ISRU Construction-Material Processor for Lunar and Martian Surface Operations

AEMS-LRCM-001 v13.0  |  SPACE SYSTEMS  |  2026

ABSTRACT

Permanent habitation of the lunar and Martian surfaces requires construction material produced in situ. Importing Portland cement from Earth to the lunar surface costs on the order of USD 1 million per kilogram under NASA's Commercial Lunar Payload Services program [17], economically prohibitive for any structure beyond a small demonstration slab. This paper presents the Lunar Regolith Cement Mixer (LRCM), a governed ISRU processing vessel that converts raw regolith into structural binder through four selectable cement pathways: sulfur concrete, alkali-activated geopolymer, water-ice cementation, and microwave sintering. Of these, sulfur concrete is identified as the primary zero-import pathway for lunar operations: elemental sulfur exists in lunar regolith as sulfides and in pyroclastic deposits, can be thermally extracted on-site, melts at 115°C, sets by cooling rather than hydration, and requires no imported bulk binder or aggregate chemicals (a trace phase-transition modifier remains an imported consumable pending in-situ production).

The LRCM repurposes the Governed Electromagnetic Mixing and Batching Chamber (GEMBC) thermal-gradient capture vessel from the CSMMC plasma methane-cracking and graphene-production architecture. The GEMBC's 316L stainless steel shell provides the abrasion tolerance, thermal envelope, and dimensional stability required for regolith processing in vacuum. Internal graphene capture coupons are replaced with mixing baffles and paddles; the vertical flow-path and residence-time control logic map directly to mixing time and curing preparation. A modular cartridge system allows pathway switching by swapping the internal cartridge assembly. Mechanical mixing is provided by a ferrofluidic or magnetic-coupled rotary feedthrough. A double-valve airlock enables regolith feed and product discharge without pressurising the processing volume. The architecture supports surface applications (foundation plinths, equipment pads, antenna-farm anchors) and subsurface construction (tunnel and cavern liners via TBM integration). Power is supplied through the GESH three-tier architecture and all process parameters are governed under DIGSP protocol.

KEYWORDS

SECTION 5.1a — SULFUR FEEDSTOCK: EXTRACTION MASS BALANCE

The sulfur-concrete pathway requires 30–35% elemental sulfur by mass as binder. This sulfur must be extracted from raw regolith upstream of the LRCM using a dedicated extraction furnace operating at 600–800°C. Mare basalt regolith contains 0.06–0.26 wt% total sulfur, predominantly as troilite (FeS), with elevated concentrations in pyroclastic glass deposits (up to 0.3–0.5 wt% in Apollo 17 orange-glass samples). Laboratory thermal extraction at 600–800°C achieves 50–70% sulfur recovery. The extraction ratio ranges from approximately 476:1 for pyroclastic feedstock to 2,500:1 for low-sulfur mare basalt.

The baseline calculation assumes a 50-litre batch (~105 kg sulfur concrete at 2,100 kg/m³) requiring 31.5 kg of elemental sulfur at 30% binder fraction. Even at the most favourable feedstock (pyroclastic, 0.30 wt% S, 70% extraction), each LRCM batch requires processing approximately 15 tonnes of raw regolith through the extraction furnace. The thermal energy demand at a baseline throughput of 100 kg/h is 6.4–12.8 kW continuous — the dominant energy consumer in the sulfur-concrete pathway; the LRCM mixer itself (0.5–1.0 kW) is a minor contributor by comparison.

Three architectural responses address this imbalance: (1) the extraction furnace operates as a continuous slow-rate stockpiling system, decoupling extraction rate from mixing rate; (2) site selection targeting pyroclastic deposits reduces the extraction ratio by a factor of 3–5; (3) counter-flow heat exchange can reduce net thermal input by 40–60%. Critically, the sulfur-depleted spent regolith is not a waste product — it is pre-heated, de-sulfured aggregate feedstock for the sulfur-concrete mix itself, closing the material loop.

SECTION 10 — SETTING AND CURING IN VACUUM AND REDUCED GRAVITY

Setting and curing behaviour on the lunar and Martian surfaces differs fundamentally from terrestrial concrete. Each LRCM pathway uses a distinct setting mechanism governed by thermal control, sealed-volume management, and reduced-gravity flow dynamics.

10.1 Sulfur Concrete: Thermal Solidification. Sulfur concrete sets by cooling below approximately 115°C. In vacuum, radiative cooling is extremely efficient and ungoverned sulfur mixtures will set too quickly. The LRCM prevents premature solidification through three provisions: vessel heater bands maintain mixture at 130–140°C throughout mixing; discharge occurs into moulds preheated to 120–130°C; DIGSP governs the cool-down rate to avoid thermal shock. The thermal balance at discharge is critical — if the receiving structure acts as a cold sink, the sulfur mixture will freeze peripherally on contact, producing a void-rich plane of weakness. All downstream formwork is preheated and discharge rate is governed to match the thermal capacity of the receiving surface.

The organic modifiers (DCPD and stearic acid) used to suppress the 95.5°C phase transition have not been fully characterised for long-term stability under sustained lunar vacuum and unshielded solar UV. Progressive modifier depletion from surface layers could re-expose those layers to phase-transition damage. Structural sulfur-concrete elements are designed to be buried under regolith overburden, limiting UV exposure and diurnal temperature swing amplitude. Phase 1 testing must include accelerated outgassing characterisation under simulated lunar thermal cycling.

10.1a Sulfur Vapor Containment: Post-Cure Sealing. A post-cure sealing step applies a thin aluminosilicate film drawn from the same alkali-activated precursor chemistry used in Cartridge B, preserving the zero-import requirement of the sulfur pathway. The seal closes the vapor escape path to vacuum. Because the coating's thermal expansion behaviour is not yet characterised against sulfur concrete's high expansion range, sublimation suppression from sealing should be treated as an unvalidated design provision pending Phase 1 vacuum-chamber mass-loss testing.

10.2 Geopolymer: Sealed-Volume Chemical Curing. Geopolymer binders cure through alkali-activated aluminosilicate polymerisation, requiring time, temperature control, and retention of activator water. Open-vacuum curing is impossible. The LRCM cures geopolymer in sealed moulds or a dedicated curing chamber maintained at 60–90°C under mild CO₂ or N₂ overpressure (0.5–2 bar). DIGSP monitors temperature, pressure, and internal humidity to ensure complete polymerisation before vacuum exposure.

10.3 Water-Ice Cement: Freeze-Bonding. Water-ice cement sets by freezing, forming ice bridges between regolith grains. In vacuum, water sublimates rapidly unless temperature is kept below −20°C. Cartridge C maintains controlled sub-zero temperatures during mixing. Product is discharged only into permanently shadowed or thermally protected regions.

10.4 Sintered Regolith: Thermal Fusion and Cool-Down. Sintered regolith contains no binder; setting is cooling after fusion at 800–1,100°C. DIGSP controls the cool-down rate to avoid thermal shock. Vacuum simplifies cooling: no convective losses, only radiative and conductive pathways. Sintered regolith is the most environment-agnostic product.

10.5 Premature Setting: Failure Mode and Mitigation. Premature setting is critical for sulfur and water-ice pathways. Sulfur sets if temperature drops below melting point during mixing or placement (mitigated by heater bands, preheated moulds, governed cool-down). Water-ice freezes on contact with cold surfaces (mitigated by cryogenic cartridge control, insulated discharge path). Geopolymer activator water flashes off in vacuum (mitigated by sealed curing chamber with overpressure). Sintering has no premature-set mode; only thermal-shock risk (mitigated by DIGSP-governed cooling).

THE CONSTRUCTION-MATERIAL PROBLEM

Every proposed lunar or Martian base architecture published since the 1990s assumes the availability of local construction material, yet no flight-qualified hardware exists to produce it. The problem is not the absence of candidate binder chemistries — sulfur concrete, alkali-activated geopolymer, sintered regolith block, and water-ice cementation have all been demonstrated at laboratory scale. The problem is the absence of a processing vessel that can handle raw regolith in the operational environment. Conventional concrete mixers rely on three conditions absent from the lunar surface: atmospheric pressure to suppress dust, terrestrial gravity to drive material flow, and water as mixing and hydration medium.

The LRCM solves this by repurposing the GEMBC — a vessel already proven for sustained high-temperature particulate processing under governed electromagnetic fields in a sealed environment. Every requirement of a regolith cement mixer is a subset of the requirements the GEMBC already meets. The LRCM is not a new vessel: it is a re-cartridged GEMBC with a mechanical drive and regolith-rated seals.