Why TBMs Are Not Feasible for the Moon in the Next Few Decades

Why TBMs Won’t Build the Moon

On Earth, tunnel boring machines justify their billions because projects demand millions of cubic meters of excavation, powered by multi-megawatt grids and supported by thousands of workers. On the Moon, none of that exists. Early Artemis bases will need a few hundred cubic meters at most.

A TBM weighs hundreds of tonnes; lunar landers can deliver tens. A TBM consumes 3–10 megawatts continuously; lunar power plants will produce tens of kilowatts. On Earth, TBMs only pay off above one million cubic meters. On the Moon, demand is two orders of magnitude smaller. The return is negative by design.

The Moon will not be bored by megaproject machines. It will be built with regolith bags, berms, adapted lava tubes, and small modular excavators, tools that fit the scale and the business case. TBMs may one day carve out lunar cities, but not before 2050. Until then, they are the wrong tool for the wrong stage.

Contractors, investors, and mission planners should stop chasing TBM fantasies and start backing modular excavation systems. That’s where the real ROI is.

Some will argue that research into lighter TBMs or micro-TBMs changes the equation. It does not. Weight is only one of the barriers, and even if mass is cut, the power demand, maintenance impracticalities, and ROI collapse remain. A lighter TBM is still a stranded asset on the Moon.

TBM vs Lunar Reality — A direct comparison of scale mismatches.

Even the smallest TBMs weigh hundreds of tonnes, while lunar landers can deliver tens at most. TBMs draw megawatts of continuous power; lunar surface systems will supply kilowatts. On Earth, TBMs only become economical above one million cubic meters; early lunar bases will require a few hundred. These three metrics alone, mass, power, and ROI threshold, show why TBMs are the wrong tool for the Moon’s first generation of construction.

Mass and Transport

The first and most decisive barrier to deploying tunnel boring machines on the Moon is their mass. On Earth, even the smallest TBMs used for urban tunnels weigh in the range of 250 to 400 tonnes. Medium-diameter machines quickly climb toward 1,000 tonnes once you include the cutterhead, main drive, backup gantries, conveyors, and support systems. These are not laboratory prototypes; they are industrial systems that demand massive transport and staging operations even under the best terrestrial conditions.

By contrast, the lunar transportation system of the coming decades will operate on an entirely different scale. The most advanced cargo landers under development are designed to place payloads of only a few tons to a few tens of tons onto the lunar surface. Blue Moon, for example, is sized for around 3.5 tonnes. Starship in its lunar configuration, if it achieves its optimistic targets, may deliver up to 100 tonnes. Even in that best-case scenario, there remains at least an order-of-magnitude gap between what a TBM requires and what can realistically be landed.

The mismatch is not incremental; it is structural. A TBM cannot simply be scaled down to meet a 30-tonne delivery constraint. Its mass is inherent to the physics of the machine: the cutterhead diameter, thrust cylinders, torque drives, support decks, and spoil handling systems all scale in the hundreds of tonnes. Attempting to disassemble a TBM into modules for launch would create its own dead end. The number of flights, the precision robotics required for reassembly, and the months of crew effort needed would dwarf the capabilities of early lunar bases.

In business terms, the logistics alone kill the idea before it starts. Even if one were to imagine the funding of a TBM shipment to the Moon, the opportunity cost is unacceptable. The same launch capacity could deliver dozens of smaller, modular machines and prefabricated surface systems, equipment that can actually be assembled, operated, and maintained in the resource-starved environment of the Moon.

TBMs vs lunar lander payload limits. Even the smallest TBMs weigh between 250 and 400 tonnes, with medium-diameter machines climbing toward 1,000 tonnes. By contrast, the next-generation lunar landers will deliver only 3 to 30 tonnes to the surface, with optimistic projections of 100 tonnes. The gap is two orders of magnitude, making disassembly and reassembly of a TBM on the Moon logistically impossible.

Power Demand

The second barrier, as decisive as mass, is energy. Tunnel boring machines are continuous consumers of power. Even compact TBMs designed for urban work require between 3 and 10 megawatts, depending on diameter and geology. Medium and large machines can easily exceed those values. This energy is not occasional peak draw; it is continuous demand during excavation.

On Earth, this is trivial. TBMs plug into urban grids or dedicated substations that deliver hundreds of megawatts without interruption. On the Moon, there is no such grid. Power must be generated locally, stored, and distributed through systems that have yet to be demonstrated at scale.

The reality for the 2020s and 2030s is kilowatt-scale surface power. Small solar farms and early nuclear demonstrators are targeting 10 to 40 kilowatts. Even if every watt is dedicated to excavation, this is two to three orders of magnitude short of what a TBM requires. The gap is not a matter of incremental improvement. It is structural and unbridgeable in the foreseeable horizon.

No contractor or mission planner is going to build a megawatt-scale power plant on the Moon simply to operate a TBM that produces a few hundred cubic meters of tunnel. The economics collapse before the first cutterhead turns. Until lunar industry can sustain reactors in the multi-megawatt range, TBMs are not even on the table.

TBM demand vs projected lunar supply. Even compact TBMs require 3–10 megawatts of continuous power. Lunar surface systems in the 2020s and 2030s will deliver only tens of kilowatts. The gap is two to three orders of magnitude, making TBMs economically and logistically impossible to operate in the near term.

Economics and Scale

The economics of tunnel boring are decisive. On Earth, the cost of constructing a tunnel with a TBM typically falls in the range of $10,000 to $50,000 per meter, depending on ground conditions, machine type, and logistics. These values are drawn from major infrastructure projects such as the Gotthard Base Tunnel in Switzerland and the Channel Tunnel between the U.K. and France, both multi-billion-dollar undertakings with excavation volumes in the tens of millions of cubic meters.

The logic behind these investments is simple: the fixed costs of TBMs, procurement, transport, assembly, backup systems, and maintenance, are enormous. They only make sense when spread across extremely large volumes of excavation. Once a machine is in the ground, every additional meter advances the return.

On the Moon, the situation is reversed. Early Artemis bases and commercial outposts will require hundreds to perhaps one thousand cubic meters of protective or habitable volume. At that scale, the fixed costs of a TBM cannot be absorbed. The machine would remain an idle asset, producing tunnels at a cost so high that no contractor or agency could defend the investment.

By comparison, modular excavation equipment, regolith bag systems, and lava tube adaptations scale efficiently at low volumes. They deliver immediate returns for outposts without tying up billions of dollars in hardware that cannot earn back its cost. TBMs only make sense when lunar settlements reach city scale, with excavation demands above one million cubic meters. Until then, every dollar spent on them is wasted.

Operational Reality

The day-to-day operation of tunnel boring machines assumes a set of conditions that do not exist on the Moon. TBMs rely on pressurized fluids, slurry or compressed air, to cool the cutterhead, remove spoil, and stabilize the tunnel face. These systems demand thousands of cubic meters of water and additives. On the Moon, there is no groundwater to draw from and no atmosphere to use. Every liter of fluid would have to be imported or manufactured, making slurry or compressed air solutions impossible.

Cutterhead wear is another limiting factor. On Earth, disc cutters must be replaced after a few hundred meters in abrasive ground. Access chambers, hyperbaric interventions, and specialized crews make this routine. On the Moon, cutterhead tools would grind against regolith that is sharper, more angular, and more glass-rich than most terrestrial materials. Tool changes in a vacuum, with suited crews or remote robotics, would be impractical. Once a TBM stalls, it becomes a stranded asset, immovable and unserviceable.

TBMs also assume predictable geology. Their economics depend on advancing steadily through consistent ground. Lunar subsurface conditions are the opposite: loose fines near the surface, compacted regolith at depth, sudden boulders, voids, and fractured megaregolith layers. A single unexpected cavity or block can jam or destroy a machine that has no flexibility to adapt.

By contrast, alternatives scale to lunar conditions. Modular drilling rigs and small roadheader-style excavators can be broken down for delivery, assembled with limited infrastructure, and serviced in the field. Microwave or laser-assisted methods weaken regolith walls without relying on mechanical force, reducing tool wear and energy needs. Regolith bag systems and lava tube adaptations avoid subsurface excavation altogether, transforming the environment rather than fighting against it.

The difference is not marginal. TBMs are designed for the uniformity of Earth’s megaprojects; lunar conditions demand adaptability. In practical terms, the Moon will reward systems that can be maintained, powered, and scaled incrementally, and penalize those, like TBMs, that collapse when their assumptions fail.

A Timeline That Fits Reality

Lunar excavation will not advance through one sudden leap to megamachines. It will follow the same incremental pattern that defines terrestrial construction history: starting with rudimentary but effective methods, then progressing toward mechanization as scale, logistics, and power allow.

The next fifteen years will not be about boring tunnels but about site reconnaissance, resource mapping, and small-scale trials. From 2025 to 2040, lunar engineering will focus on understanding subsurface conditions, testing regolith handling systems, and evaluating natural cavities such as lava tubes and skylight pits. Berms and regolith bags may be used in demonstration projects, but not yet at settlement scale. This period is best understood as the development gap, where concepts are proven before mechanized excavation is attempted.

2040–2050: Modular Mechanization

The first real step into controlled excavation will begin once logistics and surface infrastructure expand. Compact roadheader-style excavators, modular drilling rigs, and thermal-assist methods (microwave or laser) can then be introduced. These systems are compatible with payload deliveries in the tens of tonnes and power in the hundreds of kilowatts, making them feasible for mid-century lunar bases.

Post-2050: Heavy Industrialization

TBMs enter consideration only after 2050, when mission architecture allows cargo deliveries above 1,000 tonnes and nuclear reactors in the multi-megawatt class are available. At that scale, lunar cities requiring millions of cubic meters of excavation would justify the fixed and operating costs of TBMs. Before that horizon, TBMs remain structurally mismatched to demand, logistics, and economics.

Development phase (green, 2025–2040) dedicated to reconnaissance, lava tube assessment, berms, and regolith bags. Modular mechanization (blue, 2040–2050) introduces compact roadheaders, drilling rigs, and thermal-assist systems. Heavy industrialization (orange, post-2050) may finally justify TBMs, dependent on >1,000 tonnes logistics and multi-megawatt nuclear power.

Micro TBMs (MTBMs): Still the Wrong Fit

One could argue that instead of sending a full-scale tunnel boring machine to the Moon, a micro-TBM (MTBM) could be a solution. These are smaller machines, typically used on Earth for utility tunneling, diameters from 0.6 to 3 meters, and weights in the range of tens of tonnes instead of hundreds. On paper, their smaller footprint seems closer to the payload limits of near-term lunar landers.

But the same structural barriers remain:

1. Logistics: Even the smallest MTBMs weigh 10–30 tonnes with support systems. That is the upper edge of projected lunar lander capacity, leaving no margin for assembly equipment, power systems, or spares.

2. Power: An MTBM still requires 500 kW or more for continuous excavation, an order of magnitude beyond the kilowatt-class reactors and solar arrays available in the 2025–2040 horizon.

3. Operation: MTBMs still depend on slurry or compressed air for mucking and face stabilization. Those systems cannot function in vacuum or with lunar regolith, which has no water content or natural pressure boundary.

4. Maintenance: Cutterhead access, tool change, and intervention chambers are infeasible in lunar vacuum conditions. A stuck MTBM is as much a stranded asset as a full-scale TBM.

5. ROI: On Earth, MTBMs pay off when utility tunnels stretch for kilometers. On the Moon, early demand is in the hundreds of cubic meters, a scale where modular excavation and regolith bag systems remain cheaper and more effective.

The conclusion is the same: scaling a TBM down into a micro-TBM does not solve the mismatch. The economics, power, and operational realities still kill the idea.

The Return of Investment is the Decisive Test

On Earth, TBMs earn their place because megaprojects demand millions of cubic meters of excavation. Their massive procurement and operational costs are diluted across decades of tunneling, and they deliver a return because scale justifies them.

On the Moon, scale works against them. Early Artemis infrastructure will need less than 1,000 m³. At that volume, the fixed costs of a TBM, billions in procurement, hundreds of tonnes in logistics, megawatts of unavailable power, cannot be absorbed. The cost per cubic meter would be astronomical, measured in millions of dollars. That is not engineering; that is financial malpractice.

Return on investment is the decisive test:

• Fixed Costs: Even a stripped-down TBM, once transported to the lunar surface, exceeds the total construction budget of an Artemis base.

• Variable Costs: Tool replacement, power demand, and cooling systems all require consumables that cannot be supplied at today’s launch costs.

• Scale Threshold: TBMs only become competitive above 1,000,000 m³ of excavation, two to three orders of magnitude beyond Artemis-scale demand.

• Opportunity Cost: Every tonne of launch capacity allocated to a TBM is a tonne not used for modular rigs, power systems, or habitats, assets that deliver immediate returns.

• Horizon: Only after 2050, with multi-megawatt reactors and logistics capacity above 1,000 tonnes, will TBMs begin to offer a viable ROI.

This is not a question of imagination or technical optimism. It is a question of return. Until lunar demand scales into millions of cubic meters, TBMs are not merely premature; they are financially indefensible.

At SpaceGeotech, we call this plainly: lunar excavation in the next decades belongs to modular, maintainable, incremental systems. The money, the engineering hours, and the investor confidence must flow there, not into fantasies of megamachines that collapse under their own economics.

Author: Roberto de Moraes

Sources & Notes

1. TBM mass and power: Manufacturer specifications (Herrenknecht, Robbins) and ITA technical reports.

2. Lunar payload capacity: Public data from NASA and Blue Origin on lander capacities; Starship HLS concept notes.

3. Power supply: NASA Kilopower heritage reactors and Fission Surface Power program goals (40 kWe class).

4. Regolith properties: Apollo-era soil mechanics studies and JSC data on angularity, cohesion, and abrasiveness.

5. Economics: Terrestrial tunneling costs from large-scale infrastructure projects (e.g. Gotthard Base Tunnel, Channel Tunnel).