Economy of lunar rocket fuel: analysis model

Economic Model for Producing Rocket Fuel from Lunar Resources

This model evaluates the long-term cost of producing rocket fuel from lunar water ice to compare it with Earth-based fuel. Key factors are the cost transfer ratio for transporting capital equipment (G) and the production mass coefficient (𝜙 = product mass / equipment mass). These parameters determine when lunar fuel becomes cheaper than delivering it from Earth to orbits like LEO, GEO, or Lagrange points.

Tent sublimation technology achieves 𝜙 > 100, exceeding the profitability threshold even for LEO. Open-pit mining is closer to the threshold, but improvements and operational experience will make it competitive.

Key Model Notation

| Symbol | Definition |

|--------|-------------|

| C_fin | Financing cost |

| C_K | Capital development and manufacturing costs |

| C_ops | Operational expenses over lifespan |

| c_R | Reliability cost coefficient |

| C_tr | Cost of transporting capital to the Moon |

| c_X | Cost of 1 kg of lunar fuel at point X |

| G | Cost transfer ratio for lunar capital |

| 𝜙 | Production mass coefficient |

| ψ_X | Ratio of lunar to Earth fuel cost at X |

Additional: Δv_{Y-X} — characteristic velocity from Y to X; IMF — inert mass fraction; I_sp — specific impulse.

Orbits: LEO (160–2000 km), GEO (35,786 km), GTO (geostationary transfer orbit), LS (lunar surface), EML1 (Earth-Moon Lagrange point 1), DRO (distant retrograde orbit around the Moon).

Analysis of Previous TEA

Previous techno-economic analyses have varied: some predicted profitability, others a negative outcome. Critical errors include:

• Choosing architectures with high G (expensive equipment delivery).
• Ignoring capital with high 𝜙.

For example, Charania and DePascuale noted the high cost of delivery from LS to GEO but overlooked the long-term effects of production scale. Jones et al. estimated ISRU as 97% more expensive than Earth fuel, underestimating the potential of 𝜙.

This model introduces:

• x = normalized per-launch equipment cost.
• τ = specific cost of transporting capital per kg of product.
• χ = normalized capital cost.

Competitiveness condition: ψ_X < 1, where ψ_X = f(𝜙, G, other parameters).

Reliability and Operational Factors

Reliability R influences through c_R = E_R * (1 - R) / R, where E_R is the scale of effort to increase R from R_0 to R_max.

For lunar conditions:

• Low gravity (1/6 g).
• No atmosphere.
• Temperature extremes.

Technologies must account for these factors. Tent sublimation minimizes equipment wear, ensuring high 𝜙.

Calculation for LEO: with L_p = cost of launching fuel from Earth, lunar fuel wins if c_{LEO} < L_p * Γ_{LEO}.

Application in Space Economy

Production on LS for clients in GEO: satellite tugs use fuel for orbit circularization. The scale of consumer markets (e.g., Starlink-like constellations) drives demand.

• ISRU Advantages: Reduced Δv for missions; scalability akin to Earth.
• Risks: Initial capital investments; achieving R > 0.9.

The model predicts cost reductions for all space tasks due to cheaper fuel.

Key Takeaways

• Cost transfer ratio G and coefficient 𝜙 determine profitability: target G < 10, 𝜙 > 50 for LEO.
• Tent sublimation technology is already competitive; open-pit mining will be after optimization.
• Reliability R critically affects c_R; requires E_R ~ 10–100 for lunar conditions.
• ISRU reduces costs for GEO, EML1, DRO tasks.
• Long-term effect: accelerated space exploration through scale.

— Editorial Team