The establishment of a permanent lunar base, such as the 16-node Necklace of Selene grid, requires a logistics pipeline capable of monthly mission cadences. Current aerospace architectures fail this requirement due to a focus on either political heritage or extreme reusability that compromises mission-specific physics. To solve this, I propose a 4-stage dual-fuel architecture that merges the high-thrust capability of the Super Heavy booster with the industrial simplicity of the Falcon 9 upper stage philosophy.
A lunar infrastructure rocket must satisfy four primary requirements: high mass fraction, landing stability, thermal reliability, and economic cadence. Current designs fail to meet these simultaneously. The Starship architecture is optimized for Mars and total reusability, which creates a critical refueling bottleneck for the moon. Achieving a single lunar landing requires 10 to 15 tanker launches to mitigate the low energy density and high boil-off rates of liquid methane during the several-hour wait for trans-lunar injection. Furthermore, the 50-meter height of the Starship HLS creates an unacceptable center of gravity risk on the uneven terrain of the lunar south pole. Conversely, the SLS is disqualified by the extreme cost of its expendable hydrogen-based stages and the inherent leakage risks of the smallest molecular fuel.
My design solves these problems by utilizing the Super Heavy as a reusable Stage 1 to clear the atmosphere, while the upper sections consist of three expendable stages utilizing RP-1 and Merlin-derivative engines. RP-1 offers a density of 810 kg/m³, nearly double that of liquid methane. This allows for a shorter and structurally stiffer airframe with lower bending moments. Because RP-1 is stable at room temperature, it eliminates the cryogenic boil-off risks during orbital coasting, ensuring the trans-lunar injection burn is reliable and precise.
In this 3+1 staging model, the Stage 2 orbital insertion vehicle jettisons its 9-meter payload fairing at an altitude of approximately 110 km. This removes 10,000 kg of parasitic mass before LEO insertion is complete. Stage 3 performs the trans-lunar injection burn and is immediately discarded, ensuring the descent stage carries zero unnecessary structural mass into the lunar gravity well. The Stage 4 descent module is a dedicated one-way infrastructure transporter. Since the mission is one-way, we eliminate the need for transposition maneuvers, docking sequences, or ascent stages. Every kilogram of structure is either fuel or permanent infrastructure.
Calculations indicate that this architecture can deliver 48,000 kg of net infrastructure to the lunar surface per launch. With a marginal launch cost of 15 million USD for the reusable booster and 55 million USD for the mass-produced expendable upper stages, the total mission cost is 70 million USD. This results in a delivery cost of 1458 USD per kg.
By shifting high-complexity staged combustion engines to the reusable ground-linked booster and utilizing high-reliability gas-generator engines for the vacuum and landing phases, we eliminate the refueling bottleneck. This transforms the lunar mission from a rare scientific event into a standardized industrial process, providing the throughput necessary for a functional lunar grid.
Development and R&D Strategy
The R&D phase for this architecture follows a parallel development cycle of 24 months, leveraging existing hardware heritage to minimize technical risk and capital expenditure. Unlike the Starship program, which requires iterative testing of complex thermal protection systems and exotic maneuvers, this design focuses on scaling proven structural and propulsion technologies.
Structural Scaling: The development of the 9-meter diameter tanks utilizes the existing tooling and friction-stir welding techniques employed for the Falcon 9, but scaled to the Super Heavy diameter. Using Aluminum-Lithium (Al-Li) alloys for the expendable stages ensures a high strength-to-weight ratio while maintaining low manufacturing costs.
Avionics Mirroring: To eliminate 70% of software R&D cycles, the avionics and Flight Control Systems (FCS) are mirrored from the established Merlin-Vacuum fleet. This standardization ensures that the software governing Stage 2 and Stage 3 is essentially an updated version of the code that has successfully flown hundreds of Falcon 9 missions.
GSE and Infrastructure: Launch pad modifications at LC-39A focus on dual-fuel Ground Support Equipment (GSE). This involves the integration of an RP-1/LOX quick-connect fueling arm to complement the existing CH4/LOX system for the booster.
Economic Scale: Total R&D expenditure is estimated at 600 million to 800 million USD. This covers structural qualification, Stage 4 landing leg integration, and the precision avionics required for autonomous lunar touchdown.
By bypassing the multi-year development of high-energy cryogenic upper stages, this R&D path achieves mission readiness within a 2-year window, directly supporting the immediate deployment of the 16-node lunar grid.
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