Current liquid rocket architectures accept a fundamental compromise: heavy hydrocarbons (RP-1) suffer from coking and high injector pressure losses, while light hydrocarbons (methane) demand extreme turbopump discharge pressures and large tank volumes. This article introduces a unified propulsion paradigm—Pre-Saturated Hydrocarbon Propulsion (PSHP). By pre-saturating subcooled liquid hydrocarbons with dissolved gaseous hydrogen solute at <0.5 wt%, we introduce a multifunctional thermodynamic modifier into the fuel matrix.
Simultaneously acting as an in-situ effervescent atomization agent, a radical soot inhibitor, an autogenous pressurant, and a turbopump work-relief mechanism, this fluid modification is backed by a closed-loop, on-site Non-Oxidative Methane Coupling (NOCM) reforming plant. We assert that this single fluid innovation fundamentally alters the design baselines of both operational RP-1 kerolox engines (e.g., Merlin 1D) and next-generation full-flow staged combustion architectures (e.g., Raptor).
1. The Core Innovation: Multi-Functional Hydrogen Solute
Rather than treating hydrogen as a separate liquid propellant requiring isolated 20 K cryogenic containment, PSHP introduces unbound H₂ as a dissolved solute directly inside the dense liquid hydrocarbon matrix. This leverages four simultaneous mechanisms:
1. In-Situ Effervescent Atomization: Upon passing through the injector orifice, the localized pressure drop causes supersaturated H₂ to violently flash out of solution. Micro-bubbles nucleate and expand inside the liquid jet, shattering primary droplets into sub-15 µm mists via internal explosive force rather than high-shear hydraulic pressure drop.
2. Kinetic Radical Soot Capping: During fuel-rich pyrolysis (in gas generators or preburners), the desorbing H₂ provides an abundance of mobile H radicals. These radicals cap active carbon chain ends, blocking polycyclic aromatic hydrocarbon (PAH) ring growth and completely suppressing solid carbon (soot/coke) formation at the source.
3. Turbopump Work-Relief Loop: In staged-combustion cycles, light H₂ gas mixed into the fuel preburner exhaust lowers the average molecular weight of the turbine working fluid. This increases its gas constant, yielding higher enthalpy output per unit pressure drop across the turbine and lowering required turbopump discharge pressures by over 100 bar.
4. Autogenous Lightweight Pressurization: Off-gassed H₂ from the on-site system serves as an autogenous ullage pressurant gas, eliminating heavy inert helium COPV systems while maintaining high surface partial pressure to lock the solute in solution prior to pumping.
2. On-Site Closed-Loop Synthesis
To make this architecture economically self-sustaining without complex liquid hydrogen supply chains, the launch facility utilizes on-site Non-Oxidative Methane Coupling (NOCM):
The plant ingests standard pipeline methane and outputs pure, high-density Rocket-Grade Propane (C₃H₈) and pure gaseous H₂. A fraction (<0.5 wt%) of the produced H₂ is sparged into the subcooled propane, the secondary fraction provides autogenous tank ullage pressurization, and the surplus is combusted to thermally power the on-site catalytic reactor and subcooling loops.
3. Impact on Modern Rocket Architectures
This single fluid innovation alters the fundamental engineering trade-offs of existing and future launch systems:
Impact A: Retrofit Optimization (Merlin 1D / Falcon 9)
Applying ground-sparged H₂ to densified RP-1 eliminates turbopump turbine coking in the fuel-rich gas generator circuit and stops regenerative cooling channel coking. Simultaneously, replacing hydraulic shear atomization with effervescent flashing recovers 15 - 20 bar of wasted injector ΔP, allowing higher chamber pressures or lower turbopump strain while enabling rapid, zero-flushing engine reusability.
Impact B: Complete Re-Architecture (Raptor / Starship)
Replacing Liquid Methane (LNG) with H₂-saturated Pure Propane subcooled to 90 K:
- Increases bulk fuel density by +38% (~ 600 kg/m³), shrinking fuel tank volume and shifting the vehicle Center of Mass forward for re-entry stability.
- Matches Liquid Oxygen temperature at 90 K, achieving a zero-ΔT common bulkhead that eliminates boil-off and complex double-wall insulation.
- Relieves Raptor's extreme methane turbopump discharge requirement from ~ 550 bar down to ~ 420 bar, widening operating margins and drastically extending powerhead lifespan.
Conclusion & Novelty Claim
While effervescent atomization and gas-phase hydrogen injection have been studied as isolated laboratory phenomena, no prior architecture in aerospace propulsion has proposed combining on-site methane-to-propane reforming with pre-saturated H₂-dissolved hydrocarbon fuels to simultaneously serve as a micro-atomizer, a soot inhibitor, an autogenous pressurant, and a turbopump work-relief agent. This framework bridges the gap between high-density kerolox and clean-burning methalox, establishing a third, superior class of hydrocarbon propulsion.
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