Cross-consistency of system and characteristic-field models in a coupled liquid-rocket simulation (Merlin 1D–class case study)

Abstract

Abstract: Coupled liquid-rocket system models and multidimensional nozzle solvers are usually developed separately; when they are made to share a chamber state, the mass-flow consistency between them is easy to leave unmeasured. We describe a transient LOX/RP-1 open-cycle gas-generator engine architecture - capacitance-inertance liquid feed networks, a compressible gas-flow network, shaft dynamics, multi-layer regenerative wall response, offline equilibrium thermochemistry tables, and orifice injector hydraulics - coupled at analysis stop to an axisymmetric method-of-characteristics (MOC) nozzle field evaluated at the shared chamber stagnation state. A headless extraction harness regenerates all tabulated results from frozen inputs and grades two mass residuals: conservation through the marched nozzle field, and agreement between field and system mass flow. On the frozen case, field mass conservation closes to +0.92%, the field-system mass-flow residual is -1.79%, sea-level field thrust is ~830 kN, and engine specific impulse on total propellant flow (~305 kg/s) is 277.5 s, consistent with the public Merlin-class bands that guided case authoring. The result is a documented, reproducible open-cycle composition in which system-field consistency is measured rather than assumed; the case study is a representative reconstruction, and all artefacts are archived here. Manuscript Metadata: Primary Solver Codebase: LorenLib (system model + geometry/MOC) Interactive Authoring Front-End: Meco Rocket Simulator (Open Space Launch Ltd. / mecorocketsimulator.com) Primary Manuscript Venue: engrXiv Key Deliverables & Contributions: Coupled transient open-cycle GG system architecture with post-stop axisymmetric MOC field and reproducible extraction workflow. Extractable consistency metrics (r_conservation, r_network) for system-field mass bookkeeping. Merlin-class case study with frozen inputs and an explicit structural split between baseline system elements and author-selected continuous parameters. Claim discipline separating headline unreconciled field thrust from density-linear mass diagnostics. Software & Reproducibility Notice: Quantitative tables in this manuscript were regenerated using headless LorenLib extracts on the frozen fixture. Interactive authoring used Meco Rocket Simulator (commercial); reproducing the quantitative tables in this manuscript does not require purchasing Meco. The full dataset archive (input deck JSON, extraction scripts, and software snapshot) will be linked as a supplementary dataset record upon dataset publication.