constants.json

{
  "cea": {
    "plot_colors": [
      "#0b7285",
      "#c92a2a",
      "#5f3dc4",
      "#2b8a3e",
      "#e67700",
      "#495057",
      "#1c7ed6",
      "#d6336c",
      "#5c940d",
      "#9c36b5"
    ]
  },
  "blowdown": {
    "physics": {
      "g0_mps2": 9.80665,
      "nitrous_oxide_fluid": "NitrousOxide",
      "n2o_temperature_limits_k": {
        "min": 184.0,
        "max": 309.0
      }
    },
    "seed_case": {
      "highest_isp": "highest_isp"
    },
    "ui_modes": {
      "basic": "basic",
      "advanced": "advanced"
    },
    "injector_delta_p_modes": {
      "explicit": "explicit",
      "fraction_of_pc": "fraction_of_pc"
    },
    "regression_presets": {
      "custom": {
        "key": "custom",
        "label": "Custom",
        "a_reg_si": null,
        "n_reg": null
      },
      "project_default_paraffin_abs": {
        "key": "project_default_paraffin_abs",
        "label": "Paraffin + ABS baseline (Project Default)",
        "a_reg_si": 5.0e-05,
        "n_reg": 0.5
      }
    },
    "injector_pressure_drop_policies": {
      "low": {
        "key": "low",
        "label": "Low (Project Default 0.15 Pc)",
        "delta_p_fraction_of_pc": 0.15
      },
      "nominal": {
        "key": "nominal",
        "label": "Nominal (Project Default 0.20 Pc)",
        "delta_p_fraction_of_pc": 0.2
      },
      "conservative": {
        "key": "conservative",
        "label": "Conservative (Project Default 0.30 Pc)",
        "delta_p_fraction_of_pc": 0.3
      }
    },
    "stop_reason_labels": {
      "burn_time_reached": "Burn time reached.",
      "tank_quality_limit_exceeded": "Tank quality limit exceeded; vapor ingestion is likely.",
      "port_radius_reached_outer_radius": "Port radius reached the configured outer radius.",
      "tank_depleted": "Tank mass reached zero.",
      "usable_oxidizer_reserve_reached": "Configured oxidizer reserve was reached.",
      "tank_left_two_phase_region": "Tank left the supported saturated two-phase N2O model."
    },
    "estimation_basis_notes": [
      "Derived Tank Basis: Derived from burn time + O/F + Isp + oxidizer temperature + fill policy.",
      "Derived Grain Basis: Derived from target initial Gox, regression preset/default, and project-default port-count policy unless advanced mode is active.",
      "Derived Injector Basis: Derived from oxidizer flow, liquid density, a project-default Cd/hole-count, and the selected injector pressure-drop policy unless advanced mode is active."
    ],
    "model_assumptions": [
      "The highest-Isp converged CEA case is used as a single steady design seed for the transient 0D blowdown run.",
      "Tank thermodynamics assume a rigid, adiabatic, saturated two-phase nitrous tank in equilibrium.",
      "The tank model assumes liquid draw only and stops once vapor quality reaches the configured cutoff.",
      "Nitrous properties are taken from CoolProp saturation states within the hardcoded 184 K to 309 K search range.",
      "In basic mode, oxidizer tank temperature is a primary user input; saturated nitrous pressure and liquid density are taken directly from the existing CoolProp saturation helper at that temperature.",
      "In basic mode, usable oxidizer fraction is treated as a project default unless advanced mode is active.",
      "Feed losses follow an explicit configured source path: hydraulic lumped-K model with optional calibrated multiplier, or a manual override if selected.",
      "Injector flow uses an incompressible single-phase orifice equation with fixed Cd and no flashing or two-phase correction.",
      "In basic mode, injector discharge coefficient, hole count, and pressure-drop policy are treated as project defaults unless advanced mode is active.",
      "Injector total area is first estimated from oxidizer flow, liquid density, Cd, and either an explicit injector delta-p or a chosen fraction of chamber pressure.",
      "Fuel blend density is estimated from the seeded CEA ABS volume fraction and the configured ABS/paraffin material densities.",
      "In basic mode, the regression law coefficients and port count come from a project preset/default unless advanced mode is active.",
      "Grain regression uses a fixed empirical law rdot = a * Gox^n with constant user-provided coefficients.",
      "Initial port radius is estimated from the target initial oxidizer flux and the seeded oxidizer design flow.",
      "Fuel usable fraction is treated as a project default in basic mode unless advanced mode is active.",
      "Grain length is estimated from target fuel mass flow, blend density, initial port diameter, and the initial regression rate.",
      "Outer grain radius is estimated from loaded fuel mass, blend density, initial port radius, and grain length.",
      "Port growth is treated uniformly across all ports with no axial, circumferential, or erosive-burning nonuniformity model.",
      "Chamber pressure is inferred from mdot_total * c* / At using the CEA-sized throat area and a transient c* estimate.",
      "Transient thrust uses a unified nozzle-performance bookkeeping model with explicit vacuum and actual thrust definitions.",
      "A lightweight cached CEA lookup is used to vary c* with O/F and vary Cf with chamber pressure and ambient pressure through the nozzle bookkeeping layer.",
      "No finite-rate chemistry, combustion-efficiency correction, heat-transfer model, structural response, or injector transient is resolved.",
      "The result is a preliminary 0D system model intended for first-pass sizing trends, not a high-fidelity flight prediction."
    ]
  }
}