{
  "title": "MHD bypass illustrative energy ledger including a separate field-excitation debit",
  "type": "parametric bookkeeping exercise; not a performance prediction",
  "reference_inputs": {
    "mass_flow_kg_s": 10,
    "assumed_available_stream_energy_kJ_kg": 100,
    "generator_extraction_fraction": 0.2,
    "generator_efficiency": 0.6,
    "auxiliary_demand_kW": 20,
    "accelerator_efficiency": 0.6,
    "assumed_field_excitation_power_kW": 15
  },
  "reference_outputs_kW": {
    "power_removed_from_flow": 200,
    "generator_terminal_electric_power": 120,
    "other_auxiliary_demand": 20,
    "field_excitation_demand": 15,
    "power_after_auxiliaries_and_field": 85,
    "accelerator_power_returned_to_flow_kW": 51,
    "net_stream_energy_change": -149,
    "unmet_auxiliary_and_field_demand": 0
  },
  "equations": [
    "P_removed = mass_flow × assumed_available_specific_energy × extraction_fraction",
    "P_electric = generator_efficiency × P_removed",
    "P_to_accelerator = max(0, P_electric − P_other_auxiliary − P_field_excitation)",
    "P_unmet = max(0, P_other_auxiliary + P_field_excitation − P_electric)",
    "P_accelerator_power_returned = accelerator_efficiency × P_to_accelerator",
    "ΔP_stream = −P_removed + P_accelerator_power_returned"
  ],
  "input_ranges": {
    "mass_flow_kg_s": [
      1,
      50
    ],
    "assumed_available_stream_energy_kJ_kg": [
      20,
      300
    ],
    "generator_extraction_fraction": [
      0,
      0.6
    ],
    "generator_efficiency": [
      0,
      0.8
    ],
    "auxiliary_demand_kW": [
      0,
      200
    ],
    "accelerator_efficiency": [
      0,
      0.8
    ],
    "assumed_field_excitation_power_kW": [
      0,
      100
    ]
  },
  "limitations": [
    "The assumed available specific energy is an independent hypothetical input, not the 515.7 kJ/kg kinetic-to-static-enthalpy change from the separate ideal inlet model.",
    "Efficiencies, extraction fractions and auxiliary demand are user-selected teaching assumptions, not measured values or evidence that a particular MHD system can attain them.",
    "No conductivity, ionization chemistry, electrode/sheath behavior, magnetic-field supply, magnet mass, thermal management, shock structure, total-pressure loss, combustor/nozzle matching, inlet drag or vehicle-level mass balance is modeled.",
    "The stream-energy account does not calculate momentum flux, pressure thrust, net thrust, specific impulse, net efficiency or vehicle benefit.",
    "A positive generator terminal output is not a positive whole-engine energy balance. The chosen example necessarily leaves stream energy lower after conversion losses, auxiliary loads and the finite-efficiency accelerator.",
    "When generated electricity is below the selected auxiliary demand, the unmet auxiliary requirement is reported and is not assumed to be supplied by the stream.",
    "Self-excitation is an electrical architecture in some MHD systems, not free energy. The slider treats field-system draw as a simple average power debit and does not model startup residual flux, capacitor dynamics, field growth, reactive power, or coupling/stability criteria.",
    "MHD self-excitation reports cited here concern specific machine contexts; liquid-metal generators and pulse-detonation experiments are not direct validation of an airbreathing hypersonic inlet-bypass engine.",
    "The public HVEPS output figures have distinct evidence boundaries. The full AFRL preprint ADA471429 Table VI reports 6.52 kW load-bank dissipation, 14.38 kW post-test derived active-channel output excluding end losses, and 14.80 kW calculated maximum at matched load for Test 3. The abstract calls 14.8 kW peak output, but the body table classifies 14.80 kW as a matched-load analysis value. General Atomics separately reports a preliminary 15-kW active-section peak; exact run and processing equivalence is not established. AFRL public-affairs reports 2-10 kW but does not specify which table boundary it represents. None is vehicle net output. Retained color-copy source SHA-256 (the copy used for figure crop/reproduction): 58BBB34829C30439F3D6AA1AC27E31430C01657DEF5E1F29F959598B4EE734BB. Official NTIS/NTRL PDF SHA-256: CCBC90C0BC0626328B058023D153D2F268767F85DAFD8BFD2A0DBFFACCFA1521. The files are not byte-identical. A side-by-side visual check now covers the displayed Table VI rows and separately compares Figures 16 and 17 (printed p. 16 / physical PDF p. 18): titles, axes, captions, overall time windows, principal waveform shapes and the prominent approximately 32.2 s current spike correspond. The retained third-party crops have different background/trace colors and image rendering. This is a broad visual cross-check, not a pixel-identity or point-by-point data comparison; the traces have not been digitized from the official file, and reproduction rights remain unresolved."
  ],
  "case_sweep": {
    "csv": "mhd-bypass-ledger.csv",
    "rows": 270,
    "varied": [
      "extraction_fraction",
      "generator_efficiency",
      "accelerator_efficiency",
      "assumed_field_excitation_power_kW"
    ],
    "fixed_inputs": "10 kg/s, 100 kJ/kg illustrative available energy, 20 kW other auxiliaries"
  },
  "sources": [
    {
      "citation": "Litchford, R. J., Cole, J. W., Bityurin, V. A. & Lineberry, J. T. (2000), Thermodynamic Cycle Analysis of Magnetohydrodynamic-Bypass Hypersonic Airbreathing Engines, NASA/TP-2000-210387.",
      "url": "https://ntrs.nasa.gov/citations/20000095934",
      "supports": "Conceptual inlet MHD generator, electrical bypass around heat addition, downstream accelerator, and conductivity/pre-ionization requirements; cycle analysis, not an integrated flight demonstration."
    },
    {
      "citation": "Riggins, D. W., Analysis of the Magneto-Hydrodynamic (MHD) Energy Bypass Engine for High-Speed Air-Breathing Propulsion, 2002.",
      "url": "https://ntrs.nasa.gov/citations/20020073109",
      "supports": "Configuration-specific modeled pressure losses and reduced performance compared with a conventional scramjet over studied Mach 8–12.2 cases."
    },
    {
      "citation": "Air Force Research Laboratory, Scramjet MHD System Generates Electrical Power (HVEPS), 2007.",
      "url": "https://www.wpafb.af.mil/News/Article-Display/Article/401319/scramjet-mhd-system-generates-electrical-power/",
      "supports": "Official AFRL program summary reports a Mach-8-simulating ground demonstrator with a downstream MHD generator and 2-10 kW electrical output; its public summary does not identify operating points or exact boundary. The inspected primary AFRL preprint ADA471429 Table VI reports 6.52 kW at the load bank, 14.38 kW post-test derived active-channel output, and 14.80 kW calculated matched-load maximum for Test 3. No vehicle-level net output or flight result."
    },
    {
      "citation": "Marthy, Ph. (1991), Direct current power generation in self-excited liquid metal magnetohydrodynamic generators, Magnetohydrodynamics 27(4), 455–460.",
      "url": "https://mhd.sal.lv/contents/1991/4/MG.27.4.17.R.html",
      "supports": "Self-excitation in a specific mercury-loop liquid-metal MHD generator, with a critical flow condition and strong dependence of startup transient on residual magnetic field; not a hypersonic combustion-gas device."
    },
    {
      "citation": "NASA (1970), A Design Study for a Magnetohydrodynamic Power System for Space Applications, NASA-CR-107140 / NTRS 19700024695.",
      "url": "https://ntrs.nasa.gov/citations/19700024695",
      "supports": "A specific liquid-metal MHD power-conversion design study whose generator excitation used shunt capacitors; designed spacecraft power system, not atmospheric propulsion or a free-energy loop."
    },
    {
      "citation": "Litchford, R. J. et al. (1999), Towards Integrated Pulse Detonation Propulsion and MHD Power, NASA.",
      "url": "https://ntrs.nasa.gov/citations/19990064110",
      "supports": "Small-scale lab tests and a modeled self-excited-engine concept in pulse-detonation/MHD context; not validation of hypersonic aircraft flight or a generator-to-accelerator energy-recovery loop."
    },
    {
      "citation": "Mehta, U. B., Bogdanoff, D. W., Park, C. & Arnold, J. (2001), MHD Energy Bypass Scramjet Engine, NASA workshop record 20010048659.",
      "url": "https://ntrs.nasa.gov/citations/20010048659",
      "supports": "Abstract-level progress overview. Reports few MHD gas-acceleration experiments had then been performed and describes a shock-tunnel investigation; this is not flight-loop evidence."
    },
    {
      "citation": "Air Force Research Laboratory (2007), “Scramjet MHD System Generates Electrical Power” (official HVEPS program summary).",
      "url": "https://www.wpafb.af.mil/News/Article-Display/Article/401319/scramjet-mhd-system-generates-electrical-power/",
      "supports": "Directly inspected the official AFRL page on 2026-09-30: it reports a Mach-8-simulating ground demonstrator with a downstream MHD generator and 2-10 kW electrical output, and states that output was limited only by the test rig mass-flow rate. The account gives no point-by-point data or explicit metering boundary; its range remains unreconciled with a separate General Atomics preliminary 15-kW peak and a secondary-attributed 14.8-kW value whose original AIAA abstract remains unchecked. This is component output, not vehicle-level net power or flight benefit."
    },
    {
      "citation": "Lineberry et al. (2007), “HVEPS Scramjet-Driven MHD Power Demonstration Test Results,” AFRL-PR-WP-TP-2007-233, DTIC accession ADA471429; related AIAA conference paper DOI 10.2514/6.2007-3880.",
      "url": "https://doi.org/10.2514/6.2007-3880",
      "supports": "Inspected 32-page AFRL preprint: its abstract states a 14.8-kW peak, while Table VI and notes identify 14.38 kW as active-channel output excluding end losses and 14.80 kW as calculated maximum at matched load. Table VI also reports 6.52 kW dissipated at the load bank for Test 3. These are distinct boundaries.",
      "metadata_status": "DOI metadata verified; original abstract/full paper not inspected in this review."
    }
  ],
  "provenance": "The diagram is a new explanatory synthesis. The ledger is reproducible arithmetic based on its explicitly hypothetical inputs, not digitized test data or source figure reproduction.",
  "csv_column_guide": {
    "net_stream_energy_change_kW": "Change in the chosen flow-energy account only: minus the assumed extracted power plus modeled accelerator power returned to the flow. It excludes unserved auxiliary demand, pressure loss, momentum/thrust, dissipated heat, magnet/installation mass, vehicle drag and mission effects; it is not whole-engine net power.",
    "assumed_available_stream_energy_kJ_kg": "An independently stipulated teaching input for the hypothetical stream reservoir. It is not measured MHD availability and is not the 515.7 kJ/kg inlet kinetic-to-static-enthalpy example.",
    "other_columns": "Input assumptions or intermediate quantities as named. kJ/s equals kW for the power calculations."
  },
  "scenario_plot": {
    "asset_desktop": "mhd-ledger-scenarios.svg",
    "asset_mobile": "mhd-ledger-scenarios-mobile.svg",
    "csv": "mhd-ledger-scenarios.csv",
    "fixed_inputs": {
      "mass_flow_kg_s": 10,
      "assumed_available_energy_kJ_kg": 100,
      "other_auxiliary_power_kW": 20
    },
    "series": [
      {
        "label": "Reference teaching assumptions",
        "generator_efficiency": 0.6,
        "accelerator_efficiency": 0.6,
        "field_excitation_power_kW": 15
      },
      {
        "label": "Higher selected efficiencies; no field debit",
        "generator_efficiency": 0.8,
        "accelerator_efficiency": 0.8,
        "field_excitation_power_kW": 0
      },
      {
        "label": "Lower selected efficiencies; 60 kW field debit",
        "generator_efficiency": 0.4,
        "accelerator_efficiency": 0.4,
        "field_excitation_power_kW": 60
      }
    ],
    "x": "Extraction fraction 0–60%, 1 percentage point steps",
    "y": "Net change in the modeled stream-energy account, kW; no pressure/momentum/heat/vehicle terms",
    "classification": "Synthetic arithmetic from stated assumptions, not measured data."
  },
  "hveps_output_comparison_note": "The full AFRL preprint ADA471429 is now inspected. Test 3 Table VI separates 6.52 kW dissipated in the measured external load bank, 14.38 kW as post-test derived active-channel output excluding end-region losses, and 14.80 kW as the calculated maximum at matched load. The abstract calls 14.8 kW peak electric output, while the body table and notes classify 14.80 kW as a post-test matched-load estimate; do not describe it as the measured load-bank output. The participant General Atomics preliminary 15-kW active-section value is close in scale, but run and processing equivalence is not established. The AFRL public 2-10-kW summary is compatible in scale with load-bank outputs across listed tests, but its exact boundary is not identified. Retained color-copy source SHA-256 (the copy used for figure crop/reproduction): 58BBB34829C30439F3D6AA1AC27E31430C01657DEF5E1F29F959598B4EE734BB. Official NTIS/NTRL PDF SHA-256: CCBC90C0BC0626328B058023D153D2F268767F85DAFD8BFD2A0DBFFACCFA1521. The files are not byte-identical. A side-by-side visual check now covers the displayed Table VI rows and separately compares Figures 16 and 17 (printed p. 16 / physical PDF p. 18): titles, axes, captions, overall time windows, principal waveform shapes and the prominent approximately 32.2 s current spike correspond. The retained third-party crops have different background/trace colors and image rendering. This is a broad visual cross-check, not a pixel-identity or point-by-point data comparison; the traces have not been digitized from the official file, and reproduction rights remain unresolved. No full propulsion loop or flight benefit was tested.",
  "hveps_test_series_note": "Table VI of the inspected full AFRL preprint ADA471429 lists six analysed output points: tests 1, 2, 3, 5, 6 and 7. Test 4 was not reduced because its pressure distribution was anomalous. For each point, load-bank dissipation is distinct from the active-channel output that neglects end-region losses and from maximum power at matched load calculated by post-test load-line analysis. The Site figure and table show all six points; Test 3 uses the 89% mean combustion-efficiency row, while its 81.5% and 96.5% bounds are identified separately. Values are not aircraft net power. Retained color-copy source SHA-256 (the copy used for figure crop/reproduction): 58BBB34829C30439F3D6AA1AC27E31430C01657DEF5E1F29F959598B4EE734BB. Official NTIS/NTRL PDF SHA-256: CCBC90C0BC0626328B058023D153D2F268767F85DAFD8BFD2A0DBFFACCFA1521. The files are not byte-identical. A side-by-side visual check now covers the displayed Table VI rows and separately compares Figures 16 and 17 (printed p. 16 / physical PDF p. 18): titles, axes, captions, overall time windows, principal waveform shapes and the prominent approximately 32.2 s current spike correspond. The retained third-party crops have different background/trace colors and image rendering. This is a broad visual cross-check, not a pixel-identity or point-by-point data comparison; the traces have not been digitized from the official file, and reproduction rights remain unresolved.",
  "load_coverage_threshold": {
    "equation": "f_cover = (auxiliary_demand_kW + field_excitation_demand_kW) / (mass_flow_kg_s × hypothetical_available_stream_energy_kJ_kg × generator_efficiency)",
    "reference_inputs": {
      "mass_flow_kg_s": 10,
      "hypothetical_available_stream_energy_kJ_kg": 100,
      "generator_efficiency": 0.6,
      "auxiliary_demand_kW": 20,
      "field_excitation_demand_kW": 15
    },
    "reference_result_decimal": {
      "fraction": 0.058333333333333334,
      "percent": 5.833333333333333,
      "accelerator_input_at_threshold_kW": 0,
      "accelerator_work_at_threshold_kW": 0
    },
    "same_ratio_base_12": {
      "fraction": "7/A0₁₂",
      "percent": "5.A₁₂%",
      "note": "Exact notation conversion of the reference ratio; it does not change the physical inputs, precision or result."
    },
    "interpretation": "At equality, generated electricity just serves assigned auxiliary and field loads; no electrical power remains for the accelerator. Extraction must be greater to provide accelerator input, and non-zero accelerator efficiency is required to return work.",
    "classification": "Hypothetical bookkeeping threshold, not measured MHD performance, an attainable operating point, or a vehicle break-even result."
  }
}