{
  "spore": "profile",
  "id": "avcoat",
  "spore_version": "0.2",
  "family": "epoxy-ablators",
  "name": "Avcoat",
  "abbreviation": "Avcoat",
  "role": "Charring ablative heat shield for atmospheric re-entry (Apollo command module, Orion)",
  "category": "thermal-protection",
  "type": "ablators",
  "summary": "Avcoat is a charring ablator: it protects a capsule on re-entry by burning off (ablating) and leaving an insulating char. NASA's TPSX database lists the virgin material (Avcoat-5026 H/CG) at 529 kg/m3 and 0.242 W/m-K thermal conductivity at standard conditions. NASA TN D-2991 measured the room-temperature density of the Avcoat 5026-39-HC G material at 530.0 kg/m3 (75 °F) and its thermal conductivity at 0.0502 W/m-K at 154 K (-182 °F, direction C). In the enthalpy test of TN D-2991 the material had lost 11.2 % of its weight by 533.7 K (502 °F) and 27.5 % by 661.9 K (733 °F).\n",
  "best_for": "Single-use heat shields for atmospheric re-entry, the design role NASA used it for on Apollo and on the Orion EM-1 capsule",
  "weakest_at": "Single use: the material is designed to char and erode on every entry, so the shield is consumed. Its decomposition model is fitted from thermogravimetric data, and the Orion paper reports large uncertainty in the reaction orders.",
  "identity": {
    "formula": "Epoxy novolac resin filled with silica microballoons, phenolic microballoons and silica fibres, in a honeycomb (exact recipe proprietary)",
    "designations": [
      {
        "system": "Trade name",
        "code": "Avcoat 5026-39-HC G",
        "source": "tn-d2991",
        "where": "Section Materials, paragraph naming the commercial designation (Avco Corporation, Research and Advanced Development Division)"
      },
      {
        "system": "Trade name",
        "code": "AVCOAT-5026 H/CG",
        "source": "tpsx-avcoat",
        "where": "Page title and Name field (Avcoat-5026 H/CG [virgin])"
      }
    ],
    "source": "tpsx-avcoat",
    "where": "Description (constituents) and Name fields. TN D-2991 calls the material a low-density filled epoxy in honeycomb and says its composition is proprietary."
  },
  "tags": {
    "environments": [
      "re-entry"
    ],
    "stresses": [],
    "applications": [
      "heat-shields"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Room-temperature density, low-density filled epoxy in honeycomb (Avcoat 5026-39-HC G)",
      "value": 530,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "temperature": "75 °F (297 K), room-temperature measurement",
        "form": "low-density filled epoxy in honeycomb (Melpar)",
        "printed_in_source": "33.09 lb/ft3"
      },
      "method": "Room-temperature measurement (Table 6 footnote b). Printed in lb/ft3 and kg/m3; the kg/m3 value is copied as printed.",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 6 (Density), Avcoat block, row at 75 °F (297 K) marked b. For comparison, the carbon-fibre-reinforced phenolic Narmco 4028 row at the same 75 °F reads 1390 kg/m3 in the same table.",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density after heating, low-density filled epoxy in honeycomb (Avcoat 5026-39-HC G)",
      "value": 467.7,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "temperature": "500 °F (532 K)",
        "form": "low-density filled epoxy in honeycomb (Melpar)",
        "printed_in_source": "29.20 lb/ft3"
      },
      "method": "Calculated from thermal-expansion data and weight measurements after exposure to temperature (Table 6 footnote a)",
      "status": "calculated",
      "source": "tn-d2991",
      "where": "Table 6 (Density), Avcoat block, row at 500 °F (532 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, Avcoat 5026-39-HC G (direction C), low temperature",
      "value": 0.0502,
      "bound": "exact",
      "unit": "W/m-K",
      "scope": "material",
      "conditions": {
        "temperature": "-182 °F (154 K) mean temperature",
        "direction": "C",
        "specimen": "1",
        "printed_in_source": "0.0290 Btu/ft-hr-F"
      },
      "method": "Measured by Melpar (Table 3). The SI value is copied as printed.",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 3 (Thermal conductivity), Avcoat row, first row at -182 °F (154 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, Avcoat 5026-39-HC G (direction C), 491 °F",
      "value": 0.109,
      "bound": "exact",
      "unit": "W/m-K",
      "scope": "material",
      "conditions": {
        "temperature": "491 °F (528 K) mean temperature",
        "direction": "C",
        "specimen": "5",
        "printed_in_source": "0.0631 Btu/ft-hr-F"
      },
      "method": "Measured by Melpar (Table 3). The SI value is copied as printed.",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 3 (Thermal conductivity), Avcoat row at 491 °F (528 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "specific_heat",
      "label": "Specific heat, low-density filled epoxy in honeycomb (Avcoat 5026-39-HC G), low temperature",
      "value": 0.606,
      "bound": "exact",
      "unit": "kJ/kg-K",
      "scope": "material",
      "conditions": {
        "temperature": "-200 °F (144 K)",
        "form": "low-density filled epoxy in honeycomb (Melpar)",
        "printed_in_source": "0.145 Btu/lb-F"
      },
      "method": "Measured by Melpar (Table 2). The SI value is copied as printed.",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 2 (Specific heat), Avcoat row at -200 °F (144 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "specific_heat",
      "label": "Specific heat, low-density filled epoxy in honeycomb (Avcoat 5026-39-HC G), high temperature",
      "value": 1.78,
      "bound": "exact",
      "unit": "kJ/kg-K",
      "scope": "material",
      "conditions": {
        "temperature": "750 °F (671 K)",
        "form": "low-density filled epoxy in honeycomb (Melpar)",
        "printed_in_source": "0.425 Btu/lb-F"
      },
      "method": "Measured by Melpar (Table 2). The SI value is copied as printed.",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 2 (Specific heat), Avcoat row at 750 °F (671 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "emissivity",
      "label": "Emissivity (TPSX)",
      "value": 0.667,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "stp_flag": "assumed/assumed (TPSX)",
        "form": "virgin Avcoat-5026 H/CG"
      },
      "method": "Database value printed in TPSX as 6.67e-01. TPSX marks it as assumed, not measured.",
      "status": "calculated",
      "source": "tpsx-avcoat",
      "where": "Properties at Standard Conditions table, Emissivity row",
      "source_detail": {
        "title": "NASA Ames Thermal Protection Materials Database: Avcoat-5026 H/CG [virgin]",
        "id": "TPSX material id 37 (Last Modified 1996-02-01)",
        "url": "https://tpsx.arc.nasa.gov/Material?id=37",
        "year": 1996,
        "kind": "database",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "enthalpy_change",
      "label": "Enthalpy change of the material on heating to 733 °F, relative to 32 °F",
      "value": 0.6364,
      "bound": "exact",
      "unit": "MJ/kg",
      "scope": "material",
      "conditions": {
        "temperature": "733 °F (661.9 K)",
        "reference_temperature": "32 °F (273 K)",
        "form": "low-density filled epoxy in honeycomb (Melpar)",
        "printed_in_source": "273.37 Btu/lb"
      },
      "method": "Measured in the enthalpy test reported in Table 1. The SI value is copied as printed.",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 1 (Enthalpy), Avcoat row at 733.0 °F (661.9 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "weight_loss",
      "label": "Weight loss on heating to 733 °F",
      "value": 27.5,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "temperature": "733 °F (661.9 K)",
        "form": "low-density filled epoxy in honeycomb (Melpar)"
      },
      "method": "Weight loss measured with the enthalpy data (Table 1, weight-loss column)",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 1 (Enthalpy), weight-loss column, Avcoat row at 733.0 °F (661.9 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "weight_loss",
      "label": "Weight loss on heating to 502 °F",
      "value": 11.2,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "temperature": "502 °F (533.7 K)",
        "form": "low-density filled epoxy in honeycomb (Melpar)"
      },
      "method": "Weight loss measured with the enthalpy data (Table 1, weight-loss column)",
      "status": "ground",
      "source": "tn-d2991",
      "where": "Table 1 (Enthalpy), weight-loss column, Avcoat row at 502.0 °F (533.7 K)",
      "source_detail": {
        "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
        "id": "NASA TN D-2991; NTRS 19650024901",
        "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
        "year": 1965,
        "kind": "report",
        "license": "public domain (NASA)"
      }
    },
    {
      "benchmark": "normalized_ablation_rate_uncertainty",
      "label": "Uncertainty of the normalized ablation rate (char recession rate, Bc')",
      "value": 0.15,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "basis": "uncertainty u = 2 x (standard deviation / mean), Monte Carlo runs of the ACE wrapper script",
        "form": "molded Avcoat (Orion)"
      },
      "method": "Relative uncertainty calculated by the authors (Eq. 3); not a measured property of the material",
      "status": "calculated",
      "source": "orion-avcoat-uq",
      "where": "Table 1 (Resulting uncertainty values), row Char Recession Rate Bc', Current Study column",
      "source_detail": {
        "title": "Determination of Uncertainties for Analytically Derived Material Properties to be used in Monte Carlo Based Orion Heatshield Sizing (Coughlin, Sixel, Sepka, McGuire)",
        "id": "NTRS 20190029074",
        "url": "https://ntrs.nasa.gov/api/citations/20190029074/downloads/20190029074.pdf",
        "year": 2019,
        "kind": "paper",
        "license": "NASA-authored (NTRS)"
      }
    },
    {
      "benchmark": "pyrolysis_gas_enthalpy_uncertainty",
      "label": "Uncertainty of the pyrolysis gas enthalpy",
      "value": 0.18,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "basis": "uncertainty u = 2 x (standard deviation / mean), Monte Carlo runs of the ACE wrapper script",
        "form": "molded Avcoat (Orion)"
      },
      "method": "Relative uncertainty calculated by the authors (Eq. 3); not a measured property of the material",
      "status": "calculated",
      "source": "orion-avcoat-uq",
      "where": "Table 1 (Resulting uncertainty values), row Pyrolysis gas Enthalpy, Current Study column",
      "source_detail": {
        "title": "Determination of Uncertainties for Analytically Derived Material Properties to be used in Monte Carlo Based Orion Heatshield Sizing (Coughlin, Sixel, Sepka, McGuire)",
        "id": "NTRS 20190029074",
        "url": "https://ntrs.nasa.gov/api/citations/20190029074/downloads/20190029074.pdf",
        "year": 2019,
        "kind": "paper",
        "license": "NASA-authored (NTRS)"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Heating to 502 °F and 733 °F in the enthalpy test (thermal decomposition, no oxidation data)",
      "headline": "Avcoat loses 11.2 % of its weight by 502 °F and 27.5 % by 733 °F in the enthalpy test.",
      "effect": "The TN report says weight loss in these tests comes from the loss of volatile products from thermochemical reaction, and the density figures were corrected for it. This decomposition is the designed ablation, not a corrosion failure.",
      "rating": "moderate",
      "conditions": {
        "basis": "weight loss reported with the enthalpy data; test atmosphere not printed in the sections read",
        "form": "low-density filled epoxy in honeycomb (Melpar)"
      },
      "source": "tn-d2991",
      "where": "Table 1 (weight-loss column); Density section, paragraph on bulk density of virgin materials"
    },
    {
      "environment": "Thermal decomposition modelled from thermogravimetric analysis (TGA) of molded Avcoat",
      "headline": "A single Arrhenius reaction does not fit molded Avcoat, so the Orion team fitted three.",
      "effect": "The Orion paper fits three Arrhenius equations to six TGA runs with nine independent parameters. The best-fit reaction orders vary greatly, so their uncertainty is high (see the decomposition uncertainties in watch_out).",
      "rating": "moderate",
      "conditions": {
        "basis": "six laboratory TGA measurements, nine fitted Arrhenius parameters",
        "form": "molded Avcoat (Orion)"
      },
      "source": "orion-avcoat-uq",
      "where": "Section II.A (Decomposition Parameters) and Figure 1"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem silica record (CID 24261) pools company reports, and its summary notes say information may vary between notifications depending on impurities, additives and other factors. The largest block reads Not Classified, reported as not meeting GHS hazard criteria per 7724 of 9127 reports by companies. Other blocks in the record give H315, H319 and H335 (skin, eye and respiratory irritation) and H350 and H372 (may cause cancer; organ damage from prolonged or repeated exposure). The extracted record does not say which silica form each block covers, so it is not specific to the silica fibres in Avcoat.",
        "ghs": [],
        "source": "pubchem-silica",
        "where": "Safety and Hazards, GHS Classification (CID 24261): summary note and GHS Hazard Statements blocks, with their report counts"
      },
      {
        "text": "Bisphenol A diglycidyl ether (BADGE, CID 2286) is a bisphenol-A epoxy, not the epoxy novolac resin in Avcoat. PubChem lists H315 (causes skin irritation), H317 (may cause an allergic skin reaction) and H319 (causes serious eye irritation) in its company reports, and one notification block adds H411 (toxic to aquatic life with long lasting effects) for 50.9% of its reports.",
        "ghs": [],
        "source": "pubchem-badge",
        "where": "Safety and Hazards, GHS Classification (CID 2286): GHS Hazard Statements blocks"
      },
      {
        "text": "Phenolic resin (PubChem CID 24754) is the nearest class in PubChem to the phenolic microballoons in Avcoat; the sources read do not confirm that the microballoons are this resin. PubChem lists H317 (may cause an allergic skin reaction) for 100% of 4 company reports from 2 notifications, and H302 (harmful if swallowed) and H312 (harmful in contact with skin) from a single company notification.",
        "ghs": [],
        "source": "pubchem-phenolic",
        "where": "Safety and Hazards, GHS Classification (CID 24754): GHS Hazard Statements blocks"
      }
    ],
    "failure_risks": [
      {
        "mode": "Decomposition kinetics uncertainty in the heat-shield model",
        "trigger": "Predicting char recession with Arrhenius parameters fitted to TGA data",
        "consequence": "The Orion paper reports relative uncertainty of 0.263 to 0.388 in the decomposition reaction orders, and says the fitted reaction orders varied greatly.",
        "severity": "moderate",
        "source": "orion-avcoat-uq",
        "where": "Section III (Results) and Table 2 (Decomposition Parameter Uncertainties)"
      }
    ],
    "side_effects": [
      {
        "text": "Decomposition releases pyrolysis gas, which the Orion model handles through a pyrolysis gas enthalpy table with a relative uncertainty of 0.18.",
        "affects": "Heat transfer to the structure under the shield in the sizing model",
        "source": "orion-avcoat-uq",
        "where": "Section II.B (Pyrolysis Gas Enthalpy) and Table 1"
      }
    ],
    "handling": [],
    "mitigations": [
      {
        "text": "The current Orion sizing method reduces the allowable bondline temperature limit by 60 °C to cover material property uncertainty. The paper asks whether that value is still appropriate for molded Avcoat.",
        "source": "orion-avcoat-uq",
        "where": "Section I (Introduction), paragraphs 2 and 3"
      }
    ]
  },
  "uses": [
    {
      "application": "heat-shields",
      "device": "Apollo command module heat shield",
      "example": "TPSX states that AVCOAT was used as the primary heatshield for Apollo.",
      "source": "tpsx-avcoat",
      "where": "Description field"
    },
    {
      "application": "heat-shields",
      "device": "Apollo command module heat shield, flight history",
      "example": "The Avcoat article says it flew on uncrewed tests (AS-201, AS-202, Apollo 4, Apollo 6) and on crewed missions from Apollo 7 through Apollo 17, plus Skylab 2 to 4 and Apollo-Soyuz.",
      "source": "wiki-avcoat",
      "where": "History and Apollo Command Module sections"
    },
    {
      "application": "heat-shields",
      "device": "Orion EM-1 crew module heat shield (molded Avcoat)",
      "example": "The Orion paper says the EM-1 capsule has been designed to use a molded Avcoat material system, and that the heat shield thickness is sized with Monte Carlo analysis of material uncertainty.",
      "source": "orion-avcoat-uq",
      "where": "Section I (Introduction), first paragraph"
    },
    {
      "application": "heat-shields",
      "device": "Orion capsule on Artemis I (uncrewed, 2022)",
      "example": "The Avcoat article says the Artemis I shield was redesigned to use shaped AVCOAT blocks, and that Artemis I flew uncrewed in 2022.",
      "source": "wiki-avcoat",
      "where": "Orion EFT-1 and Artemis I sections"
    }
  ],
  "supply": [
    {
      "subject": "Silica (feedstock for the silica fibres and silica microballoons)",
      "abundance": "USGS Silicon chapter: 'The source of the silicon is silica in various natural forms, such as quartzite.' It also says 'World and domestic resources for making silicon metal and alloys are abundant.'",
      "producers": [],
      "critical_lists": [],
      "substitutes": [],
      "source": "usgs-mcs2026-silicon",
      "where": "Silicon chapter, World Resources and Domestic Production and Use paragraphs. The chapter covers silicon metal and ferrosilicon, not silica fibre, so it gives no silica producers. The chapter says silicon was added to the U.S. Final 2025 List of Critical Minerals; that listing is for silicon, not silica."
    },
    {
      "subject": "AVCOAT material (produced by Lockheed Martin, licensed by Textron)",
      "producers": [
        {
          "country": "United States"
        }
      ],
      "critical_lists": [],
      "substitutes": [],
      "source": "wiki-avcoat",
      "where": "Orion EFT-1 Crew Module section, paragraph beginning 'Licensed by Textron': 'AVCOAT material is produced at New Orleans's Michoud Assembly Facility by Lockheed Martin.' The page names New Orleans, not the country; United States is taken from that city. No production shares are given."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "NASA Ames TPSX Materials Database: AVCOAT-5026 H/CG [virgin]",
      "type": "database",
      "url": "https://tpsx.arc.nasa.gov/Material?id=37",
      "year": 1996
    },
    {
      "title": "NASA TN D-2991: Thermophysical Properties of Six Charring Ablators (R. Gale Wilson, compiler)",
      "type": "report",
      "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
      "year": 1965
    },
    {
      "title": "Determination of Uncertainties for Analytically Derived Material Properties to be used in Monte Carlo Based Orion Heatshield Sizing (NTRS 20190029074)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/api/citations/20190029074/downloads/20190029074.pdf",
      "year": 2019
    },
    {
      "title": "PubChem compound record, Silica (CID 24261)",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/24261",
      "year": 2026
    },
    {
      "title": "PubChem compound record, Bisphenol A diglycidyl ether (CID 2286)",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/2286",
      "year": 2026
    },
    {
      "title": "PubChem compound record, Phenolic resin (CID 24754)",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/24754",
      "year": 2026
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Silicon",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf",
      "year": 2026
    }
  ],
  "gaps": [
    "No safety data sheet or GHS classification for Avcoat 5026-39-HC G itself was found. risks.hazards holds PubChem entries for three constituent classes (silica, a bisphenol-A epoxy and a phenolic resin), which are not the proprietary Avcoat formulation. Check the supplier's SDS before handling.",
    "No handling, storage or shelf-life guidance was found in the sources read.",
    "No humidity, moisture-absorption, UV or chemical-resistance data were found. Only the enthalpy-test weight loss and the Orion decomposition model are reported.",
    "No production shares were found for Avcoat. The Wikipedia article names Lockheed Martin as producer at Michoud and Textron as licensor, but gives no shares. The USGS silicon chapter describes silica feedstock in general terms only and gives no silica-fibre producers.",
    "Mechanical properties (tensile, compressive, Young's modulus) for Avcoat in TN D-2991 Tables 7 to 10 were not transcribed; the scanned tables are hard to read reliably in this run.",
    "Virgin composition percentages were not found; TN D-2991 says the composition is proprietary.",
    "Post-flight condition after Artemis I is reported differently: the Avcoat article says post-flight inspection found material loss, and the Orion article reports no heat-shield findings. Neither claim was confirmed in a primary NASA source in this run, so no failure is listed.",
    "Mean Arrhenius parameters (pre-exponential factors, activation temperatures) from Orion Table 2 were not stored. Only the uncertainties are in the file.",
    "The TPSX blowing corrections (0.7 laminar, 0.37 turbulent) are marked assumed and are not stored as properties.",
    "Custom property names used because no canonical name exists in property-canon.yaml: emissivity, effective_heat_of_ablation, enthalpy_change, weight_loss, normalized_ablation_rate_uncertainty, pyrolysis_gas_enthalpy_uncertainty.",
    "No flight-condition char recession or ablation rate data were read; the Orion paper gives only uncertainties on these inputs.",
    "Wikipedia pages are used for history, composition and the producer name only; no numbers are taken from them."
  ],
  "story": {
    "why": "Avcoat is the ablative heat shield NASA used on Apollo and designed into the Orion EM-1 capsule. An ablator protects the vehicle by burning away and forming an insulating char on re-entry. The sources here describe a low-density epoxy-based material, and the data show how its density, thermal conductivity and specific heat change with temperature, and how much of its weight is lost as it heats.",
    "uses": [
      {
        "where": "Apollo command module",
        "line": "TPSX states that AVCOAT was the primary heat shield for Apollo. The Avcoat article lists uncrewed tests from AS-201 and AS-202 to Apollo 6, and crewed missions from Apollo 7 through Apollo 17."
      },
      {
        "where": "Orion EM-1 capsule",
        "line": "The Orion paper says the EM-1 capsule has been designed to use a molded Avcoat material system, and that its heat shield thickness is sized with a Monte Carlo analysis that includes the material's own uncertainties."
      },
      {
        "where": "Artemis I (uncrewed, 2022)",
        "line": "The Avcoat article says the Artemis I shield was redesigned to use shaped AVCOAT blocks, and that Artemis I flew uncrewed in 2022. The post-flight condition of the shield is not confirmed in the sources read."
      }
    ],
    "can_do": [
      {
        "label": "Density",
        "line": "Room-temperature density of the low-density filled epoxy in honeycomb is 530.0 kg/m3 at 75 °F, measured in TN D-2991. TPSX gives 529 kg/m3 for the virgin material at standard conditions, which it marks as assumed.",
        "benchmark": "density",
        "scope": "material",
        "value": "530.0 kg/m3 at 75 °F"
      },
      {
        "label": "Heat absorbed",
        "line": "In the TN D-2991 enthalpy test, the material absorbed 0.6364 MJ/kg of enthalpy on heating to 733 °F (661.9 K), relative to 32 °F.",
        "benchmark": "enthalpy_change",
        "scope": "material",
        "value": "0.6364 MJ/kg at 733 °F"
      },
      {
        "label": "Thermal conductivity",
        "line": "Thermal conductivity in direction C is 0.0502 W/m-K at 154 K (-182 °F) and 0.109 W/m-K at 528 K (491 °F), both measured by Melpar in TN D-2991.",
        "benchmark": "thermal_conductivity",
        "scope": "material",
        "value": "0.0502 W/m-K at 154 K"
      },
      {
        "label": "Specific heat",
        "line": "Specific heat rises from 0.606 kJ/kg-K at 144 K (-200 °F) to 1.78 kJ/kg-K at 671 K (750 °F), per Table 2 of TN D-2991.",
        "benchmark": "specific_heat",
        "scope": "material",
        "value": "0.606 kJ/kg-K at 144 K"
      }
    ],
    "compare": "The only other material in these sources with a measured density at the same temperature is the carbon-fibre-reinforced phenolic Narmco 4028, tested in TN D-2991. At 75 °F, Avcoat's density is 530.0 kg/m3, against 1390 kg/m3 for Narmco 4028, so Avcoat is much the lighter of the two. The Orion paper names PICA and another earlier ablator as comparison points, but these sources give no property values for them, so no further comparison is made.",
    "compare_rows": [
      {
        "label": "Room-temperature density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Thermal conductivity",
        "benchmark": "thermal_conductivity",
        "scope": "material"
      },
      {
        "label": "Specific heat",
        "benchmark": "specific_heat",
        "scope": "material"
      }
    ],
    "handling": [
      "No handling or storage guidance was found in the sources read. Do not assume a hazard classification without the supplier's safety data sheet.",
      "Treat the material as single-use: it is designed to char and erode on each re-entry."
    ],
    "good_for": [
      "Single-use re-entry heat shields. NASA used this design role on Apollo and on the Orion EM-1 capsule.",
      "Low-density thermal protection: 530.0 kg/m3 at room temperature in TN D-2991."
    ],
    "watch_out": [
      "Post-flight condition after Artemis I is reported differently by two sources, and neither was confirmed in a primary NASA source in this run.",
      "The decomposition model is fitted, not measured directly: the Orion paper reports reaction-order uncertainties of 0.263 to 0.388 and says the fitted reaction orders varied greatly.",
      "Thermal conductivity rises with temperature in direction C: 0.0502 W/m-K at 154 K and 0.109 W/m-K at 528 K, so use the value at the temperature of interest."
    ],
    "verdict": "Avcoat is the heritage ablator: NASA used it on Apollo and designed Orion EM-1 around it. Most property values here come from a 1965 report and a database, so check them against current NASA data before any design use, and get a hazard data sheet before handling.",
    "recipe": {
      "line": "Avcoat is a composite, not a single compound. TPSX lists its constituents as an epoxy novolac resin, silica microballoons, phenolic microballoons and silica fibres, in a honeycomb. The exact proportions are proprietary (TN D-2991).",
      "parts": [
        {
          "name": "Epoxy novolac resin",
          "role": "Binder that holds the fillers together; it decomposes on heating to form the char."
        },
        {
          "name": "Silica microballoons",
          "role": "Hollow silica spheres listed by TPSX as a filler."
        },
        {
          "name": "Phenolic microballoons",
          "role": "Hollow phenolic spheres listed by TPSX as a filler."
        },
        {
          "name": "Silica fibres",
          "role": "Fibre reinforcement listed by TPSX as a constituent."
        },
        {
          "name": "Honeycomb",
          "role": "Cell structure that holds the filled resin. TPSX lists phenolic or stainless-steel honeycomb."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "No safety data sheet for Avcoat 5026-39-HC G was read in this run. PubChem gives hazard statements for three constituent classes, but not for the proprietary Avcoat formulation.",
        "points": [
          {
            "label": "Constituents",
            "line": "PubChem lists skin, eye and respiratory irritation and skin sensitisation for these classes. Its silica record also carries cancer and organ-damage statements that it does not tie to a silica form. Check the supplier's safety data sheet before handling any Avcoat material."
          }
        ],
        "verdict": "Constituent hazards only"
      },
      {
        "title": "On re-entry",
        "lead": "The shield is designed to char and erode during entry, and the sources give the heating and weight-loss data for that process.",
        "points": [
          {
            "label": "Weight loss",
            "line": "In the TN D-2991 enthalpy test, the material had lost 11.2 % of its weight by 502 °F and 27.5 % by 733 °F."
          },
          {
            "label": "Design margin",
            "line": "The Orion sizing method reduces the allowable bondline temperature limit by 60 °C to cover material property uncertainty."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "lead": "No handling or storage guidance was found in the sources read.",
        "points": [
          {
            "label": "Storage",
            "line": "No storage or shelf-life data were found. Treat the material as single-use: it is designed to char and erode on each entry."
          }
        ]
      }
    ]
  },
  "updated": "2026-11-02",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 12,
    "unreachable": 0,
    "caveats": 0,
    "note": "Written by an AI assistant on 2026-11-01 from three NASA documents and two Wikipedia pages read in this run. Deepened on 2026-11-02 with hazard entries from three PubChem records and supply entries from the USGS silicon chapter and the Wikipedia article; property count unchanged. Values were copied as printed; table values were read from rendered page images of TN D-2991 Tables 1, 2, 3 and 6. Not yet checked by a second reader."
  },
  "sources": {
    "tpsx-avcoat": {
      "title": "NASA Ames Thermal Protection Materials Database: Avcoat-5026 H/CG [virgin]",
      "id": "TPSX material id 37 (Last Modified 1996-02-01)",
      "url": "https://tpsx.arc.nasa.gov/Material?id=37",
      "year": 1996,
      "kind": "database",
      "license": "public domain (NASA)"
    },
    "tn-d2991": {
      "title": "Thermophysical Properties of Six Charring Ablators from 140 to 700 K and Two Chars from 800 to 3000 K (NASA TN D-2991, R. Gale Wilson, compiler, NASA Langley)",
      "id": "NASA TN D-2991; NTRS 19650024901",
      "url": "https://ntrs.nasa.gov/api/citations/19650024901/downloads/19650024901.pdf",
      "year": 1965,
      "kind": "report",
      "license": "public domain (NASA)"
    },
    "orion-avcoat-uq": {
      "title": "Determination of Uncertainties for Analytically Derived Material Properties to be used in Monte Carlo Based Orion Heatshield Sizing (Coughlin, Sixel, Sepka, McGuire)",
      "id": "NTRS 20190029074",
      "url": "https://ntrs.nasa.gov/api/citations/20190029074/downloads/20190029074.pdf",
      "year": 2019,
      "kind": "paper",
      "license": "NASA-authored (NTRS)"
    },
    "wiki-avcoat": {
      "title": "Avcoat (Wikipedia article, read for composition, manufacturer and flight history only)",
      "id": "Wikipedia, read in this run",
      "url": "https://en.wikipedia.org/wiki/Avcoat",
      "year": 2026,
      "kind": "web",
      "license": "CC BY-SA 4.0 (Wikipedia)"
    },
    "wiki-orion": {
      "title": "Orion (spacecraft) (Wikipedia article, read for the Artemis I flight date and heat-shield context)",
      "id": "Wikipedia, read in this run",
      "url": "https://en.wikipedia.org/wiki/Orion_(spacecraft)",
      "year": 2026,
      "kind": "web",
      "license": "CC BY-SA 4.0 (Wikipedia)"
    },
    "pubchem-silica": {
      "title": "PubChem compound record, Silica (CID 24261)",
      "id": "CID 24261",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/24261",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-badge": {
      "title": "PubChem compound record, Bisphenol A diglycidyl ether (CID 2286)",
      "id": "CID 2286",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/2286",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "pubchem-phenolic": {
      "title": "PubChem compound record, Phenolic resin (CID 24754)",
      "id": "CID 24754",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/24754",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "usgs-mcs2026-silicon": {
      "title": "USGS Mineral Commodity Summaries 2026: Silicon",
      "id": "USGS MCS 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/avcoat/"
}