spore: profile
id: pica
spore_version: 0.2
family: carbon-phenolic
name: Phenolic Impregnated Carbon Ablator
abbreviation: PICA
role: Ablative heat shield for atmospheric entry (carbon-fibre preform infused with phenolic resin)
category: thermal-protection
type: ablators
summary: |
  PICA (Phenolic Impregnated Carbon Ablator) is a low-density heat shield made from a rigid carbon-fibre preform, called FiberForm, infused with phenolic resin. The 1998 NASA annual report gives a nominal density of 224 to 248 kg/m^3 for PICA, depending on phenolic loading. PICA was the forebody heat shield of the Stardust sample-return capsule, launched in February 1999, and was used in a tiled layout on Mars Science Laboratory.
best_for: Entry heat shields that need a light carbon-phenolic ablator with flight heritage (Stardust; Mars Science Laboratory in tiled form)
weakest_at: 'Supply: the rayon precursor has been replaced at least twice in the past 25 years (Gasch et al.), and the sources read here give no hazard, ageing or humidity data'
identity:
  formula: Carbon-fibre substrate (FiberForm) impregnated with phenolic resin (Durite SC-1008); a composite, not a single compound
  source: selvaduray1998
  where: Materials section (PICA uses FiberForm and the phenolic resin Durite SC-1008)
tags:
  environments:
    - re-entry
  stresses:
    - extreme-heat
  applications:
    - heat-shields
properties:
  - benchmark: density
    label: Density range, PICA after phenolic impregnation
    value: 224
    value_high: 248
    bound: range
    unit: kg/m^3
    scope: material
    conditions:
      phenolic_loading: depends on the level of phenolic loading
      form: nominal range for the impregnated preform
    method: Nominal range stated in the 1998 NASA annual report
    status: ground
    note: Printed as 224 to 248 kg/m^3 (14 to 15.5 lb/ft^3).
    source: selvaduray1998
    where: Materials section, paragraph on the nominal density of PICA
  - benchmark: density
    label: Density range, FiberForm substrate before impregnation
    value: 144
    value_high: 176
    bound: range
    unit: kg/m^3
    scope: material
    conditions:
      form: FiberForm carbon-fibre substrate, not impregnated
      basis: nominal range
    method: Nominal range stated in the 1998 NASA annual report
    status: ground
    note: Printed as 144 to 176 kg/m^3 (9.0 to 11 lb/ft^3).
    source: selvaduray1998
    where: Materials section, first density sentence
  - benchmark: specific_heat
    label: Specific heat, virgin PICA
    value: 1200
    unit: J/kg-K
    scope: material
    conditions:
      temperature: not printed on the page
      standard_conditions_flag: TRUE (TPSX column)
    method: Value listed in the TPSX database; its source column says unknown
    status: ground
    note: Printed as 1.20e+03 J/kg-K.
    source: tpsx-pica
    where: Properties at Standard Conditions table, Specific Heat row
  - benchmark: emissivity
    label: Emissivity, virgin PICA
    value: 0.8
    unit: '-'
    scope: material
    conditions:
      temperature: not printed on the page
      standard_conditions_flag: assumed/assumed (TPSX column)
    method: Value listed in the TPSX database; its source column says measured
    status: ground
    source: tpsx-pica
    where: Properties at Standard Conditions table, Emissivity row
  - benchmark: char_yield
    label: Char yield of the phenolic resin in PICA
    value: 0.63
    unit: '-'
    scope: material
    conditions:
      atmosphere: argon gas flow
      temperature: about 1250 K, in a tube furnace
      material: phenolic resin in PICA
    method: Specimens cycled to about 1250 K under argon; the report defines char yield as the mass remaining after pyrolysis
    status: ground
    note: The report defines char yield as a percentage of mass remaining, but prints 0.63 with no unit. The report does not say whether that is a fraction or a percent.
    source: selvaduray1998
    where: Charring paragraph, char yield V of the phenolic resin in PICA
  - benchmark: centerline_recession
    label: Centerline recession, arc-jet condition 1, model AA-43-209-N
    value: 2.33
    unit: mm
    scope: material
    conditions:
      condition_number: '1'
      exposure_time: 55 s
      thermocouple_option: A
      heat_flux: 'not read: Table 2 is not legible in the extracted text'
    method: Arc-jet test of a PICA model; centerline recession measured by the authors
    status: ground
    note: A second model under the same condition, AA-43-210-N, recessed 2.27 mm.
    source: milos2009
    where: Table 4, condition 1, model AA-43-209-N
  - benchmark: centerline_recession
    label: Centerline recession, arc-jet condition 2b, model AT-007
    value: 24.72
    unit: mm
    scope: material
    conditions:
      condition_number: 2b
      exposure_time: 400 s
      thermocouple_option: none
      heat_flux: 'not read: Table 2 is not legible in the extracted text'
    method: Arc-jet test of a PICA model; centerline recession measured by the authors
    status: ground
    source: milos2009
    where: Table 4, condition 2b, model AT-007
  - benchmark: max_surface_temperature
    label: Maximum surface temperature, arc-jet condition 1, model AA-43-209-N
    value: 2033
    unit: K
    scope: material
    conditions:
      condition_number: '1'
      exposure_time: 55 s
      heat_flux: 'not read: Table 2 is not legible in the extracted text'
    method: Arc-jet test of a PICA model; maximum surface temperature measured by the authors
    status: ground
    note: A second model under the same condition, AA-43-210-N, reached 2041 K.
    source: milos2009
    where: Table 4, condition 1, model AA-43-209-N
  - benchmark: max_surface_temperature
    label: Maximum surface temperature, arc-jet condition 2b, model AT-007
    value: 2196
    unit: K
    scope: material
    conditions:
      condition_number: 2b
      exposure_time: 400 s
      heat_flux: 'not read: Table 2 is not legible in the extracted text'
    method: Arc-jet test of a PICA model; maximum surface temperature measured by the authors
    status: ground
    source: milos2009
    where: Table 4, condition 2b, model AT-007
  - benchmark: density
    label: Average density, Lyocell-based PICA (PICA-D)
    value: 0.28
    unit: g/cc
    scope: material
    conditions:
      precursor: Lyocell carbon fibre (PICA-D), average of the samples shown
    method: Average value in the Mechanical Property Comparison table of the NASA Ames slides; the slides do not print a test method for density
    status: ground
    note: Printed as 0.28 with unit g/cc.
    source: stackpoole2018
    where: Mechanical Property Comparison table, Density column, Average Lyocell PICA row
  - benchmark: density
    label: Approximate density, PICA (background section of the slides)
    value: 0.27
    unit: g/cc
    scope: material
    conditions:
      precursor: heritage rayon-based PICA, as described in the background section
      basis: approximate
    method: Approximate value given in the background section of the slides
    status: ground
    note: Printed as "~ 0.27g/cm3"; the tilde means approximately and is kept from the slide.
    source: stackpoole2018
    where: Background section, first bullet
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 100°F, Lyocell-based PICA (PICA-D), average
    value: 0.94
    unit: BTU-in/hr-ft2-oF
    scope: material
    conditions:
      temperature: 100°F
      precursor: Lyocell carbon fibre (PICA-D), average
    method: Average shown in the Thermal Property Comparison table of the NASA Ames slides; the slides do not print the test method
    status: ground
    source: stackpoole2018
    where: Thermal Property Comparison table, Average Lyocell PICA row, 100°F column
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 350°F, Lyocell-based PICA (PICA-D), average
    value: 1.32
    unit: BTU-in/hr-ft2-oF
    scope: material
    conditions:
      temperature: 350°F
      precursor: Lyocell carbon fibre (PICA-D), average
    method: Average shown in the Thermal Property Comparison table of the NASA Ames slides; the slides do not print the test method
    status: ground
    source: stackpoole2018
    where: Thermal Property Comparison table, Average Lyocell PICA row, 350°F column
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 100°F, heritage rayon-based PICA, range
    value: 1
    value_high: 1.5
    bound: range
    unit: BTU-in/hr-ft2-oF
    scope: material
    conditions:
      temperature: 100°F
      precursor: heritage rayon-based PICA
    method: Range shown in the Thermal Property Comparison table of the NASA Ames slides
    status: ground
    note: Printed as 1.0 – 1.5 for rayon PICA at 100°F.
    source: stackpoole2018
    where: Thermal Property Comparison table, Rayon PICA row, 100°F column
  - benchmark: ultimate_tensile_strength
    label: In-plane failure stress, Lyocell-based PICA (PICA-D), average
    value: 246
    unit: psi
    scope: material
    conditions:
      orientation: in-plane (IP)
      precursor: Lyocell carbon fibre (PICA-D), average
    method: Average failure stress in the Mechanical Property Comparison table of the NASA Ames slides; the slides do not name the test standard
    status: ground
    note: The same table prints 160 - 255 for rayon PICA IP properties.
    source: stackpoole2018
    where: Mechanical Property Comparison table, Average failure stress column, IP properties row
  - benchmark: ultimate_tensile_strength
    label: Through-thickness failure stress, Lyocell-based PICA (PICA-D), average
    value: 44
    unit: psi
    scope: material
    conditions:
      orientation: through-thickness (TTT)
      precursor: Lyocell carbon fibre (PICA-D), average
    method: Average failure stress in the Mechanical Property Comparison table of the NASA Ames slides; the slides do not name the test standard
    status: ground
    note: The same table prints 43 to 54 for rayon PICA TTT properties.
    source: stackpoole2018
    where: Mechanical Property Comparison table, Average failure stress column, TTT properties row
  - benchmark: centerline_recession
    label: Average centerline recession, Lyocell-derived PICA, arc-jet at 1550W/cm2 and 1.3 atm
    value: 4
    unit: mm
    scope: material
    conditions:
      heat_flux: 1550W/cm2
      pressure: 1.3 atm
      atmosphere: air (runs in air, 2017)
      precursor: Lyocell (PICA-D)
    method: Average centerline recession of arc-jet runs, as tabulated on the NASA Ames slides; the exposure time is not printed on the slide
    status: ground
    note: Rayon-derived PICA at the same condition is a separate row.
    source: ellerby2019
    where: PICA-D Arc Jet Testing, Recession Comparison table, Lyocell PICA row, first column
  - benchmark: centerline_recession
    label: Average centerline recession, rayon-derived PICA, arc-jet at 1550W/cm2 and 1.3 atm
    value: 4.2
    unit: mm
    scope: material
    conditions:
      heat_flux: 1550W/cm2
      pressure: 1.3 atm
      atmosphere: air (runs in air, 2017)
      precursor: heritage rayon
    method: Average centerline recession of arc-jet runs, as tabulated on the NASA Ames slides; the exposure time is not printed on the slide
    status: ground
    note: Lyocell-derived PICA at the same condition is a separate row.
    source: ellerby2019
    where: PICA-D Arc Jet Testing, Recession Comparison table, Rayon PICA row, first column
corrosion:
  - environment: Arc-jet aerothermal heating, the test conditions in Milos and Chen (2009)
    headline: In two arc-jet conditions, centerline recession was 2.33 mm at 55 s and 24.72 mm at 400 s.
    effect: Recession is the depth of surface material removed. The two rows come from different test conditions, and the heat flux for each condition is not legible in the extracted text, so the two rows are not a rate for PICA. The maximum surface temperature was 2033 K at 55 s and 2196 K at 400 s.
    rating: moderate
    conditions:
      test: arc-jet tests of PICA models
      heat_flux: not read for each condition
      data: Table 4 of the paper
    source: milos2009
    where: Table 4 (test conditions, centerline recession and maximum temperature)
  - environment: Heating of the phenolic resin to about 1250 K under argon (pyrolysis)
    headline: About 0.63 of the phenolic resin mass remains as char after pyrolysis (printed value, unit not stated).
    effect: The 1998 report uses this char yield for the phenolic resin in PICA. It gives 0.60 for the silicone resin in SIRCA, the silicone-impregnated ceramic ablator the report also tests.
    rating: low
    conditions:
      atmosphere: argon gas flow
      temperature: about 1250 K in a tube furnace
      material: phenolic resin in PICA
    source: selvaduray1998
    where: Charring paragraph, char yield V
risks:
  hazards:
    - text: Phenol, the monomer used to make phenolic resins, is classed in PubChem's aggregated GHS record (ECHA C&L notifications) as toxic if swallowed (H301), toxic in contact with skin (H311), causing severe skin burns and eye damage (H314), toxic if inhaled (H331), suspected of causing genetic defects (H341), and causing damage to organs through prolonged or repeated exposure (H373). Serious eye damage (H318) and toxicity to aquatic life (H411) appear in some notifications. This is a different substance from the phenolic resin in PICA (Durite SC-1008, per Selvaduray and Cox 1998). No safety data sheet for PICA or for that resin was read in this run, so this entry describes phenol only.
      ghs:
        - H301
        - H311
        - H314
        - H318
        - H331
        - H341
        - H373
        - H411
      source: pubchem-phenol
      where: GHS Classification section, aggregated ECHA C&L data (CID 996)
  failure_risks:
    - mode: Surface recession beyond the design depth
      trigger: Arc-jet exposure of 400 s in test condition 2b (Milos and Chen 2009, Table 4)
      consequence: Centerline recession of 24.72 mm and a maximum surface temperature of 2196 K in that test.
      severity: moderate
      source: milos2009
      where: Table 4, condition 2b
  side_effects: []
  handling: []
  mitigations: []
uses:
  - application: heat-shields
    device: Stardust sample-return capsule forebody heat shield
    example: PICA was selected as the forebody heat shield for the Stardust Discovery Class Mission, which launched in February 1999 and was to re-enter at 16 Km/sec.
    source: tpsx-pica
    where: Description (summary) on the TPSX Material page
  - application: heat-shields
    device: OSIRIS-REx sample-return capsule heat shield
    example: Gasch et al. (2019) report that OSIRIS-REx uses a single-piece PICA heat shield very similar to the Stardust design.
    source: gasch2019
    where: Introduction
  - application: heat-shields
    device: Mars Science Laboratory and Mars 2020 entry heat shields (tiled)
    example: PICA was used as the Mars Science Laboratory heat shield in a tiled configuration, and the Mars 2020 heat shield design follows that layout with PICA in a tiled arrangement.
    source: gasch2019
    where: Introduction
  - application: heat-shields
    device: Orion Crew Module heat shield (candidate)
    example: Milos and Chen (2009) describe PICA as a candidate heat shield material for the Orion Crew Module, and the Orion program tested newly manufactured PICA.
    source: milos2009
    where: Abstract and Section II (Material Properties)
supply:
  - subject: Rayon-based carbon precursor for the FiberForm preform
    producers: []
    note: Fiber Materials Inc. (Biddeford, Maine) makes FiberForm and PICA. No production share by country was found in the sources read.
    critical_lists: []
    recycling: Not found in any source we hold.
    substitutes:
      - Lyocell-based PICA (PICA-D) is in development as a domestic replacement for rayon (Gasch et al. 2019).
    source: gasch2019
    where: Introduction, paragraphs on the supply chain issues and the PICA-D development plan. The rayon supply has been replaced at least twice in the past 25 years.
  - subject: Rayon and Lyocell carbon-fibre precursors for PICA
    producers: []
    note: Lenzing makes the Lyocell precursor at sister plants in the US, Austria and UK, which the slides call multiple supply routes. Heritage rayon came from Liberty (US, production ceased in the 1990s) and from Sniace (an international source, production ceased in about 2017). Mars 2020 uses the last of the heritage Sniace rayon-based PICA.
    critical_lists: []
    recycling: Not found in any source we hold.
    substitutes:
      - Lyocell-based PICA (PICA-D) is the domestic replacement for rayon, with Lenzing as the precursor supplier (Ellerby et al. 2019).
    source: ellerby2019
    where: Challenges with PICA Sustainability table (slide 4) and the Lyocell supply slide
media: []
documents:
  - title: 'NASA Ames Thermal Protection Materials Database (TPSX): PICA [virgin], Material id 43'
    type: database
    url: https://tpsx.arc.nasa.gov/Material?id=43
    year: 2006
  - title: Ablation and Thermal Response Property Model Validation for Phenolic Impregnated Carbon Ablator (AIAA-2009-0262)
    type: paper
    url: https://ntrs.nasa.gov/api/citations/20110012891/downloads/20110012891.pdf
    year: 2009
  - title: Development of Domestic Lyocell Based Phenolic Impregnated Carbon Ablator (PICA-D) for Future NASA Missions
    type: report
    url: https://ntrs.nasa.gov/api/citations/20190031963/downloads/20190031963.pdf
    year: 2019
  - title: Thermal Protection Materials Development, 1997-1998 Annual Report (NASA/CR 208331)
    type: report
    url: https://ntrs.nasa.gov/api/citations/19980235586/downloads/19980235586.pdf
    year: 1998
  - title: Sustaining PICA TPS for Future NASA Robotic Science Missions (slides)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20180006865/downloads/20180006865.pdf
    year: 2018
  - title: Sustaining Phenolic Impregnated Carbon Ablator (PICA) for Future NASA Missions Including Discovery and New Frontiers (IPPW 2019 slides)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20190028929/downloads/20190028929.pdf
    year: 2019
  - title: PubChem compound summary, phenol (CID 996), GHS Classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/996
gaps:
  - No flight-measured recession, surface temperature or in-flight data for PICA was found in the sources read; all recession and temperature values are arc-jet ground tests.
  - The heat flux for each Milos and Chen (2009) Table 4 condition is not legible in the extracted text (Table 2 is garbled), so the recession rows give no heat flux.
  - The Gasch et al. (2019) PICA-D tension, compression, shear, CTE and conductivity results are in figures only; no numbers were read from text, so none are listed.
  - Virgin PICA gas permeability values in the 1998 report are garbled by OCR in the extracted text, so none are listed.
  - No safety data sheet or PubChem GHS record for PICA itself was read in this run. The only hazard entry is for phenol, the monomer of phenolic resins, from PubChem; it is not the Durite SC-1008 resin used in PICA, and no SDS for that resin was read.
  - The Ellerby et al. (2019) recession rows are arc-jet runs in air; the slide does not print the exposure time, so they are not a recession rate.
  - No handling, storage or workplace guidance for PICA was read in this run.
  - No humidity, UV, heat-ageing or radiation data for PICA was found in the sources read.
  - No production share by country and no critical-mineral list status was found for the rayon precursor or FiberForm; the supply entry gives producers only by name.
  - No licensed image was fetched, so the media list is empty.
  - Eight sources are now read. The Stackpoole 2008 Stardust post-flight paper and the Tran 1994 and 1996 PICA papers were cited by the sources but not opened.
  - The TPSX reference page (Reference id 74) returned HTTP 404, and a Wikipedia article for PICA does not exist, so neither was used.
  - The NASA Stardust mission page does not mention PICA, and no value in this profile is taken from it. The NASA MSL page does not mention the heat shield.
  - Orion candidate status comes from a 2009 paper; no current status was found.
  - 'TPSX values read in this run but removed from properties: the value check cannot match the exponent notation the page prints, so they are kept here as printed. Density 2.36e+02 kg/m^3 (uncertainty 12.0, no unit printed); thermal conductivity 3.05e-01 W/m-K (labelled isotropic, temperature not printed; Milos and Chen 2009 call PICA strongly orthotropic); effective heat of ablation 1.15e+08 J/kg (uncertainty 5.77e+06, no unit printed; description ties it to heat fluxes of 300 to 1500 W/sqcm); pyrolysis gas enthalpy -9.02e+06 J/kg; tensile strength 1.34e+06 Pa in-plane and 2.41e+05 Pa through-thickness; tensile modulus 1.10e+08 Pa in-plane and 2.36e+07 Pa through-thickness; tensile strain to failure 1.20e-03 m/m in-plane and 8.50e-03 m/m through-thickness; volume fraction of resin 6.46e-02.'
  - 'Property names not in spores/property-canon.yaml and used here: emissivity, char_yield, centerline_recession and max_surface_temperature.'
  - The TPSX page prints no temperature for its specific heat and emissivity values.
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 18
  unreachable: 1
  caveats: 2
  note: Read by an AI assistant on 2026-11-01 from the TPSX page (raw HTML checked against the WebFetch summary) and three NASA PDFs (text-extracted with pdftotext). The value check could not match 11 TPSX values printed in exponent notation, so they are listed in gaps rather than in properties. One TPSX reference page returned 404 and was not used.
story:
  recipe:
    line: 'PICA is a composite of two parts: a rigid, low-density carbon-fibre preform (FiberForm) and a phenolic resin that fills the open space in the preform. The carbon fibres are made from rayon by a high-temperature conversion, and the preform is infused with phenolic resin and then cured (Gasch et al. 2019; Selvaduray and Cox 1998).'
    parts:
      - name: Carbon-fibre preform (FiberForm)
        symbol: '-'
        share: The rest of the volume after the phenolic resin share (TPSX)
        role: A rigid, porous carbon substrate made from chopped rayon-derived carbon fibres. It sets the low density and the open pore structure.
      - name: Phenolic resin (Durite SC-1008)
        symbol: '-'
        share: Volume share of phenolic resin (TPSX)
        role: Fills the void space between filaments. On heating it decomposes, and the char it leaves behind is what protects the surface.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not assessed in this run
      lead: No safety data sheet or PubChem GHS entry for PICA itself was read, so this group has no verdict.
      points:
        - label: Gap
          line: The supplier safety data sheet and the PubChem record for PICA were not read in this run. The phenolic resin in PICA is a different product.
    - title: If the heat shield ablates
      lead: 'Ablation is the design mechanism: the surface material is removed in a controlled way. The sources give these values from arc-jet tests, not from flight.'
      points:
        - label: Recession at 55 s
          line: In arc-jet test condition 1 of Milos and Chen (2009), a model recessed 2.33 mm in 55 s, with a maximum surface temperature of 2033 K. A second model under the same condition recessed 2.27 mm.
        - label: Recession at 400 s
          line: In arc-jet test condition 2b, a model recessed 24.72 mm in 400 s, with a maximum surface temperature of 2196 K. The heat flux for each condition is not legible in the extracted text.
    - title: Handling and storage
      lead: Only test-model preparation is documented in the sources read.
      points:
        - label: Test models
          line: In the arc-jet models, the exposed surface was machined, and the unexposed PICA surfaces were sealed or bonded to adjacent parts (Milos and Chen 2009).
  why: Phenolic Impregnated Carbon Ablator (PICA) is a low-density ablative heat shield developed at NASA Ames Research Center. The sources call it the lowest-density carbon-phenolic ablator with flight heritage (Gasch et al. 2019). It is made by infusing a rigid carbon-fibre preform with phenolic resin. Its density and ablation values come from NASA's TPSX database and from NASA papers, and this profile uses only the numbers printed in those sources.
  uses:
    - where: Stardust (launched 1999)
      line: PICA was the forebody heat shield of Stardust, the first sample-return mission from outside the Earth-Moon system. The TPSX database says Stardust was to re-enter at 16 Km/sec, and Gasch et al. describe the heat shield as a single cast piece.
    - where: OSIRIS-REx
      line: Gasch et al. report that OSIRIS-REx uses a single-piece PICA heat shield very similar to the Stardust design.
    - where: Mars Science Laboratory and Mars 2020 (tiled)
      line: PICA was used on Mars Science Laboratory in a tiled layout, and the Mars 2020 heat shield follows that layout (Gasch et al. 2019).
    - where: Orion Crew Module (candidate)
      line: Milos and Chen (2009) call PICA a candidate heat shield material for the Orion Crew Module. The program tested newly manufactured PICA.
  can_do:
    - label: Density
      benchmark: density
      line: The 1998 NASA annual report gives a nominal density of 224 to 248 kg/m^3 for PICA, depending on the phenolic loading. The FiberForm substrate before impregnation is 144 to 176 kg/m^3 in the same report.
    - label: Emissivity
      benchmark: emissivity
      value: '0.8'
      line: TPSX lists an emissivity of 0.8 for virgin PICA. Its source column says measured, and the page gives no temperature for it.
    - label: Specific heat
      benchmark: specific_heat
      value: 1200 J/kg-K
      line: TPSX lists a specific heat of 1200 J/kg-K for virgin PICA. The page gives no temperature, and its source column says unknown.
    - label: Char
      benchmark: char_yield
      line: The phenolic resin in PICA leaves about 0.63 of its mass as char after pyrolysis at about 1250 K under argon (Selvaduray and Cox 1998). The report does not say whether 0.63 is a fraction or a percent.
  compare: No other thermal-protection profile was read in this run, so this paragraph gives no side-by-side number. Within the sources read, PICA is described as the lowest-density carbon-phenolic ablator with flight heritage (Gasch et al. 2019). Its nominal density is 224 to 248 kg/m^3 and its arc-jet recession grows strongly with exposure time (2.33 mm at 55 s, 24.72 mm at 400 s, in different conditions). For a like-for-like table, read the other ablator profiles with the same method.
  compare_rows:
    - label: Density, nominal PICA
      benchmark: density
    - label: Specific heat, virgin PICA
      benchmark: specific_heat
    - label: Char yield of phenolic resin
      benchmark: char_yield
  handling:
    - 'Handle as a composite. The sources document only the test-model preparation: the exposed face was machined, and other faces were sealed or bonded.'
    - No storage or workplace handling guidance for PICA was read in this run.
    - Plan for the precursor supply. The rayon source has been replaced at least twice in the past 25 years (Gasch et al. 2019).
  good_for:
    - 'Entry heat shields that need a light carbon-phenolic ablator with flight heritage: Stardust, and Mars Science Laboratory in tiled form.'
    - 'Designs that need a NASA property set: TPSX gives density, specific heat, emissivity and effective heat of ablation for virgin PICA.'
  watch_out:
    - 'Density depends on phenolic loading: 224 to 248 kg/m^3 nominal in the 1998 report.'
    - TPSX labels the conductivity isotropic, but Milos and Chen (2009) describe it as strongly orthotropic.
    - 'Recession is large at long exposures: 24.72 mm after 400 s in one arc-jet condition.'
    - The rayon precursor supply has changed at least twice in the past 25 years, and the Lyocell replacement (PICA-D) is still in development.
  verdict: PICA is a flight-proven carbon-phenolic heat shield with NASA property values for virgin material. What the sources read here do not give is hazard data, ageing and humidity behaviour, in-flight measurements, or a settled precursor supply.
sources:
  tpsx-pica:
    title: 'NASA Ames Thermal Protection Materials Database (TPSX): PICA [virgin], Material id 43'
    id: TPSX Material id 43; manufacturer Fiber Materials Inc.; point of contact F.S. Milos
    url: https://tpsx.arc.nasa.gov/Material?id=43
    year: 2006
    kind: database
    license: NASA public database (cited, not reproduced)
  milos2009:
    title: Ablation and Thermal Response Property Model Validation for Phenolic Impregnated Carbon Ablator
    id: AIAA-2009-0262 (47th AIAA Aerospace Sciences Meeting); NTRS 20110012891; F.S. Milos and Y.-K. Chen, NASA Ames
    url: https://ntrs.nasa.gov/api/citations/20110012891/downloads/20110012891.pdf
    year: 2009
    kind: paper
    license: NASA NTRS public record (cited, not reproduced)
  gasch2019:
    title: Development of Domestic Lyocell Based Phenolic Impregnated Carbon Ablator (PICA-D) for Future NASA Missions
    id: NTRS 20190031963; M. Gasch et al., NASA Ames and Fiber Materials Inc.
    url: https://ntrs.nasa.gov/api/citations/20190031963/downloads/20190031963.pdf
    year: 2019
    kind: report
    license: NASA NTRS public record (cited, not reproduced)
  selvaduray1998:
    title: Thermal Protection Materials Development, 1997-1998 Annual Report
    id: NASA/CR 208331; NTRS 19980235586; G. Selvaduray and M. Cox, San Jose State University
    url: https://ntrs.nasa.gov/api/citations/19980235586/downloads/19980235586.pdf
    year: 1998
    kind: report
    license: NASA NTRS public record (cited, not reproduced)
  nasa-stardust:
    title: 'NASA Science: Stardust mission page'
    id: science.nasa.gov/mission/stardust
    url: https://science.nasa.gov/mission/stardust/
    year: 2026
    kind: web
    license: NASA web page (cited, not reproduced)
  stackpoole2018:
    title: Sustaining PICA TPS for Future NASA Robotic Science Missions (slides)
    id: NTRS 20180006865; M. Stackpoole, E. Venkatapathy and M. Gasch, NASA Ames; S. Violette, Fiber Materials Inc.
    url: https://ntrs.nasa.gov/api/citations/20180006865/downloads/20180006865.pdf
    year: 2018
    kind: report
    license: NASA NTRS public record (cited, not reproduced)
  ellerby2019:
    title: Sustaining Phenolic Impregnated Carbon Ablator (PICA) for Future NASA Missions Including Discovery and New Frontiers
    id: NTRS 20190028929; International Planetary Probe Workshop, 2019; D. Ellerby et al., NASA Ames
    url: https://ntrs.nasa.gov/api/citations/20190028929/downloads/20190028929.pdf
    year: 2019
    kind: report
    license: NASA NTRS public record (cited, not reproduced)
  pubchem-phenol:
    title: PubChem compound summary, phenol (CID 996), GHS Classification
    id: PubChem CID 996
    url: https://pubchem.ncbi.nlm.nih.gov/compound/996
    kind: database
    license: PubChem public record (cited, not reproduced)