spore: profile
id: regolith-polymer-composite
spore_version: 0.2
family: regolith-polymer composite
name: Regolith-polymer composite (80:20 LHS-1 lunar highlands simulant with PLA, fused-filament printed)
abbreviation: RPC
role: Printed structural building material made from regolith simulant and a bio-based polymer binder
category: regolith
type: lunar-concrete
summary: |
  Regolith-polymer composite (RPC) is lunar highlands simulant LHS-1 mixed with polylactic acid (PLA) and printed layer by layer. In NASA's REACT tests, the 80:20 LHS-1:PLA blend reached 24 MPa flexural strength at 0 degrees and 16.6 MPa at 90 degrees in one independent laboratory's tests at ambient temperature. The project describes the material as approaching technology readiness level 5, and long-term lunar exposure is still untested.
best_for: Ground demonstrations of printed lunar shelter parts made from regolith simulant and a bio-based binder
weakest_at: Strength across the print layers, and untested long-term exposure to lunar vacuum, thermal cycling and UV
identity:
  formula: 80:20 wt.% LHS-1 lunar highlands simulant and polylactic acid, (C3H4O2)n; a composite, not a single compound
  source: nasa-ntrs-2023
  where: Title and author record on the NTRS citation page 20230015024; mixture ratio from the Abstract and Table 4 of the paper (nasa-strives)
tags:
  environments:
    - lunar-day
    - lunar-night
  stresses:
    - thermal-cycling
    - vacuum-and-outgassing
    - uv
    - micrometeoroids-and-debris
  applications:
    - structures
    - in-space-manufacturing
properties:
  - benchmark: flexural_strength
    label: Flexural strength, 0 degrees, independent laboratory
    value: 24
    unit: MPa
    scope: material
    conditions:
      composition: 80:20 wt.% LHS-1:PLA (the Beta material selected by the paper)
      orientation: 0 degrees, as the paper labels it
      test_environment: ambient temperature, per the paper
      tested_by: independent laboratory, not named in Table 4
    method: Table 4 average of 24 MPa with standard deviation 3 MPa, testing by an independent laboratory; the paper labels the test as flexural strength at 0 degrees
    status: ground
    source: nasa-strives
    where: Table 4 (Summary of the Selected Beta Material), Flexural Strength (MPa), 0 degrees column
  - benchmark: flexural_strength
    label: Flexural strength, 90 degrees, independent laboratory
    value: 16.6
    unit: MPa
    scope: material
    conditions:
      composition: 80:20 wt.% LHS-1:PLA (the Beta material selected by the paper)
      orientation: 90 degrees, across the print direction
      test_environment: ambient temperature, per the paper
      tested_by: independent laboratory, not named in Table 4
    method: Table 4 average of 16.6 MPa with standard deviation 0.8 MPa, independent laboratory
    status: ground
    source: nasa-strives
    where: Table 4, Flexural Strength (MPa), 90 degrees column
  - benchmark: flexural_modulus
    label: Flexural modulus, 0 degrees, independent laboratory
    value: 5.3
    unit: GPa
    scope: material
    conditions:
      composition: 80:20 wt.% LHS-1:PLA
      orientation: 0 degrees
      test_environment: ambient temperature, per the paper
      tested_by: independent laboratory, not named in Table 4
    method: Table 4 average of 5.3 GPa with standard deviation 0.2 GPa, independent laboratory
    status: ground
    source: nasa-strives
    where: Table 4, Flexural Modulus (GPa), 0 degrees column
  - benchmark: flexural_modulus
    label: Flexural modulus, 90 degrees, independent laboratory
    value: 3.7
    unit: GPa
    scope: material
    conditions:
      composition: 80:20 wt.% LHS-1:PLA
      orientation: 90 degrees, across the print direction
      test_environment: ambient temperature, per the paper
      tested_by: independent laboratory, not named in Table 4
    method: Table 4 average of 3.7 GPa with standard deviation 0.6 GPa, independent laboratory
    status: ground
    source: nasa-strives
    where: Table 4, Flexural Modulus (GPa), 90 degrees column
  - benchmark: flexural_strength
    label: Flexural strength, 0 degrees, SpaceFactory testing
    value: 34.4
    unit: MPa
    scope: material
    conditions:
      composition: 80:20 LHS-1/PLA
      orientation: 0 degrees, as the paper labels it
      tested_by: SpaceFactory, the project partner that printed the samples
    method: Average of 34.40 MPa in Table 3 (SpaceFactory testing); the paper reports these values above the independent laboratory's results and gives both sets side by side
    status: ground
    source: nasa-strives
    where: Table 3 (Summary of the material testing results performed at SpaceFactory), row 80/20 LHS-1/PLA 0 degrees, Avg Ultimate Flexural Strength (MPa)
  - benchmark: flexural_strength
    label: Flexural strength, 90 degrees, SpaceFactory testing
    value: 14.9
    unit: MPa
    scope: material
    conditions:
      composition: 80:20 LHS-1/PLA
      orientation: 90 degrees, across the print direction
      tested_by: SpaceFactory, the project partner that printed the samples
    method: Average of 14.90 MPa in Table 3 (SpaceFactory testing)
    status: ground
    source: nasa-strives
    where: Table 3, row 80/20 LHS-1/PLA 90 degrees, Avg Ultimate Flexural Strength (MPa)
  - benchmark: flexural_modulus
    label: Flexural modulus, 0 degrees, SpaceFactory testing
    value: 7.43
    unit: GPa
    scope: material
    conditions:
      composition: 80:20 LHS-1/PLA
      orientation: 0 degrees, as the paper labels it
      tested_by: SpaceFactory, the project partner that printed the samples
    method: Table 3 average of 7.43 GPa (SpaceFactory testing)
    status: ground
    source: nasa-strives
    where: Table 3, row 80/20 LHS-1/PLA 0 degrees, Avg Flexural Modulus (GPa)
  - benchmark: flexural_modulus
    label: Flexural modulus, 90 degrees, SpaceFactory testing
    value: 3.68
    unit: GPa
    scope: material
    conditions:
      composition: 80:20 LHS-1/PLA
      orientation: 90 degrees, across the print direction
      tested_by: SpaceFactory, the project partner that printed the samples
    method: Table 3 average of 3.68 GPa (SpaceFactory testing)
    status: ground
    source: nasa-strives
    where: Table 3, row 80/20 LHS-1/PLA 90 degrees, Avg Flexural Modulus (GPa)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, 0 degrees, independent laboratory
    value: 15.2
    unit: MPa
    scope: material
    conditions:
      composition: 80:20 wt.% LHS-1:PLA
      orientation: 0 degrees
      test_environment: ambient temperature, per the paper
      tested_by: independent laboratory, not named in Table 4
    method: Table 4 average of 15.2 MPa with standard deviation 0.3 MPa, independent laboratory
    status: ground
    source: nasa-strives
    where: Table 4, Tensile Strength (MPa), 0 degrees column
  - benchmark: elastic_modulus
    label: Tensile modulus, 0 degrees, independent laboratory
    value: 7
    unit: GPa
    scope: material
    conditions:
      composition: 80:20 wt.% LHS-1:PLA
      orientation: 0 degrees
      test_environment: ambient temperature, per the paper
      tested_by: independent laboratory, not named in Table 4
    method: Table 4 average of 7.0 GPa with standard deviation 0.4 GPa, independent laboratory
    status: ground
    source: nasa-strives
    where: Table 4, Tensile Modulus (GPa), 0 degrees column
  - benchmark: compressive_strength
    label: Compressive strength, 0 degrees, independent laboratory
    value: 50
    unit: MPa
    scope: material
    conditions:
      composition: 80:20 wt.% LHS-1:PLA
      orientation: 0 degrees
      test_environment: ambient temperature, per the paper
      tested_by: independent laboratory, not named in Table 4
    method: Table 4 average of 50 MPa with standard deviation 2 MPa, independent laboratory
    status: ground
    source: nasa-strives
    where: Table 4, Compression Strength (MPa), 0 degrees column
  - benchmark: density
    label: Density, pellets, volumetric displacement
    value: 1.8
    unit: g/cc
    scope: material
    conditions:
      form: compounded pellets of 80:20 LHS-1:PLA
      method_detail: volumetric displacement, which the paper prefers over gas pycnometry for this material
    method: Table 6 pellet displacement density printed as 1.80 g/cc for 80:20 LHS-1:PLA; the paper says 1.80 g/cc was used for LINA structural design
    status: ground
    source: nasa-strives
    where: 'Table 6, 80:20 LHS-1: PLA row, Pellet Densities, Disp. column'
  - benchmark: density
    label: Density, ambient print, volumetric displacement
    value: 1.82
    unit: g/cc
    scope: material
    conditions:
      form: printed in ambient conditions, 80:20 LHS-1:PLA
      method_detail: volumetric displacement
    method: Table 6 ambient print displacement density printed as 1.82 g/cc
    status: ground
    source: nasa-strives
    where: 'Table 6, 80:20 LHS-1: PLA row, Ambient Print Densities, Disp. column'
  - benchmark: density
    label: Density, pure PLA pellets, volumetric displacement (comparison only)
    value: 1.28
    unit: g/cc
    scope: material
    conditions:
      material: pure PLA, the binder alone, with no regolith
      form: pellets
      method_detail: volumetric displacement
    method: Table 6 Pure PLA row, pellet displacement density printed as 1.28 g/cc; a comparison value for the binder, not a value for the composite
    status: ground
    source: nasa-strives
    where: Table 6, Pure PLA row, Pellet Densities, Disp. column
  - benchmark: porosity
    label: Porosity, pellets, calculated from displacement density
    value: 13.8
    unit: '%'
    scope: material
    conditions:
      form: compounded pellets, 80:20 LHS-1:PLA
      basis: calculated from displacement density and TGA mass fractions
    method: Calculated by the paper from displacement density and mass fractions (Table 7)
    status: calculated
    source: nasa-strives
    where: 'Table 7, 80:20 LHS-1: PLA row, Pellet Porosity (%)'
  - benchmark: porosity
    label: Porosity, ambient print, calculated from displacement density
    value: 15.1
    unit: '%'
    scope: material
    conditions:
      form: printed in ambient conditions, 80:20 LHS-1:PLA
      basis: calculated from displacement density and TGA mass fractions
    method: Calculated by the paper from displacement density and mass fractions (Table 7)
    status: calculated
    source: nasa-strives
    where: 'Table 7, 80:20 LHS-1: PLA row, Ambient Print Porosity (%)'
  - benchmark: porosity
    label: Porosity, TVAC print, calculated from pycnometer density
    value: 8.8
    unit: '%'
    scope: material
    conditions:
      form: printed in simulated lunar dirty thermal vacuum, 80:20 LHS-1:PLA
      basis: calculated from pycnometer data
    method: 'Table 7 footnote: calculated from pycnometer data because displacement density was not available for this sample'
    status: calculated
    note: Calculated from a different density method than the other two porosity rows, so the three values are not directly comparable.
    source: nasa-strives
    where: 'Table 7, 80:20 LHS-1: PLA row, TVAC Print Porosity (%), footnote marked with an asterisk'
  - benchmark: porosity
    label: Porosity, ambient print, X-ray CT scan
    value: 0.76
    unit: '%'
    scope: material
    conditions:
      form: printed in ambient conditions, 80:20 LHS-1:PLA
      basis: CT-scan reconstruction
    method: CT-scan porosity from Table 7; the paper says the true porosity lies between the calculated and CT-scan values, and that CT-scan values are likely an underestimate
    status: ground
    source: nasa-strives
    where: 'Table 7, 80:20 LHS-1: PLA row, Ambient Print CT-Scan Porosity (%)'
  - benchmark: porosity
    label: Porosity, TVAC print, X-ray CT scan
    value: 1.24
    unit: '%'
    scope: material
    conditions:
      form: printed in simulated lunar dirty thermal vacuum, 80:20 LHS-1:PLA
      basis: CT-scan reconstruction
    method: CT-scan porosity from Table 7; the paper says the true porosity lies between the calculated and CT-scan values
    status: ground
    source: nasa-strives
    where: 'Table 7, 80:20 LHS-1: PLA row, TVAC Print CT-Scan Porosity (%)'
  - benchmark: ultimate_tensile_strength
    label: Tensile strength of pure PLA at 77 K (cryogenic, comparison only)
    value: 87
    unit: MPa
    scope: material
    conditions:
      material: pure PLA, the binder alone, with no regolith
      temperature: 77 K
    method: Value stated in the paper's polymer comparison text; the paper does not give a cryogenic strength for the composite
    status: ground
    source: nasa-strives
    where: Polymer evaluation text, PLA paragraph (statement on cryogenic tensile strength)
  - benchmark: elongation
    label: Elongation of pure PLA at 77 K (cryogenic, comparison only)
    value: 5.7
    unit: '%'
    scope: material
    conditions:
      material: pure PLA, the binder alone, with no regolith
      temperature: 77 K
    method: Value stated in the paper's polymer comparison text, with 6.4 percent at room temperature for the same polymer; not a value for the composite
    status: ground
    source: nasa-strives
    where: Polymer evaluation text, PLA paragraph (elongation statement)
corrosion:
  - environment: Lunar vacuum, outgassing and mass loss
    headline: Mass loss from outgassing has not been measured for the composite.
    effect: The paper lists vacuum mass loss as a remaining test. During vacuum printing, the residual gas analyser showed mostly air peaks and the paper reports no substantial off-gassing, but this is a printing-time check and not a long-term lunar exposure test.
    rating: unknown
    conditions:
      exposure: vacuum printing in simulated lunar dirty thermal vacuum
      test: residual gas analyser during printing of 85:15 BP-1:PLA and 80:20 LHS-1:PLA cubes
    source: nasa-strives
    where: Vacuum Off-Gassing Characterization section and Conclusions
  - environment: Thermal cycling across the lunar temperature range
    headline: Thermal fatigue has not been tested for the composite.
    effect: The REACT slides list strength across the lunar temperature range and thermal fatigue as tests still to do. The composite has not been cycled through lunar temperatures in any source held.
    rating: unknown
    conditions:
      status: not tested
    source: nasa-react
    where: Slide 20, Conclusions (remaining tests)
  - environment: Ultraviolet exposure on the lunar surface
    headline: UV degradation is named as a risk and has not been tested.
    effect: The paper says exposure to the Moon's environment can limit the useful life of the composite through thermal cycling fatigue, mass loss from outgassing and UV degradation, and that further testing is needed.
    rating: unknown
    conditions:
      exposure: lunar surface, long-term
      test: no UV test reported
    source: nasa-strives
    where: Conclusions and Recommendations, lifecycle paragraph
  - environment: Moisture during extrusion, and sunlight heat
    headline: PLA absorbs moisture and has a low heat distortion temperature, which the paper says limits it.
    effect: The paper says PLA absorbs moisture, which may hydrolyze during extrusion and reduce mechanical properties, and that vacuum on the Moon mitigates this. It also says PLA has a low heat distortion temperature that would limit performance in direct sunlight.
    rating: moderate
    conditions:
      basis: qualitative statement about PLA in the paper, not a test of the composite
    source: nasa-strives
    where: Polymer evaluation text, PLA paragraph
risks:
  hazards:
    - text: The PLA datasheet describes Ingeo biopolymers as having very low toxicity in normal use, but says handling can generate vapours and dusts that irritate the eyes and upper airways, and advises an approved dust respirator in dusty air.
      ghs: []
      source: nw-3d850
      where: Safety and Handling Considerations, Hazards and Handling Precautions
    - text: The datasheet says dust layers can ignite, and dust suspended in air can pose an explosion hazard.
      ghs: []
      source: nw-3d850
      where: Hazards and Handling Precautions, Combustibility
    - text: The datasheet says that at melt temperature polymer can release fumes, and that for polyesters such as PLA, thermal decomposition can produce flammable vapours containing acetaldehyde and carbon monoxide.
      ghs: []
      source: nw-3d850
      where: Safety and Handling Considerations (decomposition paragraph)
    - text: The paper gives no hazard classification for the composite, and no safety data sheet for the composite was found in the sources held.
      ghs: []
      source: nasa-strives
      where: Full text read in this run; no hazard section found
  failure_risks:
    - mode: Failure along the print layers
      trigger: Loading across the printed layers, such as the 90 degree direction
      consequence: Fracture runs along layer interfaces, which the paper reads as poor adhesion between layers. The independent laboratory measured 16.6 MPa flexural strength at 90 degrees against 24 MPa at 0 degrees.
      severity: moderate
      source: nasa-strives
      where: Table 4; Microscopy section (fracture surfaces)
    - mode: Porosity from the extrusion process
      trigger: Printing with the extruder in simulated lunar dirty thermal vacuum
      consequence: Calculated porosity ranges from 8.8 to 15.1 percent depending on the method used. The paper says porosity is concentrated at layer interfaces and comes from extrusion more than from the printing environment.
      severity: moderate
      source: nasa-strives
      where: Table 7; Porosity Characterization; Conclusions
  side_effects:
    - text: During vacuum printing, the residual gas analyser showed mostly air peaks (nitrogen, oxygen, carbon dioxide and water). The paper reports no substantial off-gassing from the material.
      affects: Vacuum chamber and hardware in the printing environment
      source: nasa-strives
      where: Vacuum Off-Gassing Characterization
  handling:
    - text: Keep dust down with good housekeeping and dust control when handling PLA pellets, because dust layers can ignite.
      source: nw-3d850
      where: Hazards and Handling Precautions; Combustibility
    - text: Use an approved dust respirator in dusty atmospheres.
      source: nw-3d850
      where: Hazards and Handling Precautions
    - text: Provide good general ventilation of the polymer processing area, since fumes can be released at melt temperature.
      source: nw-3d850
      where: Safety and Handling Considerations
    - text: Dry the PLA before compounding, as the paper did, because PLA absorbs moisture.
      source: nasa-strives
      where: Polymer evaluation text (PLA moisture statement); Beta Materials Drying Procedure
  mitigations:
    - text: Optimise pellet extrusion and print parameters to reduce porosity, and move to single-step compounding during printing, as the paper recommends.
      source: nasa-strives
      where: Porosity Characterization; Conclusions and Recommendations
uses:
  - application: structures
    device: Lunar Infrastructure Asset (LINA), an unpressurized protective shelter printed from the composite
    example: The IEEE paper says LINA is designed to support 2.3 m of regolith overburden; a sub-scale LINA was printed on regolith simulant in dirty vacuum as the project's final test.
    source: nasa-strives
    where: Abstract; Conclusions
  - application: in-space-manufacturing
    device: Fused filament fabrication printer with a heated extruder head (ground demonstration only)
    example: The REACT team printed the composite one layer at a time in simulated lunar dirty thermal vacuum, per the IEEE paper. This is a ground demonstration; the REACT slides recommend a small CLPS demonstration mission next.
    source: wikipedia-fff
    where: Lead paragraph (FFF process definition); printing conditions from the IEEE paper (nasa-strives); CLPS recommendation on REACT slide 20 (nasa-react)
supply:
  - subject: Lunar highlands simulant LHS-1 (regolith stand-in used in tests)
    abundance: Not a mined material. LHS-1 is a commercial simulant that stands in for lunar highlands regolith in tests. The users guide names Exolith Lab at the University of Central Florida, now Space Resource Technologies, as its source.
    recycling: Not stated in the sources held.
    substitutes: []
    source: nasa-guide-2024
    where: Table 2 (LHS-1 row, Exolith Labs/Space Resource Technologies) and the text on Exolith Lab
  - subject: Polylactic acid (binder)
    abundance: The monomer is typically made from fermented plant starch, such as from corn, cassava, sugarcane or sugar beet pulp. Producer shares were not found in the sources held.
    recycling: Not stated in the sources held.
    substitutes: []
    source: wikipedia-pla
    where: Article text on the monomer feedstock
  - subject: Lunar regolith (the in-situ feedstock the composite is meant to use)
    abundance: Regolith covers almost the entire lunar surface. The composite is designed to use it as filler, but the simulant, not lunar regolith, was used in the tests.
    recycling: Not applicable.
    substitutes: []
    source: wikipedia-regolith
    where: Moon section of the article
documents:
  - title: Selection, Production, and Properties of Regolith Polymer Composites for Lunar Construction (IEEE Aerospace Conference 2024, NTRS 20230015024)
    type: paper
    url: https://ntrs.nasa.gov/citations/20230015024
    year: 2024
  - title: 'REACT: Selection, Production and Properties of Regolith Polymer Composite for Lunar Construction (slides, NTRS 20240003076)'
    type: report
    url: https://ntrs.nasa.gov/api/citations/20240003076/downloads/REACT%20Selection%20Production%20and%20STRIVES.pdf
    year: 2024
  - title: Lunar Regolith Simulant Users Guide, Rev A (NASA/TM-20240011783)
    type: report
    url: https://ntrs.nasa.gov/api/citations/20240011783/downloads/Lunar_Regolith_Simulant_Users_Guide_Rev_A_28OCT.pdf
    year: 2024
  - title: Ingeo Biopolymer 3D850 Technical Data Sheet (NatureWorks)
    type: datasheet
    url: https://www.natureworksllc.com/getContentAsset/6d5ea62c-7872-4297-aff7-67b8a53fe47f/53ffd608-340f-457b-b656-6b8cc0000bd4/TechnicalDataSheet_3D850_monofilament.pdf?language=en
gaps:
  - No flight, long-term lunar exposure or thermal-cycling result for the composite was found. The remaining tests listed by the REACT slides are strength across the lunar temperature range, thermal fatigue, vacuum mass loss, and assessment of lunar environmental impacts.
  - 'The two independent flexural data sets disagree: the paper''s text gives different 0 degree and 90 degree values for the independent laboratory from its Table 4. The table values are recorded above, both sets side by side.'
  - The composite's cryogenic strength, glass transition and heat distortion temperature were not found. The 77 K values above are for pure PLA only.
  - The achieved mixture of 75:25 by TGA (REACT slide 11) is recorded in the recipe text only; it is not a measured property row.
  - Vacuum pressures and the lunar vacuum levels quoted in the paper print as exponents, so they are not recorded here.
  - Compressive strength and porosity are not canonical benchmark names in the property list; they are kept as short snake_case names.
  - Production shares for PLA and for LHS-1 were not found in the sources held, so the supply entries name producers without country shares.
  - No PubChem GHS record or safety data sheet for the composite was found. The PubChem page could not be opened in this run (a verification challenge), so hazard data come from the PLA datasheet and the paper.
  - No CAS number, because the composite is a mixture. The formula is a description of the mixture.
  - The hazard from the regolith simulant's dust was not assessed in any source held.
  - The paper says higher-fidelity simulants with agglutinates and nanophase iron should be used later, so these results are for simulant only.
sources:
  nasa-strives:
    title: Selection, Production, and Properties of Regolith Polymer Composites for Lunar Construction (IEEE Aerospace Conference paper, NTRS 20230015024)
    id: NTRS 20230015024
    url: https://ntrs.nasa.gov/api/citations/20230015024/downloads/STRIVES%20IEEE-Selection%20Production%20and%20Prop%20FINAL.pdf
    year: 2024
    kind: paper
    license: public domain (NASA)
  nasa-react:
    title: Selection, Production and Properties of Regolith Polymer Composite for Lunar Construction (REACT slides, 2024 IEEE Aerospace Conference, NTRS 20240003076)
    id: NTRS 20240003076
    url: https://ntrs.nasa.gov/api/citations/20240003076/downloads/REACT%20Selection%20Production%20and%20STRIVES.pdf
    year: 2024
    kind: report
    license: public domain (NASA)
  nasa-guide-2024:
    title: Lunar Regolith Simulant Users Guide, Rev A (NASA/TM-20240011783)
    id: NTRS 20240011783
    url: https://ntrs.nasa.gov/api/citations/20240011783/downloads/Lunar_Regolith_Simulant_Users_Guide_Rev_A_28OCT.pdf
    year: 2024
    kind: report
    license: public domain (NASA)
  nasa-ntrs-2023:
    title: NTRS citation record 20230015024, Selection, Production, and Properties of Regolith Polymer Composites for Lunar Construction (presented at the 45th International IEEE Aerospace Conference, March 2024)
    id: NTRS 20230015024
    url: https://ntrs.nasa.gov/citations/20230015024
    year: 2024
    kind: paper
    license: public domain (NASA)
  nw-3d850:
    title: Ingeo Biopolymer 3D850 Technical Data Sheet (3D printing monofilament), NatureWorks
    url: https://www.natureworksllc.com/getContentAsset/6d5ea62c-7872-4297-aff7-67b8a53fe47f/53ffd608-340f-457b-b656-6b8cc0000bd4/TechnicalDataSheet_3D850_monofilament.pdf?language=en
    kind: datasheet
    license: supplier document, linked not reproduced
  wikipedia-pla:
    title: Polylactic acid, Wikipedia (monomer feedstock; CAS number in the identifiers section)
    id: CAS 26100-51-6
    url: https://en.wikipedia.org/wiki/Polylactic_acid
    kind: web
    license: CC BY-SA 4.0
  wikipedia-fff:
    title: Fused filament fabrication, Wikipedia (lead paragraph and process description)
    url: https://en.wikipedia.org/wiki/Fused_filament_fabrication
    kind: web
    license: CC BY-SA 4.0
  wikipedia-regolith:
    title: Regolith, Wikipedia (definition; Moon section)
    url: https://en.wikipedia.org/wiki/Regolith
    kind: web
    license: CC BY-SA 4.0
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 21
  unreachable: 0
  caveats: 2
  note: 'Written by an AI assistant on 2026-11-01 from the NASA IEEE paper (NTRS 20230015024), the REACT slides (NTRS 20240003076), the NASA simulant users guide, the NatureWorks 3D850 datasheet and two Wikipedia articles, all read in this run. Two caveats: the two flexural data sets disagree, and the porosity values come from different methods.'
story:
  recipe:
    line: Regolith-polymer composite is lunar highlands simulant LHS-1 mixed with polylactic acid (PLA) and compounded into pellets. The paper's target mix is 80:20 by weight, and the REACT slides report an achieved mix of "75:25" by TGA. Fused filament fabrication (FFF) then feeds the pellets as a filament through a heated, moving extruder head that deposits one layer at a time.
    parts:
      - name: LHS-1 lunar highlands simulant
        role: Mineral filler that stands in for lunar highlands regolith. The paper describes it as mostly anorthosite with glass-rich basalt.
        share_percent: 80
        source: nasa-strives
        where: Target mix 80:20 wt.% (Table 4); simulant description in the Comparative Analysis section
      - name: Polylactic acid
        symbol: (C3H4O2)n
        role: Thermoplastic binder that holds the simulant particles together and flows through the extruder. It is a bio-based polyester.
        share_percent: 20
        source: nasa-strives
        where: Target mix 80:20 wt.% (Table 4)
  risk_groups:
    - title: For people
      level: 1
      verdict: Low toxicity, but dust needs control
      lead: No hazard classification for the composite appears in the sources held. The PLA datasheet describes low toxicity, with dust and fume precautions.
      points:
        - label: Dust
          line: Handling can release dust and vapours that irritate the eyes and upper airways. The datasheet advises an approved dust respirator in dusty air, and says suspended dust can be an explosion hazard.
        - label: Heating
          line: At melt temperature, PLA can release fumes. Long holds at high temperature can decompose it into flammable vapours containing acetaldehyde and carbon monoxide.
        - label: Regolith dust
          line: The regolith simulant's dust was not assessed in any source held, so its respiratory effect is not known from this record.
    - title: Failure in service
      level: 2
      verdict: Weaker across print layers
      lead: The strength results come from small test specimens, not full shelters.
      points:
        - label: Layers
          line: Fracture follows the layer interfaces. The independent laboratory measured 16.6 MPa at 90 degrees against 24 MPa at 0 degrees.
        - label: Porosity
          line: Calculated porosity ranges from 8.8 to 15.1 percent by method. The paper says it is concentrated at layer interfaces.
    - title: Lunar exposure
      lead: Long-term lunar exposure has not been measured for this composite.
      verdict: 'Untested: thermal, UV and vacuum'
      points:
        - label: Thermal cycling
          line: Thermal fatigue across the lunar temperature range is still to be tested.
        - label: Ultraviolet
          line: The paper names UV degradation as a lunar risk, with no test reported.
        - label: Vacuum mass loss
          line: Mass loss from outgassing over the life of a lunar facility is still to be measured.
  why: Regolith-polymer composite (RPC) is a building material that mixes lunar regolith simulant with a plastic binder and prints it layer by layer, so a shelter could be built from local soil. NASA's REACT project printed it in simulated lunar dirty thermal vacuum and built a sub-scale protective shelter, the Lunar Infrastructure Asset (LINA). The project describes the work as "approaching TRL 5", and long-term lunar exposure tests remain to be done. The paper says the LINA structure was driven more by stiffness than by strength.
  uses:
    - where: Lunar shelter structure
      line: The Lunar Infrastructure Asset (LINA) is an unpressurized shelter designed to support 2.3 m of regolith overburden. A sub-scale LINA was printed on regolith simulant in dirty vacuum as the project's final test.
    - where: Ground demonstration, not flight
      line: The composite has not yet flown. The slides recommend a small Commercial Lunar Payload Services (CLPS) demonstration mission as the next step, after a large-scale demonstration at NASA's 3D printed habitat Centennial Challenge.
  can_do:
    - label: Flexural strength
      benchmark: flexural_strength
      value: 24 MPa at 0 degrees; 16.6 MPa at 90 degrees
      line: In one independent laboratory's tests, 80:20 LHS-1:PLA reached 24 MPa flexural strength in the 0 degree direction and 16.6 MPa across the print at 90 degrees.
    - label: Stiffness
      benchmark: flexural_modulus
      value: 5.3 GPa at 0 degrees; 3.7 GPa at 90 degrees
      line: In the same independent tests, flexural modulus was 5.3 GPa at 0 degrees and 3.7 GPa at 90 degrees.
    - label: Density
      benchmark: density
      value: 1.80 g/cc for pellets
      line: Pellets of the 80:20 LHS-1:PLA blend measured 1.80 g/cc by volumetric displacement, and ambient prints measured 1.82 g/cc.
    - label: Void content
      benchmark: porosity
      value: 8.8 to 15.1 percent
      line: Porosity ranged from 8.8 to 15.1 percent depending on the method and print condition, and the paper says it is concentrated at layer interfaces.
    - label: Cold PLA
      benchmark: ultimate_tensile_strength
      value: 87 MPa at 77 K, pure PLA
      line: The paper quotes an 87 MPa tensile strength at 77 K for pure PLA. This is the binder alone, not the composite, and no cryogenic strength for the composite is reported.
  compare: 'The 80:20 LHS-1:PLA blend is much denser than its binder alone: 1.80 g/cc for pellets against 1.28 g/cc for pure PLA pellets, both by volumetric displacement. Its strength depends on print direction. In the independent laboratory''s tests it reached 24 MPa flexural strength at 0 degrees and 16.6 MPa at 90 degrees. In SpaceFactory''s tests the same blend reached 34.40 MPa and 14.90 MPa. The paper says its flexural strength is significantly higher than that of lumber and concrete, but it gives no cryogenic strength for the composite.'
  compare_rows:
    - label: Density, pellets
      benchmark: density
    - label: Flexural strength, 0 degrees
      benchmark: flexural_strength
    - label: Flexural modulus, 0 degrees
      benchmark: flexural_modulus
  handling:
    - Keep dust down with good housekeeping and dust control, because dust layers can ignite.
    - Use an approved dust respirator in dusty air, and ventilate the processing area, since fumes can be released at melt temperature.
    - Dry the PLA before compounding, because PLA absorbs moisture that can degrade it during extrusion.
  good_for:
    - Ground demonstrations of printed shelter structures made from regolith simulant and a bio-based binder.
    - Stiffness-driven structural design. The paper says the LINA design was driven more by modulus than by strength.
  watch_out:
    - 'Strength across the print layers is lower than along them: 16.6 MPa at 90 degrees against 24 MPa at 0 degrees, by the independent laboratory.'
    - Porosity of 8.8 to 15.1 percent, depending on the method, concentrated at layer interfaces.
    - 'Long-term lunar exposure is untested: thermal fatigue, vacuum mass loss and UV are all listed as remaining tests.'
    - PLA has a low heat distortion temperature, which the paper says would limit its performance in direct sunlight.
  verdict: A promising ground-tested lunar construction material. Its strength is adequate on paper, but long-term lunar exposure is untested and it is weaker across the print layers.