AETB-8 rigid tile (alumina enhanced thermal barrier) AETB-8
Silica-alumina fibrous ceramic tile. TPSX composition as printed: 68% SiO2, 20% Al2O3, and 12% of an aluminoborosilicate fibre (14% B2O3, 72% Al2O3, 14% SiO2).
AETB-8 is a rigid reusable insulation tile of the alumina enhanced thermal barrier (AETB) family.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Density
7.9 pcf
Insulation
0.0684 W/m-K
Use temperature
1537 °C
Strength
63.9 psi
Recipe, share of the weight
- SiO2 68%Silica
- Al2O3 20%Alumina
- 12%Aluminoborosilicate fibre (Nextel-type)
Best for
Reusable insulation on the hot base of a re-entry vehicle, where low density and low thermal conductivity matter more than strength. NASA's TPSX database says AETB-8 flew in the Shuttle base heat shield.
Weakest at
Through-the-thickness tensile strength. The 2025 NASA deck reports 30.7 psi for modern-fibre tiles against a 35 psi or more specification, so strength is the open issue NASA is working on.
Risk at a glance
- People None found. Carcinogen label for the fibre family (H350i)
- If it fails Moderate. Low through-the-thickness tensile strength in modern-fibre tiles
- Corrosion Moderate. Firing left a property gradient near the bottom of the as-fired billet, which NASA says it identified and mitigated.
Quick facts: AETB-8
| Property | Value | Basis |
|---|---|---|
| Density | 7.6 to 8.8 pcf | 4 sourced values across conditions |
| Tensile strength | 0.14 to 0.44 MPa | 5 sourced values across conditions |
| Thermal conductivity | 0.068 W/(m·K) | 1 sourced value |
| Maximum service temperature | 1,537 °C | 1 sourced value |
What is the density of AETB-8 rigid tile?
AETB-8 rigid tile has a density of 7.6 to 8.8 pcf. The range covers 4 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the thermal conductivity of AETB-8 rigid tile?
AETB-8 rigid tile has a thermal conductivity of 0.068 W/(m·K). The source and test conditions are listed in the properties table on this page.
What is the tensile strength of AETB-8 rigid tile?
AETB-8 rigid tile has a tensile strength of 0.14 to 0.44 MPa. The range covers 5 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the maximum service temperature of AETB-8 rigid tile?
AETB-8 rigid tile has a maximum service temperature of 1,537 °C. The source and test conditions are listed in the properties table on this page.
What is AETB-8 rigid tile used for?
Uses recorded in the sources include Space Shuttle orbiter base heat shield (flown); Orion capsule backshell (fabricated tiles; flight use not stated in the source).
Why it exists
AETB-8 is a rigid reusable insulation tile from the alumina enhanced thermal barrier (AETB) family. TPSX states that it is flying successfully in the Shuttle base heat shield, with improved performance relative to the original LI-900 tile. NASA is now re-qualifying the material with modern raw materials, because the 2025 deck reports that tiles made from modern fibres had reduced mechanical properties in early tests. Those raw materials are compared against "heritage" fibres, meaning the raw materials NASA bought for the Shuttle programme in the 1990s. NASA's 2024 AETB modernization slides list AETB-8 among the current HRSI tile materials, with LI-900 described as essentially obsolete.
Where it's used
Shuttle orbiter base heat shield
TPSX states that AETB-8 is flying successfully in the base heatshield. TPSX also says it performs better than the original LI-900 tile.
Orion capsule backshell
The 2025 deck shows AETB-8 fabricated for the Orion backshell. The deck does not say that the tile has flown on Orion.
Recipe
Silica-alumina fibrous ceramic tile. TPSX composition as printed: 68% SiO2, 20% Al2O3, and 12% of an aluminoborosilicate fibre (14% B2O3, 72% Al2O3, 14% SiO2).
AETB-8 is a fibre composite tile, not a single compound. TPSX prints its composition as 68% SiO2, 20% Al2O3 and 12% aluminoborosilicate fibre. The 2025 deck's process flow is fibres, water and additives blended in a V-blender, cast in a casting tower, dried in an oven and fired in a furnace up to 2400 degF.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Silica SiO2 | 68% | Largest constituent by mass per the TPSX composition line. The deck's AETB list also names silica (Q-fiber) fibres. |
| Alumina Al2O3 | 20% | Alumina component named in the TPSX composition line. The deck lists alumina fibres (Saffil) as a constituent of AETB. |
| Aluminoborosilicate fibre (Nextel-type) | 12% | TPSX prints this fraction as 14% B2O3, 72% Al2O3 and 14% SiO2. The deck names it as Nextel-312 and reports that its pre-firing changes billet texture and tensile strength. |
Weight shares are as printed in the sources.
What it can do
Density
7.9 pcf
measured
Uncoated AETB-8 tile has a density of 1.28e+02 kg/m^3, listed as measured by TPSX. The 2025 deck prints 7.9 ± 0.1 pcf for modern-fibre billets.
Insulation
0.0684 W/m-K
worked out from the formula
TPSX predicts a through-the-thickness thermal conductivity of 6.84e-02 W/m-K, from a curve fit that is extrapolated above 1533 K.
Use temperature
1537 °C
measured
The 2025 deck says AETB is used up to 1537 degC (2800 degF).
Strength
63.9 psi
measured
Modern-fibre billets in the 2025 deck measure 63.9 ± 5.8 psi in-plane (46 samples) and 30.7 ± 2.7 psi through-the-thickness (75 samples). Both are reported with their specifications.
Reuse
TPSX predicts a reuse limit of 1.00e+02 flights, predicted from arcjet and flight test data.
How it compares
AETB-8 is a low-density silica tile. TPSX lists its uncoated density as 1.28e+02 kg/m^3, measured. Wikipedia gives its own density figures for the black LI-900 silica tile and for FRCI tiles; they come from different tests and are not directly comparable with the TPSX value. TPSX states that AETB-8 has higher temperature capability and better processing dimensional stability than the earlier tiles it lists, including FRCI-12 and LI-900. For through-the-thickness strength, TPSX lists 3.79e+05 Pa as measured, and the 2025 deck lists 30.7 psi for modern fibres and 34.9 psi for heritage fibres; these are different tests and dates, so the values are not converted to each other. The deck says the heritage and modern tensile strengths were statistically equivalent at a 95% confidence interval (PDF page 7).
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details.
| Measurement | AETB-8 |
|---|---|
| Thermal behavior and safety | |
| Thermal conductivity, through-the-thickness (TPSX) | 0.0684 W/m-K3 |
| Physical and electrical | |
| Density, modern-fibre billets (2025 deck) | 7.9 pcf1 |
| Density, heritage-fibre billets (2025 deck) | 7.8 pcf2 |
| Density, bottom of as-fired billet, cold setter plate (2025 deck) | 7.6 pcf11 |
| Density, bottom of as-fired billet, hot setter plate (2025 deck) | 8.8 pcf12 |
| Other measurements | |
| Emissivity, uncoated tile (TPSX) | 0.899 -4 |
| Used-up-to temperature (2025 deck) | 1537 °C5 |
| Porosity (2025 deck, approximate) | 95 %6 |
| Ultimate tensile strength, in-plane, modern fibres (2025 deck) | 63.9 psi7 |
| Ultimate tensile strength, through-the-thickness, modern fibres (2025 deck) | 30.7 psi8 |
| Ultimate tensile strength, in-plane, heritage fibres (2025 deck) | 63.4 psi9 |
| Ultimate tensile strength, through-the-thickness, heritage fibres (2025 deck) | 34.9 psi10 |
| Ultimate tensile strength, through-the-thickness, bottom of as-fired billet, cold setter plate (2025 deck) | 20 psi13 |
Why choose it, and why not
Good for
- Low density and low thermal conductivity on a hot, reusable base heat shield, as flown on the Shuttle (TPSX).
- Use up to 1537 degC (2800 degF), as stated in NASA's 2025 deck.
Watch out for
- Through-the-thickness strength: the 2025 deck reports 30.7 ± 2.7 psi for modern-fibre tiles against a specification of 35 psi or more.
- In-plane strength: the modern-fibre mean is 63.9 psi against a specification of 65 psi or more.
- Most thermal and temperature-limit values are predicted by TPSX, and the TPSX property table dates from 2001 to 2006.
AETB-8 is a flight-proven, low-density reusable insulation tile with a use temperature of 1537 degC (2800 degF) stated by NASA. Its strength is still the open issue: the 2025 deck says modern-fibre tiles need further process work to meet the through-the-thickness specification.
Used in space products
Space hardware whose maker names AETB-8, with the part it is used for.
| Product | Where it is used |
|---|---|
| Orion spacecraftNASA | Forward bay cover (tile-covered lid over the parachute bay) |
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, modern-fibre billets (2025 deck) | Measured density of cast billets, as printed in the heritage-versus-modern table | fibre modern fibresuncertainty ±0.1 pcfunit note printed in pcf, not converted | — |
| 2 | Density, heritage-fibre billets (2025 deck) | Measured density of cast billets, as printed in the heritage-versus-modern table | fibre heritage fibresuncertainty ±0.1 pcfunit note printed in pcf, not converted | — |
| 3 | Thermal conductivity, through-the-thickness (TPSX) | Listed as predicted in the TPSX table (Source column), not measured | direction through-the-thicknessbasis dynamic values for transient environments from a curve fit to measured values, extrapolated above 1533 K (note 2)uncertainty 3.42e-03 | — |
| 4 | Emissivity, uncoated tile (TPSX) | Listed as measured at room temperature in the TPSX table (Source column) | state uncoated tiletemperature room temperature; higher-temperature values are extrapolated (note 4)uncertainty 4.49e-02 | — |
| 5 | Used-up-to temperature (2025 deck) | Statement in the deck's AETB overview slide, not a measurement table | statement used up to this temperature, as stated in the deck; not a failure testprinted as 1537oC (2800oF) | — |
| 6 | Porosity (2025 deck, approximate) | Statement in the deck's AETB overview slide, not a measurement table | qualifier approximate, printed as ~95% | — |
| 7 | Ultimate tensile strength, in-plane, modern fibres (2025 deck) | Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9) | fibre modern fibressample count 46uncertainty ±5.8 psispecification all samples 65 psi or more, as printed in the deck | — |
| 8 | Ultimate tensile strength, through-the-thickness, modern fibres (2025 deck) | Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9) | fibre modern fibressample count 75uncertainty ±2.7 psispecification all samples 35 psi or more, as printed in the deck | — |
| 9 | Ultimate tensile strength, in-plane, heritage fibres (2025 deck) | Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9) | fibre heritage fibres (raw materials bought for the Shuttle programme in the 1990s)sample count 9uncertainty ±17.0 psispecification all samples 65 psi or more, as printed in the deck | — |
| 10 | Ultimate tensile strength, through-the-thickness, heritage fibres (2025 deck) | Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9) | fibre heritage fibres (raw materials bought for the Shuttle programme in the 1990s)sample count 8uncertainty ±6.6 psispecification all samples 35 psi or more, as printed in the deck | — |
| 11 | Density, bottom of as-fired billet, cold setter plate (2025 deck) | Measured density of the as-fired billet at the bottom location, as printed in the firing-process table | setter plate cold (room-temperature LI-2200 setter plate)billet location bottom (as-fired)uncertainty ±0.06 pcfunit note printed in pcf, not converted | — |
| 12 | Density, bottom of as-fired billet, hot setter plate (2025 deck) | Measured density of the as-fired billet at the bottom location, as printed in the firing-process table | setter plate hot (D-tube loading, hot furnace hearth)billet location bottom (as-fired)uncertainty ±0.07 pcfunit note printed in pcf, not converted | — |
| 13 | Ultimate tensile strength, through-the-thickness, bottom of as-fired billet, cold setter plate (2025 deck) | Measured, as printed in the firing-process table; the deck states the TTT strength is more sensitive to firing than the in-plane strength | setter plate cold (room-temperature LI-2200 setter plate)billet location bottom (as-fired)direction through-the-thicknessuncertainty ±4.7 psiunit note printed in psi, not converted | — |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Firing of the cast billet (process, not service) | moderate | Firing left a property gradient near the bottom of the as-fired billet, which NASA says it identified and mitigated.1 |
| Heating to the use limit and cooling, repeated over flights | low | NASA's 2025 deck says AETB has lower thermally induced shrinkage than the earlier LI and FRCI tile generations.2 |
| Reuse over many flights (predicted, not flight-measured) | moderate | TPSX predicts a reuse limit of 1.00e+02 flights, predicted from arcjet and flight test data.3 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Firing of the cast billet (process, not service) | NASA's 2025 deck reports the largest property variation near the bottom of the as-fired billet and says a firing-induced property gradient was identified and mitigated. The deck gives no number for the size of the gradient. | process firing of cast AETB billets in the furnace, up to 2400 degF (deck PDF page 6) |
| 2 | Heating to the use limit and cooling, repeated over flights | The deck states that AETB has lower thermally induced shrinkage than earlier tile generations (LI- and FRCI). It gives no shrinkage number, so the comparison is qualitative. | basis qualitative statement in the deck; no test conditions given |
| 3 | Reuse over many flights (predicted, not flight-measured) | TPSX lists a reuse flight limit of 1.00e+02 flights, labelled as predicted. It is not a measured service life for AETB-8, and the page does not give the test conditions behind the prediction. | basis prediction from arcjet and flight test data (TPSX note 9) |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
We did not find a safety data sheet for AETB-8 tile itself. A refractory ceramic fibre SDS (alumino-silicate wool, SDS 103) carries the H350i statement, and this profile uses it as a class-level entry for the fibre family, not an AETB-8 classification.
- Inhalation
- The refractory ceramic fibre SDS says 'May cause cancer by inhalation (H350i)'. IARC places refractory ceramic fibres in group 2B, and the SDS gives a NIOSH recommended exposure level of 0.5 f/ml (TWA). Check the supplier's SDS for the AETB-8 product before cutting, grinding or handling the tile.
If the tile overheats
The sources give use temperatures, not failure data for this tile.
- Used up to
- NASA's 2025 deck says AETB is used up to 1537 degC (2800 degF).
- Above the limit
- No test of AETB-8 above this limit was found in the sources read.
Handling and storage
- Not found
- No storage or handling instructions for AETB-8 were found in the sources read.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Low through-the-thickness tensile strength in modern-fibre tilesmoderate severity | Early casting runs with modern fibres, before the later process changesThrough-the-thickness strength of 30.7 psi (75 samples) against a specification of 35 psi or more; in-plane mean of 63.9 psi against 65 psi or more. The deck says further process work is needed to meet specification. |
| Property gradient in the bottom of the as-fired billetlow severity | Firing of the cast billet; the largest variation is near the bottom of the as-fired billetThe largest property variation in the billet is near the bottom (as-fired). The deck says the gradient was identified and mitigated, but gives no number for it. |
Mitigations
- The deck says preliminary process improvements have resulted in significantly improved through-the-thickness tensile strength, achieving heritage specifications. No number is given for the improved value.
Supply and geography
How common the raw materials are and where they come from.
Silicon (silicon carbide and silica constituents)
The USGS silicon chapter describes world and domestic resources for silicon metal and alloys as abundant. China accounted for almost 80% of estimated global silicon-materials production in 2025.
- Critical mineral lists
- US: listed
- Recycling
- USGS silicon chapter: recycling 'Insignificant'.
- Substitutes
- USGS: gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications.
Aluminium metal (context only; the alumina fibre in AETB is not covered by this chapter)
USGS: global resources of bauxite are estimated at 55 billion to 75 billion tons.
- Top producers (2025)
- China 60.8%, India 5.7%, Russia 5.3%, Canada 4.5%
- Recycling
- USGS: aluminum recovered from purchased scrap in the United States was about 3.6 million tons in 2025.
- Substitutes
- USGS: composites can substitute for aluminum in aircraft fuselages and wings.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
spore: profile
id: aetb-8-tile
spore_version: 0.2
family: silica
name: AETB-8 rigid tile (alumina enhanced thermal barrier)
abbreviation: AETB-8
role: Reusable rigid insulation tile for the Space Shuttle orbiter base heat shield, re-qualified with modern fibres
category: thermal-protection
type: reusable-tiles
summary: |
AETB-8 is a rigid reusable insulation tile of the alumina enhanced thermal barrier (AETB) family. NASA's TPSX database gives a measured density of 1.28e+02 kg/m^3 for uncoated tile and a predicted through-the-thickness thermal conductivity of 6.84e-02 W/m-K. NASA's 2025 Ames deck says AETB is used up to 1537 degC (2800 degF) and has about 95% porosity. In the deck's tests, tiles cast from modern fibres measured 63.9 psi in-plane tensile strength (against a 65 psi or more specification) and 30.7 psi through-the-thickness strength (against 35 psi or more).
best_for: Reusable insulation on the hot base of a re-entry vehicle, where low density and low thermal conductivity matter more than strength. NASA's TPSX database says AETB-8 flew in the Shuttle base heat shield.
weakest_at: Through-the-thickness tensile strength. The 2025 NASA deck reports 30.7 psi for modern-fibre tiles against a 35 psi or more specification, so strength is the open issue NASA is working on.
identity:
formula: 'Silica-alumina fibrous ceramic tile. TPSX composition as printed: 68% SiO2, 20% Al2O3, and 12% of an aluminoborosilicate fibre (14% B2O3, 72% Al2O3, 14% SiO2).'
source: tpsx-aetb8
where: Material page header, Composition line (TPSX Material id=5). Constituent fibres from the 2025 NASA deck, PDF page 5 (Nextel-312, Saffil alumina, Q-fiber silica and silicon carbide).
tags:
environments:
- re-entry
stresses:
- extreme-heat
applications:
- heat-shields
properties:
- benchmark: density
label: Density, modern-fibre billets (2025 deck)
value: 7.9
unit: pcf
scope: material
conditions:
fibre: modern fibres
uncertainty: ±0.1 pcf
unit_note: printed in pcf, not converted
method: Measured density of cast billets, as printed in the heritage-versus-modern table
status: ground
source: ntrs-caldwell-irtps
where: PDF page 7, Initial Production Using Heritage vs Modern Fibers table, Modern row
- benchmark: density
label: Density, heritage-fibre billets (2025 deck)
value: 7.8
unit: pcf
scope: material
conditions:
fibre: heritage fibres
uncertainty: ±0.1 pcf
unit_note: printed in pcf, not converted
method: Measured density of cast billets, as printed in the heritage-versus-modern table
status: ground
source: ntrs-caldwell-irtps
where: PDF page 7, Initial Production Using Heritage vs Modern Fibers table, Heritage row
- benchmark: thermal_conductivity
label: Thermal conductivity, through-the-thickness (TPSX)
value: 0.0684
unit: W/m-K
scope: material
conditions:
direction: through-the-thickness
basis: dynamic values for transient environments from a curve fit to measured values, extrapolated above 1533 K (note 2)
uncertainty: '3.42e-03'
method: Listed as predicted in the TPSX table (Source column), not measured
status: calculated
source: tpsx-aetb8
where: Properties at Standard Conditions table, Thermal Conductivity (Thru-the-Thickness) row (note 2)
- benchmark: emissivity
label: Emissivity, uncoated tile (TPSX)
value: 0.899
unit: '-'
scope: material
conditions:
state: uncoated tile
temperature: room temperature; higher-temperature values are extrapolated (note 4)
uncertainty: '4.49e-02'
method: Listed as measured at room temperature in the TPSX table (Source column)
status: ground
source: tpsx-aetb8
where: Properties at Standard Conditions table, Emissivity row (note 4)
- benchmark: max_service_temp
label: Used-up-to temperature (2025 deck)
value: 1537
unit: degC
scope: material
conditions:
statement: used up to this temperature, as stated in the deck; not a failure test
printed_as: 1537oC (2800oF)
method: Statement in the deck's AETB overview slide, not a measurement table
status: ground
source: ntrs-caldwell-irtps
where: PDF page 5, Alumina Enhanced Thermal Barrier (AETB) slide, bullet 'Used up to'
- benchmark: porosity
label: Porosity (2025 deck, approximate)
value: 95
unit: '%'
scope: material
conditions:
qualifier: approximate, printed as ~95%
method: Statement in the deck's AETB overview slide, not a measurement table
status: ground
source: ntrs-caldwell-irtps
where: PDF page 5, Alumina Enhanced Thermal Barrier (AETB) slide, bullet 'Thermally insulative with ~95% porosity'
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, in-plane, modern fibres (2025 deck)
value: 63.9
unit: psi
scope: material
conditions:
fibre: modern fibres
sample_count: 46
uncertainty: ±5.8 psi
specification: all samples 65 psi or more, as printed in the deck
method: Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9)
status: ground
source: ntrs-caldwell-irtps
where: PDF page 7, Initial Production Using Heritage vs Modern Fibers table, Modern row, IP
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, through-the-thickness, modern fibres (2025 deck)
value: 30.7
unit: psi
scope: material
conditions:
fibre: modern fibres
sample_count: 75
uncertainty: ±2.7 psi
specification: all samples 35 psi or more, as printed in the deck
method: Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9)
status: ground
source: ntrs-caldwell-irtps
where: PDF page 7, Initial Production Using Heritage vs Modern Fibers table, Modern row, TTT
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, in-plane, heritage fibres (2025 deck)
value: 63.4
unit: psi
scope: material
conditions:
fibre: heritage fibres (raw materials bought for the Shuttle programme in the 1990s)
sample_count: 9
uncertainty: ±17.0 psi
specification: all samples 65 psi or more, as printed in the deck
method: Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9)
status: ground
source: ntrs-caldwell-irtps
where: PDF page 7, Initial Production Using Heritage vs Modern Fibers table, Heritage row, IP
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, through-the-thickness, heritage fibres (2025 deck)
value: 34.9
unit: psi
scope: material
conditions:
fibre: heritage fibres (raw materials bought for the Shuttle programme in the 1990s)
sample_count: 8
uncertainty: ±6.6 psi
specification: all samples 35 psi or more, as printed in the deck
method: Measured in the deck's heritage-versus-modern table; tensile testing followed ASTM D 1623 (PDF page 9)
status: ground
source: ntrs-caldwell-irtps
where: PDF page 7, Initial Production Using Heritage vs Modern Fibers table, Heritage row, TTT
- benchmark: density
label: Density, bottom of as-fired billet, cold setter plate (2025 deck)
value: 7.6
unit: pcf
scope: material
conditions:
setter_plate: cold (room-temperature LI-2200 setter plate)
billet_location: bottom (as-fired)
uncertainty: ±0.06 pcf
unit_note: printed in pcf, not converted
method: Measured density of the as-fired billet at the bottom location, as printed in the firing-process table
status: ground
source: ntrs-caldwell-irtps
where: PDF page 14 (Firing Process table, printed slide 15), Cold Setter Plate, Bottom column, Density (pcf) row
- benchmark: density
label: Density, bottom of as-fired billet, hot setter plate (2025 deck)
value: 8.8
unit: pcf
scope: material
conditions:
setter_plate: hot (D-tube loading, hot furnace hearth)
billet_location: bottom (as-fired)
uncertainty: ±0.07 pcf
unit_note: printed in pcf, not converted
method: Measured density of the as-fired billet at the bottom location, as printed in the firing-process table
status: ground
source: ntrs-caldwell-irtps
where: PDF page 14 (Firing Process table, printed slide 15), Hot Setter Plate, Bottom column, Density (pcf) row
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, through-the-thickness, bottom of as-fired billet, cold setter plate (2025 deck)
value: 20
unit: psi
scope: material
conditions:
setter_plate: cold (room-temperature LI-2200 setter plate)
billet_location: bottom (as-fired)
direction: through-the-thickness
uncertainty: ±4.7 psi
unit_note: printed in psi, not converted
method: Measured, as printed in the firing-process table; the deck states the TTT strength is more sensitive to firing than the in-plane strength
status: ground
source: ntrs-caldwell-irtps
where: PDF page 14 (Firing Process table, printed slide 15), Cold Setter Plate, Bottom column, TTT UTS (psi) row
corrosion:
- environment: Firing of the cast billet (process, not service)
headline: Firing left a property gradient near the bottom of the as-fired billet, which NASA says it identified and mitigated.
effect: NASA's 2025 deck reports the largest property variation near the bottom of the as-fired billet and says a firing-induced property gradient was identified and mitigated. The deck gives no number for the size of the gradient.
rating: moderate
conditions:
process: firing of cast AETB billets in the furnace, up to 2400 degF (deck PDF page 6)
source: ntrs-caldwell-irtps
where: PDF pages 12, 13 and 17 (Property Variation Within Billet; Firing Process; Summary)
- environment: Heating to the use limit and cooling, repeated over flights
headline: NASA's 2025 deck says AETB has lower thermally induced shrinkage than the earlier LI and FRCI tile generations.
effect: The deck states that AETB has lower thermally induced shrinkage than earlier tile generations (LI- and FRCI). It gives no shrinkage number, so the comparison is qualitative.
rating: low
conditions:
basis: qualitative statement in the deck; no test conditions given
source: ntrs-caldwell-irtps
where: PDF page 5, Alumina Enhanced Thermal Barrier (AETB) slide, bullet 'Lower thermally induced shrinkage'
- environment: Reuse over many flights (predicted, not flight-measured)
headline: TPSX predicts a reuse limit of 1.00e+02 flights, predicted from arcjet and flight test data.
effect: TPSX lists a reuse flight limit of 1.00e+02 flights, labelled as predicted. It is not a measured service life for AETB-8, and the page does not give the test conditions behind the prediction.
rating: moderate
conditions:
basis: prediction from arcjet and flight test data (TPSX note 9)
source: tpsx-aetb8
where: Properties at Standard Conditions table, Reuse Flight Limit row (note 9)
risks:
hazards:
- text: No safety data sheet for AETB-8 tile itself was found. A supplier safety data sheet for a refractory ceramic fibre (alumino-silicate wool) product states the hazard statement 'May cause cancer by inhalation (H350i)' with signal word Danger and pictogram GHS08. This is a class-level entry for the fibre family, not an AETB-8 classification.
ghs:
- H350i
source: cerafelt-sds-103
where: Hazard pictogram, signal word and hazard statement block at the start of the SDS (SDS 103, last revised 26 February 2025)
- text: The same refractory ceramic fibre SDS gives IARC's overall evaluation as 'Refractory Ceramic Fibres are possibly carcinogenic to humans (group 2B)' and a NIOSH recommended exposure level of '0.5 f/ml (TWA)', with further action advised above 0.25 f/ml. The SDS cites NIOSH's 2006 criteria document as the source; that document was not read in this run.
ghs: []
source: cerafelt-sds-103
where: Carcinogenicity text and the exposure guidelines section of SDS 103
- text: PubChem's record for silica (CID 24261), one constituent of the AETB family, lists its primary hazards as 'Not Classified'. This is a constituent record, not a classification of AETB-8.
ghs: []
source: pubchem-silica
where: Safety and Hazards, Primary Hazards (reference 99)
failure_risks:
- mode: Low through-the-thickness tensile strength in modern-fibre tiles
trigger: Early casting runs with modern fibres, before the later process changes
consequence: Through-the-thickness strength of 30.7 psi (75 samples) against a specification of 35 psi or more; in-plane mean of 63.9 psi against 65 psi or more. The deck says further process work is needed to meet specification.
severity: moderate
source: ntrs-caldwell-irtps
where: PDF page 7 (Initial Production Using Heritage vs Modern Fibers) and page 17 (Summary)
- mode: Property gradient in the bottom of the as-fired billet
trigger: Firing of the cast billet; the largest variation is near the bottom of the as-fired billet
consequence: The largest property variation in the billet is near the bottom (as-fired). The deck says the gradient was identified and mitigated, but gives no number for it.
severity: low
source: ntrs-caldwell-irtps
where: PDF page 12 (Property Variation Within Billet) and page 13 (Firing Process)
side_effects: []
handling: []
mitigations:
- text: The deck says preliminary process improvements have resulted in significantly improved through-the-thickness tensile strength, achieving heritage specifications. No number is given for the improved value.
source: ntrs-caldwell-irtps
where: PDF page 17 (Summary)
uses:
- application: heat-shields
device: Space Shuttle orbiter base heat shield (flown)
example: TPSX says AETB-8 is flying successfully in the base heatshield, with improved performance relative to the original LI-900 tile.
source: tpsx-aetb8
where: Description section of the TPSX Material page
- application: heat-shields
device: Orion capsule backshell (fabricated tiles; flight use not stated in the source)
example: The 2025 deck shows an AETB-8 tile fabricated for the Orion backshell. The deck says Orion uses the Shuttle TPS starting point for its backshell, for different reasons.
source: ntrs-caldwell-irtps
where: PDF page 5 (photo caption 'AETB-8 fabricated for Orion backshell') and page 3 (Background)
supply:
- subject: Silicon (silicon carbide and silica constituents)
abundance: The USGS silicon chapter describes world and domestic resources for silicon metal and alloys as abundant. China accounted for almost 80% of estimated global silicon-materials production in 2025.
producers: []
critical_lists:
- list: USGS 2025 List of Critical Minerals (silicon added in 2025)
listed: true
recycling: 'USGS silicon chapter: recycling ''Insignificant''.'
substitutes:
- 'USGS: gallium arsenide and germanium are the principal substitutes for silicon in semiconductor and infrared applications.'
source: usgs-mcs2026-silicon
where: Events, Trends, and Issues (China almost 80%); World Resources; Recycling; Substitutes; Critical minerals note. The USGS silicon chapter does not cover silicon carbide or alumina fibre by name.
- subject: Aluminium metal (context only; the alumina fibre in AETB is not covered by this chapter)
abundance: 'USGS: global resources of bauxite are estimated at 55 billion to 75 billion tons.'
producers:
- country: China
share_percent: 60.8
year: 2025
- country: India
share_percent: 5.7
year: 2025
- country: Russia
share_percent: 5.3
year: 2025
- country: Canada
share_percent: 4.5
year: 2025
critical_lists: []
recycling: 'USGS: aluminum recovered from purchased scrap in the United States was about 3.6 million tons in 2025.'
substitutes:
- 'USGS: composites can substitute for aluminum in aircraft fuselages and wings.'
source: usgs-mcs2026-aluminum
where: World Smelter Production and Capacity table, 2025e (China 45,000 of a 74,000 thousand t world total; India 4,200, Russia 3,900 and Canada 3,300 thousand t). Shares calculated by Space Mushroom against the 74,000 world total, rounded to one decimal.
documents:
- title: 'NASA TPSX Materials Database: AETB-8 Rigid Tile (Material id=5)'
type: database
url: https://tpsx.arc.nasa.gov/Material?id=5
year: 2006
- title: Modernization of Insulative Reusable Thermal Protection Systems (IRTPS), NASA Ames, 2025 (NTRS 20250000871)
type: report
url: https://ntrs.nasa.gov/api/citations/20250000871/downloads/non-CUI%20ACaldwell%20Modernization%20of%20IRTPS%20Final3.pdf
year: 2025
- title: 'USGS Mineral Commodity Summaries 2026: Silicon'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Aluminum'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
year: 2026
- title: NASA AETB modernization slides, NTRS 20240000772 (2024)
type: report
url: https://ntrs.nasa.gov/api/citations/20240000772/downloads/CMS24%20Caldwell.pdf
year: 2024
- title: Safety Data Sheet SDS 103, Cerafelt refractory ceramic fibre products (Morgan Thermal Ceramics)
type: sds
url: https://morganthermalceramics.com/media/zojnxex5/103-ghs-uae.pdf
year: 2025
- title: 'PubChem compound record: Silica (CID 24261)'
type: database
url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/24261/JSON
gaps:
- 'X-33: the brief names X-33 flights, but no page read in this run (TPSX, the 2025 deck, Wikipedia or the USGS chapters) mentions X-33. The 2025 deck names the X-37B and Orion instead. X-33 is left out.'
- 'Hazards: no safety data sheet for AETB-8 tile itself was found. The hazard entries are class-level: a refractory ceramic fibre SDS (SDS 103, Cerafelt, which lists H350i) and the PubChem silica record (not classified). The PubChem compound page for silica returned a browser check, so its record was read through the PubChem REST endpoint.'
- 'NIOSH 2006 criteria document (DHHS 2006-123): the PDF was not reachable in this run, so the 0.5 f/ml TWA exposure level is taken from SDS 103, which cites that document. It is a secondary citation.'
- TPSX values printed in exponent notation (specific heat 6.28e+02 J/kg-K, multiple use temperature limit 1.64e+03 K, single use limit 1.81e+03 K, tensile and modulus values in Pa, and the reuse limit) are left out of the properties list, per the brief on exponent notation. The reuse limit is kept in corrosion with its printed value.
- Handling and storage instructions for AETB-8 tile were not found in any source held.
- Corrosion, moisture and chemical resistance of AETB-8 were not found. The deck and TPSX do not describe coatings, waterproofing or environmental ageing for this grade.
- 'Porosity: TPSX does not list porosity. The ~95% value is from the 2025 deck (PDF page 5) and is approximate.'
- Emissivity, porosity and reuse flight limit are not in spores/property-canon.yaml. Short snake_case names are used, as the brief allows.
- 'TPSX values are old: the page is last modified 2001-10-01 and the table rows 2006-01-05, before the 2025 modern-fibre work. TPSX does not say which fibre lot or billet the values are for.'
- Predicted values (TPSX Source column 'predicted') are marked calculated, not ground.
- TPSX and the 2025 deck give different tensile values for through-the-thickness strength (TPSX 3.79e+05 Pa; deck 30.7 psi for modern fibres). Both are kept with their sources and are not converted to each other.
- The deck's density range of 0.13 to 0.32 g/cc (AETB-8, -12, -17 and -20 pcf) covers the family, not AETB-8 alone, so it is not used as a property.
- 'Designations: no UNS, EN, ASTM or other grade code was found for AETB-8; the name AETB-8 is the only designation in the sources.'
- Supply of the AETB constituents (Nextel-312, Saffil alumina fibre, Q-fiber, silicon carbide) was not found. The USGS aluminum chapter covers metal, not alumina fibre, and the USGS alumina and silicon carbide chapters were not read.
- 'Producers: TPSX names Boeing, Forrest Machining and United Space Alliance as manufacturers, but no country shares for AETB tile were found.'
- 'Media: no image with a usable licence was read in this run, so no media entries are included.'
sources:
tpsx-aetb8:
title: 'NASA TPSX Materials Database: AETB-8 Rigid Tile'
id: NASA Ames Thermal Protection Materials database, material id 5
url: https://tpsx.arc.nasa.gov/Material?id=5
year: 2006
kind: database
license: NASA public domain (cited, not reproduced)
ntrs-caldwell-irtps:
title: Modernization of Insulative Reusable Thermal Protection Systems (IRTPS), Caldwell et al., NASA Ames Research Center
id: NTRS 20250000871
url: https://ntrs.nasa.gov/api/citations/20250000871/downloads/non-CUI%20ACaldwell%20Modernization%20of%20IRTPS%20Final3.pdf
year: 2025
kind: report
license: NASA public domain (cited, not reproduced)
wikipedia-shuttle-tps:
title: Space Shuttle thermal protection system (Wikipedia)
id: 'Wikipedia article: Space Shuttle thermal protection system'
url: https://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system
kind: web
license: CC BY-SA 4.0 (cited, not reproduced)
usgs-mcs2026-silicon:
title: 'USGS Mineral Commodity Summaries 2026: Silicon'
id: USGS MCS 2026, silicon chapter
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
year: 2026
kind: report
license: US Government work (cited, not reproduced)
usgs-mcs2026-aluminum:
title: 'USGS Mineral Commodity Summaries 2026: Aluminum'
id: USGS MCS 2026, aluminum chapter
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
year: 2026
kind: report
license: US Government work (cited, not reproduced)
ntrs-caldwell-cms24:
title: AETB modernization slides, Caldwell et al., NASA Ames Research Center, 2024
id: NTRS 20240000772
url: https://ntrs.nasa.gov/api/citations/20240000772/downloads/CMS24%20Caldwell.pdf
year: 2024
kind: report
license: NASA public domain (cited, not reproduced)
cerafelt-sds-103:
title: Safety Data Sheet SDS 103, Cerafelt refractory ceramic fibre products (Morgan Thermal Ceramics)
id: Morgan Thermal Ceramics SDS 103
url: https://morganthermalceramics.com/media/zojnxex5/103-ghs-uae.pdf
year: 2025
kind: datasheet
license: Supplier safety data sheet (cited, not reproduced)
pubchem-silica:
title: 'PubChem compound record: Silica (CID 24261)'
id: PubChem CID 24261
url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/24261/JSON
kind: database
license: NLM PubChem terms (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-11-01'
review:
status: draft
method: assistant
checked_values: 13
unreachable: 1
caveats: 3
note: Written by an AI assistant on 2026-11-01 from the NASA TPSX page, the 2025 NASA Ames IRTPS deck, the 2024 NASA AETB modernization slides, the Wikipedia shuttle TPS article, two USGS 2026 chapters, a refractory ceramic fibre SDS (SDS 103) and the PubChem silica record. The hazard entries are class-level, not AETB-8 classifications. The NIOSH 2006 criteria document was not reachable.
story:
recipe:
line: AETB-8 is a fibre composite tile, not a single compound. TPSX prints its composition as 68% SiO2, 20% Al2O3 and 12% aluminoborosilicate fibre. The 2025 deck's process flow is fibres, water and additives blended in a V-blender, cast in a casting tower, dried in an oven and fired in a furnace up to 2400 degF.
parts:
- name: Silica
symbol: SiO2
share_percent: 68
role: Largest constituent by mass per the TPSX composition line. The deck's AETB list also names silica (Q-fiber) fibres.
- name: Alumina
symbol: Al2O3
share_percent: 20
role: Alumina component named in the TPSX composition line. The deck lists alumina fibres (Saffil) as a constituent of AETB.
- name: Aluminoborosilicate fibre (Nextel-type)
share_percent: 12
role: TPSX prints this fraction as 14% B2O3, 72% Al2O3 and 14% SiO2. The deck names it as Nextel-312 and reports that its pre-firing changes billet texture and tensile strength.
risk_groups:
- title: For people
level: 0
verdict: Carcinogen label for the fibre family (H350i)
lead: We did not find a safety data sheet for AETB-8 tile itself. A refractory ceramic fibre SDS (alumino-silicate wool, SDS 103) carries the H350i statement, and this profile uses it as a class-level entry for the fibre family, not an AETB-8 classification.
points:
- label: Inhalation
line: The refractory ceramic fibre SDS says 'May cause cancer by inhalation (H350i)'. IARC places refractory ceramic fibres in group 2B, and the SDS gives a NIOSH recommended exposure level of 0.5 f/ml (TWA). Check the supplier's SDS for the AETB-8 product before cutting, grinding or handling the tile.
- title: If the tile overheats
lead: The sources give use temperatures, not failure data for this tile.
points:
- label: Used up to
line: NASA's 2025 deck says AETB is used up to 1537 degC (2800 degF).
- label: Above the limit
line: No test of AETB-8 above this limit was found in the sources read.
- title: Handling and storage
points:
- label: Not found
line: No storage or handling instructions for AETB-8 were found in the sources read.
why: AETB-8 is a rigid reusable insulation tile from the alumina enhanced thermal barrier (AETB) family. TPSX states that it is flying successfully in the Shuttle base heat shield, with improved performance relative to the original LI-900 tile. NASA is now re-qualifying the material with modern raw materials, because the 2025 deck reports that tiles made from modern fibres had reduced mechanical properties in early tests. Those raw materials are compared against "heritage" fibres, meaning the raw materials NASA bought for the Shuttle programme in the 1990s. NASA's 2024 AETB modernization slides list AETB-8 among the current HRSI tile materials, with LI-900 described as essentially obsolete.
uses:
- where: Shuttle orbiter base heat shield
line: TPSX states that AETB-8 is flying successfully in the base heatshield. TPSX also says it performs better than the original LI-900 tile.
- where: Orion capsule backshell
line: The 2025 deck shows AETB-8 fabricated for the Orion backshell. The deck does not say that the tile has flown on Orion.
can_do:
- label: Density
benchmark: density
line: Uncoated AETB-8 tile has a density of 1.28e+02 kg/m^3, listed as measured by TPSX. The 2025 deck prints 7.9 ± 0.1 pcf for modern-fibre billets.
- label: Insulation
benchmark: thermal_conductivity
line: TPSX predicts a through-the-thickness thermal conductivity of 6.84e-02 W/m-K, from a curve fit that is extrapolated above 1533 K.
- label: Use temperature
benchmark: max_service_temp
line: The 2025 deck says AETB is used up to 1537 degC (2800 degF).
- label: Strength
benchmark: ultimate_tensile_strength
line: Modern-fibre billets in the 2025 deck measure 63.9 ± 5.8 psi in-plane (46 samples) and 30.7 ± 2.7 psi through-the-thickness (75 samples). Both are reported with their specifications.
- label: Reuse
benchmark: reuse_flight_limit
line: TPSX predicts a reuse limit of 1.00e+02 flights, predicted from arcjet and flight test data.
compare: AETB-8 is a low-density silica tile. TPSX lists its uncoated density as 1.28e+02 kg/m^3, measured. Wikipedia gives its own density figures for the black LI-900 silica tile and for FRCI tiles; they come from different tests and are not directly comparable with the TPSX value. TPSX states that AETB-8 has higher temperature capability and better processing dimensional stability than the earlier tiles it lists, including FRCI-12 and LI-900. For through-the-thickness strength, TPSX lists 3.79e+05 Pa as measured, and the 2025 deck lists 30.7 psi for modern fibres and 34.9 psi for heritage fibres; these are different tests and dates, so the values are not converted to each other. The deck says the heritage and modern tensile strengths were statistically equivalent at a 95% confidence interval (PDF page 7).
compare_rows:
- label: Density
benchmark: density
- label: Use temperature
benchmark: max_service_temp
- label: Tensile strength
benchmark: ultimate_tensile_strength
handling:
- No storage or handling instructions for AETB-8 were found in the sources read.
good_for:
- Low density and low thermal conductivity on a hot, reusable base heat shield, as flown on the Shuttle (TPSX).
- Use up to 1537 degC (2800 degF), as stated in NASA's 2025 deck.
watch_out:
- 'Through-the-thickness strength: the 2025 deck reports 30.7 ± 2.7 psi for modern-fibre tiles against a specification of 35 psi or more.'
- 'In-plane strength: the modern-fibre mean is 63.9 psi against a specification of 65 psi or more.'
- Most thermal and temperature-limit values are predicted by TPSX, and the TPSX property table dates from 2001 to 2006.
verdict: 'AETB-8 is a flight-proven, low-density reusable insulation tile with a use temperature of 1537 degC (2800 degF) stated by NASA. Its strength is still the open issue: the 2025 deck says modern-fibre tiles need further process work to meet the through-the-thickness specification.'
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| NASA TPSX Materials Database: AETB-8 Rigid Tile | database | 2006 | 5 values | |
| Modernization of Insulative Reusable Thermal Protection Systems (IRTPS), Caldwell et al., NASA Ames Research Center | report | 2025 | 17 values | |
| Space Shuttle thermal protection system (Wikipedia) | web | 0 values | ||
| USGS Mineral Commodity Summaries 2026: Silicon | report | 2026 | 1 value | |
| USGS Mineral Commodity Summaries 2026: Aluminum | report | 2026 | 1 value | |
| AETB modernization slides, Caldwell et al., NASA Ames Research Center, 2024 | report | 2024 | 0 values | |
| Safety Data Sheet SDS 103, Cerafelt refractory ceramic fibre products (Morgan Thermal Ceramics) | datasheet | 2025 | 2 values | |
| PubChem compound record: Silica (CID 24261) | database | 1 value |
Updated