Materials/Carbon materials/Graphite
PG
misse2-pgIn short
On the International Space Station's forward-facing side, oxygen atoms ate away 35 µm of PG in 3.95 years, about 8.9 µm a year. A standard 25 µm film of it would last about 2.8 years there. It resists atomic oxygen 7.2 times better than Kapton H, the reference film.
Benchmarks
The benchmarks that matter for this material's applications, each compared with the reference engineers use.
| Benchmark | Result | Compared with reference |
|---|---|---|
| Atomic oxygen erosionHow fast low-orbit oxygen eats the surface. Lower is better. | 4.15×10⁻²⁵ cm³/atomLow Earth orbit, 3.95 years in flight | 0.14× Kapton HResists 7.2× better |
Not measured yet (3): darkening under UV and particles (Δα); outgassing, total mass loss (TML); thermal cycling survival.
Applications
Where materials like PG are considered, the benchmarks that decide each use, and what the measured data says so far.
| Application | Deciding benchmarks | What the data says |
|---|---|---|
| External surfaces in low Earth orbit1 of 2 deciding benchmarks measured |
| Atomic oxygen resistance is good (0.14×). Still needed: darkening under UV and particles (Δα). |
"What the data says" is Space Mushroom's reading of the measured values, not a flight qualification. Deciding benchmarks come from the Benchmark Framework.
What it went through
| Where | ISS, MISSE 2, PEC 2 tray 1 (outside the Quest airlock) |
|---|---|
| When | 2001-08-16 to 2005-07-30 (3.95 years) |
| Atomic oxygen dose | 8.43×10²¹ atoms/cm² |
| Sunlight | 5,000–6,700 equivalent sun hours |
| Temperature | Cycled between −30 °C and 40 °C |
| Also exposed to | Solar UV and charged particle radiation, in vacuum |
How it compares
Materials flown on the same tray, ranked from least to most eroded. PG is number 6 of 40.
| Rank | Material | Compared with Kapton H | Lost in 3.95 years |
|---|---|---|---|
| 4 | AFAmorphous fluoropolymer | 0.066× | 17 µm |
| 5 | FEPFluorinated ethylene propylene | 0.067× | 17 µm |
| 6 | PGPyrolytic graphite | 0.14× | 35 µm |
| 7 | KevlarPoly-(p-phenylene terephthalamide) | 0.21× | 53 µm |
| 8 | Kel-FChlorotrifluoroethylene | 0.28× | 70 µm |
| 25 | Kapton HPolyimide (PMDA) | 1.00× | 253 µm |
How the numbers are calculated
- Erosion yield is NASA's measurement: volume of material removed per oxygen atom.
- Thickness lost = erosion yield × oxygen dose = 4.15×10⁻²⁵ cm³/atom × 8.43×10²¹ atoms/cm² = 0.00350 cm = 35 µm.
- Compared with Kapton H = erosion yield ÷ 3.00×10⁻²⁴ (Kapton H's value on the same flight).
- Film life = 25 µm ÷ 8.9 µm per year, for the same exposure.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0.
spore: passport
id: misse2-pg
spore_version: 0.1
status: measured
org: nasa
dataset: misse2-peace
material:
name: "Pyrolytic graphite"
abbreviation: "PG"
family: Carbon
category: carbon
type: graphite
tags:
environments: [low-earth-orbit]
stresses: [atomic-oxygen, uv, total-radiation-dose, thermal-cycling, vacuum-and-outgassing]
applications: []
exposures:
- environment: low Earth orbit
platform: ISS, MISSE 2, PEC 2 tray 1 (outside the Quest airlock)
start: 2001-08-16
end: 2005-07-30
duration_years: 3.95
atomic_oxygen_fluence: {value: 8.43e21, unit: atoms/cm2}
solar_exposure: {value: "5000-6700", unit: equivalent sun hours}
thermal_cycling: {min_c: -30, max_c: 40, note: nominal base-plate range}
results:
- property: atomic oxygen erosion yield
value: 4.15e-25
unit: cm3/atom
lower_bound: false
sources:
- title: Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit
id: NASA/TM-2008-215490 (Banks, Backus and de Groh, December 2008)
url: https://ntrs.nasa.gov/citations/20090011780
where: Table I; exposure details in section 2.1
license: CC-BY-4.0
Sources
- Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit. NASA/TM-2008-215490 (Banks, Backus and de Groh, December 2008), Table I; exposure details in section 2.1.