Atomic oxygen and polymers in low Earth orbit

Vacuum outgassing screening, 4.5 eV ram atomic-oxygen fluence and surface recession of Kapton, PEEK, PTFE and FR-4

Author: nadir lab.
Published: 19 October 2026
Reading time: 2 min
Level: Academic
Tags: Atomic oxygen
Outgassing
Polymers
Kapton
Materials
PocketQube

Abstract

Polymers on the exterior of a PocketQube—solar-panel substrates, Kapton insulation, PEEK spools, UHMWPE burn lines and exposed FR-4 edges—face both high-vacuum volatile condensation and 4.5 eV ram atomic oxygen (AO). We review ECSS-Q-ST-70-02C / ASTM E595 screening limits and compute annual AO fluence and recession depth from 350 to 600 km.

Contents

Vacuum outgassing screening (TML and CVCM)#

Under -Q-ST-70-02C[1] and ASTM E595, polymeric materials heated at $12 5^{\circ} C$ for $24 h$ at $< 7 \times 1 0^{- 3} Pa$ must satisfy[2]:

TML \leq 1.0%, CVCM \leq 0.10%

where Total Mass Loss (TML) measures total volatile release and Collected Volatile Condensable Material (CVCM) measures the fraction that condenses on a collector plate held at $2 5^{\circ} C$ [3]. On a $50 mm$ cube, any silicone adhesive or plasticized PVC wire jacket outgasses directly onto adjacent solar coverglasses and camera lenses within centimetres.

Outgassing screening and atomic-oxygen recession of polymers

Material	TML	CVCM	WVR	RML	Screening	Erosion yield (10⁻²⁴ cm³/atom)	Recession, tumbling face (µm/yr)
FR-4 laminate	0.22	0.00	0.09	0.13	Passes ECSS and ASTM	—	—
G-10 laminate	0.52	0.00	0.16	0.36	Passes ECSS and ASTM	—	—
Polyimide–glass laminate	0.71	0.00	0.40	0.31	Passes ECSS and ASTM	—	—
PEEK, moulded	0.14	0.00	0.05	0.09	Passes ECSS and ASTM	2.99	16
PEI (Ultem), moulded	0.40	0.00	0.32	0.08	Passes ECSS and ASTM	> 3.31	18
ULTEM 1010, FDM (XY)	0.55	0.02	0.39	0.16	Passes ECSS and ASTM	—	—
Polypropylene filament	0.24	0.05	0.03	0.21	Passes ECSS and ASTM	—	—
Polyimide film (Kapton)Erosion-yield reference	0.97	0.00	0.80	0.17	Passes ECSS and ASTM	3	16
PET film (Mylar)	0.24	0.01	0.18	0.06	Passes ECSS and ASTM	3.01	16
PTFE	0.01	0.00	0.02	−0.01	Passes ECSS and ASTM	0.142	0.8
ABS	—	—	—	—	Grade-dependent	1.09	5.8
Polyamide 6	—	—	—	—	Grade-dependent	3.51	19

TML, CVCM, WVR and RML = TML − WVR in per cent; limits 1.0% mass loss and 0.10% CVCM (ECSS-Q-ST-70-02C on RML, ASTM E595 on TML). Recession = erosion yield × fluence, using the ISS ram fluence of MISSE-2 (2.1 × 10²¹ atoms/cm² a year) divided by four for a tumbling face; at 500–550 km the fluence is lower.

4.5 eV atomic oxygen and surface recession#

Photodissociation of $O_{2}$ by solar ultraviolet radiation makes monatomic oxygen ( $O$ ) the dominant neutral species between $200$ and $600 km$ [4]. At an orbital speed $v \approx 7.6 km/s$ , impacting oxygen atoms carry translational energy $\frac{1}{2} m_{O} v^{2} \approx 4.5 eV$ —sufficient to break $C-C$ and $C-H$ bonds. For a material with erosion yield $E_{y}$ ( $cm^{3} / atom$ ) exposed to annual fluence $F$ ( $atoms/cm^{2} \cdot yr$ ), the surface recession depth is[5]:

d = E_{y} \cdot F, F_{tumbling} = \frac{1}{4} n_{AO} (h, F_{10.7}) v T_{yr}

Atomic oxygen fluence and polymer erosion depth at 400 km over 2 year(s) (F10.7 = 140 sfu, ram factor 0.32)

Polymer / coating	Erosion yield E_y (cm³/atom)	Recession depth (µm)	Mass loss (mg/cm²)	Engineering notes
Kapton HN (polyimide)	3.00 × 10⁻²⁴	70.5	10.02	Standard reference material (ASTM E2089); rapid unprotected erosion below 450 km.
FR-4 / Epoxy matrix	2.10 × 10⁻²⁴	49.4	9.14	Glass fibres remain intact after resin matrix erodes, creating a diffuse matte surface.
FEP / PTFE (Teflon)	3.50 × 10⁻²⁵	8.2	1.77	Low atomic-oxygen yield alone, but synergistic VUV + AO accelerates degradation.
PEEK structural polymer	2.30 × 10⁻²⁴	54.1	7.14	Used in antenna deployment spools and insulating standoffs.
SiOx-coated Kapton (130 nm)	2.00 × 10⁻²⁶	0.5	0.07	Passivating silica barrier cuts effective erosion by > 98% outside pinhole defects.

Interactive polymer erosion calculator#

Use the interactive model below to evaluate annual fluence and recession depth across altitude, mission duration and solar activity:

Atomic oxygen fluence and polymer erosion depth at 400 km over 2 year(s) (F10.7 = 140 sfu, ram factor 0.32)

Polymer / coating	Erosion yield E_y (cm³/atom)	Recession depth (µm)	Mass loss (mg/cm²)	Engineering notes
Kapton HN (polyimide)	3.00 × 10⁻²⁴	70.5	10.02	Standard reference material (ASTM E2089); rapid unprotected erosion below 450 km.
FR-4 / Epoxy matrix	2.10 × 10⁻²⁴	49.4	9.14	Glass fibres remain intact after resin matrix erodes, creating a diffuse matte surface.
FEP / PTFE (Teflon)	3.50 × 10⁻²⁵	8.2	1.77	Low atomic-oxygen yield alone, but synergistic VUV + AO accelerates degradation.
PEEK structural polymer	2.30 × 10⁻²⁴	54.1	7.14	Used in antenna deployment spools and insulating standoffs.
SiOx-coated Kapton (130 nm)	2.00 × 10⁻²⁶	0.5	0.07	Passivating silica barrier cuts effective erosion by > 98% outside pinhole defects.