ASTM E2089-00(2006)
(Practice)Standard Practices for Ground Laboratory Atomic Oxygen Interaction Evaluation of Materials for Space Applications
Standard Practices for Ground Laboratory Atomic Oxygen Interaction Evaluation of Materials for Space Applications
SIGNIFICANCE AND USE
These practices enable the following information to be available:
3.1.1 Material atomic oxygen erosion characteristics.
3.1.2 An atomic oxygen erosion comparison of four well-characterized polymers.
The resulting data are useful to:
3.2.1 Compare the atomic oxygen durability of spacecraft materials exposed to the low Earth orbital environment.
3.2.2 Compare the atomic oxygen erosion behavior between various ground laboratory facilities.
3.2.3 Compare the atomic oxygen erosion behavior between ground laboratory facilities and in-space exposure.
3.2.4 Screen materials being considered for low Earth orbital spacecraft application. However, caution should be exercised in attempting to predict in-space behavior based on ground laboratory testing because of differences in exposure environment and synergistic effects.
SCOPE
1.1 The intent of these practices is to define atomic oxygen exposure procedures that are intended to minimize variability in results within any specific atomic oxygen exposure facility as well as contribute to the understanding of the differences in the response of materials when tested in different facilities.
1.2 These practices are not intended to specify any particular type of atomic oxygen exposure facility but simply specify procedures that can be applied to a wide variety of facilities.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.3 The values stated in SI units are to be regarded as the standard.
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Designation: E2089 − 00(Reapproved 2006)
Standard Practices for
Ground Laboratory Atomic Oxygen Interaction Evaluation of
Materials for Space Applications
This standard is issued under the fixed designation E2089; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.6 witness materials or samples—materials or samples
used to measure the effective atomic oxygen flux or fluence.
1.1 The intent of these practices is to define atomic oxygen
exposure procedures that are intended to minimize variability 2.2 Symbols:
in results within any specific atomic oxygen exposure facility
A = exposed area of the witness sample, cm
k
as well as contribute to the understanding of the differences in
A = exposed area of the test sample, cm
s
the response of materials when tested in different facilities.
E = in-space erosion yield of the witness material, cm /
k
1.2 These practices are not intended to specify any particu-
atom
lar type of atomic oxygen exposure facility but simply specify
E = erosion yield of the test material, cm /atom
s
procedures that can be applied to a wide variety of facilities.
f = effective flux, atoms/cm /s
k
F = effective fluence, total atoms/cm
k
1.3 The values stated in SI units are to be regarded as the
∆M = mass loss of the witness coupon, g
k
standard.
1.4 This standard does not purport to address all of the 3. Significance and Use
safety concerns, if any, associated with its use. It is the
3.1 These practices enable the following information to be
responsibility of the user of this standard to establish appro-
available:
priate safety and health practices and determine the applica-
3.1.1 Material atomic oxygen erosion characteristics.
bility of regulatory limitations prior to use.
3.1.2 An atomic oxygen erosion comparison of four well-
characterized polymers.
2. Terminology
3.2 The resulting data are useful to:
2.1 Definitions:
3.2.1 Compare the atomic oxygen durability of spacecraft
2.1.1 atomic oxygen erosion yield—thevolumeofamaterial
materials exposed to the low Earth orbital environment.
that is eroded by atomic oxygen per incident oxygen atom
3.2.2 Comparetheatomicoxygenerosionbehaviorbetween
reported in cm /atom.
various ground laboratory facilities.
2.1.2 atomic oxygen fluence—the arrival of atomic oxygen
3.2.3 Comparetheatomicoxygenerosionbehaviorbetween
to a surface reported in atoms/cm
ground laboratory facilities and in-space exposure.
2.1.3 atomic oxygen flux—the arrival rate of atomic oxygen 3.2.4 Screen materials being considered for low Earth
−2 −1
to a surface reported in atoms·cm ·s .
orbital spacecraft application. However, caution should be
exercised in attempting to predict in-space behavior based on
2.1.4 effective atomic oxygen fluence—the total arrival of
ground laboratory testing because of differences in exposure
atomic oxygen to a surface reported in atoms/cm , which
environment and synergistic effects.
would cause the observed amount of erosion if the sample was
exposed in low Earth orbit.
4. Test Specimen
2.1.5 effective atomic oxygen flux—thearrivalrateofatomic
4.1 In addition to the material to be evaluated for atomic
−2 −1
oxygen to a surface reported in atoms·cm ·s , which would
oxygen interaction, the following four standard witness mate-
cause the observed amount of erosion if the sample was
rials should be exposed in the same facility using the same
exposed in low Earth orbit.
operating conditions and duration exposure within a factor of
3, as the test material: Kapton polyimide H or HN, TFE-
fluorocarbon fluorinated ethylene propylene (FEP), low-
These practices are under the jurisdiction of ASTM Committee E21 on Space
Simulation and Applications of Space Technology and are the direct responsibility
density polyethylene (PE), and pyrolytic graphite (PG). The
of Subcommittee E21.04 on Space Simulation Test Methods. −2 −1
atomic oxygen effective flux (in atoms·cm ·s ) and effective
Current edition approved April 1, 2006. Published April 2006. Originally
fluence (in atoms/cm ) for polyimide Kapton H or HN should
approved in 2000. Last previous edition approved in 2000 as E2089–00. DOI:
10.1520/E2089-00R06. be reported along with the mass or thickness loss relative to
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2089 − 00 (2006)
polyimide Kapton H or HN for the test material, TFE- atomic oxygen source, it is likely that electromagnetic interac-
fluorocarbon FEP, PE, and PG. For atomic oxygen interaction tions could take place between the metal and the plasma that
21 2
testing at effective fluences beyond 2 × 10 atoms/cm , couldcauseanomalousatomicoxygenfluxesorshieldingfrom
polyimide Kapton H should be used and not Kapton HN charged species, or both. It is important to expose the four
becauseKaptonHNcontainsatomicoxygenresistantinorganic standardwitnesscouponsinthisconfigurationbeforeanyother
particles which begin to protect the underlying polyimide thus testing to determine the effects of the masking on the atomic
resulting in incorrect fluence prediction. oxygen flux.
5.3.2 Cladding—Samples which are coated with protective
4.2 It is not necessary to test the four standard witness
coatings on one side can be clad together by means of
samples for each material exposure if previous data exists at
adhesivestoallowtheprotectivecoatingtobeexposedonboth
the same exposure conditions and if the fluence for the test
sides of the sample. The use of thin polyester adhesives (or
sampleiswithinafactorof3ofthestandardwitnessexposure.
other non-silicone adhesive) is recommended to perform such
When possible, the recommended standard witness polymer
cladding. The use of silicone adhesives should be avoided
materials should be 0.05 mm thick and of a diameter greater
because of potential silicone contamination of the sample.
than 5 mm. It is recommended that the pyrolytic graphite
Although cladding allows samples to be tested with the
witness sample be 2 mm thick and of a diameter greater than
protectivecoatingsonbothfaces,edgeexposureofthesamples
5 mm. High-fluence tests, which may erode through the full
and their adhesive does occur and should be accounted for in
thickness of the standard polymer witness, can use the recom-
calculating erosion characteristics of the desired surfaces.
mended thickness sample materials by stacking several layers
of the polymer on top of each other.
5.4 Dehydration and Outgassing (for Samples Undergoing
Weight Measurement)—Because most nonmetals and nonce-
5. Procedure
ramic materials contain significant fractional quantities of
water or other volatiles, or both, it is recommended that these
5.1 Sample Preparation:
types of materials be vacuum-dehydrated before weighing to
5.1.1 Cleaning:
eliminate errors in weight because of moisture loss. Dehydrate
5.1.1.1 The samples to be evaluated for atomic oxygen
samples of a thickness less than or equal to 0.127 mm (5 mils)
interactions should be chemically representative of materials
in a vacuum of a pressure less than 200 millitorr for a duration
that would be used in space.Thus, the surface chemistry of the
of 48 h before sample weighing to ensure that the samples
samples should not be altered by exposure to chemicals or
retain negligible absorbed water. Dehydrate and weigh thicker
cleaningsolutionswhichwouldnotberepresentativelyusedon
samples periodically until weight loss indicates that no further
the functional materials to be used in space.
water is being lost. Dehydrate multiple samples in the same
5.1.1.2 Wiping samples or washing them may significantly
vacuum chamber provided they do not cross-contaminate each
alter surface chemistry and atomic oxygen protection charac-
other,andthattheyarenotofsufficientquantitysoastoinhibit
teristics of materials, and is therefore not recommended.
uniform dehydration of all the samples.
However, if the typical use in space will require preflight
solventcleaning,thenperformsuchcleaningtosimulateactual
5.5 Weighing—Because hydration occurs quickly after re-
surface conditions expected.
moval of samples from vacuum, weighing the samples should
occurwithinfiveminutesofremovalfromvacuumdehydration
5.2 Handling—The atomic oxygen durability of materials
chambers. Reduction of uncertainty associated with moisture
withprotectivecoatingsmaybesignificantlyalteredasaresult
uptakecanbeminimizedbyweighingthesamplesatmeasured
of mechanical damage associated with handling. In addition,
intervals following removal from vacuum and back extrapo-
unprotected materials can become contaminated by handling,
lating to the mass at time of removal from vacuum. Weigh
resulting in anomalous consequences of atomic oxygen expo-
samples using a balance whose sensitivity is capable of
sure. It is recommended that samples be handled such as to
measuring the mass loss of the atomic oxygen fluence witness
minimize abrasion, contamination and flexure. The use of soft
samples. For 2.54-cm-diameter by 0.127-mm-thick Kapton H
fluoropolymer tweezers is recommended for handling poly-
polyimide fluence witness samples, a balance sensitivity 1 mg
meric films with protective coatings. For samples too heavy to
19 2
is acceptable for effective fluences of at least 10 atoms/cm .
be safely held with tweezers, use clean vinyl, latex, or other
Weigh the samples at room temperature (20 to 25°C). If the
gloves which will not allow finger oils to soak through and
temperature is outside this range, measure and record at the
which are lint-free to carefully handle the samples.
time of weighing.
5.3 Exposure Area Control:
5.6 Effective Fluence Prediction:
5.3.1 Masking—Frequently it is desirable to limit the expo-
5.6.1 Fluence Witness Samples:
sureofatomicoxygentoonesideofamaterialoralimitedarea
on one side of the material. This can be done by wrapping 5.6.1.1 Ifthetestsampleisamaterialthatdoesnothaveany
metalfoil(suchasaluminumfoil)aroundthesample,covering protective coating, then use polyimide Kapton H or HN
anareawithasacrificialpolymer(suchasKapton),orbyusing samples to determine the effective atomic oxygen fluence. If
glass to cover areas not to be exposed. It is recommended that the test sample has an atomic oxygen protective coating, then
the protective covering be in intimate contact with the material test an unprotected sample of the substrate material as well.
to prevent partial exposure of the masked areas. When using The unprotected sample can also be used to determine the
metal foil within the RF or microwave excitation region of an effective atomic oxygen fluence provided that in-space erosion
E2089 − 00 (2006)
yield data is available. If such in-space data is not available, one sample at a time for weighing. The rest should remain
then use a sample of polyimide Kapton H or HN should be under vacuum to minimize rehydration mass increases. When
used for determination of effective atomic oxygen fluence witness samples are of the same chemistry as the substrate of
−24 3
assuming an in-space erosion yield of 3.0 × 10 cm /atom. protected samples, it is important to weigh both samples as
close as possible to the same time interval after removal from
5.6.1.2 It is recommended that where physically possible,
vacuum.
the atomic oxygen fluence witness material be exposed to
atomic oxygen simultaneously with the test samples to enable 5.6.4.2 Thickness Loss—Witness coupon material loss can
calculation of the effective atomic oxygen fluence. If chamber also be measured using various surface profiling techniques if
geometry prevents this, expose a fluence witness coupon just the exposure area is too small for accurate weight measure-
prior to or immediately after the test sample. If high-fluence ments to be taken. Profiling can be accomplished by stylus
exposureisnecessary,quiteoftenpolymericsheetsaretoothin profiling,scanningatomicforcemicroscopy,orotherrecession
to survive long exposures. Therefore, thick coupons of poly- measurement techniques. Take care when exposing samples to
imide or graphite are suggested to be used for high-fluence atomic oxygen which will be subsequently used for profiling
weight or thickness loss measurements. The atomic oxygen measurements that a portion of the original surface is kept
erosionyieldofpyrolyticgraphiterelativetopolyimideKapton intact and that a clear step exists between the original surface
H or HN is different in some ground laboratory facilities than and the atomic oxygen exposed portion. This requires that a
in space. Therefore, it is necessary to convert the mass loss or thin (<0.2 mm thick) removable mask be used that is in
thicknesslossofthepyrolyticgraphitetotheequivalentlossof intimate contact with the surface during the atomic oxygen
polyimide Kapton H. This can be accomplished by simultane-
exposure.
ous or sequential exposure of pyrolytic graphite and the
Kapton,andwillenabletheeffectivefluencetobecalculatedin
6. Calculation
terms of Kapton effective fluence, which is the accepted
6.1 Atomic Oxygen Kapton Effective Fluence Determina-
standard.
tion:
5.6.1.3 It is recommended that, periodically, samples of
6.1.1 Measurement of absolute fluence in ground laboratory
Kapton H or HN, TFE-fluorocarbon FEP, polyethylene, and
facilities is typically difficult to perform. In addition, such
pyrolytic graphite be exposed to atomic oxygen in the test
measurements do not reliably predict in-space durability be-
chamber to verify operational consistency and to allow com-
cause of differences in erosion yields in the ground laboratory
parisons to be made between this test facility, space, and other
facilitycomparedtoin-space.Thereislikelytobeasubstantial
ground-basedsystems.Reportthisdataalongwithanytestdata
dependence of erosion yield upon energy of the oxygen atoms,
so that test results can be compared more easily.
which is also material-dependent.
5.6.2 Test, Standard Witness, and Fluence Witness Sample
6.1.2 To assist in the prediction of in-space performance
Position and Orientation—Facilitiestypicallyexperiencesome
based on ground laboratory atomic oxygen testing, it is
spatial flux variation depending on how the atomic oxygen is
desirable,tomeasureaneffectivefluenceforthematerialbeing
formed. Minimization of errors in effective atomic oxygen
tested using a comparison of mass or thickness loss.
fluence will be achieved if witness samples are placed as close
6.1.3 Ifin-spaceatomicoxygenerosiondataisnotavailable
as possible to the same location as the test sample, and that the
for the material being teste
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