ASTM E512-94(2020)
(Practice)Standard Practice for Combined, Simulated Space Environment Testing of Thermal Control Materials with Electromagnetic and Particulate Radiation
Standard Practice for Combined, Simulated Space Environment Testing of Thermal Control Materials with Electromagnetic and Particulate Radiation
ABSTRACT
This practice describes the standard procedures for providing exposure of thermal control materials to a simulated space environment comprising of the major features of vacuum, electromagnetic radiation, charged particle radiation, and temperature control. Broad recommendations relating to spectral reflectance measurements, as well as test parameters and other information that should be reported as an aid in interpreting test results are delineated. Specifications are provided for the vacuum system, solar simulator, charged particle sources, safety precautions, and data interpretation.
SCOPE
1.1 This practice describes procedures for providing exposure of thermal control materials to a simulated space environment comprising the major features of vacuum, electromagnetic radiation, charged particle radiation, and temperature control.
1.2 Broad recommendations relating to spectral reflectance measurements are made.
1.3 Test parameters and other information that should be reported as an aid in interpreting test results are delineated.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E512 − 94 (Reapproved 2020)
Standard Practice for
Combined, Simulated Space Environment Testing of
Thermal Control Materials with Electromagnetic and
Particulate Radiation
This standard is issued under the fixed designation E512; 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.
INTRODUCTION
Spacecraft thermal control coatings may be affected by exposure to the space environment to the
extent that their radiative properties change and the coatings no longer control temperatures within
desiredlimits.Forsomecoatings,thisdegradationofpropertiesoccursrapidly;othersmaytakealong
time to degrade. For the latter materials, accelerated testing is required to permit approximate
determination of their properties for extended flights. The complexity of the degradation phenomena
and the inability to characterize materials in terms of purity and atomic or molecular defects make
laboratory exposures necessary.
It is recognized that there are various techniques of investigation that can be used in space
environment testing. These range in complexity from exposure to ultraviolet radiation in the
wavelength range from 50 to 400 nm, with properties measured before and after testing, to combined
environmental testing using both particle and electromagnetic radiation and in situ measurements of
radiative properties. Although flight testing of thermal control coatings is preferred, ground-based
simulations, which use reliable test methods, are necessary for materials development. These various
approaches to testing must be considered with respect to the design requirements, mission space
environment, and cost.
1. Scope 1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This practice describes procedures for providing expo-
ization established in the Decision on Principles for the
sure of thermal control materials to a simulated space environ-
Development of International Standards, Guides and Recom-
ment comprising the major features of vacuum, electromag-
mendations issued by the World Trade Organization Technical
netic radiation, charged particle radiation, and temperature
Barriers to Trade (TBT) Committee.
control.
1.2 Broad recommendations relating to spectral reflectance
2. Referenced Documents
measurements are made.
2.1 ASTM Standards:
1.3 Test parameters and other information that should be
E275PracticeforDescribingandMeasuringPerformanceof
reported as an aid in interpreting test results are delineated.
Ultraviolet and Visible Spectrophotometers
1.4 This standard does not purport to address all of the E296Practice for Ionization Gage Application to Space
Simulators
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- E349Terminology Relating to Space Simulation
E434Test Method for Calorimetric Determination of Hemi-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. sphericalEmittanceandtheRatioofSolarAbsorptanceto
Hemispherical Emittance Using Solar Simulation
E490Standard Solar Constant and Zero Air Mass Solar
This practice is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of SpaceTechnology and is the direct responsibility of
Subcommittee E21.04 on Space Simulation Test Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2020. Published December 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approvedin1973.Lastpreviouseditionapprovedin2015asE512–94(2015).DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E0512-94R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E512 − 94 (2020)
Spectral Irradiance Tables 3.1.12 particlefluxdensity—thenumberofchargedparticles
E491Practice for Solar Simulation for Thermal Balance incident on a surface per unit area per unit time.
Testing of Spacecraft
3.1.13 reciprocity—a term implying that effect of radiation
E903Test Method for Solar Absorptance, Reflectance, and
is only a function of absorbed dose and is independent of dose
Transmittance of Materials Using Integrating Spheres
rate.
3.1.14 solar absorptance (α )—the fraction of total solar
3. Terminology s
irradiationthatisabsorbedbyasurface.Usetherecommended
3.1 Definitions:
spectral-solar irradiance data contained in Tables E490.
3.1.1 absorbed dose—the amount of energy transferred
3.1.15 solar constant—the solar irradiance, at normal
from ionizing radiation to a unit mass of irradiated material.
incidence, on a surface in free space at the earth’s mean
3.1.2 absorbed dose versus depth—the profile of absorbed
distance from the sum of 1 AU. The value is 1353 6 21
energy versus depth into material.
W/m (see Tables E490).
3.1.3 bleaching—the decrease in absorption of materials
3.1.16 synergistic—relatingtothecooperativeactionoftwo
following irradiation because of a reversal of the damage
or more independent causal agents such that their combined
processes. This results in a reflectance greater than that of the
effect is different than the sum of the effect caused by the
initially damaged material. Also referred to as annealing.
individual agents.
3.1.4 equivalent ultraviolet sun (EUVS)—the ratio of the
3.1.17 thermal emittance (ε)—the ratio of the thermal-
solar simulation source energy to a near ultraviolet sun for the
radiant exitance (flux per unit area) of the radiator (specimen)
same wavelength region of 200 to 400 nm.
to that of a full radiator (blackbody) at the same temperature.
3.1.5 far ultraviolet (FUV)—the wavelength range from 10
to 200 nm. Also referred to as vacuum ultraviolet or extreme
4. Summary of Practice
ultraviolet.
4.1 The most typical approach in performing this test is to
3.1.6 far ultraviolet sun—the spectral and energy content of
measure the radiative properties of the specimen under
the sun in the wavelength range from 10 to 200 nm. The
consideration,thentoplacethespecimeninavacuumchamber
spectrumischaracterizedbyacontinuumspectrumtoapproxi-
and expose it to the desirable simulated space environments.
mately 160 nm and a line spectrum to 10 nm.The solar energy
The specimen temperature is controlled during the period of
intheFUVfluctuatesandforpurposesofirradiationofthermal
exposure. The radiative property measurements are performed
control coatings, the UV sun is defined as 0.1 W/m for the
insituwithoutexposingthespecimentoatmosphericpressure,
wavelength range from 10 to 200 nm (see Tables E490)at1
11 3
after exposure and before measurement. Unless it has been
AU (astronomical unit) (1.4959882×10 m) (1).
established that the material under investigation is not affected
3.1.7 in situ—within the vacuum environment. It may be
by postexposure measurements, the in situ approach is the
usedtodescribemeasurementsperformedduringirradiationas
preferred method. Usually only the radiative property of solar
well as those performed before and after irradiation.
absorptance, α , is of interest, and the net result of the test is a
s
3.1.8 integral flux—the total number of particles impinged
measurement of change in solar absorptance, ∆α . For detailed
s
on a unit area surface for the duration of a test, determined by
discussionsofmethodsofdeterminingradiativeproperties,see
integrating the incident particle’s flux over time.Also referred
Test Method E903 and Refs. (2), (3), and (4).
to as fluence.
4.2 The most effective method is to combine the radiation
3.1.9 irradiance at a point on a surface—thequotientofthe
components of the space environments and investigate the
radiant flux incident on an element of the surface containing
synergisticeffectsonradiativepropertiesofthethermalcontrol
the point, by the area of that element. Symbol: E , E; E
e e
materials.
=dφ /dA; Unit: watt per square metre, W/m . (See Terminol-
e
ogy E349.)
5. Specimen Analysis
3.1.10 near ultraviolet—the wavelength range from 200 to
5.1 Amethodcharacterizingthebehaviorofthermalcontrol
400 nm.
materials during space environment exposure is through spec-
3.1.11 near ultraviolet sun—fortestpurposesonly,thesolar
tralreflectancemeasurements.Thetwoparametersofengineer-
irradiance, at normal incidence, on a surface in free space at a
ing importance are total solar absorptance (α ) and total
s
distanceof1AUfromthesuninthewavelengthbandfrom200
hemispherical emittance (ε ). Solar absorptance is generally
h
to 400 nm. Using the standard solar-spectral irradiance, the
determined from spectral reflectance measured under condi-
value is 8.73% of the solar constant or 118 W/m (see
tions of near normal irradiation and hemispherical viewing
Terminology E349). This definition does not imply that any
over the wavelength range from 0.25 to 2.5 µm. For these
spectral distribution of energy in this wavelength band is
measurements, an integrating sphere with associated spectro-
satisfactory for testing materials.
photometer is commonly used. For reflectance measurements
beyond 2.5 µm, a blackbody cavity or parabolic reflectometer
is frequently used.
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this practice. 5.2 Postexposure Measurements:
E512 − 94 (2020)
5.2.1 Although in situ measurements are necessary, many ary ion mass spectrometry (SIMS) are some techniques that
measurements must be performed after removal of the speci- can be used to determine the composition of materials on the
men from the test chamber. The accuracy of such measure- surface of the specimens.This information can then be used to
ments should be verified by in situ measurements because of identify any contamination that may be present on the speci-
possible bleaching. mens.
5.2.2 Postexposure measurements of properties should be
5.6 Auxiliary Methods of Specimen Analysis—Several other
accomplished as soon as possible after the exposure. Where
techniques for specimen characterization and analysis are
delays allow the possibility of bleaching, it is necessary to
availabletotheinvestigator.Asarule,theseareusuallyusedin
minimize atmospheric effects by maintaining the specimens in
studies of damage mechanisms rather than engineering tests.
the dark and in vacuum until measured. In the event that
They are included in Table 1 to give a more complete account
evacuation is impractical, it is desirable that the specimens be
ofmethodsforanalysisofthermalcontrolsurfacesdamagedby
maintained under a positive pressure of dry argon. Note that
electromagnetic or particle irradiation, or both.
bleaching by diffusion of oxygen or nitrogen into the system
has been observed to occur in the dark, although more slowly, SIMULATION SYSTEM
than in the light.
6. Vacuum System
5.3 In Situ Analysis:
5.3.1 Calorimetric measurements of thermal-radiative prop-
6.1 General Description—The vacuum system shall consist
erties have received some attention in connection with in situ
of the specimen test chamber, all other components of the
studies of thermal-radiative property changes. A calorimetric
simulation system that are joined to the chamber without
determination gives a direct measure of α /ε and therefore
vacuum isolation during specimen exposure, and the transition
s
indicates the in situ changes in thermal-radiative properties. If
sectionsbywhichthesecomponentsarejoinedtothechamber.
edoes not change, then the change in α /ε shows the change in
The vacuum system must perform the following functions:
s
α . If the electromagnetic radiation source provides a good
s 6.1.1 It must provide for a reduction of pressure of atmo-
matchtotheair-masszerosolar-spectralirradiance,then awill
sphericgasesinthetestchambertoalevelinwhichnoneofthe
be equal to α . The limiting factors in calorimetric α /ε
s s constituents can react with the specimen material to affect the
determinations are the deviation of the spectral irradiance
validity of the tests. This provision implies a pressure no
−6
produced by the simulated solar source from that of the solar
greater than 1×10 torr (133 µPa) at the specimen position.
irradianceandtheaccuracyoftheirradiancemeasurement(see
6.1.2 It must provide that the specimen area be maintained
Test Method E434).
as free as possible from contaminant gases and vapors. These
5.3.2 In situ measurements allow the determination of the
gases and vapors may originate anywhere in the system
reflectance or absorptance in a vacuum environment. The
including from the test specimens themselves.
environment maintained for in situ measurements should have
6.1.3 It must promptly trap or remove any volatiles out-
noeffectonthepropertybeingmeasured.Theannealingofthe
gassed from the test specimens.
specimen after irradiation may occur sufficiently fast to make
6.1.4 Itmustprovideforaccuratepressuremeasurementsin
the posttest measurements misleading. In situ reflectance
the chamber. (See Practice E296.)
measurements allow the investigator to plot a curve of the
6.2 Test Chamber:
change in thermal radiative properties as a function of the
6.2.1 Construction—The specimen test chamber should be
exposure or absorbed dose. Posttest measurements limit the
constructed of materials suitable for use in ultra-high vacuum.
data to one point at the total dose.
Metals, glasses, and ceramics are used. Tables E490 contain
5.4 Physical Property Analysis:
information on materials for vacuum applications. Austenitic-
5.4.1 The complete evaluation of thermal control coatings
stainless steels, such as Type 304, are frequently used for
does not depend only on thermal-radiative property measure-
vacuum-chamber construction.
ments; coatings must have the adhesion and stability required
6.2.1.1 Welding and brazing should be performed in accor-
for retention on a specified substrate. One method used to
dance with good high-vacuum practice and the temperature
evaluate the ability of the coating to remain firmly attached to
requirements of the chamber. Materials to be joined must be
the substrate in space is through thermal cycling of the
properly cleaned so that sound, leaktight, nonporous joints can
specimens either during or after radiation exposure in a
be made. Inert gas arc welding (
...
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