1、Designation: E512 94 (Reapproved 2015)Standard Practice forCombined, Simulated Space Environment Testing ofThermal Control Materials with Electromagnetic andParticulate Radiation1This standard is issued under the fixed designation E512; the number immediately following the designation indicates the
2、year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONSpacecraft thermal control coatings may be affected
3、by exposure to the space environment to theextent that their radiative properties change and the coatings no longer control temperatures withindesired limits. For some coatings, this degradation of properties occurs rapidly; others may take a longtime to degrade. For the latter materials, accelerate
4、d testing is required to permit approximatedetermination of their properties for extended flights. The complexity of the degradation phenomenaand the inability to characterize materials in terms of purity and atomic or molecular defects makelaboratory exposures necessary.It is recognized that there
5、are various techniques of investigation that can be used in spaceenvironment testing. These range in complexity from exposure to ultraviolet radiation in thewavelength range from 50 to 400 nm, with properties measured before and after testing, to combinedenvironmental testing using both particle and
6、 electromagnetic radiation and in situ measurements ofradiative properties. Although flight testing of thermal control coatings is preferred, ground-basedsimulations, which use reliable test methods, are necessary for materials development. These variousapproaches to testing must be considered with
7、respect to the design requirements, mission spaceenvironment, and cost.1. Scope1.1 This practice describes procedures for providing expo-sure of thermal control materials to a simulated space environ-ment comprising the major features of vacuum, electromag-netic radiation, charged particle radiation
8、, and temperaturecontrol.1.2 Broad recommendations relating to spectral reflectancemeasurements are made.1.3 Test parameters and other information that should bereported as an aid in interpreting test results are delineated.1.4 This standard does not purport to address all of thesafety concerns, if
9、any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E275 Practice for Describing and Measuring Perfo
10、rmance ofUltraviolet and Visible SpectrophotometersE296 Practice for Ionization Gage Application to SpaceSimulatorsE349 Terminology Relating to Space SimulationE434 Test Method for Calorimetric Determination of Hemi-spherical Emittance and the Ratio of SolarAbsorptance toHemispherical Emittance Usin
11、g Solar SimulationE490 Standard Solar Constant and Zero Air Mass SolarSpectral Irradiance TablesE491 Practice for Solar Simulation for Thermal BalanceTesting of SpacecraftE903 Test Method for Solar Absorptance, Reflectance, andTransmittance of Materials Using Integrating Spheres3. Terminology3.1 Def
12、initions:1This practice is under the jurisdiction of ASTM Committee E21 on SpaceSimulation andApplications of Space Technology and is the direct responsibility ofSubcommittee E21.04 on Space Simulation Test Methods.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in
13、1973. Last previous edition approved in 2010 as E512 94 (2010).DOI: 10.1520/E0512-94R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summa
14、ry page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 absorbed dosethe amount of energy transferredfrom ionizing radiation to a unit mass of irradiated material.3.1.2 absorbed dose versus depththe profile of
15、 absorbedenergy versus depth into material.3.1.3 bleachingthe decrease in absorption of materialsfollowing irradiation because of a reversal of the damageprocesses. This results in a reflectance greater than that of theinitially damaged material. Also referred to as annealing.3.1.4 equivalent ultrav
16、iolet sun (EUVS)the ratio of thesolar simulation source energy to a near ultraviolet sun for thesame wavelength region of 200 to 400 nm.3.1.5 far ultraviolet (FUV)the wavelength range from 10to 200 nm. Also referred to as vacuum ultraviolet or extremeultraviolet.3.1.6 far ultraviolet sunthe spectral
17、 and energy content ofthe sun in the wavelength range from 10 to 200 nm. Thespectrum is characterized by a continuum spectrum to approxi-mately 160 nm and a line spectrum to 10 nm. The solar energyin the FUV fluctuates and for purposes of irradiation of thermalcontrol coatings, the UV sun is defined
18、 as 0.1 W/m2for thewavelength range from 10 to 200 nm (see Tables E490)at1AU (astronomical unit) (1.495 98821011m) (1).33.1.7 in situwithin the vacuum environment. It may beused to describe measurements performed during irradiation aswell as those performed before and after irradiation.3.1.8 integra
19、l fluxthe total number of particles impingedon a unit area surface for the duration of a test, determined byintegrating the incident particles flux over time. Also referredto as fluence.3.1.9 irradiance at a point on a surfacethe quotient of theradiant flux incident on an element of the surface cont
20、ainingthe point, by the area of that element. Symbol: Ee, E; Ee1=de/dA; Unit: watt per square metre, W/m2. (See Terminol-ogy E349.)3.1.10 near ultravioletthe wavelength range from 200 to400 nm.3.1.11 near ultraviolet sunfor test purposes only, the solarirradiance, at normal incidence, on a surface i
21、n free space at adistance of 1AU from the sun in the wavelength band from 200to 400 nm. Using the standard solar-spectral irradiance, thevalue is 8.73 % of the solar constant or 118 W/m2(seeTerminology E349). This definition does not imply that anyspectral distribution of energy in this wavelength b
22、and issatisfactory for testing materials.3.1.12 particle flux densitythe number of charged particlesincident on a surface per unit area per unit time.3.1.13 reciprocitya term implying that effect of radiationis only a function of absorbed dose and is independent of doserate.3.1.14 solar absorptance
23、(s)the fraction of total solarirradiation that is absorbed by a surface. Use the recommendedspectral-solar irradiance data contained in Tables E490.3.1.15 solar constantthe solar irradiance, at normalincidence, on a surface in free space at the earths meandistance from the sum of 1 AU. The value is
24、1353 6 21W/m2(see Tables E490).3.1.16 synergisticrelating to the cooperative action of twoor more independent causal agents such that their combinedeffect is different than the sum of the effect caused by theindividual agents.3.1.17 thermal emittance ()the ratio of the thermal-radiant exitance (flux
25、 per unit area) of the radiator (specimen)to that of a full radiator (blackbody) at the same temperature.4. Summary of Practice4.1 The most typical approach in performing this test is tomeasure the radiative properties of the specimen underconsideration, then to place the specimen in a vacuum chambe
26、rand expose it to the desirable simulated space environments.The specimen temperature is controlled during the period ofexposure. The radiative property measurements are performedin situ without exposing the specimen to atmospheric pressure,after exposure and before measurement. Unless it has beenes
27、tablished that the material under investigation is not affectedby postexposure measurements, the in situ approach is thepreferred method. Usually only the radiative property of solarabsorptance, s, is of interest, and the net result of the test is ameasurement of change in solar absorptance, s. For
28、detaileddiscussions of methods of determining radiative properties, seeTest Method E903 and Refs. (2), (3), and (4).4.2 The most effective method is to combine the radiationcomponents of the space environments and investigate thesynergistic effects on radiative properties of the thermal controlmater
29、ials.5. Specimen Analysis5.1 Amethod characterizing the behavior of thermal controlmaterials during space environment exposure is through spec-tral reflectance measurements.The two parameters of engineer-ing importance are total solar absorptance (s) and totalhemispherical emittance (h). Solar absor
30、ptance is generallydetermined from spectral reflectance measured under condi-tions of near normal irradiation and hemispherical viewingover the wavelength range from 0.25 to 2.5 m. For thesemeasurements, an integrating sphere with associated spectro-photometer is commonly used. For reflectance measu
31、rementsbeyond 2.5 m, a blackbody cavity or parabolic reflectometeris frequently used.5.2 Postexposure Measurements:5.2.1 Although in situ measurements are necessary, manymeasurements must be performed after removal of the speci-men from the test chamber. The accuracy of such measure-ments should be
32、verified by in situ measurements because ofpossible bleaching.5.2.2 Postexposure measurements of properties should beaccomplished as soon as possible after the exposure. Wheredelays allow the possibility of bleaching, it is necessary tominimize atmospheric effects by maintaining the specimens inthe
33、dark and in vacuum until measured. In the event that3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.E512 94 (2015)2evacuation is impractical, it is desirable that the specimens bemaintained under a positive pressure of dry argon. Note thatbleaching by
34、diffusion of oxygen or nitrogen into the systemhas been observed to occur in the dark, although more slowly,than in the light.5.3 In Situ Analysis:5.3.1 Calorimetric measurements of thermal-radiative prop-erties have received some attention in connection with in situstudies of thermal-radiative prop
35、erty changes. A calorimetricdetermination gives a direct measure of s/ and thereforeindicates the in situ changes in thermal-radiative properties. Ifedoes not change, then the change in s/ shows the change ins. If the electromagnetic radiation source provides a goodmatch to the air-mass zero solar-s
36、pectral irradiance, then a willbe equal to s. The limiting factors in calorimetric s/determinations are the deviation of the spectral irradianceproduced by the simulated solar source from that of the solarirradiance and the accuracy of the irradiance measurement (seeTest Method E434).5.3.2 In situ m
37、easurements allow the determination of thereflectance or absorptance in a vacuum environment. Theenvironment maintained for in situ measurements should haveno effect on the property being measured. The annealing of thespecimen after irradiation may occur sufficiently fast to makethe posttest measure
38、ments misleading. In situ reflectancemeasurements allow the investigator to plot a curve of thechange in thermal radiative properties as a function of theexposure or absorbed dose. Posttest measurements limit thedata to one point at the total dose.5.4 Physical Property Analysis:5.4.1 The complete ev
39、aluation of thermal control coatingsdoes not depend only on thermal-radiative property measure-ments; coatings must have the adhesion and stability requiredfor retention on a specified substrate. One method used toevaluate the ability of the coating to remain firmly attached tothe substrate in space
40、 is through thermal cycling of thespecimens either during or after radiation exposure in avacuum.5.4.2 The loss of mass of thermal control coatings can bemeasured, to provide an indication of the amount of decom-position products leaving the coating during exposure. Thismay be important in the study
41、 of the curing, outgassing, andcontamination potential of thermal control coatings.5.4.3 Vacuum gas analysis (mass spectroscopy or residualgas analysis, RGA) can be used to assess the type andconcentration of decomposition products.5.5 Surface Analysis of SpecimensX-ray photoelectronspecotroscopy (X
42、PS), auger electron spectroscopy, and second-ary ion mass spectrometry (SIMS) are some techniques thatcan be used to determine the composition of materials on thesurface of the specimens. This information can then be used toidentify any contamination that may be present on the speci-mens.5.6 Auxilia
43、ry Methods of Specimen AnalysisSeveral othertechniques for specimen characterization and analysis areavailable to the investigator.As a rule, these are usually used instudies of damage mechanisms rather than engineering tests.They are included in Table 1 to give a more complete accountof methods for
44、 analysis of thermal control surfaces damaged byelectromagnetic or particle irradiation, or both.SIMULATION SYSTEM6. Vacuum System6.1 General DescriptionThe vacuum system shall consistof the specimen test chamber, all other components of thesimulation system that are joined to the chamber withoutvac
45、uum isolation during specimen exposure, and the transitionsections by which these components are joined to the chamber.The vacuum system must perform the following functions:6.1.1 It must provide for a reduction of pressure of atmo-spheric gases in the test chamber to a level in which none of thecon
46、stituents can react with the specimen material to affect thevalidity of the tests. This provision implies a pressure nogreater than 1 106torr (133 Pa) at the specimen position.6.1.2 It must provide that the specimen area be maintainedas free as possible from contaminant gases and vapors. Thesegases
47、and vapors may originate anywhere in the systemincluding from the test specimens themselves.6.1.3 It must promptly trap or remove any volatiles out-gassed from the test specimens.6.1.4 It must provide for accurate pressure measurements inthe chamber. (See Practice E296.)6.2 Test Chamber:6.2.1 Constr
48、uctionThe specimen test chamber should beconstructed of materials suitable for use in ultra-high vacuum.Metals, glasses, and ceramics are used. Tables E490 containinformation on materials for vacuum applications. Austenitic-stainless steels, such as Type 304, are frequently used forvacuum-chamber co
49、nstruction.6.2.1.1 Welding and brazing should be performed in accor-dance with good high-vacuum practice and the temperaturerequirements of the chamber. Materials to be joined must beproperly cleaned so that sound, leaktight, nonporous joints canbe made. Inert gas arc welding (TIG), using helium or argon,and electron beam welding have been used. Brazing materialsand cleaning techniques are discussed in Refs (5) and (6).Welds should be on the vacuum side to eliminate the possibilityof trapping gas in cracks and crevices, thus creating a v
