1、Designation: E 512 94 (Reapproved 2004)Standard Practice forCombined, Simulated Space Environment Testing ofThermal Control Materials with Electromagnetic andParticulate Radiation1This standard is issued under the fixed designation E 512; the number immediately following the designation indicates th
2、e 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 (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONSpacecraft thermal control coatings may be affect
3、ed 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, acceler
4、ated 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 the
5、re 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
6、and 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 wi
7、th 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 radiat
8、ion, 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,
9、if 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:2E 275 Practice for Describing and Measuring P
10、erformanceof Ultraviolet, Visible, and Near Infrared Spectrophotom-etersE 296 Practice for Ionization Gage Application to SpaceSimulatorsE 349 Terminology Relating to Space SimulationE 434 Test Method for Calorimetric Determination ofHemispherical Emittance and the Ratio of Solar Absorp-tance to Hem
11、ispherical Emittance Using Solar SimulationE 490 Solar Constant and Air Mass Zero Solar SpectralIrradiance TablesE 491 Practice for Solar Simulation for Thermal BalanceTesting of SpacecraftE 903 Test Method for Solar Absorptance, Reflectance, and1This practice is under the jurisdiction of ASTM Commi
12、ttee E21 on SpaceSimulation and Applications of Space Technology and is the direct responsibility ofSubcommittee E21.04 on Space Simulation Test Methods.Current edition approved Sept. 1, 2004. Published September 2004. Originallyapproved in 1973. Last previous edition approved in 1999 as E 512 94 (1
13、999).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 Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO
14、 Box C700, West Conshohocken, PA 19428-2959, United States.Transmittance of Materials Using Integrating Spheres3. Terminology3.1 Definitions:3.1.1 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 E 490) at 1AU (astronomical unit) (1.495 988 2 3 1011m) (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
19、integral 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 surfa
20、ce containingthe point, by the area of that element. Symbol: Ee, E;Ee1=dfe/dA; Unit: watt per square metre, W/m2. (See Termi-nology E 349.)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 s
21、urface in free space at adistance of 1 AU 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 E 349). This definition does not imply that anyspectral distribution of energy in this wa
22、velength band issatisfactory for testing materials.3.1.12 particle flux densitythe number of charged par-ticles incident 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
23、absorptance (as)the fraction of total solarirradiation that is absorbed by a surface. Use the recommendedspectral-solar irradiance data contained in Tables E 490.3.1.15 solar constantthe solar irradiance, at normal inci-dence, on a surface in free space at the earths mean distancefrom the sum of 1 A
24、U. The value is 1353 6 21 W/m2(seeTables E 490).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 (e)the ratio of the thermal-radi
25、ant exitance (flux 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 under consid-eration, then to place the specime
26、n in a vacuum chamber andexpose it to the desirable simulated space environments. Thespecimen temperature is controlled during the period of expo-sure. The radiative property measurements are performed insitu without exposing the specimen to atmospheric pressure,after exposure and before measurement
27、. Unless it has beenestablished that the material under investigation is not affectedby postexposure measurements, the in situ approach is thepreferred method. Usually only the radiative property of solarabsorptance, as, is of interest, and the net result of the test is ameasurement of change in sol
28、ar absorptance, Das. For detaileddiscussions of methods of determining radiative properties, seeTest Method E 903 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 o
29、f the thermal controlmaterials.5. Specimen Analysis5.1 A method 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 (as) and totalhemispheric
30、al emittance (eh). Solar absorptance 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 common
31、ly used. For reflectance measurementsbeyond 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
32、 such measure-ments should be 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 ma
33、intaining the specimens in3The boldface numbers in parentheses refer to the list of references at the end ofthis practice.E 512 94 (2004)2the dark and in vacuum until measured. In the event thatevacuation is impractical, it is desirable that the specimens bemaintained under a positive pressure of dr
34、y argon. Note thatbleaching by 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 situst
35、udies of thermal-radiative property changes. A calorimetricdetermination gives a direct measure of as/e and thereforeindicates the in situ changes in thermal-radiative properties. Ifedoes not change, then the change in as/e shows the change inas. If the electromagnetic radiation source provides a go
36、odmatch to the air-mass zero solar-spectral irradiance, then a willbe equal to as. The limiting factors in calorimetric as/edeterminations are the deviation of the spectral irradianceproduced by the simulated solar source from that of the solarirradiance and the accuracy of the irradiance measuremen
37、t (seeTest Method E 434).5.3.2 In situ measurements 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 suffi
38、ciently fast to makethe posttest measurements 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
39、 Property Analysis:5.4.1 The complete evaluation 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
40、firmly attached tothe substrate in space 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 exp
41、osure. Thismay be important in the study 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 Spec
42、imensX-ray photoelectronspecotroscopy (XPS), 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
43、be present on the speci-mens.5.6 Auxiliary 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 g
44、ive a more complete accountof methods for 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
45、that are joined to the chamber withoutvacuum 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 c
46、hamber to a level in which none of theconstituents can react with the specimen material to affect thevalidity of the tests. This provision implies a pressure nogreater than 1 3 106torr (133 Pa) at the specimen position.6.1.2 It must provide that the specimen area be maintainedas free as possible fro
47、m contaminant gases and vapors. Thesegases 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 P
48、ractice E 296.)6.2 Test Chamber:6.2.1 ConstructionThe specimen test chamber should beconstructed of materials suitable for use in ultra-high vacuum.Metals, glasses, and ceramics are used. Tables E 490 containinformation on materials for vacuum applications. Austenitic-stainless steels, such as Type
49、304, are frequently used forvacuum-chamber construction.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 cr
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