1、Designation: E 1997 99 (Reapproved 2003)e1Standard Practice for theSelection of Spacecraft Materials1This standard is issued under the fixed designation E 1997; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEKeywords were added editorially in October 2003.1. Scope1.1 The purpose of this practice is to aid engineers, design-ers, quality and
3、 reliability control engineers, materials special-ists, and systems designers in the selection and control ofmaterials and processes for spacecraft, external portion ofmanned systems, or man-tended systems. Spacecraft systemsare very different from most other applications. Space environ-ments are ve
4、ry different from terrestrial environments and candramatically alter the performance and survivability of manymaterials. Reliability, long life, and inability to repair defectivesystems (or high cost and difficultly of repairs for mannedapplications) are characteristic of space applications. Thispra
5、ctice also is intended to identify materials processes orapplications that may result in degraded or unsatisfactoryperformance of systems, subsystems, or components. Ex-amples of successful and unsuccessful materials selections anduses are given in the appendices.2. Referenced Documents2.1 ASTM Stan
6、dards:2E 595 Test Method for Total Mass Loss and CollectedVolatile Condensable Materials from Outgassing in aVacuum EnvironmentG 64 Classification of Resistance to Stress-CorrosionCracking of Heat-Treatable Aluminum Alloys2.2 Marshall Space Flight Center (MSFC) Standard:MSFC-SPEC-522 Design Criteria
7、 for Controlling StressCorrosion Cracking32.3 Military Standards:MIL-STD-889 Dissimilar Materials4MIL-HDBK-5 Metallic Materials and Elements for Aero-space Vehicle Structures42.4 European Space Agency (ESA) Standard:PSS-07/QRM-0 Guidelines for Space Materials Selection52.5 Federal Standard:QQ-A-250
8、Aluminum and Aluminum Alloy Plate andSheet, Federal Specification for43. Significance and Use3.1 This practice is a guideline for proper materials andprocess selection and application. The specific application ofthese guidelines must take into account contractual agree-ments, functional performance
9、requirements for particularprograms and missions, and the actual environments andexposures anticipated for each material and the equipment inwhich the materials are used. Guidelines are not replacementsfor careful and informed engineering judgment and evaluationsand all possible performance and desi
10、gn constraints andrequirements cannot be foreseen. This practice is limited tounmanned systems and unmanned or external portions ofmanned systems, such as the Space Station. Generally, it isapplicable to systems in low earth orbit, synchronous orbit, andinterplanetary missions. Although many of the
11、suggestions andcautions are applicable to both unmanned and manned space-craft, manned systems have additional constraints and require-ments for crew safety which may not be addressed adequatelyin unmanned designs. Because of the added constraints andconcerns for human-rated systems, these systems a
12、re notaddressed in this practice.4. Design Constraints4.1 Orbital EnvironmentThe actual environment in whichthe equipment is expected to operate must be identified anddefined. The exposures and requirements for material perfor-mance differ for various missions. Environment definitionincludes definin
13、g the range of temperature exposure, numberand rate of thermal cycles, extent of vacuum exposure, solarelectromagnetic radiation particulate radiation, (trapped by theearths magnetosphere, solar wind, solar flares, and gammarays) micrometeroids, launch loads and vibration, structuralloads, and so fo
14、rth. Materials suitable for one orbit or mission1This practice is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and is the direct responsibility ofSubcommittee E21.05 on Contamination.Current edition approved Oct. 1, 2003. Published October 2003
15、. Originallyapproved in 1999. Last previous edition approved in 1999 as E 1997 99.2For 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 pag
16、e onthe ASTM website.3Marshall Space Flight Center, AL 35812.4Available from the Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402.5European Space Agency, 810, Rue Mario-Nikis, 75738 Paris Cedex, France.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700
17、, West Conshohocken, PA 19428-2959, United States.environment may be unsuitable for others. The applicationsand requirements will define the suitability of the materials.4.2 Low Earth Orbit (Up to 100 km)Materials in thisregion could be exposed to trapped Van Allen belt (ionizing)radiation, solar ul
18、traviolet radiation, corrosive attack by atomicoxygen (A.O.), and more frequent and more extreme thermalcycling and thermal shock as a result of frequent excursionsinto and out of the earths shadow. Orbital impacts may be aproblem because of the large amount of debris in low orbits.Design life in or
19、bit typically is on the order of 5 to 15 years.Inclination of the orbit affects the service environment, that is,polar orbits have a different flight profile than equatorial orbitsand have different profiles for radiation exposure.4.3 Synchronous Orbit (35 900 km)Materials in this re-gion are not ex
20、posed to significant atomic oxygen or very highenergy trapped radiation but may have more exposure tomedium energy ionizing electrons and protons, solar flares, andrelatively high levels of electromagnetic solar radiation (ultra-violet, VUV photons, and X-rays). The number of thermalcycles is less a
21、nd may be over a narrower temperature rangethan low earth orbit. Meteoroids also should be considered butare less likely to be significant compared to the manmadedebris found in low orbits. Design life in orbit typically is 5 to15 years, with recent designs ranging from 10 to 17 years.4.4 Interplane
22、tary (Out-of-Earth Orbit)In addition to thethermal extremes and environments of synchronous orbit, inthe interplanetary environment, temperatures may be moreextreme, and micrometeoroids, solar wind, and cosmic raysmay be critical. Ability to survive and remain functional formany years is important.
23、Probes to the inner plants typicallyhave design lifetimes of 5 to 10 years. Those to the outerplanets and beyond may have design lifetimes of 15 to 30years.5. Materials to Avoid5.1 Certain materials are known to be undesirable andshould be avoided no matter what the mission. Others are ofconcern for
24、 certain missions or of more concern for somemissions than others. In general, it is recommended that oneavoid the materials described below:5.1.1 Metals with High Vapor Pressure in Vacuum andUnusual BehaviorsAvoid the use of metals such as mercury,cadmium, and zinc, either as plating or monolithic
25、metals. It isimportant to exclude these metals both from the flight equip-ment and vacuum chambers. If these metals are used invacuum and heated even moderately, they will vacuum metal-lize both the cold walls of the chamber and any cold surfaceson equipment in the chamber. Also, pure tin has the cu
26、riousproperty of dendritic growth as a result of compressivestresses, or thermal or electrical gradients, forming whiskerswhich can cause shorts in electrical components or break offand become conductive contaminants. Some other metals havesimilar whisker-growing properties, but not to the extent th
27、attin has.5.1.2 Stress-Corrosion Sensitive MetalsMetals, which arestress-corrosion sensitive, should be avoided. Examples are2024 T6 and 7075 T6 Aluminum, which can be used if heattreated to conditions, such as 2024 T81 and 7075 T73, whichare not stress-corrosion sensitive. Many brasses and some ste
28、elalloys also are stress-corrosion sensitive; however, even alloys,which are stress-corrosion sensitive can be used if loaded incompression or if loaded to low sustained tensile stress levels,typically no more than 25 % of yield strength (see Classifica-tion G 64 and MSFC-SPEC-522).5.1.3 Materials F
29、orming Galvanic CouplesMaterial com-binations, which form galvanic couples greater than 0.5 evwhen exposed to a temperature and humidity controlledenvironment, such as during fabrication, testing, and storage,should be prohibited under most circumstances. Providingprotection from electrolytes and ma
30、intaining them in a con-trolled environment, such as during fabrication and testing,inhibits galvanic corrosion. Some alloys, such as magnesium,magnesium lithium alloys, and gold, form a galvanic couplewith most common structural materials and must be protectedadequately to prevent creating galvanic
31、 couples which causethe anodic metal to corrode. Carbon composites are included inthe materials, which must be evaluated for galvanic potential,since carbon forms galvanic couples with metals. If there is noelectrolyte present, galvanic couples greater than 0.5 ev arepermissible. Galvanic protection
32、 can be obtained by preventingelectrolyte from contacting the interfaces, interposing a dielec-tric material, or adding a material that is compatible with eachof the other materials separately.5.1.4 Materials With Thermal or EnvironmentalLimitationsMaterials that are weak or brittle at the expecteds
33、ervice temperature or environment should be avoided. Thesematerials included polymeric materials used at very low orvery high temperatures and some metals used at low tempera-tures. In this context, “low” can be from -40 to -120C and“high” can be from 150 to 200C for polymers. Some materialsare read
34、ily attacked by certain chemicals or solutions. Forexample, aluminum alloys should not be used in strongly basicor acidic environments. Steels, particularly high carbon andferritic grades, are embrittled by halogens and hydrogen.Silicones are attacked by toluene. Titanium is attacked bymethanol.5.1.
35、5 Materials Diffcult to Fabricate or TestMaterialsthat are difficult to fabricate, form, test, or inspect, or do nothave a history of consistency of properties or performance,should be avoided. Some materials, such as ceramics and mostrefractory metals, are relatively difficult to machine or form.Ot
36、hers are difficult to weld by conventional means. Somecannot be formed easily. All materials must be very carefullyevaluated to assure successful, economic fabrication and thatthe fabricated parts can be inspected easily for hidden defects.5.1.6 Materials That Have Excessive OutgassingIf thematerial
37、s have high collected volatile condensable materials(CVCM) or total mass loss (TML) when exposed at 125C andtested, they generally are excluded from spacecraft applica-tions. Normal acceptance limits for outgassing according toTest Method E 595 are no higher than 1.0 % TML and nohigher than 0.10 % C
38、VCM. Some of these materials releasecondensates that react adversely with solar radiation or radia-tion and vacuum and may degrade sensitive surfaces. Otherscan contaminate surfaces or equipment such that functionalityis impaired. High mass loss can indicate a loss or propertiesand functionality in
39、space. Sometimes, a material will haveE 1997 99 (2003)e12acceptable outgassing per normal requirements, but it may bein a particularly sensitive location, or the outgassing productmay have an adverse effect on specific sensitive equipment.These conditions can require establishing lower levels foracc
40、eptable outgassing or may require analysis of outgassedcomponents and evaluation of the acceptability for the specificapplication.NOTE 1The test is defined as performed at 125C unless clearly statedotherwise; therefore, acceptability is limited to exposures at that tempera-ture or below.NOTE 2Metall
41、ic materials do not “outgas,” but some metals, such aszinc and cadmium, do exhibit high vapor pressure at relatively low(1000-pi design loads) require specifictraining to apply the adhesive, including surface preparationand process controls for consistency and effective, reliablestrength.X2.2 Genera
42、l Usage PrecautionsUsage precautions mustbe observed to avoid undesirable or unacceptable results andeven system failures. The importance of thermal sensitivitymust not be overlooked. For example, the elastomeric seals,which failed and resulted in the loss of the Challenger, wereoperated at a temper
43、ature below their known limits. Epoxiesoften have brittle points in the 20 to 60C range. Epoxiesshould not be used in direct contact with ceramic parts, such asceramic-cased diodes when usage temperatures are low. Aflexible intermediate material must be applied to prevent brittlefracture of the cera
44、mic. Silicones are normally flexible attemperatures as low as 110C. Flexible silicones should beused rather than epoxies to bond ceramics for low temperatureapplications directly (see 5.1.14). Urethanes tend to becomebrittle at temperatures of approximately 20 to 40C andshould be used with great car
45、e or avoided at lower tempera-tures. High temperatures result in significant loss in bondstrength for adhesives. Few adhesives retain useful bond orpeel strength at temperatures above 60C. Some polyimidesmay have useful strengths at temperatures up to 300C. A moretypical adhesive upper use temperatu
46、re is 80 to 100C. If theexpected use temperature is above about 80C, the bondstrengths of adhesives should be verified either from vendortest data or by actual test.NOTE X2.1Outgassing in accordance with Test Method E 595, atstandard conditions, is performed at 125C. If operating temperatures areexp
47、ected to exceed 120 to 125C, the material should be tested foroutgassing at or above the expected operating temperature.X2.3 Mechanical and Physical PropertiesNormally, sup-pliers provide data sheets that list material properties ofadhesives. This information is not directly transferable tospecifica
48、tions and standards. In fact, the vendor data sheetsusually have a disclaimer that the properties are typical onlyand not to be used for specifications. Users are advised toperform tests of properties of interest and to use those values togenerate specifications.X2.4 Corrosion and StabilitySome adhe
49、sives are sensi-tive to contact with organic materials or certain metals. Forexample, silicones can be degraded by contact with aminescommonly used as a curing agent in epoxies. RTV silicones,which cure by reaction with moisture, cannot be cured faster byheating them. Such heating reduces the humidity at theadhesive and inhibits cure. If heated to too high a temperatureduring cure, the silicone may even be damaged and never cureproperly. It is inadvisable to use silicones, which requiremoisture to cure properly, to bond large area sandwich bonds
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