1、Designation:E199707 Designation: E1997 12Standard Practice for theSelection of Spacecraft Materials1This standard is issued under the fixed designation E1997; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The purpose of this practice is to aid engineers, designers, quality and reliability control engineers, materials specialists, and
3、systems designers in the selection and control of materials and processes for spacecraft, external portion of manned systems, orman-tended systems. Spacecraft systems are very different from most other applications. Space environments are very differentfrom terrestrial environments and can dramatica
4、lly alter the performance and survivability of many materials. Reliability, long life,and inability to repair defective systems (or high cost and difficultly of repairs for manned applications) are characteristic of spaceapplications. This practice also is intended to identify materials processes or
5、 applications that may result in degraded orunsatisfactory performance of systems, subsystems, or components. Examples of successful and unsuccessful materials selectionsand uses are given in the appendices.2. Referenced Documents2.1 ASTM Standards:2E595 Test Method for Total Mass Loss and Collected
6、 Volatile Condensable Materials from Outgassing in a VacuumEnvironmentG64 Classification of Resistance to Stress-Corrosion Cracking of Heat-Treatable Aluminum Alloys2.2 Marshall Space Flight Center (MSFC) Standard:MSFC-SPEC-522Design Criteria for Controlling Stress Corrosion CrackingMSFC-STD-3029 Gu
7、idelines to the Selection ofMetallic Materials for Stress Corrosion Cracking Resistance in Sodium Chloride Environments32.3 Military Standards:4MIL-STD-889 Dissimilar MaterialsMIL-HDBK-5 Metallic Materials and Elements for Aerospace Vehicle StructuresMIL-HDBK-17 Properties of Composite Materials2.4
8、European Space Agency (ESA) Standard:PSS-07/QRM-0 Guidelines for Space Materials Selection52.5 Federal Standard:QQ-A-250 Aluminum and Aluminum Alloy Plate and Sheet, Federal Specification for43. Significance and Use3.1 This practice is a guideline for proper materials and process selection and appli
9、cation. The specific application of theseguidelines must take into account contractual agreements, functional performance requirements for particular programs andmissions, and the actual environments and exposures anticipated for each material and the equipment in which the materials areused. Guidel
10、ines are not replacements for careful and informed engineering judgment and evaluations and all possible performanceand design constraints and requirements cannot be foreseen. This practice is limited to unmanned systems and unmanned orexternal portions of manned systems, such as the Space Station.
11、Generally, it is applicable to systems in low earth orbit,1This practice is under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and is the direct responsibility ofSubcommittee E21.05 on Contamination.Current edition approved Dec. 1, 2007. Published J
12、anuary 2008. Originally approved in 1999. Last previous edition approved in 2003 as E199799(2003)1. DOI:10.1520/E1997-07.Current edition approvedApril 1, 2012. Published May 2012. Originally approved in 1999. Last previous edition approved in 2007 as E1997 07. DOI: 10.1520/E1997-12.2For referencedAS
13、TM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. ForAnnual Book ofASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3Marshall Space Flight Center, AL 35812.3Marshall Space Flight Center, AL 35812,
14、or .4Available from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402.4Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.5European Space Agency, 810,
15、Rue Mario-Nikis, 75738 Paris Cedex, France.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately,
16、ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.sync
17、hronous orbit, and interplanetary missions. Although many of the suggestions and cautions are applicable to both unmannedand manned spacecraft, manned systems have additional constraints and requirements for crew safety which may not be addressedadequately in unmanned designs. Because of the added c
18、onstraints and concerns for human-rated systems, these systems are notaddressed in this practice.4. Design Constraints4.1 Orbital EnvironmentThe actual environment in which the equipment is expected to operate must be identified and defined.The exposures and requirements for material performance dif
19、fer for various missions. Environment definition includes defining therange of temperature exposure, number and rate of thermal cycles, extent of vacuum exposure, solar electromagnetic radiationparticulate radiation, (trapped by the earths magnetosphere, solar wind, solar flares, and gamma rays) mic
20、rometeroids, launchloads and vibration, structural loads, and so forth. Materials suitable for one orbit or mission environment may be unsuitable forothers. The applications and requirements will define the suitability of the materials.4.2 Low Earth Orbit (Up to 100 km)Materials in this region could
21、 be exposed to trapped Van Allen belt (ionizing) radiation,solar ultraviolet radiation, corrosive attack by atomic oxygen (A.O.), and more frequent and more extreme thermal cycling andthermal shock as a result of frequent excursions into and out of the earths shadow. Orbital impacts may be a problem
22、 because ofthe large amount of debris in low orbits. Design life in orbit typically is on the order of 5 to 15 years. Inclination of the orbit affectsthe service environment, that is, polar orbits have a different flight profile than equatorial orbits and have different profiles forradiation exposur
23、e.4.3 Synchronous Orbit (35 900 km)Materials in this region are not exposed to significant atomic oxygen or very high energytrapped radiation but may have more exposure to medium energy ionizing electrons and protons, solar flares, and relatively highlevels of electromagnetic solar radiation (ultrav
24、iolet, VUV photons, and X-rays). The number of thermal cycles is less and maybe over a narrower temperature range than low earth orbit. Meteoroids also should be considered but are less likely to be significantcompared to the manmade debris found in low orbits. Design life in orbit typically is 5 to
25、 15 years, with recent designs rangingfrom 10 to 17 years.4.4 Interplanetary (Out-of-Earth Orbit)In addition to the thermal extremes and environments of synchronous orbit, in theinterplanetary environment, temperatures may be more extreme, and micrometeoroids, solar wind, and cosmic rays may be crit
26、ical.Ability to survive and remain functional for many years is important. Probes to the inner plants typically have design lifetimes of5 to 10 years. Those to the outer planets and beyond may have design lifetimes of 15 to 30 years.5. Materials to Avoid5.1 Certain materials are known to be undesira
27、ble and should be avoided no matter what the mission. Others are of concern forcertain missions or of more concern for some missions than others. In general, it is recommended that one avoid the materialsdescribed below:5.1.1 Metals with High Vapor Pressure in Vacuum and Unusual BehaviorsAvoid the u
28、se of metals such as mercury, cadmium,and zinc, either as plating or monolithic metals. It is important to exclude these metals both from the flight equipment and vacuumchambers. If these metals are used in vacuum and heated even moderately, they will vacuum metallize both the cold walls of thechamb
29、er and any cold surfaces on equipment in the chamber.Also, pure tin has the curious property of dendritic growth as a resultof compressive stresses, or thermal or electrical gradients, forming whiskers which can cause shorts in electrical components orbreak off and become conductive contaminants. So
30、me other metals such as cadmium and zinc also can grow whiskers and shouldnot be used.5.1.2 Stress-Corrosion Sensitive MetalsMetals, which are stress-corrosion sensitive, should be avoided. Examples are 2024T6 and 7075 T6 Aluminum, which can be used if heat treated to conditions, such as 2024 T81 an
31、d 7075 T73, which are notstress-corrosion sensitive. Many brasses and some steel alloys also are stress-corrosion sensitive; however, even alloys, which arestress-corrosion sensitive can be used if loaded in compression or if loaded to low sustained tensile stress levels, typically no morethan 25 %
32、of yield strength (see Classification G64 and MSFC-SPEC-522).5.1.3 Materials Forming Galvanic CouplesMaterial combinations, which form galvanic couples greater than 0.5 ev whenexposed to a temperature and humidity controlled environment, such as during fabrication, testing, and storage, should bepro
33、hibited under most circumstances. Providing protection from electrolytes and maintaining them in a controlled environment,such as during fabrication and testing, inhibits galvanic corrosion. Some alloys, such as magnesium, magnesium lithium alloys,and gold, form a galvanic couple with most common st
34、ructural materials and must be protected adequately to prevent creatinggalvanic couples which cause the anodic metal to corrode. Carbon composites are included in the materials, which must beevaluated for galvanic potential, since carbon forms galvanic couples with metals. If there is no electrolyte
35、 present, galvaniccouples greater than 0.5 ev are permissible. Galvanic protection can be obtained by preventing electrolyte from contacting theinterfaces, interposing a dielectric material, or adding a material that is compatible with each of the other materials separately.5.1.4 Materials With Ther
36、mal or Environmental LimitationsMaterials that are weak or brittle at the expected servicetemperature or environment should be avoided. These materials included polymeric materials used at very low or very hightemperatures and some metals used at low temperatures. In this context, “low” can be from
37、-40 to -120C and “high” can be from150 to 200C for polymers. Some materials are readily attacked by certain chemicals or solutions. For example, aluminum alloysshould not be used in strongly basic or acidic environments. Steels, particularly high carbon and ferritic grades, are embrittled byE1997 12
38、2halogens and hydrogen. Silicones are attacked by toluene. Titanium is attacked by methanol.5.1.5 Materials Diffcult to Fabricate or TestMaterials that are difficult to fabricate, form, test, or inspect, or do not have ahistory of consistency of properties or performance, should be avoided. Some mat
39、erials, such as ceramics and most refractorymetals, are relatively difficult to machine or form. Others are difficult to weld by conventional means. Some cannot be formedeasily. Certain applications such as elevated temperature service may require use of ceramics or refractory metals. That should no
40、treduce the need for careful review and functional design of the equipment.All materials must be very carefully evaluated to assuresuccessful, economic fabrication and that the fabricated parts can be inspected easily for hidden defects.5.1.6 Materials That Have Excessive OutgassingIf the materials
41、have high collected volatile condensable materials (CVCM)or total mass loss (TML) when exposed at 125C and tested, they generally are excluded from spacecraft applications. Normalacceptance limits for outgassing according to Test Method E595 are no higher than 1.0 % TMLand no higher than 0.10 % CVCM
42、.Some of these materials release condensates that react adversely with solar radiation or radiation and vacuum and may degradesensitive surfaces. Others can contaminate surfaces or equipment such that functionality is impaired. High mass loss can indicatea loss or properties and functionality in spa
43、ce. Sometimes, a material will have acceptable outgassing per normal requirements,but it may be in a particularly sensitive location, or the outgassing product may have an adverse effect on specific sensitiveequipment. These conditions can require establishing lower levels for acceptable outgassing
44、or may require analysis of outgassedcomponents and evaluation of the acceptability for the specific application.NOTE 1The test is defined as performed at 125C unless clearly stated otherwise; therefore, acceptability is limited to exposures below 125C. Thetest temperature of 125C was assumed to be s
45、ignificantly above the expected operating temperature in service. If expected operating temperatures exceed65 to 70C the test temperature should be increased. It is suggested that the test temperature be at least 30C higher than expected maximum servicetemperature in order to provide material compar
46、isons for TML and CVCM.NOTE 2Metallic materials do not “outgas,” but some metals, such as zinc and cadmium, do exhibit high vapor pressure at relatively low (1000-pi design loads) require specific training to apply theadhesive, including surface preparation and process controls for consistency and e
47、ffective, reliable strength.X2.2 General Usage PrecautionsUsage precautions must be observed to avoid undesirable or unacceptable results and evensystem failures. The importance of thermal sensitivity must not be overlooked. For example, the elastomeric seals, which failedand resulted in the loss of
48、 the Challenger, were operated at a temperature below their known limits. Epoxies often have brittlepoints in the 20 to 60C range. Epoxies should not be used in direct contact with ceramic parts, such as ceramic-cased diodeswhen usage temperatures are low. A flexible intermediate material must be ap
49、plied to prevent brittle fracture of the ceramic.Silicones are normally flexible at temperatures as low as 110C. Flexible silicones should be used rather than epoxies to bondceramics for low temperature applications directly (see 5.1.14). Urethanes tend to become brittle at temperatures of approximately20 to 40C and should be used with great care or avoided at lower temperatures. High temperatures result in significant lossin bond strength for adhesives. Few adhesives retain useful bond or peel strength at temperatures above 60C. So
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1