ASTM E1997-15(2021)
(Practice)Standard Practice for the Selection of Spacecraft Materials
Standard Practice for the Selection of Spacecraft Materials
SIGNIFICANCE AND USE
3.1 This practice is a guideline for proper materials and process selection and application. The specific application of these guidelines must take into account contractual agreements, functional performance requirements for particular programs and missions, and the actual environments and exposures anticipated for each material and the equipment in which the materials are used. Guidelines are not replacements for careful and informed engineering judgment and evaluations and all possible performance and design constraints and requirements cannot be foreseen. This practice is limited to unmanned systems and unmanned or external portions of manned systems, such as the Space Station. Generally, it is applicable to systems in low earth orbit, synchronous orbit, and interplanetary missions. Although many of the suggestions and cautions are applicable to both unmanned and manned spacecraft, manned systems have additional constraints and requirements for crew safety which may not be addressed adequately in unmanned designs. Because of the added constraints and concerns for human-rated systems, these systems are not addressed in this practice.
SCOPE
1.1 The purpose of this practice is to aid engineers, designers, quality and reliability control engineers, materials specialists, and systems designers in the selection and control of materials and processes for spacecraft, external portion of manned systems, or man-tended systems. Spacecraft systems are very different from most other applications. Space environments are very different from terrestrial environments and can dramatically 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 space applications. This practice also is intended to identify materials processes or applications that may result in degraded or unsatisfactory performance of systems, subsystems, or components. Examples of successful and unsuccessful materials selections and uses are given in the appendices.
1.2 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.
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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: E1997 − 15 (Reapproved 2021)
Standard Practice for the
Selection of Spacecraft Materials
This standard is issued under the fixed designation E1997; 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.
1. Scope Sodium Chloride Environments
2.3 Military Standards:
1.1 The purpose of this practice is to aid engineers,
MIL-STD-889Dissimilar Materials
designers, quality and reliability control engineers, materials
MIL-HDBK-5Metallic Materials and Elements for Aero-
specialists, and systems designers in the selection and control
space Vehicle Structures
of materials and processes for spacecraft, external portion of
MIL-HDBK-17Properties of Composite Materials
manned systems, or man-tended systems. Spacecraft systems
2.4 European Space Agency (ESA) Standard:
areverydifferentfrommostotherapplications.Spaceenviron-
PSS-07/QRM-0Guidelines for Space Materials Selection
ments are very different from terrestrial environments and can
2.5 Federal Standard:
dramatically alter the performance and survivability of many
QQ-A-250 Aluminum and Aluminum Alloy Plate and
materials.Reliability,longlife,andinabilitytorepairdefective
Sheet, Federal Specification for
systems (or high cost and difficultly of repairs for manned
applications) are characteristic of space applications. This
3. Significance and Use
practice also is intended to identify materials processes or
applications that may result in degraded or unsatisfactory 3.1 This practice is a guideline for proper materials and
process selection and application. The specific application of
performance of systems, subsystems, or components. Ex-
amplesofsuccessfulandunsuccessfulmaterialsselectionsand these guidelines must take into account contractual
agreements, functional performance requirements for particu-
uses are given in the appendices.
lar programs and missions, and the actual environments and
1.2 This international standard was developed in accor-
exposures anticipated for each material and the equipment in
dance with internationally recognized principles on standard-
which the materials are used. Guidelines are not replacements
ization established in the Decision on Principles for the
forcarefulandinformedengineeringjudgmentandevaluations
Development of International Standards, Guides and Recom-
and all possible performance and design constraints and
mendations issued by the World Trade Organization Technical
requirements cannot be foreseen. This practice is limited to
Barriers to Trade (TBT) Committee.
unmanned systems and unmanned or external portions of
2. Referenced Documents
manned systems, such as the Space Station. Generally, it is
applicabletosystemsinlowearthorbit,synchronousorbit,and
2.1 ASTM Standards:
interplanetarymissions.Althoughmanyofthesuggestionsand
E595Test Method for Total Mass Loss and Collected Vola-
cautions are applicable to both unmanned and manned
tile Condensable Materials from Outgassing in a Vacuum
spacecraft, manned systems have additional constraints and
Environment
requirements for crew safety which may not be addressed
G64Classification of Resistance to Stress-Corrosion Crack-
adequately in unmanned designs. Because of the added con-
ing of Heat-Treatable Aluminum Alloys
straints and concerns for human-rated systems, these systems
2.2 Marshall Space Flight Center (MSFC) Standard:
are not addressed in this practice.
MSFC-STD-3029Guidelines to the Selection of Metallic
Materials for Stress Corrosion Cracking Resistance in
4. Design Constraints
4.1 Orbital Environment—Theactualenvironmentinwhich
This practice is under the jurisdiction of ASTM Committee E21 on Space
SimulationandApplicationsofSpaceTechnologyandisthedirectresponsibilityof
the equipment is expected to operate must be identified and
Subcommittee E21.05 on Contamination.
defined. The exposures and requirements for material perfor-
Current edition approved Sept. 1, 2021. Published October 2021. Originally
mance differ for various missions. Environment definition
approved in 1999. Last previous edition approved in 2015 as E1997–15. DOI:
10.1520/E1997-15R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM AvailablefromU.S.GovernmentPrintingOfficeSuperintendentofDocuments,
Standards volume information, refer to the standard’s Document Summary page on 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
the ASTM website. www.access.gpo.gov.
Marshall Space Flight Center, AL 35812, or everyspec.com. European Space Agency, 8–10, Rue Mario-Nikis, 75738 Paris Cedex, France.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1997 − 15 (2021)
includes defining the range of temperature exposure, number which can cause shorts in electrical components or break off
and rate of thermal cycles, extent of vacuum exposure, solar and become conductive contaminants. Some other metals such
electromagnetic radiation particulate radiation, (trapped by the
ascadmiumandzinchavesimilarwhisker-growingproperties,
earth’s magnetosphere, solar wind, solar flares, and gamma
but not to the extent that tin has. Since they can also grow
rays) micrometeroids, launch loads and vibration, structural
whiskers, they should not be used.
loads, and so forth. Materials suitable for one orbit or mission
5.1.2 Stress-Corrosion Sensitive Metals—Metals, which are
environment may be unsuitable for others. The applications
stress-corrosion sensitive, should be avoided. Examples are
and requirements will define the suitability of the materials.
2024 T6 and 7075 T6 Aluminum, which can be used if heat
treated to conditions, such as 2024 T81 and 7075 T73, which
4.2 Low Earth Orbit (Up to 100 km)—Materials in this
region could be exposed to trapped Van Allen belt (ionizing) arenotstress-corrosionsensitive.Manybrassesandsomesteel
radiation,solarultravioletradiation,corrosiveattackbyatomic alloysalsoarestress-corrosionsensitive;however,evenalloys,
oxygen (A.O.), and more frequent and more extreme thermal
which are stress-corrosion sensitive can be used if loaded in
cycling and thermal shock as a result of frequent excursions
compression or if loaded to low sustained tensile stress levels,
into and out of the earth’s shadow. Orbital impacts may be a
typically no more than 25% of yield strength (see Classifica-
problem because of the large amount of debris in low orbits.
tion G64 and MSFC-SPEC-522).
Design life in orbit typically is on the order of 5 to 15 years.
5.1.3 Materials Forming Galvanic Couples—Material
Inclination of the orbit affects the service environment, that is,
combinations,whichformgalvaniccouplesgreaterthan0.5ev
polar orbits have a different flight profile than equatorial orbits
when exposed to a temperature and humidity controlled
and have different profiles for radiation exposure.
environment, such as during fabrication, testing, and storage,
4.3 Synchronous Orbit (35 900 km)—Materials in this re- should be prohibited under most circumstances. Providing
gionarenotexposedtosignificantatomicoxygenorveryhigh protection from electrolytes and maintaining them in a con-
energy trapped radiation but may have more exposure to
trolled environment, such as during fabrication and testing,
mediumenergyionizingelectronsandprotons,solarflares,and inhibits galvanic corrosion. Some alloys, such as magnesium,
relatively high levels of electromagnetic solar radiation
magnesium lithium alloys, and gold, form a galvanic couple
(ultraviolet, VUV photons, and X-rays). The number of ther-
with most common structural materials and must be protected
mal cycles is less and may be over a narrower temperature
adequately to prevent creating galvanic couples which cause
range than low earth orbit. Meteoroids also should be consid-
theanodicmetaltocorrode.Carboncompositesareincludedin
ered but are less likely to be significant compared to the
the materials, which must be evaluated for galvanic potential,
manmade debris found in low orbits. Design life in orbit
since carbon forms galvanic couples with metals. If there is no
typically is 5 to 15 years, with recent designs ranging from 10
electrolyte present, galvanic couples greater than 0.5 ev are
to 17 years.
permissible.Galvanicprotectioncanbeobtainedbypreventing
electrolytefromcontactingtheinterfaces,interposingadielec-
4.4 Interplanetary (Out-of-Earth Orbit)—In addition to the
tric material, or adding a material that is compatible with each
thermal extremes and environments of synchronous orbit, in
of the other materials separately.
the interplanetary environment, temperatures may be more
extreme, and micrometeoroids, solar wind, and cosmic rays 5.1.4 Materials With Thermal or Environmental
may be critical. Ability to survive and remain functional for Limitations—Materials that are weak or brittle at the expected
many years is important. Probes to the inner plants typically
service temperature or environment should be avoided. These
have design lifetimes of 5 to 10 years. Those to the outer materials included polymeric materials used at very low or
planets and beyond may have design lifetimes of 15 to 30
very high temperatures and some metals used at low tempera-
years.
tures. In this context, “low” can be from -40 to -120°C and
“high”canbefrom150to200°Cforpolymers.Somematerials
5. Materials to Avoid
are readily attacked by certain chemicals or solutions. For
example,aluminumalloysshouldnotbeusedinstronglybasic
5.1 Certain materials are known to be undesirable and
or acidic environments. Steels, particularly high carbon and
should be avoided no matter what the mission. Others are of
ferritic grades, are embrittled by halogens and hydrogen.
concern for certain missions or of more concern for some
Silicones are attacked by toluene. Titanium is attacked by
missions than others. In general, it is recommended that one
methanol.
avoid the materials described below:
5.1.5 Materials Diffıcult to Fabricate or Test—Materials
5.1.1 Metals with High Vapor Pressure in Vacuum and
that are difficult to fabricate, form, test, or inspect, or do not
Unusual Behaviors—Avoid the use of metals such as mercury,
have a history of consistency of properties or performance,
cadmium, and zinc, either as plating or monolithic metals. It is
shouldbeavoided.Somematerials,suchasceramicsandmost
important to exclude these metals both from the flight equip-
refractory metals, are relatively difficult to machine or form.
ment and vacuum chambers. If these metals are used in
Others are difficult to weld by conventional means. Some
vacuum and heated even moderately, they will vacuum metal-
cannot be formed easily. Certain applications such as elevated
lize both the cold walls of the chamber and any cold surfaces
on equipment in the chamber. Also, pure tin has the curious temperature service may require use of ceramics or refractory
metals.That should not reduce the need for careful review and
property of dendritic growth as a result of compressive
stresses, or thermal or electrical gradients, forming whiskers functional design of the equipment.All materials must be very
E1997 − 15 (2021)
carefully evaluated to assure successful, economic fabrication and reproducible performance. It is important to select mate-
and that the fabricated parts can be inspected easily for hidden rials that are well understood and have established histories of
defects. consistentandpredictablephysicalandmechanicalbehaviorin
space.Itisalsoimportantthatthematerialsbecapableofbeing
5.1.6 Materials That Have Excessive Outgassing—If the
processed in a controlled, repeatable manner so that perfor-
materials have high collected volatile condensable materials
mance is dependable and reproducible in accordance with
(CVCM)ortotalmassloss(TML)whenexposedat125°Cand
5.1.5.
tested, they generally are excluded from spacecraft applica-
5.1.11 Radiation Sensitivity—Materials that are sensitive to
tions. Normal acceptance limits for outgassing according to
radiation, or radiation and vacuum, require care in selection
TestMethodE595arenohigherthan1.0%TMLandnohigher
and application. Many glasses and optical coatings are dam-
than 0.10% CVCM. Some of these materials release conden-
aged by radiation. Some polymeric materials may be degraded
sates that react adversely with solar radiation or radiation and
by radiation or solar flares. The susceptibility to particulate
vacuum and may degrade sensitive surfaces. Others can
radiation damage sometimes is increased in vacuum when
contaminate surfaces or equipment such that functionality is
simultaneously exposed to ultraviolet radiation. It is important
impaired. High mass loss can indicate a loss or properties and
to consider radiation sensitivity and the orbital environment
functionalityinspace.Sometimes,amaterialwillhaveaccept-
when selecting materials.
able outgassing per normal requirements, but it may be in a
5.1.12 Materials Particulate Contamination—Emission of
particularly sensitive location, or the outgassing product may
particles or flaking can cause interference with optical or
have an adverse effect on specific sensitive equipment. These
thermal control surfaces or perhaps jam mechanisms. Thor-
conditions can require establishing lower levels for acceptable
ough cleaning of materials and assemblies is important to
outgassing or may require analysis of outgassed components
preventemissionofparticles.Conductiveparticlesareparticu-
and evaluation of the acceptability for the specific application.
larly undesirable and must be avoided. Surfaces should be
NOTE1—Thetestisdefinedasperformedat125°Cunlessclearlystated
examined and verified for elimination of particles before
otherwise; therefore, acceptability is limited to exposures below 125°C.
components are assembled.
The test temperature of 125°C was assumed to be significantly above the
5.1.13 Fluid Compatibility—If the material is likely to be
expectedoperatingtemperatureinservice.Ifexpectedoperatingtempera-
tures exceed 85 to 90°C the test temperature should be increased. It is exposed to propellant, coolants, in-process solvents, and so
suggested that the test temperature be at least 30°C higher than expected
forth, it is important to test and verify fluid compatibility with
maximum service temperature in order t
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