ASTM E1997-99(2003)e1
(Practice)Standard Practice for the Selection of Spacecraft Materials
Standard Practice for the Selection of Spacecraft Materials
SIGNIFICANCE AND USE
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 difficulty 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
e1
Designation:E1997–99 (Reapproved 2003)
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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were added editorially in October 2003.
1. Scope space Vehicle Structures
2.4 European Space Agency (ESA) Standard:
1.1 The purpose of this practice is to aid engineers, design-
PSS-07/QRM-0 Guidelines for Space Materials Selection
ers, quality and reliability control engineers, materials special-
2.5 Federal Standard:
ists, and systems designers in the selection and control of
QQ-A-250 Aluminum and Aluminum Alloy Plate and
materials and processes for spacecraft, external portion of
Sheet, Federal Specification for
manned systems, or man-tended systems. Spacecraft systems
areverydifferentfrommostotherapplications.Spaceenviron-
3. Significance and Use
ments are very different from terrestrial environments and can
3.1 This practice is a guideline for proper materials and
dramatically alter the performance and survivability of many
process selection and application. The specific application of
materials.Reliability,longlife,andinabilitytorepairdefective
these guidelines must take into account contractual agree-
systems (or high cost and difficultly of repairs for manned
ments, functional performance requirements for particular
applications) are characteristic of space applications. This
programs and missions, and the actual environments and
practice also is intended to identify materials processes or
exposures anticipated for each material and the equipment in
applications that may result in degraded or unsatisfactory
which the materials are used. Guidelines are not replacements
performance of systems, subsystems, or components. Ex-
forcarefulandinformedengineeringjudgmentandevaluations
amplesofsuccessfulandunsuccessfulmaterialsselectionsand
and all possible performance and design constraints and
uses are given in the appendices.
requirements cannot be foreseen. This practice is limited to
2. Referenced Documents unmanned systems and unmanned or external portions of
manned systems, such as the Space Station. Generally, it is
2.1 ASTM Standards:
applicabletosystemsinlowearthorbit,synchronousorbit,and
E595 Test Method for Total Mass Loss and Collected
interplanetarymissions.Althoughmanyofthesuggestionsand
Volatile Condensable Materials from Outgassing in a
cautions are applicable to both unmanned and manned space-
Vacuum Environment
craft, manned systems have additional constraints and require-
G 64 Classification of Resistance to Stress-Corrosion
ments for crew safety which may not be addressed adequately
Cracking of Heat-Treatable Aluminum Alloys
in unmanned designs. Because of the added constraints and
2.2 Marshall Space Flight Center (MSFC) Standard:
concerns for human-rated systems, these systems are not
MSFC-SPEC-522 Design Criteria for Controlling Stress
3 addressed in this practice.
Corrosion Cracking
2.3 Military Standards:
4. Design Constraints
MIL-STD-889 Dissimilar Materials
4.1 Orbital Environment—Theactualenvironmentinwhich
MIL-HDBK-5 Metallic Materials and Elements for Aero-
the equipment is expected to operate must be identified and
defined. The exposures and requirements for material perfor-
mance differ for various missions. Environment definition
This practice is under the jurisdiction of ASTM Committee E21 on Space
includes defining the range of temperature exposure, number
SimulationandApplicationsofSpaceTechnologyandisthedirectresponsibilityof
and rate of thermal cycles, extent of vacuum exposure, solar
Subcommittee E21.05 on Contamination.
Current edition approved Oct. 1, 2003. Published October 2003. Originally
electromagnetic radiation particulate radiation, (trapped by the
approved in 1999. Last previous edition approved in 1999 as E1997–99.
earth’s magnetosphere, solar wind, solar flares, and gamma
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
rays) micrometeroids, launch loads and vibration, structural
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM
Standards volume information, refer to the standard’s Document Summary page on loads, and so forth. Materials suitable for one orbit or mission
the ASTM website.
Marshall Space Flight Center, AL 35812.
Available from the Superintendent of Documents, U.S. Government Printing
Office, Washington, DC 20402. 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.
e1
E1997–99 (2003)
environment may be unsuitable for others. The applications alloysalsoarestress-corrosionsensitive;however,evenalloys,
and requirements will define the suitability of the materials. which are stress-corrosion sensitive can be used if loaded in
4.2 Low Earth Orbit (Up to 100 km)—Materials in this compression or if loaded to low sustained tensile stress levels,
region could be exposed to trapped Van Allen belt (ionizing) typically no more than 25% of yield strength (see Classifica-
radiation,solarultravioletradiation,corrosiveattackbyatomic
tion G64 and MSFC-SPEC-522).
oxygen (A.O.), and more frequent and more extreme thermal
5.1.3 Materials Forming Galvanic Couples—Materialcom-
cycling and thermal shock as a result of frequent excursions
binations, which form galvanic couples greater than 0.5 ev
into and out of the earth’s shadow. Orbital impacts may be a
when exposed to a temperature and humidity controlled
problem because of the large amount of debris in low orbits.
environment, such as during fabrication, testing, and storage,
Design life in orbit typically is on the order of 5 to 15 years.
should be prohibited under most circumstances. Providing
Inclination of the orbit affects the service environment, that is,
protection from electrolytes and maintaining them in a con-
polar orbits have a different flight profile than equatorial orbits
trolled environment, such as during fabrication and testing,
and have different profiles for radiation exposure.
inhibits galvanic corrosion. Some alloys, such as magnesium,
4.3 Synchronous Orbit (35 900 km)—Materials in this re-
magnesium lithium alloys, and gold, form a galvanic couple
gionarenotexposedtosignificantatomicoxygenorveryhigh
with most common structural materials and must be protected
energy trapped radiation but may have more exposure to
adequately to prevent creating galvanic couples which cause
mediumenergyionizingelectronsandprotons,solarflares,and
theanodicmetaltocorrode.Carboncompositesareincludedin
relatively high levels of electromagnetic solar radiation (ultra-
the materials, which must be evaluated for galvanic potential,
violet, VUV photons, and X-rays). The number of thermal
since carbon forms galvanic couples with metals. If there is no
cycles is less and may be over a narrower temperature range
electrolyte present, galvanic couples greater than 0.5 ev are
than low earth orbit. Meteoroids also should be considered but
permissible.Galvanicprotectioncanbeobtainedbypreventing
are less likely to be significant compared to the manmade
electrolytefromcontactingtheinterfaces,interposingadielec-
debris found in low orbits. Design life in orbit typically is 5 to
tric material, or adding a material that is compatible with each
15 years, with recent designs ranging from 10 to 17 years.
of the other materials separately.
4.4 Interplanetary (Out-of-Earth Orbit)—In addition to the
5.1.4 Materials With Thermal or Environmental
thermal extremes and environments of synchronous orbit, in
Limitations—Materials that are weak or brittle at the expected
the interplanetary environment, temperatures may be more
service temperature or environment should be avoided. These
extreme, and micrometeoroids, solar wind, and cosmic rays
materials included polymeric materials used at very low or
may be critical. Ability to survive and remain functional for
very high temperatures and some metals used at low tempera-
many years is important. Probes to the inner plants typically
tures. In this context, “low” can be from -40 to -120°C and
have design lifetimes of 5 to 10 years. Those to the outer
“high”canbefrom150to200°Cforpolymers.Somematerials
planets and beyond may have design lifetimes of 15 to 30
are readily attacked by certain chemicals or solutions. For
years.
example,aluminumalloysshouldnotbeusedinstronglybasic
or acidic environments. Steels, particularly high carbon and
5. Materials to Avoid
ferritic grades, are embrittled by halogens and hydrogen.
5.1 Certain materials are known to be undesirable and
Silicones are attacked by toluene. Titanium is attacked by
should be avoided no matter what the mission. Others are of
methanol.
concern for certain missions or of more concern for some
5.1.5 Materials Diffıcult to Fabricate or Test—Materials
missions than others. In general, it is recommended that one
that are difficult to fabricate, form, test, or inspect, or do not
avoid the materials described below:
have a history of consistency of properties or performance,
5.1.1 Metals with High Vapor Pressure in Vacuum and
shouldbeavoided.Somematerials,suchasceramicsandmost
Unusual Behaviors—Avoid the use of metals such as mercury,
refractory metals, are relatively difficult to machine or form.
cadmium, and zinc, either as plating or monolithic metals. It is
Others are difficult to weld by conventional means. Some
important to exclude these metals both from the flight equip-
cannot be formed easily. All materials must be very carefully
ment and vacuum chambers. If these metals are used in
evaluated to assure successful, economic fabrication and that
vacuum and heated even moderately, they will vacuum metal-
the fabricated parts can be inspected easily for hidden defects.
lize both the cold walls of the chamber and any cold surfaces
on equipment in the chamber. Also, pure tin has the curious 5.1.6 Materials That Have Excessive Outgassing—If the
property of dendritic growth as a result of compressive materials have high collected volatile condensable materials
stresses, or thermal or electrical gradients, forming whiskers (CVCM)ortotalmassloss(TML)whenexposedat125°Cand
which can cause shorts in electrical components or break off tested, they generally are excluded from spacecraft applica-
andbecomeconductivecontaminants.Someothermetalshave tions. Normal acceptance limits for outgassing according to
similar whisker-growing properties, but not to the extent that Test Method E595 are no higher than 1.0% TML and no
tin has. higher than 0.10% CVCM. Some of these materials release
5.1.2 Stress-Corrosion Sensitive Metals—Metals, which are condensates that react adversely with solar radiation or radia-
stress-corrosion sensitive, should be avoided. Examples are tion and vacuum and may degrade sensitive surfaces. Others
2024 T6 and 7075 T6 Aluminum, which can be used if heat can contaminate surfaces or equipment such that functionality
treated to conditions, such as 2024 T81 and 7075 T73, which is impaired. High mass loss can indicate a loss or properties
arenotstress-corrosionsensitive.Manybrassesandsomesteel and functionality in space. Sometimes, a material will have
e1
E1997–99 (2003)
acceptable outgassing per normal requirements, but it may be thermal control surfaces or perhaps jam mechanisms. Thor-
in a particularly sensitive location, or the outgassing product ough cleaning of materials and assemblies is important to
may have an adverse effect on specific sensitive equipment. preventemissionofparticles.Conductiveparticlesareparticu-
These conditions can require establishing lower levels for larly undesirable and must be avoided.
acceptable outgassing or may require analysis of outgassed 5.1.13 Fluid Compatibility—If the material is likely to be
components and evaluation of the acceptability for the specific exposed to propellant, coolants, in-process solvents, and so
application. forth, it is important to test and verify fluid compatibility with
the materials in advance. Always check and verify the com-
NOTE 1—Thetestisdefinedasperformedat125°Cunlessclearlystated
patibility of the materials with all fluids in which they may
otherwise; therefore, acceptability is limited to exposures at that tempera-
come into contact and with all of the fluids used, including
ture or below.
cleaning agents, solvents, and test fluids.
NOTE 2—Metallic materials do not “outgas,” but some metals, such as
5.1.14 Arc Tracking of Wires—Kaptont wire insulation is
zinc and cadmium, do exhibit high vapor pressure at relatively low
(<150°C) temperatures in vacuum. (See 5.1.1.) susceptible to arc tracking when used in power-carrying
applications.Any damage or abrasion to this type of wire may
5.1.7 Materials That Release Undesirable Components—
cause dielectric breakdown and arcing, even in vacuum. Wire
For example, acetic acid is released when curing certain
insulations, such as Teflon-polyimide-Teflont , which are not
silicones.Theacidcanattackandcorrodeelectricalwiringand
susceptible to arc tracking and have been qualified as such are
contacts and cause failures. In some applications, the alcohols
availableandshouldbeconsideredasreplacementsforKapton
released when silicones cure may be harmful.
wire insulation.
5.1.8 Unstable Polymeric Materials—Some polymeric ma-
5.1.15 Inadequately Controlled Materials—Any material
terials may revert or change character when exposed to other
that is purchased and controlled only by vendor data sheet or
materials or to the space environment. For example, certain
material certification, or both, has questionable controls. This
silicones in contact with amine-cured epoxy can become fluid;
type of product control should be viewed with caution. Data
some polymeric materials are degraded by radiation or atomic
sheets are not assurances of performance and often are mis-
oxygen (A.O.), or both. Polyamide may become brittle in
leading. For example, a maximum use temperature of a
vacuum and lose mechanical strength. PTFE and FEPbecome
polymermaybegivenas200°C,butatthattemperatureitmay
brittle when exposed to radiation in vacuum. Lubricants
have low dielectric strength, poor modulus of elasticity and
containing graphite may lose lubricity in vacuum. ETFE wire
strength, excessive outgassing, or significant loss of other
insulation may become brittle and crack if heated to high
properties. Relying on vendor certifications alone can resu
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.