ISO 15856:2010

INTERNATIONAL ISO
STANDARD 15856
First edition
2010-08-01

Space systems — Space environment —
Simulation guidelines for radiation
exposure of non-metallic materials
Systèmes spatiaux — Environnement spatial — Lignes directrices de
simulation pour l'exposition aux radiations des matériaux non
métalliques




Reference number
ISO 15856:2010(E)
©
ISO 2010

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ISO 15856:2010(E)
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ISO 15856:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.2
3 Terms, definitions, abbreviated terms and acronyms.2
3.1 Terms and definitions .2
3.2 Abbreviated terms and acronyms .4
4 Space environment radiation characteristics.5
4.1 Sources of radiation in space .5
4.2 Radiation levels for Earth orbits .5
4.3 Methods for charged particle and photon irradiation.6
5 Properties of spacecraft materials .6
5.1 General .6
5.2 Surface properties.6
5.3 Volume (bulk) properties .7
5.4 Measure of radiation action.7
6 Requirements for simulation of space radiation.7
6.1 Objective.7
6.2 Methodology (test) .7
6.3 Methodology for simulation that involves simulation of the type of radiation, its spectrum,
and intensity .8
7 Radiation sources for simulation .10
7.1 Sources.10
7.2 Low-energy protons .10
7.3 Low-energy electrons .10
7.4 High-energy proton accelerators.10
7.5 High-energy electron accelerators .10
7.6 Ultraviolet radiation.10
8 Alternate simulation method.11
8.1 Methodology .11
8.2 Standard spacecraft orbits.11
Annex A (informative) Additional information .13
Annex B (informative) Depth dose .15
Annex C (informative) Accelerated tests .21
Bibliography.22

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ISO 15856:2010(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15856 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 14, Space systems and operations.
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ISO 15856:2010(E)
Introduction
The purpose of this International Standard is to establish guidelines for designing space systems that are
highly reliable and will have long mission life spans. It is impossible to reproduce the space environment for
ground testing of space system elements because of the variety and complexity of the environments and the
effects on materials. The reliability of the test results depends on simulating the critical effects of the space
environments for a particular mission. The main objectives of the simulation are to get test results that are
satisfactory for the material behaviour in a space environment and to use existing radiation sources and
methods available in the test laboratory.
Non-metallic materials used in space systems are affected by electrons and protons in a broad energy interval,
electromagnetic solar radiation (both the near and the far ultraviolet radiation) and X-ray radiation. The
response of non-metallic materials to radiation depends on the type of radiation and energy that defines the
ionization losses density, and the radiation response of materials depends on these losses. The radiation
spectrum and chemical composition of materials define the absorbed dose distribution, especially in the near-
the-surface layers.
During the design of the space system, it is necessary to simulate long mission time in reasonable ground
time. For this reason, it is necessary to perform accelerated radiation tests requiring the use of dose rates that
may be of an order of magnitude greater than in the natural space environment. These high dose rates can
influence the effects on the properties of materials. Therefore, the main requirement for the correct simulation
in radiation tests involves simulating the correct effects of materials in space by considering the type,
spectrum (energy), and absorbed dose rate of the radiation. Simulation is complex because the various
properties of materials may respond differently to the approximations of the natural space environment used
for testing. In addition, various materials may respond differently to the same simulated space radiation
environment. This is valid for different classes of materials such as polymeric and semiconductor materials.
The space engineering materials in space environment are exposed not only to charged particles and
electromagnetic solar radiation but also to a number of other environmental factors, e.g. atomic oxygen, deep
vacuum, thermocycling, etc. Synergistic interactions can significantly increase the material degradation,
i.e. decrease the time of operation, but in certain cases (like solar absorptance variation under UV and
protons) synergistic interaction can decrease the degradation. These effects are not well understood and have
to be simulated as far as possible. Space environment simulation at the combined exposure is a much more
complicated procedure than the simulation of each factor separately. Development of corresponding
standards, both for different factors and different classes of materials, will be provided in the following stages
of the standard set preparation for space environment simulation at on-ground tests of materials.
This International Standard contains normative statements, recommended practices and informative parts.
The term “shall” indicates a normative statement.

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INTERNATIONAL STANDARD ISO 15856:2010(E)

Space systems — Space environment — Simulation guidelines
for radiation exposure of non-metallic materials
IMPORTANT — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing this
document using a colour printer.
1 Scope
This International Standard is the first part of a series on space environment simulation for on-ground tests of
materials used in space. This International Standard covers the testing of non-metallic materials exposed to
simulated space radiation. Non-metallic materials include glasses, ceramics and polymer-metal composite
materials such as metal matrix composites and laminated materials. This International Standard does not
cover semiconductor materials used for electronic components. The types of simulated radiation include
charged particles (electrons and protons), solar ultraviolet radiation and soft X-radiation of solar flares.
Synergistic interactions of the radiation environment are covered only for these natural, and some induced,
environmental effects.
This International Standard outlines the recommended methodology and practices for the simulation of space
radiation effects on materials. Simulation methods are used to reproduce the effects of the space radiation
environment on materials that are located on surfaces of space vehicles and behind shielding.
This methodology involves:
a) the definition of the environment to be simulated using commonly accepted space environment models;
b) the definition of the material properties under test or of concern in accordance with the specificity of
degradation in the space environment, satellite-specific constraints determination, temperature conditions
(constant values or cycled temperature mode), mechanical stress, charging, contamination, etc.;
c) the selection of laboratory radiation simulation sources, energies and fluences that will be used to
reproduce the kind of orbital radiation and mimic the orbital dose profiles;
d) the exposure techniques and procedures used to perform the laboratory simulation including
contamination control, acceleration factors (dose rates), temperature control, vacuum levels and
atmospheric effects.
An alternative method using standard spacecraft orbits and environments is included.
This International Standard does not specify the design of material specimens, methods of measuring the
properties of materials and characteristics of radiation sources, the design of vacuum systems and the
preparation of test reports. The user should select designs and measurement methods based on the state of
the art and the requirements of specific space systems and contracts.
This International Standard does not include a list of hazards and safety precautions. The users are
responsible for providing safe conditions based on national and local regulations.
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ISO 15856:2010(E)
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
IEC 60544-2, Guide for determining the effects of ionizing radiation on insulating materials —
Part 2: Procedures for irradiation and test
ASTM E490, Standard Solar Constant and Zero Air Mass Solar Spectral Irradiance Tables
ASTM E512, Standard Practice for Combined, Simulated Space Environment Testing of Thermal Control
Materials with Electromagnetic and Particulate Radiation
3 Terms, definitions, abbreviated terms and acronyms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
absorbed dose
D
amount of energy imparted by ionizing radiation per unit mass of irradiated matter
NOTE 1 The quotient of dε by dm, where dε is the mean energy imparted by ionizing radiation to matter of mass dm, is
dε
D =
dm
−1
NOTE 2 The special name of the unit for absorbed dose is the gray (Gy). 1 Gy = 1 J⋅kg .
3.1.2
acceleration factor
ratio of dose rate between simulation and expectation at space application for the same type of radiation
3.1.3
bremsstrahlung
brake radiation
photon radiation, continuously distributed in energy up to the energy of the incident particle radiation, emitted
from a material due to deceleration of incident particle radiation within the material, mainly due to electrons
3.1.4
depth distribution criterion of absorbed dose
ratio of the exponent index, µ, of the absorbed dose depth profile curve to the material density, ρ
NOTE The depth distribution criterion of absorbed dose is measured in square centimetres per gram.
3.1.5
depth dose profile
distribution of the absorbed dose through the depth of material
3.1.6
energy fluence
total energy of ionizing radiation per unit area of the irradiated surface
NOTE Energy fluence is measured in joules per square metre.
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ISO 15856:2010(E)
3.1.7
galactic cosmic rays
GCR
high-energy-charged particle fluxes penetrating the heliosphere from local interstellar space
[ISO 15390, definition 2.1]
3.1.8
heliosphere
region surrounding the sun where the solar wind dominates the interstellar medium
NOTE Also known as solar cavity.
3.1.9
ionizing radiation
any type of radiation consisting of charged particles or uncharged particles or both, that, as a result of physical
interaction, creates ions of opposite signs by either primary or secondary processes
NOTE Charged particles could be positive or negative electrons, protons or other heavy ions, and uncharged
particles could be X-rays, gamma rays, or neutrons.
3.1.10
linear energy transfer
LET
energy delivered by a charged particle passing through a substance and locally absorbed per unit length of
path
−1 2 −1 2 −1 2 −1
NOTE It is measured in joules per metre. Other dimensions are keV⋅µm , J⋅m ⋅kg , MeV⋅cm ⋅g , MeV⋅cm ⋅mg .
3.1.11
mean free path
average distance that a subatomic particle, ion, atom or molecule travels between successive collisions with
ions, atoms or molecules
3.1.12
natural space environment
environment that exists in space without a spacecraft system present
NOTE This includes radiation, vacuum, residual atmosphere, plasmas, magnetic fields and meteoroids.
3.1.13
near ultraviolet radiation
NUV radiation
solar electromagnetic radiation with a wavelength in the range of 300 nm to 400 nm
3.1.14
radiation action measure
energetic characteristic of radiation action on a material
NOTE The radiation action measure for non-metallic materials is an absorbed dose or energy fluence.
3.1.15
radiation belt
electrons and protons trapped by the geomagnetic (planetary magnetic) field
3.1.16
radiation scale effect
dependence of the material degradation on the thickness ratio of irradiated and unirradiated layers
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ISO 15856:2010(E)
3.1.17
surface properties
properties of a material which are defined by the physico-chemical and morphological structure of its surface
NOTE The depth or thickness that constitutes surface properties depends upon the type of material and particular
property.
3.1.18
synchrotron radiation
continuous radiation created by the acceleration of relativistic charged particles, as in a synchrotron or storage
ring
NOTE Synchrotron radiation is a practical energy source of photons.
3.1.19
volume properties
bulk properties
properties that are determined by characteristics averaged through the volume of a product
3.1.20
irradiance
〈at a point on a surface〉 quotient of the radiant flux incident on an element of the surface containing the point,
by the area of that element
3.1.21
vacuum ultraviolet radiation
VUV radiation
solar electromagnetic radiation with a wavelength in the range from 10 nm to 200 nm
3.1.22
X-rays
irradiances with a wavelength in the range from 0,001 nm and 10 nm
3.2 Abbreviated terms and acronyms
Al aluminium
ASTM (now ASTM International) American Society for Testing and Materials
ECSS European Cooperation for Space Standardization
ESA European Space Agency
EUV extreme ultraviolet
FEP fluorinated ethylene propylene
VUV vacuum ultraviolet
GCR galactic cosmic rays
GEO Geosynchronous orbit
GLON GLONASS navigation spacecraft (Russian Federation)
GOST R Federal Agency on Technical Regulating and Metrology (Russian Federation)
GPS Global Positioning Satellite (U.S.A.)
HEO highly elliptical orbit
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ISO 15856:2010(E)
ISS International Space Station
LEO low Earth orbit
LET linear energy transfer
MeV megaelectronvolt
Mg magnesium
MUV middle ultraviolet
NUV near ultraviolet
POL Standard polar orbit
PTFE polytetrafluoroethylene
4 Space environment radiation characteristics
4.1 Sources of radiation in space
The main sources of radiation in space are galactic and solar particle radiation (solar wind), solar X-radiation
in the 1 nm to 10 nm wavelength band, vacuum ultraviolet radiation and trapped charged particles of low
energy in radiation belts around the planets (e.g. Earth, Jupiter and Saturn).
4.2 Radiation levels for Earth orbits
4.2.1 General
The specified radiation levels for the various standard orbits are based on generally accepted, published
models that are, in turn, based on measurements. Work is in progress for improving and standardizing the
models. Space Environment Information System (SPENVIS) provides standardized access to models of the
hazardous space environment through the following website: http:/www.spenvis.oma.be/spenvis/.
4.2.2 Electron irradiation
The electron irradiation environment is based on the best available model to date, the AE-8 model. The AE-8
model describes spectra of electrons with minimal energy 40 keV (see Clause A.1 and Reference [23]).
There are no similar models for lower-energy electrons. Energy characteristics of low-energy particles for a
geosynchronous orbit are presented in References [25] and [28].
For the LEO and POL orbits, the energy ranges are 40 keV to 5 MeV for electrons. For the GEO, GLON and
HEO orbits, the energy ranges are 1 keV to 5 MeV for electrons.
4.2.3 Proton irradiation
The proton irradiation environment is based on the best AP-8 model available now. The AP-8 model describes
spectra of protons with minimal energy 100 keV (see Clause A.1 and Reference [24]).
There are no similar models for low-energy protons. Energy characteristics of such particles for a
geosynchronous orbit are presented in Reference [26].
For the LEO (ISS) and POL orbits, the energy ranges are 100 keV to 200 MeV for protons. For the GEO,
GLON and HEO orbits, the energy ranges are 1 keV to 100 MeV for protons.
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ISO 15856:2010(E)
4.2.4 X-radiation
The main part of the solar X-ray radiation in the energy range of 0,1 keV to 10 keV corresponds to the solar
flares. See Reference [29]. The predominant energy contribution comes from photons with energies between
1 keV and 3 keV.
4.2.5 Bremsstrahlung (brake radiation)
Bremsstrahlung is produced from the deceleration of particulate radiation inside matter. Bremsstrahlung
contributes to the radiation damage in materials with thicknesses greater than several grams per square
centimetre or in shielded materials.
4.2.6 Ultraviolet radiation
Solar spectral irradiances in the VUV and NUV are specified in ASTM E490.
−2
Irradiance of the VUV in low Earth orbits is about 0,1 W⋅m or 0,007 % of the total solar electromagnetic
−2
irradiance. Irradiance of the NUV for the same conditions is about 118 W⋅m or 8,7 % of the total solar
electromagnetic irradiance.
The VUV energy spectrum with wavelength lower than 50 nm is specified in ASTM E512.
4.3 Methods for charged particle and photon irradiation
Use the dose and energy fluence calculation made for a typical mission (for specific environmental conditions
and place of the material on the spacecraft, taking into account all the shielding effects). Examples of the most
commonly used codes are presented in Clause A2.
An alternative method to obtain such information is based on the standard spacecraft orbits and environments
(see Clause 8).
Take into account that the contribution of each type of space radiation into the total absorbed dose depends
on the shielding depth (see, for example, Table A.1). Sometimes the space radiation (i.e. Bremsstrahlung,
60
high-energy electrons) may be simulated by Co gamma rays (see References [14], [15] and [18] for
simulation methods). See ASTM E512 and Reference [21] for UV radiation simulation methods.
5 Properties of spacecraft materials
5.1 General
Various regions of radiation spectra are responsible for the degradation of different properties when materials
are irradiated in the space environment. The properties are divided into surface properties and volume (bulk)
properties.
5.2 Surface properties
Surface properties are determined by the nature of the material at or near the surface. The surface of a
material is defined as that part of the material exposed directly to the space environment in the spacecraft
−2
application. “Near the surface” is considered to be approximately 4 mg⋅cm or less (see Figures B.1 to B.3).
The surface properties include surface electrical conductivity, optical properties (reflectance, absorptance,
emittance), adhesive properties (adhesion, adhesive strength), tribotechnical characteristics (coefficient of
friction, friction durability, wear resistance) and surface electrical charging.
The low-energy part of the corpuscular radiation spectrum (no more than 50 keV for electrons and 1,0 MeV for
protons) and VUV are primarily responsible for the degradation of surface properties.
The whole spectrum of the solar X-radiation and UV affect the surface properties of non-metallic materials.
Most materials have a high absorption of VUV, and some materials will be affected by near UV-radiation
depending on absorption characteristics and energies required to break molecular bonds.
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ISO 15856:2010(E)
5.3 Volume (bulk) properties
Volume properties are determined by the average properties of the material through the bulk of a product.
Degradation of the volume material properties is determined by the high-energy parts of the charged particle
−2 −2
spectrum. The radiation damage to materials located behind shielding of more than 5 mg⋅cm to 10 mg⋅cm
thickness is also caused by the high-energy parts of the spectrum.
Composite materials consisting of layers of thin films may require additional analyses to determine the depth
dose distribution from the natural space radiation.
5.4 Measure of radiation action
To study the surface properties, a measure of radiation action should be taken equal to the energy fluence of
2
corpuscular radiation, J/m , resulting from the absorption of more than 90 % exposure energy in tens of
microns thick near-the-surface layers and neglecting the absorption of Bremsstrahlung energy in the same
layers in comparison with that of corpuscular radiation (see Table A.1).
The absorbed dose averaged over the product thickness is taken to be a measure of radiation action to
analyse the volume properties and it practically relates to a high-energy part of the spectrum. The same
measure is applied to shielded materials.
This approach to selecting the radiation action measure is influenced by a radiation scale effect,
i.e. dependence of the material degradation on the thickness ratio of irradiated and unirradiated layers (see
References [31] and [32]). The two-measure approach of radiation action is applicable to the layers with more
2
than 4 mg/cm thickness on the space vehicle surface. The energy fluence is an only measure of radiation
2
action on the layers of less than 4 mg/cm thickness.
6 Requirements for simulation of space radiation
6.1 Objective
The objective is to simulate the effects of the space environment on materials and not necessarily duplicate
the space environment.
6.2 Methodology (test)
The following methodology is suggested for organizing space simulation tests.
a) Select the space environment factors for the specific mission and properties that are critical for
performance and reliability of the material to be tested.
b) Consider the induced environment factors that can influence the effects that are under investigation
(radiation-induced outgassing, contamination of samples, etc.).
c) Determine the environment acceptable acceleration rates that will not adversely affect the results.
d) Select the environments to be simulated for on-ground tests.
e) Select the radiation sources for ground simulation.
f) Determine the energies and fluences for the radiation sources to closely simulate the depth dose profile
that would occur in space. A detailed analysis of the space radiation environment and absorbed dose
profile for the given orbit, mission lifetime and material shall be performed. Various mathematical models
are available to perform this type of analysis.
g) For simulation, calculate the depth d
...