ISO 16691:2014
(Main)Space systems — Thermal control coatings for spacecraft — General requirements
Space systems — Thermal control coatings for spacecraft — General requirements
ISO 16691:2014 defines general requirements for thermal control coatings (TCC) that are applied on metallic and/or non-metallic surfaces of spacecraft and payloads in order to provide the following thermo-optical properties: αs: solar absorptance; ε: emittance. The function of TCC is to reduce external heat absorption and/or to regulate radiant heat exchange between on-board equipment on spacecraft.
Systèmes spatial — Revêtements pour le contrôle thermique des satellites et véhicules spatiaux — Exigences générales
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 16691
First edition
2014-02-15
Space systems — Thermal control
coatings for spacecraft — General
requirements
Systèmes spatial — Revetements pour le contrôle thermique des
satellites et vehicules spatiaux — Exigences générales
Reference number
ISO 16691:2014(E)
©
ISO 2014
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ISO 16691:2014(E)
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ISO 16691:2014(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 4
4 General . 4
4.1 Functionality . 5
4.2 Basic components . 6
5 Selection . 6
6 Test methods for TCC . 8
6.1 Visual inspection . 8
6.2 Coating thickness . 8
6.3 Adhesion . 8
6.4 Thermo-optical properties . 8
6.5 Resistance (electrical surface resistance and electrical volume resistivity) .10
6.6 Outgassing .10
6.7 UV-resistance .11
6.8 Radiation resistance .11
6.9 Аtomic oxygen resistance .11
6.10 Gloss .11
6.11 Temperature cycling (influence of temperatures) .11
6.12 Mass of ejecta .11
7 Requirements for application .11
8 Safety requirements for TCC application .12
9 Identification .12
10 Protectors .12
11 Packing.13
12 Production program of quality assurance .13
12.1 General .13
13 Changes and revisions .13
13.1 Permissive document .13
13.2 Necessary signatures for the confirmatory document .14
13.3 Record of changes . .14
Annex A (informative) General properties of TCC-I and TCC-II .15
Bibliography .17
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ISO 16691:2014(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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
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to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 14, Space systems and operations.
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ISO 16691:2014(E)
Introduction
This International Standard explains technical information for TCCs selection and application required
to confirm their compliance with the requirements of the thermal control for spacecraft.
This International Standard classifies thermal control coatings in accordance with their usage in passive
and/or active thermal control subsystems for reduction of external heat absorption or regulation of
radiant heat exchange between on-board equipment on spacecraft, their general properties, and their
special characteristics for space environment applications.
This International Standard also contains special recommendations for surface preparation, application
of coating systems and curing, and establishes requirements for test methods on estimating properties
of thermal control coatings according to their target use.
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INTERNATIONAL STANDARD ISO 16691:2014(E)
Space systems — Thermal control coatings for spacecraft
— General requirements
1 Scope
This International Standard defines general requirements for thermal control coatings (TCC) that are
applied on metallic and/or non-metallic surfaces of spacecraft and payloads in order to provide the
following thermo-optical properties:
— α : solar absorptance;
s
— ε: emittance.
The function of TCC is to reduce external heat absorption and/or to regulate radiant heat exchange
between on-board equipment on spacecraft.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 9117-1:2009, Paints and varnishes — Drying tests — Part 1: Determination of through-dry state and
through-dry time
ISO 14624-3, Space systems — Safety and compatibility of materials — Part 3: Determination of offgassed
products from materials and assembled articles
3 Terms, definitions, and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
active thermal control system
system where the active thermal control method is used
Note 1 to entry: The active thermal control method is the procedure to control the temperature using mechanical
mobile components or fluid, using electric energy from a heater, changing the component’s thermo-physical
property, or utilizing another technology to change/control the temperature.
[SOURCE: JERG-2–310:2009]
3.1.2
coating
continuous layer formed from a single or multiple application of a coating material to a substrate
[SOURCE: ISO 4618:2006]
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ISO 16691:2014(E)
3.1.3
coating material
product in liquid, paste, or powder form, that, when applied to a substrate, forms a film possessing
protective and/or other specific properties
[SOURCE: ISO 4618:2006]
3.1.4
coating process
process of application of a coating material to a substrate, such as dipping, spraying, roller coating,
brushing
[SOURCE: ISO 4618:2006]
3.1.5
coating system
combination of all coats of coating materials which are to be applied or which have been applied to a
substrate
[SOURCE: ISO 4618:2006]
3.1.6
emissivity
emittance
ε
ε=M/Mb
where M is the radiant exitance of a thermal radiator, and Mb is the radiant exitance of a blackbody at
the same temperature
Note 1 to entry: The following adjectives should be added to define the conditions:
— Total: If they are related to the entire spectrum of thermal radiation (this designation can be considered as
[7]
implicit);
[7]
— Spectral or monochromatic: If they are related to a spectral interval centered on the wavelength λ;
— Hemispherical: If they are related to all directions along which a surface element can emit or receive
[7]
radiation;
— Directional: If they are related to the directions of propagation defined by a solid angle around the defined
[7]
direction;
[7]
— Normal: If they are related to the normal direction of propagation or incidence to the surface.
[SOURCE: ISO 80000-7:2008]
[SOURCE: ISO 16378]
3.1.7
paint
pigmented coating material which, when applied to a substrate, generally forms an opaque film having
protective or specific technical properties
[SOURCE: ISO 4618:2006]
3.1.8
paint film
intact coating that is formed by applying one or multiple layers of coating materials on a substrate
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ISO 16691:2014(E)
3.1.9
passive thermal control system
system where the passive thermal control method is used
Note 1 to entry: The passive thermal control method is the procedure to control the temperature of the component
within the specified range by adjusting the paths of conduction and radiation, and by the selection of geometric
form of each surface and thermo-physical property of the spacecraft.
[SOURCE: JERG-2–310:2009]
3.1.10
payload
set of space segment elements (parts of a space system placed in space to fulfill the space mission
objectives)
Note 1 to entry: A spacecraft payload is a set of instruments or equipment that performs the user mission.
Note 2 to entry: A launcher payload is a set of space segment elements carried into space in accordance with
agreed position, time, and environmental conditions.
[SOURCE: ISO 10795:2011]
3.1.11
primer
paint that has been formulated for use as a priming coat on prepared surfaces
3.1.12
priming coat
first coat of a coating system
3.1.13
solar absorptance
α
s
ratio of the solar radiant flux absorbed by a material (or body) to the radiant flux of the incident radiation
3.1.14
substrate
surface to which a coating material is applied or is to be applied
3.1.15
thermal control coating
TCC
coating that is used to maintain certain temperature conditions of an object by way of establishing the
balance between the heat absorbed from an environment and/or emitted by internal heat sources and
the energy radiated by object’s surface in an environment
3.1.16
varnish
clear coating material which, when applied to a substrate, forms a transparent film
3.1.17
witness sample
sample pieces that represent the coated product
Note 1 to entry: They shall be made in the form of the flat plates using the same coating material with the product,
and coated simultaneously. Used for destructive test and test that requires limited size of specimen.
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ISO 16691:2014(E)
3.2 Abbreviated terms
The following abbreviated terms are defined and used within this International Standard.
BOL beginning of life
EMC electromagnetic compatibility
EOL end-of-life
ESD electrostatic discharge
TCC(s) thermal control coating(s)
TCS(s) thermal control (sub) system(s)
QA quality assurance
UV ultraviolet
VUV vacuum ultraviolet
4 General
Figure 1 — The mapping of thermal control coatings relative to each passive thermal control
material
The action of the space environment strongly depends on the spacecraft service conditions. These are
defined by the orbits where spacecraft are intended to operate.
Heat sources which determine the temperature of a spacecraft are mainly solar rays and earth albedo.
The quantity of heat emitted from a spacecraft is equal to the sum of heat input and the quantity of
internal heat produced from the all equipment of a spacecraft.
Nevertheless, there are general factors that exert influence on spacecraft serviceability and efficiency:
vacuum, electromagnetic solar radiation, including UV-radiation and VUV-radiation, ionizing radiations,
atomic oxygen, temperature, contamination, micrometeoroids, and debris environment effects.
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ISO 16691:2014(E)
When in service, undesirable effects can occur, such as electrostatic charging, generation of spacecraft
outer atmosphere, and alternating thermal loads.
TCC are generally damaged by UV and charged particle exposure. In addition, at altitudes of roughly 200
km-600 km erosion of some TCC can occur due to atomic oxygen. Bleaching or whitening of UV/charged
particle induced damage of these coatings can also occur from atomic oxygen exposure.
TCCs are the elements of passive and/or active TCSs for temperature regulation of spacecraft. The
location of thermal control coatings in relation to other passive thermal control materials is shown in
Figure 1 above.
TCCs are applied on spacecraft surfaces, individual units, assemblies, and devices that are to be
temperature-controlled. They are used to maintain the preset temperature conditions of a spacecraft
by establishing the balance between the heat absorbed from an environment and/or emitted by on-
board sources, the energy redistributed between equipment and spacecraft structure, and the energy
radiated in environment.
The thermo-optical properties of a TCC are used in TCSs design. TCC shall meet the specification
requirements at the BOL and maintain required properties at the EOL of the spacecraft.
EMC/ESD, ageing, difference of properties between the beginning and the end of service life are defined
by service conditions and purposes of spacecraft. These properties are measured when candidate TCC
materials are under consideration for a TCS in the design stage.
The scope depends on the coating to be tested and requirements of designer and/ or production engineer.
4.1 Functionality
With regard to their functionality, determined by the coating’s ability to absorb or reflect the radiant
energy, the thermal control coatings can be classified as follows:
— I: true absorber (α →1, ε →1);
s
— II: solar reflector (α →0, ε →1);
s
— III: solar absorber (α →1, ε →0);
s
— IV: true reflector (α →0, ε →0).
s
4.1.1 Class I
Class I (black) TCCs absorb the heat from higher temperature objects and transmit the heat to lower
temperature one, and promote intensification of the radiant heat transfer between surfaces of devices
and units, as well as between devices, units, and environment.
Black TCCs are mainly applied to inner surfaces. They are applied on surfaces of spacecraft optical
devices (radiation-measuring instruments, analog of an ideal radiator), on lens cells, blends, and barrels
of optical devices (cameras, telescopes, scanners of a terrestrial surface), and on external surfaces to
absorb radiation from the sun. Additionally, these coatings prevent the reflection of light from one
surface to another.
4.1.2 Class II
Class II (white) TCCs reflect incident light and thermal radiation from heat sources such as solar rays
and earth albedo to maintain the temperature of spacecraft design components within the working
range and increase efficiency of TCSs.
White TCCs are mainly applied to outer surfaces. Class II TCCs can also be used to sink heat in
environments to lower temperature of spacecraft members.
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ISO 16691:2014(E)
4.1.3 Class III
Class III TCCs are used on facilities that function periodically and require ingress of energy when the
facility is off to maintain a stable temperature and prevent exceeding low temperature limits.
4.1.4 Class IV
Class IV TCCs are mainly applied on surfaces subjecting to simultaneous heating by propulsion jets and
subject to convective cooling.
4.2 Basic components
The basic components of TCCs are binders and pigments.
Paints generally have both of these components; but other coatings, such as plasma spray TCC can use
only one, usually a pigment.
Usual binders are either organic (for example, silicone, polyurethane, fluorocarbon, etc) or inorganic
(for example, silicates) components.
Pigments which can be used include oxides and fluorides of metals, metals, and also complex and simple
salts.
5 Selection
TCCs should be selected considering their thermo-optical and environmental resistance properties,
advantages and disadvantages, meet mission requirements, and perform the required system functional
objectives.
To ensure working capacity of spacecraft, selection of TCC or coating system (class of coating, structure,
paints, and primers) should be made by the designer depending on requirements for their properties
and type of material to which a coating material is applied and service conditions.
When selecting TCCs of classes I and II, primary characteristics to be considered are shown in Table 1
below.
When selecting TCCs of classes III and IV, the list of primary characteristics is determined by designers
depending on service conditions of the equipment, on which TCC is applied.
Table 1 — Primary characteristics to be considered when selecting TCCs of Class I and II
TCC-I TCC-II
Coating type Remarks on selection
Internal External External
surface surface surface
Thickness + + + Coating thickness is determined con-
sidering adhesion, hiding power, and
weight. Required thickness to achieve
its thermo-optical function is different
depending on types of coating materials.
Adhesion + + + The adhesion of TCCs is different
depending on the types of coating mate-
rials and materials to be coated. The
TCCs which demonstrates a high level
of adhesion shall be selected regarding
adhesion test results of the TCC to dif-
ferent materials.
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ISO 16691:2014(E)
Table 1 (continued)
TCC-I TCC-II
Coating type Remarks on selection
Internal External External
surface surface surface
Thermo-optical char- α - + + The appropriate α and ε shall be
s s
acteristics selected regarding internal heat genera-
ε + + +
n
tion and the desired temperature of
spacecraft.
When internal heat is small, the space-
craft temperature is determined by α
s
/ε.
Since extended exposure to the space
environment will affect thermo-optical
properties, special attention is needed.
Electrical volume resistivity + + + Reducing surface charging requires
controlling electric properties of the
Electrical surface resistance + + +
surface materials that directly contact
with the surrounding plasma. Electri-
cal resistivity should be low enough to
reduce possibility of local charging and
the resultant electrostatic discharge.
Outgassing + + + Outgassing character of TCC shall fulfill
the contamination requirement of the
spacecraft. Special care should be taken
when the coating is applied on a large
area, close to contamination sensitive
and/or cryogenic surfaces. The quantity
of outgas is different depending on the
processing condition such as the spray-
ing and the curing of the coating and the
lot of the coating material.
UV-resistance - + + TCCs which applied outer surface of a
spacecraft are subject to strong UV rays.
Thermo-optical properties and adhesion
are degraded by UV.
The amount of UV which a spacecraft
receives is determined by the orbital
altitude, expected lifetime, attitude, and
geometry of the spacecraft.
Radiation resistance + + + TCCs shall withstand strong levels of
radiation. Thermo-optical properties
and adhesion are degraded by radia-
tion. Dose which a spacecraft receives
is determined by the orbital altitude,
expected lifetime, and shielding effect of
the spacecraft.
Atomic oxygen resistance - + + TCCs which applied outer surface of a
spacecraft are exposed to a large quan-
tity of atomic oxygen. Thermo-optical
properties and adhesion are affected by
atomic oxygen.
Gloss + + + Class I TCC is sometimes used around
optical instruments in purpose of sur-
face reflection prevention. TCC with flat
(low gloss) surface should be selected
for that purpose.
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ISO 16691:2014(E)
Table 1 (continued)
TCC-I TCC-II
Coating type Remarks on selection
Internal External External
surface surface surface
Temperature cycling + + + TCCs shall withstand temperature
cycling. Thermo-optical properties and
adhesion are affected by temperature
cycling.
The cycle is determined by the orbital
altitude of spacecraft.
a
Mass of ejecta + + + Damage caused by meteoroids and/or
debris can result in a potential genera-
tion of small debris (ejecta). The amount
of ejecta is greater for brittle materials
such as inorganic TCC than for ductile
materials.
a
For specific cases, on request of the designer.
General properties of typical TCCs are shown in Annex A.
6 Test methods for TCC
6.1 Visual inspection
Visual inspection shall be performed to the coated product itself. Witness samples approved by the
manufacturer shall be used for comparison, if required.
The samples shall be prepared from the materials that are used in spacecraft.
6.2 Coating thickness
The thickness of TCC applied on surfaces is measured by non-destructive methods.
The thickness of TCC shall be measured in three different points on the surface of the product. When the
2
coated surface is greater than 1 m , number of measurements should be coordinated with the customer.
Thickness of TCC is not to be measured in hard-to-reach places, on welds, and on edges of the product.
The weight of dried TCC (coating system) will depend on its thickness and shall be calculated in advance
to adhere to the requirements of system weight limitation.
6.3 Adhesion
Adhesion of a TCC is determined using preferably the cross-cut tests primarily performed on a witness
sample. The cross-cut test on a painted product will be performed with the customer’s approval. Other
adhesion tests are also permissible. The subsequent repair of the damaged test areas and/or coating
details is mandatory.
The measurement of the coating adhesion in the hard-to-reach places is not mandatory.
The test specimen shall be prepared simultaneously with the coated products.
6.4 Thermo-optical properties
a) The thermo-optical properties shall be measured in the course of/after space environment
resistance tests.
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ISO 16691:2014(E)
b) The measurements shall be performed on the witness samples by the methods referred in Annex A.
Other measurement method could be applied with the customer’s approval. Measurement method
shall be recorded and reported.
c) To measure α , ε, and thickness of the TCC applied on metal surfaces, the witness samples are made
s
in the form of the flat plates, one item per product or a batch of products, and coated simultaneously
with them.
d) To measure α , ε, and thickness of the TCC applied on non-metallic surfaces, the witness samples are
s
made from the same material that is used in the product to be coated.
6.4.1 Method of measurement of α
s
Two test methods are described in this clause.
6.4.1.1 Solar absorptance using a spectrophotometer
The primary method covers the measurement of spectral absorptance (α ), reflectance, and transmittance
s
of materials using spectrophotometers equipped wit
...
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