ISO 23020:2021

Space systems — Determination of test methods to characterize material or component properties required for break-up models used for Earth re-entry

This document defines the elementary thermal tests to obtain thermal properties of materials and composite materials used to manufacture space body to support the fragmentation and survivability analysis. This document does not apply to spacecraft containing nuclear power sources[1].

Systèmes spatiaux — Détermination des méthodes d'essai pour caractériser les matériaux ou les éléments de structure nécessaires pour les modèles de calcul de « désintégration » utilisés pour la rentrée terrestre

General Information

• Status: Published
• Publication Date: 14-Sep-2021
• ICS: 49.140 - Space systems and operations
• Technical Committee: ISO/TC 20/SC 14 - Space systems and operations
• Drafting Committee: ISO/TC 20/SC 14/WG 6 - Materials and processes
• Current Stage: 6060 - International Standard published
• Start Date: 15-Sep-2021
• Due Date: 27-Oct-2021
• Completion Date: 15-Sep-2021

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23020
First edition
2021-09
Space systems — Determination of
test methods to characterize material
or component properties required for
break-up models used for Earth re-
entry
Systèmes spatiaux — Détermination des méthodes d'essai pour
caractériser les matériaux ou les éléments de structure nécessaires
pour les modèles de calcul de « désintégration » utilisés pour la
rentrée terrestre
Reference number
ISO 23020:2021(E)
©
ISO 2021

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ISO 23020:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 23020:2021(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 . 5
4 Methodology of material characterization. 5
4.1 General . 5
4.2 Temperature range . 5
4.3 Type of tests . 6
4.4 Test conditions . 6
4.5 Mechanisms of degradation . 7
5 Definition of the elementary tests. 7
5.1 General . 7
5.2 List of the elementary tests . 8
5.3 Composite materials specifications . 9
6 Metallic and metallic composite materials .10
6.1 Test conditions .10
6.2 List of the recommended standards .10
7 Organic and organic composite materials .11
7.1 Organic materials .11
7.1.1 General.11
7.1.2 Test conditions.11
7.2 Organic composite materials .11
7.2.1 General.11
7.2.2 Test conditions in virgin state .11
7.2.3 Test conditions in charred state .12
7.3 List of the recommended standards .12
8 Ceramic and associated composite materials .12
8.1 Test conditions .12
8.2 List of the recommended standards .13
8.2.1 Ceramic .13
8.2.2 Ceramic composite .13
Bibliography .14
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ISO 23020:2021(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.
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
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 14, Space systems and operations.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved

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ISO 23020:2021(E)

Introduction
New regulations require unmanned spacecraft and launch vehicle orbital stages, called space bodies in
this document, to be designed and manufactured in such way that fragments generated during Earth
re-entry cannot cause casualties, damage to property or environmental pollution on the ground (see
ISO 24113).
Space bodies are submitted to high aero-thermodynamic fluxes, pressures and shear stresses that
lead to their disintegration into fragments that can potentially reach ground after a re-entry. These
fragments are generated by the effect of aero-thermal loads seen by components that constitute a space
body. The assessment of the fragmentation and subsequent survivability of the fragments in terms of
size and trajectory is based on simulation.
The methodology to determine the size of the debris is based on an idealized two-step process, called
fragmentation and survivability.
— Fragmentation
Based on the knowledge of the orbital (ballistic) trajectory of the space body and the knowledge
of its design, the computation of temperature and stresses determine the most probable failure
locations that will generate sub components. The breakup fragments prior to re-entry are termed
debris.
— Survivability
The objective is then to determine if debris can survive (no completely burned), and then if the final
size and energy when touching down the Earth are in accordance with the international regulation.
The computation of the final size and energy of the debris is based on generic geometry definition,
homogenized properties and on the knowledge of their trajectories.
For both fragmentation and survivability, suitable thermal response models require a range of material
properties for a full characterization of the material response.
Thermal tests used to determine material properties need to be well defined and shared between
spacecraft manufacturers and regulation authorities.
There are a range of relevant spacecraft materials, from metals, organic and ceramics to composite
materials.
As a result, the material or component properties used in break-up models is an essential model input.
Objects that separate during the ascent phase and impact the ground are addressed in ISO 14620-2.
Assessment, mitigating and control of potential risks created by the re-enter of objects from the orbit
are addressed in ISO 27875.
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INTERNATIONAL STANDARD ISO 23020:2021(E)
Space systems — Determination of test methods to
characterize material or component properties required
for break-up models used for Earth re-entry
1 Scope
This document defines the elementary thermal tests to obtain thermal properties of materials and
composite materials used to manufacture space body to support the fragmentation and survivability
analysis.
[1]
This document does not apply to spacecraft containing nuclear power sources .
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1.1
ablation
chemical change and removal of surface material (3.1.12) due to the action of external high temperature
heating
Note 1 to entry: Ablation can be a chemical process, addressing chemical reaction (gas-solid or gas-liquid).
Note 2 to entry: Ablation can be a physical process addressing vaporization, melting, fusion.
Note 3 to entry: Ablation can be a mechanical process addressing phenomena of erosive process (applied to solid
or liquid surface) linked to pressure effect and wall shear stress due to high-speed motion.
[SOURCE: EN 16603-31:2014, 3.2.4.2, modified — Notes 1, 2 and 3 to entry have been added.]
3.1.2
break-up
event that completely or partially destroys an object and generates space debris (3.1.18)
Note 1 to entry: Debris generated during earth re-entry (3.1.16) can survive and fall to the ground.
[SOURCE: ISO 24113:2019, 3.2, modified — Note 1 to entry has been added.]
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ISO 23020:2021(E)

3.1.3
break-up altitude
altitude when the main structural fragmentation occurs leading several components (3.1.5)
Note 1 to entry: Altitude break-up (3.1.2) can occur on a wide range of values depending on trajectories and
attitudes of the spacecraft (3.1.19).
3.1.4
ceramic
essentially inorganic and non-metallic material (3.1.12)
Note 1 to entry: The concept “ceramic” comprises products based on clay as raw material and also materials
which are typically based on oxides, nitrides, carbides, silicides, borides, carbon etc.
[SOURCE: ISO 20507:2014, 2.1.7]
3.1.5
component
part
set of materials (3.1.12), assembled according to defined and controlled processes, which cannot be
disassembled without destroying its capability and which performs a simple function that can be
evaluated against expected performance requirements
[SOURCE: ISO 10795:2019, 3.48]
3.1.6
composite material
combination of materials (3.1.12) different in composition or form on a macro scale
Note 1 to entry: The constituents retain their identities in the composite.
Note 2 to entry: The constituents can normally be physically identified, and there is an interface between them.
[SOURCE: ISO 16454:2007, 3.6]
3.1.7
emissivity
ε
quotient of the radiant exitance of a radiator and the radiant exitance of a Planckian radiator at the
same temperature, expressed by
ε = M/M
b
where M is the radiant exitance of a thermal radiator and M is the radiant exitance of a Planckian
b
radiator (called hereafter black body) at the same temperature (ISO 80000-5)
Note 1 to entry: Emissivity of any surface is a function of wavelength, direction, temperature, and surface
conditions.
Note 2 to entry: Emittance is a property of a particular object. It is determined by material (3.1.12) emissivity,
surface roughness, of angle of incidence, oxidation, the sample's thermal and mechanical history, surface finish,
and measured wavelength range. Although emissivity is a major component in determining emittance, the
emissivity determined under laboratory conditions seldom agrees with actual emittance of a certain sample.
[SOURCE: ISO 80000-7:2019, item 7-30.1, modified — Notes 1 and 2 to entry have been added.]
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ISO 23020:2021(E)

3.1.7.1
total directional emissivity
total radiance, L , emitted by the considered surface, divided by total radiance emitted by the black
Ω
body, L° at the same temperature
Ω
Note 1 to entry: Determined in the domain of near infrared (NIR) and middle infrared (MIR) of the infrared
radiation (3.1.10).
[SOURCE: ISO 9288:1989, 5.8, modified — Note 1 to entry has been added.]
3.1.7.2
spectral directional emissivity
spectral radiance, L , of the considered surface divided by the spectral radiance emitted by the black
Ωλ
body, L° , at the same temperature
Ωλ
Note 1 to entry: Determined in the domain of near infrared (NIR) and middle infrared (MIR) of the infrared
radiation (3.1.10).
[SOURCE: ISO 9288:1989, 5.9, modified — Note 1 to entry has been added.]
3.1.7.3
total hemispherical emissivity
total hemispherical exitance, M, of the considered surface divided by the total hemispherical exitance of
the black body, M° at the same temperature
Note 1 to entry: Determined in the domain of near infrared (NIR) and middle infrared (MIR) of the infrared
radiation (3.1.10).
[SOURCE: ISO 9288:1989, 5.10, modified — Note 1 to entry has been added.]
3.1.8
glass ceramic
inorganic material (3.1.12) produced by the complete fusion of raw materials at high temperatures into
a homogeneous liquid which is then cooled to a rigid condition and temperature treated in such a way
as to produce a mostly micro crystalline body
[SOURCE: ISO 7086-2:2000, 2.11]
3.1.9
glass transition temperature
Tg
characteristic value of the temperature range over which the glass transition takes place
Note 1 to entry: Glass transition temperature characterizes the transition from true solid to very viscous liquid.
Note 2 to entry: The assigned glass transition temperature (Tg) may vary, depending on the specific property
and on the method and conditions selected to measure it.
[SOURCE: ISO 11357-2:2020, 3.1, modified — Note 1 to entry has been added.]
3.1.10
infrared radiation
electromagnetic radiation of wavelength between 780 nm and approximately 1 mm
Note 1 to entry: For infrared radiation, the range between 780 nm and 1 mm is commonly subdivided into:
— near infrared (NIR): 780 nm to 3 000 nm;
— middle infrared (MIR): 3 000 nm to 50 000 nm;
— far infrared (FIR): 50 000 nm to 1 mm.
Note 2 to entry: These limits are also specified in ISO 20473.
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ISO 23020:2021(E)

Note 3 to entry: For break-up (3.1.2) models (3.1.14), NIR and MIR are the must representative wavelength
domains related to re-entry (3.1.16) phenomena.
[SOURCE: ISO 9488:1999, 3.9, modified — Notes 1, 2 and 3 to entry have been added.]
3.1.11
launch vehicle orbital stage
complete element of a launch vehicle that is designed to deliver a defined thrust during a dedicated
phase of the launch vehicle’s operation and achieve orbit
Note 1 to entry: Non-propulsive elements of a launch vehicle, such as jettisonable tanks, multiple payload
structures or dispensers, are considered to be part of a launch vehicle orbital stage while they are attached.
[SOURCE: ISO 24113:2019, 3.13]
3.1.12
material
raw, semi-finished or finished purchased item (gaseous, liquid, solid) of given characteristics from
which processing into a functional element of the product is undertaken
Note 1 to entry: Gas is not concerned for break-up (3.1.2) models (3.1.14).
[SOURCE: ISO 10795:2019, 3.148, modified — Note 1 to entry has been added.]
3.1.13
melting point
temperature at which solid changes state from solid to liquid
Note 1 to entry: At the melting point the solid and liquid phases exist in equilibrium for a single substance. The
melting point of a solid depends on pressure and is usually specified at standard pressure.
Note 2 to entry: Solids, which differ from single substances and eutectics, do not have a sharp melting point
because fusion occurs in a wide temperature range. Therefore, there is a temperature of beginning of fusion
called solidus and an end temperature of fusion called liquidus.
Note 3 to entry: Amorphous solids (including many polymers) do not have a sharp melting point. When these pass
from a solid to fluid state, they do so over a wide temperature range, centred roughly about the glass transition
temperature (3.1.9).
Note 4 to entry: The determination method of the melting point used in the break-up (3.1.2) model (3.1.14) shall
be mentioned if it is liquidus state, solidus state or even as an average of solidus and liquidus.
Note 5 to entry: By conservatism, liquidus is preferred in order to state that no solid debris can fall on ground.
Note 6 to entry: Carbon does not melt at any temperature under standard pressure; instead it sublimes around
4 000 K.
3.1.14
model
physical or abstract representation of relevant aspects of an item or process that is put forward as a
basis for calculations, predictions, or further assessment
Note 1 to entry: The term “model” can also be used to identify particular instances of the product, e.g. flight
model.
[SOURCE: ISO 10795:2019, 3.155]
3.1.15
pyrolysis
chemical change caused by heat
Note 1 to entry: Sometimes used in a more restricted sense to describe chemical changes resulting from heat
treatment in the absence of oxygen.
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ISO 23020:2021(E)

[SOURCE: ISO 11074:2015, 6.4.33]
3.1.16
re-entry
return of a spacecraft (3.1.19) or other space object into the Earth’s atmosphere
Note 1 to entry: Several alternative definitions are available for the boundary between the Earth’s atmosphere
and outer space.
[SOURCE: ISO 10795:2019, 3.197]
3.1.17
reversible specific heat capacity
specific heat capacity determined with DSC where all heat contributions (endothermic and exothermic)
due to chemical transformation of the material (3.1.12) are not taken into account to measure the
specific heat capacity
3.1.18
space debris
non-functional fragments of, or residue from, a space segment element, or launch segment element, in
Earth orbit or re-entering the Earth’s atmosphere
[SOURCE: ISO 10795:2019, 3.219, modified — The deprecated term has been removed.]
3.1.19
spacecraft
manned or unmanned vehicle designed to orbit or travel in space
[SOURCE: ISO 10795:2019, 3.224, modified — The abbreviated term and Note 1 to entry have been
removed.]
3.2 Abbreviated terms
DSC differential scanning calorimetry
LFA laser flash analysis
TGA thermogravimetry analysis
4 Methodology of material characterization
4.1 General
Unmanned spacecraft and launch vehicle orbital stages are made with different components based on
metals, polymers, ceramics and composite materials made with polymers, metals and ceramics.
The test matrix (type of test and environmental experimental conditions) shall be determined with
respect to the complexity of the break-up model and the re-entry mode that provides the temperature
range.
4.2 Temperature range
Depending on the type of re-entry (controlled versus natural) of the spacecraft, one can define two
temperature domains associated with high dynamic pressure and aerothermal loads or high energy,
respectively.
For controlled re-entry, the entry speed is maximized when the flight path angle allows the temperature
to reach over 1 500 K and below approximately 2 500 K.
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ISO 23020:2021(E)

For uncontrolled re-entry, the trajectory speed and low flight path angle are naturally decaying slowly.
In these conditions, the theoretical heat fluxes and dynamic pressure can lead to lower break-up
altitude of the main parts and consequently the temperature of the parts can be lower than 1 500 K.
Even if the reality is more complex, for practical reasons, two domains of temperature can be defined
to specify the temperature range of the test matrix. This temperature boundary of 1 500 K is not fixed
but should be adapted to take into account important evolutions of the material and its thermo-physical
properties.
4.3 Type of tests
Elementary thermal tests can characterize basic properties, such as thermal conductivity, specific heat
capacity and chemical effects inclusive of melt and pyrolysis. These bulk properties are independent of
the surface state or any surface interactions with the environmental gas.
In order to produce a reasonable prediction of the survivability of an object during the re-entry, it is
necessary to take into account mass and energy transfer occurring between the object surface and the
environmental gas. Surface properties and characteristics, such as emissivity, catalicity of the object,
shall be measured in representative atmosphere.
The available data is often restricted to a temperature domain, which is generally well below the real or
predicted temperature, met by the debris during the terminal re-entry phase.
Technological tests (complementary to elementary tests) are consequently required to extend the
domain temperature in a more relevant surface state so that surface mass and energy transfer are
ideally well captured.
These technological tests can be divided in two types.
The first type is radiative (generally in the infrared wavelength domain), where a furnace may be used
to expose one face of the material sample to highly calibrated pure radiative heat flux in air at ambient
pressure or in vacuum. This allows capturing of the material emissivity, the roughness and some
chemical effects that contribute to the surface mass and energy transfer. Convective flow effects on the
surface phenomena in such a test set-up are not assessed.
The second method to generate high temperature and pseudo flight representative aerothermal
loads consists in the use of plasma wind tunnel facilities. These facilities can capture effects such as
the material chemical catalicity to the recombination of air molecules at the surface, and the thermo-
mechanical flow effects on the material.
4.4 Test conditions
a) Tested samples shall be representative to the materials used in the real part even if the thickness
has to be adapted to test devices.
b) Elementary thermal tests shall be performed on test samples of monolithic material to solve the
energy balance conservation equation (including Fourier’s law in case of multidimensional object)
by knowing the density, reversible specific heat capacity, thermal conductivity, glass transition
[2]
temperature, melting point, and enthalpy of fusion . Total hemispherical emissivity tests are also
[3]
required .
NOTE Thermal conductivity is often determined indirectly with diffusivity measurement. Thermal
conductivity is then calculated knowing the density and specific heat.
c) Due to the uncertainties of the measurements of thermo-physical material properties, the number
of test samples to identify each thermal property measured in laboratories shall be selected with
respect to the expected statistical uncertainty of the material property.
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ISO 23020:2021(E)

In case of material scattering, a minimum of 5 measurements for each characteristic determined for
each test condition are recommended if the statistic distribution can be fitted by a Gaussian law.
d) Test methods and environmental conditions shall be described.
4.5 Mechanisms of degradation
Degradations are based on different mechanisms: fusion, pyrolysis and chemical ablation. Mechanical
ablation is not addressed in this document even if it exists.
a) For metal and metal composite materials, oxidation, melting and chemical ablation shall be
considered.
b) For ceramic and ceramic composite materials, oxidation, melting and chemical ablation shall be
considered.
NOTE 1 Glass and glass ceramic materials are considered as ceramic materials.
NOTE 2 Carbon materials like graphite are considered as ceramic materials.
NOTE 3 Carbon/carbon composite materials are considered as ceramic composite materials.
c) For organic and organic composite materials, melting, pyrolysis and chemical ablation driven by
oxidation shall be considered.
NOTE 4 It is assumed that non-reinforced organic materials are fully consumed during any re-entry
conditions but often decompose endo-thermally and as such can act to postpone the degradation of
spacecraft components.
5 Definition of the elementary tests
5.1 General
a) All relevant thermo-physical material properties shall be characterized under well-defined
laboratory conditions (temperature, heating rate, pressure, gas composition, number of tests for
each condition).
b) Elementary test
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23020
ISO/TC 20/SC 14
Space systems — Determination of
Secretariat: ANSI
test methods to characterize material
Voting begins on:
2021­06­09 or component properties required for
break-up models used for Earth re-
Voting terminates on:
2021­08­04
entry
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SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
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Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 23020:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
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NATIONAL REGULATIONS. ISO 2021

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ISO/FDIS 23020:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH­1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/FDIS 23020:2021(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 . 5
4 Methodology of material characterization. 5
4.1 General . 5
4.2 Temperature range . 5
4.3 Type of tests . 6
4.4 Test conditions . 6
4.5 Mechanisms of degradation . 7
5 Definition of the elementary tests. 7
5.1 General . 7
5.2 List of the elementary tests . 8
5.3 Composite materials specifications . 9
6 Metallic and metallic composite materials . 9
6.1 Test conditions . 9
6.2 List of the recommended standards .10
7 Organic and organic composite materials .11
7.1 Organic materials .11
7.1.1 General.11
7.1.2 Test conditions.11
7.2 Organic composite materials .11
7.2.1 General.11
7.2.2 Test conditions in virgin state .11
7.2.3 Test conditions in charred state .12
7.3 List of the recommended standards .12
8 Ceramic and associated composite materials .12
8.1 Test conditions .12
8.2 List of the recommended standards .13
8.2.1 Ceramic .13
8.2.2 Ceramic composite .13
Bibliography .14
© ISO 2021 – All rights reserved iii

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ISO/FDIS 23020:2021(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 non­governmental, 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.
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
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 14, Space systems and operations.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 23020:2021(E)

Introduction
New regulations require unmanned spacecraft and launch vehicle orbital stages, called space bodies in
this document, to be designed and manufactured in such way that fragments generated during Earth
re-entry cannot cause casualties, damage to property or environmental pollution on the ground (see
ISO 24113).
Space bodies are submitted to high aero-thermodynamic fluxes, pressures and shear stresses that
lead to their disintegration into fragments that can potentially reach ground after a re-entry. These
fragments are generated by the effect of aero-thermal loads seen by components that constitute a space
body. The assessment of the fragmentation and subsequent survivability of the fragments in terms of
size and trajectory is based on simulation.
The methodology to determine the size of the debris is based on an idealized two-step process, called
fragmentation and survivability.
— Fragmentation
Based on the knowledge of the orbital (ballistic) trajectory of the space body and the knowledge
of its design, the computation of temperature and stresses determine the most probable failure
locations that will generate sub components. The breakup fragments prior to re-entry are termed
debris.
— Survivability
The objective is then to determine if debris can survive (no completely burned), and then if the final
size and energy when touching down the Earth are in accordance with the international regulation.
The computation of the final size and energy of the debris is based on generic geometry definition,
homogenized properties and on the knowledge of their trajectories.
For both fragmentation and survivability, suitable thermal response models require a range of material
properties for a full characterization of the material response.
Thermal tests used to determine material properties need to be well defined and shared between
spacecraft manufacturers and regulation authorities.
There are a range of relevant spacecraft materials, from metals, organic and ceramics to composite
materials.
As a result, the material or component properties used in break­up models is an essential model input.
Objects that separate during the ascent phase and impact the ground are addressed in ISO 14620-2.
Assessment, mitigating and control of potential risks created by the re-enter of objects from the orbit
are addressed in ISO 27875.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23020:2021(E)
Space systems — Determination of test methods to
characterize material or component properties required
for break-up models used for Earth re-entry
1 Scope
This document defines the elementary thermal tests to obtain thermal properties of materials and
composite materials used to manufacture space body to support the fragmentation and survivability
analysis.
[1]
This document does not apply to spacecraft containing nuclear power sources .
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1.1
ablation
chemical change and removal of surface material (3.1.12) due to the action of external high temperature
heating
Note 1 to entry: Ablation can be a chemical process, addressing chemical reaction (gas-solid or gas-liquid);
Note 2 to entry: Ablation can be a physical process addressing vaporization, melting, fusion;
Note 3 to entry: Ablation can be a mechanical process addressing phenomena of erosive process (applied to solid
or liquid surface) linked to pressure effect and wall shear stress due to high-speed motion.
[SOURCE: EN 16603-31:2014, 3.2.4.2, modified — Notes 1, 2 and 3 to entry have been added.]
3.1.2
break-up
event that completely or partially destroys an object and generates space debris (3.1.18)
Note 1 to entry: Debris generated during earth re-entry (3.1.16) can survive and fall to the ground.
[SOURCE: ISO 24113:2019, 3.2, modified — Note 1 to entry has been added.]
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3.1.3
break-up altitude
altitude when the main structural fragmentation occurs leading several components (3.1.5)
Note 1 to entry: Altitude break-up (3.1.2) can occur on a wide range of values depending on trajectories and
attitudes of the spacecraft (3.1.19).
3.1.4
ceramic
essentially inorganic and non-metallic material (3.1.12)
Note 1 to entry: The concept “ceramic” comprises products based on clay as raw material and also materials
which are typically based on oxides, nitrides, carbides, silicides, borides, carbon etc.
[SOURCE: ISO 20507:2014, 2.1.7]
3.1.5
component
part
set of materials (3.1.12), assembled according to defined and controlled processes, which cannot be
disassembled without destroying its capability and which performs a simple function that can be
evaluated against expected performance requirements
[SOURCE: ISO 10795:2019, 3.48]
3.1.6
composite material
combination of materials (3.1.12) different in composition or form on a macro scale
Note 1 to entry: The constituents retain their identities in the composite.
Note 2 to entry: The constituents can normally be physically identified, and there is an interface between them.
[SOURCE: ISO 16454:2007, 3.6]
3.1.7
emissivity
ε
quotient of the radiant exitance of a radiator and the radiant exitance of a Planckian radiator at the
same temperature, expressed by
ε = M/M
b
where M is the radiant exitance of a thermal radiator and M is the radiant exitance of a Planckian
b
radiator (called hereafter black body) at the same temperature (ISO 80000-5)
Note 1 to entry: Emissivity of any surface is a function of wavelength, direction, temperature, and surface
conditions.
Note 2 to entry: Emittance is a property of a particular object. It is determined by material (3.1.12) emissivity,
surface roughness, of angle of incidence, oxidation, the sample's thermal and mechanical history, surface finish,
and measured wavelength range. Although emissivity is a major component in determining emittance, the
emissivity determined under laboratory conditions seldom agrees with actual emittance of a certain sample.
[SOURCE: ISO 80000-7:2019, item 7-30.1, modified — Notes 1 and 2 to entry have been added.]
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3.1.7.1
total directional emissivity
total radiance, L , emitted by the considered surface, divided by total radiance emitted by the black
Ω
body, L° at the same temperature
Ω
Note 1 to entry: Determined in the domain of near infrared (NIR) and middle infrared (MIR) of the infrared
radiation (3.1.10).
[SOURCE: ISO 9288:1989, 5.8, modified — Note 1 to entry has been added.]
3.1.7.2
spectral directional emissivity
spectral radiance, L , of the considered surface divided by the spectral radiance emitted by the black
Ωλ
body, L° , at the same temperature
Ωλ
Note 1 to entry: Determined in the domain of near infrared (NIR) and middle infrared (MIR) of the infrared
radiation (3.1.10).
[SOURCE: ISO 9288:1989, 5.9, modified — Note 1 to entry has been added.]
3.1.7.3
total hemispherical emissivity
total hemispherical exitance, M, of the considered surface divided by the total hemispherical exitance of
the black body, M° at the same temperature
Note 1 to entry: Determined in the domain of near infrared (NIR) and middle infrared (MIR) of the infrared
radiation (3.1.10).
[SOURCE: ISO 9288:1989, 5.10, modified — Note 1 to entry has been added.]
3.1.8
glass ceramic
inorganic material (3.1.12) produced by the complete fusion of raw materials at high temperatures into
a homogeneous liquid which is then cooled to a rigid condition and temperature treated in such a way
as to produce a mostly micro crystalline body
[SOURCE: ISO 7086­2:2000, 2.11]
3.1.9
glass transition temperature
Tg
characteristic value of the temperature range over which the glass transition takes place
Note 1 to entry: Glass transition temperature characterizes the transition from true solid to very viscous liquid.
Note 2 to entry: The assigned glass transition temperature (Tg) may vary, depending on the specific property
and on the method and conditions selected to measure it.
[SOURCE: ISO 11357-2:2020, 3.1, modified — Note 1 to entry has been added.]
3.1.10
infrared radiation
electromagnetic radiation of wavelength between 780 nm and approximately 1 mm
Note 1 to entry: For infrared radiation, the range between 780 nm and 1 mm is commonly subdivided into:
— near infrared (NIR): 780 nm to 3 000 nm;
— middle infrared (MIR): 3 000 nm to 50 000 nm
— far infrared (FIR): 50 000 nm to 1 mm
Note 2 to entry: These limits are also specified in ISO 20473.
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Note 3 to entry: For break-up (3.1.2) models (3.1.14), NIR and MIR are the must representative wavelength
domains related to re-entry (3.1.16) phenomena.
[SOURCE: ISO 9488:1999, 3.9, modified — Notes 1, 2 and 3 to entry have been added.]
3.1.11
launch vehicle orbital stage
complete element of a launch vehicle that is designed to deliver a defined thrust during a dedicated
phase of the launch vehicle’s operation and achieve orbit
Note 1 to entry: Non-propulsive elements of a launch vehicle, such as jettisonable tanks, multiple payload
structures or dispensers, are considered to be part of a launch vehicle orbital stage while they are attached.
[SOURCE: ISO 24113:2019, 3.13]
3.1.12
material
raw, semi-finished or finished purchased item (gaseous, liquid, solid) of given characteristics from
which processing into a functional element of the product is undertaken
Note 1 to entry: Gas is not concerned for break-up (3.1.2) models (3.1.14).
[SOURCE: ISO 10795:2019, 3.148, modified — Note 1 to entry has been added.]
3.1.13
melting point
temperature at which solid changes state from solid to liquid
Note 1 to entry: At the melting point the solid and liquid phases exist in equilibrium for a single substance. The
melting point of a solid depends on pressure and is usually specified at standard pressure.
Note 2 to entry: Solids, which differ from single substances and eutectics, do not have a sharp melting point
because fusion occurs in a wide temperature range. Therefore, there is a temperature of beginning of fusion
called solidus and an end temperature of fusion called liquidus.
Note 3 to entry: Amorphous solids (including many polymers) do not have a sharp melting point. When these pass
from a solid to fluid state, they do so over a wide temperature range, centred roughly about the glass transition
temperature (3.1.9).
Note 4 to entry: The determination method of the melting point used in the break-up (3.1.2) model (3.1.14) shall
be mentioned if it is liquidus state, solidus state or even as an average of solidus and liquidus.
Note 5 to entry: By conservatism, liquidus is preferred in order to state that no solid debris can fall on ground.
Note 6 to entry: Carbon does not melt at any temperature under standard pressure; instead it sublimes around
4 000 K.
3.1.14
model
physical or abstract representation of relevant aspects of an item or process that is put forward as a
basis for calculations, predictions, or further assessment
Note 1 to entry: The term “model” can also be used to identify particular instances of the product, e.g. flight
model.
[SOURCE: ISO 10795:2019, 3.155]
3.1.15
pyrolysis
chemical change caused by heat
Note 1 to entry: Sometimes used in a more restricted sense to describe chemical changes resulting from heat
treatment in the absence of oxygen.
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[SOURCE: ISO 11074:2015, 6.4.33]
3.1.16
re-entry
return of a spacecraft (3.1.19) or other space object into the Earth’s atmosphere
Note 1 to entry: Several alternative definitions are available for the boundary between the Earth’s atmosphere
and outer space.
[SOURCE: ISO 10795:2019, 3.197]
3.1.17
reversible specific heat capacity
specific heat capacity determined with DSC where all heat contributions (endothermic and exothermic)
due to chemical transformation of the material (3.1.12) are not taken into account to measure the
specific heat capacity
3.1.18
space debris
non­functional fragments of, or residue from, a space segment element, or launch segment element, in
Earth orbit or re­entering the Earth’s atmosphere
[SOURCE: ISO 10795:2019, 3.219, modified — The deprecated term has been removed.]
3.1.19
spacecraft
manned or unmanned vehicle designed to orbit or travel in space
[SOURCE: ISO 10795:2019, 3.224, modified — The abbreviated term and Note 1 to entry have been
removed.]
3.2 Abbreviated terms
DSC differential scanning calorimetry
LFA laser flash analysis
TGA thermogravimetry analysis
4 Methodology of material characterization
4.1 General
Unmanned spacecraft and launch vehicle orbital stages are made with different components based on
metals, polymers, ceramics and composite materials made with polymers, metals and ceramics.
The test matrix (type of test and environmental experimental conditions) shall be determined with
respect to the complexity of the break-up model and the re-entry mode that provides the temperature
range.
4.2 Temperature range
Depending on the type of re-entry (controlled versus natural) of the spacecraft, one can define two
temperature domains associated with high dynamic pressure and aerothermal loads or high energy,
respectively.
For controlled re-entry, the entry speed is maximized when the flight path angle allows the temperature
to reach over 1 500 K and below approximately 2 500 K.
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For uncontrolled re-entry, the trajectory speed and low flight path angle are naturally decaying slowly.
In these conditions, the theoretical heat fluxes and dynamic pressure can lead to lower break-up
altitude of the main parts and consequently the temperature of the parts can be lower than 1 500 K.
Even if the reality is more complex, for practical reasons, two domains of temperature can be defined
to specify the temperature range of the test matrix. This temperature boundary of 1 500 K is not fixed
but should be adapted to take into account important evolutions of the material and its thermo-physical
properties.
4.3 Type of tests
Elementary thermal tests can characterize basic properties, such as thermal conductivity, specific heat
capacity and chemical effects inclusive of melt and pyrolysis. These bulk properties are independent of
the surface state or any surface interactions with the environmental gas.
In order to produce a reasonable prediction of the survivability of an object during the re-entry, it is
necessary to take into account mass and energy transfer occurring between the object surface and the
environmental gas. Surface properties and characteristics, such as emissivity, catalicity of the object,
shall be measured in representative atmosphere.
The available data is often restricted to a temperature domain, which is generally well below the real or
predicted temperature, met by the debris during the terminal re-entry phase.
Technological tests (complementary to elementary tests) are consequently required to extend the
domain temperature in a more relevant surface state so that surface mass and energy transfer are
ideally well captured.
These technological tests can be divided in two types.
The first type is radiative (generally in the infrared wavelength domain), where a furnace may be used
to expose one face of the material sample to highly calibrated pure radiative heat flux in air at ambient
pressure or in vacuum. This allows capturing of the material emissivity, the roughness and some
chemical effects that contribute to the surface mass and energy transfer. Convective flow effects on the
surface phenomena in such a test set­up are not assessed.
The second method to generate high temperature and pseudo flight representative aerothermal
loads consists in the use of plasma wind tunnel facilities. These facilities can capture effects such as
the material chemical catalicity to the recombination of air molecules at the surface, and the thermo-
mechanical flow effects on the material.
4.4 Test conditions
a) Tested samples shall be representative to the materials used in the real part even if the thickness
has to be adapted to test devices.
b) Elementary thermal tests shall be performed on test samples of monolithic material to solve the
energy balance conservation equation (including Fourier’s law in case of multidimensional object)
by knowing the density, reversible specific heat capacity, thermal conductivity, glass transition
[2]
temperature, melting point, and enthalpy of fusion . Total hemispherical emissivity tests are also
[3]
required .
NOTE Thermal conductivity is often determined indirectly with diffusivity measurement. Thermal
conductivity is then calculated knowing the density and specific heat.
c) Due to the uncertainties of the measurements of thermo-physical material properties, the number
of test samples to identify each thermal property measured in laboratories shall be selected with
respect to the expected statistical uncertainty of the material property.
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In case of material scattering, a minimum of 5 measurements for each characteristic determined for
each test condition are recommended if the statistic distribution can be fitted by a Gaussian law.
d) Test methods and environmental conditions shall be described.
4.5 Mechanisms of degradation
Degradations are based on different mechanisms: fusion, pyrolysis and chemical ablation. Mechanical
ablation is not addressed in this document even if it exists.
a) For metal and metal composite materials, oxidation, melting and chemical ablation shall be
considered.
b) For ceramic and ceramic composite materials, oxidation, melting and chemical ablation shall be
considered.
NOTE 1 Glass and glass ceramic materials are considered as ceramic materials.
NOTE 2 Carbon materials like graphite are considered as ceramic materials.
NOTE 3 Carbon/carbon composite materials are considered as ceramic composite materials.
c) For organic and organic composite materials, melting, pyrolysis and chemical ablation driven by
oxidation shall be considered.
NOTE 4 It is assumed that non-reinforced organic materials are fu
...