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

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Published
Publication Date
14-Sep-2021
Current Stage
6060 - International Standard published
Start Date
15-Sep-2021
Completion Date
15-Sep-2021
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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
---------------------- Page: 1 ----------------------
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: +41 22 749 01 11
Email: copyright@iso.org
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

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
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
---------------------- Page: 4 ----------------------
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.
© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
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.]
© ISO 2021 – All rights reserved 1
---------------------- Page: 6 ----------------------
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

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

where M is the radiant exitance of a thermal radiator and M is the radiant exitance of a Planckian

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.]

2 © ISO 2021 – All rights reserved
---------------------- Page: 7 ----------------------
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

body, L° 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, 5.8, 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

body, L° , 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, 5.9, 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

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.
© ISO 2021 – All rights reserved 3
---------------------- Page: 8 ----------------------
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.
4 © ISO 2021 – All rights reserved
---------------------- Page: 9 ----------------------
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.
© ISO 2021 – All rights reserved 5
---------------------- Page: 10 ----------------------
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.
6 © ISO 2021 – All rights reserved
---------------------- Page: 11 ----------------------
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-
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ISO/FDIS 23020:2021(E)
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---------------------- Page: 1 ----------------------
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: +41 22 749 01 11
Email: copyright@iso.org
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
---------------------- Page: 3 ----------------------
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

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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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ISO/FDIS 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

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

where M is the radiant exitance of a thermal radiator and M is the radiant exitance of a Planckian

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/FDIS 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

body, L° 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, 5.8, 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

body, L° , 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, 5.9, 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

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/FDIS 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/FDIS 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

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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ISO/FDIS 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 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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ISO/FDIS 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 fu
...

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