ISO 10785:2025

Space systems — Bellows — Design and operation

This document specifies general and detailed requirements for bellows used in space systems. It establishes requirements regarding material, design, analysis, fabrication, material, testing, inspection, and operation for space use. This document is applicable to metallic bellows which are used as pressure bearing components and are integrated into a pressure system. This document is not applicable to engine bellows or valve bellows.

Systèmes spatiaux — Soufflets — Conception et fonctionnement

General Information

• Status: Published
• Publication Date: 07-Aug-2025
• 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 - Space systems and operations
• Current Stage: 6060 - International Standard published
• Start Date: 08-Aug-2025
• Due Date: 24-Aug-2025
• Completion Date: 08-Aug-2025

Relations

• Revises: ISO 10785:2011 - Space systems — Bellows — Design and operation
• Effective Date: 27-Aug-2022

Standards Content (Sample)

International
Standard
ISO 10785
Second edition
Space systems — Bellows — Design
2025-08
and operation
Systèmes spatiaux — Soufflets — Conception et fonctionnement
Reference number
© ISO 2025
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
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 6
5 Requirements . 6
5.1 General .6
5.2 Design requirements .7
5.2.1 Loads, pressures and environments .7
5.2.2 Strength .7
5.2.3 Stiffness .7
5.2.4 Thermal effects . .8
5.2.5 Stress analysis .8
5.2.6 Leak-before-burst (LBB) failure modes .8
5.2.7 Fatigue life .8
5.2.8 Leakage .9
5.2.9 Damage tolerance life .9
5.2.10 Miscellaneous .9
5.3 Material requirements.10
5.3.1 Material selection .10
5.3.2 Material evaluation .10
5.3.3 Material characterization .10
5.4 Fabrication and process control requirements .10
5.4.1 General .10
5.4.2 Contamination control and cleanliness requirements .10
5.5 Quality assurance requirements .11
5.5.1 Quality assurance programme .11
5.5.2 Inspection plan .11
5.5.3 Inspection techniques .11
5.5.4 Inspection data .11
5.5.5 Acceptance test requirements .11
5.6 Operation and maintenance requirements . 12
5.6.1 Operating procedures . 12
5.6.2 Safe operating limit . 12
5.6.3 Inspection and maintenance . 12
5.6.4 Repair and refurbishment . . 13
5.6.5 Storage . 13
5.6.6 Documentation. 13
5.6.7 Reactivation . 13
5.7 Specific qualification test requirements . 13
Bibliography .15

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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.
This second edition cancels and replaces the first edition (ISO 10785:2011), which has been technically
revised.
The main changes are as follows:
— clarification of the Scope;
— updates of the normative references and their citations in the text;
— updates of the terms and definitions to harmonize with the other ISO structural related standards;
— harmonization of requirements with ISO 24638 and ISO 21347.
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
Introduction
The bellows for space systems is usually used under severe conditions, such as high pressure, extremely
low temperatures, large deflection, or high inner flow speed. The design safety factor of the bellows
tends to be small to satisfy two different function requirements simultaneously. One is the function of the
pressure bearing component, which all pressure components have; and the other is the special function to
accommodate installation misalignment, thermal expansion or contraction and displacement induced by
large deformation of the pressurized propellant tank.
There are many items to be considered for design and manufacture such as hoop stress, bulging stress,
buckling strength, flow-induced vibration, and cyclic deflection.
This document aims to ensure safe and reliable bellows hardware and operations.
Some examples of the design safety factors are shown in Annex A.
The requirements in this document are not intended to be different from the requirements also applicable
for bellows included in ISO 24638.

v
International Standard ISO 10785:2025(en)
Space systems — Bellows — Design and operation
1 Scope
This document specifies general and detailed requirements for bellows used in space systems. It establishes
requirements regarding material, design, analysis, fabrication, material, testing, inspection, and operation
for space use.
This document is applicable to metallic bellows which are used as pressure bearing components and are
integrated into a pressure system. This document is not applicable to engine bellows or valve bellows.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 14623, Space systems - Pressure vessels and pressurized structures — Design and operation
ISO 21347, Space systems — Fracture and damage control
ISO 24638, Space systems — Pressure components and pressure system integration
3 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 f
...

FINAL DRAFT
International
Standard
ISO/FDIS 10785
ISO/TC 20/SC 14
Space systems — Bellows — Design
Secretariat: ANSI
and operation
Voting begins on:
Systèmes spatiaux — Soufflets — Conception et fonctionnement 2025-05-16
Voting terminates on:
2025-07-11
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 10785:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 10785:2025(en)
International
Standard
ISO/FDIS 10785
ISO/TC 20/SC 14
Space systems — Bellows — Design
Secretariat: ANSI
and operation
Voting begins on:
Systèmes spatiaux — Soufflets — Conception et fonctionnement
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ISO/FDIS 10785:2025(en) © ISO 2025

ii
ISO/FDIS 10785:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 6
5 Requirements . 6
5.1 General .6
5.2 Design requirements .7
5.2.1 Loads, pressures and environments .7
5.2.2 Strength .7
5.2.3 Stiffness .7
5.2.4 Thermal effects . .8
5.2.5 Stress analysis .8
5.2.6 Leak-before-burst (LBB) failure modes .8
5.2.7 Fatigue life .8
5.2.8 Leakage .9
5.2.9 Damage tolerance life .9
5.2.10 Miscellaneous .9
5.3 Material requirements.10
5.3.1 Material selection .10
5.3.2 Material evaluation .10
5.3.3 Material characterization .10
5.4 Fabrication and process control requirements .10
5.4.1 General .10
5.4.2 Contamination control and cleanliness requirements .10
5.5 Quality assurance requirements .11
5.5.1 Quality assurance programme .11
5.5.2 Inspection plan .11
5.5.3 Inspection techniques .11
5.5.4 Inspection data .11
5.5.5 Acceptance test requirements .11
5.6 Operation and maintenance requirements . 12
5.6.1 Operating procedures . 12
5.6.2 Safe operating limit . 12
5.6.3 Inspection and maintenance . 12
5.6.4 Repair and refurbishment . . 13
5.6.5 Storage . 13
5.6.6 Documentation. 13
5.6.7 Reactivation . 13
5.7 Specific qualification test requirements . 13
Bibliography .15

iii
ISO/FDIS 10785:2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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.
This second edition cancels and replaces the first edition (ISO 10785:2011), which has been technically
revised.
The main changes are as follows:
— clarification of the Scope;
— updates of the normative references and their citations in the text;
— updates of the terms and definitions to harmonize with the other ISO structural related standards;
— harmonization of requirements with ISO 24638 and ISO 21347.
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/FDIS 10785:2025(en)
Introduction
The bellows for space systems is usually used under severe conditions, such as high pressure, extremely
low temperatures, large deflection, or high inner flow speed. The design safety factor of the bellows
tends to be small to satisfy two different function requirements simultaneously. One is the function of the
pressure bearing component, which all pressure components have; and the other is the special function to
accommodate installation misalignment, thermal expansion or contraction and displacement induced by
large deformation of the pressurized propellant tank.
There are many items to be considered for design and manufacture such as hoop stress, bulging stress,
buckling strength, flow-induced vibration, and cyclic deflection.
This document aims to ensure safe and reliable bellows hardware and operations.
Some examples of the design safety factors are shown in Annex A.
The requirements in this document are not intended to be different from the requirements also applicable
for bellows included in ISO 24638.

©
...

ISO/FDIS 10785:2025(en)
ISO/TC 20/SC 14/WG 1
Secretariat: ANSI/AIAA
Date: 2025-04-0230
Space systems — Bellows — Design and operation
Systèmes spatiaux — Soufflets — Conception et fonctionnement
FDIS stage
ISO/DIS FDIS 10785:202X2025(en)
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
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO/FDIS 10785:2025(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 8
5 Requirements . 8
5.1 General. 8
5.2 Design requirements . 9
5.3 Material requirements . 12
5.4 Fabrication and process control requirements . 12
5.5 Quality assurance requirements . 13
5.6 Operation and maintenance requirements . 14
5.7 Specific qualification test requirements . 16
Bibliography . 18

iii
ISO/DIS FDIS 10785:202X2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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.
This second edition cancels and replaces the first edition (ISO 10785:2011), which has been technically
revised.
The main changes are as follows:
— — clarification of the Scope;
— — updates of the normative references and their citations in the text;
— — updates of the terms and definitions to harmonize with the other ISO structural related standards;
— — harmonization of requirements with ISO 24638 and ISO 21347.
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/FDIS 10785:2025(en)
Introduction
The bellows for space systems is usually used under severe conditions, such as high pressure, extremely low
temperatures, large deflection, or high inner flow speed. The design safety factor of the bellows tends to be
small to satisfy two different function requirements simultaneously. One is the function of the pressure
bearing component, which all pressure components have; and the other is the special function to
accommodate installation misalignment, thermal expansion or contraction and displacement induced by large
deformation of the pressurized propellant tank.
There are many items to be considered for design and manufacture such as hoop stress, bulging stress,
buckling strength, flow-induced vibration, and cyclic deflection.
This document aims to ensure safe and reliable bellows hardware and operations.
Some examples of the design safety factors are shown in Annex A.
The requirements in this document are not intended to be different from the requirements also applicable for
bellows included in ISO 24638.
v
ISO/FDIS 10785:2025(en)
Final DRAFT International Standard

Space systems — Bellows — Design and operation
1 Scope
This document specifies general and detailed requirements for bellows used in space systems. It establishes
requirements regarding material, design, analysis, fabrication, material, testing, inspection, and operation for
space use.
This document is applicable to metallic bellows which are used as pressure bearing components and are
integrated into a pressure system. This document is not applicable to engine bellows or valve bellows.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 14623, Space systems - Pressure vessels and pressurized structures — Design and operation
ISO 21347, Space systems — Fracture and damage control
ISO 24638, Space systems — Pressure components and pressure system integration
3 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 3.1
acceptance test
required formal test conducted on flight hardware to ascertain that the materials, manufacturing processes
and workmanship meet specifications and that the hardware is acceptable for intended usage
[SOURCE: ISO 14623:2003, 2.2]
3.2[SOURCE: ISO 14623:2003, 2.2]
3.2
bellows
corrugated single-layer or multi-layer elastic casing, when integrated into a duct assembly, capable of
performing linear, shear and angular movements
Note 1 to entry: A bellows consists of both a convolution section and a mechanical linkage section (3.23(3.23),), which
serves as a bellows restraint. The most common mechanical linkage types are gimbal-type and braided-type. In some
cases, a bellows contains an internal liner or flow tube for the purpose of improving flow capability.
ISO/DIS FDIS 10785:202X2025(en)
Note 2 to entry: See Figure 1Figure 1.

Key
1 internal pressure
Figure 1 — Bellows
3.3 3.3
bellows stiffness
ratio between an applied force and the resulting bellows (3.2(3.2)) displacement
3.4 3.4
bulging stress
meridional or axial stress at the convolution section induced by pressure
3.5 3.5
component
set of materials, 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: ISO24638:2021, 3.4]
3.6
[SOURCE: ISO24638:2021, 3.4]
3.6
damage tolerance life
safe life

ISO/FDIS 10785:2025(en)
design criterion under which failure due to the presence of flaws (3.15(3.15)) does not occur in the expected
environment during the service life (3.29(3.29))
Note 1 to entry: In this design criterion, a flaw (3.15(3.15)) is assumed consistent with the inspection process specified
and it is shown that the largest undetected flaw that can exist in the structure will not grow to failure in durations
multiplying life factors (3.19(3.19)) to service lifetimes when subjected to the cyclic and sustained loads in the
environments encountered.
3.63.7 3.7
damage tolerance life
safe life

required period during which a structural item, even containing the largest undetected flaw (3.15(3.15),), is
shown by analysis or testing not to fail catastrophically under the expected service load and environment

3.73.8 3.8
deflection
contraction or expansion along its longitudinal axis, angular rotation, or lateral offset
Note 1 to entry: See Figure 2Figure 2.

Key
1 axial deflection
ISO/DIS FDIS 10785:202X2025(en)
2 angular rotation
Figure 2 — Deflection
3.83.9 3.9
design burst factor
multiplying factor applied to maximum expected operating pressure (MEOP) (3.22(3.22)) or maximum design
pressure (MDP) (3.21(3.21)) to obtain the design burst pressure (3.10(3.10))
3.93.10 3.10
design burst pressure
burst pressure
differential pressure that pressurized hardware must withstand without bursting in the applicable
operational environment
Note 1 to entry: Design burst pressure is equal to the product of the maximum expected operating pressure (MEOP)
(3.22(3.22)) or maximum design pressure (MDP) (3.21(3.21)) and a design burst factor (3.9(3.9).).
[SOURCE: ISO 24638:2021,3.7]
3.11
[SOURCE: ISO 24638:2021,3.7]
3.11
design safety factor
safety factor
design factor of safety
factor of safety
multiplying factor to be applied to limit loads (3.20(3.20)) and/or maximum expected operating pressure
(MEOP) (3.22(3.22))
Note 1 to entry: The factor is defined in order to account for the statistical variations of loads and structural strength, and
inaccuracies in the knowledge of their statistical distributions.
Note 2 to entry: In this definition, the word maximum expected operating pressure (MEOP) (3.22(3.22)) may be replaced
by maximum design pressure (MDP) (3.21(3.21).).
[SOURCE: ISO 24638:2021, 3.8, modified — The word “maximum design pressure (MDP)“has
been deleted from the definition statement. Note 1 and Note 2 to entry have been added.]
3.12[SOURCE: ISO 24638:2021, 3.8, modified — "or maximum design pressure (MDP)" has been removed, and
Note 1 and Note 2 to entry have been added.]
3.103.12
detrimental deformation
structural deformation, deflection or displacement that prevents any portion of the structure or other system
from performing its intended function or that jeopardizes mission success
[SOURCE: ISO 24638:2021, 3.9]
3.13[SOURCE: ISO 24638:2021, 3.9]
ISO/FDIS 10785:2025(en)
3.113.13
fatigue
process of progressive localized permanent structural change occurring in a material/structure subjected to
conditions which produce fluctuating stresses and strains at some point or points and which may culminate
in cracks or complete fracture (3.16(3.16)) after a sufficient number of fluctuations
[SOURCE: ISO 14623:2003, 2.23]
3.123.14 3.14
fatigue life
number of cycles of stress or strain of a specified character that a given structure or component of a structural
assembly can sustain [without the presence of flaws (3.15(3.15)])] before failure of a specified nature occurs
[SOURCE: ISO 10786:2011, 2.24]
3.15
[SOURCE: ISO 10786:2011, 2.24]
3.15
flaw
local discontinuity in a structural material
EXAMPLES Crack, cut, scratch, void, delamination disbond, impact damage and other kinds
of
...