ISO 16454:2007

INTERNATIONAL ISO
STANDARD 16454
First edition
2007-11-01
Space systems — Structural design —
Stress analysis requirements
Systèmes spatiaux — Conception des structures — Exigences relatives
à l'analyse des contraintes
Reference number
©
ISO 2007
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©  ISO 2007
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ii © ISO 2007 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Requirements . 5
4.1 General. 5
4.2 Basic data . 5
4.3 Analysis methodology and software . 7
4.4 Structural mathematical model . 7
4.5 Structure mathematical model check. 8
4.6 Failure modes. 8
4.7 Critical location analysis. 9
4.8 Determination margins of safety. 9
4.9 Report . 10
Annex A (informative) Structural mathematical model check . 11

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16454 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 14, Space systems and operations.
iv © ISO 2007 – All rights reserved

Introduction
From the beginning of the space age, structural integrity verification has been one of the main fields of
mechanical specialists’ activity. Mission failure and potential danger to human life, expensive ground
constructions and other public and private property are the most probable consequences in the case of space
structural integrity failure. Static strength is one of the most important critical conditions for structural integrity
analysis. It is usually the main criteria for space structure weight evaluation. If the space structure is too heavy,
the mission could be extremely expensive or impossible to achieve. If the space structure is underdesigned, it
could result in structural failure, leading to high risk associated with safety of life, and loss of expensive
hardware and other property. It is therefore necessary to specify unique requirements for static strength
analysis in order to provide cost effective design and light-weight, reliable and low risk structures for space
application.
The analysis and design of space structures has a long history. This International Standard establishes the
preferred requirements related to these techniques for static strength critical condition.

INTERNATIONAL STANDARD ISO 16454:2007(E)

Space systems — Structural design — Stress analysis
requirements
1 Scope
This International Standard is intended to be used for the determination of the stress/strain distribution and
margins of safety in launch vehicles and spacecraft primary structure design. Liquid propellant engine
structures, solid propellant engine nozzles and the solid propellant itself are not covered, but liquid propellant
tanks, pressure vessels and solid propellant cases are within the scope of this International Standard.
This International Standard provides requirements for the determination of maximum stress and
corresponding margin of safety under loading, and defines criteria for static strength failure modes, such as
rupture, collapse and detrimental yielding. Critical conditions associated with fatigue, creep and crack growths
are not covered. Notwithstanding these limitations in scope, the results of stress calculations based on the
requirements of this International Standard are applicable to other critical condition analyses.
In accordance with the requirements of this International Standard, models, methods and procedures for
stress determination can also be applied to the displacements and deformation calculations, as well as to the
loads definition, applied to substructures and structural members of structures under consideration. When this
International Standard is applied, it is assumed that temperature distribution has been determined and is used
as input data.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 14622, Space systems — Structural design — Loads and induced environment
ISO 14623, Space systems — Pressure vessels and pressurized structures — Design and operation
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
A-basis allowable
mechanical strength value above which at least 99 % of the population of values is expected to fall, with a
confidence level of 95 %
3.2
allowable load
allowable stress
allowable strain
maximum load (stress, strain) that can be accommodated by a material/structure without potential rupture,
collapse or detrimental deformation in a given environment
NOTE Allowable loads (stresses, strains) commonly correspond to the statistically based minimum ultimate strength,
buckling strength and yield strength, respectively.
3.3
basic data
input data required to perform stress analysis and to determine margins of safety
3.4
B-basis allowable
mechanical strength value above which at least 90 % of the population of values is expected to fall, with a
confidence level of 95 %
3.5
collapse
failure mode induced by quasi-static compression, shear or combined stress, accompanied by very rapid
irreversible loss of load resistance capability
3.6
composite material
combination of materials different in composition or form on a macro scale
NOTE 1 The constituents retain their identities in the composite.
NOTE 2 The constituents can normally be physically identified, and there is an interface between them.
3.7
creep
process of a permanent material deformation resulting from long duration under constant or slowly altered
load
NOTE The ultimate creep deformation, corresponding to the loss of material integrity is often much larger than
ultimate deformation in the case of short time loading.
3.8
critical condition
most severe environmental condition in terms of load and temperature, or combination thereof, imposed on a
structure, system, subsystem or component during service life
3.9
critical location
structural point at which rupture, local buckling or detrimental deformation will first lead to structural failure
3.10
design safety factor
coefficient by which limit loads are multiplied in order to account for the statistical variations of loads and
structure resistance, and inaccuracies in the knowledge of their statistical distributions
3.11
destabilizing load
load that produces compressive stress at critical location
3.12
detrimental yielding
〈metallic structures〉 permanent deformation specified at the system level to be detrimental
3.13
development test
test to provide design information that can be used to check the validity of analytic technique and assumed
design parameters, to uncover unexpected system response characteristics, to evaluate design changes, to
determine interface compatibility, to prove qualification and acceptance procedures and techniques, to check
manufacturing technology, or to establish accept/reject criteria
2 © ISO 2007 – All rights reserved

3.14
flight-type hardware test
test of a flight structure article, a protoflight model, a representative special model or a structural element
fabricated with the same or close to flight hardware technology
3.15
gauges
thickness and other structure dimensions which relative scattering could result in significant effect on stress
levels and/or margin of safety
3.16
knockdown coefficient
empirical coefficient, other than design safety factor, which is used to determine analytically in a simple way
actual or allowable loads or stresses, and which is defined on the basis of test results of flight-type structures,
model structures or structural members as compared with corresponding stress analysis data
3.17
limit load
maximum that can be expected during service life and in the presence of the environment
NOTE For stabilizing loads, the limit load is the minimum load.
3.18
loads
volume forces and moments, concentrated and/or distributed over the structure surfaces or structure, caused
by its interaction with environment and adjacent parts of vehicle, and accelerations
NOTE This includes pressures, external loads and enforced displacements acted at considered structural element,
pretension, inertial loads caused by accelerations and thermal gradients.
3.19
loading case
particular condition described in terms of loads/pressures/temperatures combinations, which can occur for
some parts of structure at the same time during its service life
3.20
local buckling
failure mode, which occurs when an alternative equilibrium mode of a structural member exists, and which
could lead to detrimental deformation or rupture of that member if it occurs under loading
3.21
margin of safety
M
S
expression of the margin of the limit load multiplied by design safety factor against the allowed load
Another representation of the concept:
⎛⎞
F
AL
M=−1 (1)
⎜⎟
S
fF×
⎝⎠DS LL
where
F is the allowable load under specified functional conditions (e.g. yield, rupture, collapse, local
AL
buckling);
F is the limit load;
LL
f is the design safety factor.
DS
NOTE Load can imply corresponding stress or strain.
3.22
minimum allowable
minimum material mechanical properties warranted by the supplier
3.23
pressure
external load caused by fluid action on a structural surface
NOTE The terms “pressure” and “load” are sometimes referred to simultaneously in this International Standard.
3.24
primary structure
part of a vehicle that carries the main loads and/or defines the fundamental resonance frequencies
3.25
rupture
loss of integrity by structure material differed from fatigue and ultimate creep deformation attainment, which
could prevent the structure from withstanding load combinations
3.26
semi-finished item
product that is used for structure manufacturing or assembling
EXAMPLE Sheets, plates, profiles, strips, etc.
3.27
stabilizing load
load which decreases compressive stresses if applied in conjunction with destabilizing loads
3.28
static strength
property of a structure, characterized by its capability to withstand loads and temperature combinations
without rupture, collapse, detrimental local buckling and detrimental deformation
3.29
strength failure mode
condition of a structure or a structural member considered as a critical condition in accordance with stress
analysis results
3.30
stress analysis
analytical procedure to determine structure stress/strain distribution, deformations and margins of safety
3.31
structure
primary structure, unit attachments, pressure/loads carrying elements of pressure vessels, loads carrying
elements of appendages
3.32
structural mathematical model
analytical or digital presentation of a structure
NOTE It is advisable that the model provides adequate description of the structure's response under
loads/pressures/temperatures.
3.33
ultimate load
limit load multiplied by ultimate design safety factor
3.34
unit
part of a vehicle which is designed mainly to provide vehicle functioning and which differs from a structure
4 © ISO 2007 – All rights reserved

4 Requirements
4.1 General
For structures used in space systems, such as launch and space vehicles, the stress analysis and
corresponding determination of margin of safety for various static strength failure modes shall meet the
requirements specified in this International Standard.
Basic data, structural models, methods for stress analysis and strength criteria are considered critical for the
successful completion of these procedures.
Unless otherwise noted below, there are no limitations set out in this International Standard that restrict the
use of results from stress calculations for other applications.
4.2 Basic data
4.2.1 General
Basic data used for space structure stress analyses shall meet the requirements included in 4.2
Basic data shall include all the following information:
⎯ structural configuration, geometry and gauges,
⎯ structural materials and their properties, and
⎯ loading case list, load and temperature combinations, and corresponding design safety factors for every
loading case.
4.2.2 Structural configuration, geometry and gauges
4.2.2.1 Structural configuration, geometry and gauge data (with tolerances) used for stress analyses shall
correspond to drawings representing a relevant design stage.
4.2.2.2 The choice of particular thickness (minimum or nominal) for stress analyses shall be subject to
national regulatory requirements. Otherwise, the following factors shall be taken into account:
⎯ conservatism of applied safety factors and knockdown coefficients;
⎯ correspondence between applied thickness and procedure for knockdown coefficient determination;
⎯ stress analysis results dependence on and sensitivity to thickness;
⎯ simplification of stress analysis procedure application;
⎯ linear or non-linear behaviour.
4.2.2.3 Structural configuration, geometry and gauge data (with tolerance) shall be sufficient to
substantiate a given structural analytical model and to determine the corresponding parameters.
4.2.3 Structural materials and their properties
4.2.3.1 This entire subclause (4.2.3) refers to individual material properties for any individual part of the
structure (junctions) for which the stress analyses require allowable values.
4.2.3.2 A list of materials used for the fabrication of the structure and its members shall correspond to the
design and technology documentation. The information about types of materials, semi-finished items and
tec
...