ISO TC 20/SC 14 N 1

Date:   2023-11-13

ISO/CD 22010

ISO TC 20/SC 14/WG 1

Secretariat:   ANSI

Space systems --- Mass properties control

*Systèmes spatiaux --- Gestion du devis du masse*

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Contents Page

Foreword [iv](#__RefHeading___Toc54532860)

Introduction [v](#__RefHeading___Toc54532861)

1 Scope [1](#scope)

2 Normative references [1](#normative-references)

3 Terms and definitions [1](#terms-and-definitions)

4 Symbols and abbreviated terms [3](#symbols-and-abbreviated-terms)

5 Mass properties control plan [3](#mass-properties-control-plan)

5.1 General [3](#general)

5.2 Control process [3](#control-process)

5.2.1 Basis of the process [3](#basis-of-the-process)

5.2.2 Requirements definition [4](#requirements-definition)

5.2.3 Mass reduction plan [4](#mass-reduction-plan)

5.2.4 Mass Properties Control Board [4](#mass-properties-control-board)

5.2.5 Mass allocation and trend analysis
[4](#mass-allocation-and-trend-analysis)

5.2.6 Mass properties monitoring [5](#mass-properties-monitoring)

5.2.7 Subcontractor mass properties control
[5](#subcontractor-mass-properties-control)

5.3 Documentation [5](#documentation)

5.3.1 General [5](#general-1)

5.3.2 Control Plan [5](#control-plan)

5.3.3 Report Plan [5](#report-plan)

5.3.4 Analysis Plan [5](#analysis-plan)

5.3.5 Verification Plan [5](#verification-plan)

5.3.6 Status Reports [6](#status-reports)

5.3.7 Trend Analysis Reports [6](#trend-analysis-reports)

5.4 Analysis [7](#analysis)

5.4.1 General [7](#general-2)

5.4.2 Flight hardware analysis [7](#flight-hardware-analysis)

5.4.3 Ground handling [8](#ground-handling)

5.4.4 Special Analyses [8](#special-analyses)

5.4.5 Verification [9](#verification)

Annex A (informative) Mass growth guidelines
[11](#__RefHeading___Toc54532890)

Bibliography [12](#__RefHeading___Toc54532891)

Figures

[Figure 1 --- Mass control parameters 2](#__RefHeading___Toc65322229)

[Figure 2 --- Programme mass tracking 7](#__RefHeading___Toc65322230)

Tables

[Table A.1 --- Mass growth allowance as a function of design maturity
11](#__RefHeading___Toc15728067)

[]{#__RefHeading___Toc54532860 .anchor}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 3.

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.

ISO 22010 was prepared by Technical Committee ISO/TC 20, *Aircraft and
space vehicles*, Subcommittee SC 14, *Space systems and operations*.

> []{#__RefHeading___Toc54532861 .anchor}Introduction
>
> This International Standard establishes the minimum requirements for
> providing adequate control of the mass properties of space systems to
> meet mission requirements. In addition, many recommended practices
> that add value to the mass properties monitoring tasks are presented.
> Throughout this international standard, the minimum essential criteria
> are identified by the use of the key word "shall." Recommended
> criteria are identified by the use of the key word "should," and while
> not mandatory, are considered to be of primary importance in providing
> timely and accurate mass properties support for contracts. Deviations
> from the recommended criteria should only occur after careful
> consideration and thorough evaluation have shown alternative methods
> to be satisfactory.
>
> The requirements may be tailored for each specific space program
> application.

Space systems --- Mass properties control

# Scope

This International Standard describes a process for managing,
controlling, and monitoring the mass properties of space systems. The
relationship between this management plan and the performance parameters
for mass and stability to be met throughout the mission are described.
Ground handling, dynamics analysis and test set ups that rely on
accurate mass properties inputs are identified. This standard covers all
program phases from pre-proposal through end of life.

# Normative references

The following normative documents contain provisions which, through
referenced in this text, constitute provisions of this International
Standard. For dated references, subsequent amendments to, or revisions
of, any of these publications do not apply. However, parties to
agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the
normative documents indicated below. For undated references, the latest
edition of the normative document referred to applies. Members of ISO
and IEC maintain registers of currently valid International Standards.

ISO DIS 15864 Space systems -- General test standard for spacecraft,
subsystems, and units

ISO CD 22108 Space systems -- Non-flight items in flight hardware --
Identification and control

# Terms and definitions

For the purposes of this International Standard, the following terms and
definitions apply.

3.1

Basic mass properties

::: Definition
Best engineering estimate based on an assessment of the most recent
baseline design, excluding mass growth allowance.
:::

3.2

Calculated properties

::: Definition
Mass properties determined from released drawings or controlled computer
models.
:::

3.3

Contractor limit

::: Definition
Predicted mass plus a contractor margin to allow for uncertainties
during the design cycle.
:::

3.4

Contractor margin/system margin

::: Definition
Difference between the contractor limit and the predicted mass.
:::

3.5

Customer reserve

::: Definition
Allowance defined by the customer according to the agreements of the
contract.
:::

3.6

Estimated properties

::: Definition
Mass properties determined from preliminary data, such as sketches or
calculations from layout drawings.
:::

3.7

Mass control parameters

::: Definition
Factors used as an indicator of the current mass, predicted mass, and
margins/limits for a space system.
:::

3.8

Mass growth allowance

::: Definition
Predicted change to the basic mass based on an assessment of the design
maturity, allowing for design changes and evolutions during development
that may occur, excluding configuration changes due to major contract or
requirements changes. This allowance is not meant to be a tolerance.
:::

NOTE Figure 1 is an illustration of related terms commonly used in
reporting mass properties during the development of space systems
hardware.

[]{#__RefHeading___Toc65322229 .anchor}![](media/image1.wmf)Figure 1 ---
Mass control parameters

3.9

Mass properties

::: Definition
Mass, centre of gravity, moments of inertia, and products of inertia.
:::

3.10

Mass properties categories

::: Definition
Criteria used to indicate the confidence in or maturity of the design.
:::

3.11

Mass properties engineer (MPE)

::: Definition
A project engineer trained specifically in the discipline of mass
properties engineering.
:::

3.12

Measured properties

::: Definition
Mass properties determined by measurement or by comparison of nearly
identical components for which mass properties are available.
:::

3.13

Mission limit

::: Definition
Maximum mass that can still satisfy all of the mission performance
requirements.
:::

3.14

Predicted mass

::: Definition
Sum of the basic mass and the mass growth allowance; intended to
estimate the final mass at system delivery.
:::

3.15

Space systems

::: Definition
Launch vehicles, satellites, space vehicles, or components thereof.
:::

# Symbols and abbreviated terms

ACS attitude control system

AIAA American Institute of Aeronautics and Astronautics

ANSI American National Standards Institute

ATP authorization to proceed

CAD computer aided design

CDR critical design review

CFE customer furnished equipment

GSE ground support equipment

IPT integrated product team

MPCB mass properties control board

MPE mass properties engineer

NTE not-to-exceed

PDR preliminary design review

SAWE Society of Allied Weight Engineers

TPM technical performance measurement

# Mass properties control plan

## General

A mass properties control plan should be documented.

A mass properties control plan should be based on the critical
parameters that need to be controlled. In some cases, that may only be
mass. In the extreme, a spin-stabilized space system may have a set of
requirements that warrant control of all the mass properties, including
final measurements of mass, centre of mass, and moments and products of
inertia. The depth and detail of analysis, reporting, and testing shall
be reflective of the critical parameters.

## Control process

### Basis of the process

The mass properties control process shall be started in the pre-proposal
or conceptual design phases, where an initial mass budget is
established. An MPE, or an integrated product team member who has been
trained in the mass properties discipline, shall be a member of the
preliminary design centre or the proposal team in order to guide
subsystem and component mass allocations and the launch vehicle
selection process, if applicable. This team member should also be
supported by other members who have previous experience in the
allocation process.

NOTE Space system stability is a prime concern. Without early mass
properties control there is a high risk of performance, schedule, and/or
cost problems later in the program.

The control process after authorization to proceed may include one or
more of the following elements:

a)  understanding of the flow-down of requirements that affect mass
    properties analysis and test plans

b)  a successful mass reduction plan

c)  implementation of a Mass Properties Control Board (MPCB)

d)  mass allocation and trend analysis

e)  mass properties monitoring

f)  subcontractor mass control

Application of some of the more stringent elements listed above is
contingent on available mass and stability margins, cost considerations,
and the planned verification (measurement vs. analysis) schema. The
various elements and their applicability are discussed below.

### Requirements definition

There shall be a review of all requirements that affect mass properties,
including but not limited to the contractual, attitude control, mission,
and ground handling requirements. Different space systems have different
mass properties requirements.

EXAMPLE A space system that is spin-stabilized throughout its mission
requires a finer balance than one that is 3-axis stabilized.

### Mass reduction plan

After establishing a credible mass summary during the proposal phase, a
database shall be used with the tools necessary to develop a projected
mass for the space system at delivery. A contractor or system mass
margin against the contractor limit should be determined. If the mass
margin is not sufficient, a rigorous mass reduction program should be
initiated. In this case, the program office should fully support the
effort.

NOTE Mass reduction generally is a costly undertaking, and program
offices should allocate sufficient budget to accomplish the goal. An
historical database of previous weight reduction ideas is recommended.

### Mass Properties Control Board

In conjunction with a mass reduction plan, a Mass Properties Control
Board may be convened to audit the mass properties database, critically
review designs for optimum mass, and perform cost/mass trades as well as
review margins. The Board should have at least one of its members
trained in mass properties analysis as well as have program office and
systems engineering representation. Some of the MPCB members should also
have previous experience with this process. The MPCB should have the
authority to direct design changes that reduce mass, within the
considerations of cost, schedule, and technical performance. MPCB
members should attend all design reviews to ensure that mass
optimisation is considered.

### Mass allocation and trend analysis

One of the most effective ways to control mass is to set not-to-exceed
(NTE) allocations at the subsystem or unit level. Referring to Figure 1,
if the contractor margin at the beginning of the program is small or
negative, it may be necessary to challenge each subsystem manager in
order to ensure that the contractor limit will not be exceeded. The same
idealized chart can be used to represent each subsystem's mass target,
or NTE allocation. These technical performance measurement charts should
be used to monitor the progress of each subsystem. If the predicted mass
exceeds the NTE allocation, mass reduction is necessary; in some cases,
a re-allocation among subsystems may solve the problem. This trend
analysis is particularly critical prior to preliminary design review,
when designs are still evolving, and mass reduction efforts are less
costly.

### Mass properties monitoring

For programmes with adequate margins in all mass properties parameters,
a simple mass history chart and a table showing the predicted mass
properties versus the requirements will suffice. The chart and table
should be included in periodic reports to the customer (refer to
subclause 5.3.6 on status reports).

### Subcontractor mass properties control

It is suggested that a MPE be involved in the development of NTE masses
in the procurement specification that is issued to subcontractors. If
additional controls, such as centre of mass or inertia, are required,
those NTE values shall also be added to the specification and contract.
The status of the critical values shall be reported by the subcontractor
in periodic reports as specified by the contractor. If mass reduction is
needed to bring the deliverable items within specification, the Program
Office may want to set up regular meetings with the subcontractor
(including a mass review board) until the problem is mitigated, or until
all avenues for meeting the specification have been exhausted.
Incentives and penalties against specification values written into the
contract may be of use.

## Documentation

### General

Mass properties documentation consists of plans and reports. Plans
define the programme management methods for controlling, reporting, and
measuring mass properties. Reports provide visibility into the hardware
configuration and design maturity through the development process.

### Control Plan

The overall control plan described in subclauses 5.1 and 5.2 shall be
documented in order to provide an organized process that can be
implemented early in the development phase and carried through to
hardware delivery. The control plan should contain the elements of the
control process in subclause 5.1, as applicable, as well as a reporting
plan and a verification plan.

### Report Plan

Report format and frequency of delivery may be specified in the
contract. An initial report may be expected one month after ATP. Formal
monthly reports should be provided through critical design review, with
quarterly reports thereafter. For mass critical programs, a weekly mass
update may be required. A final test report provides the customer with
the measured space system\'s mass properties from which mission
predictions are made.

### Analysis Plan

In some cases, full space systems analysis using CAD systems may not be
possible, due to resource limitations. In other cases, parametric data
from other programs may prove to be accurate enough until
program-specific hardware measurements are taken. In those cases, an
analysis plan should be documented, informing the customer of the risk
to the mathematical model.

### Verification Plan

The verification plan shall define the methods to be used to verify the
mass properties data. The plan shall address the process for determining
part, unit, subassembly, and assembly level verification. The
verification plan should be formulated in the early stages of the
program.

EXAMPLE Mass properties measurement requirements can affect the hardware
design. Thus, procurement of long lead measurement devices, such as
adapters and handling equipment, may be required.

The plan shall define the method of verification -- analysis or test --
for each mass properties parameter. If margins are small, an uncertainty
analysis should be performed to verify that analysis is sufficient. A
more detailed plan, including which units, parts, subassemblies, or
modules are to be weighed, may be delivered to manufacturing planning
for implementation. A note should be placed on each detail or assembly
drawing defining which items should be weighed. On programs with
multiple identical space systems, it may be sufficient to weigh only the
first serial number at the detail part or unit level. Such information
shall be transmitted to manufacturing.

### Status Reports

A report format shall be established that satisfies the needs of the
customer, program office, and the other internal customers who rely on
the timely transmittal of mass properties information.

Periodic status reports provide insight to the space system's mass
properties throughout development. The report may consist of a full set
of mass properties, or a subset thereof, depending on the contractual
requirement for reporting. In some cases, where margins are large and
control systems robust, reporting total predicted mass is sufficient.
The level of detail to be reported may also vary.

EXAMPLE Typically the details of the masses for the components within an
electronic box are not required, so there may be a request to report
only the predicted total mass of the unit. Conversely, at certain points
in the program, the customer may want to view the entire detail mass
properties database for an independent review.

The report plan in subclause 5.3.3 shall specify the level of detail
required.

### Trend Analysis Reports

Trend analysis reports may be submitted as part of the status report
mentioned in subclause 5.3.6, or may be submitted separately. The space
system mass trend analysis is simply the summation of the subsystem TPM
mentioned in subclause 5.2.5, with the mission and contractor limits
specified. Charts tracking centre of mass or moments of inertia may be
developed, if those parameters are critical.

Figure 2 illustrates the effects of large uncertainties and lack of mass
control in the early stages of a programme. By month 5, in this example,
mass reduction techniques are implemented, and the mass begins to
decrease. By month 13, the design maturity is advanced enough to
evidence a steady decrease in the mass growth allowance. By month 24,
measured masses are available, and the basic and predicted masses
converge.

The mass growth allowance applied to the basic mass shall be directly
related to the maturity of the design. The maturity of each component,
unit, or assembly shall be categorized and assigned a percentage of mass
growth. As the design evolves, the mass growth should decrease. This
should be a continuous process that is captured in each status report.
Applying the mass growth allowance at the part level generally provides
the most accurate representation of programme mass status.

Each contractor shall develop its own set of mass growth percentages
based on its historical data. In the absence of historical data, Table
A.1 in Annex A may be used.

![](media/image2.wmf)

[]{#__RefHeading___Toc65322230 .anchor}Figure 2 --- Programme mass
tracking

## Analysis

### General

Mass properties analysis follows the methodology defined in the Mass
Properties Control Plan and provides direct input to the various
reports. The analyses should be divided into three main categories:

-   flight hardware,

-   ground handling,

-   special analysis.

### Flight hardware analysis

All new subsystems, units, and components may be subject to detailed
analysis. These may include but are not limited to the following
subsystems.

-   antenna,

-   wave guide and/or coax cables,

-   electrical/electronic components,

-   structure,

-   thermal,

-   propulsion,

-   batteries, solar arrays and/or other power sources,

-   wire harnesses,

-   mechanisms,

-   instrumentation.

There shall be an analytical database maintained that accurately
represents the space system's mass properties throughout the mission,
including launch, transfer orbit, on-station, and return (if
applicable). Software shall be capable of performing changes in
configuration such as deployments and fuel depletion.

### Ground handling

Analysis of the combined ground support equipment and flight hardware
may be required during integration and test operations. Mass and centre
of mass of various subassemblies or modules of flight hardware shall be
analysed for the design of GSE, location of pickup points, rollover
characteristics, and stability during handling. The mass properties
database should have enough detail, and the software versatile enough to
predict the mass properties of these unique configurations accurately.
Non-flight items forming part of the configuration should be weighed and
incorporated into the data reduction process.

### Special Analyses

#### General

There are several special analyses that may be requested. These requests
are generally made by internal customers, such as Structural Analysis,
Flight Mechanics, Mission Control, Manufacturing, Ground Support
Operations, Special Test Equipment, Packaging, Transportation, Dynamics,
Attitude Control, or Payload Layout Design.

#### Layout analysis

Mass properties considerations, such as optimisation of equipment from a
balance standpoint, should be taken into account during the layout
process.

#### Mass distribution analysis

The stress and dynamics analysis organizations may request a mass
distribution for use in developing loads, and for accurately predicting
load concentrations that may require local strengthening. A sort
capability in the mass properties software would greatly facilitate this
analysis.

#### Balance mass analysis

On space systems requiring static or dynamic balancing, mass properties
considerations should be taken into account along with structural design
to provide the optimum locations and configuration of the proposed
balance weights. Special requirements, such as thermal finish, shall be
addressed in the design of the weights. Stress and dynamics engineers
should analyse the support schemes for the weights.

#### Mission/attitude control system analysis

There are mass properties interfaces with the Mission and ACS
organizations in the iterative process of defining propellant budgets
and deployment schemes. A separate file in a special format may be
requested by ACS to perform their analyses. In the data interchange with
ACS, the mass properties shall indicate whether a positive or negative
integral is used in the determination of the products of inertia.

#### Uncertainty analysis

There shall be knowledge of the approximate uncertainty in the space
system's mass properties at key points in the programme.

The uncertainty may be based on historical or comparative data, or may
be rigorously derived. The mass growth allowance will normally encompass
design uncertainties associated with design maturities for Estimated,
Layout and Pre-Release Drawing maturity categories. In special cases
where the mass growth allowance figures are believed too inaccurate, a
rigorous uncertainty analysis based on raw uncertainty data can be
performed.

### Verification

#### General

Mass properties verification is the confirmation that the required mass
properties are known within the established limits. The following
subclauses provide criteria for determining which mass properties
require verification and how best to meet these requirements.

#### Determining mass properties verification requirements

Based on individual program requirements, specific flight events
generally require specific knowledge of flight mass properties and the
allowable tolerances on these values. The mass properties shall be
defined early in the design process and controlled within defined
tolerances. A wide tolerance of mass properties may be acceptable, but
an exact knowledge of the space system or parts thereof shall be
available. The critical mass properties for selected assemblies or for
the total space systems shall be defined.

#### Determining mass properties limits

The allowable limits of the mass properties parameters generally define
two distinct criteria to be established in the verification program:

a)  establish acceptance criteria for the hardware assembly in terms of
    maximum and minimum mass, centre of mass location, and moments and
    products of inertia that are consistent with the verification
    requirements, and

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g)  establish the accuracy required in conducting the measurements in
    the verification process that is consistent with the verification
    requirements.

The mass properties limits shall be defined in the verification plan and
addressed in the specific procedures used to determine these parameters.

#### Mass properties verification process

##### General

Verification may be accomplished by direct or indirect measurement, by
analysis, or by a combination of both methods. Based on the accuracy
required, methods of verification shall be selected that are consistent
with the required levels of accuracy at each phase of the assembly.
Verification shall be performed in accordance with the verification
plan.

##### Verification requirements

A verification matrix shall be prepared that identifies which system
level mass properties shall be verified by test, which by analysis, and
which by a combination of the two methods. With customer and program
office approval, this plan should be flowed down to lower levels of
assembly to determine which units, parts, or subassemblies should be
measured. The verification methods should be selected early enough in
the program to provide time for acquisition, modification, or
preparation of measurement equipment and sites. Verification should be
performed at a low enough piece part level to adjust the calculated
values of the mass properties not being verified by test.

##### Verification procedures

Mass properties measurement tests shall be conducted in accordance with
program procedures that are approved and documented. The procedures
shall contain stated goals of the test that are determined by
requirements.

EXAMPLE ISO 15864 includes a dynamic balance test.

##### Notification of measurement

This subclause deleted.

##### Test conditions

The test article shall be flight representative and should be no less
than 90% of the total flight mass, excluding propellant and explosive
devices, and with minimal non-flight hardware installed. The
configuration shall be verified and mass properties related data for all
missing items, non-flight items installed, other items that may be
different from the flight model and tare items recorded. A log of
non-flight items shall be established according to the requirements in
ISO 22108.

##### Data records

Mass properties verification data shall be documented and made available
for review on the current programme as well as archived for reference on
future programmes.

A.  []{#__RefHeading___Toc54532890 .anchor}(informative)\
    Number range aaaNumber range TableNumber range Figure\
    Mass growth guidelines

The following table represents a compilation of historical data from
several sources. In some cases, the percent ranges are quite large.
However, for a contractor with limited experience, or a relatively small
database of programmes, the average percent in each category should be a
good indicator for the mass growth of the overall space system. Note
that the table below is derived from current existing technology
applications and may not apply to newer technology applications. For
impacts of newer technologies, modifications of Table A.1 may be
required.

[]{#__RefHeading___Toc15728067 .anchor}![](media/image1.wmf)Table 1 ---
Mass growth allowance as a function of design maturity

[]{#__RefHeading___Toc54532891 .anchor}Bibliography

American Institute of Aeronautics and Astronautics, ANSI/AIAA
R-020A-1999, *Recommended Practice ― Mass Properties Control for
Satellites, Missiles, and Launch Vehicles*

United States Department of Defense, Military Handbook 1811
(MIL-HDBK-1811), Mass *Properties Control for Space Vehicles*

Society of Allied Weight Engineers, *SAWE Recommended Practice Number
11* (RP-No. 11)*, Mass Properties Control for Space Vehicles*