ISO 20893:2021

INTERNATIONAL ISO
STANDARD 20893
First edition
2021-02
Space systems — Detailed space
debris mitigation requirements for
launch vehicle orbital stages
Systèmes spatiaux — Exigences détaillées pour la limitation des
débris spatiaux relatifs aux étages orbitaux des lanceurs
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Avoiding the intentional release of space debris into Earth orbit during normal
operations . 1
5 Avoiding break-ups in Earth orbit . 2
5.1 Accidental break-up caused by an on-board source of energy . 2
5.1.1 General. 2
5.1.2 Residual propellants in propulsion systems . 2
5.1.3 Pressurized gasses in pressure vessels . 2
5.1.4 Batteries . 3
5.1.5 Range safety systems . 3
5.1.6 Probability of accidental break-up due to internal causes . 3
5.2 Accidental break-up caused by a collision . 3
6 Disposal of a launch vehicle orbital stage after the end of mission so as to minimize
interference with the protected regions . 3
6.1 Launch service provider — spacecraft mission designer coordination . 3
6.2 Selection of disposal option . 4
6.2.1 Disposal to minimize interference with the geostationary Earth orbit
(GEO) protected region . 4
6.2.2 Disposal to minimize interference with the low Earth orbit (LEO)
protected region . 4
6.3 Probability of successful disposal. 5
6.4 Contingency planning . 5
7 Re-entry . 5
8 Planning and documentation . 6
8.1 General . 6
8.2 Break-up prevention plan . 6
8.3 End of mission disposal plan . 6
8.4 Re-entry plan . 7
8.5 Documentation . 7
Bibliography . 8
Foreword
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This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 14, Space systems and operations.
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iv © ISO 2021 – All rights reserved

Introduction
This document was developed to support the implementation of the high-level space debris mitigation
requirements in ISO 24113.
This document contains a detailed and practical set of requirements and recommendations to assist
the space industry in conforming to the requirements in ISO 24113 which relate to launch vehicle
orbital stages.
INTERNATIONAL STANDARD ISO 20893:2021(E)
Space systems — Detailed space debris mitigation
requirements for launch vehicle orbital stages
1 Scope
This document defines detailed space debris mitigation requirements and recommendations for the
design and operation of launch vehicle orbital stages in Earth orbit.
The requirements defined in this document are applicable for:
— avoiding the release of space debris;
— disposing of a launch vehicle orbital stage after the end of its mission so as to avoid a break-up in orbit;
— disposing of a launch vehicle orbital stage after the end of its mission so as to minimize interference
with the protected regions;
— safely re-entering a launch vehicle orbital stage.
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 24113, Space systems — Space debris mitigation requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 24113 and the following apply.
ISO and IEC maintain terminological 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
decay orbit
orbit that will result in the re-entry of a launch vehicle orbital stage
3.2
disposal orbit
orbit in which launch vehicle orbital stage resides following the completion of its disposal maneuvers
4 Avoiding the intentional release of space debris into Earth orbit during normal
operations
4.1 ISO 24113 specifies a limit for the total number of launch vehicle orbital stages and space debris
objects that a launch vehicle may leave in Earth orbit during normal operations.
NOTE The space debris objects related to the launch include, but are not limited to, protective shrouds, inter-
stage elements, clamp bands, jettisonable tanks, jettisonable attitude control or propellant settling systems.
4.2 If a launch vehicle, by design, leaves two launch vehicle orbital stages in Earth orbit during the
launch of a single spacecraft, then at least one of the two stages shall be removed. It is preferred for both
stages to be removed from orbit at the end of the launch vehicle’s operations.
5 Avoiding break-ups in Earth orbit
5.1 Accidental break-up caused by an on-board source of energy
5.1.1 General
The following elements of a launch vehicle orbital stage are most likely to cause an accidental break-up:
a) residual propellants in propulsion systems;
b) pressure gasses in vessels including propellant tanks, high-pressure gas bottles, and pressure lines;
c) batteries;
d) range safety system when not decoupled from command chain, i.e. computer order and
necessary energy.
5.1.2 Residual propellants in propulsion systems
5.1.2.1 Residual propellants shall be vented from a launch vehicle orbital stage as part of its passivation,
the timing of such an operation being selected in order not to generate any adverse consequence to the
stage or its payloads.
NOTE1 In case residual propellants are vented by combustion from the thrust chamber, the change of mixture
ratio inside the chamber is a major factor of break-up risk of the thrust chamber.
NOTE2 In case residual propellants are vented in a sequential mode, without combustion, the pressure
gradients of venting of liquid residual propellants are key control variables to avoid either boiling up or the
generation of ice particle(debris) which can clog the passivation orifices and valves.
5.1.2.2 The venting of residual propellants shall be implemented in accordance with the requirements
of launch vehicle orbital stage disposal.
NOTE Proper orientation of venting outlets can lower the final orbit and thus reduce the orbit lifetime of a
launch vehicle orbital stage.
5.1.3 Pressurized gasses in pressure vessels
Pressure vessels shall be designed in accordance with standardised procedures, and made safe by one
or more of the following means (in order of preference):
a) relieving the pressurized gasses totally, or
b) relieving the pressurized gasses until the internal pressures are lower than their validated critical
values, or
c) designing with safety margins that do not allow rupture when considering thermal effec
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