ASTM F3668/F3668M-23

• Abstract:

  SIGNIFICANCE AND USE; 4.1 Flight crew safety is a complex and all-encompassing goal of human spaceflight. The entire spacecraft is designed to get the flight crew safely to and from their Low Earth Orbit (LEO) destination. In the spirit of Specification F3479, Failure Tolerance for Occupant Safety of Suborbital Vehicles, failure tolerance, or an equivalent means of control where failure tolerance is impractical, is the primary control for prevention of catastrophic hazards that cannot be eliminated from the design. This is true for all hazards which may result in a catastrophic event. The spacecraft can be also be designed with increased levels of failure tolerance to enhance the likelihood of mission success. ; 4.2 This guide is focused upon the design and operational capabilities necessary to support flight crew survivability when failure tolerance has been exhausted. For example, a spacecraft may have three mission computers that perform identical functions. Typical rules that govern the flight operations might allow continuation of the mission after the first failure. Following the second failure, a mission abort is likely using the single remaining mission computer to return the spacecraft to safety. Should this third computer fail, emergency systems are available to assist the return of the flight crew to safety when possible, and it is those systems that are the focus of this guide. Note that for each emergency situation described herein, a set of emergency procedures and the equipment to implement them will be available in order for the crew to survive. ; 4.3 LEO missions are divided into pre-launch, ascent, orbit, reentry, and landing. Note that there are separate, additional considerations for transport of humans beyond LEO and for missions having crewed durations in LEO of greater than approximately 30 days which are not within the scope of this guide.; SCOPE; 1.1 The purpose of this guide is to provide guidance for current and developing space flight operators who intend to fly humans on spacecraft. The occupants include the crew and spaceflight participants in the orbital vehicles. This guide is targeted primarily toward ground launched, Low Earth Orbit (LEO) spacecraft which provide transportation from the surface to orbit followed by subsequent rendezvous with an orbital complex or short-duration free flight orbit operations, and safe return to Earth’s surface. As used in the guide, LEO is an approximate circular orbit within ~2000 km of Earth’s surface. Longer duration spaceflight (>approximately two weeks) aboard an orbital space station poses unique design and medical constraints which are not specifically addressed in this guide. ; 1.2 The methods in this guide are best practices. Having prior positive performing systems may be a basis for compliance to this guide. ; 1.2.1 This is a non-comprehensive subset of best safety practices for crew survivability of catastrophic hazards for which all failure tolerance has been exhausted. This is further elaborated upon in 1.5 and 4.2. ; 1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard. ; 1.4 Each spacecraft will present its own set of safety hazards that the user of this standard is expected to analyze and implement survivability options where practical. Also, note that safety is an inherent characteristic of a system, not the product of a few key post-hazard mitigation features. History has shown that a safe and successful spaceflight system is built and operated to the highest possible standards of design robustness, manufacturing quality, inspection, test, and operation, including maintenance and sustaining engineering. The addition of the design features and capabilities as re...

• Status: Published
• Publication Date: 30-Sep-2023
• Technical Committee: F47 - Commercial Spaceflight
• Drafting Committee: F47.01 - Occupant Safety

• Referred By: ASTM F3658-23 - Standard Guide for Crewed Suborbital Space Vehicle Design
• Effective Date: 01-Oct-2023

Overview

ASTM F3668/F3668M-23 - Standard Guide for Occupant Survivability in Orbital Vehicles provides comprehensive guidance for promoting the safety and survivability of occupants-both crew and spaceflight participants-onboard Low Earth Orbit (LEO) spacecraft. Developed by ASTM, this guide targets current and emerging space flight operators responsible for transporting humans from Earth’s surface to orbit, conducting orbital operations, and ensuring safe return.

The primary intent is to identify best practices that enhance occupant survivability, especially when conventional failure tolerance has been exhausted. The standard addresses the design, systems, and operational procedures that support crew safety throughout critical mission phases, including pre-launch, ascent, orbit, reentry, and landing. By focusing on catastrophic hazards and emergency response solutions, the guide supports robust risk mitigation and continuous improvement of orbital vehicle safety.

Keywords: occupant survivability, orbital vehicles, crew safety, LEO spacecraft, emergency systems, failure tolerance, spaceflight safety.

Key Topics

• Survivability Beyond Failure Tolerance:
  The guide emphasizes that failure tolerance or equivalent control measures are the primary lines of defense against catastrophic hazards in spacecraft. When these are no longer viable, it is crucial to have contingency systems and procedures in place to maximize the chances of occupant survival.

• Emergency Response Systems:
  Recommendations cover the availability of emergency procedures and systems-such as abort and escape capabilities, personal protective equipment, fire suppression, emergency egress, and atmospheric management-that support crew response to critical situations.

• Applicable Phases of Human Spaceflight:
  The standard considers the entire mission lifecycle-pre-launch, ascent, orbit, re-entry, and landing-recognizing that different hazards and survivability requirements exist at each phase.

• Hazard Analysis and Best Practices:
  Users of the standard are expected to thoroughly analyze spacecraft-specific risks and implement practical controls and design features that enhance overall survivability, building on the lessons learned from previous successful missions.

• Compliance and Units of Measure:
  Guidance is based on best practices, with flexibility for using proven legacy systems. It permits the use of SI or inch-pound units, but not a mix, to avoid nonconformance.

Applications

• Spacecraft Design and Operations:
  This guide informs the design process for new orbital vehicles and operational protocols for crewed missions, ensuring that safety systems are integrated into both hardware and procedures from initial concept through mission execution.

• Mission Planning and Risk Mitigation:
  By highlighting critical mission phases and detailing emergency response expectations, operators can plan missions with enhanced contingency readiness, thus improving the likelihood of safe crew return even under adverse scenarios.

• Safety Analysis for Regulatory Approval:
  By following this standard, companies and agencies demonstrate adherence to recognized safety benchmarks, which may assist in meeting regulatory safety requirements and industry certification.

• Training and Crew Preparedness:
  The standard supports the development of emergency training programs, ensuring that crew and spaceflight participants are prepared to execute necessary survival actions should primary systems fail.

Related Standards

• ASTM F3479: Specification for Failure Tolerance for Occupant Safety of Suborbital Vehicles, which shares similar principles around failure tolerance and occupant safety.
• NASA Standard CCT-REQ-1130: Addresses flight crew transportation and services for the International Space Station, providing additional requirements for human spaceflight safety.
• NASA-STD-6016C: Outlines standard material and process requirements for spacecraft.
• Federal Regulations (CFR Title 14, Chapter III, Subchapter A, PART 401 and CFR Title 49, Chapter VIII, PART 830): Establish definitions and requirements relevant to commercial spaceflight operations.

ASTM F3668/F3668M-23 serves as an essential resource for any organization involved in crewed orbital spaceflight, guiding the implementation of robust occupant survivability practices for greater overall spaceflight safety.

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3668/F3668M − 23
Standard Guide for
Occupant Survivability in Orbital Vehicles
This standard is issued under the fixed designation F3668/F3668M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope The addition of the design features and capabilities as recom-
mended in this guide cannot and is not intended to make up for
1.1 The purpose of this guide is to provide guidance for
deficiencies in these basics. It is the responsibility of the user
current and developing space flight operators who intend to fly
of this standard to establish appropriate safety, survivability,
humans on spacecraft. The occupants include the crew and
health, and environmental practices and determine the appli-
spaceflight participants in the orbital vehicles. This guide is
cability of regulatory limitations prior to use. For example,
targeted primarily toward ground launched, Low Earth Orbit
with regard to survivability, certain operators will likely
(LEO) spacecraft which provide transportation from the sur-
require additional crew survivability capabilities be provided
face to orbit followed by subsequent rendezvous with an orbital
prior to permitting their space vehicle to fly a crew.
complex or short-duration free flight orbit operations, and safe
1.5 This standard does not purport to address all of the
return to Earth’s surface. As used in the guide, LEO is an
safety or survivability design concerns, if any, associated with
approximate circular orbit within ~2000 km of Earth’s surface.
its use. It is the responsibility of the user of this standard to
Longer duration spaceflight (>approximately two weeks)
establish appropriate safety, survivability, health, and environ-
aboard an orbital space station poses unique design and
mental practices and determine the applicability of regulatory
medical constraints which are not specifically addressed in this
limitations prior to use.
guide.
1.6 This international standard was developed in accor-
1.2 The methods in this guide are best practices. Having
dance with internationally recognized principles on standard-
prior positive performing systems may be a basis for compli-
ization established in the Decision on Principles for the
ance to this guide.
Development of International Standards, Guides and Recom-
1.2.1 This is a non-comprehensive subset of best safety
mendations issued by the World Trade Organization Technical
practices for crew survivability of catastrophic hazards for
Barriers to Trade (TBT) Committee.
which all failure tolerance has been exhausted. This is further
elaborated upon in 1.5 and 4.2.
2. Referenced Documents
1.3 Units—The values stated in either SI units or inch-
2.1 ASTM Standards:
pound units are to be regarded separately as standard. The
F3479 Specification for Failure Tolerance for Occupant
values stated in each system may not be exact equivalents;
Safety of Suborbital Vehicles
therefore, each system shall be used independently of the other.
2.2 NASA Standards:
Combining values from the two systems may result in noncon-
NASA Standard CCT-REQ-1130 ISS Flight Crew Transpor-
formance with the standard.
tation and Services
1.4 Each spacecraft will present its own set of safety
NASA Technical Standard NASA-STD-6016C; Standard
hazards that the user of this standard is expected to analyze and
Material and Processes Requirements for Spacecraft
implement survivability options where practical. Also, note
2.3 Federal Regulations:
that safety is an inherent characteristic of a system, not the
CFR Title 14, Chapter III, Subchapter A, PART 401 (Defi-
product of a few key post-hazard mitigation features. History
nitions)
has shown that a safe and successful spaceflight system is built
CFR Title 49, Chapter VIII, PART 830 (Definitions)
and operated to the highest possible standards of design
robustness, manufacturing quality, inspection, test, and
operation, including maintenance and sustaining engineering.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This guide is under the jurisdiction of ASTM Committee F47 on Commercial the ASTM website.
Spaceflight and is the direct responsibility of Subcommittee F47.01 on Occupant Available from the National Aeronautics and Space Administration (NASA),
Safety. https://ntrs.nasa.gov/citations/20150010757.
Current edition approved Oct. 1, 2023. Published October 2023. DOI: 10.1520/ Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St.,
F3668_F3668M-23. NW, Washington, DC 20401, http://www.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3668/F3668M − 23
3. Terminology 3.1.8.1 Discussion—During the launch countdown, flight
crew may continue by taking an elevator, slide wire, or a
3.1 Definitions:
similar system to a safe distance or place (shelter) outside a
3.1.1 abort, v—the forced early return of the crew when
defined hazard area. However, they may also stop at a safe
failures or the existence of uncontrolled catastrophic hazards
shelter still inside a hazard area that provides adequate protec-
prevent continuation of the mission profile and a return is
tion until the hazard is cleared.
required for crew survival; escape is a specific instance of an
3.1.9 emergency equipment and systems, n—systems
abort and is defined below.
(ground or flight) that exist solely to prevent loss of life in the
3.1.2 automated, automatic, adj—ability of a space system
presence of imminent catastrophic conditions; examples in-
to perform operations independent of ground control team or
clude fire suppression systems and extinguishers, emergency
flight crewmembers as opposed to human control of a system
breathing devices, Personal Protective Equipment (PPE), emer-
or operation.
gency communication and crew escape systems; emergency
3.1.3 autonomous, adj—ability of a space system to perform
systems are not considered a leg of failure tolerance for the
operations independent from any ground-based systems or
nominal, operational equipment and systems, and do not serve
other external command and control center; this includes no
as a design control to prevent the occurrence of a catastrophic
communication with or real-time support from mission control,
condition.
other ground systems, or other spacecraft.
3.1.10 escape, n—separation of the crewed spacecraft from
3.1.3.1 Discussion—This definition excludes any devices or its launch vehicle/booster in an off-nominal scenario to avoid a
systems which contribute to the cooperative rendezvous with
hazardous condition during ascent to orbit.
and docking to participating spacecraft such as transponders,
3.1.10.1 Discussion—There are several different escape sce-
broadcast of ancillary data such as state vector from a target
narios depending on the phase of ascent (all the way from pad
spacecraft, or radar reflectors on the target spacecraft which
escape through the ascent to orbit). The final possible phase of
contribute to the accuracy of the relative state vector between
escape is an escape to orbit; in this case, the spacecraft
the chaser and the target.
continues to temporary, sub-optimal orbit rather than immedi-
3.1.4 catastrophic failure, n—an event resulting in death or
ately returning to the ground.
permanent disability to flight crew and/or public, or complete
3.1.11 failure tolerance, n—the ability to sustain a certain
safety-critical system loss; for the purposes of this guide, this
number of failures while still retaining the capability to satisfy
is further defined as a failure which either causes the loss of the
safety objectives.
spacecraft or the loss of the launch vehicle.
3.1.12 flight crew survivability, n—the capability of the
3.1.5 crew or flight crew, n—any employee or independent
contractor of an operator who performs activities directly flight crew to avoid or withstand a hostile environment caused
by a catastrophic condition without sustaining death, or the
relating to the launch, reentry, or other operation of or in a
impairment of their ability to accomplish their designated
launch vehicle or reentry vehicle that carries human beings; a
crew consists of flight crew and any remote operator; as this mission.
guide is focused on safety of all those onboard, spaceflight
3.1.12.1 Discussion—This includes the ability to keep the
participants are considered crew or flight crew.
flight crew alive using such capabilities as abort, escape, safe
3.1.6 critical failure, n—an event causing serious injury (as
haven, emergency egress, rescue and emergency medical
defined in 49 CFR § 830.2; Definitions) or illness to the flight
equipment.
crew or public, or major system failure which can result in the
3.1.13 hazard, n—any real or potential condition that can
early termination of a mission; for the purpose of this guide,
cause a serious or fatal injury.
this is further defined as a failure of spacecraft system(s) which
3.1.14 hazard analysis, n—identifies hazards within the
can compromise the ability of the vehicle to achieve the
integrated system and the means to control or eliminate them.
mission.
3.1.7 Downrange Abort Exclusion Zone (DAEZ), n—The
3.1.15 human rating, n—the process of evaluating and
Downrange Abort Exclusion Zone (DAEZ) is specific to assuring that the total system can safely conduct the required
ground-up rendezvous to the International Space Station (ISS)
human missions.
from Kennedy Space Center (orbit inclined at 51.6 deg); it is a
3.1.16 MMOD, n—Micrometeoroid and Orbital Debris;
region in the North Atlantic that extends roughly 150 nm east
naturally occurring micrometeoroids and man-made debris
of St. John’s Newfoundland to 150 nm west of Shannon,
orbiting the Earth within the bounds of LEO.
Ireland; the intent of any exclusion zone is to avoid possible
3.1.17 operator, n—a holder of a license or permit under 51
ascent escapes into known hazards such as rough seas and
U.S.C. Subtitle V, Chapter 509: Commercial Space Launch
cold-water temperatures in the North Atlantic.
Activities.
3.1.8 emergency egress, n—capability for a crew to exit the
vehicle and leave a hazardous situation or catastrophic event 3.1.18 remote operator, n—a crew member who (1) has the
within the specified time; flight crew emergency egress can be ability to control, in real time, a launch, orbit or reentry
unassisted or assisted by ground personnel including first vehicle’s flight path, and (2) is not on board the controlled
responders. vehicle, for example, a Ground Control Team.
F3668/F3668M − 23
3.1.19 spacecraft, n—all system elements that are occupied be afforded the ability to reach the safe area within the time it
by the crew during the space mission and provide life support takes failures to reach criticality as defined by a hazard
functions for the crew. The crewed element includes all the analysis. Where egress is a necessary part of mitigating
subsystems that provide life support functions for the crew. hazards, features of a system that provides this egress capabil-
ity include:
3.1.20 spaceflight participant, n—any human on board the
5.1.1 Vehicle mechanical systems that permit the flight crew
spacecraft while in flight that has no responsibility to perform
to self-egress the spacecraft in approximately 90 seconds.
nominal mission tasks but who is trained to deploy and operate
5.1.1.1 Self-egress systems include the ability to self-extract
specific emergency systems.
quickly from the vehicle seating (for example, a single-point
3.1.21 time to criticality, n—the time it takes for failure
harness) and mobility aids to help the flight crew reach the exit
effects to propagate from the failure mode to the critical failure
hatch, equalize pressure across the exit hatch, open the hatch to
effect (for example, loss of vehicle, loss of control).
the primary egress route without requiring specialized tools,
and safe access to an exit platform without using fall protec-
4. Significance and Use
tion. Inward opening, pressure-sealed hatches have been im-
4.1 Flight crew safety is a complex and all-encompassing
plicated in delayed rescues (Apollo 1) therefore the risk of
goal of human spaceflight. The entire spacecraft is designed to
post-liftoff cabin leakage and rapid decompression should be
get the flight crew safely to and from their Low Earth Orbit
weighed against the risk of delayed hatch opening during the
(LEO) destination. In the spirit of Specification F3479, Failure
pre-launch phase when designing the proper egress method.
Tolerance for Occupant Safety of Suborbital Vehicles, failure
5.1.2 Personal Breathing Apparatus (PBA) systems that
tolerance, or an equivalent means of control where failure
support the egress.
tolerance is impractical, is the primary control for prevention
5.1.2.1 Conditions which warrant an emergency egress are
of catastrophic hazards that cannot be eliminated from the
varied, but can include leakage of propellants or other liquids
design. This is true for all hazards which may result in a
which are toxic. PBAs should be available for donning if
catastrophic event. The spacecraft can be also be designed with
pressure suits are not available or the crew is unsuited prior to
increased levels of failure tolerance to enhance the likelihood
leaving the protective confines of the egress platform and
of mission success.
should protect the nose, mouth, and eyes.
5.1.3 A clearly marked egress pathway to provide guidance
4.2 This guide is focused upon the design and operational
to flight crew.
capabilities necessary to support flight crew survivability when
5.1.3.1 The egress route can be encumbered by smoke, toxic
failure tolerance has been exhausted. For example, a spacecraft
gasses, poor lighting, fire deluge systems, and limited commu-
may have three mission computers that perform identical
nication with rescue forces or each other. A clearly marked path
functions. Typical rules that govern the flight operations might
will avoid disorientation and expedite the egress.
allow continuation of the mission after the first failure. Fol-
5.1.4 Expeditious movement to a safe area during egress.
lowing the second failure, a mission abort is likely using the
5.1.4.1 Booster/spacecraft design should include passively
single remaining mission computer to return the spacecraft to
safe systems that can prolong the time between a failure and a
safety. Should this third computer fail, emergency systems are
catastrophic event. Only through a hazard analysis can the time
available to assist the return of the flight crew to safety when
to criticality be determined. This time to criticality will
possible, and it is those systems that are the focus of this guide.
determine how quickly the flight crew should move from the
Note that for each emergency situation described herein, a set
spacecraft to the safe area. In some cases, stairs or an elevator
of emergency procedures and the equipment to implement
may be acceptable. In others, a more expeditious system such
them will be available in order for the crew to survive.
as a slide wire, zipline, slide, or blast-proof conveyance will be
4.3 LEO missions are divided into pre-launch, ascent, orbit,
necessary. Where the time to criticality is less than that needed
reentry, and landing. Note that there are separate, additional
for flight crew egress, additional hazard controls, mitigations,
considerations for transport of humans beyond LEO and for
and/or protective measures should be added (for example,
missions having crewed durations in LEO of greater than
enhanced factor/margin of safety).
approximately 30 days which are not within the scope of this
5.1.5 A safe area outside the hazard/blast danger area
guide.
reachable by protected transportation at which the flight crew
are met with rescue and medical assistance.
5. Applicable Phases of Flight
5.1.5.1 Flight crew may initially stay in a safe area (that is,
5.1 Pre-launch—The pre-launch phase includes the time
a protected shelter) inside the hazard area until the hazard
from flight crew ingress into the spacecraft up to the launch.
condition is cleared, and then they can move to a safe area
During this phase, dynamic operations should normally be
outside the hazard to receive assistance. If, during the egress,
avoided (fueling, significant tank pressure changes, arming,
the crew could be exposed to a hazard, the transportation
venting, and so forth) so as to minimize risk to the flight crew.
method should be protected against the hazard.
Given that this is not always possible, the flight crew should be
provided a means to egress from a spacecraft to a safe area
where they can be protected from hazards. The flight crew may
Reference for 90 seconds here: https://www.faa.gov/documentLibrary/media/
self-egress or be assisted by a ground team. In either case, the
Advisory_Circular/AC_25.803-1A.pdf. 90 seconds is also referenced in NASA-
flight crew and any ground team involved in the egress should STD-1130.
F3668/F3668M − 23
5.2 Ascent: achieve safe orbital velocity, or major spacecraft subsystem
5.2.1 Historically, the most significant failures that alter the failure (that is, fire, loss of cabin pressure, etc.).
outcome of the mission occur during the dynamic phases of 5.2.5.1 Pre-lift-off. A pre-launch escape (also known as “pad
ascent to and re-entry from LEO. High-temperature/high- escape” or “pad abort”) adds complexity to a spacecraft escape
frequency machinery, rapidly changing environmental factors, due to the low altitude, speed and proximity of ground
exposure to aerodynamic forces, pyrotechnic shock, vibration, equipment and launch structure. Additionally, a pre-launch
and maneuvering all combine to test the booster and spacecraft. escape may exacerbate the ground system or booster failure
A powered escape system (such as an ejection seat, tractor/ initiating event for the escape (that is, compressed gas or
pusher escape system, or other systems to extricate the flight propellant leak) and may cause a conflagration when one
crew from a rapidly degrading situation) uses rapid accelera- would not have otherwise occurred. Notwithstanding, if there
tion of a segment of the spacecraft away from the main element are no other credible options for flight crew survival, a
to take the flight crew to safety. These systems are inherently pre-launch escape capability is highly desirable (Reference
risky themselves and add mass and complexity, but historically, Soyuz T-10-1 pad-escape (1983) ).
they have been considered better than the alternative of losing 5.2.5.2 Post-MECO through orbital insertion. For the pur-
the flight crew. An element of the “escape approach” is an poses of this discussion, orbital insertion is defined as a stable
expeditious (but not immediate) return to safety. This could be orbit for at least 24 hours. A post-powered ascent escape
an ability to land in a safe area after a single orbit or the ability capability provides options to a remote operator (that is,
to dock to a safe haven within hours of launch. Generally, the ground control team) and the flight crew. In the event an early
flight crew should be protected from catastrophic failures main engine cutoff (MECO) results in insufficient orbital
during the powered launch phase as follows: velocity, an automated capability to establish a safe orbital
5.2.2 Detect and automatically initiate an ascent escape velocity and trajectory may avoid an early re-entry and provide
when immediate action is the only means of flight crew additional time for the flight crew or ground control team to
survival for a known failure mode from pre-launch through consider options. Establishing a safe spacecraft configuration
booster separation. for re-entry to an emergency landing site after one orbit is
5.2.2.1 The primary emphasis here is on launch vehicle likely the best option in the presence of an early MECO or if
failures where an immediate safe separation and return of the the spacecraft has experienced a critical systems failure which
spacecraft will provide a chance for flight crew survival. warrants a return as soon as possible (cabin leak, fire, etc.).
However, spacecraft systems should also be assessed to deter-
5.3 Orbital Flight:
mine if any failure modes warrant the immediate response of
5.3.1 Categories of orbital flight (post-orbital insertion
an automated escape system. Note, there should also be a
through de-orbit burn) emergency systems are organized under
capability for manually (both flight and ground control team)
fire, toxic atmosphere, loss of pressure (Dp/Dt), and loss of
initiated escape for failure modes when an immediate response
control (LOC). Failure of systems (for example, electrical
of an automated escape does not exist. When assessing the
power system, batteries (for example, thermal runaway), and
effectiveness of a spacecraft escape systems during ascent, the
other energetic systems) or controls for certain hazards can
possibility of launch vehicle Flight Termination System initia-
lead to fires or cause a toxic atmosphere. Structural failures or
tion should be considered, particularly given the recent trend
micrometeoroid and orbital debris (MMOD) can lead to
towards automated activation of these systems.
structural breach and loss of pressure (Dp/Dt). Systems failures
5.2.3 Provide an ascent escape capability that results in the
under the broad category of guidance, navigation, and control
spacecraft landing outside hazardous areas as defined in the
(GNC) can lead to a LOC. In addition to these emergency
hazard analysis (for example, the Downrange Abort Exclusion
systems, safety systems should be considered for orbital
Zone (DAEZ) for ground-up ISS rendezvous missions
vehicles that are performing proximity or docking operations
launched from Kennedy Space Center).
(prox ops) with other vehicles. In the event of failures during
5.2.4 Provide the ability for the flight crew to survive for at
prox ops resulting in a loss of control, the spacecraft should
least 24 hours under ocean (or land) landing conditions
provide for a flight crew or remote operator to command the
(temperature, wave height, etc.) while awaiting rescue.
vehicle to hold and break-out of the planned trajectory within
5.2.4.1 Hazardous escape landing conditions should be
the time to criticality after the failure has occurred to avoid a
avoided. While this is not always possible due to the expanse
hazardous condition (for example, collision).
of possible geography following a spacecraft escape, the
5.3.2 Atmospheric Safety—Fire:
spacecraft should provide adequate inherent survival charac-
5.3.2.1 An on-orbit fire can quickly put the flight crew into
teristic given the worst expected landing conditions.
extremis. The absence of ventilation, the permeation of com-
Additionally, landing within close proximity to land masses
bustion products in a zero-g environment, and the limited
with pre-positioned recovery teams maximizes the probability
source of emergency breathing air to supplement the environ-
of flight crew survival. Twenty-four hours is the approximate
ment until the toxic gasses can be purged combine to make a
time for pre-positioned rescue forces to arrive at an ocean
zero-g fire uniquely dangerous. To provide the maximum
landing area.
5.2.5 Provide continuous ascent escape capability from
pre-lift-off through orbital insertion in the event of a failure to https://en.wikipedia.org/wiki/Soyuz_7K-ST_No.16L.
F3668/F3668M − 23
chance of flight crew survival following a fire the spacecraft an equivalent can be time consuming. But unless the capacity
should, at a minimum, provide the following fire mitigations: or desire is to deorbit immediately, the cabin atmosphere will
require remediation.
5.3.3 Fire detection system that senses combustion products
5.3.8 Before doffing PBA, a means to ensure the post-fire
from the primary environmental control system flow path.
toxicity of the atmosphere is acceptable.
5.3.3.1 The nature of gas propagation in zero-g warrants a
5.3.8.1 A method to test the atmosphere is essential before
continuous flow of mixed ambient gases past combustion
doffing the PBA. Depending upon the anticipated
sensors. Areas of stagnant airflow should be avoided.
contaminants, a compound-specific analyzer (CSA) or Drager
5.3.4 Means to suppress credible fire types given the known
tube system can be used. Criteria for an acceptable atmosphere
fuel and combustion sources.
should be established in
...