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comparable safety critical systems, sub-systems, and components, and by conducting both analyses and
tests, at the respective levels. A flight history could mean extensive documentation might not be required
if it can be shown through test results, analyses, or empirical data, that the flight regimes experienced are
similar to the proposed flight regime. The degree of applicability of data depends on the degree of
similarity to environmental conditions and how environmental conditions compare to the history and
anticipated reactions of this system. Even when the same system, sub-system, or component is known to
have an extensive (and favorable) flight history in the same or more severe environments, interfaces and
integration with other systems must still be examined and tested. Another method of acquiring data is
through estimating system, sub-system, and component 3-sigma performance and reliability numbers
from testing evaluations and (where applicable) flight data.
The use of similarity is not new to launch operations. EWR 127-1, Paragraph. 4.14.1.2, states: as
required, qualification by similarity analysis shall be performed; if qualification by similarity is not
approved, then qualification testing shall be performed. For example, if component A is to be considered
as a candidate for qualification by similarity to a component B that has already been qualified for use,
component A shall have to be a minor variation of component B. Dissimilarities shall require
understanding and evaluation in terms of weight, mechanical configuration, thermal effects, and dynamic
response. Also, the environments encountered by component B during its qualification or flight history
shall have to be equal to or more severe than the qualification environments intended for component A.
13.4.7 Operational Controls
There is an interrelationship between the system design capabilities and the systems operational
limitations. Figure 2 depicts the relationship between the vehicle systems and the scope of operations
within which the vehicle is operated. What constitutes a safety critical system may depend on the scope
and nature of the vehicle design and its proposed operations. Intended operational requirements affect the
proposed vehicle design requirements and vehicle capabilities/limitations and also establish the
operational system constraints necessary to protect public health and safety. For example, reusable launch
vehicle landing sites may have to be within some minimum cross-range distance from the orbital ground
trace because of cross-range limitations of the vehicle. A vehicle operator may choose, or be required, to
mitigate certain vehicle limitations through the use of operational controls rather than relieving vehicle
limitations through design changes.
Test parameters and analytic assumptions will further define the limits of flight operations. The scope of
the analyses and environmental tests, for example, will constitute the dimensions of the applicant’s
demonstration process and therefore define the limits of approved operations if a license is issued. Such
testing limits, identified system and subsystem limits, and analyses also are expected to be reflected in
FAA System Safety Handbook, Chapter 13: Launch Safety
December 30, 2000
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mission monitoring and mission rules addressing such aspects as commit to launch, flight abort, and
commit to reentry.
Vehicle capabilities/limitations and operational factors such as launch location and flight path each affect
public risk. The completion of system operation demonstrations, such as flight simulations and controlled
flight tests, provide additional confidence in the vehicle systems and performance capabilities. As
confidence in the systems overall operational safety performance increases, key operational constraints
such as restrictions on overflight of populated areas may be relaxed.
The following are examples of the types of operations-related considerations that may need to be
addressed by the applicant when establishing their operations scenarios.
Launch commit criteria/rules
Human override capability to initiate safe abort during launch and reentry
System monitoring, inspection and checkout procedures
For re-flight: inspection and maintenance
Selected primary and alternate landing sites for each stage
Surveillance/control of landing areas
Standard limits on weather
Coordination with appropriate air space authorities
Limits on flight regime (ties in with analysis, testing and demonstrating confidence in
system performance and reliability)
Limits on over-fight of populated areas
Others identified through hazard analysis
FAA System Safety Handbook, Chapter 13: Launch Safety
　
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