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112 MEMS and Microstructures in Aerospace Applications

TABLE 6.1
Technology Readiness Level (TRL) Scale

TRL1 Basic principles observed and reported
TRL2 Technology concept and application formulated
TRL3 Analytical and experimental critical function and/or characteristic proof-of-concept
TRL4 Component and/or breadboard validation in laboratory environment
TRL5 Component and/or breadboard validation in relevant environment
TRL6 System or subsystem model or prototype demonstration in a relevant
environment (ground or space)
TRL7 System prototype demonstration in a space environment
TRL8 Actual system completed and ‘‘flight qualified’’ through test and
demonstration (ground or flight)
TRL9 Actual system ‘‘flight proven’’ through successful mission operations
Source: NASA/JPL.

concepts are at the low TRL stage, sometimes referred to as the ‘‘technology push’’
4
stage, with the daunting challenge of having to bridge the ‘‘TRL gap’’ to success-
fully transition to the high-TRL space applications or ‘‘technology pull’’ stage. The
TRL gap, sometimes referred to as the ‘‘valley of death’’ in the commercial sector,
therefore represents an order-of-magnitude increase in effort (and consequently
funding) that is required to make the transition to high TRL. The primary reason
that most new technologies fail to bridge the TRL gap is that because of their
relatively low maturity, they do not have a compelling mission ‘‘pull’’ to drive
further system-level development.
Another important consideration is that space applications only need compon-
ents and systems in relatively minuscule volumes compared to the consumer
market. However, the performance requirements for these technologies are no less
stringent, and in most cases, much more so than for consumer products. Thus, the
system development costs are considerable since a sufficiently large body of
laboratory test data has to be generated in order to conclusively demonstrate the
reliability of the new technology. Additionally, there is also a more subtle percep-
tion barrier to be overcome. This involves the generation of sufficient ‘‘space
heritage’’ via actual space flights of the new system. Carried to the extreme, this
perception barrier leads to the conundrum that a new technology cannot fly unless it
has flown before! NASA has recognized the impact of the space heritage barrier as
a major obstacle impeding the infusion of new technologies into its missions. This
recognition has led to the setting up of programs such as the New Millennium
Program (NMP) that are aimed specifically to provide flight demonstration oppor-
tunities for new technologies. These flights, however, are few and far between, and
are also generally restricted to technologies that are already at a high level of
maturity (TRL 4 and above).

© 2006 by Taylor & Francis Group, LLC