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TECHNOLOGY READINESS LEVELS
A White Paper
April 6, 1995
Edited: 22 December 2004
John C. Mankins
Advanced Concepts Office
Office of Space Access and Technology
NASA
Introduction
Technology Readiness Levels (TRLs) are a systematic metric/measurement system that
supports assessments of the maturity of a particular technology and the consistent
comparison of maturity between different types of technology. The TRL approach has
been used on-and-off in NASA space technology planning for many years and was
recently incorporated in the NASA Management Instruction (NMI 7100) addressing
integrated technology planning at NASA. Figure 1 (attached) provides a summary view
of the technology maturation process model for NASA space activities for which the
TRL’s were originally conceived; other process models may be used. However, to be
most useful the general model must include: (a) ‘basic’ research in new technologies
and concepts (targeting identified goals, but not necessary specific systems), (b)
focused technology development addressing specific technologies for one or more
potential identified applications, (c) technology development and demonstration for each
specific application before the beginning of full system development of that application,
(d) system development (through first unit fabrication), and (e) system ‘launch’ and
operations.
Technology Readiness Levels Summary
TRL 1 Basic principles observed and reported
TRL 2 Technology concept and/or application formulated
TRL 3 Analytical and experimental critical function and/or characteristic proof-
of-concept
TRL 4 Component and/or breadboard validation in laboratory environment
TRL 5 Component and/or breadboard validation in relevant environment
TRL 6 System/subsystem model or prototype demonstration in a relevant
environment (ground or space)
TRL 7 System prototype demonstration in a space environment
TRL 8 Actual system completed and “flight qualified” through test and
demonstration (ground or space)
TRL 9 Actual system “flight proven” through successful mission operations
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Discussion of Each Level
The following paragraphs provide a descriptive discussion of each technology readiness
level, including an example of the type of activities that would characterize each TRL.
TRL 1
Basic principles observed and reported
This is the lowest “level” of technology maturation. At this level, scientific research
begins to be translated into applied research and development. Examples might include
studies of basic properties of materials (e.g., tensile strength as a function of
temperature for a new fiber).
Cost to Achieve: Very Low ‘Unique’ Cost
(investment cost is borne by scientific research programs)
TRL 2
Technology concept and/or application formulated
Once basic physical principles are observed, then at the next level of maturation,
practical applications of those characteristics can be ‘invented’ or identified. For
example, following the observation of high critical temperature (Htc) superconductivity,
potential applications of the new material for thin film devices (e.g., SIS mixers) and in
instrument systems (e.g., telescope sensors) can be defined. At this level, the
application is still speculative: there is not experimental proof or detailed analysis to
support the conjecture.
Cost to Achieve: Very Low ‘Unique’ Cost
(investment cost is borne by scientific research programs)
TRL 3
Analytical and experimental critical function and/or
characteristic proof-of-concept
At this step in the maturation process, active research and development (R&D) is
initiated. This must include both analytical studies to set the technology into an
appropriate context and laboratory-based studies to physically validate that the
analytical predictions are correct. These studies and experiments should constitute
“proof-of-concept” validation of the applications/concepts formulated at TRL 2. For
example, a concept for High Energy Density Matter (HEDM) propulsion might depend
on slush or super-cooled hydrogen as a propellant: TRL 3 might be attained when the
concept-enabling phase/temperature/pressure for the fluid was achieved in a laboratory.
Cost to Achieve: Low ‘Unique’ Cost
(technology specific)
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TRL 4
Component and/or breadboard validation in laboratory
environment
Following successful “proof-of-concept” work, basic technological elements must be
integrated to establish that the “pieces” will work together to achieve concept-enabling
levels of performance for a component and/or breadboard. This validation must devised
to support the concept that was formulated earlier, and should also be consistent with
the requirements of potential system applications. The validation is relatively “low-
fidelity” compared to the eventual system: it could be composed of ad hoc discrete
components in a laboratory. For example, a TRL 4 demonstration of a new ‘fuzzy logic’
approach to avionics might consist of testing the algorithms in a partially computer-
based, partially bench-top component (e.g., fiber optic gyros) demonstration in a
controls lab using simulated vehicle inputs.
Cost to Achieve: Low-to-moderate ‘Unique’ Cost
(investment will be technology specific, but probably
several factors greater than investment required for TRL 3)
TRL 5
Component and/or breadboard validation in relevant
environment
At this, the fidelity of the component and/or breadboard being tested has to increase
significantly. The basic technological elements must be integrated with reasonably
realistic supporting elements so that the total applications (component-level, sub-system
level, or system-level) can be tested in a ‘simulated’ or somewhat realistic environment.
From one-to-several new technologies might be involved in the demonstration. For
example, a new type of solar photovoltaic material promising higher efficiencies would
at this level be used in an actual fabricated solar array ‘blanket’ that would be integrated
with power supplies, supporting structure, etc., and tested in a thermal vacuum chamber
with solar simulation capability.
Cost to Achieve: Moderate ‘Unique’ Cost
(investment cost will be technology dependent, but likely to be several factors
greater that cost to achieve TRL 4)
TRL 6
System/subsystem model or prototype demonstration
in a relevant environment (ground or space)
A major step in the level of fidelity of the technology demonstration follows the
completion of TRL 5. At TRL 6, a representative model or prototype system or system
— which would go well beyond ad hoc, ‘patch-cord’ or discrete component level
breadboarding — would be tested in a relevant environment. At this level, if the only
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‘relevant environment’ is the environment of space, then the model/prototype must be
demonstrated in space. Of course, the demonstration should be successful to represent
a true TRL 6. Not all technologies will undergo a TRL 6 demonstration: at this point the
maturation step is driven more by assuring management confidence than by R&D
requirements. The demonstration might represent an actual system application, or it
might only be similar to the planned application, but using the same technologies. At
this level, several-to-many new technologies might be integrated into the demonstration.
For example, a innovative approach to high temperature/low mass radiators, involving
liquid droplets and composite materials, would be demonstrated to TRL 6 by actually
flying a working, sub-scale (but scaleable) model of the system on a Space Shuttle or
International Space Station ‘pallet’. In this example, the reason space is the ‘relevant’
environment is that microgravity plus vacuum plus thermal environment effects will
dictate the success/failure of the system — and the only way to validate the technology
is in space.
Cost to Achieve: Technology and demonstration specific; a fraction
of TRL 7 if on ground; nearly the same if space is required
TRL 7
System prototype demonstration in a space environment
TRL 7 is a significant step beyond TRL 6, requiring an actual system prototype
demonstration in a space environment. It has not always been implemented in the past.
In this case, the prototype should be near or at the scale of the planned operational
system and the demonstration must take place in space. The driving purposes for
achieving this level of maturity are to assure system engineering and development
management confidence (more than for purposes of technology R&D). Therefore, the
demonstration must be of a prototype of that application. Not all technologies in all
systems will go to this level. TRL 7 would normally only be performed in cases where
the technology and/or subsystem application is mission critical and relatively high risk.
Example: the Mars Pathfinder Rover is a TRL 7 technology demonstration for future
Mars micro-rovers based on that system design. Example: X-vehicles are TRL 7, as
are the demonstration projects planned in the New Millennium spacecraft program.
Cost to Achieve: Technology and demonstration specific,
but a significant fraction of the cost of TRL 8
(investment = “Phase C/D to TFU” for demonstration system)
TRL 8
Actual system completed and “flight qualified” through test and
demonstration (ground or space)
By definition, all technologies being applied in actual systems go through TRL 8. In
almost all cases, this level is the end of true ‘system development’ for most technology
elements. Example: this would include DDT&E through Theoretical First Unit (TFU) for
a new reusable launch vehicle. This might include integration of new technology into an
existing system. Example: loading and testing successfully a new control algorithm into
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the onboard computer on Hubble Space Telescope while in orbit.
Cost to Achieve: Mission specific; typically highest unique cost for a new technology
(investment = “Phase C/D to TFU” for actual system)
TRL 9
Actual system “flight proven” through successful
mission operations
By definition, all technologies being applied in actual systems go through TRL 9. In
almost all cases, the end of last ‘bug fixing’ aspects of true ‘system development’. For
example, small fixes/changes to address problems found following launch (through ‘30
days’ or some related date). This might include integration of new technology into an
existing system (such operating a new artificial intelligence tool into operational mission
control at JSC). This TRL does not include planned product improvement of ongoing or
reusable systems. For example, a new engine for an existing RLV would not start at
TRL 9: such ‘technology’ upgrades would start over at the appropriate level in the TRL
system.
Cost to Achieve: Mission Specific; less than cost of TRL 8
(e.g., cost of launch plus 30 days of mission operations)
