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/sub-system model or prototype demonstration in an operational environment.
TRL-7 System prototype demonstration in an operational environment.
TRL-8 Actual system completed and “flight qualified” through test and demonstration.
TRL-9 Actual system flight proven through successful mission operations.
TRL-2 Invention begins, practical application is identified but is speculative, no experimental proof or detailed analysis is available to support the conjecture.
TRL-3 Analytical studies place the technology in an appropriate context and laboratory demonstrations, modeling and simulation validate analytical prediction.
TRL-4 A low fidelity system/component breadboard is built and operated to demonstrate basic functionality and critical test environments, and associated performance predictions are defined relative to the final operating environment.
TRL-5 A medium fidelity system/component brassboard is built and operated to demonstrate overall performance in a simulated operational environment with realistic support elements that demonstrates overall performance in critical areas. Performance predictions are made for subsequent development phases.
TRL-6 A high fidelity system/component prototype that adequately addresses all critical scaling issues is built and operated in a relevant environment to demonstrate operations under critical environmental conditions.
TRL-7 A high fidelity engineering unit that adequately addresses all critical scaling issues is built and operated in a relevant environment to demonstrate performance in the actual operational environment and platform (ground, airborne, or space).
TRL-8 The final product in its final configuration is successfully demonstrated through test and analysis for its intended operational environment and platform (ground, airborne, or space).
TRL-9 The final product is successfully operated in an actual mission.
NASA “Technology Readiness Level Definitions”
NASA(2012) “Technology Readiness Level” Oct. 29, 2012