Technology Readiness Levels (TRL)

Technology Readiness Levels were developed by NASA in 1974 to enable it to procure multiple technologies at different stages of development for large and complex space missions. It has subsequently been expanded and extended to other sectors, but it still finds its best use in complex engineering projects where multiple partially developed technologies need to be brought together in the final product. Examples include aerospace, automotive and nuclear engineering.

The different levels are most precisely defined in aerospace covering the range from initial scientific observation (TRL 1) to ‘flight proven’ (TRL9). TRL definitions include:

• TRL 1 – Basic principles observed and reported
• TRL 3 – Proof of concept
• TRL 4 – Component tested and validated in the lab
• TRL 7 – Complete prototype tested in flight
• TRL 9 – Flight proven through actual missions

Outside the very specific environment of highly complex engineering projects, a looser TRL scale is used.