Technology readiness levels (TRL) are a nine-step scale for describing how mature a technology is, from the first observation of a basic principle (TRL 1) to a system proven in real operation (TRL 9). The scale was developed at NASA and is now used across government, research and industry to plan R&D, judge risk and decide what it will take to get a technology into service. This article explains the nine levels and what they mean in practice for industrial and scientific systems.
The nine technology readiness levels
| TRL | Description | What it looks like for an industrial or scientific system |
|---|---|---|
| 1 | Basic principles observed | A physical effect or measurement idea is described in research |
| 2 | Technology concept formulated | A practical application of the idea is proposed |
| 3 | Experimental proof of concept | A bench test shows the core idea works on real samples |
| 4 | Technology validated in the lab | Key components work together in a lab setup |
| 5 | Technology validated in a relevant environment | Components tested under realistic conditions: real parts, speeds, lighting or noise |
| 6 | Technology demonstrated in a relevant environment | A working prototype system performs in realistic conditions |
| 7 | System prototype demonstrated in an operational environment | A near-final system runs on the production line or in the lab where it will be used |
| 8 | System complete and qualified | The final design is tested, documented and accepted |
| 9 | Actual system proven in operation | Systems run reliably in day-to-day production or research use |
Grouping the levels
How TRL maps to prototype stages
TRL lines up closely with the stages of prototype development. A feasibility study and proof of concept take an idea to around TRL 3. A functional prototype tested on real samples reaches TRL 4 to 6. A pilot unit running in production reaches TRL 7, and a qualified, documented design with systems in use reaches TRL 8 and 9.
Why the jump from TRL 6 to TRL 7 is hard
Many promising technologies stall between a prototype that works in realistic conditions and a system that works in real operation. The reasons are rarely the core idea. They are integration, reliability, operator use, maintenance, documentation and the cost of building more than one. Planning for those early, with a design that is modeled in 3D, built for service and documented as it goes, is what gets a system across that gap. See prototype to production.
TRL and manufacturing readiness levels
TRL measures the technology. Manufacturing readiness levels (MRL), a related scale used in defense programs, measure whether it can be built repeatably and affordably. A system can be technically mature but hard to build. For industrial equipment and instruments that will be built in quantity, both matter.
Using TRL in your own projects
- State the current TRL honestly, with the evidence behind it
- Set the target TRL for the end of each stage
- Spend first on the experiments that answer the biggest open question
- Treat the step to operational use (TRL 7) as a project of its own
- Reassess at every gate, not just at the end
Frequently asked questions
A nine-step scale, developed at NASA, that describes how mature a technology is, from basic principles observed (TRL 1) to an actual system proven in operation (TRL 9).
TRL 1 basic principles observed; TRL 2 technology concept formulated; TRL 3 experimental proof of concept; TRL 4 validated in the lab; TRL 5 validated in a relevant environment; TRL 6 demonstrated in a relevant environment; TRL 7 system prototype in an operational environment; TRL 8 system complete and qualified; TRL 9 actual system proven in operation.
It depends on how and where it has been tested. A bench proof of concept is around TRL 3, a prototype tested in realistic conditions TRL 5 to 6, and a prototype running in real operation TRL 7.
TRL measures how mature a technology is. MRL, manufacturing readiness level, measures how ready it is to be produced repeatably and affordably.
