Technology Readiness Levels (TRL) Explained for Defense Programs

Technology readiness levels (TRL) are a nine-point scale, from TRL 1 for basic principles observed to TRL 9 for a system proven in actual operations, that governments use to judge how mature a technology really is before they pay to build it. Invented at NASA in the 1970s, the scale is now a standard yardstick in defense acquisition.

9

Levels on the TRL scale

1970s

Decade NASA first used the scale

TRL 6

Typical gate before a program enters development

TRL 9

Proven in actual operations

What are technology readiness levels

A technology readiness level is a label that says how far a technology has progressed from an idea to a fielded product. The scale was created at NASA in the 1970s, formalized in the 1980s and 1990s, and adopted by the US Department of Defense in the early 2000s after auditors found that programs were repeatedly starting development with immature technology and then overrunning their budgets. The European Union and NATO now use variants of the same scale.

The idea is simple. Each level requires a specific kind of evidence: a paper concept, a laboratory test, a prototype in a relevant environment, then a demonstration in a real one. A technology cannot skip levels by assertion, only by showing test results.

TRL 1 to TRL 9 explained

The nine technology readiness levels

TRL	Definition	Typical evidence
1	Basic principles observed and reported	Scientific research, papers
2	Technology concept formulated	Analytical studies, early designs
3	Experimental proof of concept	Laboratory experiments of key functions
4	Component validated in laboratory	Breadboard tests of integrated parts
5	Component validated in relevant environment	Higher-fidelity tests with realistic conditions
6	System prototype demonstrated in relevant environment	Representative prototype tested on a range
7	System prototype demonstrated in operational environment	Flight or field demonstration
8	System complete and qualified	Test and evaluation completed
9	System proven in actual operations	Successful mission use

Simplified from NASA and US Department of Defense TRL definitions.

The critical jump is between TRL 6 and TRL 7, where a prototype leaves the controlled test range and meets real conditions. Program managers often call the period before that point the valley of death, because many promising technologies stall there for lack of funding. Early levels are cheap and run by laboratories and universities, while the higher ones require expensive prototypes.

Why TRL matters in defense acquisition

The US Government Accountability Office has long recommended that major programs reach TRL 6 before entering system development, and TRL 7 before production. Programs that ignore that advice often pay for it later. A weapon that depends on an unproven seeker, engine or software component can see costs rise and schedules slip.

TRL is also a communication tool. It lets an engineer tell an executive, in one number, whether a claim is a slide or a hardware test. Companies selling to governments know that the number will be scrutinized, and inflating it is a recurring temptation. Budget analysts rely on the scale when deciding how risky a project is, which ties into the money questions covered in our guide to defense industry scale and revenue.

TRL examples in defense programs

Illustrative TRL positions of defense technologies

Technology	Approximate maturity	Comment
Operational hypersonic glide weapons	TRL 7 to 9 depending on program	Some countries claim fielding; demonstrated reliability varies and claims are often unverified
Gallium nitride radar	TRL 8 to 9	Fielded in several modern radars
High-energy laser weapons	TRL 6 to 7	Demonstrated on ships and vehicles, limited operational use
Collaborative combat aircraft	TRL 6 to 7	Prototypes flying, operational concepts still maturing
Quantum sensing for navigation	TRL 3 to 5	Laboratory and early field trials

Levels are illustrative and depend on the specific program, definition and date; they are not official assessments.

Fielded examples sit at the top of the scale. Gallium nitride radar has moved from laboratory promise to operational hardware in a single generation. In contrast, hypersonic weapons show how hard it is to read maturity from headlines: some countries announce deployment, yet test cadence and reliability are often not public. Drone wingmen, described in our collaborative combat aircraft guide, sit in the middle, with flying prototypes but still-evolving tactics.

Limits of the TRL scale

TRL measures the readiness of a single technology, not of a whole system or of the factory that must make it. Two companion scales, manufacturing readiness levels (MRL) and system readiness levels (SRL), were created to fill that gap. A technology can reach TRL 8 and still be unbuildable at scale.

The scale also says little about cost, integration difficulty or software. Modern programs increasingly depend on code, and software maturity moves differently from hardware. Some agencies now use separate software readiness measures or continuous-delivery approaches instead.

Editor’s read

TRL is most useful as a question rather than an answer. Ask what evidence supports the number, in what environment, and who performed the test.