Technology Readiness Level (TRL)
The technology Readiness Level (TRL) is an assessment of the maturity of a technology. In general, TRLs 1 to 4 describe basic research with both analytical studies and laboratory experiments, 5 to 8 engineering efforts, and 9 indicates a mature space-proven product.
After a period of chaos during which different organisations defined TRLs in different ways, ESA worked with ISO to create a recognised set of guidelines. Today, the definitions of TRL levels are specified in "ISO 16290, Space systems — Definition of the Technology Readiness Levels (TRLs) and their criteria of assessment". The standard was officially adopted by ECSS with "ECSS-E-AS-11C – Adoption Notice of ISO 16290" [1].
Specification of TRL Levels
For each TRL, we report the ECSS name, and expectations required to progress to the next level. The "Milestone Achieved" field describes the outcomes necessary to move to the next TRL.
TRL 1 - Basic principle observed and reported
Basic research. A new behaviour is identified and explored, but the practical applications have not yet been developed. The focus is on understanding the process.
| Milestone Achieved | Work Achievement |
|---|---|
| Potential applications are identified following basic observations but element concept not yet formulated |
- Expression of the basic principles intended for use. - Identification of potential applications |
TRL 2 - Technology concept and/or application formulated
The technology is well understood enough that a potential application can be identified, but further research is before a proof-of-concept can be created. There is an idea, but no clarity on how to actually implement it. There is no experimental proof
The project is moving from fundamental science, to applied science.
| Milestone Achieved | Work Achievement |
|---|---|
| Formulation of potential applications and preliminary element concept. No proof of concept yet. |
- Formulation of potential applications. - Preliminary conceptual design of the element, providing understanding of how the basic principles would be used. |
TRL 3 - Analytical and experimental critical function and/or characteristic proof-of-concept
The concept is clear, but laboratory measurements are needed to characterise the expected performance. The goal is to ensure that the concept works as intended. To do so, individual components of the technology are tested individually. Modelling and simulation may be used to fill in the gaps.
| Milestone Achieved | Work Achievement |
|---|---|
| Element concept is elaborated and expected performance is demonstrated through analytical models supported by experimental data/characteristics. | - Preliminary performance requirements (can target several missions) including definition of functional performance requirements. - Conceptual design of the element. - Experimental data inputs, laboratory-based experiment definition and results. - Element analytical models for the proof-of-concept. |
TRL 4 - Component and/or breadboard functional verification in laboratory environment
A Breadboard of the system is created to validate the physical concept. Multiple components of the technology are integrated together to ensure that they operate as expected in the lab environment.
Little by little, the project is moving from scientific research, towards engineering.
| Milestone Achieved | Work Achievement |
|---|---|
| Element functional performance is demonstrated by breadboard testing in laboratory environment | - Preliminary performance requirements (can target several missions) with definition of functional performance requirements. - Conceptual design of the element. - Functional performance test plan. - Breadboard definition for the functional performance verification. - Breadboard test reports. |
TRL 5 - Component and/or breadboard critical function verification in a relevant environment
The Breadboard continues to mature, and can now be tested in a relevant environment (usually a simulation of the operational environment). If necessary, the system can be scaled up or down to facilitate testing, but the effect of the scaling must be taken into account.
The definition of a representative environment depends on the application, but, for space systems, this usually includes thermal, vacuum, or radiation testing.
The Breadboard is now representative enough that scientific risk has been eliminated, and only engineering risk remains.
| Milestone Achieved | Work Achievement |
|---|---|
| Critical functions of the element are identified and the associated relevant environment is defined. Breadboards (potentially not full-scale) are built for verifying the performance through testing in the relevant environment, subject to scaling effects. |
- Preliminary definition of performance requirements and of the relevant environment. - Identification and analysis of the element critical functions. - Preliminary design of the element, supported by appropriate models for the critical functions verification. - Critical function test plan. Analysis of scaling effects. - Breadboard definition for the critical function verification. - Breadboard test reports |
TRL 6 - Model demonstrating the critical functions of the element in a relevant environment
There is confidence that the performance requirements can be achieved. The Breadboard-level tests were successful. The goal is now to move from components on a workbench to a fully functional prototype.
The model, usually an Engineering Model (EM), should be tested in a relevant environment, and have all the functionalities of the final flight model. The primary goal is to reduce the engineering risk before building the flight model.
| Milestone Achieved | Work Achievement |
|---|---|
| Critical functions of the element are verified, performance is demonstrated in the relevant environment and representative model(s) in form, fit and function. |
- Definition of performance requirements and of the relevant environment. - Identification and analysis of the element critical functions. - Design of the element, supported by appropriate models for the critical functions verification. - Critical function test plan. - Model definition for the critical function verifications. - Model test reports |
TRL 7 - Model demonstrating the element performance for the operational environment
Having tested a prototype, the goal is now to validate the performance of a representative model of the system in the target environment.
The design of the system is practically complete, and the goal is to eliminate the remaining engineering and manufacturing risk by testing a Qualification Model (QM) in the operational environment. In some cases, this may involve flying the system on a separate mission to exercise it in outer space.
| Milestone Achieved | Work Achievement |
|---|---|
| Performance is demonstrated for the operational environment, on the ground or if necessary in space. A representative model, fully reflecting all aspects of the flight model design, is built and tested with adequate margins for demonstrating the performance in the operational environment. |
- Definition of performance requirements, including definition of the operational environment. - Model definition and realisation. - Model test plan. - Model test results. |
TRL 8 - Actual system completed and accepted for flight
Having tested the system in all relevant conditions, the customer has accepted the system and it is now "flight-qualified". All that's missing now is the actual launch.
| Milestone Achieved | Work Achievement |
|---|---|
| Flight model is qualified and integrated in the final system ready for flight. | - Flight model is built and integrated into the final system. - Flight acceptance of the final system. |
TRL 9 - Actual system flight proven through successful mission operations
The system has launched, and is operating successfully in space. The technology is considered mature, and you can proudly tell your customers that it is TRL9.
Remember, if you change anything you lose that precious TRL and need to start again.
| Milestone Achieved | Work Achievement |
|---|---|
| Technology is mature. The element is successfully in service for the assigned mission in the actual operational environment | Commissioning in early operation phase. In-orbit operation report |