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Technology readiness levels (TRLs) are a method for estimating the maturity of technologies during the acquisition phase of a program. TRLs enable consistent and uniform discussions of technical maturity across different types of technology.[1] TRL is determined during a technology readiness assessment (TRA) that examines program concepts, technology requirements, and demonstrated technology capabilities. TRLs are based on a scale from 1 to 9 with 9 being the most mature technology.[1]

TRL was developed at NASA during the 1970s. The US Department of Defense has used the scale for procurement since the early 2000s. By 2008 the scale was also in use at the European Space Agency (ESA).[2] The European Commission advised EU-funded research and innovation projects to adopt the scale in 2010.[1] TRLs were consequently used in 2014 in the EU Horizon 2020 program. In 2013, the TRL scale was further canonized by the International Organization for Standardization (ISO) with the publication of the ISO 16290:2013 standard.[1]

A comprehensive approach and discussion of TRLs has been published by the European Association of Research and Technology Organisations (EARTO).[3] Extensive criticism of the adoption of TRL scale by the European Union was published in The Innovation Journal, stating that the "concreteness and sophistication of the TRL scale gradually diminished as its usage spread outside its original context (space programs)".[1]

Definitions

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TRL NASA usage[4] European Union[5]
1 Basic principles observed and reported Basic principles observed
2 Technology concept and/or application formulated Technology concept formulated
3 Analytical and experimental critical function and/or characteristic proof-of concept Experimental proof of concept
4 Component and/or breadboard validation in laboratory environment Technology validated in lab
5 Component and/or breadboard validation in relevant environment Technology validated in relevant environment (industrially relevant environment in the case of key enabling technologies)
6 System/subsystem model or prototype demonstration in a relevant environment (ground or space) Technology demonstrated in relevant environment (industrially relevant environment in the case of key enabling technologies)
7 System prototype demonstration in a space environment System prototype demonstration in operational environment
8 Actual system completed and "flight qualified" through test and demonstration (ground or space) System complete and qualified
9 Actual system "flight proven" through successful mission operations Actual system proven in operational environment (competitive manufacturing in the case of key enabling technologies; or in space)


Assessment tools

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DAU Decision Point / TPMM Transition Mechanisms
DAU Decision Point / TPMM Transition Mechanisms

A Technology Readiness Level Calculator was developed by the United States Air Force.[6] This tool is a standard set of questions implemented in Microsoft Excel that produces a graphical display of the TRLs achieved. This tool is intended to provide a snapshot of technology maturity at a given point in time.[7]

The Defense Acquisition University (DAU) Decision Point (DP) Tool originally named the Technology Program Management Model was developed by the United States Army.[8] and later adopted by the DAU. The DP/TPMM is a TRL-gated high-fidelity activity model that provides a flexible management tool to assist Technology Managers in planning, managing, and assessing their technologies for successful technology transition. The model provides a core set of activities including systems engineering and program management tasks that are tailored to the technology development and management goals. This approach is comprehensive, yet it consolidates the complex activities that are relevant to the development and transition of a specific technology program into one integrated model.[9]

Uses

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The primary purpose of using technology readiness levels is to help management in making decisions concerning the development and transitioning of technology. It is one of several tools that are needed to manage the progress of research and development activity within an organization.[10]

Among the advantages of TRLs:[11]

  • Provides a common understanding of technology status
  • Risk management
  • Used to make decisions concerning technology funding
  • Used to make decisions concerning transition of technology

Some of the characteristics of TRLs that limit their utility:[11]

  • Readiness does not necessarily fit with appropriateness or technology maturity
  • A mature product may possess a greater or lesser degree of readiness for use in a particular system context than one of lower maturity
  • Numerous factors must be considered, including the relevance of the products' operational environment to the system at hand, as well as the product-system architectural mismatch

TRL models tend to disregard negative and obsolescence factors. There have been suggestions made for incorporating such factors into assessments.[12]

For complex technologies that incorporate various development stages, a more detailed scheme called the Technology Readiness Pathway Matrix has been developed going from basic units to applications in society. This tool aims to show that a readiness level of a technology is based on a less linear process but on a more complex pathway through its application in society.[13]

History

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Technology readiness levels were conceived at NASA in 1974 and formally defined in 1989. The original definition included seven levels, but in the 1990s NASA adopted the nine-level scale that subsequently gained widespread acceptance.[14]

Original NASA TRL Definitions (1989)[15]

Level 1 – Basic Principles Observed and Reported
Level 2 – Potential Application Validated
Level 3 – Proof-of-Concept Demonstrated, Analytically and/or Experimentally
Level 4 – Component and/or Breadboard Laboratory Validated
Level 5 – Component and/or Breadboard Validated in Simulated or Realspace Environment
Level 6 – System Adequacy Validated in Simulated Environment
Level 7 – System Adequacy Validated in Space

The TRL methodology was originated by Stan Sadin at NASA Headquarters in 1974.[14] Ray Chase was then the JPL Propulsion Division representative on the Jupiter Orbiter design team. At the suggestion of Stan Sadin, Chase used this methodology to assess the technology readiness of the proposed JPL Jupiter Orbiter spacecraft design.[citation needed] Later Chase spent a year at NASA Headquarters helping Sadin institutionalize the TRL methodology. Chase joined ANSER in 1978, where he used the TRL methodology to evaluate the technology readiness of proposed Air Force development programs. He published several articles during the 1980s and 90s on reusable launch vehicles utilizing the TRL methodology.[16]

These documented an expanded version of the methodology that included design tools, test facilities, and manufacturing readiness on the Air Force Have Not program.[citation needed] The Have Not program manager, Greg Jenkins, and Ray Chase published the expanded version of the TRL methodology, which included design and manufacturing.[citation needed] Leon McKinney and Chase used the expanded version to assess the technology readiness of the ANSER team's Highly Reusable Space Transportation (HRST) concept.[17] ANSER also created an adapted version of the TRL methodology for proposed Homeland Security Agency programs.[18]

The United States Air Force adopted the use of technology readiness levels in the 1990s.[citation needed]

In 1995, John C. Mankins, NASA, wrote a paper that discussed NASA's use of TRL, extended the scale, and proposed expanded descriptions for each TRL.[1] In 1999, the United States General Accounting Office produced an influential report[19] that examined the differences in technology transition between the DOD and private industry. It concluded that the DOD takes greater risks and attempts to transition emerging technologies at lesser degrees of maturity than does private industry. The GAO concluded that use of immature technology increased overall program risk. The GAO recommended that the DOD make wider use of technology readiness levels as a means of assessing technology maturity prior to transition.[20]

In 2001, the Deputy Under Secretary of Defense for Science and Technology issued a memorandum that endorsed use of TRLs in new major programs. Guidance for assessing technology maturity was incorporated into the Defense Acquisition Guidebook.[21] Subsequently, the DOD developed detailed guidance for using TRLs in the 2003 DOD Technology Readiness Assessment Deskbook.

Because of their relevance to Habitation, 'Habitation Readiness Levels (HRL)' were formed by a group of NASA engineers (Jan Connolly, Kathy Daues, Robert Howard, and Larry Toups). They have been created to address habitability requirements and design aspects in correlation with already established and widely used standards by different agencies, including NASA TRLs.[22][23]

More recently, Dr. Ali Abbas, Professor of chemical engineering and Associate Dean of Research at the University of Sydney and Dr. Mobin Nomvar, a chemical engineer and commercialisation specialist, have developed Commercial Readiness Level (CRL), a nine-point scale to be synchronised with TRL as part of a critical innovation path to rapidly assess and refine innovation projects to ensure market adoption and avoid failure.[24]

In the European Union

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The European Space Agency[1] adopted the TRL scale in the mid-2000s. Its handbook[2] closely follows the NASA definition of TRLs. In 2022, the ESA TRL Calculator was released to the public. The universal usage of TRL in EU policy was proposed in the final report of the first High Level Expert Group on Key Enabling Technologies,[25] and it was implemented in the subsequent EU framework program, called Horizon 2020, running from 2013 to 2020,[1] and has been retained in the EU's following framework programs. This means it is applied not only to space and weapons programs, but everything from nanotechnology to informatics and communication technology.

See also

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Technology readiness level

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from Grokipedia
Technology Readiness Levels (TRLs) are a standardized used to evaluate the maturity of a particular technology on a scale from 1 (basic principles observed) to 9 (actual proven through successful mission operations). Developed originally by to gauge the progress of technologies from conceptual research to operational deployment, TRLs provide a common language for assessing development risks, costs, and integration challenges across projects. The framework emphasizes progressive validation through analytical studies, laboratory testing, prototypes, and real-world demonstrations, helping organizations decide when to invest in or transition technologies. The TRL concept originated in 1974 when researcher Stan Sadin proposed a seven-level scale to assess maturity for missions, which was later expanded and formally defined in a 1989 report. By the 1990s, the scale was refined to nine levels and gained widespread adoption within and U.S. industry, particularly after its integration into acquisition processes to reduce program overruns. This evolution aligned TRLs with the , from fundamental research to flight-proven systems, and influenced similar metrics like Manufacturing Readiness Levels (MRLs). The nine TRL levels are defined as follows:
  • TRL 1: Basic principles observed and reported, with scientific research beginning to translate into future applications.
  • TRL 2: Technology concept and/or application formulated, often through applied research with speculative practical problems identified.
  • TRL 3: Analytical and experimental critical function and/or characteristic proof-of-concept demonstrated in a environment.
  • TRL 4: Component and/or validation in a environment, integrating basic components into a functional system.
  • TRL 5: Component and/or validation in a relevant environment, tested under simulated operational conditions.
  • TRL 6: System/subsystem model or prototype demonstration in a relevant environment, representing a major step in maturity.
  • TRL 7: System prototype demonstration in an operational environment, such as space for applications.
  • TRL 8: Actual system completed and qualified through test and demonstration, flight qualified for space missions.
  • TRL 9: Actual system proven through successful mission operations, marking full technological maturity.
Beyond , TRLs have been adopted by the U.S. Department of Defense (DoD) since the early 2000s to standardize technology assessments in acquisition programs, ensuring critical technology elements reach sufficient maturity before major investments. The (ESA) also employs TRLs to measure technology progress for space applications, requiring levels 5–6 for payload integration in missions. The TRL scale was formalized internationally through ISO 16290:2013. This global use extends to industries like and , where TRLs facilitate and international collaboration on complex systems.

Fundamentals

Definition and Purpose

Technology Readiness Levels (TRL) constitute a nine-point scale designed to measure the maturity of a technology, progressing from basic principles observed and reported (TRL 1) to full operational deployment in a relevant environment (TRL 9). This framework quantifies the advancement of evolving technologies by evaluating their progression through analytical studies, laboratory demonstrations, and real-world testing. The primary purpose of TRL is to offer a standardized for assessing technological , informing decisions, and facilitating by determining a technology's readiness for integration into larger systems. By assigning a numerical maturity level, TRL enables developers and decision-makers to gauge how closely a technology aligns with operational requirements, thereby supporting systematic advancement from conceptual to practical application. Key benefits of the TRL framework include reducing uncertainty in processes, enhancing communication among stakeholders such as engineers, managers, and funders, and enabling phased allocation of resources based on verified progress. This approach emerged in response to the inherent challenges of evaluating unproven technologies for integration into complex systems, such as , where extensive validation is essential to mitigate failures in high-stakes environments.

The TRL Scale

The Technology Readiness Level (TRL) scale consists of nine distinct levels that measure the maturity of a technology from initial scientific discovery to full operational deployment. Developed by , this scale provides a structured framework for assessing progress, with each level representing increasing fidelity in validation, from theoretical principles to real-world performance. Transitions between levels are marked by key milestones, such as the shift from analytical models to physical prototypes and from controlled testing to operational integration, ensuring technologies advance only after demonstrating reliability in progressively demanding environments. The scale progresses through three primary phases: (TRL 1–3), technology development (TRL 4–6), and (TRL 7–9). At lower levels, emphasis is on observing principles and formulating concepts; mid-levels focus on validation in lab and relevant environments; higher levels require demonstration in operational settings. Key transition criteria include achieving proof-of-concept through experiments, validating components via prototyping, and proving end-to-end functionality under mission-like conditions, all while incorporating risk reduction through iterative testing.
TRL LevelDescriptionEnvironmentMaturity Indicators
TRL 1Basic principles observed and reported: Scientific research or engineering studies justify the basic principles of a technology, often through observation of phenomena or formulation of algorithms.N/A (Theoretical)Initial scientific knowledge; no hardware involved.
TRL 2Technology concept and/or application formulated: Invention begins; practical application is identified, with analytical tools for simulation or modeling developed.N/A (Conceptual)Defined characteristics and potential uses; applied research initiated.
TRL 3Analytical and experimental critical function or characteristic proof-of-concept: Active research demonstrates feasibility using breadboard or lab-scale models, with representative data collected.LaboratoryProof-of-concept via experiments; critical functions validated analytically or empirically.
TRL 4Component and/or breadboard validation in laboratory environment: Basic components integrated and tested in a lab setting to simulate operational conditions.LaboratoryStandalone prototyping; full-scale lab experiments confirming performance predictions.
TRL 5Component and/or breadboard validation in relevant environment: Prototype tested in environments simulating operational stresses, with realistic support elements.Relevant (Simulated operational)Integrated subsystem testing; interfaces and performance verified under representative conditions.
TRL 6System/subsystem model or prototype demonstration in a relevant environment: High-fidelity prototype demonstrates overall system feasibility in end-to-end scenarios.Relevant (End-to-end simulated)Partial integration; engineering feasibility proven with hardware-in-the-loop testing.
TRL 7System prototype demonstration in an operational environment: Prototype operates in actual mission conditions, demonstrating most functions.OperationalNear-full-scale integration; limited documentation and risk assessment completed.
TRL 8Actual system completed and qualified through test and demonstration: End-product tested in operational environment, meeting qualification standards.OperationalFull integration; verification, validation, and documentation finalized.
TRL 9Actual system proven through successful mission operations: Technology deployed and performs as expected in real missions, with ongoing support.Operational (Mission-proven)Thorough demonstration; sustaining engineering established for reliability.
These levels ensure a systematic maturation , where each advancement requires documented of performance alignment between predicted and actual results, reducing technical risks before significant investment. For instance, the transition from TRL 3 to TRL 4 typically involves moving from bench-scale proofs to integrated component tests, while TRL 6 to TRL 7 shifts from simulated to actual operational exposures.

Historical Development

NASA Origins

The concept of Technology Readiness Levels (TRLs) was first introduced at in the mid-1970s as a systematic approach to evaluate the maturity of emerging technologies for space applications. Developed by NASA engineer Stan Sadin within the Office of and , the initial framework consisted of seven levels and functioned as a discipline-independent metric to track technology progress from conceptual stages to operational deployment. This early iteration emerged amid 's expanding portfolio of complex missions, providing a standardized tool for assessing risks associated with . This early framework was formally defined in a 1989 report by Sadin et al., establishing the seven-level scale. In 1995, engineer John C. Mankins advanced this foundation by formalizing the TRL scale into its modern nine-level structure through a pivotal titled Technology Readiness Levels, issued by NASA's Advanced Concepts Office in the Office of Space Access and Technology. Mankins' document articulated detailed definitions and illustrative examples for each level—from TRL 1 (basic principles observed and reported) to TRL 9 (actual system proven through successful mission operations)—transforming TRLs into a comprehensive tailored for planning. This publication marked the first official codification of the scale, embedding it within NASA's internal guidelines such as Management Instruction 7100. TRLs were promptly adopted in NASA's Technology Readiness Assessment (TRA) processes for flagship projects, including the International Space Station (ISS), where subsystem demonstrations achieved TRL 6 in relevant environments to confirm integration feasibility. By the early 2000s, TRL evaluations had been fully incorporated into NASA's project lifecycle reviews, as mandated in procedural documents like NASA Procedural Requirements (NPR) 7120.5, which required maturity assessments at preliminary and critical design milestones to guide decision-making and resource allocation. These early implementations, such as TRA applications for ISS hardware validation, underscored TRLs' role in enhancing mission reliability during NASA's post-Shuttle era of collaborative space infrastructure development.

International Adoption

The U.S. Department of Defense (DoD) formally endorsed the use of Technology Readiness Levels (TRLs) in 2001, integrating them into its acquisition processes to evaluate technology maturity and manage risks in defense programs. This adoption built on NASA's framework, with the DoD issuing a Technology Readiness Assessment (TRA) Deskbook in 2003 to standardize assessments for critical technology elements across major acquisition categories, such as aircraft and missiles. The (ESA) incorporated TRLs into its technology development and evaluation processes in the mid-2000s, to ensure reliable progression from to operational deployment. ESA's handbook, published in , aligned closely with NASA's scale while tailoring criteria to space-specific challenges, such as and integration. By the , this incorporation supported ESA's broader technology strategy, emphasizing maturation activities across member states. Standardization efforts have further promoted international consistency in TRL application. The (ISO) published ISO 16290:2013, which defines TRLs specifically for space systems and provides criteria for their assessment, enabling uniform maturity evaluations across global space projects. Similarly, the American Institute of Aeronautics and Astronautics (AIAA) references TRLs in its technical standards and guidelines, such as those for aircraft design and propulsion systems, to guide technology integration and risk reduction in . Beyond defense and space, the U.S. Department of Energy (DOE) adopted TRLs in the late 2000s for assessing energy technologies, following recommendations from the Government Accountability Office to align with and DoD methodologies in major projects like nuclear and demonstrations. By the , TRLs saw widespread global adoption in non-aerospace sectors; for instance, automotive industries used them to evaluate components and autonomous driving systems, while biotechnology firms applied the scale to translational research for and tools. Adaptations of the TRL framework reflect sector-specific needs, with ESA placing particular emphasis on environmental testing to verify performance in space-like conditions, such as vacuum, , and extremes, during prototype demonstrations at TRL 6 and 7. This variation ensures technologies for missions like Ariane launches meet rigorous operational reliability without altering the core 1-9 scale.

Assessment Process

Evaluation Criteria

The evaluation of a technology's readiness level relies on core criteria that assess its progression through increasingly demanding environments, from controlled settings to relevant simulated conditions and finally to operational real-world scenarios. These environments are pivotal: lower TRLs (1-4) involve basic observation and component validation in lab conditions, mid-levels (5-6) require demonstrations in relevant environments that mimic operational stressors, and higher levels (7-9) demand full proof in actual operational contexts. Validation methods include analytical models and simulations for early stages, followed by physical s and rigorous testing such as flight or field trials in later phases, ensuring the technology's performance under realistic conditions. Evidence requirements emphasize verifiable data from experiments, including test reports, performance metrics, and peer-reviewed documentation, to substantiate claims of maturity without relying on anecdotal or unverified assertions. Quantitative aspects supplement these qualitative evaluations by incorporating measurable metrics to gauge progress and risks. Success rates in testing during prototype demonstrations in relevant environments for TRL 6 provide concrete benchmarks for advancement. estimates for scaling the technology to higher TRLs, often revealing potential overruns when immature components are integrated early, help quantify financial risks. Risk scoring, typically via matrices that tie technical uncertainties, schedule delays, and integration challenges to specific TRL thresholds, enables prioritized mitigation strategies before committing resources. These metrics ensure decisions are data-driven rather than subjective, with statistical significance required for test repetitions to validate performance against operational requirements. Decision gates at TRL transitions serve as critical points, informed by the accumulation of evidence from prior levels. For instance, advancing to TRL 6 often requires demonstrated success in a relevant environment with high fidelity to operations, while TRL 7 mandates operational environment testing to confirm system viability, as seen in requirements for U.S. Department of Defense Milestone B (targeting TRL 6) and Milestone C (TRL 7). These gates evaluate whether the technology meets predefined thresholds for functionality, reliability, and risk reduction, preventing progression if gaps persist. Failure to meet criteria at these junctures can lead to program delays or redesigns, underscoring the need for comprehensive TRA reports to support governance approvals. The role of experts is essential for interpreting these criteria, particularly in areas involving subjective judgments on maturity and context-specific factors. Multidisciplinary panels, typically comprising 3-5 independent subject matter experts from , , and relevant domains, conduct assessments to ensure objectivity and . These teams review evidence, resolve discrepancies through peer validation, and provide consensus ratings, often drawing on their specialized knowledge to weigh intangible risks like integration challenges. Program stakeholders may observe but not influence to maintain , with team qualifications documented to uphold the process's rigor.

Tools and Methodologies

NASA's Technology Readiness Assessment (TRA) Best Practices Guide provides step-by-step instructions for conducting assessments, including templates and worksheets to evaluate and assign TRLs to critical technology elements. These resources, updated in the , emphasize hierarchical analysis of components, subsystems, and systems, with specific question sets for each TRL range to ensure evidence-based justifications. For instance, the guide outlines a process starting with self-assessment by principal investigators, followed by peer validation using defined exit criteria for each level. The Department of Defense (DoD) employs methodologies that integrate TRL assessments with broader acquisition frameworks, such as the use of TRA reports during reviews to inform decisions on technology maturation. These assessments follow a five-step process—planning, identifying critical technology elements, evaluating maturity, reporting findings, and applying results—often aligned with practices to address risks in hardware and software. While not directly fused with the (CMM), DoD approaches complement process maturity evaluations by focusing on technology-specific demonstrations required for entry into engineering and development phases. Software tools facilitate standardized TRL scoring and documentation. NASA's Earth Science Technology Office offers an Excel-based TRL that automates calculations by prompting users for evidence against level-specific criteria, generating a maturity map for components and systems. Open-source alternatives, such as the European Space Agency's web-based TRL calculator, enable interactive assessments from TRL 3 to 7, incorporating user inputs on demonstrations and environments to output maturity scores. Best practices for TRL assessments include conducting iterative evaluations throughout development to track progress, incorporating peer reviews by subject matter experts for objectivity, and maintaining detailed of to support auditability and . These practices ensure assessments remain dynamic, with regular updates to maturation plans based on test results and risk analyses. As of 2025, digital platforms have emerged for collaborative TRL tracking, particularly in agile development environments. The TRA Tool, leveraging (MBSE), allows teams to model, simulate, and project TRL progression in shared digital twins, enabling real-time updates and integration with workflows. This approach supports distributed teams in visualizing technology risks and dependencies without relying on static documents.

Applications

In Aerospace and Defense

In the aerospace sector, NASA employs Technology Readiness Levels (TRLs) to guide the maturation of critical technologies for the Artemis program, ensuring they achieve sufficient maturity before integration into lunar missions. For instance, in-space resource utilization (ISRU) technologies, such as oxygen extraction from lunar regolith, have been advanced from low TRLs (1-2) to higher levels through targeted demonstrations, reducing uncertainties in resource-dependent systems like habitats and propulsion. This systematic assessment helps prioritize investments in lunar surface innovations, maturing mid-TRL components to support sustainable human presence on the Moon. Similarly, the (ESA) integrates TRL evaluations into the development of the rover, , to verify the maturity of planetary exploration technologies. Key subsystems, including robotic arms and force-torque sensors for sample acquisition, undergo TRL progression through laboratory prototypes and analog field tests, aligning with ESA's guidelines for space applications. This approach ensures that instruments and mobility systems meet operational demands on Mars, mitigating integration risks in a collaborative mission with international partners. In defense applications, the U.S. Department of Defense (DoD) mandates that critical technologies reach at least TRL 6—demonstration in a relevant environment—prior to Milestone B approval for major acquisition programs, as stipulated in acquisition policies to minimize technical risks during engineering and manufacturing development. For the F-35 , Technology Readiness Assessments (TRAs) evaluate components such as and power management systems; for example, a proposed electric power and cooling system achieved TRL 6 through ground-based prototypes simulating flight conditions. These assessments identified immature elements like the integrated core processor, prompting maturation efforts to support Block 4 upgrades. TRLs provide significant benefits in these high-stakes fields by mitigating mission risks, particularly for propulsion systems prone to failures in extreme environments. NASA's in-space propulsion technologies, such as the NEXT ion thruster, undergo TRL-based risk reduction through transient testing and vector stability demonstrations, enabling reliable performance in operational analogs and preventing issues like inefficient thrust during deep-space maneuvers. Pre-flight validations at TRL 6 and above ensure compatibility with mission architectures, as seen in propulsion maturation for lunar landers, thereby enhancing overall system reliability and avoiding costly redesigns.

In Research Funding

In the European Union's programme (2021-2027), Technology Readiness Levels (TRLs) serve as a key criterion for funding eligibility and project scope in collaborative and actions. and Actions (RIAs), which emphasize establishing new and feasibility studies, typically cover technologies from TRL 1 to 6, focusing on fundamental , experimental validation, and small-scale prototype development. In contrast, Actions (IAs) target higher maturity levels from TRL 6 to 8, supporting prototyping, demonstration, piloting, and market validation in relevant environments. For instance, the European Innovation Council's (EIC) Transition grants, part of , fund projects starting at TRL 3 or 4 and aiming to reach TRL 5 or 6, with budgets up to €2.5 million to bridge toward commercialization. In the United States, the (NSF) incorporates TRL assessments in programs like the Regional Innovation Engines to evaluate commercialization potential, assigning ratings based on demonstrated capabilities and progress toward market readiness. Similarly, the Department of Energy (DOE) mandates TRL evaluations in many Funding Opportunity Announcements (FOAs), such as those under the Office of Energy Efficiency and Renewable Energy, where projects often start at TRL 6-7 and advance to TRL 8-9 for demonstration and deployment, ensuring alignment with economic and societal impacts. The NSF's (SBIR) program, while not strictly requiring TRLs, encourages their use in proposals to demonstrate maturity and commercial viability, particularly in Phase II awards that build prototypes. TRLs function as a gatekeeper in research funding, delineating phases of support and unlocking progressively larger budgets as maturity increases; for example, the (ERC) grants provide up to €150,000 to explore potential from early-stage ERC-funded research, often advancing from TRL 1-3 toward proof-of-concept validation. This phased approach ensures resources are allocated efficiently, with lower TRLs receiving foundational funding and higher levels accessing demonstration-scale investments. In the EU, this emphasis on TRLs evolved post-2014 with the launch of Horizon 2020, where the scale was first systematically integrated into work programmes to prioritize market-oriented actions.

Manufacturing and Integration Readiness

The Manufacturing Readiness Level (MRL) is a standardized metric developed by the (DoD) to evaluate the maturity of manufacturing processes and production capabilities for . Introduced in 2005, the MRL scale consists of 10 levels, progressing from basic manufacturing implications identified at MRL 1—where initial concepts and potential production challenges are outlined—to full-rate production demonstrated at MRL 10, which includes lean practices and continuous improvement in operational environments. This scale assesses key threads such as , , materials, processes, , facilities, and management to identify risks and ensure producibility aligns with acquisition milestones. Complementing the MRL, the Integration Readiness Level (IRL) addresses the maturity of integrating multiple technologies or subsystems into a cohesive system, particularly in complex environments like system-of-systems architectures. Proposed in 2007 by researchers at , the IRL uses a 9-level scale starting at IRL 1, where basic interfaces between components are merely identified, and culminating at IRL 9, where full and mission-proven integration are achieved through verified performance in operational settings. Unlike individual component validation, IRL emphasizes compatibility, data exchange, and control mechanisms to mitigate integration risks. While the Technology Readiness Level (TRL) primarily gauges the maturity of individual technologies from basic principles to operational deployment, MRL focuses on the scalability and cost-effectiveness of production, and IRL evaluates how well those technologies combine without unforeseen interactions. These metrics are often assessed concurrently during technology maturation to provide a holistic view of readiness, with MRL and IRL thresholds typically aligned to corresponding TRL gates—for instance, achieving MRL 6 or IRL 6 before advancing to higher TRL demonstrations. In practice, this integrated approach helps decision-makers balance technical with practical challenges. In the sector, MRL and IRL are particularly valuable for managing complexities in large-scale programs. For example, during the development of the , assessments akin to MRL frameworks were employed to evaluate production maturity across a global supplier network, ensuring that processes and assembly integration met scalability requirements despite initial delays in synchronization. Such applications highlight how these readiness levels reduce risks in transitioning from prototypes to high-volume , fostering reliable outcomes in defense and projects.

Other Specialized Levels

In specialized domains, Technology Readiness Levels (TRLs) are adapted to address unique development dynamics, such as in software or regulatory and ethical considerations in biomedical fields. These modifications ensure the framework aligns with domain-specific milestones while maintaining the core nine-level scale. For instance, adaptations emphasize validation methods tailored to intangible elements like code or biological interactions, rather than solely physical integration. NASA has adapted TRLs for software-intensive technologies, incorporating specific descriptors for each level to prioritize code validation, , and simulation-based testing over hardware environments. At TRL 3, limited software functionality is validated for critical properties using non-integrated components; by TRL 5, end-to-end testing occurs in simulated environments mimicking operational conditions; and at TRL 8, the software undergoes thorough , full integration with operational systems, and completion of processes. These adjustments account for software's iterative nature, where bugs are iteratively removed and is developed progressively, contrasting with hardware's emphasis on physical prototypes. In biomedical technologies, variants developed by agencies like the FDA, NIH, and VA integrate regulatory milestones, particularly for drugs, biologics, and medical devices. For drug and biological products, TRL 4 involves optimizing safety and efficacy through non-GLP in vivo studies and identifying preclinical candidates, while TRL 5 advances to IND-enabling toxicology studies and pre-IND FDA meetings. Preclinical trials typically align with TRLs 4-5, transitioning to Phase I clinical trials at TRL 6 after IND submission. For medical devices, adaptations include pre-IDE FDA meetings at TRL 5 for prototype optimization and clinical studies leading to FDA clearance at TRL 8. The NIH's National Center for Advancing Translational Sciences often funds projects at TRLs 3-5, focusing on proof-of-concept and preclinical validation to bridge to clinical application. These changes accommodate biomedical development's need for ethical oversight, biological variability, and phased regulatory approvals, which extend timelines beyond standard hardware prototyping. Adaptations for environmental and green technologies incorporate sustainability assessments to evaluate lifecycle impacts, such as and emissions reduction. The (ESA) applies TRLs within its Clean Space initiative to green technologies, assessing maturity alongside environmental benefits like reduced mission and hazardous material minimization. A related framework, Sustainability Readiness Levels (SRLs), extends TRLs by measuring net positive environmental outcomes, where higher levels require demonstrated benefits outweighing drawbacks across system effects. These variants address green tech's focus on holistic impacts, including scalability for climate adaptation, differing from standard TRLs that overlook long-term ecological constraints. Domain-specific challenges arise because standard TRLs, rooted in hardware-physical testing, inadequately capture software's agile iterations without fixed environments or biomedical/green tech's regulatory and sustainability hurdles, necessitating tweaks like simulation proxies or integrated ethical metrics to prevent mismatched risk assessments.

Limitations and Criticisms

Challenges in Application

One major challenge in applying Technology Readiness Levels (TRLs) stems from the inherent subjectivity in assessments, where variations in assessor interpretations often lead to inconsistent ratings across evaluations. Studies have highlighted that the TRL scale can be subjective and biased due to differing expertise levels and lack of standardized training, resulting in discrepancies in how maturity is gauged. For instance, reviews have identified over-optimistic self-assessments by project teams and varied interpretations of TRL definitions as key sources of inconsistency in the assessment process. Ambiguity in defining "relevant" versus "operational" environments further complicates TRL application, particularly for technologies outside , such as software systems. In traditional TRL frameworks developed for hardware contexts, the distinction between simulated or lab-based testing (relevant environment) and real-world deployment (operational environment) is clear, but this becomes unclear for non-physical technologies like software, where virtual environments may serve as proxies yet lack consensus on their equivalence to operational conditions. Adaptations for fields like research have addressed this by limiting reliance on "operational" demonstrations and emphasizing contextual validation, underscoring the need for tailored definitions to avoid misaligned maturity judgments. An overemphasis on achieving high TRLs in funding decisions can discourage investment in early-stage innovation, as programs prioritize technologies closer to deployment over foundational research. In EU initiatives like , this focus has created gaps in early-stage funding, with low TRL (1-3) projects often underutilized despite their role in generating novel ideas, leading to calls for redirecting resources to bridge the "valley of death" between and demonstration phases. Such biases risk stifling long-term breakthroughs by favoring incremental advancements in mature technologies. Scalability issues arise when applying TRLs to complex, multi-technology systems, such as AI-integrated hardware, where individual component maturity does not guarantee system-level integration. Machine learning systems, for example, often develop in siloed testbeds without accounting for interoperability with hardware or downstream tasks, leading to challenges in propagating uncertainties across the entire architecture and hindering progression beyond mid-level TRLs. This is exacerbated by the lack of principled methods for assessing reliability in dynamic, multi-tech environments, making it difficult to scale assessments for large-scale deployments.

Proposed Improvements

To address the limitations of standalone Technology Readiness Levels (TRLs), hybrid models have been proposed that integrate TRLs with Manufacturing Readiness Levels (MRLs) and Integration Readiness Levels (IRLs) to provide a more holistic assessment of technology maturity across technical, manufacturing, and integration dimensions. This approach, detailed in a method for combining these scales, enables better in complex systems by evaluating how well technologies integrate and scale in production environments. The U.S. Department of Defense (DoD) has incorporated such hybrid frameworks into its processes during the , with updates to the MRL Deskbook emphasizing coordinated assessments to align technology development with acquisition milestones. Quantitative enhancements to TRL assessments aim to introduce greater objectivity through probabilistic models, which estimate the likelihood of a advancing from one TRL to another within a given timeframe, thereby informing scheduling and . For instance, statistical models have been developed to predict TRL progression probabilities based on historical data, reducing subjective biases in traditional assessments. Additionally, AI-assisted scoring tools leverage to automate TRL evaluations by analyzing project documentation and performance metrics, offering consistent and scalable assessments for large portfolios. These methods, including intelligent virtual assistants for TRL calculation, have shown promise in streamlining evaluations while maintaining alignment with established criteria. As alternatives to the linear TRL scale, multi-dimensional frameworks such as Readiness Level Matrices have been suggested to capture interactions between technology components, providing a matrix-based view of maturity across multiple axes like technical, operational, and programmatic readiness. The U.S. Government Accountability Office (GAO) has advocated for supplementary measures, including the Degree of Difficulty (R&D³) scale, which complements TRLs by quantifying complexity and innovation risks in a five-level structure. These alternatives enable more nuanced in funding and development by avoiding oversimplification of maturity. Recent proposals as of focus on adapting TRLs for modern development paradigms, such as the European Space Agency's (ESA) TRL Calculator tool, which supports dynamic assessments in agile space projects by allowing iterative updates to maturity ratings based on evolving requirements. These updates aim to make TRLs more flexible for rapid iteration cycles in software-heavy and collaborative environments.

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