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Grading NASA's Solar System Exploration Program: A Midterm Report D NASA Technology Readiness Levels Technology readiness levels (TRLs) are a systematic metric/measurement system that supports assessments of the maturity of a particular technology and the consistent comparison of maturity between different types of technology. TRLs were first introduced by NASA in the 1980s and initially included seven levels. The system was expanded, in a 1995 white paper,1 to include nine levels. Table D.1 summarizes each TRL. TABLE D.1 Summary of NASA Technology Readiness Levels Level Summary Description TRL 1 Basic principle observed and reported This is the lowest level of technology maturation. At this level, scientific research begins to be translated into applied research and development. Examples might include studies of basic properties of materials (e.g., tensile strength as a function of temperature for a new fiber). TRL 2 Technology concept and/or application formulated Once basic physical principles are observed, at the next level of maturation practical applications of those characteristics can be invented or identified. For example, following the observation of high critical temperature superconductivity, potential applications of the new material for thin-film devices (e.g., superconductor-insulator-superconductor mixers) and in instrument systems (e.g., telescope sensors) can be defined. At this level, the application is still speculative: there is not experimental proof or detailed analysis to support the conjecture. TRL 3 Analytical and experimental critical formula and/or characteristic proof of concept At this step in the maturation process, active research and development (R&D) is initiated. These studies and experiments should constitute “proof-of-concept” validation of the applications/concepts formulated at TRL 2. For example, a concept for high energy density matter (HEDM) propulsion might depend on slush or supercooled hydrogen as a propellant: TRL 3 might be attained when the concept-enabling phase/temperature/pressure for the fluid was achieved in a laboratory. TRL 4 Component and/ or breadboard validation in laboratory environment Following successful proof-of-concept work, basic technological elements must be integrated to establish that the “pieces” will work together to achieve concept-enabling levels of performance for a component and/or breadboard. For example, a TRL 4 demonstration of a new fuzzy logic approach to avionics might consist of testing the algorithms in a partially computer-based, partially bench-top component (e.g., fiber-optic gyros) demonstration in a controls laboratory using simulated vehicle inputs. 1 John C. Mankins, Advanced Concepts Office, Office of Space Access and Technology, NASA, Technology Readiness Levels, A White Paper, April 6, 1995.
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Grading NASA's Solar System Exploration Program: A Midterm Report Level Summary Description TRL 5 Component and/ or breadboard validation in relevant environment At this level, the fidelity of the component and/or breadboard being tested must increase significantly. The basic technological elements must be integrated with reasonably realistic supporting elements so that the total applications (component-level, subsystem-level, or system-level) can be tested in a simulated or somewhat realistic environment. From one to several new technologies might be involved in the demonstration. For example, a new type of solar photovoltaic material promising higher efficiencies would at this level be used in an actual fabricated solar array “blanket” that would be integrated with power supplies, supporting structure, and so on, and tested in a thermal vacuum chamber with solar simulation capability. TRL 6 System/ subsystem model or prototype demonstration in a relevant environment (ground or space) At TRL 6, a representative model or system prototype or system would be tested in a relevant environment. At this level, if the only relevant environment is the environment of space, then the model/prototype must be demonstrated in space. Not all technologies will undergo a TRL 6 demonstration: at this point the maturation step is driven more by assuring management confidence than by R&D requirements. For example, an innovative approach to high-temperature/low-mass radiators, involving liquid droplets and composite materials, would be demonstrated to TRL 6 by actually flying a working, subscale (but scaleable) model of the system on a space shuttle or International Space Station pallet. In this example, the reason that this space is the relevant environment is that microgravity plus vacuum plus thermal environment effects will dictate the success or failure of the system—and the only way to validate the technology is in space. TRL 7 System prototype demonstration in a space environment TRL 7 is a significant step beyond TRL 6, requiring an actual system prototype demonstration in a space environment. It has not always been implemented in the past. In this case, the prototype should be near or at the scale of the planned operational system, and the demonstration must take place in space. TRL 7 would normally only be performed in cases where the technology and/or subsystem application is mission-critical and relatively high-risk. Example: The Mars Pathfinder Rover is a TRL 7 technology demonstration for future Mars micro-rovers based on that system design. Example: X-vehicles are TRL 7, as are the demonstration projects planned in the New Millennium spacecraft program. TRL 8 Actual system completed and “flight qualified” through test and demonstration (ground or space) In almost all cases, this level is the end of true system development for most technology elements. Example: This would include design, development, testing, and evaluation through Theoretical First Unit (TFU) for a new reusable launch vehicle. This might include integration of new technology into an existing system. Example: Loading and testing successfully a new control algorithm into the onboard computer on Hubble Space Telescope while in orbit. TRL 9 Actual system “flight proven” through successful mission operations In almost all cases, the end of last “bug-fixing” aspects of true system development. For example, small fixes/changes to address problems found following launch (through “30 days” or some related date). This might include integration of new technology into an existing system (such as operating a new artificial intelligence tool into operational mission control at Johnson Space Center). This TRL does not include planned product improvement of ongoing or reusable systems. For example, a new engine for an existing reusable launch vehicle would not start at TRL 9: such technology upgrades would start over at the appropriate level in the TRL system. SOURCE: Adapted from John C. Mankins, Advanced Concepts Office, Office of Space Access and Technology, NASA, Technology Readiness Levels, A White Paper, April 6, 1995.