Technology Readiness Levels
NASA employs a technology readiness level (TRL) process to assess the flight readiness of a given technology under development on the basis of its level of maturity (see Appendix D in this report). The TRL is rated on a scale of 1 to 9 depending on the degree of concept development, analytic and empirical validation, and ultimately, flight validation (see Figure 3.1.1).
TRL 9: Actual system “flight proven” through successful mission operations
TRL 8: Actual system completed and “flight qualified” through test and demonstration (ground or space)
TRL 7: System prototype demonstration in a space environment
TRL 6: System/subsystem model or prototype demonstration in a relevant environment (ground or space)
TRL 5: Component and/or breadboard validation in relevant environment
TRL 4: Component and/or breadboard validation in laboratory environment
TRL 3: Analytical and experimental critical formula and/or characteristic proof-of-concept
TRL 2: Technology concept and/or application formulated
TRL 1: Basic principle observed and reported
SOURCE: NASA In-Space Propulsion Web site at http://www.grc.nasa.gov/WWW/InSpace/when.html.
must choose carefully how and what to fund so as to expand its mission capabilities. The importance of a tightly focused technology program to support future advanced missions such as those that would be conducted using the Constellation System led the committee to recommend that NASA develop a comprehensive strategic plan for advanced propulsion system development (see the section below entitled “Propulsion System Technology Summary”).
The overall technology requirements for the mission concepts studied in this report are summarized in Table 3.1. The technology readiness levels (TRLs) used by NASA to assess the flight readiness of a given technology are listed in Box 3.1. For a fuller description of these TRLs, see Appendix D.