Top Technical Challenges

The panels identified a number of challenges for each technology area that should be addressed for NASA to improve its capability to achieve its objectives. These top technical challenges were generated to provide some focus for technology development and to assist in the prioritization of the level 3 technologies. The challenges were developed to identify the general needs NASA has within each technology area, whereas the technologies themselves address how those needs will be met. Once the top technical challenges were identified, the panels then determined the relative importance of the challenges within each technology area to put them in priority order.

Descriptive Factors

The steering committee identified three descriptive factors that helped characterize each technology. While these factors were not primary in the determination of technology prioritization, they did assist in generating a better understanding of the current status or state of the art of the technology.

•   Technology Readiness Level (TRL): This factor describes the current state of advancement of the technology using NASA’s TRL scale. The TRL scale is defined in Table 2.1. It was determined that TRL should not be a basis for prioritizing technologies, as NASA should be investing across all levels of technology readiness. In assessing TRL levels, the panels were directed to evaluate the most promising developments that should receive attention. For example, electric propulsion systems are commonly used today, so as a whole, they would be assessed as TRL 9; however, the promising area of advancement of high power electric propulsion is less advanced, and thus 2.2.1 Electric Propulsion was assessed as TRL 3.

•   Tipping Point: The tipping point factor was used to determine if the technology was at a state such that a relatively small additional effort (compared to that which advanced the technology to its current state) could produce a significant advance in technology readiness that would justify increasing the priority associated with this technology.

•   NASA Capabilities: This factor captured how NASA research in this technology aligns with the expertise, capabilities, and facilities of NASA and/or other organizations cooperating with NASA in this area. It also indicated how much value NASA research in this technology would add to ongoing research by other organizations. This was not a primary consideration in assessing which technologies should be prioritized. Instead it was a factor in considering whether the technology should be developed by NASA, or if NASA should support other current efforts. The factor also addressed whether or not NASA should invest in improving its own capability for pursuing the high-priority technologies.

Evaluation Criteria

The steering committee identified three main criteria on which the technologies were to be judged for evaluation. The three criteria were benefit, alignment with NASA’s goals and objectives, and technical risk and challenge. Each of these is described in further detail below. For the latter two criteria, three further sub-criteria were created to assist in evaluating the technologies.

For each evaluated criterion or sub-criterion, a set of four (or in one case five) grades or bins were established, and the public and panel members were asked to determine what grade each technology should receive for that criterion. For consistency, a set of definitions were generated for each grade. The grading definitions were provided as guidelines to help the panel and steering committee members assign an appropriate range of grades necessary to prioritize the technologies in question. They were generated such that most technologies would be placed into one of the middle bins, while placement at the upper/lower bounds would need significant justification. The grades were assigned numeric scores on a non-linear scale (e.g., 0-1-3-9) to accentuate the spread of the summed



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