agency can threaten the viability and the continuation of multiagency efforts. In some cases, the resulting disruptions have led to a loss of experienced technology specialists. These losses impact NASA as well as the national aerospace community (NRC, 2009a, 2010a). Consequently, the need to restore technological capabilities across NASA, industry, and academia and to preserve stability and continuity in a core space technology program has become a national issue.

Evolutionary Improvements and Intermediate Goals

The successful development of game-changing technologies that lead to revolutionary capabilities applicable to a wide range of potential missions is a priority. In some cases, however, maintaining (or reestablishing) a technology base that produces a pipeline of evolutionary improvements over time can be important as well. For example, a steady stream of year-by-year, decade-by-decade improvements in solar-power systems has produced substantial improvements in the capabilities of solar-powered spacecraft and enables new classes of missions that could not have been conducted in past decades. In particular, the solar-powered Juno mission to Jupiter (launched on August 15, 2011) would not have been possible 10 to 20 years ago. In fact, Juno will be the first solar-powered spacecraft operating so far from the Sun. The state of the art in operational spacecraft solar arrays has evolved from the International Space Station (with panels that convert sunlight to electricity with 13 percent efficiency) to recent planetary spacecraft (with efficiencies of up to 20 percent) to the Juno spacecraft (with an efficiency of 26 percent).1 Looking ahead, new solar-electric propulsion missions are likely to become feasible as the photovoltaic power output per unit mass increases.

Conversely, some of the game-changing goals established in the draft roadmaps, such as the development of long-life rechargeable batteries with a power-to-mass ratio of 500 watt-hours per kilogram, are so advanced relative to the state of the art that no technological approach to this goal has been identified. In these situations, intermediate goals are required so that technology development can proceed with a reasonable likelihood of success.

Pursuing evolutionary improvements and setting intermediate goals have many benefits. These practices lead to time-phased applications, promote sustainable facilities and workforce within industry, and improve NASA’s ability to manage its resources and provide effective oversight.

Focus and Flexibility

Balance is needed between support of focused technological approaches and support of technologies that accommodate a wide range of destination and schedule options. When multiple technological approaches are available to address a specific, significant challenge, down-select points would allow the roadmaps to focus on whatever approaches show the most promise. However, when the ultimate application of a technology is uncertain, it is also important to use a flexible approach that can meet a range of likely future needs. For example, the draft Entry, Descent, and Landing (EDL) roadmap is focused largely on meeting the needs of a human mission to Mars. While this mission beneficially stresses and challenges the technology envelope in EDL, it would be prudent to ensure that the EDL technology under development is not tied too closely to a specific mission or destination. Technologies that enable a broad spectrum of future missions tend to be highly valued.

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1 Stated efficiencies are approximate values at beginning of life at one solar radius from the Sun.



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