NASA has a space power and energy storage technology roadmap. Power system composes 20-30 percent of the spacecraft mass.
The flaw in the NASA analysis is that they are focused on enabling space science missions using the technology roadmaps. They are not focused on developing a systematic plan changing the game in space. Spacex is working towards changing the game with reusable rockets that could lower costs to space by 100 times. NASA technology plans need to look at how space can be industrialized and removing technological barriers to seed systems that can allow space resources to be used to bootstrap what can be done in space.
In solar power generation, the emphasis is on the development of high efficiency cells, cells that can effectively operate in low intensity/low temperature (LILT) conditions (over 3 AU), cells and arrays that can operate for long periods at high temperatures (over 200°C), high specific power arrays (500-1000 W/kg), electrostatically-clean, radiation tolerant, dust tolerant, and durable, re-stowable/deployable arrays.
Fission Power System (FPS) efforts should focus on continued technology development for a 10 – 100 kWe “workhorse” system, development of a 500 – 5000 We fission system for use on advanced science missions and (potentially) some “flexible path” missions, and development of technologies to enable very high power (over 5 MWe) very low specific mass (less than 5 kg/kWe) space fission power. Work on low power (less than 100 kWe) fission systems should focus on researching and developing methods for integrating developed technologies into a highly useful, long-life power supply. Work on high power (over 100 kWe) fission systems should focus on advanced fuels and materials, and high temperature power conversion. FPS work will help enable affordable use of fission systems for missions not currently possible. These include missions requiring over 1000 We in hostile environments (e.g. heat, dust, radiation) or in regions where adequate sunlight is not available (e.g. outer planets, permanently shaded craters, high Martian latitudes, etc.). Technology work related to high power fission systems will help enable high performance nuclear electric propulsion for cargo and human missions to any destination desired.
Fusion power generation technology development should focus on ~ 50 MW aneutronic (p-11B) reactors, direct power conversion (e.g., traveling wave) from high energy charged particle beams, high voltage (~1 MV), high efficiency power management and distribution. Related propulsion work should focus on the development of plasma thrusters in which the plasma is heated directly by the high energy charged particle beam from an aneutronic fusion reactor.
Advanced space batteries focuses on the development of:
1) High specific energy and long life rechargeable batteries (500 Wh/kg, 5000 cycles),
2) High specific energy low temperature rechargeable batteries (200 Wh/kg, -100°C ),
3) high specific energy primary batteries (1000 Wh/kg) with low temperature operational capability (-160°C),
4) high temperature (450°C) primary and rechargeable batteries,
5) green battery materials and processes; and
6) advanced electronics to implement optimized charge methodologies to enhance life and safety.
For flywheel energy storage, development should focus on flywheel component miniaturization, nanotechnology-based rotors, magnetic bearings, reliability, and system development and demonstration.