2025 SBIR Phase I Research Subtopic Pre-Release S13.06 Amendment.pdf

Fiscal Year 2025 SBIR Phase I Research Subtopics

S13.06: Dynamic Power Conversion (SBIR)

Related Subtopic Pointers: S13.03, S16.05, Z-ENABLE.01

Lead Center: GRC

Participating Center(s): N/A

Subtopic Introduction:

NASA is considering high efficiency dynamic power conversion technologies for use in Radioisotope Power

Systems (RPS) to power science missions for the Moon and other solar system bodies of interest. This is mapped by

NASA SMD's strategic technology investment plan for space power and energy storage enabling higher power systems using the same amount of fuel, enabling more spacecraft to support a single mission, or requiring less fuel for offered power levels. Technologies are sought maturing high efficiency and robust dynamic power conversion integrated with a RPS power source that provides thermal-to-electric power conversion with low mass, long life, and high reliability for use on RPS powered space probes, landers, and rovers.

Scope Title: High Efficiency Power Conversion Technologies

Scope Description:

High efficiency RPS are sought across a wide range of power, from 1 to 100 watts for RPS applications. Lower power conversion could convert heat from one or more small isotope heat sources to a few watts for powering battery chargers or sensors on small science stations or distributed networks. Higher power conversion could convert hundreds to thousands of thermal watts made available from one or more large isotope heat sources, such as the

General Purpose Heat Source (GPHS) or an alternative isotope heat source, to hundreds of watts for powering large orbiting or surface spacecraft. Waste heat could also be removed from the power convertor for keeping spacecraft components warm enough to survive very cold environments. Proposals are sought that address the following technical challenges:

1. Efficient, robust power conversion:

• Free-Piston Stirling cycle convertors capable of long life (17 years) and high efficiency (>30%) that are robust and reliable for 100-class generator concepts. There is an interest in lower power convertors (20 to 40 watts electrical output) to support small RPS concepts.

• High power density convertor alternator designs are sought to survive combined temperature and radiation environments, with robust organic and magnet materials. Alternators should be able to survive for long periods (17 years) at elevated temperatures and radiation levels (over 200 °C and 2x1014 n/cm2

+ 1x103 krad).

• Thermal management technologies, such as heat pipes, that are directly coupled to Stirling heater heads and robust high-temperature multi-layer insulation (MLI) designs for insulating an isotope source operating at elevated temperatures (900 to 1000 °C).

2. Radiation-hardened electronic controllers and power processing:

• Electronic controller hardware for Stirling-based systems with a credible path to flight and able to control one or more dynamic convertors. There is a special interest in controller architectures able to manage multiple convertors and controllers able to control a single convertor and an active balancer without relying on feedback from vulnerable short-lived sensors.

• Increasing the radiation tolerance of electronic components found in controllers and accompanying power processing systems to values greater than 5x1011 n/cm2 + 3x102 krad + 40 MeV-cm2/mg (linear energy transfer). Higher tolerance will enable a reduction in shielding mass and is strongly desired.

• Increasing specific power density (w/kg) of controllers with high density capacitive and magnetic filtering and buffering.

• Sensors and hardware systems integrated with innovative control algorithms and data processing to enable robust, autonomous operation of Stirling-based systems.

Please note that the following areas are excluded from S13.06 this year:

• Static power conversion technologies (offerors are suggested to consider Z-ENABLE.01 "Enabling

Power and Thermal Technologies").

Expected TRL or TRL Range at completion of the Project: 2 to 5

Primary Technology Taxonomy:

• Level 1: TX 03 Aerospace Power and Energy Storage

• Level 2: TX 03.1 Power Generation and Energy Conservation

Desired Deliverables of Phase I and Phase II:

• Research

• Analysis

• Prototype

• Hardware

• Software

Desired Deliverables Description:

• Phase I: Results of studies, modeling, and/or component testing to demonstrate basic feasibility.

• Phase II: Prototype hardware that has demonstrated basic functionality in a laboratory environment, the appropriate research and analysis used to develop the hardware, and maturation options for flight designs. Phase II deliverables should also include/delineate any further work that would be required to bring the system to full operational and/or commercial use.

State of the Art and Critical Gaps:

RPS are critical for long-duration NASA missions to dark, dusty, and harsh environments. There have been twelve major RPS powered robotic spacecraft deployed over the past 51 years that have successfully explored our solar system, including: Pioneer (2), Viking (2), Voyager (2), Galileo, Ulysses, Cassini, New Horizons, Curiosity, and

Perseverance. Those power systems used thermoelectric generators with high reliability, but low efficiency, where solar power wasn’t practical. Past RPS contain Plutonium-238; however, future RPS could use alternatives, like

Americium-241. Current work is focused on maturing high efficiency dynamic power conversion technologies that would be integrated with a radioisotope heat source to provide thermal-to-electric power conversion.

Dynamic energy conversion offers long-lived generators for spacecraft power with significantly higher efficiency, up to a factor of four. New high efficiency convertors can enable robust, high-temperature and radiation-tolerant designs. In addition to 100 watt-class convertors, advances in much smaller and lower power dynamic power convertors are sought that would convert lower amounts of heat for applications such as distributed sensor networks, small spacecraft, and other systems that take advantage of lower power electronics for the exploration of surface phenomenon on the moon and other bodies of interest.

This scope addresses shortfalls identified in the Civil Space Shortfall Ranking including:

• [Ranked 1st] ID 1618: Survive and operate through the lunar night

• [Ranked 21st] ID 1596: High Power Energy Generation on Moon and Mars Surfaces

• [Ranked 93rd] ID 1597: Power for Non-Solar-Illuminated Small Systems

• [Ranked 35th] ID 1390: Power and Data Transfer in Dusty Environments

Relevance / Science Traceability:

Highly efficient Stirling RPS could enable long-lived robotic science missions to other worlds identified in the

Decadal Survey "Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032"

[Ref. 5]. As a part of planned science missions, highly efficient Stirling power conversion can provide power and heat on landers and rovers so they may operate in dark, dusty locations throughout the solar system. NASA's RPS

Program Office is developing highly efficient RPS technologies for more efficient use of precious nuclear fuel on future RPS powered missions.

References:

1. "Radioisotope Power Systems," National Aeronautics and Space Administration:

https://rps.nasa.gov/about-rps/overview/

2. Oriti, S.; Wilson, S., "Dynamic Power Convertor Development for Radioisotope Power Systems at

NASA Glenn Research Center," AIAA Propulsion and Energy Forum. 2018:

https://arc.aiaa.org/doi/pdf/10.2514/6.2018-4498

3. Wilson, S. D.; Schifer, N. A.; Geng, S. M; Reid, T. V.; Penswick, L. B.; Casciani, M. R., "NASA Low

Power Stirling Convertor for Small Landers, Probes, and Rovers Operating in Darkness," AIAA

Propulsion and Energy Forum. 2018: https://arc.aiaa.org/doi/pdf/10.2514/6.2018-4499

4. Wong, W. W.; Wilson, S.; Collins, J., Wilson, K., "Advanced Stirling Convertor (ASC) Technology

Maturation," AIAA Propulsion and Energy Forum, 2015: https://arc.aiaa.org/doi/pdf/10.2514/6.2015-

5. “Origins, Worlds, and Life: Planetary Science and Astrobiology in the Next Decade,” National

Academics: https://nap.nationalacademies.org/catalog/27209/origins-worlds-and-life-planetary-science-and-astrobiology-in-the

6. "Civil Space Shortfalls," National Aeronautics and Space Administration:

https://www.nasa.gov/spacetechpriorities https://rps.nasa.gov/about-rps/overview/ https://arc.aiaa.org/doi/pdf/10.2514/6.2018-4498 https://arc.aiaa.org/doi/pdf/10.2514/6.2018-4499 https://arc.aiaa.org/doi/pdf/10.2514/6.2015-3806 https://arc.aiaa.org/doi/pdf/10.2514/6.2015-3806 https://nap.nationalacademies.org/catalog/27209/origins-worlds-and-life-planetary-science-and-astrobiology-in-the https://nap.nationalacademies.org/catalog/27209/origins-worlds-and-life-planetary-science-and-astrobiology-in-the https://www.nasa.gov/spacetechpriorities