High Energy Density Radiation Tolerant Capacitors for Cryogenic Temperature Applications

The Phase II proposal addresses the development of advance high energy density capacitors, for use in Power Processing Units (PPUs) of spacecraft, probes and landers, that are designed to operate in extreme temperature environments, with particular focus on cryogenic temperatures. Operating capacitors at cryogenic temperature presents unique challenges that need to be addressed to ensure a high level of reliability and performance. Space missions to planetary bodies that are distant from the sun, as well as lunar regions that are permanently shadowed, require electrical components with low temperature survivability and predictable and stable functionality at temperatures in the range of +125C to -240C. Furthermore, resistance to radiation exposure is a key requirement to reduce the added weight and volume of radiation shielding. The Phase I development demonstrated that NanoLam capacitor elementshave excellent parametric stability from a cryogenic temperature of 5oK (liquid helium) to 160oC. Comparison with state-of-the-art technologies shows that the NanoLamTM capacitors, have superior extreme temperature performance and multiple times higher energy density (J/cc) and specific energy (J/gr). The Phase II development is designed to produce and evaluate complete capacitors that comprise stacks of capacitor elements connected in parallel and packaged in a high temperature polymer box. The packaged parts will be tested using a series of environmental, electrical and mechanical tests. These will include, accelerated life tests at different conditions of voltage, temperature, vacuum and gamma radiation, to simulate operating conditions at different environments, and to facilitate the development a life-law to predict long term performance. Components will be supplied to NASA personnel for further tests and integration into low voltage advance controller units of dynamic power conversion systems, and high voltage PPUs for Hull Ion Thruster propulsion systems. Deep space missions and future lunar missions to shadowed areas of the moon, require electrical components with predictable and stable functionality at temperatures in the range of -240οC to at least +125οC. Two of the largest and most critical components in most NASA Power Processing Units (PPUs) are energy buffer and DC-link capacitors used to minimize ripple current, voltage fluctuations, and transient suppression. The proposed development will build upon the successful evaluation of a disruptive, solid-state, NanoLam™ polymer capacitor technology.  NanoLam™ capacitors are self-healing, they have stable capacitance, dissipation factor, and breakdown voltage from -268oC to at least 140oC, and comprise a nanothick polymer dielectric.  As a result, the capacitors have superior breakdown strength and high resistance to radiation exposure. NanoLamTM capacitors have an order of magnitude higher energy density that state-of-the-art capacitors that may be used in cryogenic applications, with superior performance at high temperatures, and do not require protective radiation shields. The primary objective of the proposed Phase II program is to complete the development of both the 80V and 480V DC-link capacitors that cover most of the current PPU requirements for spacecraft, probes, and landers.  Specific objectives include optimization of the 85mF/80V NanoLamTM element design and the 4mF/480V element that will be used to produce respectively 750mF/80 and 50mF/480V packaged DC-link capacitors; design and fabrication of high-temperature liquid crystal boxes to package the two capacitor designs; performance of a series of short term and long-term Highly Accelerated Life Tests (HALT), under various conditions of voltage, temperature, humidity, as well as thermal cycle and thermal shock tests; taking advantage of this development, expand the NanoLamTM capacitor market to 48V applications for inverters of hybrid vehicles where the NanoLamTM capacitors have superior dielectric performance and energy density, over aluminum electrolytics and multilayer ceramics. The deliverables will include: capacitor elements, packaged capacitors, and the final Phase II report. At least 100-200 capacitors elements and packaged capacitors will be delivered to Alexander Teverovsky of NASA-GSFC.  These parts will be delivered throughout the Phase II development for round-robin tests, as well as measurement of the performance of NanoLamTM capacitors in the presence of radiation. 

Potential NASA applications include Power Processing Units (PPUs) for photovoltaic arrays, 20V and 300V for electric propulsion, such as Hall Ion thruster systems. A more stringent application is PPUs of Dynamic Radioisotope Power Systems (DRPS), designed for future deep space missions such as the Saturn moons and planned missions to the shadowed side of the moon. Capacitors used in DRPS spacecraft, landers and probes need to operate in cryogenic temperature environments as well as in the presence of radiation both internal and external. NanoLamTM capacitors have a wide range of applications, that includes DC-link capacitors for inverters of hybrid and electric vehicles, medical instrumentation such as defibrillators both implantable and external, PPUs for aerospace applications, DOD and DOE applications that require capacitors with unique performance characteristics, and industrial applications such as power supplies.

This is early/mid-stage (TRL 5) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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