Circuit-level techniques for mitigating radiation-induced degradation of commercial microelectronics in space
Keywords: Materials Science and Engineering.

The survivability of microelectronic devices in harsh radiation environments has a profound impact on spacecraft reliability and is a limiting factor in our species becoming a multi-planet civilization. Despite recent sociotechnical advancements providing more access to space, the radiation-induced degradation of modern electronic systems continues to dictate overall mission scope, cost, and lifetime. The paradigm of one-off engineering feats comprised of bespoke radiation-hardened circuits no longer fits the increasingly competitive landscape of satellite and small-spacecraft development. To bridge this divide, this thesis describes the development of non-invasive circuit-level techniques for improving the reliability of commercial electronics in space in order to to better equip future spacecraft with the capabilities afforded by modern consumer microelectronics. This dissertation documents the development of two techniques for improving component-level and system-level reliability of commercial electronics in ionizing radiation. The first technique exploits the periodic nature of many space radiation environments to achieve as much as 300% improvement in device lifetime by modulating device power during periods of intense irradiation. Through simulation and subsequent experimental testing using a Cs-137 gamma source, this "dynamic biasing" technique lays the foundation for providing electronic systems a means of intelligently responding to the real-time radiation environment without additional shielding or modifications to individual semiconductor architectures. Next, the design and verification of a second technique is presented which enables improved system-level reliability of commercial electronics by mitigating the single-point failure mode inherent to popular serial communication protocols. A simple external circuit is proposed and evaluated for its effectiveness in digitally isolating one or more devices in the event of failure. We show through simulation and hardware implementation that these isolation schemes are effective at preventing bus-wide failure in the event of peripheral device malfunction for two serial bus protocols, Inter-Integrated Circuit (I2C) and Serial Peripheral Interface (SPI), without requiring additional I/O or processing overhead. The isolation circuits were integrated into the avionics hardware of three small-satellite spacecraft and their operation validated at communication speeds of 400 kHz (fast-mode) for I2C and 5 MHz for SPI before, during, and after inducing device failure on the bus. By eliminating the single-point failure mode of I2C and SPI protocols, the developed isolation techniques were found to significantly reduce the likelihood of system failure for the satellite mission. The last portion of this thesis details the real-world application of the previously described dynamic biasing and serial bus isolation techniques, culminating in an open-source spacecraft avionics platform and two successful on-orbit satellite missions. The design and operating principles of our open-source hardware and software platform for spacecraft development, called PyCubed, is presented and its widespread adoption across the small-satellite community discussed. Application of the PyCubed framework is then detailed in the design and operation of the 2019 "KickSat-2" CubeSat mission which successfully dispensing 105 "femtosatellites, " each weighing less than 100 grams, in low-Earth orbit at an altitude of 300 km. Finally, details and on-orbit data from the 2021 "V-R3x" mission are presented, which involved the development and operation of three 1U CubeSats for coordinated networking and technology demonstrations in low-Earth orbit at an altitude of 500 km