Component-Level Polymer Composite Spot Shielding for Radiation and Thermal Management in SmallSats

The increasing use of commercial-off-the-shelf (COTS) electronics in SmallSat platforms offers significant advantages in cost, performance, and development speed; however, radiation tolerance and thermal constraints often force conservative spacecraft-level shielding strategies. Bulk aluminum enclosures introduce substantial size, weight, and power (SWaP) penalties and frequently require entire subsystems to be over-shielded based on the most radiation-sensitive component. This paper presents a component-level radiation shielding approach for SmallSat electronics based on polymer composite spot shielding, evaluated as an alternative to full aluminum enclosures. The architecture combines a high-density metal-oxide polymer composite (MOPC) for ionizing radiation attenuation with a fiber-reinforced polymer composite (FRPC) layer engineered for in-plane thermal spreading. Together, the layers enable selective protection of radiation-sensitive components while redistributing localized heat without increasing shield thickness or electrical conductivity. Radiation attenuation measurements show that the MOPC layer achieves up to seven times higher mass attenuation efficiency than aluminum in low-energy photon regimes relevant to electron-dominated low Earth orbit environments. Environmental testing demonstrates that the composite system maintains mechanical integrity following total ionizing dose exposures up to 600 krad(Si), as well as extended thermal-vacuum cycling between −20 °C and 125 °C. Both composite layers satisfy NASA ASTM E595 outgassing requirements. System-level demonstrations using representative SmallSat electronics indicate that targeted spot shielding can reduce total radiation shielding mass by 70 – 85% compared with aluminum enclosure-based approaches, while simultaneously improving thermal behavior at the component level. These results highlight a practical pathway for reducing SWaP penalties and expanding the viable use of high-performance COTS electronics in future SmallSat missions.