Performance degradation mechanism and power evolution model of radioisotope thermoelectric generator

Abstract

Radioisotope thermoelectric generator (RTG) is an indispensable long-duration power system for space exploration and terrestrial applications. However, its long-term output performance is dominated by complex time-dependent coupling of radioisotope decay, thermoelectric degradation and aerogel insulation aging, making accurate prediction highly challenging. Conventional experimental evaluations are prohibitively time-consuming, while data-driven methods are severely constrained by the scarcity of high-quality RTG operational data. To address this limitation, a physics-driven output power prediction framework is developed by combining long-term component aging tests and nuclear-thermal-electric multiphysics simulations. Experimental results indicate that both TE modules and aerogel insulation follow a logarithmic degradation behavior. Multiphysics simulations quantitatively decouple the performance degradation contributions of individual components, revealing that radioisotope decay reduces thermal inventory and reconstructs the internal temperature field, which further induces secondary TE efficiency decrease. Crucially, the power evolution is found to transition from an early-stage TE-aging-controlled logarithmic regime to a late-stage radioisotope-decay-controlled exponential regime. Based on this degradation-regime transition, a segmented physics-based power evolution model is proposed. Comparisons with multi-mission RTG (MMRTG) prototype measurements and multi-parameter sensitivity analyses confirm the general two-stage degradation trend of RTG output power. This work provides a reliable power prediction methodology and clarifies the underlying coupled degradation physics of RTG.

The authors' abstract, as published at the source. Applied Thermal Engineering, 2026 · DOI ↗