An improved availability–dependability–capability (ADC) assessment framework is proposed for evaluating the mission effectiveness of solar-powered unmanned surface vehicles (USVs) under the coupled effects of hardware state transitions and stochastic energy supply. Within the availability and dependability dimensions, a joint state space is constructed that couples hardware condition states with battery state of charge (SOC). A Monte Carlo simulation driven by real solar irradiance data is used to derive the initial probability distribution and the dynamic state transition matrix. In the capability dimension, a hierarchical index system is established, and a hierarchical Criteria Importance Through Intercriteria Correlation (CRITIC) method is introduced to achieve objective weighting that accounts for inter-index correlations across multiple levels. Case-study calculations for a typical task profile yield a baseline mission effectiveness of approximately 0.661934. Comparative analysis reveals that neglecting the dynamic evolution of the energy state overestimates effectiveness by 38.94%, whereas ignoring random hardware failures produces a deviation of roughly 9.48%. These findings indicate that, while energy-state dynamics impose the dominant constraint on mission performance, the contribution of hardware degradation remains substantial. The concurrent influence of both limiting factors confirms the necessity of an assessment framework that explicitly integrates hardware and energy states, as developed in this work.

Small catamaran unmanned surface vessels (USVs) under wave action experience continuous roll and pitch, causing the solar irradiance on deck-mounted photovoltaic (PV) panels to vary and thereby affecting power output. The quantitative effect of wave-induced hull motion on PV power fluctuation and daily energy yield remains insufficiently quantified, and the separate contributions of roll and pitch remain unquantified. We developed a coupled PV power simulation model for a catamaran USV and applied it to six scenarios combining three sea states (Hs = 0.6, 1.0, and 1.5 m) with two wave directions (0°and 90°). Under the simulated clear-sky conditions, the attitude-induced daily energy loss rate did not exceed 1.3% across all scenarios and remained below 0.2% in following seas. Wave direction strongly controlled the power output characteristics: at a given sea state, the coefficient of variation of power under beam seas was 2.3–2.8 times that under following seas, and the maximum loss rate was 6.5 times the corresponding following-sea value. The realized motion contribution was wave--dependent, with roll dominating under beam seas and pitch dominating under following seas. Under the prescribed equal-amplitude motions, roll exhibited approximately five times the fluctuation sensitivity of pitch, whereas the dominant contribution under irregular waves depended on wave direction. Power fluctuation followed a diurnal pattern, stronger in the early morning and late afternoon and weaker around midday. These results suggest that roll mitigation may be prioritized in PV system design for catamaran USVs, while reducing beam-sea exposure may be considered in route planning to improve power stability.