Mass migration influence on the restart characteristics of a sodium heat pipe

• Experimentally investigated the restart characteristics after mass migration. • Mass migration led to wick blockage and reduced effective heat transfer length. • The Argon natural convection enhanced the heat transfer performance after restart. • The successful restart proved the application feasibility for spacecraft systems. • Two feasible strategies were proposed to mitigate mass migration. Sodium heat pipes are critical for spacecraft thermal management but suffer from mass migration—a phenomenon where sodium freezes in the condenser section during dormancy, degrading heat transfer performance. This study presents the first experimental investigation into the restart characteristics of sodium heat pipes after mass migration. We successfully replicated mass migration, observing temperature gradients exceeding 500 °C and loss of isothermal behavior. Crucially, we demonstrate that restart is achievable and that adjusting the condenser's argon gas gap significantly enhances performance: Heating power increased by 29 % (4.02 kW to 5.18 kW) with maintained isothermal properties (Δ T ≈ 15 °C). Mass migration reduces effective heat transfer length by blocking the wick, but strategic gas-gap optimization mitigates this effect. These findings offer potential solutions for reliable thermal control in deep-space missions.