Multi-phase thermal control systems, evaporators, variable porous wick elements, heat transfer structures, and methods for their production are provided. Two-phase evaporators for use in such multi-phase thermal control systems are also provided. Two-phase evaporators incorporate a vapor plate body having there three major layers: a vapor channel network, a wick, and a liquid channel. The vapor channel network comprises a plurality of extrusions (e.g., vapor pillars) and associated channels (e.g., vapor channels) configured to allow a vapor to flow therethrough. The wick comprises a porous body configured to be disposed between the vapor channel network of and the liquid flow reservoir.