A passive thermal protection system that overcomes the disadvantages of the polyurethane "water wall" includes a fiberformed ceramic insulation, a plurality of electrodes embedded in the insulation to define a wick panel, and a gelled ceramic sol in the wick panel. The system can be prepared by introducing the sol into the wick panel with its subsequent gelling by applying a direct current across the electrodes. Cooling water is held in the gelled sol to provide passive cooling, yet the system easily achieves even distribution of the water (even when subject to accelerations) without the use of pre-gelled or viscous reagents.