NASA built a heat shield tile that was 94% empty space. You could pull it from a 2,200°F furnace and grab it with bare hands. LI-900 silica tiles conducted heat so poorly that the edges dropped to room temperature in seconds while the center still glowed at 2,200°F. The thermal conductivity was so low that heat couldn't travel through the material fast enough to reach your fingers. You weren't grabbing a hot object. You were grabbing air that happened to be shaped like a brick. The…