Abstract: The cool insulator incorporates a water gel coolant and poly-p-ethylene tphthalamide fibers (Kevlar) in an elastomeric rubber binder selected from the group consisting of silicon rubber, ethylene-propylene-diene-monomer, polybutadiene, and polyisoprene. The fiber provides erosion resistance required for long motor burning periods. This insulation includes a submicroscopic particulate water source with high temperature water release properties. The submicroscopic particulate water source is in the form of a flowable solid when formulated and in a weight percent amount from about 10 to about 20. The preferred water source is submicroscopic particulate silica containing over 11.times.10.sup.15 particles per gram and has a surface area of about 200 square meters per gram. The submicroscopic particulate silica is known as "dry water" and specifically described by its method of preparation in commonly assigned U.S. Pat. No. 4,008,170.