With the advances in the field of high speed and low altitude missiles, thermal shock resistance of IR material domes becomes more critical than ever. In such applications the friction between the dome and the air gives rise to severe aerothermal heating, that can elevate the temperature of the dome well above 250°C in a matter of seconds. Designing the ZnS dome's thickness is a result of a tradeoff between several constraints. Rain Shock and hail impact resistance requirements pull us towards higher thickness. On the other hand, thermal shock resistance favors thinners thicknesses. We present here a recent research of the thermal shock resistance of Rafael made CVD ZnS domes. The method of heating chosen was quenching in hot oil. Ten domes of each type were immersed in mildly stirred oil, heated to consecutively elevated temperatures between 100°C-300°C, and let to cool to room temperature after each step. According to the literature, mildly stirred oil has a heat transfer coefficient in the range of h = 250 ~ 1000 W/m2K, hence for a 4 mm thick ZnS dome, we reach a Biot number between β = 0.06 ~ 0.24 . This is well in the range that is representative of missile dome aerothermal heating, i.e. β = 0.01 ~ 5 . All twenty domes survived the immersions without shattering. This implies that the material properties and process parameters of the Rafael dome production line, exhibits high resistance to thermal shock. Further tests are under way.
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