Published online by Cambridge University Press: 04 July 2016
Ablative cooling is a proven, reliable thermal protection method for entry vehicles with zero to moderate hypersonic lift/drag ratio. Unfortunately, this method becomes impractical for vehicles with lift/drag ratios greater than about 1-0, because of the severe weight penalties which accrue from long glide times and the large surface areas associated with high LID configurations. Moreover, to obtain high hypersonic LID it is necessary to minimise blunting of the nose and leading edges, a condition certainly present when ablation is used to protect the leading edges. This situation is commonly handled by the design of a high temperature radiation cooled structure of refractory metal with supplemental insulative protection in the stagnation region along the leading edges and in areas of local heating such as those resulting from shock impingement. This insulation may take the form of a high temperature foamed ceramic such as zirconia foam.