Flight-dynamics instability induced by heat-shield ablation lag phenomenon

Flight-dynamics instabilities resulting from the ablation-lag phenomenon have been investigated. Ablation lag occurs on spin-stabilized missiles or reentry vehicles that use ablative materials for thermal protection. The present approach includes the coupling and combined effects of reentry vehicle surface recession, heat conduction into the vehicle skin, reentry vehicle spin rate, and angle of attack. Thyson's analysis on the magnitude of ablation lag is used in the present analysis. The present model predicts the advent of reentry-vehicle flight instability during reentry and the eventual self-curing of the divergence. The thermal performance of several heat-shield materials and the propensity of the materials to induce flight instability are briefly assessed. Numerical examples are given to illustrate the ablation-lag phenomenon.