Analysis of Re-Entry Vehicle Behavior during Boundary-Layer Transition
Analysis of re-entry vehicle (RV) behavior during the period of boundary-laye r transition is performed using the full three degree of rotational freedom plane fixed equations of motion without limitations of linearization s or quasi-steady restrictions. Flight data for a number of RVs, including ablative and nonablative afterbodies, showed large divergencies in the magnitude and sense of the precession characteristics. Associated with the large excursions in the precession behavior are significant changes in the character of the motion, i.e., the ratio of maximum to minimum angle of attack. Three possible sources of these anomalies were investigated: unstable damping;- static "out-of-plane" moments; "in-plane" static moment asymmetries. Analyses show the unstable damping postulation is highly improbable; simulations employing "out-of-plane" static moments adequately describe the majority of flight results. However, significant discrepancies are noted for two flights. A rapidly varying body fixed moment source is described which provides reasonable simulations of the precession divergencies and highly transient angle of attack behavior.