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____________________ 2j SECURITY CLASSIFICATION AUTHORITY 3 DiSTRaSUTIONIAVA.ABIL1TY OF REPORT 2b DECLASSIFICATION iDOWNGRADING SCHEDULE Appi oved for public release; distribution unlimited. 4 PERFORMING ORGANIZATION REPORT NUMBER(S) 5 MONITORING ORGANIZATION REPORT NUMBER(S) BRL-mR-3609 6. AM OF PERFORMING ORGANIZATION 6b OFFICE SYMBOL ?a. NAME OF MONITORING ORGANIZATION us Airnly (it applicable) Ballistic Research Laboratory SLCBR-LF 6c ADDRESS (City State. and ZIP Code) 7b. ADDRESS (City. State, and ZIP Code)

The free-flight motion of an elastic missile is approximated with three bodies connected by two massless elastic cantilever beams. If the mass distribution of the three bodies is 1-2-1, the frequency of the symmetric oscillation of the outer bodies is within 5% of the classical frequency of the oscillation of a free-free beam. A second combined pitching antisymmetric flexing motion can occur with a frequency that is almost twice that of the symmetric flexing motion. As the beam stiffness is reduced, the symmetric flexing motion frequency approaches the rigid body aerodynamic zero-spin frequency, and the flight zero-spin aerodynamic frequency is considerably reduced. Moderate beam damping can cause dynamic instability for spins greater than the zero-spin aerodynamic frequency. Resonance mode amplification can occur when the spin is equal to the zero-spin aerodynamic frequency, but more importantly it can occur when the spin is equal to the two elastic flexing frequencies. Spin-yaw lock-in occurs at the lower elastic frequency.

The flidirgs in this report are not to be construed as an official Departnent of the Army position, unless so designated by other authorized documents.'~a not 0-ti t~t* kda m ven o r Mv CO . Ma -Pre