Calculated Aeroelastic Bending of a Sounding Rocket Based on Flight Data

During a series of Nike-Tomahawk sounding rocket flights, large extra-atmospheric coning angles were observed which were not predicted by preflight calculations. The most probable causes were concluded to be Magnus forces, aeroelastic bending, and/or lee-side boundarylayer separation. This paper is a report of an investigation of the aeroelastic behavior of one of these flights. An analysis was made which assumed that the missile consisted of two rigid bodies (payload and motor) hinged at their interface. Three-degree-of-freedom moment equations were written for each of the sections that were coupled by a bending moment at the hinge point. Sufficient data were available from flight, wind-tunnel, and laboratory tests to calculate the coning angles of each section. The maximum angular difference between the payload and the motor, immediately following second-stage burnout, was calculated to be -f-0. Flexural strengths obtained from bending tests accounted for the angular difference except for a 4-sec period near burnout. The additional bending is attributed to the opening of the payload separation joint caused by the rapid aerodynamic heating and sudden loss of acceleration at second-stage burnout.