NECESSARY CONDITIONS FOR SUSTAINED REENTRY ROLL RESONANCE.

Using the method of near-identity transformations, the author studies a model of reentry roll resonance, a situation encountered when an almost axially symmetric vehicle reenters the earth's atmosphere. This method allows him to extend previous results for the case of sustained resonance, when roll buildup occurs. In particular, he gives necessary conditions (in terms of the slowly varying pitch or yaw frequency) both for entrainment to sustained resonance and for sustained resonance to continue and discusses their implications. In addition, he makes a conjecture concerning sufficient conditions for sustained resonance.