Solution to the Delta vehicle second stage pogo problem

A discussion of the pogo phenomenon observed on the Delta launch vehicle second stage is presented. The pressure-fed engine and the high frequency of the oscillation (125 Hz) required unique analysis and extensive testing to support analysis detail. In addition, the need to continue a one vehicle per month launch rate required both an immediate interim and a timely long-term solution to the problem. The development and implementation of a program involving analysis, ground test, and flight instrumentation is described. An analytical model was developed and used to investigate both structural and propulsion system modifications. The factors which influenced the final suppression system selection, the analytical predictions for that system, and flight data which validate that system's effectiveness are presented.