Pogo is defined as an unstable interaction between a launch vehicle structural mode and a propulsion system mode. It is usually characterized by a “football” shaped acceleration curve which shows an increasing acceleration for a period of time (negatively damped system), sometimes followed by a period of limit cycle acceleration and then typically followed by a period of decreasing acceleration. Early in flight, while the vehicle mass is at peak value, the vehicle mass-stiffness distribution leads to a relatively low structural mode frequency. As flight progresses, the vehicle quickly loses mass (burning propellant) with very little change in vehicle stiffness. This typically leads to an increase in vehicle structural mode frequency. For this reason, a pogo event is usually short lived, but can still be damaging to payload or the vehicle depending on the acceleration levels achieved during the unstable interaction.
This webinar will provide an overview of the pogo stability challenge, a historical view of the pogo phenomenon, guidance on the performance a pogo stability analyses, and insight into the most common fix for the typical pogo interaction.