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Space Station Freedom may be characterized as a large, flexible, free-floating structure with high modal density and low natural frequencies. These structural features allow for control/structure interaction problems to arise that may influence the SSF design or on-orbit operations. One such control/structure interaction problem is the effect of the Reaction Control System thrusters acting on the central truss structure. The central truss structure is the skeleton of SSF and supports all other hardware items on-orbit. The RCS thrusters are used for station reboost and attitude control maneuvers. Both the RCS and the central truss structure are the responsibility of the McDonnell Douglas Space Systems Company under contract to NASA through the Johnson Space Center. The Permanently Manned Configuration of SSF may easily be excited to resonance by on-off pulsing of the RCS thrusters.