Dynamics of liquid sloshing in upright and inverted bladdered tanks

A system identification methodology was used to examine the dynamics of liquid sloshing in the upright and inverted bladdered hydrazine tanks of the Tracking and Data Relay Satellite, (TDRS) and to evaluate the effects of bladder stiffness on the sloshing parameters. Mechanical models of the two systems were developed using the numerical values derived from static stability tests and from slosh frequency response tests of a full-size model tank fitted with a prototype bladder. For the upright tank (liquid below the bladder) a modified conventional pendulum was used. In the inverted tank (liquid above the bladder) where sloshing is unconventional due to the highly nonsymmetrical orientation of the liquid held by the bladder, a mechanical model using an inverted pendulum which is able to undergo small oscillations as well as large reorientations was necessary. Both thrusting and low-gravity conditions are considered.