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Attitude Control and Fuel Slosh: Implications for NASAâ€s Constellation Program

Attitude dynamics is the modeling of spacecraft orientation based on the conservation of angular momentum, accounting for external torques. This investigation considers the effect of the sloshing motion in liquid fuel tanks, the corresponding torque it imparts on space vehicles, and the subsequent effect on spacecraft attitude. Depending on the mission, this liquid motion can impose significant vehicle design constraints. For NASA's Constellation Program, the baseline propellant budget for the Altair Lunar Lander includes a significant mass allocation to compensate for slosh disturbances. In this investigation, in order to alleviate these guidance and navigation design constraints, we consider methods to minimize this fluid motion by altering fluid properties. A two pronged approach is initiated. First, we will perform a series of experiments using an existing test bed at the Southwest Research Institute (SwRI) in San Antonio, TX. SwRI is internationally recognized for its fuel slosh expertise; their experiments and analysis have been used to validate launch vehicle and spacecraft designs.Second, we will create a computational test bed. Two essential components will be developed separately, using commercial software packages. A computational fluid dynamics problem solver (Fluent) will model surface disturbances and internal fluid motion in a partially filled liquid tank and compute the corresponding hydrodynamic forces exerted by the fluid on the interior of the tank surface. A separate program (Matlab Simulink) will simulate spacecraft attitude, implementing spacecraft control algorithms. Disturbance torques as characterized by the Fluent model will be an input to Matlab, providing a direct correlation between liquid motion and spacecraft attitude.

Location: Robert Glen Rapp Engineering Research Building (RRB) - 227

Audiences: Everyone Is Invited

Contact: Dan Erwin