Modeling and Parameter Estimation of Spacecraft Lateral Fuel Slosh
Author: Yadira Rodriguez Chatman Title: Modeling and Parameter Estimation of Spacecraft Lateral Fuel Slosh Institution: Embry-Riddle Aeronautical University Degree: Master of Science in Aerospace Engineering Year: 2008 Predicting the effect of fuel slosh on spacecraft and launch vehicle attitude control systems has been a very important and challenging task and has been the subject of considerable research over the past years. Analytic determination of the slosh analog parameters has been met with mixed success and is made more difficult by the introduction of propellant management devices such as elastomeric diaphragms. The experimental set-up in this research incorporates a diaphragm in a simulated spacecraft fuel tank subjected to lateral slosh behavior. This research focuses on the parameter estimation of a SimMechanics model of the simulated spacecraft propellant tank with diaphragms using lateral fuel slosh experiment data. An experimental investigation was conducted to determine and measure the slosh forces response of free surface slosh and diaphragms in an eight inch diameter spherical tank. The lateral slosh testing consisted of the tank assembly partially filled with different liquids, for other tests, diaphragms were incorporated into the tank. The experiment results from different testing conditions were compared for estimation of unknown parameter characteristics that include the pendulum model stiffness constants and damping coefficients.
Modeling of Free-Surface Fuel Slosh in Microgravity for Off-Axis Spacecraft Propellant Tanks
Liquid propellants generate surface waves within partially filled propellant tanks of spinning space systems and cause energy dissipation. Propellant slosh induces linear nutation growth and results in gyroscopic instability and exponential precession. Recent missions, such as the second launch of SpaceX’s Falcon 1 in 2007, substantiate that accurately modeling slosh dynamics is critical for mission success; Falcon 1 oscillated out of control shortly after stage separation due to fuel slosh. A MATLAB SimMechanics fuel slosh model can be used to estimate slosh parameters and predict dynamic effects on dependent systems. The rate at which nutation grows is defined as the Nutation Time Constant (NTC). Comparative flight data was acquired by spinning a mock spacecraft with partially filled propellant tanks in a microgravity environment. Empirical and simulated NTC’s are compared to validate a SimMechanics fuel slosh model.
A study of the local tissue reactions in man to cortisone and compound F. VI. Histopathological studies of the local effect of compound F in normal and pathologic skin of man.
After our previous negative studies (1) of the local effect of cortisone acetate in the skin of man, a year ago, a parallel study of 17-hydroxycorticosterone-21-acetate, Compound F, was outlined. Theoretically, Compound F should be the active steroid. It was so suggested by Rothman (2), that in all probability Compound F and not cortisone would be active locally in the skin of man.