Development of closed loop roll control for magnetic balance systems

This research was undertaken with the goal of demonstrating closed loop control of the roll degree of freedom on the NASA prototype magnetic suspension and balance system at the MIT Aerophysics Laboratory, thus, showing feasibility for a roll control system for any large magnetic balance system which might be built in the future. During the research under this grant, study was directed toward the several areas of torque generation, position sensing, model construction and control system design. These effects were then integrated to produce successful closed loop operation of the analogue roll control system. This experience indicated the desirability of microprocessor control for the angular degrees of freedom

Numerical Modeling of GOX/HTPB Hybrid Rocket Flowfields and Comparison with Experiments

Numerical simulations of the flowfield in a GOX/HTPB hybrid rocket engine are carried out with a Reynolds averaged Navier-Stokes solver including detailed gas surface interaction modeling based on surface mass and energy balances. Fuel pyrolysis is modeled via finite-rate Arrhenius kinetics. A simplified two-step global reaction mechanism is considered for the gas-phase chemistry to model the combustion of 1,3-butadiene in oxygen. Results are compared with firing test data from a lab-scale hybrid rocket in which gaseous oxygen is fed into axisymmetric HTPB cylindrical grains through an axial conical subsonic nozzle. With the oxidizer fed by this kind of injector, which generates nonuniform conditions at the entrance of the fuel port, the fuel regression rate is shown to increase several times with respect to the case of homogeneous injection of the oxidizer through all the grain port area, in agreement with the experimental findings. The spatial distribution of the regression rate is substantially different from the one expected in a turbulent developing flow, because of the presence of a strong recirculation zone. Numerical simulations, yet not capturing the absolute regression rate values, are fairly able to predict the main ballistic features, i.e. the regression rate weaker dependence on the mass flux, the influence of port diameter and the pressure evolution over time