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Thrust control of hybrid rocket motors

Solid rocket motors and liquid rocket engines are the two primary forms of rocket propulsion. For example, GSLV has its first stage as solid motor, and all of its other propulsion systems, including the strap-ons are liquid engines.

A solid rocket motor consists of a casing with a solid propellent (fuel-oxidizer mixer) that burns to produce thrust. Liquid rocket engines store fuel and oxidizer as liquids which are mixed and burned in a combustion chamber and exhausted through a nozzle to produce thrust. Solid rocket motors are simple to manufacture and operate, but once ignited, cannot be controlled or stopped. Liquid rocket engines are complex, but the thrust produced can be controlled (including a complete shutdown and restart).

Although developed as early as solid and liquid rocket motors, a rocket propulsion technology that did not quite catch up with the other two is hybrid rocket motor which typically has a solid fuel and liquid/gaseous oxidizer.

Recently, hybrid rocket motors have gained increasing interest due to their unique characteristics that offer improved safety and reduced costs compared to traditional solid and liquid rocket motors. As a result, hybrid rocket motors are an area of active research and development, with the potential to revolutionize the field of rocket propulsion.

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Modeling small UAV propellers

Propeller selection is a crucial stage in airplane design. A poor selection can result in an inefficient design.

Designers of small UAVs are often faced with a hurdle in the propeller selection stage in preliminary design due to the lack of simple yet accurate models to estimate small propellers’ performance (thrust coefficient, power coefficient, and efficiency at various combinations of forward speeds and propeller RPMs). It might even seem impossible to have accurate propeller performance models as the performance depends on the propeller geometry (airfoil characteristics, chord length, radius, and linear pitch). And small propellers have complex geometries, the details of which are proprietary and not publically available.

Nonetheless, we could still have accurate yet simple propeller models. That is what Siddhardha and I showed in our work published recently in Aerospace Systems.

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