Autophage Engines: Toward a Throttleable Solid Motor

摘要

This paper describes the instrumented test firing of a rocket that seeks to combine the throttleability of a liquid-fueled engine with the simplicity of a solid motor. The concept is that a differentiated fuel and oxidizer rod is forced into a vaporization unit where its constituents transition into separate propellant gases, which are then mixed in a combustion chamber. The vaporization unit is heated by the combustion, and the throttle setting is adjusted by changing the force used to drive the solid propellant rod into the vaporizer, which naturally influences the propellant feed rate. In experiments using a solid propellant rod consisting of polypropylene fuel and a 1:1.5 mixture of NH4ClO4 and NH4NO3 oxidizer, operations have been sustained for around 60s. During testing, using propellant feed forces of between 250 and 900 N, propellant feed rates of between 100 and 300 mm/min have been achieved, which are in turn correlated to chamber pressures of between approximately 300 and 700 kPa. These correlated cycles of control input (the feed force), throttle response (the propellant feed rate), and implied thrust (the chamber pressure) demonstrate, for the first time, a simple solid rocket that can be throttled in real time.