Developed in 1933, Engine 09 successfully propelled the first Soviet rocket burning liquid oxidizer on August 17, 1933.
A rare museum replica of the 09 engine, showing holes for injection of the benzene gel into the combustion chamber.
The engine of Vehicle 09 was intended to burn an unusual gel-like fuel made of benzene mixed with rosin. Around one kilogram of the semi-solid substance was loaded into a special cavity between the main wall of the combustion chamber and a special central pipe with holes.
The fuel would burn in layers from the central pipe toward the periphery of the chamber, thus protecting the vulnerable main wall of the chamber from melting almost until the very end of the combustion process. The unusual design allowed to avoid the construction of a fuel tank and its fuel-supply mechanism.
In the meantime, the liquid oxygen serving as oxidizer for the fuel would be forced into the combustion chamber by the pressure of its own vaporization.
The system became known as a hybrid engine, rather than a full-fledged liquid propellant engine. It was apparently the world's first attempt to use a design of this type.
According to various sources, the engine was designed to burn between 15 and 20 seconds.
Known specifications of Engine 09:
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A schematic of the 09 engine. (shown upside down). Credit: GDL