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The Jetex engine was a type of solid-fuel rocket engine developed for use as a powerplant for model aircraft. First developed in 1947, they were available from 1953, sold by the Wilmot and Mansour Company of Southampton. The company also developed kits that used Jetex power.
Jetex engines were powered by a solid pellet of guanidine nitrate, which burnt to release variety of gases in copious volumes, and leaving no solid residue or ash. Thrust developed was fairly modest, suitable for horizontally launched flying models rather than vertically launched rockets. The exhaust gas was not excessively hot either, which conferred a safety advantage. Fuel was manufactured by Imperial Chemical Industries (ICI). The engine casing was made of aluminium and was reusable, new fuel pellets and ignition wick being a consumable that could be bought and used in the engine.
Jetex was fairly popular among aeromodellers for some time, but by the 1970s was largely forgotten. Recently, there has been a reawakening of interest in Jetex - in the mid 90s a similar device called the Rapier was launched, and many old plans for Jetex powered models were dusted off and built with the new engines. Other types of engine such as the disposable Estes type are also sometimes used for models of this kind.
Compared with modern Estes-type rockets, the Jetex is fairly different. It has a much gentler, cooler exhaust, so flight characteristics tend to feature gradual acceleration rather than firework-like performance. The cooler exhaust is easier to handle and does not require extensive flameproofing of the airframe. However, the fuel is more toxic and requires special handling to keep it in working condition. As a result Jetex were often quite unreliable, failing to fire often.
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