Jetex engine

The Jetex engine was a type of solid-fuel rocket engine produced for use as a powerplant for model aircraft. Originally developed in 1947, it was first demonstrated to the modelling press in early 1948, and were available to the public in June 1948, when "Aeromodeller" featured Jetex power on its front cover. The first motor was the Jetex 100, and the more powerful Jetex 350 and Jetex 200 followed soon afterwards. The most popular motor, the Jetex 50, was marketed in 1950, by Wilmot, Mansour & Company Ltd of Southampton. That company also developed model kits that used Jetex power.

Jetex engines were powered by a solid pellet of guanidine nitrate, which burnt to release a variety of gases in copious volumes, 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 and wick to ignite the pellets was manufactured by Imperial Chemical Industries (ICI). The engine casing was made of an aluminium alloy and was reusable, new fuel pellets and ignition wick being a consumable that could be bought and used in the engine.

Jetex power made a big impact in the late forties and early fifties, allowing new sorts of models, scale and duration, to be designed. Its popularity waned after the mid-fifties, and by the 1970s was largely forgotten. Recently, there has been a reawakening of interest in Jetex - in the mid 1990s, 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.

Compared with modern Estes-type rockets, the Jetex is quite 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 dry and in working condition (the fuel is slightly deliquescent and will gradually absorb moisture from the atmosphere which quickly renders it inactive). As a result, Jetex were often quite unreliable, failing to ignite, as modellers and keen schoolboys of the era will recall.

External links

* [http://www.jetex.org Jetex.org] This non-profit site is "the premier Web resource for information and advice about models powered by micro rocket motors, especially those exemplified by the Jetex series of engines".