What is Jetex ?
Jetex is a model propulsion technology that is now fifty years old. It is basically a form of rocket motor but some important characteristics are very different to those of motors used for model rocketry. Jetex motors are metal and reload able using fuel 'pellets', and traditionally Jetex fuel was ignited by a fuze which had to be lit by a match.
Jetex fuel is defined as being a non-explosive, gas generating substance. Because of this characteristic the thrust profile is for the most part a steady one. The thrust builds up for a couple of seconds immediately after ignition and will then stay largely steady, possibly increasing somewhat as the motor warms up until the fuel pellet is almost consumed, often a final 'spike' of thrust will mark the final consumption of a pellet. This can take a matter of several seconds. If a further pellet is loaded this will then commence to burn and again a gradual build followed by a period of steady thrust will ensue. The most common size, the 50 produces about 1/2 an ounce of steady thrust for around 16 seconds, with a few bumps in the profile to add a bit of interest! These thrust characteristics make Jetex suitable as a means of propulsion for free flight model aircraft.
Jetex was introduced in 1948 and development proceeded rapidly with a variety of different sized motors from .35 of an ounce to around 5 ounce. The first models were designed for out and out duration although scale models of the numerous new jet aircraft of the day were soon introduced. Wilmout Mansour founded the Jetex company and produced, as well as the motors a variety of different innovation models.
During the 1950's Wilmout Mansour sold out to the Sebel company who concentrated on less innovative, but arguably more practical motor designs. The Sebel business eventually folded when the company was purchased by an asset striper who sold off the tooling for scrap.
In recent years Jetex has enjoyed something of a revival. This can largely be attributed to Roy and Julie Lever of Powermax who in the late 80's apparently discovered a large quantity of steel Sebel motors in the USA. These were brought back to the UK and the Lever's arranged for the manufacture of fuel and igniter wick. Jetex was then remarketed under the title Jet-X.
Since then a variety of new and familiar products have appeared. Amerang models have remanufactured some of the Keil-Kraft range of scale kits. Powermax have introduced new 50 and 100 size motors and John Emmett has introduced an innovative ignition system, which eliminates the need for igniter wick, electrical ignition.
