Jetex

The Jetex motor is a miniature solid-fuel rocket motor produced for use as a powerplant for aerodynamically lifted model aircraft.

Jetex 50B micro rocket motor

Jetex 50B packaging

Jetex was developed in 1947, by Wilmot, Mansour & Company Ltd of Southampton, it was first demonstrated in early 1948, and was available to the public in June 1948, when Aeromodeller featured Jetex power on its front cover. The first motors were the Jetex 100 and 200, with the more powerful Jetex 350 following in November 1948. The most popular motor, the Jetex 50, was introduced in May 1949, along with kits for a model plane and model car using Jetex power. The subsequent popularity of Jetex led to the manufacture of numerous kits by third party companies such as KeilKraft, Skyleada.

Classic Jetex Jetex motors are powered by a solid pellet consisting mainly of guanidine nitrate, which burns to release an exhaust gas in large volume, leaving little solid residue. Thrust developed is modest and sustained, making it suitable for aerodynamically lifted flying models. The exhaust gas is not excessively hot, which confers a safety advantage.

Motors are loaded with one or more solid fuel pellets and a combustible 'wick' is led through the exhaust nozzle to ignite the fuel. Fuel and wick were manufactured by Imperial Chemical Industries (ICI). The engine casing of the early motors are made of an aluminium alloy. On introduction fuel pellets and wick could be purchased separately and so the system is reusable.

Jetex power made a big impact in the late forties and early fifties, allowing new sorts of models, scale and duration, to be designed. Jetex went through a change of ownership in the mid 1950s and gradually its popularity waned. (Incidentally, Jetex motors were used extensively by AP Films/Century 21, during the 1960s for producing model vehicle exhaust effects for the 'Supermarionation' TV series.) However, by the late 1970s Jetex power had been largely forgotten.

Jet-X In 1985 Roy and Julie Lever of the UK company Powermax discovered a stock of original Jetex motors in the USA. These motors were of Sebel manufacture, comprising steel-bodied 50Cs and 50R/HTs. The Levers themselves undertook the manufacture of igniter fuse and fuel. By the following year Powermax launched a range of motors and fuel kits onto the UK market under the Jet-X brand. In the October 1986 issue of Aeromodeller, Peter Freebrey reviewed the new fuel and fuse, having made a number of successful test fights with a KeilKraft 'Space Jet'. In the USA it was not until August 1995 that the motors and new fuel and fuse were commercially imported. In that same month, Flying Models, in an editorial by Bob Hunt, hailed their arrival, enthusing that "safe and viable rocket power for model airplanes is back".

When the initial stock of Sebel motors came to an end Powermax introduced their own 'Z' series motors in the latter half of the 1990s. The range was eventually extended to include motors of 100 and 35 size. Though tales of uncertain ignition and variable performance plagued the Jet-X scene, the Levers must be credited with bringing the reloadable micro rocket concept back to practical life.

Rapier With the new millennium came another revival. A product called the Rapier was launched. This has similar weight, thrust and duration to Jetex and many old plans for Jetex powered models were dusted off and built and flown with the new motors. The Rapier is a single use motor with a cardboard case and a ceramic nozzle. In appearance it is more like a model rocket motor than the original Jetex.

Tendera In early 2020 another new, comparable range of motors was introduced, under the name Tendera. These are rather similar to the Rapiers, being one-time use motors having cardboard cases and ceramic nozzles.

For a detailed, comprehensive history of Jetex and its various successors please see Jetex.org.