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Cool Gas Generator Technologies

A Cool Gas Generator can best be described as a “tamed” solid propellant motor, both used solid propellants, ignited by an igniter to produce gasses. However, where a solid propellant rocket motor produces a mixture of very hot gasses to create thrust, a Cool Gas Generator produces a nearly pure gas at ambient temperature that can be used for many different applications than only propelling rockets and missiles.

How does it work

A good analogy for the working of a Cool Gas Generator is a cigarette. After ignition, a reaction front moves down from the top (where it is ignited) towards the exit. The gasses that are produced in the reaction front can only get to the exit through the porous grain that is not yet decomposed. There it cools down to the temperature of the grain which is the temperature of the CGG before firing.

For the last part of the grain this process does not work and below the grain a cooler and filter is installed that cools down the last part of the gasses and also filters out volatiles and unwanted reaction products.

The chemical reaction inside the CGG is designed in such a way that only the wanted gas is produced and as little as possible by-products. HDES has developed, on the basis of TNO work, grains that produce oxygen and Carbon dioxide gas. Grains that produce other gasses are possible and HDES has identified different formulations for different gasses. In the reaction, solid compounds reaction to form other solid materials and the required gas. It is important to design the CGG in such a way that both the grain is stable and porous before and after the reaction.


The ignition puts a bit of energy into the top layer of the grain, enough to start the reaction which is self-sustained and continues through the whole grain. The ignition can be done by a glow plug, a pyrotechnic squib or by a mechanical impact on a percussion cap.

Why a Cool Gas Generator?

Due to the use of solid propellants to produce a pure gas the advantages of solid propellant rocket motors can be applied to pure gas storage, like no pressure during storage, very rugged devices and a long life time without maintenance.

Our Cool Gas generators do not use any toxic propellants and the remaining products are also non-toxic and inert.

HDES has tested its Cool Gas Generators over a broad range of temperatures and (back) pressures and they perform very stable under all circumstances.

CGG casing technologies

The propellant is the core of the Cool Gas Generator, but the casing or housing is just as important. HDES has designed different kinds of housings from different materials like Titanium and stainless steel. As the remainder of the reaction after the gas production is hot, a good thermal design is very important and HDES has the knowledge to deal with these problems. It has worked with different kinds of thermal protection to limit the temperature of the outside wall and even has used this heat energy in a positive way.

Other technologies

Due to the know-how built up during the Cool Gas Generator development, HDES has also acquired technologies that are related and available for our customers. These are:

  • High temp thermal structural design and testing
  • Ignition systems for pyrotechnic and other products
  • Fluid dynamic system design, construction and testing
  • Test stands and test equipment design, construction and qualification
  • IoT systems