LOW TEMPERATURE COEFFICIENT (LTC) PROPELLANTS

Ammunition now has to be safe in each climate zone, especially abroad, when carrying out UN missions. For use in a combat aircraft, for example, the ammunition should have high cook-off stability so that a self ignition reaction of the propellant does not occur while lying in the hot gun barrel. On the other hand, there is still the demand for high ballistic performance with low barrel erosion. Accordingly, conventional single- and multi-base propellants border on their limits. A new type of propellant was developed to solve the above problem. This new gun propellant (consisting of RDX, a nitrocellulose binder, and a three-component energetic plasticizer) has a high ignition temperature of about 210°C and significantly improved chemical stability compared with conventional gun propellants. Besides a high force constant at a low adiabatic flame temperature and a low molecular weight of the product gases (which is of value in terms of barrel erosion), the novel gun propellant has a further outstanding property: the burning rate hardly depends on the propellant temperature. This means that the temperature coefficient in Vieilles burning law is low. That is why we call the propellant a Low Temperature Coefficient (LTC) propellant. Since the burning rate does not depend much on the propellant initial temperature, neither does the maximum gas pressure in the gun. Therefore, the maximum permissible gas pressure can be exploited to full advantage and can be used to increase the muzzle velocity. In the meantime, the LTC gun propellant has been investigated successfully in the medium caliber range. The results of that investigation are presented and discussed in this paper.