Smoke Characteristics of Pyrolants

The smoke characteristics of three types of pyrolants, namely nitropolymer pyrolants composed of NC-NG with and without a nickel catalyst, and a B-KNO3 pyrolant, have been examined in relation to the use of these pyrolants as igniters of rocket motors. Though nitropolymer pyrolants are fundamentally smokeless in nature, a large amount of black smoke is formed when they burn at low pressures below about 4 MPa due to incomplete combustion. Metallic nickel or organonickel compounds are known to catalyze the gas-phase reaction of nitropolymer pyrolants. 

The mass fraction of nickel powder incorporated into the NP pyrolant was 0.01 and the diameter of the nickel particles was 0.1 pm. The NP pyrolants with and without nickel particles were pressed into pellet-shaped grains 1 mm in diameter and 1 mm in length. The BK pyrolant was pressed into pellet-shaped grains 3 mm in diameter and 3 mm in length. 

The heats of explosion, of the pyrolants are shown as a function of pressure 

NP pyrolant is caused by incomplete combustion at about 4 MPa and that the increased of the NP-Ni pyrolant is caused by a catalytic effect on the gas-phase re- 

The smoke characteristics and the ignition capabilities of igniters are evaluated by using a micro-rocket motor. Ignition delay time and rate of pressure rise are 

The heats of explosion, of the pyrolants are shown as a function of pressure in Fig. 12.3. It is evident that H p of the NP pyrolant is increased by the addition of nickel particles in the low-pressure region below about 2 MPa. The measured of the NP-Ni pyrolant becomes less pressure-dependent and reaches approximately 97 % of the theoretical value. The results indicate that the lower value of H p of the NP pyrolant is caused by incomplete combustion at about 4 MPa and that the increased H p of the NP-Ni pyrolant is caused by a catalytic effect on the gas-phase reaction which increases the temperature. The gas-phase reduction of NO to N2 in the dark zone of the NP pyrolant in the low-pressure region is promoted by the addition of the nickel particles. 

BK and NP-Ni igniters, the attenuation by the NP-Ni igniter is much lower than that by the BK igniter for the same mass of igniter grain. 

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Table 12.7 Chemical formulations of the pyrolants used to evaluate smoke characteristics (mass fraction).

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