Development of Hygroscopic Pyrotechnics for Warm Cloud Seeding

1 Introduction Hygroscopic pyrotechnics is a kind of pyrotechnics whose main ingredients includes oxidizer, oxidizable agent, organic binder and additives, the oxidizer can be chlorate or perchlorate such as potassium chlorate, sodium chlorate , potassium perchlorate, sodium perchlorate and so on, the oxidizable agent includes magnesium or aluminum, the organic binder can be resin or liquid rubber according to the shaping method. The salts produced by decomposition of the oxidizer acts as the hygroscopic particles while the oxygen play as the oxidizer to react with the oxidizable agent such as metal and organic binder, the reaction are all heat-release reaction so the salts produced by decomposition vapor to produce the salt particles. 2 Static Test of the Pyrotechnics Mix 50g ingredients of each formulation, the mixture includes potassium perchlorate, magnesium powder, organic binder, chloride and additives. Shape the mixture into a grain with a diameter of 10mm and a length of 10mm. The grain burns in a box whose dimension is 60x60x60cm, and the smoke is pumped into the electrostatic collection box through a tube of 10mm in diameter. The voltage between the anode and cathode is 5000V, the particles are collected on a carbon film and observed by Scanning Electron Microscope(SEM), the particles' size are stated and compare them each other. The statistic results show: (1) The formulation which has a greater burning rate produces bigger particles. (2) Higher magnesium content is propitious to enhance the particle size 3 Dynamic Test of the Pyrotechnic Shape the pyrotechnics mixture into a grain which is 35mm in diameter and 300mm in length, a layer of restrictor is enwrapped on the surface of the grain to ensure a end-burning, the grain burned in the wind channel at a speed of 50m/s and 100m/s, burning time of the grain is 5min, a FSSP(range 0.5`8µm) is used to measure the large particles' size. The dynamic test results is consistent with the static test, the formulation which has a bigger particle size in static test also shows a good result in dynamic test. While high wind speed goes against producing bigger particles. 4 Conclusion The static test and dynamic test in the wind channel show: (1) High burning rate is propitious to produce bigger particles. (2) High magnesium content is propitious to produce bigger particles. (3) The static test result accords with the dynamic test result. (4) High wind speed goes against producing bigger particles.