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Cannons HAIL CANNON HANDBOOK Our background was a little different from those who had gone before us, in that we had the advantage of knowledge in important technical fields related to the design and operation of such devices, as well as the necessary workshops to build and test them. Hail cannons are believed to have been used seriously as early as the 1600's. How effective they were then or later is not recorded sufficiently to allow the claim that they have a successful history of 400 years, but certainly the _ ____ ~__ _ ~<;!e~t!~.pi=~Il2~<2.uEqJ9~ __ __T!!~O~IES_ _ __._ ____. a long time. During World War One changes in weather were noted to coincide with the use of artillery barrages, changes included hailstorms changing to slush after the guns began firing. There are many other tales which seek to prove that hail cannons work, and there are probably many which would dispute the claim. History Our history in this field is relatively recent. The serious damage done to crops in our area by hail was beginning to threaten the viability of orchards, as operating margins became tighter and quality demands increased. Having heard the history of hail cannons from various sources, the possibility that they may have a useful part to play in our operations had to be taken seriously. -~-~";,,:. ; ;,,:t~;<ic. .:"'XV~~ sometimes work, but it often fails to the extent that it can produce similar hailstones earlier. This suggested that the theory was partially right, but something was missing, and experience suggested that a return to basic theory rather than simplistic - n - - -explanatIo-nwa~s~eede(f" - -- --- AS part of the folklore of these devices, we were told they worked by ionisation and radiation among other things. These stories didn't provide any real basis for building and testing and they didn't seem to be based on any facts we knew about atmospheric physics, explosives, or gunnery. Cloud seeding One approach which is to first appearance related to hail cannons is the use of shells fired into the storm cloud, to release the chemical silver-iodide which is widely used in rain making operations. This method of attacking hailstorms is used in some parts of the world. .It is based on the theC?.U' that by causing the water vapour to form raindrops earlier than they would have formed, they can be made to fall as tiny ice particles rather than big chunks. The results suggest that this can MIKE EGGERS LTD. Nelson, New Zealand So we went back to the basic theory of what is known about meteorology. Why are there clouds? Why does it rain? and why does it hail? These were our basic questions. When we were convinced we had separated the fact from fiction we were left with trying to understand where the relatively small amount of energy from an explosion on the ground could affect the formation of hail occurring perhaps to 3 Km up in the atmosphere. So we then went to the basic theory of sound as it travels through the air and we found that what we learnt at school wasn't the real story for very loud sounds from explosions. The people who make explosives and bombs deal in an area called explosive acoustics, which gave an explanation of how the sound energy remained relatively concentrated over such long distances. Page 1 EXHIBIT A;