Investigation of Cold Colored Smoke Production

Abstract : The main objective of this project is to develop a non-fading colored cold smoke composition for use in a signal cartridge for practice bombs. The primary constraint is that the substance must not require any form of heat to produce the smoke; hence the term 'cold smoke'. The principal use of the colored cold smoke charge is to mark the point of impact of practice bombs used by the Canadian Forces (CF). In summertime, white smoke produced by titanium tetrachloride (TiCl4) is satisfactory; however, colored smoke is required during winter because of the white snow background. Different methods for producing large colored smoke clouds for use as spotting charges are evaluated. The problem of the disappearance, or bleaching, of the orange color from vanadium oxytrichloride (VOCl3) clouds during times of high relative humidity is considered. It is postulated that this is caused by the absorption of large quantities of atmospheric moisture by the smoke. A model has been developed to study the process. This model makes the key predictions concerning the absorption of very large amounts of atmospheric moisture by VOCl3 type smokes above a relative humidity of 80% and the very small importance of temperature as a parameter. These predictions are, in general, corroborated very well by experiment. Possible solutions to this color bleaching problem are discussed, including one that calls for the synthesis of hydrolyzable vanadium compounds with nonhygroscopic leaving groups.