Compact counter-recoil design of water cannon using a single nozzle with backward spray

A novel design of water cannons using off-the-shelf bullet and barrel was conceptualized, analyzed, prototyped and field-tested. The cannon was designed to be mounted on a remotely controlled carrier robot and its main propose was to utilize water impact to defuse explosives usually placed in metal or wooden containers. In the previous design, the firing created a large recoil force, which was likely to damage and/or immobilize the robot. In the new design presented here, the primary objective was to significantly reduce the recoil force by using backward spray near the muzzle, which allowed the cannon to maintain its destructive power without increasing the robot's payload. In this paper, the design process using a combination of Computational Fluid Dynamics simulations and experiments were presented. The combination was nontrivial but essential due to the limited prior knowledge of the employed bullet (for simulations) as well as firing safety regulation and high prototyping cost (for experiments). The final prototype of the cannon was field-tested and shown to be capable of reducing the recoil force to such an extent that the robot was visibly stationary.