Short-range Defensive Water Cannon
The short-range defensive water cannon is a weapon designed by Mindy Westerberg to provide formidable striking power in fixed defensive installations where the limitation of collateral damage is a high priority.
Based on commercial water jet cutter technology, the defensive water cannon uses electromagnetic fields to focus an ultra-high pressure water stream containing a yttrium aluminum garnet abrasive medium on targets up to almost 40 meters away. Beyond this range, the cutting jet disperses rapidly into harmless water vapor and garnet dust. The weapon can be set for shorter maximum ranges if desired.
Four weapons of this type were first deployed in defense of the temporary System Four headquarters atop the Drake Building in Philadelphia, set so that their jets could not hit nearby structures. In their sole engagement during that deployment, they brought down one of several Hughes OH-6 helicopters that was attacking the headquarters. This helicopter's crash in the street below demonstrated the limitations of the weapon system's ability to prevent collateral damage.
During the construction of XTS Firehawk, these weapons, plus several additional units, were installed on the vessel. In this installation, the cannon were modified for optional operation in a higher volume, less-focused mode without the abrasive medium. This permits their use in fighting fires on-board ship or at a range of up to 150 meters.