An ice tank is a specific type of ship model basin designed to test hull designs intended to become ice-breaking ships. By examining the characteristics of a model ship in an ice tank, designers are able to make changes to the design to create a better ship. The ice tank is a large-scale water tank that can be adjusted to a specific water temperature, current and, most importantly, ice thickness. The ice tank is instrumental in understanding and testing a model ship's ability to navigate through the icy water by measuring resistance, required propeller thrust and maneuvering characteristics in relation to specific ice thicknesses.
Whenever a new style or design of ship is being introduced, it is common to test a miniature model of the vessel in a machine known as a ship model basin. As the title implies, the machine is a large basin in which the model ships are tested in a variety of ocean conditions. Wind, current and waves are the typical test subjects. Mechanical devices located in the basin are programed to create scale waves sized according to the scale of the model ship being tested. Readings are taken to capture the ship's performance in the simulated storm and water conditions. Ship designers typically note the recordings and modify the model to allow for increased performance and safety, and the improved model is once again tested until the desired results are reached.
There are several versions of the ship model basin, with the ice tank being used exclusively for the design and testing of ice-breaking vessels. A scale model of a ship is placed in the ice tank and the tank is frozen in such a manner that even the ice crystals are in scale to the ship model. This creates an actual lifelike testing model. The scale ship is usually a model that is carved from wood or paraffin wax on a computerized milling machine.
While in the ice tank, the model ship is tested for its ability to maneuver in the icy water. The hull design is tested in the ice tank to discover the flow of icy water and ice particles and chunks across and around the rudder. It is common to test both forward and reverse operation of the model while it is in the ice tank. Propeller designs are also tested in the tanks to demonstrate ice-chopping ability as well as the ability to push the heavy ice chunks away from the ship.