The test carriage is a structure made of trusses formed by steel tubes welded together. At the front of the carriage is a noseblock segment with grooves to catch the cables of the arresting gear. In the center of the carriage is the test article drop carriage, which holds the test article (such as a tire). At the back of the carriage is the reaction bucket which catches and rotates the water-jet from the propulsion system. When the propulsion system is activated, water hits the reaction bucket at the back of the carriage, propelling the carriage down the track. The test article is lowered to the track surface by hydraulic cylinders within the center drop carriage. At the end of the track, the noseblock catches the cables in the arrestment system, which slows the carriage to a stop.

The Science Behind the System

The thrust directed against the carriage by the propulsion system accelerates the carriage from rest (zero speed) to a maximum of 20 g's (250 miles per hour) over a distance of 121.9 m (400 ft). As the carriage passes over the test section of the track, two hydraulic cylinders lower the test item to make contact with the test surface. Then up to four hydraulic load cylinders push down with added force, resulting in increased vertical load on the test item. Hydraulic fluid from a storage container on the carriage flows into each hydraulic cylinder. The force on the test article can be increased or decreased as the cylinder's pressure changes. Two cylinders are used to lift and lower the test article, and the four cylinders are used to apply added force pushing downward on the test article.

Battery-powered cameras and instrumentation systems take pictures and collect data. As the test run is made, required data is collected by onboard sensors, sent to a signal converter, then the telemetry sent by microwave transmitter to a computer in the ground station instrumentation room. High-speed motion picture cameras contained in watertight boxes with plexiglass windows photograph the test articles. Additional pictures can be taken by cameras located at different positions along the track. At the end of the test run, the five grooves in the noseblock located at the front of the carriage catch the five arresting cables which are a part of the arrestment system located at the end of the track. The kinetic energy of the carriage which was built up at its launch is transferred to the arrestment system. As the kinetic energy of the carriage decreases, the speed of the carriage decreases until at the end of the track, the carriage comes to a stop.