Drag chains (launching)

Drag chains are heavy chain bundles laid alongside the launchways and shackled to the hull to brake and steady a ship during an end (gravity) launch. As the hull slides down the ways and enters the water, it picks up speed; the drag chains pay out and absorb energy through friction as they are dragged off their stacks, limiting how far the freed hull travels across a narrow waterway and controlling the swing. The chain weight and number are calculated from the launch weight, ways slope, and available water. Too little drag and the ship overruns the basin; too much and the stern lifts hard at the moment the bow is still on the ways.