Why did <i>Endurance</i> sink?

Abstract Sir Ernest Shackleton’s ship, Endurance , was crushed by Antarctic sea ice and sank in November 1915. Since then, it has been widely considered that Endurance was the strongest polar ship of its time and was lost because ice tore away the rudder. Based on expedition diaries, Shackleton’s correspondence, and structural analysis, this paper shows that Endurance was not among the strongest ships of its time and that the rudder was not the main cause of the vessel sinking. While the final reason was tearing off the keel, Endurance sank because the vessel was simply crushed in compression by ice. This is not surprising, Endurance was not designed for compressive conditions in the Antarctic pack ice, but for easier conditions at the ice edge in the Arctic. The weakest part of its hull was the engine room area, which was not only larger than in other early Antarctic ships but also lacked beams to give strength against compression by ice. Comparison with other wooden polar ships is not favourable for Endurance : ships designed for compressive pack ice were stronger. It is also evident from archive research that Shackleton was well aware of the weaknesses of Endurance even before his expedition set sail for Antarctica.