The PFS Polarstern of the Alfred Wegener Institute for Polar Research: A 20.000 HP icebreaker with a twin hull and a total weight of 17,000 metric tonnes. It has a lenght of 120 metres and a height of 52 m. At temperatures below -50°C, it can go through 1.5 metre thick ice with a constant speed of 6 knots (~ 11 km/h). Thicker ice sheets can be rammed. The capacity of the Diesel tank is 3,000 metric tonnes and serves as an emergency energy source in case the ship gets trapped in the ice and has to spend a winter there.