High efficiency fuel sleds for polar traverses

We describe here the evolution of lightweight, high-efficiency fuel sleds for Polar over-snow traverses. These sleds consist of flexible bladders strapped to sheets of high molecular weight polyethylene. They cost 1/6th, weigh 1/10th and triple the fuel delivered per towing tractor compared with steel sleds. An eight-tractor fleet has conducted three 3400-km roundtrips to South Pole with each traverse delivering ∼320,000 kg of fuel while emitting <1% the pollutants, consuming 1/2 the fuel and saving ∼$1.6 M compared with aircraft resupply. A two-tractor fleet in Greenland recently delivered ∼83,000 kg of fuel in bladder sleds to Summit with similar benefits. Performance monitoring has revealed that bladder-sled towing resistance is largely governed by sliding friction, which can start high and drop in half over the first 30 min of travel. Frictional heating probably produces a thin water layer that lubricates the sled–snow interface. Consequently, towing resistance depends on the thermal budget of the sled. For example, black fuel bladders increase solar gain and thus decrease sled resistance; data suggest they could double again the fuel delivered per tractor. The outstanding efficiency and low cost of these sleds has transformed fuel delivery to Polar research stations.