HIGH EFFICIENCY FUEL SLEDS FOR POLAR TRAVERSES

摘要

The National Science Foundation has implemented over-snow traverses to resupply its research stations at South Pole, Antarctica, and Summit, Greenland. Traverse fleets consist of rubber-tracked tractors towing groups of sleds over natural snow, with fuel being the primary cargo. We describe here the evolution of lightweight, high-efficiency fuel sleds for Polar traverses. These sleds consist of flexible bladders strapped to sheets of high molecular weight polyethylene (HMW-PE). They cost 1/6th, weigh 1/10th and triple the fuel delivered per tractor compared with steel sleds. An eight-tractor fleet has conducted three 3,400-km roundtrips to South Pole (2008 -11) with each traverse delivering ～320,000 kg of fuel while emitting <1% the pollutants, consuming 1/2 the fuel and saving ～$1.6M 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. Annual performance monitoring of both traverse fleets has revealed that bladder-sled towing resistance is largely governed by sliding friction. The flexible, low ground-pressure (～ 7 kPa) sleds produce very little snow-compaction resistance. Sliding friction can start high (μ～0.2) and drop in half as sleds warm up in response to frictional heating. As with conventional skis, 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. While sled durability still needs improvement, the outstanding efficiency and low cost of these sleds has transformed fuel delivery to US Polar research stations.