Mobility of Cargo Trains during Year Two of the Proof-of-Concept South Pole Traverse

摘要

The U.S. Antarctic Program is conducting a proof-of-concept traverse to haul heavy cargo 1600 km from McMurdo Station to South Pole Station. During the 2003-04 season (year two), the tractor-trains experienced poor mobility over undisturbed snow on the Ross Ice Shelf. despite relatively low sled ski pressures and encouraging results of pre-departure tests conducted on the McMurdo Ice Shelf. To understand why, we conducted expedient mobility tests, snow-strength measurements, and snow-pit studies along 250-km of route as the traverse returned to McMurdo. The key phenomenon causing train immobility appears to be traction-slip-resistance feedback resulting from the sled skis riding in the ruts made by the towing tractors. We measured much lower towing resistance when the same sleds were towed over undisturbed snow outside of the tractor ruts. Large pitch and roll motions and consequently large resistance peaks, also occurred when several sleds were towed in series. The role of snow strength was more difficult to assess. Hard sastrugi caused severe motions and sled breakdowns. Decreasing average strength towards the center of the Ross Ice Shelf agreed with qualitatively worsening mobility but quantitative results were inconclusive. Also, increased measured strength on the previously traveled trail was insufficient to account for improved mobility of the returning fleet. The year-two results formed the basis for recommendations to improve fleet mobility for year three: tow fuel sleds in 2 x 2 configurations, rather than four in-line; increase the gauge of the other sleds to place the skis outside of the tractor ruts; increase ski area and alter nose shape for the fuel sleds; and install instrumentation to monitor towing forces, sled sinkage, and snow strength along the entire route. The U.S. Antarctic Program adopted these recommendations.