Innovations in over-snow cargo transport

The United States Antarctic Program (USAP) is developing tractor-sled trains to haul heavy cargo 1600 km from McMurdo Station to South Pole Station. In 2003, the proof-of-concept fleet experienced poor mobility and numerous sled breakdowns when attempting to cross the Ross Ice Shelf. Based on in-situ mobility tests, we recommended several expedient changes to the sled trains: tow the sleds outside of the tractor ruts, build larger skis with elliptical noses, and accommodate sled motions via compliant bushings. The USAP adopted these recommendations, the sleds performed well, and the fleet completed its first successful cargo delivery to South Pole in December 2005. For that season, we designed and the fleet successfully trialed a novel fuel sled consisting of a transportable fuel bladder strapped onto a sheet of durable, low-friction plastic. The resulting sled costs about one-quarter that of a steel tank sled, has about one-eighth of the tare weight and increases the expected fuel delivered per tractor almost nine times. The durability of these bladder sleds over rough terrain must yet be assessed, but their high fuel-delivery efficiency, compared with the present method of aircraft delivery, is worth pursuing. For example, a seven-tractor fleet completing three round trips per season could deliver fuel to South Pole equivalent to 92 LC-130 flights while consuming about one-quarter of the fuel required for aircraft delivery. Economic analysis shows that reduced aircraft costs could payoff the capital cost of a traverse fleet within a single season.