TRANSPORTING GAS BY AIRSHIP

This article will consider line-haul cargo transportation cost and optimum airspeed and fineness (length-diameter) ratio for a cargo-gas airship to provide a given number of Mcf-miles of natural-gas transportation per second. It will be also investigate the sensitivity of transportation cost to variations in design airspeed and fineness ratio, as well as the sensitivity of these three variables to changes in estimated costs of major airship components and changes in cargo-gas density. Under what are intended as middle-of-the-road assumptions with regard to component costs and performance, giant airships could transport natural gas on long hauls for about 2 mill/100 Mcf-mi, assuming that the transportation of non-gaseous commercial cargo as ballast would cover the cost of its own built-in accommodations (e. g. , petroleum tanks) and of crews and control systems. Designing for unitary-specific-gravity gas instead of 0. 60-gravity natural gas reduces cost by almost one-sixth on a ton-mile basis, comparing heavy gas with lighter gas plus associated ballast. In airships of roughly comparable ton-mile capability, hauling petroleum as the only commercial cargo with a 0. 10-gravity carrier gas is estimated to cost about 1 mill/ton-mi. Economies of scale are moderate for small craft, but taper off as successively larger airships are considered. The annual cost of owning and operating a natural-gas-hauling airship varies as the eight-tenths power of transportation capability for the largest airships considered and as the seven-tenths power for the smallest. Reducing capability by a factor of 16 from the benchmark level doubles the unit cost of transportation.