Models for comparing air-only and sea/air transportation of wartime deployment cargo

Abstract

When faced with an overseas contingency, efficiencies may be gained by using ships in conjunction with aircraft to transport military cargo from the Continental United States (CONUS) to an overseas Port of Debarkation (POD). This thesis evaluates a proposal to load air-transportable cargo aboard vessels at CONUS seaports and to ship that cargo to an appropriately located sea-air- interface (SAI) for further transport by air to the final POD. This bi-modal approach is profoundly different from the current uni-modal paradigm where cargo loaded on a given platform at the port of embarkation continues on the same platform to the POD. Two mixed-integer programming models compare the incumbent and candidate transportation paradigms. The models are formulated in the General Algebraic Modeling System (GAMS) and run on a desktop PC. Solutions for a typical set of overseas airlift-only cargo requirements are obtained in less than one minute for both the air-only and bi-modal models. This research concludes that the bi-modal paradigm is less efficient than the uni-modal paradigm with respect to lift asset utilization and timeliness of deliveries, but may have merit as supplemental transportation to alleviate the backlog of surge cargo in the early phase of a conflict. For instance, by pre-positioning cargo at the SAIs, we are able to reduce the aircraft inventory required to execute our Time-Phased Force and Deployment Database from 44 to 30.