Theoretical study of network design methodologies for the aerial relay system

Abstract

Growth of the United States air transportation system is currently facing two major barriers: energy and congestion. While the price of fuel has gone up by approximately an order of magnitude in the last 10 years, there is no assurance that fuel will continue to be available at the levels desired by the airlines. At the same time, lack of capacity at the major airports is causing delays to increase, both in number and duration. Both of these factors are causing the price of air transportation to reverse a 40-year-old trend and to increase in real terms, negating gains in aircraft productivity and engine efficiency. These considerations have led some observers of the aviation scene to conclude that the air travel mode is reaching maturity, although various regulatory, economic, and technological options have been suggested which offer incremental improvements to the existing system. For substantial growth to continue, however, major structural changes may be necessary. One imaginative and radical departure is the Aerial Relay System (Albert C. Kyser, "The Aerial Relay System: An Energy Efficient Solution to the Airport Congestion Problem," NASA Technical Memorandum 80208, January 1980). Briefly, in the Aerial Relay System a series of "liners", made up of "line modules", continuously cruise over the United States at a set altitude and on a predetermined schedule. These liners are met by a fleet of "feeders" carrying aloft passengers bound for cities along the liners' routes and accepting passengers destined for their own base. The basic elements of the system are shown in Figure I. A fully-developed Relay system could provide frequent non-stop service between practically any two cities in the United States. The advantages of the Relay system are many. The elements of the system can be tailored for their own function leading to efficiency of operation: the liners for cruise conditions, the feeders optimized for short-haul takeoff and climb. But the basic attraction lies in the Relay system's ability to unload the major hubs' airports by utilizing secondary (or satellite) airports and smaller city airports for the feeder's operations; since one of the major functions of airports, especially those at large hubs, is the interchange of connecting passengers between airplanes, this transfer is now performed onboard the liners. The feeder from a smaller city or secondary airport takes up passengers bound for many destinations downstream (and accepts diverse passengers for the downward journey), bypassing the hub and relieving the hub of these operations. The Relay system would thus supplement and not replace the existing airline networks; the hub-to-hub origin-destination traffic could continue to be served by dedicated aircraft at the major airports. Alternatively, the Relay system could serve as the major link between large hubs while utilizing satellite airports and thus relieving the major airports of this type of traffic. Thus the Aerial Relay System has intrinsic appeal, as it could both relieve congestion and decrease energy consumption of the air mode. Clearly, substantial engineering and design work is required before the system can be implemented. However, some questions regarding the fundamental mathematical network properties of the Relay system can be addressed to insure that no basic drawbacks to the general concept exist. This report presents the derivation of a generalized algorithm which can be used for basic design studies of networks for the Aerial Relay System.