A scheduling model for the aerial relay system
Author(s)Ausrotas, Raymond A.; Liu, Elliott Wu-Hsun.
Massachusetts Institute of Technology. Flight Transportation Laboratory
Langley Research Center.
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Introduction: The growth of air travel in the United States during the last 40 years has been caused by a fusion of technology and economics. Aircraft design improvements, resulting-in higher speed and larger size, have increased the efficiency and productivity of airplanes. Airlines have passed on these savings to the public through ever-lower ticket prices. At the same time, the U.S. economy has had substantial growth in per capita GNP (and per capita disposable income), thus compounding the consumer's ability to purchase travel. One million passengers flew in the U.S. in 1938; 240 million flew in 1978. As travel grew, the infrastructure grew with it. Old airports expanded and new airfields and terminals were built; the air traffic control system was modernized to keep pace with the jets; airlines took advantage of the computer and communications explosions and adapted them to their own needs. But eventually air travel created its own set of problems. Increased operations of jets caused the once-curious and proud residents near airports to clamor for relief from incessant noise. Improved engines and a leveling of operations due to the introduction of wide-body aircraft have abated complaints somewhat, but any plans for airport expansion are automatically resisted. Similarly, unless airports are placed far away from population areas (Kansas City, Mirabelle, Fort Worth-Dallas) and contain sufficient acreage to effectively hide the noise within the airport boundaries, they will not be built. Thus, capacity at large hubs is running out and no relief seems possible through airport expansion due to political and environmental reasons. With rapidly rising fuel costs, congestion at airports is also diminishing the productivity gains of fuel-efficient aircraft and causing the price of air travel to increase. Future technological innovations (metering and spacing of aircraft, wake vortex reduction, etc.) promise to increase airport capacity. However, the gambit of substituting ever larger aircraft for smaller ones will eventually transfer the congestion to the ground side of the airport (already Los Angeles International Airport prefers to have a wide-body operation replaced by a narrow-body -2- because of access problems). Thus, if the system of air transportation remains as currently constituted, further growth in air travel will be stymied by a combination of energy (costs and availability) and congestion (air and land) in the not-too-distant future. Such considerations have led some observers of the aviation scene to conclude that the air transportation mode is simply maturing, just as other transportation modes have in the past. Other analysts, more optimistically, note that some fundamental changes to the existing system of transporting people and cargo by air could allow growth to continue. One of the more imaginative and radical departures is the Aerial Relay System (Kyser, 1979). Briefly, in the Aerial Relay System a series of "liners", made up of "liner 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 1. 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 take-off 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 feeders' 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 (O-D) traffic could continue to be served by dedicated aircraft at the major airports. Alternatively, the Relay system could serve as the major O-D 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 while allowing continued growth by the air mode. Clearly, substantial engineering and design work is required before the system can be implemented. However, some questions regarding its operational feasibility can be addressed to insure that there are no fundamental drawbacks to the general concept. The scheduling of liners, i.e. the ability to calculate their position during the course of the day, and the estimation of the passenger flow in response to this service, is one such consideration. This report describes an interactive computer scheduling model to perform these functions for the Aerial Relay System.
September 1979Includes bibliographical references (p. 21)
Cambridge, Mass. : Massachusetts Institute of Technology, Flight Transportation Laboratory ; 1979
FTL report (Massachusetts Institute of Technology. Flight Transportation Laboratory) ; R79-10NASA contractor report ; NASA CR-159387
Production scheduling, Airports, Airlines, Traffic control, United States