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Mechanical Engineering (ABSTRACT)A research effort aimed at enhancing ACSYNT, a computer program for aircraft conceptual design, has necessitated the development of methods for predicting inlet drag.Originally, the drag of only one inlet type, the variable-geometry conical inlet, could be calculated within ACSYNT. This prompted the present research which resulted in the creation of a modular suite of subroutines that extend the capability of ACSYNT. Using this new source code, ACSYNT can now predict the drag of subsonic and supersonic pitot inlets, fixed-and variable-geometry conical inlets, and two-dimensional supersonic inlets.Even though the requirement of computational efficiency has necessitated that many simplifications be made in the analysis, the drag calculations have a sound physical basis. The semi-empirical methods have been extracted from a number of sources based on an extensive literature survey, and these have been enhanced to encompass the full range of inlet operating conditions. The effectiveness of the methods has been demonstrated by comparing some results of the predictions to published data. AcknowledgementsI would like to thank the fallowing faculty members who served on my committee:Professor Eugene F. Brown, my advisor, for his willing assistance and guidance during the course of this work; Professor Arvid Myklebust, for his able management of the ACSYNT project; Professor J. Robert Mahan, for getting me involved with the project.Grateful acknowledgement is given to the Powered Lift Investigations Branch, NASA Ames Research Center, for providing the financial support for this work.Thanks also to and the rest of the ACSYNT team. The meetings wouldn't have been the same without them! Finally, a special thanks to my wife who made great sacrifices so that I could come to Virginia Tech. Without her love and support, we just wouldn't be here.. .. .. Tables Table 1. NACA I-Series Cowl Coordinates (from Seddon and Goldsmith ( 1985), Aircraft conceptual design is the process whereby the size and general configuration of an aircraft are selected to meet a specific mission profile. This process involves the choice of a candidate aircraft layout, and an initial guess must be made as to its overall size. Acknowledgements IllThe aircraft is then synthesized by a series of design relations which describe important aspects of the design such as the aerodynamic performance, component weights and the propulsion system performance. This synthesis enables the aircraft weight to be calculated, and hence the initial aircraft layout can be revised accordingly. The procedure needs to be repeated until the design converges satisfactorily. This iterative design process is best performed by computer, thus enabling the design turn-around time to be minimized without foregoing the use of relatively complex design relations.ACSYNT is one such computer program for aircraft synthesis and conceptual design.It is distinguished by the incorporation of numerical optimization techniques to allow specific characteri...

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