Aerodynamic Versus Ballistic Flight
Open Journal of Fluid Dynamics, 2019, 9, 346-400 http://www.scirp.org/journal/ojfd ISSN Online: 2165-3860 ISSN Print: 2165-3852 Aerodynamic versus Ballistic Flight Jack Denur Electric & Gas Technology, Inc., Rowlett, TX, USA How to cite this paper: Denur, J. (2019) Abstract Aerodynamic versus Ballistic Flight. Open Journal of Fluid Dynamics, 9, 346-400. We consider, compare, and contrast various aspects of aerodynamic and bal- https://doi.org/10.4236/ojfd.2019.94023 listic flight. We compare the energy efficiency of aerodynamic level flight at a given altitude versus that of ballistic flight beginning and ending at this same Received: January 17, 2017 altitude. We show that for flights short compared to Earth’s radius, aerody- Accepted: December 15, 2019 Published: December 18, 2019 namic level flight with lift-to-drag ratio LD> 2 is more energy-efficient than ballistic flight, neglecting air resistance or drag in the latter. Smaller Copyright © 2019 by author(s) and LD suffices if air resistance in ballistic flight is not neglected. For a single Scientific Research Publishing Inc. This work is licensed under the Creative circumnavigation of Earth, we show that aerodynamic flight with LD> 4π Commons Attribution International is more energy-efficient than minimum-altitude circular-orbit ballistic space- License (CC BY 4.0). flight. We introduce the concept of gravitational scale height, which may in http://creativecommons.org/licenses/by/4.0/ an auxiliary way be helpful in understanding this result. For flights traversing Open Access N circumnavigations of Earth, if N 1 then even minimum-altitude circu- lar-orbit ballistic spaceflight is much more energy-efficient than aerodynamic flight because even at minimum circular-orbit spaceflight altitude air resis- tance is very small.
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