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ABSTRACT
Aerospace propulsion is based upon models and physical laws which govern the movement and speed of engines. This article details the various formulae and laws to be mastered (Bréguet and Tsiolkovski formulae for instance) in order to design a propulsion system efficiently. It provides the way of using estimates, reference levels and simplified designing laws for a cruise, an acceleration, a ballistic flight initially propelled. The understanding of these various data facilitates the ecquisition of certain calculation "reflexes". In order to gain a sound knowledge of these elements, certain exercises of application (antitank missiles, launcher restitution) are also explained in this article.
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Read the articleAUTHOR
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Marc BOUCHEZ: Graduate of the École catholique d'arts et métiers de Lyon and the École supérieure des techniques aérospatiales - Engineer in the aerodynamics, propulsion and lethality department of MBDA France - Temporary professor of propulsion at several universities and grandes écoles
INTRODUCTION
This article sets out simplified design laws for cruise, acceleration and initially powered ballistic flight, using various examples (rockets, missiles and aircraft).
Three formulas are used for non-propelled flight (with an initial speed generally obtained by initial propulsion), gliding or ballistic flight.
The other two formulas correspond to two particular cases of propulsion use: acceleration from one speed to another, or cruising flight (with two expressions whose authors have remained famous: the Tsiolkovski and Breguet formulas).
The simplified expressions used in this article thus enable reliable, but estimated, pre-sizing, which will then be confirmed during a project by more precise models and detailed trajectory calculations.
The examples and data provided are taken from the open literature, as the applications of these engines inevitably lead to restrictions on certain particular points of these propulsion systems from a commercial or military point of view.
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Aerospace propulsion
Simplified design laws
Bibliography
We have deliberately limited the bibliography to a few works that cover all the aspects presented here, and provide numerical examples and calculation methods that are accessible to engineers without supercomputers.
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