An Analysis of Thrust Estimation: A Definition of Thrust and a Study of the Effects of Various types of Intake

WITH the coming of high speed flight it becomes increasingly necessary to define clearly what is meant by the thrust of a propulsive unit, or if an arbitrary definition is made, a clear idea of the full implications of such a definition is necessary. The latter case is the present day state of affairs, and to cover the inadequacies of our definition of thrust, corrections are necessary under certain conditions. These corrections are usually accepted as an additional burden by the aerodynamicist under the varied titles of ‘spillage drag’, ‘incremental scoop drag’, ‘additive drag’ and ‘pre‐entry drag’ (these terms, while being in the same category, do not in fact all refer to the same thing). These concepts and their relative importance are discussed below.