The groundwork of practical naval gunnery or exterior ballistics

364 Pages·2016·22.89 MB·English

by  Alger P.R.

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THE GROUNDWORK
OF
PRACTICAL NAVAL GUNNERY

GROUNDWORK
THE OF
PRACTICAL NAVAL GUNNERY
A
Study of the Principles and Practice of Exterior
Ballistics, as Applied to Naval Gunnery
And of the
Computation and Use of Ballistic and Range Tables
By PHILIP R. ALGER
Professor of Mathematics, U. S. Navy
Revised and Extended to Include the Formulas and Methodsof
Colonel James M. Ingalls, U. S. Army
By the Officers on Duty in the Department of Ordnance and Gunnery
United States Naval Academy
1914-15
ANMAPOLIS, MD.
THE UNITED STATES NAVAL INSTITUTE
1915
^^
COPTRIGHT, 1915, BY
P. C. ALLEN
Sec.and Tkeas. U. S. Naval Institute
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Column
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PREFACE
6 ' '•
(a) An arrangement that would appear more logical and consecutive to a mid-
shipman taking up the study of the subject for the first time.
(b) A more clear distinction between the methods and formula? that are purely
educational and those that are actually used in practice.
(c) The rendering more easily understood of quite a number of points in the
older text book that seemed in the past to give great trouble to the midshipmen in
their study of the subject.
(d) The modification of the problems given in the textbook to make them apply
to modern United States Naval Ordnance. The problems in the older text book dealt
largely with foreign ordnance, and exclusively with guns, projectiles, velocities, etc.,
that are now obsolete, or nearly so; and, while many of the older problems have been
retained as valuable examples of principles, a large number of problems dealing with
present-day conditions and ordnance have been added.
(e) An effort has been made to give a complete discussion of the practical use
of the range tables, a subject but lightly touched upon in the older text book. In
orderto accomplish this a large number of officers, in the Atlantic fleet and elsewhere,
were requested to contribute such knowledge as they might have on this subject, and
the matter received from them has been incorporated in the chapter on this subject.
The discussion of this point should therefore include all the most up-to-date practice
in the use of therange tables.
4. In preparing this revision for the purpose indicated in the preceding para-
graphs, the logical treatment of the subject seemed to indicate its division under two
general heads, as follows
(A) The treatment of the trajectory as a plane curve; which, in turn, logically
subdivides itself under two sub-heads, as follows
(a) General definitions, etc.; the trajectory in vacuum; the resistance of the air
and the retardation due thereto; the ballistic coefficient in its fullest form; the equa-
tion to the trajectory in air under certain specified and limited conditions; and the
approximate determination of the elements of the trajectory by the use of the above
special equation. In other words, the features that are of educational rather than of
practical value, but which are necessary to an understanding of the practical methods
that are to follow.
(b) The more exact and practical theories and formulae; that is, the ones that
are generally used in practical work. This subdivision is not a rigid one, as it will be
seen that some of the approximate formulae and methods are sufficiently accurate to
permit of theiruse in practice, and they are so used; but the general statement of the
subdivision may be accepted as logical, with this one reservation.
(B) Aconsideration of the variation of the actual trajectory from a plane curve,
which treats of the influence upon the motion of the projectile of drift and wind, and
of the effect upon the fall of the projectile relative to the target of motion of the gun
and target. That is, having treated under the first division those computations
thatare notmaterially affectedbythe variations of the trajectory from a plane curve
in the second division we treat of the effect of such deviations upon accuracy of fire.
In other words, there are here to be discussed the steps taken to overcome the inaccu-
racies in fire caused by the variation of the trajectory from a plane curve, in order to
hit a moving target with a shot fired from a gun mounted on a moving platform,
when there is a wind blowing.
5. Following these natural and logical divisions of the subject comes a' full
discussion of the range tables, column by column, and of the methods of computing
the data contained in them, and of using this data after it has been computed and
tabulated.