DETERMINATION OF METEOROLOGICAL CORRECTIONS ON THE RANGES OF GUNS.

Abstract

A projectile in its flight spends more time in the upper part of the trajectory because of its lower vertical velocity, so that when correcting for range and deflection the winds in the upper regions have more time to affect the range or deflection of the projectile and should be given more consideration or weight than the winds lower down. The less dense air composing these upper winds and the decreased horizontal velocity are other factors that must be taken into consideration in order to properly determine the weight that the winds at various heights should be given. The resistance offered a projectile in its flight varies with the density of the air, other factors being constant. The density aloft is computed from values of pressure and temperature determined from airplane flights. The ratio of observed to normal is then computed and used in making the corrections. A change in the velocity of sound arising from a change in temperature has the effect of changing the air resistance law of a projectile; hence changing the range of a projectile. Ballistic temperature is computed from values obtained from airplane observations of temperature and by the use of temperature weighting factor curves. These curves are of such a nature that the ballistic temperature may be lower than the lowest actual temperature.