A History of Research and a Review of Recent Developments

Introduction xxi
in the seventeenth and eighteenth centuries. It was important to know the
pressure that resulted from the firing of gunpowder, which was needed to
estimate the required structural strength of gun barrels, and to calculate initial
projectile speeds. The appearance of gunpowder and artillery in Europe started
in the thirteenth century, and Berthold Schwarz, a German, is usually credited
with the honour of harnessing the propellant force of gunpowder. Roger Bacon
gave an account of the composition of gunpowder in the middle of the thirteenth
century, and artillery in the form of cannons seems to have been introduced to
the battlefield in the fourteenth century. The development of the material and
manufacturing methods for cannons proceeded steadily via cast bronze or
brass (gunmetal) to wrought iron (longitudinal rods and rings) and cast iron
by the sixteenth century.
In England, the underrated Benjamin Robins wrote his New Principles of
Gunnery in 1742, in which the first chapter dealt with force of gunpowder
and the pressure on a ball at the instant of explosion of the powder. The
pressure was needed to calculate the velocity of the ball when leaving the
muzzle of the cannon. Robins, whose scientific work in this field has been
admirably summarized in recent times by Professor W.Johnson in a paper in
Volume 4 of the International Journal of Impact Engineering, was dealing
mainly with relatively lightweight cannon balls weighing about twenty-four
pounds. To find the force on them he describes the burning of gunpowder at
the top end of a closed tube almost filled with water. He found that an ounce
of gunpowder expands to a volume 244 times as great at room temperature,
and to a volume 1000 times as great at the temperature of ‘red hot iron’. This
told him that the initial pressure on the shot would be about 1000 atmospheres
and he used this to calculate the muzzle velocity of the ball.
Robins also introduced the concept of the ballistic pendulum to measure
projectile velocity. This consisted of a block of wood attached to an iron
pendulum, which was suspended from a metal crosspiece supported by a
substantial three-legged frame. The movement of the block when struck by a
projectile was recorded by means of a ribbon attached to the underside of the
block, and passing over a transverse member attached to the supporting frame.
Robins, who was a mathematician, also proposed that large guns should have
rifled barrels, but a century was to pass before this idea was taken up.
Ballistic pendulums were increased in size and strength during the eighteenth
century but it was not until the latter half of the nineteenth century that major
new developments occurred. Firstly, Alfred Krupp in Germany produced an
all-steel gun, drilled out from a single block of cast metal, and then Captain
T.J. Rodman of the Ordnance Department of the US Army produced a gauge
for the measurement of the pressure exerted by the burning of gunpowder in
a closed vessel. This was a useful development, described in Rodman’s fifth
and sixth reports on his experimental work, and was in the form of an
indentation apparatus, known as a cutter gauge. A gun was prepared by drilling
transversely at intervals so that a plug containing a cylindrical indenting tool