"Dynamite Guns: Brilliant Technical Dead-Ends! " Topic

"A major role is played in the Dawlish Chronicles novel Britannia's Shark, set in 1881, by an experimental "pneumatic projector" – essentially a gun from which the projectile is launched by compressed air. Such weapons were considered very promising in the 1880s and 1890s and indeed the inventor John Phillip Holland, who also features in "Britannia's Shark", built a 9-inch projector into his 1882 Fenian Ram, arguably the first successful submarine.

Though forgotten today, the concept was very attractive in its own day and the spur to its development was the recent invention of dynamite, an explosive of considerably greater power than any other previously available. Filling conventional artillery shells with dynamite would obviously increase their potency but the concern was that dynamite was sufficiently unstable as to be incapable of resisting the rapid acceleration involved in discharge from a conventional gun. A method of propulsion which would give slower acceleration, but comparable range, was what was required. The answer was to eject the shell from a giant blow-pipe by means of compressed air.

There were other advantages. Lighter gauge metal could be used for the discharge tube than would be needed for a conventional gun-barrel and larger-calibre weapons could be carried for the same weight. Also the lack of flame and smoke when the projectile was discharged would reduce visibility, and chance of location, particularly at night. The greatest potential was as an anti-shipping weapon. A direct hit would not be necessary if a large enough projectile could be dropped into the water close to the ship. Exploding underwater, the shock waves would rupture the hull. Recognition of the effectiveness of below-waterline attack had already led to the development of the self-propelled torpedo. At a time however when torpedo speeds, ranges and sizes were still low a pneumatic projector offered the opportunity of landing a larger charge close to a moving ship more quickly and accurately, and at greater ranges…"

Full article here
link

Amicalement
Armand

Holland also fitted pneumatic projectors to the submarines he sold to the British Admiralty as well as torpedo tubes – one of each, one above the other. Submarines already had to have air compressors and pressure tanks, plus shells were considerably smaller than torpedoes.

USN mounted these type of weapons on the USS Vesuvius which took part in Spanish American war. Very interesting application:
link

Thanks for the link my friend.

Amicalement
Armand