Dynamite Guns: Brilliant Technical Dead-Ends!

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.

Credit for proving the concept went to a Mr.D.M.Melford of Toledo, Ohio, who demonstrated a 2-inch prototype to the US Military in 1884, firing a 5-pound solid shot over half-a-mile and driving it through a 26-inch thick concrete target. Mefford seems to have faded from the scene thereafter but one of the observers at the trial, an artillery lieutenant called Edmund Zalinski picked up the idea and formed the “pneumatic Dynamite gun Company”. By 1885 Zalinski had an operational prototype with an 8-inch bore which could fire a projectile with a 100 pound dynamite charge over two miles. The projector was at least as accurate as conventional cannon of the same calibre and, though the range was less, could carry a much larger explosive charge,

The US Navy was now interested – not least because such weapons could be mounted in smaller, lighter ships. A test in 1887 completely destroyed a target ship and the publicity this got led to the decision to build a "dynamite cruiser" armed with three such weapons. Zalinski, by now US Naval attaché to Russia, returned to supervise development of these projectors as well as the construction of similar ones for mounting in coastal-defence fortifications.

The Vesuvius– an unarmoured  246 ft, 930 ton vessel, with two 2200 hp engines giving her a top speed of 21 knots – was fitted with three fixed 15-inch bore projectors. To aim them the entire ship needed to be aimed at the target –this was to prove the main operational drawback – and range was varied by adjusting air pressure. They offered the capability of hurling quarter-ton dynamite charges up to a mile, while with a reduced charge of 200 lbs the respectable range of two and a half miles was achievable. In one test fifteen projectiles were fired by the Vesuvius in just over sixteen minutes.  The projectiles themselves looked like huge darts, with sheet meal tails carried on an extensions behind the charge proper, the fins being angled to as to impart a spin – and stability – in flight. Once the projectile had dropped into the water, and had begun to sink, salt-covered fuses were exposed which, when fully exposed to sea-water, completed an electric circuit and detonated the charge.

Despite extensive trials, which revealed many operational problems,  the Vesuviusdid not enter active service until the Spanish-American War in 1898. She was to bombard a Spanish fortification at Santiago, Cuba, but the results, though visually spectacular, seem to have been meagre, doing little more than plough up the fort’s glacis. She was converted to a torpedo-trials vessel thereafter (an ironic fate, in that the Zalinski guns once had once promised to replace the torpedo) and, with her pneumatic projectors removed, she lasted to 1922.

One other Zalinski gun was mounted on a warship. This was a single 15-inch unit mounted on a Brazilian auxiliary cruiser, the Nictheroy, a 7080-ton (displacement) Brazilian auxiliary cruiser. She was originally a coastal passenger and cargo operated under the name El Cid by the Morgan Lines company. Faced with a large-scale naval mutiny in 1894, the Brazilian government looked frantically for ships overseas, bought El Cid, and had a Zalinski weapons similar to those of the Vesuviusinstalled. Though she reached Brazil the mutiny was suppressed without the Nictheroy needing to open fire. She was purchased back by the US Navy at the time of the Spanish-American War and had a worthy career thereafter in various support roles as the USS Buffalo. She was sold in 1927.

15-inch Zalinski guns were also evaluated by the US Army’s coastal artillery, offering enough promise for two such weapons, and a small 8-inch gun, to be mounted Fort Hancock, New Jersey, in 1894. These were regarded as sufficiently successful for three more 15-inch guns to be located at San Francisco in 1898 to protect the Golden Gate, followed by individual weapons at  Hilton Head, South Carolina and Fishers Island, New York.  in 1901. By then they were being made obsolete by the development of more stable explosives – such as cordite – which were stable enough to be fired from conventional guns over much greater ranges. All US Army batteries were scrapped well before WW1.

The concept still had sufficient promised for John Phillip Holland, built two 8.4-inch Zalinski guns into the first commissioned US submarine USS Holland (SS-1), no doubt remembering his first attempt to do so in the early 1880s. They were however removed afterwards.

One other pneumatic gun was to enter service. This was the bizarre Sims-Dudley gun for use as mobile field artillery. This duty precluded use of steam-driven compressors, as installed on ships or at fixed shore batteries. Instead, a separate cylinder was placed below the projector tube and a smokeless-powder charge was detonated in it to send compressed air – presumably on the other side of a piston, to the launching tube. This seems to have been an example of having the worst of both worlds in design terms, and the age-old principle of Occams’s Razor, as valid in technology as in philosophy, must have been unknown to the inventors. Despite this the US Army bought sixteen of these guns, firing 2.5 inch calibre, 10-pound projectiles with 5-pound bursting charges. The projectiles seem to have been smaller versions of the Zalinski missiles, as shown in teh illustration below.

Colonel Theodore Roosevelt and his Rough Riders used a Sims-Dudley gun during the siege of Santiago. Its greatest advantage appears to have been its lack of a loud report and the fact that its smokeless-power charges did not reveal the weapon’s location to the enemy. It seems however to have been mechanically unreliable. The Sims-Dudley faded from history afterwards – probably deservedly so!

Though considerable ingenuity was expended in making pneumatic guns work, and though the American Government was prepared to invest large sums in their development, they ultimately represented one of history’s technological dead-ends. The advent of more stable explosives, and of longer-ranged and faster torpedoes, quickly sidelined them. Pneumatic guns do not however deserve to be forgotten, and for me, in Britannia’s Shark, it has been a delight to write about the period when they still held such promise.

Britannia's Shark

Click on the image below to learn more about Britannia's Shark. This will allow you to read the opening chapters - including the testing of a pneumatic gun.