Anti-Invasion Floating Mortar

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Name: Anti-Invasion Floating Mortar
In service: Never built
General characteristics (as designed)
Length: 80 ft (24 m)
Beam: 30 ft (9.1 m)
Propulsion: Steam engine, single screw
Speed: More than 10 knots (19 km/h; 12 mph)
Armament: Explosive-filled ram
Armour: 10 ft (3.0 m)

Also known as Naysmyth's Submarine Mortar and the Steam Ram, the Anti-Invasion Floating Hammer was a semi-submerged naval ship design conceived and published by inventor James Nasmyth in 1853.[1] The mortar had a length of 80 feet (24 m) and a beam of 30 feet (9.1 m) and was equipped with a small steam engine that drove a single propeller. The walls of the mortar were 10 feet (3.0 m) thick, protecting it against potential enemy gunfire of that period.[2] At the front of the boat was a hollow brass cap shaped like a ram that was 9 feet thick. Inside the ram was a case filled with a heavy charge of explosive powder. With only the funnel and a domed structure covering the pilot being visible above water, the mortar sought to attack enemy ships by ramming the hull with the explosive-filled ram at speeds of over 10 knots (19 km/h; 12 mph).[3] Because of potential dangers associated with its means of attack, the Anti-Invasion Floating Mortar was never built.

See also[edit]


  1. ^ Smiles, Samuel, ed. (1912). James Nasmyth Engineer: An Autobiography. London: John Murray. 
  2. ^ Jackson, G. Gibbard (1930). The Romance of the Submarine. Philadelphia: J. B. Lippincott & Co. 
  3. ^ Newbolt, Henry (1918). A Note on the History of Submarine War. London: Longmans, Green & Co. p. 11. Retrieved 26 June 2012.