French submarine Plongeur

The French submarine Plongeur, 1863.
History
France
Name:	Plongeur
Operator:	French Navy
Ordered:	1859
Builder:	Arsenal de Rochefort
Laid down:	1 June 1860
Launched:	16 April 1863
Struck:	2 February 1872
General characteristics
Displacement:	381 t (420 tons) in displacement
Length:	45 m (146 ft)
Beam:	3.7 m (12 ft)
Propulsion:	Compressed air engine with 53 m³ (1,872 ft³) of compressed air at 12.5 bar (1.25 MPa, 180 psi).
Speed:	4 kn (7.2 km/h)
Range:	5 nmi (9 km)
Test depth:	10 metres
Complement:	12
Armament:	Spar torpedo

Plongeur (French for "Diver") was a French submarine launched on 16 April 1863. She was the first submarine in the world to be propelled by mechanical (rather than human) power.

Captain Siméon Bourgeois, who made the plans, and naval constructor Charles Brun began working on the design in 1859 at Rochefort.

In 1859 the Conseil des Travaux called naval engineers for designs for a submarine and reviewed three, choosing that submitted by Siméon Bourgeois (later Admiral) and Charles Brun, naming the project Plongeur with the code name Q00.

The submarine used a compressed-air engine, propelled by stored compressed air powering a reciprocating engine. The air was contained in 23 tanks holding air at 12.5 bar (1.25 MPa, 180 psi), taking up a huge amount of space (153 m³/5,403 ft³), and requiring the submarine to be of unprecedented size. The engine had a power of 60 kW (80 hp), and could propel the submarine for 5 nmi (9 km), at a speed of 4 kn (7.2 km/h).

Compressed air was also used to empty its ballast tanks, which had a volume of 53 m³ (1,872 ft³). Ballast was 212 t (234 tons), including a security ballast of 34 t (37 tons).

The submarine was armed with a ram to break holes in the hull of enemy ships, and an electrically fired spar torpedo, fixed at the end of a pole though later, Admiral Bourgois who was, after 1871, chairman of the Commission on Submarine Defences opposed to the use of torpedoes as the primary weapon in commerce warfare.