SP-350 Denise

Career (France)
Launched:	1959
General characteristics
Displacement:	3.8 tonnes
Length:	2.75 metres
Beam:	2.75 metres
Draught:	1.5 metre
Propulsion:	Electric water jet
Speed:	1 knot
Endurance:	96 hours (one person)
Test depth:	1000 metres
Complement:	2

The SP-350 Denise, famous as the "Diving saucer" (Soucoupe plongeante), is a small submarine designed to hold two people, and is capable of exploring depths of up to 400 metres. It was invented by Jacques-Yves Cousteau and engineer Jean Mollard at the French Centre for Undersea Research.

Its propulsion consists of steerable, electrically powered water jets, allowing it to navigate in all directions, as well as turn about on its vertical axis. The crew members enter the craft through a hatch on the top of the hull and lie prone side-by-side on mattresses to operate it, watching their surroundings through tilted portholes that let them come within a few centimeters of their subject. Electric lamps are fitted for night diving and to provide illumination for photography at extreme working depths. An electrically operated manipulator arm can be fitted at the front of the craft so that objects can be picked up and examined through the portholes.

The steel pressure hull, nearly circular in plan form, is two meters in diameter and 1.43 meters high, able to resist a pressure of more than 90 kg per square centimeter, equivalent to a depth of nearly 900 meters, although dives never exceed 300 meters for safety.

Despite having positive buoyancy, the SP350 is weighted to negative buoyancy with ballast weights that can be jettisoned in an emergency. To correct the attitude of the hull, the pilot can shift a liquid mercury ballast mass.

If the craft is within 100 meters of the surface, the crew can abandon it via the top hatch, provided they are equipped with emergency breathing apparatus.

Launching and recovery is accomplished with the assistance of a shipboard crane.

Bibliography

• Manned Submersibles R. Frank Busby General Books (2010) ISBN 9781154776898

External links

• Manned Submersibles, by R. Frank Busby
• Hospital Ship Britannic Diving Equipment
• (Italian) Soucoupe plongeante - SP300 drawing of the diving saucer^{[dead link]}