Thank you to an unnamed source. Any errors or incorrect assumptions are purely my responsibility however
The Sagittaire was an innovative midget submarine design from French submarine builder Comex Industries. The 200 ton submarine came in two versions; a Special Forces Diver Intervention (DI) model and the torpedo armed Coastal Defense (D) version.
Artist’s impression of a Sagittaire launching an SDV. Based on original Comex sketch.
It was proposed in the mid-1980s as a solution to both inshore defense and Special Forces support. Uniquely, it featured an SDV hangar in the bow which could carry two Comex designed two-man SDVs (Swimmer Delivery Vehicles). The hangar was constantly flooded, even when the submarine was surfaced. Carrying SDVs below the waterline is not unusual for midget subs of this generation but the streamlined internal hangar is unique – they are normally carried externally on the sides of the sub. The divers entered the hangar from a moon-pool hatch, directly from a divers support section of the boat which most likely also functioned as a decompression chamber. Comex were involve in Saturation Diving so it is possible that it could be kept at higher atmospheric pressure for extended periods also. Behind the control compartment the submarine switches to double-hull construction with crew berthing and the engine / machinery space aft.
Schematic of the Divers Intervention (DI) version with unique SDV hangar in the bow.
The Sagittaire CD (Coastal Defense) version replaced the SDVs with up to four torpedo tubes. Internal layout was identical except that without the divers, the forward accommodation was used by an enlarged crew instead.
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Comex entered the submersibles business with a technology transfer from British military / civilian SDV manufacturer Marex around 1970. Their first wet sub was the jointly developed Total Sub 01 which was used in the oil industry. From there on all the built subs have been for the civilian market. They have built a total of 23 submersibles of various types including large tourist submarines. Their military designs are virtually unheard of however.
<- Comex Globule two-man dry sub. Photo: David Crochet.
Comex Remora 2000 with acrylic spheres cabin. ->
More relevantly, Comex also built and operate the long range 300 ton SAGA research submarine which has a diver lock-out capability and can dive to 600m (2,000ft). It was originally intended to have a nuclear power plant for under-ice operation but was built with diesels and Air Independent Power (AIP) using Stirling engines.Fantastic photos and information at lescompagnonsdusaga.org
Some images from lescompagnonsdusaga.org/:
Marex Type-A (A2, A4, A5, Comex Total-Sub-01) SDVs
Soviet Project 1015 'SPLC' Special Purpose midget submarine
Maritalia GST-23+ Midget Submarine
Piranha Class (LOSOS)midget sub
MSV-75 midget sub design
HDS-500 Midget Submarine
Crocodile 250 Midget Submarine
Iranian Nahang Class midget sub