During the latter half of the 1920s, the French Navy placed its mine-laying duties in the hands of the six-strong Saphir-class submarines. The vessels appeared during the span of 1925 into 1929 and was designed primarily for operations in Mediterranean waters. If France were to go to war with one of its European neighbors, the Mediterranean waterways would prove crucial to its survival.
The boats in the class were designated Diamant, Nautilus, Perle, Rubis, Saphir and Turguoise. As the war progressed, though not in favor of France, the Nautilus, Saphir and Turquoise were all captured at Bizerta while Diamant was scuttled at Toulon to avoid capture. The Perle eventually fought under the Free French banner during most of the war but was eventually lost to a British air attack on July 8th, 1944 which abruptly (and accidentally) ended her career. Of the class, only Rubis enjoyed a complete war time service career for its host nation.
She was built by Arsenal de Toulon and saw her keel was laid down on April 3rd, 1929 with launching occurring on September 30th, 1931. Her formal commissioning was had on April 4th, 1933.
As designed, Rubis was given a displacement of 760 tons when surfaced and showcased 925 tons when submerged. She featured a length of 216 feet with a beam measuring 23.4 feet and a draught of 14 feet. Propulsion was served through 2 x diesel engines developing 1,300 horsepower to two shafts. The diesels powered the vessel on the surface. Submerged propulsion was therefore handled by 2 x electric motors developing 1,100 horsepower. Consistent with submarines of the period, Rubis required surfacing to recharge her battery supply and take on fresh oxygen for the crew. Her crew totaled between 40 and 43 personnel with at least three officers. Maximum speed was 12 knots when surfaced and 9 knots when submerged. Endurance was limited to 8,060 miles surfaced and approximately 90 miles submerged. Armament included some 32 naval mines in her hold. She was also outfitted with 3 x 550mm (21.65") torpedo tubes backed by 2 x 400mm (15.75") torpedo tubes which allowed her to engage surface vessels in a more traditional, direct way. Surface warfare was also strengthened by 1 x 75mm (2.95") deck gun ahead f the sail and a twin-barreled 13mm anti-aircraft machine gun installation aft of the tower. Her overall profile included a boat-like bow projection, tapered stern, a flat surface deck and centrally-located sail. Dive planes were fitted forward and low along the hull sides. The rudder control system was fitted aft of the propellers for maximum agility.
In April of 1940, Rubis served with the British Home Fleet and utilized her mine-laying effectiveness in waters off the coast of Norway during the Norway Campaign (April 9th, 1940 - June 10th, 1940). The vessel ended up becoming the most successful boat in the Saphir-class as she completed no fewer than twenty-two successful mine-laying sorties during her tenure at sea. Additionally, she claimed a few vessels through her torpedo armament with a war record including 15 total vessels of which five were dedicated enemy warship types. As a disruptor of enemy shipping, the Rubis proved her design a success.
With her useful sailing days behind her, FS Rubis was struck from the Naval Register on October 4th, 1949 and ultimately ordered scuttled on January 31st, 1958 to be used as a sonar "target".