Argonauta class submarine (1931)

Medium Submersibles: 1929-33:
Argonauta, Fisalia, Jalea, Jantina, Medusa, Salpa, Serpente

The Argonauta class were the first sub-class of the “600 tonnes Series” considered either “medium” in Western publications and “coastal” in Italian ones. This large standardization effort (this first class comprised seven vessels, a record), built for the Regia Marina from 1929 to 1933 and named after mythological beings very much mirrores their transalpine counsins, the also called the “600 tonnes”, and were at the root for a large evolution until WW2 with the “metals” series. Some saw limited action in the Spanish Civil War of 1936–1939 and heavy action in the Mediterranea, with only one surviving the Second World War.

Jalea and Jantina out of the OTO shipyard in Muggiano (IA colored)

The 600 tonnes series

The 600-class Argonauta series were a new type of standardized coastal submarine of the Italian Royal Navy, started as an evolution of the Squalo class. Thie “600 tonnes” as they were known collectively just like the “condotierri class” cruisers, but they were far more homogeneous. They were so far the largest class of Italian submarines ever, with fifty-nine built, and probably also one of the most successful. These were produced in five series that did not differ greatly from each other: These classes were named Argonauta, Sirena, Perla, Adua, and finally Acciaio. The latter were the last and largest class with thirtheen, but the next ones, considered sufficiently different to be excluded from this series, was the Flutto class which inaugurated the first and last of the “900 tonnes”, but had 48 boats ordered in three series with only seven commissioned.

In capabilities, they were sea-going submarines, even though they were designated as coastal-types but were built for service in the Mediterranean and to to conform with interwar naval treaties, notably the 1922 Washington and 1930 London conferences, placing restrictions on the number and size of warships of various types, including submarines (that Britain wanted to ban originally). Coastal submersibles were in treaties, limited to a 600-ton surface displacement, albeit there was no limit placed on their numbers. This created an opportunity France, Italy and later Germany (with the Type VII) or even britain (with the S-class) did not wanted to miss. At the same time the Italians were creating their 600 tonners after the 1930 London conference confirmation, the French had the same series, but they started earlier, in 1925, and these boats were specifically tailored for the Mediterranean, whereas its “1500 tonnes” were intended for the Atlantic. This only underlined the more general Franco-Italian naval rivalry, largely driven by treaties, starting with an identical tonnage granted in 1922.

Sirene in Oran. The French started their “600 tonnes” right after the Washington Treaty.

However in this submarine naval arms race, providing the impetus for a sustained building programme, and led Italy having the second largest submarine fleet in the world when World War II started. The French took a different path when Italy was just started in 1929, with the “630 tonnes” after they estimated the “600 tonnes” were too cramped. More so, they will have in the end only 34 submersibles in this series versus 48 for Italy, and the first of the “630 tonnes” were named… argonaute. Most of these had ancient mythologic names as well. Even the Argentines, not submitted to any treaty, jumped in the bandwagon of the “600 tonnes” with the Italian-built Santa Fe class.

The Italian 600 tonnes are generally believed today the most successful talian submarine lineage. They performed very well in service, well-organized internally, with a robust inner hull for great depths, excellent seaworthiness, and proved maneuverable both when surfaced or submerged. Some still argued they could perhaps have been a faster when surfaced, but the type did not require top speed as priority. Next designs capitalized on this success and tried tro improve on speed, still. The sucess of the Argonauta led to the success and mass production of the “600” class, with the next ones only having minor improvements and modernizations, but essential characteristics never changed. For the Italian Navy, this was the bedrock of its Mediterranean submarine force, with nearly fifty available in 1939, and an exprort success as well: Many more were ordered by foreign navies, which appreciated the soundness of the design and excellent performances in general for a moderate tonnage.

Design of the class

The Argonauta was derived from the earlier Squalo-class submarines, but pushed to this specific tonnage, and simplified for a large production, in fact, the class was ordered from three yards, and built in two batches, for a total of seven submarines in the Argonauta series in total. Five were named after submersibles of the preceding Medusa class of 1910: Medusa, Salpa, Jantina, Fisalia, and Jalea. Serpente had originally been named “Nautilus”, like the lead vessel of the same name from 1911. They were single-hulled with external bulges and in Italian literrature of the time designated as “Sommergibile di piccola crociera”, meaning of “small cruise”. This does not definitively advocated for “medium”, nor “coastal” although the terms seems to favour the first equivalent, hence its prevalence in anglo-saxon naval literrature. They were too large to be “truly coastal” since in WWI the Germans with their UB-I type showed what a successful coastal type really can be. They displaced just 127 tonnes surfaced, 142 tonnes submerged, a far cry for the 600-tonners.

The design later rebranded as “costieri” or “coastal” submarines, was also the work of Bernardis, which maintained its solution of a simple hull with an inner pressure hull. However, experience with the Pisani class urged the addition of bulges, upper blisters below the main deck during the design phase to ensure good stability when surfaced. Thus, these boats, based on past experience, were born without any substantial issue and immediately proved successful. The bulges at waterline level were a crucial way to keep good buoyancy, with rapid-surfacing and compensation tanks also located in the double hull. The bulges contained extra fuel, in crescent-shaped section tanks, with more in the the lightweight outer hull, in the central sections.

Hull and general design

The Argonauta class displaced 660 metric tons (650 long tons) surfaced and 813 metric tons (800 long tons) submerged. They reached 61.5 meters (201 ft 9 in) long overall, for had a beam of 5.7 meters (18 ft 8 in) and draft of 4.7 meters (15 ft 5 in). Italian sources precises an exact surface tonnage of 666,56 t and underwater tonnage of 810,43 t. Details of the dimensions of the inner pressure hull in lenght and diameter are unknown. The overall design was classic still, with a ship-like bow, pointy stern, forward horizontal dive planes folding up when not in use, and a X type arrangement of aft planes and larghe rounded tail, two propellers shafts on struts. The propellers were protected by attacehement arms for the dive planes behind.

The long, flat deck followed a constant sloped downwards, appox. 2.5 lower than the prow. The deck was enlarged, sponsoned for the main gun forward of the CT. The conning tower was also classic, with an enclosed, windowed helmsman’s post followed by the bell containing the two periscopes, attack and watch and main access upper hatch, spotting deck, and pintles for the AA HMGs. The non-retractable capstans were located close to the forward dive planes position and aft close to the truss mast. The prow had a net cutter continued by a cable guard anchored on a small portico on the CT, supported by two intermediate truss masts. There was a torpedo hatch aft, and three compatrment’s deck hatches.

On that chapter, there were three main compartments, the forward Torpedo room with tubes reloaded inside, the main forward ballast tank, with the pressure hull encased in a convexe bulkhead. The pressure hull was divided into two stages, the upper one being the main living and operating quarters and the lower ones, that can be sealed from the upper one, divided into a forward and aft battery room. There were extra ballast tanks alongide the central control room. Next was the auxiliary room, enegine room for the diesels and electric engien room, separated by the main aft hatch, with the pressure hull tail ending by a concave bulkhead, and aft main ballast tank in which the two aft torpedo tubes went through. There was also a non-jettisonable flat-bottomed ballast keel below the outer hull. Their crew numbered 4 officers and 32 enlisted men.

Powerplant

For surface running, the Argonauta class were powered by two 750-brake-horsepower (559 kW) diesel engines, each driving one propeller shaft. These were CRDA diesels albeit, Tosi diesels for the boats built by the Taranto shipyard, and one FIAT and one CRDA for Medusa only, mated onto two propellers in each case. There were also two CRDA electric propulsion motors and Marelli for the units built by the Taranto shipyard.
So to resume: Jalea and Jantina had Fiat diesels and CRDA electric motors, Salpa, Serpente had Tosi diesels and Marelli electric motors.
The surface power output was 1,500 hp for a top speed of 14 knots (26 km/h; 16 mph) on trials, and a surfaced range of 2,300 miles () at max 14 knots or 4,900 at 9.5 knots, or 5,000 nautical miles (9,300 km; 5,800 mi) at 8 knots. Submerged, she had 800 hp (400-horsepower/298 kW each) for a top speed of 8 knots (15 km/h; 9.2 mph) and a range of: 7 miles at 8 knots or 110 miles (200 km; 130 mi) at 3 knots (5.6 km/h; 3.5 mph). They had an operational diving depth of 80 meters (260 ft).

Armament

The boats were armed with six 53.3-centimeter (21 inches) torpedo tubes, four in the bow and two in the stern, a classic arrangement inherited from the Squalo class and others before it. For these tubes, they carried a total of 12 torpedoes, less the six already pre-loaded, leaving six in reserve, two aft, four forward. They were also armed with a single 102-millimeter (4 in) deck gun forward of the conning tower for surface engagements. Their anti-aircraft armament consisted of two single 13.2-millimeter Breda 76 caliber (0.52 in) machine guns.

Cannone da 100/35 Mod. 1914 (Fitted in 1940)

This Schneider-Armstrong 1914-15 was fitted at completion, but replaced by the modello 1938 as soon as it was available. Real caliber was 102 mm so exactly 4-inches as they derived from a British design with some French input, but built by OTO under licence.

Specs 100 mm/35 (3.9″) Model 1914

Weight 1,220 kg (2,690 lb), barrel 3.73 m (12 ft 3 in) 35 Caliber
Shell: 15 kg (33 lb) 102 x 649mm R 102 mm (4 in)
Breech: Vertical sliding block
Elevation: -5° to +45°
Rate of fire; 7 rpm
Muzzle velocity: 755 m/s (2,480 ft/s)
Effective range: 11.7 km (7.3 mi) at +45°

Cannone da 100/47 Mod. 1938

Placed on the forward deck, on a raised platform or bandstand well integrated into the hull, acting as wave breaker, to avoid sea spray. This 100 mm/47 (3.9″) Modello 1938 benefited from developments and improvements made on the earlier Modello 1928, specifically intended for submarines but also used on a few auxiliary vessels, all manufactured by OTO. The Modello 1931, 1935 and 1938 for Submarines were present on the the Glauco, Marcello, Cappellini, Argonauta, Marconi, Cagni, Sirena, Perla, Adua, Argo, Acciaio and Flutto classes.

Specs

Gun Length oa: 194.5 in (4.940 m), 8-10 rpm.
Fixed Ammunition (HE) 30.4 lbs. (13.8 kg) 2,756 fps (840 mps)
Range: 35° 13,800 yards (12,600 m), OTO 1932
Weight 4.6 tons (4.7 mt) -5 /+32 or 35°.
To compare the previous Cannone da 100/43 modello 1927 had the following specs:
170 in (4.300 m) long, 8-10 rom. HE shells: 30.4 lbs. (13.8 kg), muzzle Velocity 2,625 fps (800 mps)
Elevation -5/+35°. Range: 30.4 lbs. (13.8 kg) HE Elevation/35° 12,000 yards (11,000 m).

AA: 2×2 Breda Breda Mod. 31

The anti-aircraft defence counted on two twin Breda M1931 13.2 mm L/76 heavy machine guns, placed aft of the conning tower. Each mount weighed 695 kg, but ensured an elevation of -10° to 90°. They fired 125 g unitary rounds, with a muzzle velocity of 790 m/s, maximum range of 6,000 meters and effective range of 2,000 meters. Their rate of fire was 500 rounds/min, so 2000 rounds when both twin mounts fired in concert, however.

12x 533 mm (21 inches) torpedoes

Models available in 1932:
-W 270/533.4 x 7.2 Veloce: 1,700 kg, 7.2 m WH 270 kg, 3,000-4,000 m/50 knots or 12,000 m/30 knots.
-W 270/533.4 x 7.2 “F”: 1,550 kg, 6.500 m, WH 250 kg, speed 3,000 m/43 knots or 10,000 m/28 knots
-W 250/533.4 x 6.5: 1,550 kg, 7.200 m, WH 270 kg, 4,000 m/48 knots or 12,000 m/30 knots.
-Si 270/533.4 x 7.2 “I”: 1,700 kg, 7.2 m, WH 270 kg, speed 3 km/42 kts or 7 km/32 kts, 9,2km/30 knots, 12km/26 kts
-W 250/533.4 x 6.72: 7.2m, WH 270 kg speed 4km/49 kts or 8km/38 kts.
-Si 270/533.4 x 7.2 “M”: 1,7 ton, 7.2 m, WH 270 kg speed 4km/46 kts, 8km/35 kts or 12km/29 kts.
They were also given also a pair of hydrophones.

⚙ specifications
Displacement	660 t (650 long tons) surfaced, 813 t (800 long tons) submerged
Dimensions	61.5 x 5.7 x 4.7 (202 ft x 18 ft 8 in x 15 ft 5 in)
Propulsion	2 shafts diesel-electric 1,500 bhp (1,100 kW)/800 hp (600 kW)
Speed	14 knots (26 km/h; 16 mph) surfaced, 8 knots (15 km/h; 9.2 mph) submerged
Range	5,000 nmi at 8 knots surfaced, 110 nmi at 3 knots submerged
Armament	102 mm (4 in) deck gun, 2× 13.2 mm AA, 6× 533 mm TTs (4 bow, 2 stern)
Depth	80 m (260 ft)
Sensors	Hydrophones
Crew	44 Officers and Ratings

Career of The Argonauta Class

This class sufferred heavy losses: Argonauta was sunk on 28 June 1940 off Sicily by British aircraft. Salpa was sunk on 27 June 1941 in Mediterranean, torpedoed by the T class British submarine HMS Triumph. Jantina was sunk on 5 July 1941 in the Aegean sea by another T-class British submarine, HMS Torbay. Fisalia was sunk on 28 sept. 1941 near Yaffa, depht-charged by the British Flower-class corvette HMS Hyacinth. Medusa was sunk on 30 January 1942 in the Adriatic sea, by the T-class British submarine HMS Thorn. Notice that 3/4 of the class were lost until early 1942, and half bt yhe British ocenanic T-class, initially planned for the Pacific, but that found Mediterranean waters a fertile hunting ground, well served by their massive bow torpedo “hand”. Serpente was the first exception, she escaped destruction only to be scuttled by her crew on 12 Sept. 1943 (just after the armistice) near Ancona to avoid German capture. Only one survived the war, saw a quiet co-belligerence service and was disposed off postwar.

Argonauta (1931)

Argonauta was laid down at CRDA (Cantieri Riuniti dell’Adriatico), Monfalcone on November 1929, launched on 19 January 1931 and completed, commissioned on 1 January 1932. In June 1940, she was attacked by anti-submarines off Alexandria, Egypt, suffering serious damage forcing her back to Tobruk. On June 27, she left Tobruk for Taranto, to be repaired. Nothing more was heard of her. There are two competing hypothesis about her loss: Two anti-submarine actions most likely led to her sinking like a a depth charge attack carried out around 2.00 PM in the afternoon on June 29, by HMS Dainty, Defender, and Ilex (at 35°16′ N and 20°20′ E.). The other possible was a Short Sunderland flying boat, 50 minutes later, against her at periscope depth, at 37°29′ N and 19°51′ E. The entire crew, under commander Vittorio Cavicchia Scalamonti (5 officers, 43 petty officers and sailors) went down with her.

Fisalia (1931)

Fisalia was laid down at CRDA, Monfalcone in november 1929, launched on 2 May 1931 and entered service on 5 June 1932. On 2 June 1940, she spotted a merchantman off Alexandria, but was unable to attack. Three days later while returning to base, she dodged a torpedo launched by an unknown enemy submarine. On 12 July, she was depth-charged by three British ships off the coast of Libya, suffering serious damage, forcing her to return to port. Between October 1940 and March 1941, she was withdrawn from offensive patrols and kept for training, making 46 of such missions for the Pola Submarine School in the Adriatic. On 23 September 1941, she resumed offensive patrols, departing Leros for an ambush area between Jaffa and Haifa, but never returned. It is establushed today she was sunk on 28 September 1941 by the corvette HMS Hyacinth about 25 miles northwest of Jaffa, with all hands, including Commander Girolamo Acunto.

Jalea (1932)

Jalea and Jantina out of the OTO shipyard in Muggiano

Jalea was orderered from, and laid down at OTO (Odero Terni Orlando) shipyards Muggiano in January 1930, launched on 15 June 1932, and commissioned on 16 March 1933. Like ehr sisters she took part clandestinely in the Spanish war, sinking suspected Republican arms summglers, notably from thre USSR. On 26 December 1936 for example she attacked the Spanish cargo ship “Villa de Madrid” with two torpedoes, but missed. However as it happened close to shore, one of the torpedoes ended up on a nearby beach. It was retrieved b the Republicans, which revealing the active participation of Italian submarines in the war. On 12 August 1937, she launched two torpedoes against the Spanish destroyers Churruca and Alcalà Galliano. Churruca was hit but she survived thankls to her bulkheads, towed to safety and repaired. At the start of the Second World War she was deployed in the eastern Mediterranean. From March 1941, she was assigned to the Submarine School in Pola, retired from the frontline and multiplying training cruises in the Adriatic. At the armistice, she was handed over to the Allies in Malta. During the co-belligerence, she, like others Italians subs in the same situation, was used a target in allies anti-submarine exercises remote from the frontline like the Balearic islands and azores. Thus, she became the only one in class to survive the war. On 1 February 1948 she was decommissioned and sold for BU.

Jantina (1932)

Jalea and Jantina out of the OTO shipyard in Muggiano

Jantina had been ordered from OTO (Odero Terni Orlando), Muggiano shipyatd in January 1930. She was launched on 16 May 1932 and commissioned on 1 March 1933. With other Italian submarines in class, she clandestinely took part in the Spanish Civil War, but made no kill. On 27 June 1940 as the war started, she launched a torpedo against a British destroyer and reported an explosion. However the latter was not alone and she was hunted down for two full days, depth charges many times. She survived but badly damaged and had to return to Leros for provisional repeairs, departing on 5 July, towards Brindisi for full repairs. However she was ambushed underway, spotted by the British submarine HMS Torbay, which launched six torpedoes. Hit by one or two, she sank in less than a minute off Mykonos, with all except 6 men in the conning tower (she was surfaced at the time) on 5 July 1941.

Medusa (1931)

Medusa was ordered from CRDA, Monfalcone in November 1929. She was launched on 10 December 1931, and was commissioned on 5 June 1932. When WW2 was well engaged, she had carried out ten war patrols without kill. The was then assigned given her age by March 1941, to the Submarine School in Pola. While returning from a training mission off the coast of Carnaro on 30 January 1942, she was spotted by the submarine HMS Thorn, launching four torpedoes. Commander Enrico Bertarelli’s promt reactions allowed her to avoid three, but the fourth hit her, and she sank rapidly: Of the 60 men on board, only three in the conning tower were thrown into the water and survived, after being and rescued by the steamer Carlo Zeno. Four other men in the same CT were killed ouright in the detonation or drown. Commander Bertarelli was among these. Wounded, he went to the bottom while trying to save his me. 14 remained trapped, alive, in a stern compartment however as there was enough buoyancy remaining.

Rescue attempts were hindered by bad weather and the pontoons and diving boats were forced to return. The submarine Otaria, which was pumping air to the Medusa, was the last to return in the evening of 1 February, condemning the survivors to suffocate. On 4 February, when operations reumed, there was none to save. On 15 June 1943 the two sections of the submarine were recovered, bodies were extracted. However a piece of the stern, 25 metres long, sank again after the cable snapped. It is still on the seabed today.

Salpa (1932)

Salpa was ordered from Tosi, Taranto in and laid down on 23 April 1930, launched on 8 May 1932 and commissioned on 12 December. On 29 June 1940 in WW2 she was depth charged during one of her missions, suffering heavy damage, forced to return to Benghazi and from there, to Taranto for full repairs. On 3 February 1941 she was again detected and a long hunt started for hours, causing further damage. In the end, if she survived, this had been of such severity she was forced to return again. On 27 June, after more patrols, she was spotted and attacked by night, by gunfire, from the submarine HMS Triumph and hit several times, then by a torpedo. She sank rapidly, taking with her commander Renato Guagno and the entire crew.

Serpente (ex-Nautilus) 1932

Serpente was initially ordered as Nautilus from Tosi, Taranto and laid down on 30 April 1930. She was initially in 1931 renamed Serpente and launched on 28 February 1932, commissioned on 12 November. On 1 October 1940 she was depth charged and damaged in one of her patrols. On 20 December, she spotted and launched torpedoes against a group of British cruisers and destroyers, reporting an explosion. Postwar reports showed she was likely HMS Hyperion (H class destroyer) which was actually badly damaged, so much so she it had to be abandoned, scuttled by torpedoes from HMS Janus. Others reported it was unlikely to be Serpente, but a mine laid by Italian destroyers previously in the same sector. On 29 September 1941 she took part in an attempt to stop Operation “Halberd”. She spotted and launched two torpedoes against one of the four destroyers escorting a battleship, reported a detonation. But postwar it was believed this was the explosion of depth charges launched by HMS Legion and Lively. No torpedop damage was reported that day. On 4 May 1942, she was assigned to the Submarine School in Pola and carried out 105 training missions. At the armistice, she left Pola for Ancona. She departed again on 12 September 1943 for Taranto, towing the midget submarine CB.12. However the towing cable snapped, but CB.12 had a crew onboard and managed to continue on her own, and reached Taranto in turn, only to be, like Serpente, scuttled on 12 September. The crew was carried by a fishing boat and disembarked in Civitanova.

Argonauta class submarine (1931)

The 600 tonnes series