U-1-class submarine (Austria-Hungary)

The U-1 class was a class of two submarines or U-boats built for and operated by the Austro-Hungarian Navy (Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine). The U-1-class boats were built to an American design at the navy yard in Pola. The class was a part of the Austro-Hungarian Navy's efforts to competitively evaluate three foreign submarine designs.

The two U-1-class boats, both launched in 1909, were 100 ft long and as built were each powered by two gasoline engines while surfaced, and two electric motors when submerged. Neither boat was operational at the beginning of World War I because both were in drydock awaiting replacement diesel engines for their problematic gasoline engines.

Beginning in 1915, both boats conducted reconnaissance cruises out of either Trieste or Pola until declared obsolete in early 1918. Both remained in service as a training boats at the submarine base on Brioni, but each was at Pola at the end of the war. They were ceded to Italy as war reparations in 1920 and scrapped at Pola. Neither submarine sank any ships during the war.

Design and construction
In 1904, after allowing the navies of other countries to pioneer submarine developments, the Austro-Hungarian Navy ordered the Austrian Naval Technical Committee (MTK) to produce a submarine design. The January 1905 design developed by the MTK and other designs submitted by the public as part of a design competition were all rejected by the Navy as impracticable. They instead opted to order two submarines each of designs by Simon Lake, Germaniawerft, and John Philip Holland for a competitive evaluation. The two Lake-designed submarines comprised the U-1 class. The Navy ordered plans for the building of two boats—designated U-1 and U-2—from the Lake Torpedo Boat Company of Bridgeport, Connecticut, in 1906.

The U-1-class design had several features typical of Lake's designs, including a diving chamber under the bow and two variable pitch propellers. Lake's design also called for two retractable wheels that, in theory, could allow travel over the seabed. The design also placed the diving tanks above the waterline of the single, cylindrical hull, which necessitated a heavy ballast keel for vertical stability. The propulsion system for the U-1 class consisted of two gasoline engines for surface running and two electric motors for running while submerged. For underwater steering and maneuverability, the design featured four pairs of diving planes.

The boats were 100 ft long by 15 ft abeam and had a draft of 12 ft. As designed, each boat displaced 229.7 MT surfaced and 248.9 MT submerged. Both of the submarines had three 45 cm torpedo tubes—two in the bow, one in the stern—and could carry up to five torpedoes, but typically carried three. Each submarine was also armed with a 37 mm deck gun.

U-1 and U-2 were laid down in July 1907 at the navy yard at Pola, and were launched in February and April 1909, respectively.

Service career
Upon completion of the two boats, the Austro-Hungarian Navy evaluated the U-1 class in trials through 1910. During the trials, technical problems with the gasoline engines were revealed. Exhaust fumes and gasoline vapors frequently poisoned the air inside the boats and the engines themselves were not able reach the contracted speed. Because of the problems, the Austro-Hungarian Navy considered the engines to be unsuitable for wartime use and paid only for the hulls and armament of the two U-1 boats. While replacement diesel engines were ordered from the Austrian firm Maschinenfabrik Leobersdorf, they agreed to a lease of the gasoline engines at a fee of US$4,544 annually.

In order to dive, the diving tanks, located above the waterline, had to be flooded by pumps, which took over 14½ minutes in early tests, but which was later reduced to 8 minutes. The maximum diving depth was set at 40 m when the hulls began to show signs of stress at that depth. The four pairs of diving planes gave the boats exceptional underwater handling, and, when the boats were properly trimmed and balanced, the boats could be held within 20 cm of the desired depth. Other tests proved the underwater wheels to be useless. The U-1 class boats outperformed the U-3 (Germaniawerft) and U-5 (Holland) classes in both diving and steering capabilities in the Austro-Hungarian Navy evaluations.

Both boats were officially commissioned into the Austro-Hungarian Navy in 1911—U-1 in April, U-2 in June—and served as training boats, each making as many as ten training cruises a month. At the outbreak of World War I, U-1 and U-2 were both in drydock awaiting the installation of their new diesel engines. To accommodate the new engines, the boats were lengthened by about 11 in. These changes lowered the surface displacement to 223.0 MT but increased the submerged displacement to 277.5 MT.

From 1915, both boats conducted reconnaissance cruises out of either Trieste or Pola. In January 1918, the boats were declared obsolete, but remained in service as training boats at the submarine base at Brioni, but at the war's end both boats were in Pola, After the war, both boats were ceded to Italy as war reparations and scrapped. Neither boat sank any ships during the war.

SM U-1
U-1 was laid down at the navy yard at Pola in July 1907, launched in February 1909, and underwent trials throughout 1910. She was commissioned in April 1911 and served as a training boat through 1914. Her periscope was damaged when she was accidentally rammed by an Austro-Hungarian cruiser in January 1914. At the beginning of World War I, U-1 was not operational because she was in drydock awaiting new batteries and replacement diesel engines. When the engine swap had been completed, U-1 served as a training boat for the Austro-Hungarian Navy through October 1915. From November that same year she conducted reconnaissance cruises out of Trieste and Pola until she was declared obsolete in early 1918. U-1 remained in service as a training boat at the submarine base on Brioni, but was at Pola at the end of the war. She was awarded to Italy as a war reparation in 1920 and scrapped at Pola. U-1 did not sink any ships during the war.

SM U-2
SM U-2 was laid down at the navy yard at Pola in July 1907, launched in April 1909, and underwent trials through 1910. She was commissioned in June 1911 and served as a training boat through 1914. At the beginning of World War I, U-2 was not operational because she was in drydock awaiting replacement diesel engines. With her new engines and a new conning tower installed by June 1915, U-2 conducted reconnaissance cruises out of Trieste but was declared obsolete in early 1918. U-2 remained in service as a training boat at the submarine base on Brioni, but was at Pola at the end of the war. She was ceded to Italy as a war reparation in 1920 and scrapped at Pola. U-2 sank no ships during the war.