×
Aircraft / Aviation Vehicles & Artillery Infantry Arms Warships & Submarines Military Pay Chart (2023) Military Ranks
Advertisements
HOME
NAVAL WARFARE
MODERN FLEETS
COUNTRIES
SHIPBUILDERS
COMPARE
BY CONFLICT
BY TYPE
BY DECADE
BY CLASS
WORLD WAR 1
Naval Warfare

SM U-21 (U-XXI)


Diesel-Electric Ocean-Going Attack Submarine [ 1917 ]



SM U-21 formed the first of four U-20 class submarines in service with the Austro-Hungarian Navy during World War 1.



Authored By: Staff Writer | Last Edited: 08/01/2016 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

GO TO SPECIFICATIONS [+]
Advertisements
World War 1 (1914-1918) would mark the last recorded actions of the Austro-Hungarian Navy, a fighting force in service since 1786. In 1904 a committee was arranged to draw up plans for an indigenous submarine but it and others were passed on during a 1905 review. In the end, the service elected for an improved version of the existing German U-1 which became the U-3 for the Austro-Hungarians. From this meager beginning evolved several other submarine types prior to The Great War and all were based on foreign designs like the American C-class. With the assassination of Archduke Ferdinand in 1914 to officially begin the conflict, the Austrian-Navy was put on alert - though just six boats made up its submarine force and two of these were not even operational.

Pressed to strengthen its undersea fighting force amidst the growing war commitment, the Navy pushed for construction of a design based on the U-20-class which were built from the period spanning 1915 to 1917 and commissioned from 1916 to 1918. Four were completed including "SM U-21". Despite their generally obsolete status by the time the war arrived, any boat was better than none and local industry was charged with delivering the submarines for wartime service (construction having been split between Austrian and Hungarian firms which did not help matters much).

U-21 displaced 170 tons (long) when surfaced and 210 tons (long) when submerged. She held a length of 127.1 feet with a beam of 13 feet and a draught down to 9 feet. Power was from a combination diesel-electric propulsion system with the diesel units used for surface running and battery-driven motors for undersea running. Power from the diesel installation totaled 450 horsepower with 160 available from the electric motors. These drove a single shaft at the stern. Maximum speed was 12 knots when surfaced and 9 knots when submerged with ranges out to 1,400 nautical miles (estimated) and 23 nautical miles respectively. Internally the boat was crewed by eighteen personnel made up of officers and sailors. Armament centered on 2 x 450mm torpedo tubes in bow-facing, bow-mounted positions. Beyond this, the vessel could call upon a 66mm deck gun and an 8mm machine gun for surface attacks.

U-21 was ordered on March 27th, 1915 and saw her keel laid down shortly thereafter - such was the expediency asked of Austro-Hungarian industry to deliver viable submarines. She was launched on August 15th, 1916 and officially commissioned on August 15th, 1917. She marked the first boat of her class to enter service.

As with other Austro-Hungarian submarines of World War 1, the impact of U-21 in the conflict proved quite minimal. From the outset she was beset with self-inflicted damage owing to both her design and generally inexperienced crews. Damage forced her to be laid up early in her career and a leak ended one of her wartime patrols. During a run in July of 1918, the boat encountered an issue with her diesels and had to be towed to Pola for repairs and it was in this state that she remained until the Armistice of November 1918. Following the Austro-Hungarian surrender, U-21 was passed on to Italy as war reparations which led to the submarine being stripped of her value and ultimately scrapped in 1920.©MilitaryFactory.com
Note: The above text is EXCLUSIVE to the site www.MilitaryFactory.com. It is the product of many hours of research and work made possible with the help of contributors, veterans, insiders, and topic specialists. If you happen upon this text anywhere else on the internet or in print, please let us know at MilitaryFactory AT gmail DOT com so that we may take appropriate action against the offender / offending site and continue to protect this original work.
Advertisements

Specifications



Service Year
1917

Origin
Austria-Hungary national flag graphic
Austria-Hungary

Complement
18
PERSONNEL


Class
U-20 class
Number-in-Class
4
VESSELS
Ships-in-Class


U-20; U-21; U-22; U-23


National flag of Austria National flag of the Austro-Hungarian Empire National flag of Hungary Austria-Hungary
(OPERATORS list includes past, present, and future operators when applicable)
Submerged Attack
Traveling under the surface to search, track, and / or engage or reconnoiter areas.
Maritime Patrol
Active patroling of vital waterways and maritime areas; can also serve as local deterrence against airborne and seaborne threats.
Fleet Support
Serving in support (either firepower or material) of the main surface fleet in Blue Water environments.


Length
127.1 ft
38.74 m
Beam
13.0 ft
3.96 m
Draught
9.0 ft
2.74 m
Displacement
175
tons
Disp.Submerged
210
tons


Installed Power: 1 x Diesel engine developing 450 horsepower with 1 x Electric motor generating 160 horsepower; 1 x shaft.
Surface Speed
12.0 kts
(13.8 mph)
Submerged Speed
9.0 kts
(10.4 mph)
Range
1,399 nm
(1,610 mi | 2,591 km)


kts = knots | mph = miles-per-hour | nm = nautical miles | mi = miles | km = kilometers

1 kts = 1.15 mph | 1 nm = 1.15 mi | 1 nm = 1.85 km
2 x 450mm torpedo tubes (bow-facing); 2 x torpedo reloads
1 x 66mm deck gun
1 x 8mm Anti-Aircraft (AA) machine gun


Supported Types


Graphical image of a modern warship turreted deck gun armament
Graphical image of an aircraft medium machine gun
Graphical image of an aircraft automatic cannon
Graphical image of an aircraft aerial torpedo


(Not all weapon types may be represented in the showcase above)
None.


Military lapel ribbon for the Cold War period
Military lapel ribbon for early warship designs
Military lapel ribbon for the Falklands War
Military lapel ribbon for the 1991 Gulf War
Military lapel ribbon for the Korean War
Military lapel ribbon representing modern aircraft
Military lapel ribbon for the Attack on Pearl Harbor
Military lapel ribbon for the Russian Invasion of Ukraine
Military lapel ribbon for the Vietnam War
Military lapel ribbon for the World War 1
Military lapel ribbon for the World War 2


Ribbon graphics not necessarily indicative of actual historical campaign ribbons. Ribbons are clickable to their respective naval campaigns / operations / periods.

Images Gallery



1 / 1
Image of the SM U-21 (U-XXI)
Image from the Public Domain.


Advertisements




Disclaimer | Privacy Policy | Cookies


2023 Military Pay Chart Military Ranks DoD Dictionary Conversion Calculators Military Alphabet Code Military Map Symbols

The "Military Factory" name and MilitaryFactory.com logo are registered ® U.S. trademarks protected by all applicable domestic and international intellectual property laws. All written content, illustrations, and photography are unique to this website (unless where indicated) and not for reuse/reproduction in any form. Material presented throughout this website is for historical and entertainment value only and should not to be construed as usable for hardware restoration, maintenance, or general operation. We do not sell any of the items showcased on this site. Please direct all other inquiries to militaryfactory AT gmail.com. No A.I. was used in the generation of this content; site is 100% curated by humans.

Part of a network of sites that includes GlobalFirepower, a data-driven property used in ranking the top military powers of the world, WDMMA.org (World Directory of Modern Military Aircraft), WDMMW.org (World Directory of Modern Military Warships), SR71blackbird.org, detailing the history of the world's most iconic spyplane, and MilitaryRibbons.info, cataloguing military medals and ribbons.

View day-by-day actions of the American Civil War with CivilWarTimeline.net. View day-by-day actions of World War II with SecondWorldWarHistory.com.


©2023 www.MilitaryFactory.com • All Rights Reserved • Content ©2003-2023 (20yrs)