''Röthelstein'' is an

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

n river icebreaker owned by Verbund AG. She is used to break ice and push barges on the

Danube The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...

river. Built by Kværner Masa-Yards in

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

in 1995, she was the first new vessel to be fitted with

Azipod Azipod is a trademarked azimuth thruster pod design, a marine propulsion unit consisting of a fixed pitch propeller mounted on a steerable gondola ("pod") containing the electric motor driving the propeller, allowing ships to be more maneuverab ...

propulsion units.

History

In early 1994, Kværner Masa-Yards signed a contract worth about $4.3 million for the construction of a shallow-draft river icebreaker for the Austrian power company Österreichische Donaukraftwerke AG (today Verbund AG). The vessel would be fitted with a new type of propulsion system and, following extensive development work carried out by the shipyard's Arctic Research Centre, feature high icebreaking capability despite its small size and shallow draft.Kvaerner Builds Diesel-Electric Icebreaker, Renovates Russian Vessel
Maritime Reporter/Engineering News, February 1994, page 39. Instead of being launched from a slipway or floated out from a dry dock, the 400-ton vessel was lowered to the water using the shipyard's cranes in late 1994. She was given the name ''Röthelstein'' after a municipality of the same name. During sea trials in the northern

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...

in February 1994, ''Röthelstein'' achieved a speed of in open water and, using the azimuthing propulsion units, demonstrated ability to turn on the spot. In full scale ice trials in the

Gulf of Bothnia The Gulf of Bothnia (; ; ) is divided into the Bothnian Bay and the Bothnian Sea, and it is the northernmost arm of the Baltic Sea, between Finland's west coast ( East Bothnia) and the northern part of Sweden's east coast ( West Bothnia an ...

, the river icebreaker was successfully tested in level ice up to thick.

Ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...

penetration tests showed that ''Röthelstein'' could overcome ridges varying between in thickness when the icebreaker proceeded in astern direction and utilized the pulling-type azimuth thrusters to break up the ridge. This was one of the first demonstrations of the

double acting ship A double acting ship is a type of icebreaking ship designed to travel forwards in open water and thin ice, but turn around and proceed astern (backwards) in heavy ice conditions. In this way, the ship can operate independently in severe ice cond ...

principle. After the trials, ''Röthelstein'' sailed through the Rhine–Main–Danube Canal flying the Finnish flag. She was delivered to the owner in the port of Ybbs an der Donau in April 1995. Since then, ''Röthelstein'' has been in service on the Danube River.

Design

''Röthelstein'' is long and has a beam of . Her normal operating draft is , which results in a displacement of about 400 tonnes, but in shallow waters the draft can be reduced to only . The hull form follows the design of very shallow draft river icebreakers with a wide cylindrical bow similar to those found in

landing craft Landing craft are small and medium seagoing watercraft, such as boats and barges, used to convey a landing force (infantry and vehicles) from the sea to the shore during an amphibious assault. The term excludes landing ships, which are larger. ...

s. The low-profile deckhouse is only highDiesel-Electric Icebreaker Röthelstein Launched At Kvaerner's Helsinki Yard
Maritime Reporter, December 1994, page 24. and provides accommodation for up to ten people, but normally the vessel carried a crew of three. ''Röthelstein'' has a diesel-electric propulsion system consisting of two

Caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

3508 DITA generating sets, each producing 700kW, and two 560kW ABB

VI0760A propulsion units with stainless steel propellers.References - Propulsion Products
ABB. Following retrofits to two existing vessels, the newly built ''Röthelstein'' was only the third vessel ever to be fitted with an electric podded propulsion system where the propulsion motors driving the propellers are located inside steerable gondolas. She was also the first vessel with Azipod units in pulling configuration where the propellers are facing forwards to improve efficiency and icebreaking performance.Experience with Azipod propulsion systems on board marine vessels
ABB Review 2/1999.

References

{{DEFAULTSORT:Rothelstein (icebreaker) Icebreakers of Austria 1994 ships Ships built in Helsinki Ships of Austria