Strait of Hormuz

Assessing the threat to oil flows through the Strait

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	A Russian-built, Kilo-class diesel submarine recently purchased by Iran, is towed by a support vessel in this photograph taken in the central Mediterranean Sea during the week of December 23.  The submarine and the support ship arrived at Port Said, Egypt, on Tuesday and were expected to begin transiting the Suez Canal today, Jan. 2, 1996.  Ships and aircraft from the U.S. NavyÕs Sixth Fleet are tracking the submarine, which has been making the transit on the surface.  This is the third Kilo-class submarine the Iranians have purchased from Moscow.  DoD photo

Source: http://www.defenselink.mil/photos/newsphoto.aspx?newsphotoid=529

Caption: Picture of a Russian-built, Kilo-class submarine, purchased by Iran in 1996

Kilo Submarines

Kilo submarines also face some difficult constraints on their ability to operate in the Persian Gulf. Fast currents make them difficult to control in some areas, notably near the Strait. Moreover, their minimum operational depth is about 150 feet, which limits their flexibility: the Strait and the Persian Gulf have a lot of water that is "deep" compared to the draft of even very large surface ships but that is "shallow" for a submarine.

The Kilo-class submarine is equipped with six 21-inch diameter torpedo tubes and can carry a total of 18 torpedoes (six in the tubes and 12 reloads in the torpedo room) of various types, including wake-homing torpedoes.[v] In lieu of torpedoes, the Kilo submarine can carry 24 mines or (possibly in the future) submarine-launched anti-ship cruise missiles (ASCMs). [vi]

Kilos use a combination of electrical and diesel power for propulsion - generally electrical power when submerged and diesel power when surfaced and for charging their batteries. Because the submarine must surface to re-charge, the charging time, speed while submerged, and the overall capacity of the batteries determine its submerged transit distance.[vii] This trade-off between snorkeling and submerged operation is referred to as the indiscretion ratio.[viii] This indiscretion ratio limits Iran's capabilities to carry out its covert missions, but not too much, because travel distances in the Persian Gulf are relatively short.

Countermeasures

While submarines are extremely effective in naval warfare, they are not invincible. Submarine detection is the first element in countering an attack by a submarine. The different types of submarine detention mechanisms include Radio intercept, Radar, Sonar, and Magnetic Anomaly Detection.

Once the submarine has been detected, the second element is destroying the submarine. This can be done using gunfire, missiles, torpedoesmines, depth charges and anti-submarine mortars. Although tankers do not carry countermeasures against submarines, U.S. Navy combatants deployed in the Persian Gulf do.

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PACIFIC MISSLIE RANGE FACILITY, BARKING SANDS, KAUAI (July 08, 2001) - The Republic of Korea submarine Nadaeyung (SS 069) surfaces after launching it Harpoon anti-ship missile (AGM-84) at the decommissioned ship White Plains (AFS 4) during a SINKEX, during RIMPAC 2002.  A SINKEX gives units an opportunity to launch live ordnance, for many of the participating countries it is the only opportunity they will get all year.  Rim of the Pacific (RIMPAC) is the largest maritime exercise in the Asia-Pacific region bringing together military forces from eight different nations (Canada, Chile, Peru, Australia, Japan, the Republic of Korea, the United Kingdom and the United States).   This year's event is the 18th in a series of RIMPAC training exercises bringing together over 30 ships, 24 aircraft, 11,000 Sailors Airmen, Marines, Soldiers and Coastguardsmen.  The purpose of RIMPAC is to enhance international relations and promote stability in the Pacific Rim region for the benefit of all participating nations.  Official US Navy photo by PH3(AW) Michael J. Pusnik, Jr. of Combat Camera Group Pacific.  Photo and caption cleared for public release by CDR Jacqueline Yost, COMTHIRDFLT PAO.

Source: www.acig.org/artman/uploads/bphoto08_001.jpg

Caption: A Mirage aircraft firing an Exocet missile

2 - Submarine - U-boat photo

Source: http://en.wikipedia.org/wiki/Image:U534.jpg

Caption: A dry-docked German U-Boat from the WWII era

Relevant Historical Uses of Submarines

The historical background attests to the effectiveness and shortcoming of submarines in naval warfare. World War I, World II, and the Falklands War provide examples of the utility of diesel-electric submarines " and of how they can be overcome.

However, the situation in the Strait of Hormuz differs from the past examples in one big respect: the geographical area in which Iran will be operating (the Persian Gulf) is much smaller than the area in which Argentina (South Atlantic Ocean), Germany (North Atlantic Ocean), and the United States (Pacific Ocean) were operating. The small area will make it difficult for submarines to go unnoticed.

Iran & Submarines

The depth of Strait of Hormuz (depth of 82 feet to 131 feet) is deep enough for ships, but is shallow for the submarines. The shallow waters and strong currents of the Strait both hamper and aid submarines " the water provides noisy background conditions that help cover up the sound of a submarine, but the shallow waters make the submarine more likely to be visually identified from the air or surface of the water. The confined waters and strong currents of the Gulf make the Strait of Hormuz an extremely hazardous place for even experienced submariners. [xvii]

The Kilos that Iran owns need to be modernized in order to keep their aging military equipment from becoming irrelevant. Modernizing the Iranian kilos comes with a high price tag of $80-90 million per submarine.[xviii] The Kilos' immediate threat is their ability to lay mines. Submerged Kilos offer the capability to covertly[xix] deploy 24 to 36 mines per sortie.[xx] However, Iran's indigenously produced (moored or floating) mines[xxi] are not deployable by submarine.[xxii]

In the end, the two or three Iranian Kilo submarines would have a very short period of survivability when confronted by the United States' anti-submarine warfare forces.[xxiii]

[i] British Royal Navy, Submarine FAQ. Online. Available: http://www.royalnavy.mod.uk/server/show/nav.2559 Accessed: April 23, 2008.

[ii] Naval-technology.com, SSK Kilo Class (Type 636) Attack Submarine, Russia. Online. Available: http://www.naval-technology.com/projects/kilo/index.html. Accessed: April 2, 2008.

[iii] Federation of American Scientists, Diesel-Electric Torpedo Submarine. Online. Available: http://www.fas.org/man/dod-101/sys/ship/row/rus/877.htm. Accessed: April 2, 2008.

[iv] Shirley A. Kan, Christopher Bolkcom, and Ronal O'Rourke, "China's Foreign Conventional Arms Acquisitions: Background and Analysis," Congressional Research Service Report for Congress, (October 10, 2000), p. 60.

[v] Shirley A. Kan, Christopher Bolkcom, and Ronal O'Rourke, "China's Foreign Conventional Arms Acquisitions: Background and Analysis," Congressional Research Service Report for Congress, (October 10, 2000), p. 60.

[vi]Shirley A. Kan, Christopher Bolkcom, and Ronal O'Rourke, "China's Foreign Conventional Arms Acquisitions: Background and Analysis," Congressional Research Service Report for Congress, (October 10, 2000), p. 60. Iran could retrofit its three Kilo Submarines with the capability of shooting Club-S missiles at a cost of $80-90 million per submarine.

[vii] Roy Burcher and Louis Rydill, Concepts in Submarine Design (Cambridge: Cambridge University Press, 1998), p. 126.

[viii] Roy Burcher and Louis Rydill, Concepts in Submarine Design (Cambridge: Cambridge University Press, 1998), p. 126.

[ix] Robert Jackson ed., Encyclopedia of Warships (San Diego: Thunder Bay Press, 2006), p. 361.

[x] The first diesel-powered submarine, the Aigrette, was built in 1904 by France. James L. George, History of Warships: From Ancient Times to the Twenty-First Century (Annapolis: Naval Institute Press, 1998), p. 158.

[xi] James L. George, History of Warships: From Ancient Times to the Twenty-First Century (Annapolis: Naval Institute Press, 1998), p. 160.

[xii] James L. George, History of Warships: From Ancient Times to the Twenty-First Century (Annapolis: Naval Institute Press, 1998), p. 166.

[xiii] G. H. Pearsali, The Effects of the World War II Submarine Campaigns of Germany and the United States- A Comparative Analysis (Newport: Naval War College, 1994).

[xiv] "The Lesson of San Luis," International Defense Review, Vol. 30 No. 8, p. 36.

[xv] "Solutions to the Shallow-Water Challenge," Jane's Navy International, Vol. 101 No. 5, p. 10.

[xvi] Norman Friedman, Sea Power as Strategy: Navies and National Interest (Annapolis: Naval Institute Press, 2001), p. 264.

[xvii] David Miller, "Submarines in the Gulf," Military Technology, No. 17 (1993), pp. 42-43.

[xviii] Major Dale R. Davis, "Iran's Strategic Philosophy and Growing Sea-Denial Capabilities," Marine Corps Gazette, No. 59 (July 1995), p. 22. Michael Eisenstadt, Iranian Military Power: Capabilities and Intentions (Washington DC, Washington Institute for Near East Policy, 1991), p. 120.

[xix] During the Iran-Iraq War, the mine-laying ship Iran "Ajr" was tracked, boarded, and sunk by U.S. naval forces in September 1987. See Anthony Cordesman, The Gulf and the West: Strategic Relations and Military Realities (Boulder, CO: Westview Press, 1988), pp. 390-391.

[xx] Major Dale R. Davis, "Iran's Strategic Philosophy and Growing Sea-Denial Capabilities," Marine Corps Gazette, No. 59 (July 1995), p. 22. Michael Eisenstadt, Iranian Military Power: Capabilities and Intentions (Washington DC, Washington Institute for Near East Policy, 1991), p. 120.

[xxi] However, Iran has reportedly received as many as 1800 Russian and Yugoslav mines with its first Kilo (See James C. Bussert, "Modernized Iranian Navy Poses New Gulf Dilemma," Signal, No. 51 (October 1996), p. 37-38.) and, as of 1998, was seeking to purchase rocket-propelled EM52 mines from China (See James C. Bussert, "Modernized Iranian Navy Poses New Gulf Dilemma," Signal, No. 51 (October 1996), p. 142); and James Bruce, "Choking the Strait: Iranian Naval Firepower and the Threat to Gulf Shipping," Jane's Intelligence Review, No. 8 (September 1996), p. 412).

[xxii] Michael Eisenstadt, Iranian Military Power: Capabilities and Intentions (Washington DC, Washington Institute for Near East Policy, 1991), p. 141.

[xxiii]David Miller, "Submarines in the Gulf," Military Technology, No. 17 (1993), p. 22.

This page last modified in August 2008

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