Sejong the Great-class destroyer

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ROKS Sejong the Great (DDG 991) broadside view.jpg
ROKS Sejong the Great (DDG-991)
Class overview
Operators Republic of Korea Navy
Preceded by Chungmugong Yi Sun-sin class
Succeeded byKDDX-class destroyer
Cost$923 million[1]
General characteristics
TypeGuided-missile destroyer
  • 7,650 tons standard displacement
  • 10,600 tons full load
LengthBatch 1 166 m (544 ft 7 in), Batch 2 170 m (557 ft 9 in)
Beam21.4 m (70 ft 3 in)
Draft6.25 m (20 ft 6 in)
Speedexceeds 30 knots (56 km/h; 35 mph)
Range5,500 nmi (10,200 km; 6,300 mi)
Endurance30 days
Sensors and
processing systems
  • AN/SPY-1D(V) multi-function radar
  • AN/SPG-62 fire control radar
  • DSQS-21BZ-M hull-mounted sonar
  • SQR-220K towed array sonar system
  • Sagem Infrared Search & Track (IRST) system
Electronic warfare
& decoys
LIG Nex1 SLQ-200K Sonata electronic warfare suite
Aircraft carried2 × Super Lynx or SH-60 Seahawk
Aviation facilitiesHangar and helipad

The Sejong the Great-class destroyers (Sejongdaewang-Geup Guchukam or Hangul: 세종대왕급 구축함, Hanja: 世宗大王級驅逐艦), also known as KDX-III, are three guided-missile destroyers of the Republic of Korea Navy (ROKN).[2]

Hull name[edit]

On 20 April 2007, South Korean Chief of Naval Operations announced that the lead ship of KDX-III class destroyers will be referred to as Sejong the Great. Sejong the Great (Hangul: 세종대왕) is the fourth king of the Josun Dynasty of Korea. He is credited with the creation of the indigenous Korean system of writing.[3]


The Sejong the Great class is the third phase of the South Korean navy's Korean Destroyer eXperimental (KDX) program, a substantial shipbuilding program, which is geared toward enhancing ROKN's ability to successfully defend the maritime areas around South Korea from various modes of threats as well as becoming a blue-water navy.[4]

At 8,500 tons standard displacement and 11,000 tons full load, the KDX-III Sejong the Great destroyers are the largest destroyers in the South Korean Navy and larger than most destroyers in the navies of other countries.[5] They are built slightly bulkier and heavier than Arleigh Burke-class destroyers or Atago-class destroyers to accommodate 32 more missiles. As such, some analysts believe that this class of ships is more appropriately termed a class of cruisers rather than destroyers.[6] KDX-III are currently the largest ships to carry the Aegis combat system.[7]


Sejong the Great-class destroyers' main gun is the 127 mm/L62 Mk 45 Mod 4 naval gun, an improved version of the same gun used on other warships from several other nations. Point-defense armaments include one 30 mm Goalkeeper CIWS and a RIM-116 Rolling Airframe Missile Block 1 21-round launcher, the first Aegis platform to carry RAM.[8] Anti-aircraft armament consists of SM-2 Block IIIA and IIIB[9][10] in 80 total Mk 41 VLS cells. Block IIIB has added infrared (IR) induction mode to Block IIIA, improving interception capability.

Anti-submarine warfare armaments consists of both K-ASROC Hong Sang-uh (Red Shark) anti-submarine rockets, which have the same form as the U.S. ASROC, and 32 K745 LW Cheong Sang-uh (Blue Shark) torpedoes. Anti-ship capability is provided by 16 SSM-700K Hae Sung (Sea Star) long-range anti-ship missiles, each with performance similar to the U.S. Harpoon. It is equipped on a navy ship that is built after the late KDX-II destroyers. Land-attack capability is provided by the Hyunmoo III cruise missile.[4]

Missile batteries

  • Vertical Launching System: 128 total cells
    • Mk 41 VLS 48 cells (Fwd)
    • Mk 41 VLS 32 cells (Aft)
    • K-VLS 48 cells (Aft)
  • Anti-ship missile launchers:
    • 16 (4 × quadruple) launchers


The ship features the Aegis Combat System (Baseline 7 Phase 1) combined with AN/SPY-1D(V) multi-function radar antennae.[11][4] This gives the destroyers the ability to track missiles launched from anywhere in North Korea. This capability was demonstrated by the tracking of a North Korean missile in April 2009.[12]

The Sejong the Great-class destroyers are often compared to the Arleigh Burke and Atago classes because they utilize the AN/SPY-1D multi-function radar, and have similar propulsion and capabilities. One notable difference between the Sejong the Great-class ships and Arleigh Burkes is the number of VLS cells. Destroyers of the Sejong the Great class have a capacity of 128 missiles, as opposed to 96 on the Arleigh Burke class and the Japanese Atago-class destroyers. The Sejong the Great class is thus one of the most heavily armed ships in the world,[13] with greater missile capacity than the Chinese People's Liberation Army Navy Type 055 destroyer[14] (112 VLS cells) and the U.S. Navy Ticonderoga-class guided-missile cruiser (122 VLS cells). The Sejong the Great class is surpassed in VLS depth only by the Kirov-class battlecruiser with 352 missiles (entire missile load).[15]

Another similarity to Arleigh Burke Flight IIA and Atago-class destroyers is the presence of full facilities for two helicopters,[1] a feature missing from earlier Arleigh Burke[16] and Kongō-class destroyers.[17]


In August 2016, press reports revealed that South Korea was considering adding the SM-3 interceptor to its Sejong the Great-class ships to enable them to perform ballistic missile defense in response to North Korean efforts to bolster offensive missile capabilities. This came months after the U.S. decision to deploy the THAAD missile interceptor system on mainland South Korea. The addition of SM-3s to the ships may require software and computer hardware upgrades.[18] The following month, Aegis manufacturer Lockheed Martin confirmed the next three Sejong the Great vessels will be capable of performing "integrated air and missile defense" (IAMD) to supplement U.S. Army ground-based missile interceptors on the peninsula, likely being outfitted with the SM-3. While the first three destroyers are fitted with Aegis Baseline 7 based on older proprietary computers that can't carry out IAMD operations, the following three will be fitted with the Baseline 9 version of the Aegis Combat System that combines modern computing architecture to allow the AN/SPY-1D(V) radar to perform air warfare and BMD missions at the same time.[19]

Ships in the class[edit]

Name Pennant number Builder Launched Commissioned Status
Batch I
ROKS Sejong the Great (Korean: 세종대왕함) DDG-991 Hyundai Heavy Industries 25 May 2007 22 December 2008 Active
ROKS Yulgok Yi I (Korean: 율곡 이이함) DDG-992 Daewoo Shipbuilding & Marine Engineering 14 November 2008 31 August 2010 Active
ROKS Seoae Ryu Seong-ryong (Korean: 서애 류성룡함) DDG-993 Hyundai Heavy Industries 24 March 2011 30 August 2012 Active
Batch II
ROKS Jeongjo the Great (Korean: 정조대왕) DDG-995 Hyundai Heavy Industries 28 July 2022 Launched

On 10 October 2019, HHI signed a deal to build the first of three 170m long, KDX-III Batch II Aegis destroyers for the Republic of Korea Navy. The Sejong the Great class is KDX-III Batch-I, and Korean Navy is planning 3 ships of KDX-III Batch-II.[20] Under the deal, HHI will deliver the first ship by November 2024.[21]

See also[edit]


  1. ^ a b "Sejong the Great Class Guided Missile Destroyer |". Retrieved 26 December 2022.
  2. ^ "ROK (Republic of Korea) Navy to increase KDX-III Aegis destroyers to six by 2027". 11 December 2013. Archived from the original on 12 December 2013. Retrieved 12 December 2013.
  3. ^ Kim-Renaud, Young-Key (Spring 2000). "Sejong's Theory of Literacy and Writing" (PDF). Studies in the Linguistic Sciences. 30: 13–45 – via CORE.
  4. ^ a b c "Sejong the Great (Sejongdaewang) class Destroyer - KDX-III". Retrieved 26 December 2022.
  5. ^ "Koreas KDX-III AEGIS Destroyers". Archived from the original on 11 December 2009. Retrieved 8 March 2010.
  6. ^ "Sejong the Great Class Guided Missile Destroyer."
  7. ^ "Aegis Weapon System Verified During Korean Navy Ship - at DefenceTalk". Archived from the original on 5 December 2010. Retrieved 21 October 2010.
  8. ^ "KDX-III / DDH-III Sejongdaewang". Guide to Military Equipment and Civil Aviation. Archived from the original on 7 October 2006. Retrieved 7 April 2009. These ships will be the world's first combining proven AEGIS and RAM.
  9. ^ "Korea to acquire new missiles for Aegis destroyer". The Korea Herald. 28 June 2009. Retrieved 27 June 2009.
  10. ^ "Republic of Korea - SM-2 Standard Missiles" (PDF). Defense Security Cooperation Agency. 26 May 2009. Archived from the original (PDF) on 27 May 2011. Retrieved 27 June 2009.
  11. ^ LaGrone, Sam (6 September 2016). "New South Korean Destroyers to Have BMD Capability". USNI News. Retrieved 26 December 2022.
  12. ^ "Korea Launches 3rd Aegis Destroyer". Archived from the original on 14 June 2012. Retrieved 10 May 2012.
  13. ^ Burleson, Mike (25 May 2010). "South Korean Naval Plight Our Own". New Wars. Archived from the original on 28 October 2011. Retrieved 10 November 2011.
  14. ^ China's New Guided Missile Destroyer To Be Its Biggest Yet Archived 6 December 2016 at the Wayback Machine -, 24 October 2016
  15. ^ Kirov class Archived 4 March 2016 at the Wayback Machine -
  16. ^ "DDG-51 ARLEIGH BURKE-class - Navy Ships". Retrieved 26 December 2022.
  17. ^ "Kongo class". Retrieved 26 December 2022.
  18. ^ Report: South Korea Wants BMD Capability for Guided Missile Destroyers Archived 15 August 2016 at the Wayback Machine -, 15 August 2016
  19. ^ New South Korean Destroyers to Have Ballistic Missile Defense Capability Archived 7 September 2016 at the Wayback Machine -, 6 September 2016
  20. ^ "Hyundai Heavy bags 677 bln-won deal to build upgraded Aegis destroyer". 10 October 2019. Retrieved 10 October 2019.
  21. ^ "South Korea's Mid-Term Defense Procurement Plan Largely Unaffected By COVID-19 Crisis". May 2020.

External links[edit]