South Korean HHI's HDS-400 Small Submarine Mystery

Above is South Korea's HDS-500 (aka KSS-500A). Does Hyundai Heavy Industry (HHI's) HDS-400 look like the South Korean design concept above? Or does HDS-400 look like the TKMS Type 300 design concept below? 

A TKMS Type 300 (for 300 tons surfaced) design concept. (Diagram courtesy Turkish Navy "ship bucket")

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It has been reported in late September 2015 at IHS Jane's Navy International and here, here and here that Hyundai Heavy Industries (HHI) is building a small submarine, known as the HDS-400, for a secret naval customer. Apparently one Kim Moon-ju, a Communications (Public Relations) Officer for HHI, would not divulge details of the customer. The HDS-400 reportedly weighs 400 tons (surfaced), is 40 m long, and has a maximum speed of 15 knots. Those specifications may suggest a submarine that can approach a well guarded enemy coast, insert or extract special forces or spies, or operate more securely in shallow seas. 

The main mysteries include who is the lucky naval customer and how is the HDS-400 propelled? 

One approach to answering such mysteries is to look at South Korea's small submarine record. I classify a midget or mini-submarine as 200 tons (surfaced) or less and a small submarine as over 200 tons. Since 2011 South Korea has been trying to market a design variously known as the HDS-500, KSS-500A and HDS-500RTN (when recently offered to Thailand). The HDS-500 design weighs 500 tons (surfaced), is 37 metres long and could be propelled by Lithium-ion Batteries (LIBs) alone with the LIBs charged from a generator on the wharf. No diesels means no noisy, exposed, indiscrete snorting is necessary. Or the HDS-500 could have diesel engines to charge LIBs.

Note that if the HDS-400 is launched before 2020 it might still rely on lead-acid batteries depending on how South Korea's and maybe Germany's LIB development programs are going. This recognises that South Korea has mainly relied on German Type 209 and 214 designs to date. A relationship that may partially continue.

If a 100 tons lighter HDS-400 is LIBs only this could widen its appeal both to the South Korean Navy as a customer or to a foreign customer.

Reasons the South Korean Navy may be an HDS-400 customer include:

-  need to trial the sub with realistic testing as it is an unusual size, battery only and new style LIB submarine.

-  if diesel engines charge LIBs it would be valuable testbed for subsequent LIBs on future larger submarines used by South Korea and perhaps by Germany. South Korea is developing a future larger submarine variously called KSS-3, KSS-III, D-3000 and KSS-3000 with perhaps a launch by 2025 timeframe which may be well aligned to use LIBs.

-  South Korea needs some mini-small subs to test ASW warfare forces and sensors. This is because its main opponent, North Korea, uses mini-subs frequently.     

-  South Korea's remaining two Dolgorae class mini-subs are still operational but were launched in 1990 and 1991. So they are nearing the end of their operational lives (2020) and need to be replaced if South Korea wishes to maintain a mini-small submarine capability. 

Reasons a foreign navy my be the first or later customer for the HDS-400 include:

A foreign customer need not be small as a small battery only (or LIB only) submarine could approach a coast that has a higher intensity of ASW sensors or shallower water than a standard size submarine of 1,000 tons upwards. Possible navies interested are many, including:

-  Turkish Navy that was considering TKMS Type 200 (diagrams below) and Type 300 (diagram above) designs in the past. Turkey has built and operates full size TKMS subs.

-  Vietnamese Navy - Vietnam will soon have all 6 Kilo subs in total  - in Comments for Submarine Matters recent Philippines article "Anonymous - from Europe" said "The Vietnamese Navy acquired several ["Yugo" class mini-subs of about 100 tons] from N-Korea to preserve the skills & knowledge and use them for Special Operations in the South China Sea ... rumors on Viet forums is that the VN-MoD has placed an order for 4 Hyundai HDS-400A. The first is under construction in S-Korea and there might be "ToT"? involved for the remaining units. The N-Korean midget-subs are nearing their service-life later this decade. This is an excellent opportunity for Philippine Navy to piggyback and place an order. VN can benefit from lower unit-prices. Those subs cannot win a war, but could very useful for recon, sabotage etc. Just like VN in 1990s they could be foundation a fleet of larger SSK later."
-  Taiwanese Navy. This might explain South Korea's secrecy. It would be easier to build and hand-over a submarine to Taiwan before China decides to publicly object. Just 400 tons makes an HDS-400 a defensive submarine.
-  the US Navy may want to trial the intelligence gathering and special forces value of a mini HDS-400 submarine. Also the US could use it in ASW exercises - given opponents North Korea and Iran widely use mini-submarines.

-  many other western-friendly navies that already have full size subs could be future customers

Western-friendly navies with limited budgets and/or have to operate in shallow water, include:

-  Royal Thai Navy

-  Philippines Navy

-  Sri Lanka

-  Bangladesh

-  maybe Myanmar/Burma

-  many in Europe, Africa, Middle East, Latin America

So, like the great Type 218SG mystery, the who is buying HDS-400 mystery? will eventually be revealed.

USEFUL WEBSITES ON MIDGET AND MINISUBS

This Wiki website mentions many other midget or mini-submarine consumer and producer countries. North Korea is a politically less popular supplier or on-seller. Yugoslavia, when it was one country, was a producer. Italy was a producer and still may be.

Covert Shores also has a wealth of detail and diagrams on midget or mini-subs.

Above and below are concept drawings of a TKMS Type 200 (200 ton surfaced) mini-sub design (Drawings courtesy Turkish Navy shipbucket)

Both the TKMS Type 200 and Type 300 designs can use strap on heavyweight (533mm) torpedos, one on each side, and/or lightweight (400mm or less) torpedos fired from torpedo tubes.

Pete