October 23, 2015

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")

It has been reported in late September 2015 at IHS Jane's Navy International and herehere 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.


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.



Julien Araneta said...

Hi, Pete!

Indeed, Philippine Navy should scram a feasibility study (which I believe would result a positive) to acquire, train and operate this SoKor KSS-500A sub not for direct naval combat engagement but for passive surveillance deployment only. I believe this submarine, being brand new and with modern sensors (as opposed to none at the moment with PN), will offer a step ahead (versus pre-used ones) in training and operational familiarizations (manual vs digital/electronic). The risk skeptics love to argue is that "training need not be with brand new and updated platform" is at best very shortsighted and limited - lacking the will, initiative and courage (even logic) - that new systems will give years of service and current proficiency, efficiency and competence in submarine warfare.

But, Pete, problem is, the Philippine Navy is yet to formulate its submarine warfare doctrine in both strategic and tactical level as it have zero experience regarding that warfare dimension.


Nicky said...

HI Pete,
How dose the HDS-400 stack up to a well known small submarine such as Type 206, Kobben and Gal class Submarines. What I suspect south Korea is attempting to do is build something that is on the level of the Type 206, Kobben and Gal class Submarines. Which are under the 500 ton range and would be perfect for a country looking for a very small littoral submarine.

jbmoore said...


Mini subs are perfect for special forces insertions and extractions. Their combat record is mixed. Only one of the Japanese minisubs may have gotten into Pearl Harbor in 1941 and completed their mission, but it was suicide for the crew. There was also success in Diego Suarez harbor in 1942. It may have been a Yono class minisub that sank the ROKS Cheonan. It is a 130 ton displacement. The technology has gotten better, so a 300-ton submarine could be quite deadly, especially if automated to allow a minimum crew complement which would allow it to stay submerged longer. The NR-1 displaced 400 tons. It was a deep diving nuclear submarine used for classified deep ocean retrievals and searches. Deep sea covert ops would be another useful mission for a smaller sub since their hulls could be build stronger. But, minisubs capable to entry and exit in shallow waters is probably the best use of the vehicles. Russian minisubs may be making a comeback as well.



MHalblaub said...

Dear Pete,

the Type 200 might be a smaller version of the Type 206. The old Type 206 needed a crew of 23 and the Type 200 just 6!?! Just console operators, no cook and no mechanist? The Type 206 was an attack submarine with 8 heavy weight torpedoes. So without that load and just the aim to transport special forces the submarine can shrink.

The new eletric motors need no gear box and are therefore shorter and lighter. Also the Type 212 operates with just one diesel electric engine. Maybe AIP only to reduce the workload for the extremly small crew. Such a submarine could also be interesting for the US or others to gather intellegence.

I still think Type 210mod would be the best option for Australia.


Peter Coates said...

Hi Julien Araneta

As the KSS-500A (HDS-500) hasn't yet been built the also not built HDS-400 should be even cheaper for the Philippines to buy and operate. Also the HDS-400 would not empasise torpedos, with maybe only 2 lightweights.

In terms of doctrine HDS-400 would be particularly useful setting out from Palawan and Luzon to gather intelligence on Chinese island-reef developments in the South China Sea. Maybe with some expert US crew.



Peter Coates said...

Hi Nicky

MHalblaub's comment pretty much compares the HDS 400/500 with the Kobben/206/Gal. Possibly Germany's TKMS-HDW may have designed the HDS 400 and 500 as as update of the 205/206/Kobben/Gal although South Korea is building it.



Peter Coates said...

Hi jbmoore

Yes the Japanese 2 man mini-subs that unsuccessfully attacked Pearl Harbour also did poorly in Sydney Harbour. Pretty much suicide subs.

A Japanese 2 man sub was successful in Madagascar in 1942 damaging UK battleship Ramillies and sinking a tanker https://en.wikipedia.org/wiki/Battle_of_Madagascar#Landings_.28Operation_Ironclad.29

The British had high losses but some success with 30 ton X-craft minisubs against the German battleship Tirpitz in 1943 https://en.wikipedia.org/wiki/X-class_submarine

South Korea could do well marketing HDS-400s and 500s to numerous customers.



Peter Coates said...

Hi MHalblaub

The Type 200 and 300 might indeed be a smaller version of the Type 206 with much reduced crew and less propulsion workload than the 206/Kobben/Gal. Special forces and/or sensors could be the main 200/300 functions.

Yes I thought of the US as a possible customer for the 200, 300, 400 or 500. The US could also use those platforms as "enemy" to train US and Western ASW forces.

With all the demands on Australia's limited naval budget I do thing Australia acquiring 4,000 ton (surfaced) subs is extravagant. 210, 214 or 218s would be much more economical and would be able to function with far lower crews than the projected 60.



Nicky said...

HI Pete,
That's what I am thinking in MHalblaub's comment. I was thinking that the HDS 400/500 could be an evolution of the Kobben/206/Gal class Submarines. That could be because South Korea is trying to fulfill a niche in a 500 ton SSK Submarine on the level of the Kobben/206/Gal class Submarines. I wonder if the HDS 400/500 draw lessons from the Kobben/206/Gal Class Submarines. I think the HDS 400/500 would fulfill a niche for those who are looking for a small 500 ton submarine for the Littorals

Peter Coates said...

Hi Nickky

Given all the North Korean minisubs and North Korea's likely high intensity of submarine defences South Korea could indeed need HDS 400s or 500s.

Certainly they would have limited range but good shallow water ability which makes them ideal littoral subs.



Anonymous said...

RN had more success with the XE-class in the Far East. They cut the telegraph cable between Hong Kong and Saigon and the telegraph cable between Hong Kong and Singapore in two different operations. Two subs also infiltrated the Singapore harbour and sunk the heavu cruiser Takao.
Most likely had the technology matured by then and the better sea conditions in the Far East, compared to the North Atlantic also helped.

I very much doubt that USN would buy some small conventional subs for training, their admirals are almost allergic to the idea. I think they prefer to either train against allied subs or as with the case with HSwMS Gotland, lease in a sub for a year or two.


Peter Coates said...

Hi /C

The XE class mini-subs certainly were successful.

The undersea cable cutting also encouraged "the Japanese to use radio and render themselves open to message interception" https://en.wikipedia.org/wiki/XE-class_submarine.

The risk to the US Navy submarine service of being reduced to smaller, cheaper, less able conventional subs is very real and deeply felt.

Better for the USN that it retains SSNs and deploys a whole new generation of large diameter UUVs and diver delivery vehicles for the shallows.



Anonymous said...

"I very much doubt that USN would buy some small conventional subs for training, their admirals are almost allergic to the idea. I think they prefer to either train against allied subs or as with the case with HSwMS Gotland, lease in a sub for a year or two."

The USN lost its taste for conventional Subs after the USS Gudgeon (SS-567)
incident off Vladivostok back in 1957:


The prospect of having one of their subs forced to the surface and possibly
boarded or even captured is something no navy wants to deal with.

Peter Coates said...

Hi Anonymous [Oct 26 9:55 AM]

Quite chilling. As Australia "progresses" to a new Future SSK with the weight and cost of an SSN Australia may well look forward to a Gudgeon like incident against China.



Anonymous said...

"Yes the Japanese 2 man mini-subs that unsuccessfully attacked Pearl Harbour also
did poorly in Sydney Harbour. Pretty much suicide subs."

The Japanese mini-subs may have done more damage in Pearl Harbor than
originally thought:

Pearl Harbor mini-submarine mystery solved?:

"No torpedoes were found on the wreck, and evidence suggests that they
were not present when the boat was sunk. A newly declassified
photograph taken by a Japanese plane during the attack appeared to
show a mini-sub firing a torpedo into Battleship Row. A report to
Congress in 1942 by Adm. Chester W. Nimitz describes an unexploded
800-pound torpedo recovered after the battle. That's twice the size
carried by the torpedo bombers.

That torpedo was apparently a dud that missed the West Virginia.

But an examination of the remains of the Oklahoma shows that it
apparently had underwater damage much larger than that associated with
aerial torpedoes. An underwater blast would have caused it to capsize,
Stephenson said. "Otherwise it would have settled to the bottom
upright," like the other sunken ships.""





Peter Coates said...

Hi Anonymous [at October 26, 2015 at 12:39 PM]

All a sad end. Maybe in Pearl Harbour and later in Madagascar, Japanese mini-subs had some success. But subsequent death was near certain.

Japan's use of large mother subs sometimes towing suicidal mini-subs was nowhere near as successful (overall) as US, UK and German strategy/tactics of using medium size subs each sinking many enemy cargo ships and sometimes warships.



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