AIP Submarines For RSN



The New Archer-Class ( ex-Vastergotland Class ) Submarine



HMS Sodermanland was a Vastergotland-class SSK that was upgraded in 2003 with AIP.
Seen here in a 2010 photo. Photo via Wikicommons




In case you do not know, RSN stands for the Republic of Singapore Navy. The RSN has been operating submarines since 1995, when a total of 5 ex-Swedish Navy A-11 Sjöormen Class SSKs ( Diesel-electric Attack Submarines ) were acquired when they were being retired by the Swedes. These old boats were all launched between the years 1967 to 1968 making them more than 25 years old when they were sold to Singapore.

However, they were extensively refurbished and modernised by Kockums AB of Sweden ( now SAAB as of 2015 ) for operations in tropical climate before being re-commissioned for the RSN as the RSS Challenger Class submarines. Four of these boats form the backbone of the 171 Squadron while the fifth boat is cannabilised for spares.

The RSN subsequently acquired another 2 submarines from Sweden in late 2005, the A-17 Vastergotland Class SSK, which had been retired from service by the RSwN ( Royal Swedish Navy ). Again, Kockums AB was engaged to refurbish these submarines. At that time little else was announced about the deal, especially whether the refurbished boats will have Air-Independent Propulsion (AIP) technology*. Today, 16th Jun 2009, the public learnt from the daily newspapers and MINDEF releases that these two boats are the RSS Archer and RSS Swordsman. RSS Archer has been launched at Kockums AB yard at Karlskrona by Mrs Teo Chee Hian, wife of the DPM / Minister for Defense.

Swedish newspapers reported that the Vastergotland deal was worth SEK 1 billion, then equivalent to US$135 million.
 



Launch of the RSS Archer at Kockums Shipyard in Karlskrona 16th Jun 2009.
Photosource : Kockums AB Photographer : Peter Nilsson 

What is Air Independent Propulsion?

AIP is simply a non-nuclear submarine propulsion system that works without requiring an external supply of air. It allows a conventional ( non-nuclear ) submarine to remain submerged for a longer period of time compared with their diesel-electric cousins as the AIP engine negates the need for an external supply of air / oxygen.

 

Diesel-electric submarines have batteries that need to be recharged by their diesel engines every now and then when they are depleted. Running the diesel engines require air / oxygen that can only be supplied when the submarine is either on the surface or when it is snorkeling. When snorkeling, the submarine stays submerged just beneath the surface but sticks its snorkel mast up to suck in air and expel diesel exhaust.

These activities put the submarine at increased risk of being detected by visual or infra-red sighting, radar reflection from the snorkeling mast or conning tower, magnetic anomaly disturbances or by the acoustic signature of the noisy diesel engines.

With AIP, all of the above risks normally associated with battery recharging will be eliminated. It allows the submarine to remain submerged for 2 weeks or more and makes the AIP submarine much stealthier than its diesel-electric counterpart.

The AIP Integrator

Kockums AB is the Swedish shipyard owned by Germany's ThyssenKrupp Marine Systems after a series of mergers and acquisitions starting from 1999. They have been building quality submarines for Sweden since 1912 and were the first in the world to produce a purpose-built AIP submarine the A-19 Gotland-class. While the RSwN retired the HMS Vastergotland and her sister ship HMS Halsingland, it chose to upgrade the newer two ships, the HMS Sodermanland and the HMS Ostergotland to being AIP capable using Kockum AB's proprietary AIP Stirling Engine. Kockums basically cut the submarines into two at mid section and lengthened the hull to accommodate the new Stirling Engine. The Stirling AIP uses diesel and oxygen in a closed system. The upgrade is so radical that the 2 boats are considered a new class of their own - the Sodermanland Class.

 

 

Royal Swedish Navy : All AIP Fleet

 

With the completion of the Sodermanland-class upgrade, the Royal Swedish Navy became the only navy in the world to have an entirely AIP capable submarine fleet. Nobody else could have that claim. Who else better to turn to when you need AIP submarines than the Swedes? They are the experts!

The A17 HMS Vastergotland ( left ) and the more advanced
A19 Gotland-class HMS Uppland  along side at Malmo, Sweden.
Photo taken in 2003 before the Vastergotland was sold to Singapore. Wikicommons



HMS Sodermanland and the submarine rescue ship A-214 HMS Belos in 2003. Wikicommons

 

Blue Water vs Brown Water

The US Navy commissioned the world's first operational nuclear submarine the USS Nautilus (SSN-571) in 1954 and never looked back. Their last batch of conventional diesel-electric submarine, the Barbel-class, was ordered between 1955 to 1956 and all had been retired by 1990. They now have an exclusively nuclear underwater fleet which is extremely effective for blue water ( open ocean ) operations which require long endurances. The Swedes however, have vastly different requirements where they have huge swaths of coastlines with deep narrow fjords to patrol. The salinity and temperature of the Baltic Sea are also very different from that of the open oceans and therefore the Swedes have long settled with conventionally powered submarines.
 

Singapore is a littoral state with plenty of shallow, murky waters and busy, noisy sea lanes. The small Swedish SSKs are well suited for this kind of underwater environment. Besides, modern diesel-electric submarines, like the Russian Type 636 improved Kilo Class SSK, can be extremely quiet especially when they are drifting or moving very slowly ( less than 5 Knots ). In fact, the RSwN HMS Gotland was "leased" to the USN for 2 years between 2005 to 2007, complete with crew, for bilateral anti-submarine exercises. Uncle Sam will not need to practice ASW with HMS Gotland if it was not quiet!

Growth of RSN's ASW Capabilities

The Anti-Submarine Warfare (ASW) capabilities of the RSN has grown in leaps and bounds ever since its early days of operating the Seawolf-class missile gunboats ( since retired ). In the 80s came the Victory Class missile corvettes with their variable depth sonar and Whitehead Alenia torpedoes. The 90s saw the addition of the Fearless Class ASW Patrol Vessels and of course, the best ASW platform, the Challenger Class SSKs.
The missile corvettes and the patrol vessels are both too small to accommodate any ASW helicopters. That glaring deficiency has since been rectified with the purchase of the Formidable Class stealth frigates which will carry the Sikorsky S70B Seahawk ASW helicopter, assumingly with magnetic anomaly detectors and towed array sonars plus offensive weapons like the mk46 torpedoes.
With the commissioning of the RSS Archer and Swordsman due in ?2010/2011, the RSN will have AIP technology among its submarine fleet and significantly increase its reach.
We must also not forget the aerial assets of the RSN, the Fokker F50 maritime patrol aircraft, in operation with the 121 Squadron since 1993, which acts as a force multiplier when dealing with naval threats.




What Singapore's Neighbours Have or Are Acquiring

The Malaysians have received their first of 2 Scorpene Class SSK earlier this year, the KD Tunku Abdul Rahman. These Scorpenes are not AIP endowed, unlike their more capable Spanish S-80 / S-80A cousins with the MESMA AIP engine which uses ethanol and compressed oxygen. They have another older Agosta B SSK based in France for training purposes. Since these were bought in 2002 during Malaysia's M-Era, the officially stated RM3.4billion package came with certain landing rights at the Charles de Gulle Airport for MAS as well. Maybe they could have had 3 scorpenes for the same price ( or 2 scorpene basic-AIPs ) had they not insisted on those landing rights, or having to pay the hundred over million ringgit of brokerage fees, or.... I digress. The second boat KD Tun Razak is due to be commissioned later this year.

The Indonesians have 2 ageing Type 209 / 1300 Cakra Class SSK since 1981. They have been recently upgraded by the South Koreans who also operate the Type 206 / Type 209 submarine. The Type 209 is one of the most widely exported submarine from the West. They have made an agreement with Putin in 2007 to buy among other things, 2 Type 636 Kilo Class SSK plus options for another 8 more. These orders have yet to be fulfilled.

Thailand has no submarine fleet but are eager to acquire one. Earlier efforts by Sweden to sell them the A19 Gotland Class submarine have failed to materialise. Most of the money could have gone into financing their purchase of the 12 SAAB JAS-39 Gripen fighters and the 2 SAAB S-1000 Erieye AEW. Air Force 1 Navy 0.

Vietnam has 2 ex-Yugoslav minisubs for special forces operations and has recently ( Apr 09 ) agreed in principle to buy 6 Russian Type 636 Kilo Class SSK. Pegged at USD1.8Billion these are said to be originally the ones ordered by Venezuela, but with Hugo Chavez's falling oil fortunes are now going to Vietnam.

Australia has 6 Type 471 Collins Class Diesel-electric SSK designed by Kockums AB. These are among the world's largest non-nuclear submarines displacing 3350tons submerged suited to patrolling the vast coastlines of Australia. They are quiet and capable boats with a large weapons load including the Boeing Sub-Harpoon anti-ship missile and the Mk48 ADCAP torpedoes. They can be retrofitted with AIP engines. Following a bad start with lots of delays and deficiencies, these boats have been upgraded with a combat control system from Raytheon similar to the one in the Virginia Class SSN of the US Navy.

The New Zealanders are on good terms with the Aussies and do not have any perceived threats in their immediate vicinity. The Helen Clarke Government retired the last of their 1950 era McDonnell Douglas A-4Ks without any replacement. Their air force now only operates helicopters and transports. The RNZN does not own any submarines.

The Future

What next after the RSS Archer? The RSN will probably retire part of its Challenger Class fleet upon arrival of the RSS Archer and RSS Swordsman. They can be mothballed or be used as a training submarine or be cannibalized for spare parts. Once its AIP operational experience has been gained, it can either look to acquire the A-19 Gotland Class when the Swedes are ready to retire them or consider other advanced options like the German HDW U212 / U214 AIP SSKs or the Russian Amur 1650 / Amur 950 / Kilo SSKs or God forbid, the DCNS / Navantia Scorpene SSK.

Update 2013

RSS Archer and Swordsman have both been commissioned. The 4 older Challenger Class submarines are still operational. There are now rumours that RSN could be interested in the latest Swedish A26 Class submarine.

The Collins Class SSKs of Australia is still plagued by generator and sonar problems. Only one out of six ship is currently operational. The RAN is looking to acquire 12 new enhanced-Collins type submarines as their replacement.

Indonesia bought 3 Type 209 / 1400s from South Korea.

Malaysia has received Exocet missiles with land attack capabilities for their Scorpene submarines, range about 180km .....

Update 3rd Dec 2013

In the Straits Times : The Republic of Singapore Navy will be acquiring 2 customized Type 218SG AIP submarines from HDW Kiel. They are likely to be ready by 2020. Two of the older Challenger class non-AIP submarines will be retired.