Spain’s S-80: the SEA 1000 dark horse?

Undersea warfare

1st Oct 2010

The acquisition strategy for SEA 1000 – the Collins Class submarine replacement project – can logically take two paths.

The first is for Australia to develop a new class of submarine; the second is to procure a military-off-the-shelf (MOTS) product with some changes to meet local requirements. Of course there can be some blurring between the two because if an existing design is sufficiently altered then in essence it becomes a new submarine – a lesson that should have been learned with the Collins Class.

There are several MOTS submarines in service but realistically the two that might be available for Australia are the German HDW Type 214 and the French DCNS ‘Scorpene’. Two other submarines will meet the MOTS classification within the SEA 1000 timeframe and they are the Spanish Navantia S-80, currently under construction, and the Swedish Kockums / HDW A26, which has been ordered and is in the design stage.

Of these four submarines, the largest is the S-80 which will have a maximum displacement of 2,400 tonnes. The Royal Australian Navy has always maintained a preference for a large conventional submarine based largely on the argument that size correlates directly to vital operational requirements such as range and endurance. Before detailing other features of the S-80 it is worth examining these features because they can be somewhat fuzzy and misleading.

The range of a submarine is determined by the amount of fuel it carries and uses. Just like a car, the sheer size of the fuel tank is not itself a guide to range – as any driver of a Toyota Prius (such as the author) is aware. A large submarine can carry more diesel but it also needs more energy to push it through the water. Another factor influencing range is the way the submarine is operated – having extremely long range but at an extremely low speed might not be an operationally desirable formula. Having mentioned this, the stated range of the S-80 is 12,500 nautical miles at 4 knots (even this qualified by the hotel load, the frequency of snorting etc), reducing to 11,700 nautical miles at 9 knots and so on. This is comparable with the Collins Class and while some commentators have called for the new submarines to have even greater range the justification for this looks flimsy.

In other words a large submarine does not necessarily have greater range than a smaller one and it may transpire that 2,400 tonnes – or even less than that – will meet Australia’s range requirements.

Turning to endurance, this is simpler to work out than range because this is a matter of calculating how many days the submarine can remain at sea. This relates to the amount of supplies that can be carried on board relative to the size of the crew and in this case the S-80 has enough for in excess of 50 days. This is with a crew of 32 and an additional 8 special forces personnel. Clearly, if just the basic crew were on the submarine its endurance would be considerably greater. This relatively small crew size – a highly desirable feature – is due in no small part to a high level of system automation.

This again is comparable with Collins. It is also worth pointing out that because of continuing reliability problems not a single Collins Class has ever been able to stay at sea for its specified maximum endurance. Again, it can be concluded that it is more than possible that a submarine such as the S-80 will have endurance similar or perhaps greater than that of the Collins Class.

On the 31st of May this year the RAN’s Future Submarine Project Director, Rear Admiral Rowan Moffit was asked in the Senate, whether to meet the requirements set out in the Government’s Defence White Paper, the Collins Class replacement would need to be a bigger design of around 4,000 tonnes. He replied:

“There are submarines in existence or in design today which can come very close in
some respects to answering all of those questions and which are not 4,000 tonne submarines.”

He added:

“The difficulty that we confront in simply comparing some of these things against the stated white paper objective, is that we are looking at technologies which are not well developed today and which we need to understand the development path for, so that we can know what sort of increased capabilities might be available to us from them, in the event they reach a level of maturity that makes them available to us.”

What a large submarine tends to have over a smaller one is internal volume and therefore a larger payload and possibly increased crew comfort. The S-80 seems to do well in both areas, though crew comfort has a level of subjectivity. The weapons payload includes not only DMA4 torpedoes and sub-Harpoons but potentially Tactical Land Attack Missiles such as Tomahawk – something that will be of great interest for Australia.

The Navantia shipyard at Cartagena looks much smaller than Australia’s ASC and is certainly much older and far busier. The two main assembly halls are an absolute hive of activity, with welders, angle grinders and various other noise-making implements generating curtains of sparks. Compared with the sometimes-glacial pace of activity in other yards – not naming names – the Spaniards are going flat out, which is hardly surprising since the first S-80 will be launched in 2012 with delivery to the Navy (Armada) at the end of 2013 once sea trials are completed. The interval between the construction of the first and second submarines is one year, dropping to a fairly amazing seven months for numbers three and four. APDR has observed that no siestas are being taken.

Navantia received the order for an initial batch of four S-80s in 2003, though work had commenced in the mid-1980’s with a naval staff requirement being formulated. (Note to the RAN and Defence Minister Stephen Smith: it can take around 20 years for an experienced builder to produce an entirely new class of submarine – and we want ours to be in service when?).

The Armada hopes to eventually acquire an additional two S-80s. However, because of Spain’s major problems with the structure of its budget these plans have been placed on hold indefinitely.

At all times Navantia emphasise that the S-80 is an entirely new submarine and is not a derivative of anything else. The reason for making this point is that Navantia and DCNS of France are apparently involved in a legal squabble over some intellectual property matters – even though neither company discusses the issue. This relates to the aforementioned ‘Scorpene’ submarine, which started life as a joint activity between the two companies. It is believed that DCNS contends that some features of the ‘Scorpene’ have found their way into the S-80 but presumably this is not the view from Spain.

It is well beyond the scope of this article to review the entire history of submarines but it can be noted that Spain was an early player in this domain, with at least one early design being produced in 1864. Just like all other navies, it took the Armada a little while to recognize the potential of underwater warfare, but by the late 1880s they had embraced the technology in the form of a submarine known as the ‘Peral’ – which today sits on top of a quaint fountain on a Cartagena traffic roundabout. After a completely arcane legal dispute surrounding the ‘Peral’ there seems to have been a gap in submarine-related activity, which only resumed towards the end of the First World War. After that, Spain has almost continuously built or purchased submarines with varying pedigrees – German, Dutch, French and US. And, most recently, Navantia has had half of the joint production of the ‘Scorpene’ Class for the navies of Chile, Malaysia and now India. The S-80 seems to be the first completely indigenously designed Spanish submarine for quite some time and the company has drawn on a huge amount of previous experience to come up with a leading edge product.

This is displayed in a number of areas – such as air independent propulsion (AIP). It seems that all conventional submarines now come with AIP because they allow far greater underwater endurance. The Spanish system uses bio-ethanol and liquid oxygen as the initial heat source for the generation of electricity. Navantia describes their approach as utilizing an open-anode proton exchange membrane – one advantage of which is that relatively low-grade ethanol can be used. The contractor for this system is Hamilton Sundstrand – part of the giant US United Technologies Corporation – and even though this is believed to be the first submarine application of the technology - it, or something like it, has been used on space missions.

The claimed power output of the AIP system is a formidable 300 kilowatts. If this can be sustained it will give the S-80 the ability to stay under water for 40 days, albeit at low speeds. This will give the S-80 a considerable performance edge over all other present-day conventional submarines.

Navantia say that the AIP test and trials program has been going well and that all deliverables are on schedule. The first complete unit will arrive in Cartegena in April 2011 at the Land Based Test Site prior to installation. Navantia themselves are responsible for the integration of the system and has also developed – in association with another Spanish company – a carbon dioxide absorption mechanism.

A critical part of a submarine is its combat system and sensors. For this Navantia have turned to Lockheed Martin and what seems to be a version of their Submarine Integrated Combat System (SUBICS). Lockheed Martin say that this product has been derived from the company’s experience with the USN and use a form of words suggesting that it is very similar to the combat system on the ‘Virginia’ Class nuclear submarines. The system for Spain is described as an advanced 21st century product featuring all the most desirable features such as an open-architecture COTS-based design. It is said to be highly modular, an example being that the consoles are truly multi-purpose, where any one of them can perform any combat system task. Some have wondered whether the US would actually release one of their submarine combat systems to another country – but it must be pointed that Spain is a very close ally and also that Washington has been prepared to release one of their systems to another country – Australia.

The similarities with the ‘Virginia’ Class go beyond just the combat system architecture. The S-80 also has the same active torpedo discharge system and several of the same masts. In this regard there are some similarities to the way the Collins Class have been evolving.

Lockheed Martin are also supplying most of the sonars, including the all-important cylindrical array which has just passed acceptance tests in the United States. Other sonars are a 27 meter flank array. There are a total of six passive ranging sonars – three on each side of the hull – and three acoustic intercept sonars, as well as a mine and obstacle avoidance sonar. However, the towed array will be supplied by Spanish industry.

Navantia has their contract directly with Lockheed Martin rather than through the FMS sales process. While Lockheed has overall responsibility for the combat system, Navantia are involved in many areas of integration and this is seen very much as a team effort. The overall work share in this domain is probably 75 – 25 in favor of the US company.

There are two land based test sites, one in the US and the other in Spain. Like the remainder of the program, the combat system work is said to be on schedule and so far without major problems.

Interestingly even though Spain could have purchased the US Mk 48 ADCAP heavyweight torpedo, the Armada chose on performance grounds to select the Atlas Elektonik DM2A4. The future Tactical Land Attack Missile has not yet been selected.

Many of the performance characteristics of the S-80 are classified and the publicly available information is that it will have a top underwater speed of greater than 19 knots and a diving depth in excess of 300 meters. Like all modern submarines it has been designed to minimize radiated noise by isolating as many items of machinery as possible. The use of a seven-blade skew-back propeller – the choice of many navies – will reduce cavitation. In essence the S-80 will be very quiet.

Finally, Navantia has established a good relationship with the Royal Australian Navy as a consequence of being selected for the two current surface ship projects – the Air Warfare Destroyer and the Amphibious Support Ships - the latter being partially constructed in Spain. While it is early days for both of these projects, they seem to be going well – or at least those parts that are Navantia’s responsibility. Obviously the company is also a serious contender for SEA 1000.

APDR at a glance