Pacific 2010: Making the Future Submarine move | ADM Dec 09/Jan 10

There is much research to be done about what local and overseas players can offer in terms of technology, schedule and cost.

But Defence needs to ensure that the missions are driving these requirements, not the debate over what size the hull should be or where the combat system comes from.

Katherine Ziesing | Canberra

The heated debate about the costs and capability of the Future Submarine is well underway.

Former ASC CEO and managing director Greg Tunny kicked off the cost debate in 2006 at the Submarine Institute of Australia (SIA) conference outlining how six evolved Collins class would cost around the $13 billion mark.

A paper at the end of 2009 from Andrew Davies of the Australian Strategic Policy Institute and Sean Costello from Millar Costello Consulting put the cost of 12 Future Submarines potentially at $36 billion.

"In order to have a boat in the water for sea trials by 2022 and in service by 2025, Australia has barely seven years in which to determine the design and capability of the Collins class replacement," the ASPI paper points out.

"In that relatively short time, decisions have to be made about the capabilities of the boats and the technologies that will be incorporated into them.

"Experience in major military R&D projects the world over suggests that entering the build phase with changeable requirements and/or unproven technologies will significantly increase the risk of cost and schedule blowouts."

But what are the missions of the Future Submarine?

Surely the missions will drive the requirements for a project destined to be the most complex and expensive Defence procurement exercise Australia has ever undertaken as Minister for Defence Personnel, Materiel and Science Greg Combet has acknowledged.

The 2009 White Paper Force 2030 outlines numerous mission roles for the Collins replacement.

"The Government has decided to acquire 12 new Future Submarines, to be assembled in South Australia.

"This will be a major design and construction program spanning three decades, and will be Australia's largest ever single defence project.

"The Future Submarine will have greater range, longer endurance on patrol, and expanded capabilities compared to the current Collins class submarine.

"It will also be equipped with very secure real-time communications and be able to carry different mission payloads such as uninhabited underwater vehicles.

"The Future Submarine will be capable of a range of tasks such as anti-ship and anti-submarine warfare; strategic strike; mine detection and mine-laying operations; intelligence collection; supporting special forces (including infiltration and exfiltration missions); and gathering battlespace data in support of operations.

"Long transits and potentially short-notice contingencies in our primary operational environment demand high levels of mobility and endurance in the Future Submarine.

"The boats need to be able to undertake prolonged covert patrols over the full distance of our strategic approaches and in operational areas.

"They require low signatures across all spectrums, including at higher speeds.

"The Government has ruled out nuclear propulsion for these submarines."

"In the case of the submarine force, the Government takes the view that our future strategic circumstances necessitate a substantially expanded submarine fleet of 12 boats in order to sustain a force at sea large enough in a crisis or conflict to be able to defend our approaches (including at considerable distance from Australia, if necessary), protect and support other ADF assets, and undertake certain strategic missions where the stealth and other operating characteristics of highly-capable advanced submarines would be crucial.

"Moreover, a larger submarine force would significantly increase the military planning challenges faced by any adversaries, and increase the size and capabilities of the force they would have to be prepared to commit to attack us directly, or coerce, intimidate or otherwise employ military power against us."

Plus there is the confirmation that the Future Submarine will be fitted with a ‘strategic strike option which will occur through the acquisition of maritime based land attack cruise missiles' with the Raytheon produced Tomahawk touted as the leading contender.

Since these boats won't be in the water for well over a decade, such speculation seems somewhat hasty.

The boat outlined in the White Paper aims to re-establish the capability edge that Australia lays claim to in the region (elements within the SIA membership have argued that this edge has been lost somewhat due to the reliability issues plaguing the Collins class and the acquisition of European made submarines by neighbours).

There is little difference in the White Paper about which of the characteristics outlined are required versus desired.

If the complete list of mission objectives and technology capability is to be addressed, there are many complex issues at play.

The SEA 1000 project office led by Rear Admiral Rowan Moffitt has much hard work ahead of it as gathers information.

A Defence spokesperson confirmed that the Sea 1000 office had 20 people currently on board with more to come in 2010.

In terms of what has been ruled in or out apart from the nuclear aspect, there is little information coming from Defence about thinking, aside from commissioning the RAND Corp study into domestic design capability.

The government is due to receive the report in February this year.

A Defence spokesperson confirmed to ADM that the report would be released to the public ‘after March next year'.

"It is too early in the process to have ruled any system out," BMT's manager of marine systems Andrew Compson said.

"The Swedish Stirling, the French MESMA and the German Fuel Cells are now all proven in service and even the modern CCDs have seen significant development from various manufacturers.

Having said that I do not believe that including AIP in the Future Submarine is a foregone conclusion - there is a lot of trade-off and modelling to be done yet, including analysis of improving battery technologies."

The statement that the government has ruled out nuclear propulsion as a power source has started a conversation about what will power the Future Submarine.

Air Independent Propulsion (AIP) is the holy grail of conventional submarines.

The ability to sidestep the necessity to ingest air, at or near the surface of the ocean, to support power generation for all systems, is crucial in maintaining the stealthy edge of a submarine.

Not having to come up and snorkel for weeks on end, much like a nuclear submarine, is the goal.

There are four options out there to power the batteries needed in a conventional submarine, with a few variations on the theme.

These are:
• Closed cycle diesel (CCD)
• Stirling engines
• Fuel cells
• MESMA (Module d'Energie Sous-Marin Autonome), an ethanol burning engine.

The one thing these systems have in common is the need for large amounts of liquid oxygen or LOX to be stored aboard and all but fuel cells also need to discharge the by-products of combustion.

Fuel cells do need a supply of H2 in order to operate as well.

These technologies are also heavily reliant on batteries, regardless of their shape or makeup, a subject that ADM will explore in a later edition.

CCD
This technology is a straight forward development based on diesel engines usually built into submarines, but the CCD plant is laid out for a power output significantly lower than that known for air-dependent diesel generator sets of submarines due to the limited amount of oxygen which can be carried on board.

The diesel engine is driven with diesel fuel and artificial air, composed of oxygen, carbon dioxide and argon, which are needed to adapt the gas mixture's adiabatic exponent to that of atmospheric air.

The exhaust gas is cooled down and led into the absorber, in which carbon dioxide is dissolved in seawater.

The exchange of water between the exhaust gas circuit at roundabout five bar and the surrounding sea at outer diving pressure is controlled by the water management system (WMS) with lowest possible auxiliary power consumption.

Afterwards water is separated from the remaining gas mixture and oxygen and argon are added in order to again create an artificial air.

An earlier development stage of this system has already been tested successfully on board a submarine in the 1990s.

Since at that time the German Navy decided in favour of the fuel cell system, the further development of the CCD system was suspended for roundabout a decade.

A few years ago these activities have been resumed, resulting in a land test rig featuring the latest development stages of all this system's components, which has just recently been put into operation.

CCD systems currently in service are more related to torpedoes than submarine power requirements due to the volatility and high speed/discharge levels associated with the hydrogen peroxide used.

The lack of CCD systems in service on the global market is telling.

MESMA
French shipbuilder DCNS has spent the last decade developing MESMA, based on a closed-cycle steam turbine.

It is essentially a modified version of their nuclear propulsion system with heat being generated by ethanol and oxygen.

In essence you have a conventional steam turbine power plant, which is powered by steam generated from the combustion of ethanol and stored oxygen.

This pressure-firing system allows the exhaust, carbon dioxide, to be expelled overboard at any depth without an exhaust compressor.

This power plant can also be retrofitted via a plug-in extension during a full cycle docking period.

The first vessel equipped with MESMA was the Pakistani Navy's Hamza, an Agosta 90B-class boat, license-built in Karachi, Pakistan.

With MESMA, ethanol is burned with oxygen in a combustion chamber at a pressure of 60bar and a temperature exceeding 700 degrees.

The heat is then transferred to a secondary circuit, in which the water/steam passes through a Rankine cycle loop (converting heat into work).

The turbine drives a generator, which produces the electric power output.

The combustion's products of the first circuit are either stored on board (water) or released to the surrounding sea water (mainly CO2).

While the power output from MESMA is significant, the efficiency of the system has been questioned due to the multiple energy transfers and the associated drawbacks of waste heat (IR signature concerns) and high oxygen consumption (space for the LOX tanks).

DCN currently offers two submarines for export with a MESMA option:

• The Agosta 90B-class: diesel-electric submarines, with an option to include an air-independent propulsion (AIP) system;

• The Scorpène-class: diesel-electric submarines, jointly developed with Spain's Izar (now Navantia) Shipyard, are offered in three versions:
- Scorpène Basic without an AIP system;
- Scorpène Basic-AIP with an AIP system as the secondary power source;
- Scorpène Compact with an AIP system as the primary power source.

Scorpène Compact is a shortened version of Scorpène Basic, and is designed for use in littoral waters.

Stirling Engine
The Stirling engine from Kockums is an externally heated engine using the Rankine cycle loop again. Heat is generated in a combustion chamber by burning diesel and LOX.

The Stirling engine turns a generator that produces electricity for propulsion and/or to charge the vessel's batteries.

The AC is rectified in the generator control cabinet and connected to the submarine DC mains in parallel to the battery.

The engine together with the alternator and the auxiliary equipment is designed as a closed module.

The module itself is covered with a sound-reducing hood.

Exhaust gases from the combustion process enter a cooling circuit and are then discharged overboard.

The Kockums-built AIP system was first tested on the refurbished submarine Näcken in 1989.

Today, three Gotland-class subs (Gotland, Uppland, and Halland) are fitted with Swedish Stirling cycle engines.

The Gotlands are powered by hybrid diesel-electric propulsion units, with the Stirling engine supplementing the conventional diesel-electric system.

The Stirling engine turns a generator that produces electricity for propulsion and/or to charge the vessel's batteries.

The Gotland was delivered in 1996.

Submerged endurance (without snorkelling) for the 1,500-tonne submarine is 14 days at five knots.

Kockums have also delivered Stirling engines to Japan for all of their new submarines.

The first submarine, Soryu, in the class was launched on 5 December 2007 and was delivered to the Japanese Maritime Self Defence Force in March 2009.

The Stirling engine has been tested on a shore rig for the Collins class as part of the research effort into the upgrade program.

Fuel cells
Polymer-Electrolyte-Membrane (PEM) Fuel Cells are known for the efficient conversion of chemical energy stored as hydrogen and oxygen into electricity.

Comparative studies of fuel cells and other air AIP systems such as Stirling engines, closed cycle diesels, and steam turbine systems in conventional (non-nuclear) submarines have shown the superiority of the low temperature fuel cells to combustion-based solutions.

The PEM fuel cell was developed by HDW together with Siemens to provide a new generation of conventional submarines with an AIP system enabling heretofore unattainable durations for submerged operations together with exceptional acoustic performance.

Siemens PEM fuel cells are based on metal technology with a compact design, meeting the volume constraints of the submarine designer.

Additionally, the technology allows high power density together with excellent thermal management of the cells for signature management and discharge of the by products which is water.

The two fuel cell designs currently installed in active submarine construction programs are the BZM 34 and BZM 120, operating in the rated power range of 34 and 120 kW respectively.

The BZM 34 was designed for the Type 212 submarine, which has been delivered to both the German and Italian Navies, it has been successfully integrated into a fuel cell power plant configured to achieve redundancy.

The subsequent development of the BZM 120 enabled an application suitable for the Type 214 export submarines in addition to upgrade or retrofit programs of previous submarine designs (e.g. Type 209).

LOX and hydrogen are stored in metal hydride canisters to feed the fuel cell power plant.

Storage quantities are sufficient to enable continuous production of electricity and support sustained submerged operations measured in weeks.

Like all AIP systems, fuel cells generate electricity for low speed propulsion, the operation of the electrical equipment during silent running and for recharging the battery. In the case of high power demand, e.g. for evasion of threats, the lead acid batteries provide burst
speed capability.

In Type 212 submarines the fuel cell stack, which consists of nine fuel cell modules, is connected directly to the ship's main power system.

Redundancy is achieved through an installed spare module which engages automatically in the event of a fault in any of the installed modules.

Reformers are the next step in submarine fuel cell technology race.

Reformers work by combining either ethanol or methanol with LOX to produce hydrogen onboard the submarine.

This hydrogen is then supplied along with additional LOX, to the fuel cell.

This approach negates the need to use heavy metal hydride containers for Hydrogen stowage and capitalises on the fact that ethanol ad methanol are readily available and easy to refuel in distant ports.

The Spanish are leaping straight to reformers on the S-80 submarine program and the Germans have been working steadily on them for some of their future submarine programs.

The fuel cell has become the system of choice for many shipbuilders and nations as seen in diagram one.

R&D efforts
Some of today's most advanced AIP developmental work, particularly on fuel cells, is being carried out in Europe.

Howaldtswerke-Deutsche Werft (HDW, in Kiel), ThyssenKrupp Marine Systems (TKMS) with HDW, NSWE, Kockums and Siemens are some of the better known companies working on this front.

Over the past 30 years, TKMS with HDW, NSWE and Kockums has delivered 122 submarines to 16 navies either as new construction or as "kits" for local production.

The US and UK, both experienced builders of nuclear submarines, have ruled themselves out of the Australian propulsion solution: the White Paper is explicit when it comes to nuclear submarines.

Defence review documents from both Mortimer and Pappas outline the need for MOTs (military off the shelf) solutions where possible and using them as a baseline for competitive comparison.

Given the relatively nascent submarine design and build capability resident in Australia, there would have to be substantial reasons why Australia would not look to leverage European technology and experience.

"The stated in-service date for the Future Submarine does not allow for a new AIP plant to be taken from concept to build," Compson said.

"Therefore, if AIP is to be utilised, then adaptation of an existing system is the way forward.

"Invariably this means that AIP is applied in support of the standard diesel-electric configuration - we are a long way from AIP providing a primary source of power.

"Of course all of the AIP technologies mentioned above are Europe based and the operational profile for submarines in that region is very different to that required for an Australian boat.

"Australia is unique in many ways and this should be remembered when considering the AIP argument."

That said, these same European shipbuilders are supplying submarines to nations that do operate in the same geographic waters as Australia.

India with its 209s from HDW and Scorpenes from DCNS/Navantia, Pakistan with Agosta's from DCNS and 214s from HDW on the way, Singapore with Kockums built Challenger and Archer class on the way, Malaysia with its Scorpenes from DCNS/Navantia and South Korea with both 209s and 214s from HDW.

The argument that only a large conventional submarine can operate effectively in our regional waters would be highly contested by numerous nations doing just that.

The demands for the future Australian submarines imply the need for increased amounts of AIP energy stored onboard.

A reformer system could be used to convert methanol into hydrogen suitable to be fed into fuel cells.

HDW is currently operating a shore based demonstrator which are being developed and tested.

Pros and cons
AIP must be seen for what it is and what it isn't.

It is a means of patrolling once a target area is reached for considerable time at slow speeds.

In littoral waters, restrictions imposed on top speed would not be an issue and AIP in this context is a great asset.

It is not a means of charging to a target area at top speed, steaming to seas far away from home to launch the relatively small payload that an Australian boat would have on board.

The raft of technology in and around the Future Submarine will come from numerous sources with even more numerous strings attached.

Australia needs to pick which strings will suit its budget and risk appetite.

Design a sub 101

In response to the increasing calls for better educated project managers, planners and engineers in the submarine domain, BMT Design and Technology runs a submarine design course aimed at the Australian market.

"The course has two primary aims," BMT's manager of marine systems Andrew Compson said.

"For Defence personnel it is aimed at creating an informed customer that understands the whole boat implications of the primary design options open to the Future Submarine.

"For industry participants the course is not designed to expand knowledge in their own field - more to give them an understanding of how their products and designs affect interfacing systems and the overall submarine design philosophy."

In terms of propulsion there are two primary modules.

‘The Energy Generation Plant' looks at all conventional boat options from diesel to AIP (and the argument for and against ruling out nuclear for Australia).

It explores lessons learnt from the diesels on Collins, the current application of AIP in the Swedish, French and German designs and the implications of applying the various options to the Australian Future Sub (including the significant issues surrounding storage of the LOX that all AIP systems use along with the required fuel).

‘The Propulsion System' module looks at the wider implications of integrating the entire energy generation and drive train.

It also investigates the ‘Australian Scenario' in terms of potential range and endurance requirements and demonstrates just how difficult it is to meet these aims with a conventional submarine (whether or not AIP is applied to increase submerged duration).

There are many other course topics which refer to the propulsion system, for example looking at implications related to boat stability.

Given the closed nature of a submarine, the feedback loops between systems are a given.

The course aims to look at how these systems affect one another in a design sense and how to best design against given requirements.