Although the detailed design of the RAN’s Attack-class Future Submarines will not be finalised until 2026, Defence scientists have already been working for nearly a decade on understanding and assessing the materials likely to be used in their construction.
While later builds may eventually benefit from technical developments such as additive manufacturing using 3D printing, the focus of specialists within the Maritime Division of Defence Science and Technology (DST) remains very much on the materials that are currently in the process of selection, and ensuring they are fit for purpose.
Producing the steel alloy for the hull structure is one of the most challenging aspects of submarine construction.
DST points out that this material has to be capable of withstanding the stresses bearing on it as a result of submarine manoeuvres and underwater explosions. It and the welds used to join sections must have strength under tension and compression at all relevant thicknesses of plate, and it must exhibit high fracture toughness.
The material also needs to be corrosion resistant to withstand constant immersion in salt water, and have low-level magnetic properties to ensure low likelihood of detection by electro-magnetic sensors.
“We’ve had a program running from the early days of the Future Submarine program, looking at certification of Future Submarine steel,” Dr David Kershaw, Chief of DST’s Maritime Division explained to ADM.
“This program has involved us understanding the fundamental properties of potential submarine steels, going out and doing blast tests to ensure that the two overseas steels that are being used for submarines, and in particular the steel that has been developed in Australia, are able to meet the strength requirements for our Future Submarine.”
DST’s involvement with submarine steel actually stretches back more than three decades, through its predecessor the Defence Science and Technology Organisation (DSTO) and its role in testing and certifying the steel used in the hulls of the RAN’s six in-service Collins-class submarines.
These are constructed from a high-tensile micro-alloy steel created by Swedish specialist steel manufacturer SSAB but subsequently modified for Australian manufacture and produced by NSW company Bisalloy Steels, the country’s only producer of high strength quenched and tempered steel plate, and steelmaker Bluescope.
“The steel needed to have particular characteristics. Strength, toughness and shock loading impact resistance were vitally important but the steel also must be readily cold-formed, fabricated and welded,” a Bisalloy spokesperson said.
The outcome, after input and rigorous testing by DSTO, was the Australian grade BIS 8 l 2EMA plate that is weldable, micro-alloyed, high yield stress steel with excellent low temperature impact properties. It is also reportedly a lighter chemistry and easier to weld than the HY-80 or HY-100 nickel-alloy steel used in contemporary submarine construction projects.
Advanced welding technology developed by DST produced a fracture control methodology which ensured that optimum resistance to shock loading was built into the new submarines. It also meant that Australian industry was able to perform all Collins-class steelwork maintenance and repair.
Fast forward, and in February this year Bisalloy Steels received an initial order from Naval Group Australia, the FutureSubmarine design and build partner, for 250 tonnes of specialised high performance steel plate. This will be utilised for the first of up to three qualification phases which will test the company’s ability to maintain quality in production.
February’s order followed successful testing the previous month of trial material that confirmed the company could manufacture steel which met all targeted Attack-class specifications, the company said.
DSTG testing role
Deciding whether or not independent testing of materials is required is discussed between DST, Capability and Sustainment Group (CASG), and Naval Engineering, Dr Kershaw says.
“Often our role is to advise whether we can rely on someone else’s certification, but in key critical areas we absolutely want to do the testing so that we have independently verified what is going on.
“We have the suite of analysis skills, tools and equipment to provide the independent verification that is sought for the certification of Future Submarine steel.”
This resource was the outcome of DST’s 2013-2018 Strategic Plan in which careful consideration was given to the science and technology capability areas that would be needed to ensure DST had the capability to support the head of Naval Engineering in this certification process.
“We have a core of the necessary skills within DST and we have an ongoing research program to ensure that these skills remain up-to-date and world-class,” Dr Kershaw noted.
“We also have a very good understanding of who our key partners are either overseas or in-country to ensure that Australia has access to the necessary skill and knowledge base to certify the materials we use.”
The level of Commonwealth expertise available to assess materials proposed by Naval Group for different systems was also stressed by Rear Admiral Greg Sammut, head of the Future Submarine program, at Senate Estimates in April.
“Given that we do have experience in submarine design and we certainly have a lot of experience in the way those systems perform on Collins in our unique environments, we are well-placed with the expertise that we’ve got in the Future Submarine program to assess what Naval Group is advising us and making informed decisions about their recommendations.
“We can be confident that the design choices we end up with are going to best suit our requirements given our understanding of the environment in which our submarines operate and the expertise we have in our team.”
The possibility of DST developing uniquely-Australian enhancements for the Future Submarine is, understandably, not a subject Dr Kershaw wishes to pursue in a public forum. But he acknowledges the in-country development of anechoic tiles for the Collins-class after the US and UK declined to share their IP with Australia was one example of DST producing the world’s best technology.
The warm water environment in which Australia’s submarines generally operate creates some unique environmental pressures on maritime platforms.
“Paints and coatings and fabrics behave very differently in tropical waters and tropical conditions,” Dr Kershaw said.
“Our approach in looking at whether we need to invest in the capability for independent certification has three considerations. One is whether we need to maintain that scientific capability in order to assist with the certification of the design or material.
“The next consideration is whether we really have to have a very solid understanding of those Australian operating conditions, and biofouling is one example.
“And then we have another consideration where we have niche world-class expertise and we can work in those areas to either insert into our programs where we can, or we work with our partners transferring that technology into their programs.”
Partnering
One such example is a three-year collaboration program signed by DST in May with universities and industry for research into potential new acoustic materials.
A team comprising researchers from DST, the University of Melbourne and RMIT, and industry partners QinetiQ and Matrix Composites and Engineering will develop prototype stealth materials.
The $1.5 million program is supported by the DST-managed Next Generation Technologies Fund with an investment of $730,000, a miniscule amount in the context of the naval shipbuilding program but a pointer to the Fund’s intention to broaden seed funding countrywide for acoustic and materials sciences, engineering and technological innovation to develop new defence technology solutions.
Looking into the not-too-distant future, Dr Kershaw envisages the development of multi-functional coatings in which the skin of an unmanned underwater vehicle (UUV) could also act as its sonar sensor while also providing dynamic adaptive camouflage.
The emerging area of integrated computational materials engineering (ICME) was highly promising in terms of what could be done with metallic and polymeric materials.
“As we use our computers to design very advanced lightweight but strong structures we can have some confidence they will have the properties that we expect them to have because of our knowledge of the base material,” Dr Kershaw explained to ADM.
“So this starts raising all sorts of questions for surface ships and for submarines. Can I now start to build parts of my vessel to have the same strength as a more traditional material if they’re very much lighter? Obviously that has huge attractions for surface ships with masts and what you’re putting up high.”
The development of additive manufacturing would soon raise the possibility of sending a ship or submarine to sea with a 3D metal printer and a bag of feedstock, allowing a part to be printed to order. But how would that part be certified?
“Today, if I had a non-safety-critical part and I was reasonably confident about how the printer could operate, I might use it. But if I was printing an elbow and a joiner for a high-pressure hydraulic line or a high-pressure steam line, would I actually want to use a 3D printer part in that environment?”
As an example of where modern materials can lead, Dr Kershaw points to an increase in very small-scale demonstrations of metamaterials – actually designed structures rather than a material – some of which can bend electromagnetic radiation, including light, around an object, ‘cloaking it’ and rendering it seemingly invisible.
Technology futures
And for a futuristic view of submarine design, materials and capabilities, the Royal Navy recently tasked UKNEST, a forum founded in 2005 to promote the engineering, science and technology interests of UK naval defence, to produce some blue-sky concepts involving new technology.
The primary concept of the UKNEST team was the Nautilus 100 mothership, a design sporting a whale shark mouth and a manta ray body to enhance speed and stealth.
The 3D printed acrylic hull would be bonded to super-strong alloys to withstand depths of more than 1,000 metres. For additional stealth the Nautilus would have a skin of anechoic, nanometer-thin graphene scales bonded with a piezoelectric material to enable real-time adjustments and dynamic controls.
Thanks to advanced autonomous systems and “neuro-interfacing” allowing control by thought, the submarine would only need a crew of about 20. Steering and depth control would be by means of flexible wingtips able to alter their shape like a living fish.
Hybrid algae-electric propulsion would power stealth cruising at 30 knots, while Casimir-effect force batteries using an advanced quantum effect to store energy would provide large amounts of power for short speed bursts of up to 150 knots.
These would be facilitated by the ability of the Nautilus to encapsulate itself in a super-cavitating air bubble created by lasers on the leading edge of the mothership that would boil the water ahead of it while outlets stabilised and directed the flow over the hull.
Although the Nautilus would be equipped with torpedoes for defence, its main armament would be Flying Fish drones with wings doubling as fins, and propelled by a combination of microturbines and plasma batteries.
This design would enable the Flying Fish to dive immediately it detected radar or to fly just above the sea surface when it detected active sonar. Payloads would range from conventional explosives, cluster warheads and shockwave emitters, to electromagnetic pulse (EMP) weapons.
Implausible, impractical, fantasy – possibly. Yet it’s worth remembering the advances in technology that have flowed since the launch of the USS Nautilus, the world’s first nuclear-powered submarine, just 65 years ago. The world of science fiction is quickly becoming more viable as technology progresses.
This article first appeared in the August 2019 edition of ADM.