Ahead of the class

The Devonshire Dock Hall at BAE Systems’ Barrow-in-Furness shipyard is a cavernous space, but it’s full. At one end, two massive submarines of the Royal Navy’s new attack class, Astute and Ambush, face the doors that lead out to the sea.

Astute, the first of class, is lit up by the glare of welding in its final stages of fitment before undocking for trials next month; Ambush is still only partially covered in the acoustic tiles that will help hide it from hostile shipping. At the other end of the hall, the enormous cylinders that will make up the third boat in the fleet, Artful, are swarming with engineers installing miles of pipework and tonnes of equipment. And on the other side of Barrow, the inches-thick sheets of rolled submarine steel that will form the hull of Boat 4, Audacious, have started to arrive.

For John Hudson, engineering director of BAE Systems Submarine Solutions, it’s an exciting time; the coming departure of Astute represents the culmination of over a decade of work. Indeed, his engineers are still dealing with the teething problems which, he said, are inevitable in any first-of-class submarine.

‘We’ve got a certain amount of our team now working very closely with the commissioning engineers on Astute to make sure the submarine we designed is the vessel that gets delivered,’ he explained. ‘To give an example of the sort of issues that crop up, we have a very complicated reactor control system, which talks to a very complicated platform control system, and we have to make sure that the protocols of those systems work together absolutely seamlessly.’

But despite the intense activity in the welding shops and the dock hall, the four submarines taking shape under Hudson’s stewardship aren’t the sole focus of his attention. Under pressure from fixed budgets and the uncontrollable rise in materials costs, he is leading efforts to find ways of reducing the price of the remaining three boats in the Astute fleet. Moreover, he has now put teams together to work on the design of the next class of submarine that will be built in Barrow: a new fleet of deterrent submarines that will carry the UK’s nuclear arsenal.

The intensity of the concentration on cost reduction is a new experience for the Submarine Solutions team, said Hudson. ‘With the pressure on defence budgets, this is something we’ve done a lot more than we had previously. The whole industry is facing materials price increases, notably for steel and copper, so to maintain the solution within the budget, you have to look at engineering solutions to help reduce the price.’

To do this, the team is looking outside the defence sector for equipment that can be incorporated into the vessels at a lower cost than the traditional solutions. For example, Hudson said, the final four Astute boats will use an off-the-shelf low-pressure (LP) blower, which is used to fill the buoyancy tanks that enable the submarine to surface and flush out the air supply in the case of fire.

‘Up to now, we’ve used a very well-established LP blower that’s also used on US submarines,’ said Hudson. ‘But we’ve identified a source for one which is used in agriculture for grain-blowing. It’s quieter than ours, because it has magnetic bearings, it’s slightly smaller, and we think it’s more robust and cheaper. We’ve agreed with the MoD that we’re going to integrate that piece of equipment into Boat 4 and the later boats.’

Some of the new technologies for Boat 4 onwards have such promise that Hudson is planning to back-fit them on to the earlier Astute submarines during their planned maintenance periods once in service, and will even fit them on to older classes in the submarine fleet. ‘We’ve developed a combined oxygen generation system, where we’ve put the electrolyser and scrubber into a single unit. That simplifies integration and reduces the cost, so we’re going further up the chain to keep the fleet the same.’

This ability to change demonstrates what Hudson sees as a unique feature of shipbuilding, and submarines in particular: the first of class is a prototype which nevertheless has to go into service. ‘Many industries, notably automotive and aerospace, have reduced their use of prototypes, but they still make them. We’ve never had that opportunity. We have to try get it right first time, to make something that is the prototype and the first of class. we learn from that and make refinements, small changes here and there, to deliver the same, or better, capability on future models — but at a lower cost.’

One thing in Hudson’s favour is that submarine technology doesn’t move as fast as aerospace or computing, so there are fewer issues with obsolesence. ‘A lot of the submarine is very robust and traditional engineering,’ he said. ‘We still use steam turbines and still use gearboxes, although we’re considering eliminating them on future vessels. The combat systems, however, do develop. there’s faster processing, better sensors, better analysis software, and we look at ways to fit that into the submarine on a lifecycle that’s faster than the vessel’s. But the “submariney” bits, the material technology, doesn’t move on massively quickly. We’re fitting some technology now that would have been recognisable to a submariner 30 years ago.’

However, some changes are under consideration in Submarine Systems’ current engineering design project. Known as Successor, this is the new submarine to carry the nuclear missiles which will replace the Trident system. Concept development is expected to end late next year, and the dockyard is anticipating cutting the first steel for the new boats in 2016, while the last of the seven Astuteboats is still in construction.

‘We’ve been invited by the MoD to work with Babcock Marine and Rolls-Royce to look at the Vanguard replacement, and we’re working as a multi-company team to develop concepts,’ said Hudson. ‘The SSBN — nuclear-powered ballistic submersible ship — has a different role from the nuclear-powered attack submarine, so there are things that are unique about its design. But submarine building is an evolutionary process. There are things we’ve learned on Astute that can help us improve the process.’

One matter under consideration is a new drivetrain. Even though submarines are nuclear powered, their drive system is mechanical: high-pressure steam raised by the nuclear heat spins a turbine which runs the propulsion device via a gearbox. ‘We’re looking at whether it’s time to go to an electric drive, where we generate electricity to drive an electric motor, eliminating the gearbox,’ said Hudson. The debate is finely-balanced, however. the mechanical system is well-understood, robust and reliable, but electric motors give better low-speed efficiency, which extends the life of the submarine. ‘That is clearly advantageous,’ he added, ‘but there are other ways of doing it, such as a hybrid drive that combines direct-drive steam with electric motors.’

Part of this concept development includes the building of a new generation of nuclear reactors, and for this, Hudson has to look even further ahead, to the eventual replacement for the Astute class even before the first vessel has entered service. ‘We’re looking with our colleagues in Rolls-Royce, which builds the reactor cores, at how we can provide safer and more supportable reactors for future programmes.

‘So does the proposed Successor plant match the requirement for a new attack submarine? Deterrent submarines have to go slowly and quietly, but attack submarines sometimes have to sprint. So we’re looking at thermal requirements in the reactor and propulsion chain to get a sensible solution that matches, and doesn’t block us out of, the next generation of attack submarines as well.’

The next generation of reactors will be a pressurised water design, as will the likely new civil nuclear reactors for generating base-load electricity for the National Grid. But that’s where the resemblance stops, said Hudson. ‘It’s a completely different scale, and the requirements are very different. In a civil plant, you want to load it at full power and keep it there. In a submarine, the reactor is your plant. You need to sprint and loiter, and the plant has to provide that power, so you need a plant that’s much better at load following than a civil one. The way we control the reactor is fundamentally different.’

Nevertheless, Hudson is concerned that a new generation of civil reactors might mean problems for BAE Systems. ‘It’s going to put more demand on suppliers of castings and forgings, and into the resource pool of engineers. There might be competition for resources between civil and military nuclear. We have to see whether these issues are opportunities or threats.’