By Andrew Davies*
In a 1974 article in Aeroplane Monthly, a former Royal Air Force maritime patrol pilot wrote this about his experience flying in World War II:
During a period of 1,200 operational hours flown over a period of about a year—primarily on the Russian route—I was, alas, only involved in three attacks out of perhaps six possible sightings of U-boats, with no positive claim of a kill, and no sightings made of any German capital ship. However … we made an invaluable contribution in containing the German sea offensive against the Allied convoys traversing this area of the high seas. The constant patrolling of Allied convoy routes forced U-boats to be submerged for much longer periods than their attack plans catered for. … [T]here had to come a time when he would be forced to surface, well out of range of Royal Navy escorts and convoy air cover, in order to recharge his batteries. All this put valuable time and distance between the U-boat and his prey, and the prospects of a kill were severely reduced as a result.
First, persistent presence is important for what we now call ISR (intelligence, surveillance and reconnaissance) missions. The Catalina West flew was slow, but it could stay airborne for over 20 hours, allowing it to monitor a large expanse of water, even with just the ‘mark one eyeball’ and crude radar as sensors. The second enduring truth is that the need for conventional submarines to keep their batteries charged is a weakness that can be exploited to reduce their mission effectiveness.
That said, modern conventional submarines aren’t likely to be hunting down ships in the open ocean. They are totally outmatched by nuclear submarines in that role due to the latter’s higher speed and longer submerged endurance. And the surface vessels of today are generally significantly faster than the convoys that ploughed their way to Russia at 10 knots during WWII, making it harder for a conventional submarine to manoeuvre into a firing position.
Instead, the operational concept for conventional subs in the anti-surface role sees them lurking in ‘choke points’—bodies of water sufficiently constrained to make transiting targets come to the submarine. (Think many of the straits threading the Indonesian archipelago.)
Technology has moved on since 1945, on both the submarine and the ISR sides, but lessons from the past are still pertinent. Submarines today are stealthier, faster when submerged, and have greatly improved weapons and sensors. Those fitted with air-independent propulsion (AIP) systems have much greater submerged endurance. But improvements to surveillance systems work against those advantages.
The question becomes whether the modern conventional submarine, for all its improvements, can reasonably hope to remain covert while managing its energy state to complete its mission. Current trends seem to be swinging towards the ISR side. For a start, satellites in low-earth orbit can do wide-area searches with radar and infra-red sensors, and a submarine running its diesel engines via a ‘snort’ mast to generate electricity to charge its batteries can in principle be detected by either means. The predictability of satellite orbits means that the danger can largely be avoided by exploiting the windows between passes—though even that necessarily constrains the submarine’s options.
The proliferation of unmanned air, surface and underwater systems that we’re already seeing will pose a much greater risk to conventional submarines. Aircraft in the class of the MQ-4 Triton drone fly higher, faster and for longer (up to 30 hours) than the patrol aircraft of the past, and they have much better sensors.
Unmanned surface vessels currently in development have essentially unlimited endurance, and high-endurance unmanned underwater systems are being trialled in several countries. Worse, from the submarine’s viewpoint, is that all of those platforms, perhaps augmented by fixed acoustic arrays, can be networked together to produce a persistent wide-area system from which it will be difficult to hide. A submarine commander keen to recharge the boat’s batteries has little chance of counter-detecting silent passive sensors.
Those observations have implications for the operations of Australia’s future submarines. Based on the publicly available description of their missions (and consistent with the history of Australian submarine operations), they’ll have to transit long distances, threading one or more choke points along the way before setting up their own far-flung patrols.
They’ll potentially face persistent networked ISR around choke points and in their patrol areas, and even the open ocean won’t necessarily be safe. They may also be threatened by adversary submarines lying in wait in those choke points and, if the ambushing boats have AIP, the enemy will generally have the advantage.
I wrote about these things almost exactly two years ago. Then I concluded that these trends would force the future submarine to become a ‘mother ship’ for unmanned platforms so it could stand off at a safe distance from adversary sensors. Since then the Attack-class boats have been prescribed no AIP and relatively low energy density (though safe) lead-acid batteries.
They’ll have limited potential to deploy unmanned systems—if money is found to acquire them. And the timeline for initial deployment has slipped out to 2035. Meanwhile, unmanned systems have gone ahead in leaps and bounds and semi- or fully autonomous systems are a likely development before then.
Future sensor nets will likely be expansive, flexible and inexhaustible and I fear that Derek Woolner and David Glynne Jones are right about the early obsolescence of the Attack-class boats. But it’s not just battery technology—in fact all of the technological trends are against us, as is our unique operational requirement of having to negotiate choke points and transit long distances across open oceans to reach distant mission areas.
We are investing many billions of dollars to get small, incremental improvements in stealth, range and endurance while the counter technologies are on the cusp of massive, and potentially relatively cheap, increases in performance.
Based on all that, I’m betting now that the Attack program sees major changes or comes to an end long before the planned delivery of boat 12 in 2050. There’s a review of submarine technology pencilled in for the late 2020s but, given that the 2016 defence white paper is under review, we should do it now.
*Andrew Davies is a senior fellow at ASPI and lectures on defence acquisition at the Australian National University.First published by the Australian Strategic Policy Institute