Australia is about to build a new class of submarines, which will probably be in service well beyond 2050. How is their world likely to change over that long life span? What forces are currently driving submarine technology?
We can look back to form some idea of how technology affects submarines. A Collins class submarine, as she is currently equipped, is far more effective than she was when she was designed and built, mainly because her computer combat system is far more sophisticated. This greater capacity could be built into a submarine of fixed size and volume because the change came out of far more capable computers and their chips – out of Moore’s Law, which posits that computer power doubles every 18 months, if not more frequently. As currently configured, the Collins class (like US submarines) can be upgraded periodically as computer power continues to grow, a process the US Navy calls ARCI – Acoustic Rapid COTS Insertion.
Here the point is that commercial (COTS) hardware, which is less and less expensive, gives the system the potential to use more and more powerful software. At the end of the Cold War the US Navy realized that it could not afford a new-generation sonar array – but given ARCI it could make far better use of what it had and could buy. Similarly, the Collins class was built with a set of sonar arrays which is difficult to change – but processing is another matter.
This trend is likely to continue for some time; it is by no means clear how and when Moore’s Law, like all other expressions of technical growth, will peter out. Similarly, the Collins class is currently armed with a far more powerful torpedo than it had at the outset. The change in torpedoes was relatively simple because submarine fire control was software-based and could therefore be modified inexpensively.
What comes next? Submarines are increasingly expensive, both to buy and to operate. They are valued because they are, in effect, invisible, as nothing else in the defence world is. That seems likely to continue, particularly if Australian submarines often operate in coastal areas in which submarine detection is even more difficult than in the open ocean. Invisibility makes submarine reconnaissance, generally sopping up radio signals, an extremely important mission. A potential target is generally aware of satellite orbits, for example, and may shut down crucial communications when they are in range. That applies even more strongly to nearly all airplanes, manned and unmanned.
An invisible submarine offshore is a very different proposition. Moreover, it has the capacity to make sense of what it picks up, and therefore to adjust its surveillance accordingly. Australia in particular relies heavily on intelligence for security, because the country wields a relatively small but extremely sophisticated defense force. It has to be in the right place when needed.
A very expensive submarine can be in only one place at a time – or is that true? In the past it certainly was true, but the emerging class of unmanned vehicles, both airborne and underwater, promise something more. For example, one might imagine a submarine offshore launching a cloud of expendable miniature air vehicles to listen to radio signals and transmit back to the submarine.
The cloud can cover a much larger area than the submarine’s own surveillance receivers, attached to the submarine. It can also be offset sufficiently that even if the surveillance target becomes aware of the cloud, that knowledge does not give away the position of the submarine. That contrasts dramatically with current surveillance technology, in which the submarine pierces the surface with a visible mast. Current technology succeeds because a small submarine mast is often difficult to detect – but that will probably change over time. It may change particularly if countries buy numerous unmanned air vehicles for coastal surveillance.
Miniature air vehicles currently exist, although their capacity is limited though likely to grow considerably. The submarine offshore might sift what the unmanned air vehicles collected and pass the results back to Australia via a high-capacity satellite link. This is not a new idea – the US Navy was talking about such vehicles about 2001 – but it has not yet materialized anywhere in mature form. That a small air vehicle can operate more or less autonomously is very much an application of Moore’s Law.
A cloud of miniature aircraft would certainly be detectable, and might well give away the presence of the submarine. That may be undesirable because it can have political consequences. The essence of covert intelligence-gathering is that the target not be aware that it is being done. Quite aside from any question of embarrassment, the hope is that the act of intelligence-gathering will not exacerbate the crisis which has led to the surveillance in the first place.
An emerging alternative is unmanned or autonomous underwater vehicles (AUVs). They have to be autonomous because it is difficult for them to link back to the mother submarine on a continuous basis. If the vehicle runs into an underwater obstacle, for example, it has to find its way around.
The US Navy is currently experimenting with small Remus vehicles on board submarines. Previous attempts to use larger vehicles foundered because it was difficult to recover them. For example, a torpedo-size AUV died because the recovery mechanism occupied two of the submarine’s four torpedo tubes. Reportedly the current project accepts that the vehicle will have to be expended after it completes its mission. A key to using such vehicles is improvements in underwater data links, which are possible thanks to Moore’s Law.
It makes a considerable difference if the AUV can beam back what it learns without having to return to the submarine. At some point it will presumably be possible, moreover, for the AUV to return to the submarine, to be taken aboard in some efficient way. The current US Navy effort employs the Dry Deck Shelters devised in the first place to support SEALs.
The idea of intelligence-gathering AUVs is not new. About a decade ago, for example, a mock-up of a surveillance AUV carrying intercept antennas was shown at a US Sea-Air-Space show. Apparently it was not built.
More generally, AUVs can multiply (in effect) a force by adding sensors without requiring more ships. AUVs are already being used in mine countermeasures, but usually they are explained as a means of keeping sailors further away from the minefields they are trying to neutralize. The multiplier possibility deserves more attention. Right now a single minehunter typically explores an area by examining each potential mine, then neutralizing those deemed to be real. That rather protracted process can have unfortunate consequences.
For example, before landing troops a commander generally wants to know whether the beach is mined. Potential enemies generally have limited mine stocks, so it is quite possible that the area off the beach is clear. Spending weeks making sure of that is a good way to alert an enemy. At the least he can mass his own troops near the beach to massacre a landing force.
An AUV can explore a potential landing beach. It is generally small enough that it will not trigger mines; even if it does, it is expendable. Current technology may well not be up to deciding automatically that something on the bottom is a real mine, but the AUV can bring back images which human experts can examine. At the least, a mass of AUVs can show that a beach appears to have been mined, and that it may be wise to land elsewhere. The more AUVs that are used, the faster the process can run. Ideally the AUVs run underwater and, like submarines, are not particularly visible from the shore.
This is not a new idea. Remus AUVs were used successfully to examine Iraqi ports in 2003. Several navies use AUVs in mine countermeasures. What is new is the idea of deploying mine detecting AUVs in quantity from submarines, to work in parallel. If the AUVs can map a potential minefield sufficiently precisely, other underwater vehicles can be deployed to attack the supposed mines, using self-propelled anti-mine torpedoes which already exist. This sort of mine clearance can be carried out by existing mine countermeasures ships, the most important limit being their capacity for the underwater vehicles. However, the autonomous character of the AUVs suggests a future in which submarines are the best way to clear a landing zone covertly. The more covert, the less the possibility that an enemy will be able to deploy enough troops on a beach to break up a landing.
Australia generally relies on technological leverage to make up for limited numbers. The combination of submarines and AUVs offers just such leverage. Similarly, rapid covert mine clearance off a potential landing beach would make the most of the limited number of troops the Australian amphibious force can deploy at one time.
This article first appeared in the November 2018 edition of ADM.