It’s been said so often but never actually examined in great detail – the Future Submarine Program is strategic for Japan and Australia. In speaking to the submarine community, past and present, what comes through is that cooperation with Japan results in a Future Submarine that can approach the performances of Collins but only with a completely new design and one that will definitely not be regionally superior post 2030. This is alarming and requires pause for thought.
The root-cause of this problem is that Japan does not have any technology that is, well, regionally superior. Indeed it is the reverse situation - Japan’s relative submarine capability is improved by the Future Submarine Program but not Australia’s.
The Future Submarine is strategic for Japan, but not for Australia.
The Australian Government tells us that the next generation of RAN submarines will be regionally superior because they will have higher performances in stealth, sensors, range and endurance, and of course the US-origin combat system and weapons. With superior performances in these areas, the Future Submarine can outmatch any other submarine the RAN might conceivably fight, including the nearly silent nuclear attack submarines emerging from Russia and in the future, China. In the decades to come these submarines will hunt, and be hunted by, Australian submarines and it’s important to note that the RAN may not get to choose who to fight or when – they might choose us.
"To say it in plain English, if the Collins were to fight the Soryu today Collins would kill it every time."
But what if the international partner for Australia has no better technology than we already have access to? The undeniable logic is the Future Submarine will offer performances no better than the Collins Class Submarine it replaces. An ‘Australianised’ Soryu will not be regionally superior beyond 2030. This is the critical issue.
To say it in plain English, if the Collins were to fight the Soryu today Collins would kill it every time. And there is no technology offered by Japan to suggest any evolution of the Soryu can change this situation in the future.
In lobbying Australia to accept their submarine, Japan has disclosed enough about its own capabilities in open literature to prove this. The Soryu Class, Japan’s most modern submarine, offers no improvement over Collins in any capability area – not stealth, not sonar, not range nor endurance and not combat system or weapon. Moreover, there is no objective evidence that Japan can overcome these problems with a new design. Let's examine the case for the Soryu point by point.
Stealth in submarines is mostly determined by the noise of the submarine, making it vulnerable to detection by the enemy (the noise of machinery, vibration, the flow of water over the hull and the propeller at all speeds) as well as the echo the submarine may return from enemy active sonar. For a submarine to be detected by active sonar its position is generally already localised by an adversary.
The extent to which the noise generated by on-board machinery is reduced is determined by the vibration of the equipment in the first instance, followed by the effectiveness of acoustic isolation treatments. Submarine designs since the 1980s, including the Collins, isolate vibration by a combination of treatments at each and every interface between the equipment, the hull of the submarine and the deck itself. However at least one technical paper made public by Kawasaki confirms that the Soryu does not have acoustic isolation between the deck and the hull.
This problem is clear as the production process described by Kawasaki in its own literature is incompatible with any conceivable method for acoustic isolation of the deck from the hull. Without isolation of the deck from the hull, acoustic isolation is incomplete and will result in higher acoustic signatures and loss of stealth capability. Alarmingly, the acoustic signature of the Soryu is very likely to be higher than that of the Collins and the problem is literally welded in. Fixing the problem is not straight forward as the Soryu's double hull sections constrain the available internal volume for installation of the acoustic systems. Even before the problems of range and endurance are considered, a complete redesign of the Soryu based on technology from outside Japan is required - perhaps Australia will donate this technology to Japan from the Collins?
“Every single nut and bolt forward of the thrust block in Soryu needs redesign and none of it is trivial”
As the phrase suggests, a double hull creates one small submarine inside a larger one. Only the internal hull, with the smaller diameter, is designed to resist the external seawater pressure. The external hull is comprised of tanks for fuel and ballast. A double hull can save weight but can introduce other problems.
Stealth is also related to hydrodynamic performances, which seeks to reduce drag and improve energy consumption globally – minimising use of platform equipment and the radiated noise of the submarine. Hydrodynamic performances also create a more uniform flow of water into the propeller improving both its efficiency, cavitation inception speed and other types of radiated noise at all speeds.
In this respect both classes have some problems. The Soryu has a very large fin, wide and broad hydroplanes and control surfaces all of which visibly extend beyond the line of the hull from all angles of observation. These are presumably designed for manoeuvrability or are simply a carry-over from previous designs. A second problem with the Soryu is the flank array visibly juts out from the laminar surface of the hull, presumably for better sonar performances or to manage some other integration problem. The Collins flank array is more streamlined. It of course has a very blunt bow caused by a combination of six horizontally aligned torpedo tubes and the high position of the forward cylindrical array, again a result of the quest for higher sonar performances. But the Soryu has the better overall hull form than the Collins.
A submarine can also be detected by the active sonar of an enemy. The return echo strength (or target strength) of both classes is difficult to determine as the performances of acoustics materials (tiles, paints etc) are unknown. However the large hydroplanes and control surfaces of the Soryu again provide reflexive surfaces at all observable aspects, and its double pressure at the fore and aft sections have a negative impact on return echo strength as the incoming acoustic waves can be diffracted by the structures placed between the two hulls. Here the Collins has the advantage.
Sensor performance in a submarine is dominated by the performance of the primary sensor, the passive sonar suite. Higher performances are characterised as enabling the submarine to hear fainter noises at further distances away from the submarine with such fidelity that on-board computers and software can detect, classify, track and direct weapons at the enemy. Different types of ships, submarines and even aircraft have dissimilar noise characteristics calling for a combination of sonars within a sonar suite.
Expected passive sonar performances are highly related to the overall size and design of the submarine, as these two factors together support the largest possible array antennas, minimise submarine self-noise and other interferences, and provide sufficient power and cooling to the on-board computational systems. Both classes are both equipped with at least three types of main passive sonar arrays: a bow array; flank arrays placed on both sides of the submarine; and a linear array towed streamed aft of the submarine.
The performance of a bow array in almost any submarine is most constrained by the limited available surface in the frontal lobe and the hydrodynamic performances (self-noise), particularly at speed.
The Collins and the Soryu are probably similar in performance in this area – the Collins with a high-mount Cylindrical Array and the Soryu with a slightly wider hull.
Inherent to its mounting on the hull, the performance of a flank array is especially dependant on the acoustic surface of the hull and the self-noise of adjacent ship machinery. Accordingly, the flank array’s performances are determined by how well it is physically integrated with these elements of the submarine. Observing the Soryu, the flank array is clearly compromised whereas the Collins is not.
The reduced length of the Soryu’s array, compromised again by avoiding the acoustic reflexion of forward section of the double hull, adversely affects performances and particularly detection at lower frequencies. A complete redesign of the forward section of the submarine into a conventional single hull and new sonar arrays is a solution – the solution already at sea on the Collins today.
To match the range and endurance of the Collins a completely new design from Japan is needed. The Soryu has a given range of 6,100 nm at 6.5 knots. Australia wants 11,000 nm at 10 knots and to get there every single nut and bolt forward of the thrust block in Soryu needs redesign and none of it is trivial. The underlying problem is the design philosophy in Japan, where incremental change has been introduced into successive classes of submarines over decades, must now be scrapped in favour of radical overhaul. Whether this can be done safely can only be known by the Japanese themselves and perhaps the Australian CEP evaluators.
Japan needs to remove the Soryu’s Air Independent Plant (AIP) of four Stirling engines, add seven metres to the length of the ship, completely resize the galley, accommodation and habitability spaces (Japan are the first to confess this problem and their own Navy has complained in public about on-board conditions), add more batteries, diesel fuel and at least one diesel engine and generator and redesign the ballast and trim system. Extending the hull is itself a major change and requires a complete revalidation of the design's underwater handling characteristics and weapons discharge parameters.
New major platform equipment will in turn require new main propulsion switchboards and a new power control and distribution system particularly for the new combat system network and new communications equipment.
To achieve the range and endurance requirements Japan says they will move to a new battery technology and have offered a Lithium-Ion (Li-ion) battery in place of a lead-acid battery. Li-Ion batteries have higher performances than lead-acid batteries (about 20 per cent dived endurance and a smaller improvement to indiscretion ratio), but are yet to be deemed safe enough for adoption into submarine service in any country, including Japan. Again, Australia will undoubtedly share the painful lessons we will no doubt learn as the lead customer to Japan's advantage. Combat System
The Soryu’s planned life cycle of 20 years, compared to the Collins’s 30 years, requires either faster rates of new submarine production or complete revision of the Soryu asset management plan. Both approaches require more money and long-term commitments to either replace the submarines more frequently or invest more deeply in a long-term sustainment program absent in Japan today. This requires a complete understanding of the engineering approach needed to support long-range and long-of-life submarines – something which will be provided from Australia to Japan for free.
And of course there is the AN/BYG-1 combat system and Mk-48 ADCAP torpedo. Both are at sea and proven in the Collins today and are yet to be integrated into Soryu. Australia is the lead customer again, not Japan.
"It is inconceivable that the USN would operate a submarine with inferior performances in order to accommodate an ally’s request."
The final footnote is addressing the perception the US favours a strategic tie-up with Australia and Japan. And of course, the strategic link between the US, Sweden and Australia, as proven in the Collins, has been discounted from the beginning of the CEP. Every day the media reports that the US Government is "backgrounding" Australian officials, journalists and political players that a Japan solution is preferred. Officially, the US says it is neutral and this is appropriate. Consider the reverse situation: it is inconceivable that the USN would operate a submarine with inferior performances in order to accommodate an ally’s request. Equally, the ally in question would be regarded as grossly interfering in US sovereignty.
It would cause anger.
The problem is far more serious for Japan and the US. Japanese mishandling of the Australian opportunity has now verified that not one but both principle allies of the US in the Asia Pacific need international partners to go to the next level in submarine capability.
We must not be deceived by wishing away every Japanese problem with money, time, goodwill or the US relationship. Forget culture and language problems, as serious as they are. The problem is Australia will not be regionally superior with Japan and the root-cause of this problem is lack of submarine technology and know-how in Japan.