What confuses me is some of the conflicting statements I see:
- "Exist only 'on paper' versus MOTS/'in the water'"; yet
- "Upscaling and/or changing a sub is not a simple process" (i.e. inc. evolved Soryu)
It sounds to me like making the Soryu into what we need is itself no simple project, yet by some is being sold as otherwise. I can see all solutions hitting some pretty big hurdles, and all having their issues ironed out eventually (with differing time frames) provided the fundamentals of the design is sound and that the right people are involved to do so.
I can see there being a balance that needs to be struck, whereby a solution is available in a time frame by which they're needed (i.e. Collins really need replacing) versus a solution that provides a better platform over the long-term (i.e. a design with future adaptation/capabilities in mind). I guess the other option is don't worry about a long life, just get something sorted with a shorter life and replace them earlier (the model Japan is following?)
As I understand it, there is no MOTS solution which meets RAN needs, therefore anything selected would need to either be modified to meet RAN requirements, or be designed from the start to fulfill the RAN requirements.
However of the three offerings (French, German, and Japanese) the
Soryu-class sub is an in-service design and in terms of size, displacement, and capabilities, fairly similar to what the RAN is looking for.
The Germans do have extensive experience in designing and building, or overseeing foreign construction of conventional submarines. However, this experience involves subs roughly half the displacement that the RAN seems to be looking for. Additionally, RAN subs need to be capable at operating effectively when very far from their bases. It is not just a matter of being capable of long transits, the sub must be able to operate for a period of time once on station, and then be able to return home. In order to accomplish this, a notional "Type 216" sub has been designed which, on paper at least, resembles the current capabilities of a
Collins-class sub and other large conventional subs. IIRC what is of concern though, is the
Collins-class was basically an enlargement of a Swedish
Vastergotland-class sub from the experienced Swedish sub builder, Kockums. As was found out after the
Collins-class first entered service, changing the displacement and dimensions impacts how a sub operates and performs. It is not just as simple as increasing the dimensions and adding extra buoyancy. Get the sums wrong and the sub becomes a diving bell, like the Spanish
S-80-class sub. Or instead of being a quiet conventional boat, the flow noise could be sub that the sub sounds like an underwater music festival...
As for the French proposal... It might be of roughly the right dimensions and displacement, being based off their
Barracuda-class SSN but conventionally powered. However, the first of the SSN's is still being built, with the programme being behind schedule and suffering cost overruns to my knowledge. To change the design from a nuclear to conventionally powered sub would involve significantly reworking the entire vessel, since where displacement would be within the vessel would change. The designers would need to take into account how the vessel's trim could/would change as diesel fuel is consumed during operations, the heat and power management would need to all be re-done, etc. From my POV, in many respects the redesign work would require everything except perhaps the outer hullform to be scrapped. And then there would be the issues with IP firewalls between French and US-sourced kit, etc.
A modified version of a Japanese
Soryu-class would of course need to be redone to take into consideration kit the RAN wants which might be different, as well as what kit is required to use RAN sub conops. However, that should require significantly less work, and therefore less risk, than switching from a nuclear reactor/powerplant to a diesel-electric one.
