Now going back to what has been mentioned about pumpjets, they are a useful capability for a submarine with a sufficient power budget (i.e. SSN) to have. The power budget for a diesel-electric sub is considerably smaller. From my POV this would mean that either;
- The RAN subs are fitted for/with pumpjets, but rarely if ever use them
- The French pumpjets require a significantly lower power budget to be useful
- The power generation & especially storage for the new sub will be dramatically greater, without a corresponding increase in base/hotel load
Note the last item on the this, and how this could involve CONOPS. As I mentioned previously, from existing open sources the
Collins-class sub can sustain a 4 kts submerged transit for 100 hours. This means that in addition to power consumed propelling the sub at 4 kts for 100 hours, it also means operating the various pieces of kit which make up the base/hotel load for 100 hours. I would also imagine that there was some sort of emergency reserve of power factored in, in the event that the RAN sub had to engage (or was engaged by) a hostile. It would not do for a RAN sub to finish a 100 hour/400 n mile transit and need to snort to recharge the batteries and suddenly find itself being stalked by a hunter-killer group. With some of the numbers suggested earlier (take them with a large grain of NaCl...) where doubling the speed cubes the required power, then a sudden sprint sustained for perhaps two hours, would have a power requirement similar to 100 hours at 4 kts, if a
Collins-class sub were to do it. There would of course be less power required for the base/hotel load, since there would only be two hours of that, but still, such a higher speed would drain the batteries at a tremendous rate. I admit I do not know the specifics for using a pumpjet, but I somehow doubt they are more energy efficient than a traditional propeller, otherwise there would not be just one conventional sub which was fitted. Where this gets into CONOPS is whether rapid acceleration at the cost of increased indiscretion rate is beneficial, a hindrance, or would make no difference in how the RAN will be operating the future subs.
As I mentioned before, if the capability delivered is insufficient to get a sub outside of a search box, then it might well be irrelevant for what the RAN is looking for.