Had they eventuated, the Attack-class submarines would have been larger and looked different to the Collins submarines - but they would have been fitted with similar propulsion systems, sensors and weapons.
Collins boats upgraded under the planned Life-of-Type Extension (LOTE) program will be fitted with German MTU 4000-series diesel engines, Jeumont and Schneider combined systems with a permanent magnet AC motor, and Wartsila Euroatlas power conversion and distribution systems.
The MTU diesels will replace the original Swedish Hedemora diesel engines.
Captain Dan LeRaye, executive director of the Collins LOTE program told the Submarine Institute of Australia conference in Adelaide this week that when LOTE equipment choices were being made, it 'made a lot of sense' to opt for technologies and products as similar as possible to the Attack-class, and it is now 'not possible' to reconsider equipment choices.
“LOTE is not just replacing the systems in the Collins-class with the same technologies as the Attack-class because they are the same as what the Attack-class was getting,” CAPT LeRaye said.
“LOTE is replacing these systems because we must. We must do it to mitigate or eliminate, in essence, the highest risk to achieving the amended planned withdrawal date.”
Procurement of long lead time items begins next year, starting with the main motor. Under the LOTE program, the six Collins boats will be upgraded, beginning with HMAS Farncomb in 2026.
CAPT LeRaye dismissed concerns that the Collins-class might not have sufficient hull life to bridge the gap to the new nuclear submarines. The final Collins vessel, HMAS Rankin, is set to retire in 2048.
CAPT LeRaye said hull fatigue was one of 'five lines of efforts' considered in scoping studies assessing whether the LOTE was viable.
“That was pretty much a deal breaker. If the hull couldn’t go the extra distance, there was no point in doing life extension,” CAPT LeRaye said. “I know that work was done. I know the answer was favourable and I know the answer was peer-reviewed by both NAVSEA and Saab-Kockums.”
The government has approved LOTE work Package A, with Package B still under consideration.
The latter could see Collins boats equipped with optronic periscopes - most likely by French company Safran – as would have been installed on the Attack submarines.
“We have completed concept designs for an optronics capability to replace the search periscope. We are ready to go if government do make a decision to proceed,” CAPT LeRaye said.
However the LOTE program will not fit air-independent propulsion (AIP) system to the class.
Commodore Tom Phillips, Navy Director-General of submarines, said much work on Sea 1000 was done on modelling of the best propulsion train and energy sources for submarines in the Australian context.
He said AIP worked well for nations whose submarines needed to travel short distances to their operational areas.
“If you put AIP into a submarine, you necessarily either make the submarine larger which reduces range and endurance, or you keep the submarine the same size and reduce battery and fuel capacity which again effects endurance and range,” CDRE Phillips said.
In addition, CDRE Phillips said the Sea 1000 modelling found the optimum for Australian circumstances was diesel electric propulsion.
“Even better than that would be nuclear propulsion,” he said. “Based on that, AIP will not be in the LOTE going forward.”