The Navy's new stealth submarines might not be so stealthy after all. A top executive at the company building the subs has thrown doubt on whether cutting-edge pump-jet propulsion technology will be used as planned. The ultra-quiet technology was a key selling point for the French design that won the Government's competitive evaluation process to build the new submarines at a cost of $50 billion. Jean-Michel Billig, Executive Director of Naval Group, was asked at a naval conference in Sydney earlier this month whether pump-jet propulsion "remained viable" for the Australian submarine. He said it "could" be viable, but also...