CAPTAIN NEMO would be green with envy. The US Navy is developing stealth submarines that have exchanged propellers for artificial muscles that let them slip silently through the water like a fish.
A metre-long prototype has already been tested. It uses shape memory alloys (SMAs) as muscles, bending and flexing the hull to generate thrust. “Initially we are focusing on unmanned underwater vehicles,” says Othon Rediniotis at Texas A&M University, College Station. But the potential is there to put people in them, he says.
The aim is to find stealthier alternatives to noisy propellers that leave highly visible wakes, says…
