What do you do when you cannot find a torpedo to buy? You make one. This is 6 inches (150mm) in diameter and over 5 feet (1.5 meters in length). I have the contra rotating shafts and propellers worked out. I bought 4 inch diameter or 100mm brass model boat propellers with opposite pitch. I am still working out the issues on the gear box, electric motor, controls and batteries. I will also need to find a speed boat and design a launch tube. I will be conducting sealing and buoyancy tests in the local pool this week.