Germans did it first... (Score 1)

I don't remember all of the facts, and someone may have already mentioned it, but the Germans used this back in WW1 for torpedos. Very effective. Not bubble - less, though. Think about it, the combustion process generates gas. You will always have extra gas that must be expended. Additionally, the deeper you go, the higher pressure the gas must be, which really robs the efficiency of the motor. There would be an absolute limit to depth. Re-breathers really work differently - they scrub the CO2 and add O2. The CO2 doesn't need to be removed for operation with an engine. FYI, Diesel Subs only use the diesels to recharge the batteries while they are on the surface. Once under water, they run off battery. Interesting approach, but limited application. Any one heard of other modern app's?