Originally Posted By: TheFallibleFiend

The same principle is what makes rockets work. It's not that the burning fuel is pushing against the air outside the rocket (although that happens, it's not what's producing the lift). Rather, the force of the expanding


That's true, but I think having the exhaust underwater would slow the release of the air, applying less force to the boat, but lasting longer. Whether that'd make the boat travel a longer or shorter distance isn't clear to me. It would probably depend on lots of other factors.

Still, there's other ways to realize that compressed air isn't much use for vehicle propulsion. Like determining its energy content.

Still again, moving a boat at low speed (and ignoring waves) takes very little force, unlike a car which always has some friction regardless of speed. I wonder if you could actually travel a lot further in a boat on the same amount of energy as a car - as long as you go slow enough. ??


Last edited by kallog; 06/29/10 05:12 PM.