Comment One-shot motor (Score 4, Insightful) 73
So it's super-efficient and all... if you intend to move no farther than 10 ft forward.
For greater distances, you could, say, keep the balloon constantly inflated with some kind of pump. And then, to save unnecessary weight and complication, you could do away with the balloon and let the pump shoot out the back of the vehicle directly.
I shall call my invention a hydrojet. Genius!