I think you might have a misunderstanding of the application of the rocket equation. high mass flow rate * high exhaust velocity = high thrust. You may be confused because current high exhaust velocity engines tend to be hall effect thrusters with low mass flow rate.
That's why I like my fusion-reactor-core maneuver drives. In any kind of atmosphere, high thrust is possible without burning much in the way of fuel (water). You just squeeze the incoming atmosphere past the REALLY hot reactor core and what comes out the back in thrust. These reactors are fueled by very small quantities of rare isotopes, which isotopes seldom run out before the reactor itself needs replacement.
Since I allow jumps without need of any fuel (just power), my ships only burn significant quantities of onboard fuel while traversing from low orbit to jump point and vice versa. If you want to travel to anywhere much beyond the jump point within the same star system, it's a very good idea to make a microjump . . . unless you want to spend a LOT of time coasting most of the way there and back.