Pretty much. More mass to lift = more fuel = more mass = more fuel etc., plus burning fuel isn't the most efficient way of getting kinetic energy into the thing

Pretty much. More mass to lift = more fuel = more mass = more fuel etc., plus burning fuel isn't the most efficient way of getting kinetic energy into the thing you are lifting. I would say it is unsuitable for atmospheric engines because of the way it runs. Earth to Mars in 30 days will need you to be travelling at almost 90 km/second. The engine has to fire for 3 days straight because the delta v you need is retardedly high, so it pulses the engine once a minute so that the passengers don't die and the ship doesn't break up due to huge g-forces. Lifting something into orbit needs to be done fast, because most of your energy is spent counteracting gravity, not air resistance. A slow pulsing engine would not be enough to get you up.