The best way I’ve seen it described is that the first 9.8 m/s² of thrust only makes you hover in place. So the more g forces you generate the higher the efficiency of the engine - as long as thrust per kg of fuel doesn’t dip too far.
This all changes in outer space, where 0.01g is a valid propulsion mechanism for long duration missions.
Yup. Look at the launch trajectory of the Webb telescope. The upper stage engine was too weak for the orbital insertion and the booster had to waste energy putting it higher than need be so the upper stage engine had altitude to trade for time to keep the telescope from hitting the atmosphere.
But it was the optimum solution because that engine had a long burn to take it to L2. Hauling less engine to L2 was worth more than the loss of the engine not being powerful enough to fight gravity.
God bless the Webb team but if a manager came to me to pitch a software project with as many sequential events that had to go perfect I would have told him to fuck right off. After I stopped laughing so hard I couldn’t breathe.
I made a pikachu face when they returned the first image.
This all changes in outer space, where 0.01g is a valid propulsion mechanism for long duration missions.