Firstly, let me note that 2k3 thrusters are "magic" in terms of performance. Any thruster with the implied exhaust velocity would melt like a candle in a blowtorch.

However, given the calculation that one "burn" is about a dV of 1.4 kps, then for a planet of density 1, 1 burn per world size is the mathematically correct dV to lift off. If the world isn't the same density of Earth, the number of burns should scale linearly. So to lift to orbit from a size 10, 1.2 Earth density world should take 12 burns.

If you have a spaceplane type design, with an airbreathing engine, then you basically get a "free" burn of dV in the early stages.

Realistically, SSTO from an Earth size world is darned difficult.

Using the real equations, in round figures, each burn, using a hydrogen/oxygen rocket, is about 27% of the mass of the vessel. However, as Traveller is a volume based system, the first burn is 59% of the volume of the vehicle (assuming the rest is sg1). Say 60%. If you have a 1,000 dTon starship, the first burn costs 600 dTons of fuel. Things pretty quickly get impossible.