[Dylan16807]

The more fuel you have to pile onto the rocket, the less the weight of the engine matters.

Using the chart in the accepted answer, launching with chemical engines takes 50 thousand tons at 3x gravity and 3 million tons at 4x gravity.

Now consider a theoretical engine that has a 7:1 thrust to weight ratio at 1G but sips fuel. Take a 25 ton engine, strap 10 tons of fuel to it and 1 ton of payload. Watch it go to orbit on a single stage.

A real NTR doesn't save nearly as much fuel, but it can still be useful in certain ranges.