[tricky_k_1972]

How big a hole in the ground is this thing gonna leave behind it on liftoff?

Well if you take the Saturn V as an example (of which this is loosely based off of), then not any. There are several ways of diminishing the thrust such as high pressure water diffusion and redirection of exhaust.

[solitas]

Well if you take the Saturn V as an example (of which this is loosely based off of), then not any. There are several ways of diminishing the thrust such as high pressure water diffusion and redirection of exhaust.

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"This engine produces 1,200,000 pounds of thrust, with an exhaust velocity of 30,000 meters per second, from a thermal output of approximately 80 gigawatts. ... With our engines giving 1.2 million pounds of thrust, we need at least five to get off the ground. But, since we have the power of nuclear on our side, we will use seven engines instead of five. ... With seven engines, we have a thrust of 8.4 million pounds available." [with 560 Gw of heat and 30 km/sec exhaust velocity]

Is gonna equal a BIG hole. :)