 Three variants were studied, one with three F-1 engines in the first stage, one with four, and one with five.Without the S-II stage, which made up a large fraction of the mass of the Saturn V, a version of the INT-20 using an unmodified five-engine version of the S-IC booster would be greatly overpowered and accelerate substantially faster than the Saturn V. This would create excessive aerodynamic stress in the low atmosphere.Several solutions to this problem were considered.