[2] 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.

This meant that a considerable amount of the firing time would be carrying three engines of "dead weight".

The remaining two engines would burn until first-stage shutdown 212 seconds after launch.

This variant could put approximately 132,000 pounds (60,000 kg) into a 100 nautical mile (185 km or 115 statute mile) orbit, versus around 250,000 pounds (110,000 kg) for the three-stage Saturn V.[3] The three-engine variant would burn all three engines up to first-stage shutdown at 146 seconds after launch.

This variant could put approximately 78,000 pounds (35,000 kg) of payload into a 100 nautical mile (185 km) orbit, around 2.5 times the useful payload of the Saturn IB.