The Saturn INT-20 was a proposed intermediate payload follow-on from the Apollo Saturn V launch vehicle. An interstage would be fitted on top of the S-IC stage to support the S-IVB stage, so it could be considered either a retrofitted Saturn IB with a more powerful first stage, or a stubby, cut-down Saturn V without the S-II second stage.
Three variants were studied, one with three F-1 engines in the first stage, one with four and one with five.
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The Saturn INT-20 was a proposed intermediate payload follow-on from the Apollo Saturn V launch vehicle. An interstage would be fitted on top of the S-IC stage to support the S-IVB stage, so it could be considered either a retrofitted Saturn IB with a more powerful first stage, or a stubby, cut-down Saturn V without the S-II second stage.
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, the five-engine variant of the INT-20 would be seriously overpowered and accelerate substantially faster than the Saturn V. To avoid excessive aerodynamic stress in the low atmosphere three engines would be shut down 88 seconds after launch, with the remainder of the first-stage flight flown on only two engines. As a consequence the extra payload over the four-engine variant would only have been about one thousand pounds, and the extra cost and complexity of...
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