The Saturn INT-20 was a proposed intermediate-payload follow-on from the

Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

Saturn V The Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, had multistage rocket, three stages, and was powered by liquid-propel ...

launch vehicle. A conical-form interstage would be fitted on top of the

S-IC The S-IC (pronounced S-one-C) was the first stage of the American Saturn V rocket. The S-IC stage was manufactured by the Boeing Company. Like the first stages of most rockets, more than 90% of the mass at launch was propellant, in this case RP ...

stage to support the

S-IVB The S-IVB (pronounced "S-four-B") was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 rocket engine. For lunar missions it was fired twice: first for Earth ...

stage, so it could be considered either a retrofitted

Saturn IB The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, 43,3 ...

with a more powerful first stage, or a stubby, cut-down Saturn V without the

S-II The S-II (pronounced "S-two") was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen (LH2) and liquid oxygen (LOX) it had five J-2 engines in a quincunx pattern. The second stage accelerated ...

second stage. Three variants were studied, one with three F-1 engines in the first stage, one with four, and one with five.

Performance

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. Using the original five-engine S-IC would require three engines to be shut down 88 seconds after launch, with the remainder of the first-stage flight flown on only two engines. This meant that a considerable amount of the firing time would be carrying three engines of "dead weight". As a consequence the extra payload over a four-engine variant would only have been about one thousand pounds, and the extra cost and complexity of the fifth engine was unjustified. A four-engine variant would launch with four engines firing and shut down two engines 146 seconds after launch. The remaining two engines would burn until first-stage shutdown 212 seconds after launch. This variant could put approximately into a 100

nautical mile A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute ( of a degree) of latitude at t ...

(185 km or 115 statute mile) orbit, versus around for the three-stage Saturn V. The three-engine variant would burn all three engines up to first-stage shutdown at 146 seconds after launch. This variant could put approximately of payload into a 100 nautical mile (185 km) orbit, around 2.5 times the useful payload of the Saturn IB. Both three- and four-engine variants would therefore have provided useful payload capacities (

Saturn C-3 The Saturn C-3 was the third rocket in the Saturn (rocket family), Saturn C series studied from 1959 to 1962. The design was for a three-stage launch vehicle that could launch to low Earth orbit and send to the Moon via trans-lunar injection. ...

) intermediate between the Saturn IB and Saturn V, and re-using Saturn V components would reduce costs and simplify ground operations compared to building an entirely new launcher in that payload range.

References

{{Saturns Apollo program Cancelled space launch vehicles Saturn V

Performance

See also

References