SATURN-V for Dummies Part-2: The Machine Overview

Happy Makar Sankranti/Pongal and thank you, readers, for the tremendous love and support in my previous article on the History of Saturn-V. If you haven’t read that yet, I would highly recommend giving it a read, this will help you to get the context of this article (click here to read it). In this article, I will be giving you the machine overview and try to answer the question, what this Saturn-V actually is. So, without much further ado, let’s get to the point.

The Machine Overview: Getting the Rough Idea

Saturn-V is a 3-stage vehicle, with each stage namely; S-IC first stage, S-II second stage, S-IVB third stage, and Instrument unit. If you find the stage names confusing, don’t worry I’ll also explain the logic behind the nomenclature. But why did the rocket need 3 stages to get to the moon? The simple answer is mass management and gravity or simply the Tyranny of the Rocket Equation; a massive amount of fuel is needed to get to high altitudes, 85-90% of the rocket is just the fuel, and the rest 10-15% comprises the dry mass. In that case, it is more efficient to just expend a stage after the fuel is used up. though there are many on-paper concepts of Single Stage To Orbit (SSTO) rockets, none of them have flown yet (SSTOs will be covered in a future article). So, staging seems a wiser and better idea to get to orbit.

Saturn-V with all its stages in Houston, USA

S-IC First Stage:

The 1^st stage was 42m tall, 10m in diameter, and provided 33000kN (33MN) of thrust to get the rocket through the first 61km of ascent. The dry mass of the stage was 131000kg and, once fully fueled it weighed 2.3 million kg. Rocket-grade kerosene (RP-1) was used as the fuel for this particular stage and liquid oxygen (Lox) was used as the oxidizer. The stage had five F-1 engines in a quincunx arrangement. The center engine was fixed whereas the four outer engines could be gimballed using hydraulic systems to control the rocket.

The Boeing Company was awarded the contract to manufacture the S-IC first stage on December 15, 1961. By then, the general design of the first stage had been decided by the engineers at the MSFC. The MSFC engineers also built the first 3 test stages (S-IC-T, S-IC-S, S-IC-F), and the first two flight models (S-IC-1 and -2). The main place of manufacture was the Michoud Assembly Facility, New Orleans. Wind tunnel testing took place in Seattle and the machining of the tools needed to build the stages at Wichita, Kansas.

It took around 9 months to build the tanks and 14 months to complete a stage. The timeline may feel absurd because today, SpaceX can manufacture its Falcon-9 rocket in under 3 months, but we need to keep in mind the scale and the time of manufacture. The rocket was way bigger and way more capable than an F9 and again it was being manufactured in the 1960s and 70s, a time when automated manufacturing basically did not exist.

The largest and heaviest single component of the S-IC was the thrust structure, with a mass of 22000kg. It was designed to support the thrust of the five engines and redistribute it evenly across the base of the rocket. There were four anchors which held down the rocket as it built thrust. These were among the largest aluminum forgings produced in the U.S. at the time, 4.3m long and 816kg in weight. The four stabilizing fins withstood a temperature of 1100 °C.

Now, S-I means Stage-1, and C means, it is the third design iteration of the stage and hence the name S-1C.

S-IC stage on display at the Kennedy Space Centre

S-II Second Stage:

The 2^nd stage was about 25m tall, 10m in diameter, and provided 4,400kN of thrust to accelerate the Saturn-V through the upper atmosphere. The dry mass of the stage was 36200kg and, when fully fueled, it weighed 480000kg. Liquid hydrogen (LH₂) was used as the fuel in this stage and liquid oxygen (Lox) was used as the oxidizer. The stage had five J-2 engines in a quincunx pattern. Similar to the S-IC; the center engine was fixed and the outer four were hydraulically gimballed. 

North American Aviation was awarded the contract to manufacture S-II second stage on 11^th September 1961 (Note: it is the same company that was awarded the contract for the Apollo Command / Service Module). They were also provided with the manufacturing plant at Seal Beach, California by the government.

Interestingly, this stage when fully loaded; had only 7.6% hardware, and the rest 92.4% comprised LH₂ and Lox. The S-II stage had some very brilliant ways to contain highly volatile liquid hydrogen and even prevent turbulence due to fuel sloshing. We will surely cover them in detail in a future article.

S-II simply means Stage-2, the meaning is quite literal.

S-II stage on display at the Kennedy Space Centre

S-IVB Third Stage:

The 3^rd stage was 17.8m tall, 6.6m in diameter and could provide a maximum thrust of 890kN (S-IVB 200 series) or 1MN (S-IVB 500 series). The stage weighed 13500kg when empty and 123000kg when fully fueled. Similar to the S-II stage it used LH₂ and Lox fuel and oxidizer respectively. The stage used only one J-2 engine and was restartable. For lunar missions, it was fired twice: first for Earth orbit insertion after second stage cutoff (SECO), and then for translunar injection (TLI).

This stage evolved from the upper stage of the Saturn 1 rocket and was the first stage of the Saturn-V to be designed.  NASA awarded the manufacturing contract to Douglas Aircraft Company on 19 April 1960. At the same time, it was decided to make the Saturn-1b that would also use the S-IVB as the second stage and could be used for testing the Apollo spacecraft in the Earth orbit.

S-IVB was originally meant to be the fourth stage of the C-4 rocket (covered in the previous article), and the ‘B’ because, it was the second manufacturing iteration, the previous version used a cluster of six J-2 engines. Hence the name, S-IVB.

S-IVB stage separation in Apollo-7 mission

Instrument Unit:

Manufacturing the Instrument Unit

The instrument unit was built by IBM and was placed on top of the third stage. This was the brain of the whole rocket and controlled all the operations of the rocket just before liftoff until the S-IVB stage was discarded. Now guess what, we have a whole article fully dedicated to the sheer brilliancy of this 60s old school computer. Go, check that out!!

These were the 3 stages of the mighty Saturn-V rocket, once all the stages were built, they were vertically integrated at the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Centre, Florida. It took an average of 2 years to build a single Saturn-V and needed a giant crawler-transporter for carrying the beast to the launchpad.

The project did cost around 6.417 billion USD, with cost per launch leading up to a whopping 185 million USD (well today it would have cost $1.33 billion). If we take the inflation rate as 7.19, then this whole project would cost around $46.11 billion (as of 2021) to put things into perspective NASA’s 2021 budget is $23.3billion, and in the 60s and 70s Apollo wasn’t the only program that NASA was funding, that's a lot of money!

Though these accomplishments seem nuts, trust me these are nothing compared to the glorious fire-breathing bells that the rocket had underneath it. Stay tuned because in my next article we'll be stripping down the engines of Saturn-V. Get ready to be blown away by the marvels of modern engineering.

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To know the basics of the quantum world, astronomy, and space exploration you can check out the book "Through the wormhole" on amazon kindle by Ratnadeep Das Choudhury.

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