S-IVB

Key takeaways

S-IVB belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect S-IVB to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of S-IVB from memory before moving on to harder problems.

Reference excerpt

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 orbit insertion after second stage cutoff, and then for translunar injection (TLI).

History The S-IVB evolved from the upper stage of the Saturn I rocket (the S-IV) and was the first stage of the Saturn V to be designed. The S-IV used a cluster of six RL10 engines but used the same fuels as the S-IVB – liquid hydrogen and liquid oxygen. It was also originally meant to be the third stage of a planned rocket called the C-4, hence the name S-IV. Eleven companies submitted proposals for being the lead contractor on the stage by the deadline of 29 February 1960. NASA administrator T. Keith Glennan decided on 19 April that Douglas Aircraft Company would be awarded the contract. Convair had come in a close second but Glennan did not want to monopolize the liquid hydrogen-fueled rocket market as Convair was already building the Centaur stage of the Atlas-Centaur rocket. In the end, the Marshall Space Flight Center decided to use the C-5 rocket (later called the Saturn V), which had three stages and would be topped with an uprated S-IV called the S-IVB featuring a single J-2 engine, as opposed to the cluster of 6 RL10 engines on the S-IV. Douglas was awarded the contract for the S-IVB because of the similarities between it and the S-IV. At the same time, it was decided to create the C-IB rocket (Saturn IB) that would also use the S-IVB as its second stage and could be used for testing the Apollo spacecraft in low Earth orbit. Twelve 200-series and sixteen 500-series S-IVB stages were built, alongside three test stages. NASA was working on acquiring four additional 200-series stages (as part of four new Saturn IB rockets, SA-213 to 216), but funding never materialized and the order was canceled in August 1968 before S-IVB hardware was assembled. Similarly, an order for two additional 500-series stages (for Saturn V rockets 516 and 517) was canceled around the same time.

Configuration Douglas built two distinct versions of the S-IVB, the 200 series and the 500 series. The 200 series was used by the Saturn IB and differed from the 500 in that it did not have a flared interstage and it had less helium pressurization on board since it did not have to be restarted. In the 500 series, the interstage flared out to match the larger diameter of the S-II stage of the Saturn V. The 200 series also had three solid rockets for separating the S-IVB from the S-IB during staging. On the 500 series this was reduced to two, and two small Auxiliary Propulsion System (APS) thruster modules were added as ullage motors for restarting the J-2 engine and to provide attitude control during coast phases of flight. The S-IVB carried 73,280 litres (19,360 US gal) of liquid oxygen (LOX), massing 87,200 kilograms (192,200 lb). It carried 252,750 litres (66,770 US gal) of liquid hydrogen (LH2), massing 18,000 kilograms (40,000 lb). Empty mass was 10,000 kilograms (22,000 lb)

Auxiliary Propulsion System

Attitude control was provided by J-2 engine gimbaling during powered flight and by the two APS modules during coast. APS modules were used for three-axis control during coast phases, roll control during J-2 firings, and ullage for the second ignition of the J-2 engine. Each APS module contained two 150-pound-force (670 N) thrusters providing thrust for roll and pitch, another 150-pound-force thruster for yaw, and one 70-pound-force (310 N) thruster for ullage. Each module contained its own propellant tanks of 150 pounds (68 kg) dinitrogen tetroxide and 115 pounds (52 kg) monomethyl hydrazine as well as compressed helium to pressurize its propellants.

Uses A surplus S-IVB tank, serial number 212, was converted into the hull for Skylab, the first American space station. Skylab was launched on a Saturn V on May 14, 1973, and it eventually reentered the atmosphere on July 11, 1979. A second S-IVB, serial number 515, was also converted into a backup Skylab, but this one never flew. From Apollo 13 onward, the S-IVB stages were crashed into the Moon to perform seismic measurements used for characterizing the lunar interior.

Stages built

(* See List of artificial objects on the Moon for location.)

Derivatives The second stage of the Ares I rocket and the proposed Earth Departure Stage (EDS) would have had some of the characteristics of the S-IVB stage, as both would have had an uprated J-2 engine, called the J-2X, with the latter performing the same functions as that of the Series 500 version of the stage (placing the payload into orbit, and later firing the spacecraft into trans-lunar space). The MS-IVB was a proposed modification of the S-IVB that would have been used on a Mars flyby, but it was never produced.

See also S-IC S-II S-IV Saturn IB Saturn V Apollo (spacecraft) List of artificial objects on the Moon

References Marshall Space Flight Center, Apollo Systems Description Volume II - Saturn Launch Vehicles, 1 February 1964. (Archived copy, pdf)

External links

NASA New Reference: Saturn third stage

Illustrations

Worked examples

Example 1 — a first encounter with S-IVB

Start with the simplest possible case. Write down what S-IVB claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to S-IVB before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about S-IVB ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of S-IVB

In research: S-IVB appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses S-IVB in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: S-IVB is common in secondary-school and first-year university syllabi. It links to neighbouring topics Apollo program, Impactor spacecraft, Rocket stages, so understanding it makes those chapters shorter.
In everyday life: Look for S-IVB outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study S-IVB in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what S-IVB means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain S-IVB out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is S-IVB in simple terms?

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.

Why does S-IVB matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study S-IVB?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on S-IVB.