You just don’t see much of the Saturn I launch vehicle. This launch vehicle ended up as little more than an R&D project for more ambitious Saturn technologies.

In particular, you just don’t get to see much of the damned beautiful symmetry of this rocket’s S-IV second stage and its six RL-10 cryogenic engines. It was the second rocket stage to use the new hydrogen fuel, sharing the benefits of the RL-10’s development with the troubled but improving Centaur upper stage booster, needed to get heavier spacecraft to the moon and beyond.

SA-5 fig156g
Saturn I SA-5. Oh, baby. (NASA)

Each of these early RL-10s at the time generated 15,000 pounds/thrust (6,000 kg/thrust) for a total of 90,000 pounds/thrust (40823 kg/thrust).

As potent as this cluster seemed, Pratt & Whitney, creator of the RL-10, would provide engineering data to Rocketdyne used to develop the J-2 cryogenic engine.

S-IV and S-IVB Comparisons
The S-IV’ and its six RL-10s, for all its innovation, could not outperform the single J-2 engine of the S-IVB. (NASA)

One J-2 engine delivered over 10 times the power of the RL-10 at up to 200,000 pounds/thrust (90718 kg/thrust). Five would hurl the S-II stages of the Saturn V upward at 1 million pounds/thrust (453,593 kg/thrust). One would push the S-IVB into parking orbit before being reignited to send Apollo crews to the moon.

S-IV 6411809
The S-IV stage used for SA-7. Wonderous. (NASA)

But screw performance right now.

Short of a Saturn V liftoff shredding your eardrums and filling your eyeballs with light, nothing looked more badass than the January 29, 1964 liftoff of Saturn I SA-5, the first flight of the Saturn I with an S-IV stage.

That black nose was only a large non-functional weight. I don’t care. Most others don’t either. When you search around for scale plastic and resin models to build from various places, the popular SA-5 configuration is often available, such as one from RealSpace Models.

And there’s just something very attractive about the six-engine cluster of RL-10s.

The S-IV was intended to push an Apollo Command/Service Module into orbit for earth-orbital tests. The speed of improvements to the Saturn as well as delays in development of the Command Module meant that the Saturn I would never fly a crew.

The incredible website HeroicRelics.org has a boatload of hard-to-find documents on the Saturn I, from which I shamelessly post one drawing of the SA-5’s S-IV.

Saturn I S-IV Drawing

Maybe it was the also the scalloped interstage that appeared on some stages that adds to the engineering majesty of the S-IV.

Here’s SA-9’s S-IV stage with said contours.

S-IV Second_Stage_for_SA-9
These workers aren’t working. They’re on their lunch break: Sacrificing their corned beef for touching, gazing, and admiring the majesty of the S-IV. (NASA)

It’s sad that the S-IV saw little operation. Aside from SA-5 and launching a few boilerplate Apollo Command Modules, the last three launched the Pegasus micrometeroid sensing satellites.

The S-IV did demonstrate the reliability of cryogenic engines for later Saturns, thanks in no small part to the RL-10 and its prior test flights with the Centaur upper stage.

Pegasus 9801797-orig
The Pegasus component extended out from a modified Service Module casing on the S-IV. (NASA)

To complete this examination of unadulterated hawt rocket exhaust, just enjoy this video, which gives you a healthy dose of the S-IV’s design, transport and assembly in the process of the launching of SA-5.

I’ll be in my bunker.

Sources: