Clustering

[KASASpace]

In the late 1950s, Wernher von Braun helped to design the "Saturn" rocket, not the C-series, the A-1 version.

It was effectively a Jupiter stage surrounded by Redstones with a cluster of 8 H-1s.

They originally wanted E-1s, but using the H-1s, which were only slightly different from the Jupiter's own engines, it would take much less time.

So, there are two different clustering things:

Clustering Engines,

and clustering fuel tanks on a stage.

Now, are there any particular advantages that make these kinds of rockets?

If so, what are they?

I know it makes it cheaper if you use components already being built, for example the Redstone tanks, but what about the other aspects?

[R0cketC0der]

One major aspect in clustering is safety. If you have only one engine and it fails, the launch is a complete failure. If you however have multiple engine and one fails, you may be able to continue the flight.

[KASASpace]

One major aspect in clustering is safety. If you have only one engine and it fails, the launch is a complete failure. If you however have multiple engine and one fails, you may be able to continue the flight.

Yet, those engines also have separate subsystems, such as their own turbopumps and gimbals.

So, paradoxically it's less efficient, but more "reliable" in that way.

[Nibb31]

The reason for using clustering for the Saturn 1B first stage was simply because Jupiter and Redstone tanks were available. It was a quick kludge that carried a serious mass penalty, but it did the job.

Sometimes the best tool for the job is the one that you have rather than the one you need to build from scratch.

[KASASpace]

The reason for using clustering for the Saturn 1B first stage was simply because Jupiter and Redstone tanks were available. It was a quick kludge that carried a serious mass penalty, but it did the job.

Sometimes the best tool for the job is the one that you have rather than the one you need to build from scratch.

I'm not asking why, I'm asking advantages.

[Rakaydos]

I'm not asking why, I'm asking advantages.

"Bird in the hand" is an advantage.

[KASASpace]

"Bird in the hand" is an advantage.

Yes, yes it is.

Although I had to look that up to understand it, as I've never heard that proverb before.

[Rakaydos]

Looking things up is good.

[Idobox]

There is also an advantage in industrial process.

If you use few big engines, you basically run a workshop, and build them like prototypes. But if you use many smaller engines, you can use processes closer to mass production and cut the costs.

For example, imagine you need a mould for one part. If you have a big engine, it will be a big part, the mould will be very expensive (doesn't scale linearly with size), you will need advanced techniques to keep the metal liquid everywhere and avoid issues with thermal contraction (when the metal cools, it shrinks).

But if you use a cluster of smaller engines, the mould will be smaller, hence cheaper and easier to use, and you will use it much more often. So you end up with lower capital cost spread over more stuff (the smae engine can be used alone for a secondary stage, clustered for the primary one, clustered differently on booster, etc).

The same kind of scale economies will be found pretty much everywhere in the process, resulting in significantly cheaper stuff.

You also save on R&D. If you have a small engine, it's usually cheaper to cluster a bunch of them rather than to develop and test a new one.

The fact that big engines exist means there are advantages to single engines too. I assume better performances, and less balancing issues, as well as tailoring to the needs (if you need 3.5 times more thrust, it might be better to build a new engine rather than cluster 4 small ones).

[Nibb31]

I'm not asking why, I'm asking advantages.

The advantage of a tank that is available is that it is available. You have the tooling and the industrial process in place to build more.

Having to design a new tank from scratch is a disadvantage.

[KASASpace]

The advantage of a tank that is available is that it is available. You have the tooling and the industrial process in place to build more.

Having to design a new tank from scratch is a disadvantage.

Let me put it this way:

I'm not asking why they did it on the Saturn 1, I'm asking for any particular advantages (or disadvantages) of this construction technique.

It also allows for better modularization. As in the Saturn 1, eight "Redstone" tanks were used, and that means no new huge tank as Redstones were already in production, and plus it was also how they all were simply "put in place" around the Jupiter, which is fairly easy, but it required a lot of equipment.

[cantab]

Ultimately that is one of the primary advantages: Being able to use the same components in different complete machines. It saves development costs, and thus money. We see this pretty much everywhere, not just in rocketry.

[Brotoro]

It can also help with transportation. The Proton rocket is built with a large central oxidizer tank, and its side-tanks hold the fuel and have the engines mounted on them. The reason for this was because the diameter of the oxidizer tank (a little over four meters) was the largest the Russians could transport by rail. So the side tanks/engines are strapped on at the launch complex to make a larger first stage than could be transported across country.