Asparagus Staging: an Explanation

[Vanamonde]

Say you've built this rocket, but it doesn't go as far as you need it to.

So you add some side tanks to give it more fuel and longer range.

(Note that this requires running the little yellow fuel lines from the outer tanks to the inner, and yes, the direction is important because fuel runs from the first attachment point to the second. If you ever get confused about which way the fuel lines run, zoom way in and you'll see little gray triangles on the lines, pointing the way the fuel will flow.)

But now, the rocket is too heavy for the engine. What to do? Give the side tanks engines to lift their own weight.

The side columns will now support their own weight, while still providing additional fuel for the original rocket in the center. True, adding more engines means that they burn some of the fuel, and not all of the fuel in the side tanks is now available for use by the central engine. But this arrangement is still a net gain for the ship as a whole, and the rocket will go farther with these side tanks than without them. This is what is described as asparagus staging, because apparently somebody once thought the cluster of side columns made the rocket look like a clump of asparagus spears. Anyway, when side columns are both burning engines of their own as well as pumping fuel to central stages, that is asparagus staging.

Asparagus staging is not used much in the real world for two reasons. Firstly, pumping fuel at the required rate is quite difficult, and creates a number of technical difficulties. And secondly, the side tanks add to air resistence, slowing the rocket and holding it back. But within the game, fuel is pumped as fast as you want it to move, and the additional drag from the side tanks is not a serious problem. 

Now that we've described asparagus staging, let's demonstrate how it works.

For this example, I have added an additional set of asparagus columns, to better demonstrate the idea.

The ship takes off and all engines are contributing to lifting the ship's mass.

But once the outer set of tanks have used their fuel, they become useless weight which holds the ship back. You want to eject the tanks, but an additional benefit of asparagus staging is that the engines on the outer columns are no longer needed, and can be discarded along with the tanks.

Keeping those engines would make the ship go faster, but that isn't always a good thing. Excessive acceleration wastes fuel in atmosphere by trying to push the ship faster than air resistence will allow it to go, and extreme acceleration can even cause parts of the ship to collapse. So off the engines go with the tanks. But keep in mind that the fuel tanks on the remaining portion of the ship are still entirely full, since the fuel they've burned has been replaced by fuel pumped in from the outer tanks.

Repeat the process with the second stage and you are back to your original rocket,

except that compared to launching it directly from the pad, it is now "launching" with an advantage of many meters of altitude and many meters/second of speed, but still has full fuel tanks.

I laid out that example rocket with the columns side-by-side so that it would be easy to see the design, but it actually isn't very strong. That's why players generally wrap the asparagus stages around the central column. (This version has exactly the same parts as the version above.)

In this arrangement, all of the side columns cluster around the central core, which makes the ship stronger, and has the advantage of giving you attachment points for reinforcement struts. But this rocket will function just like the flat version pictured above, as long as the fuel lines are arranged properly to feed from outer tanks to inner.

Once you have arranged the parts the way you want them in the VAB, though, be careful to go back and re-work the staging order, as the game's construction system does not automatically arrange the parts in the order you need. All the engines should fire at once, then the first set of decouplers should fire, then the second. The staging display should look like this when properly arranged.

So that's what asparagus staging is, how it works, and how to build it, so that your rockets fly farther and are stronger. I hope this has been helpful.

[EtherDragon]

That's a nice tutorial!

I have a video you should check out where I go over the mathematics of why asparagus staging works as well as it does. It doesn't demonstrate staging as well as you did, but it goes into detail about how/why the math ends up working in your favor when you use asparagus staging.

Check it out:

[arcanise]

covered this in one of my many tutorial videos

[TheGreatB3]

Actually, there's a really great mod called SmartStage that will reorder the stages for you, and works especially well on asparagus staging. I've also found a mod called AutoAsparagus, but I haven't tried it yet. It should be fully compatable with SmartStage though.