Staging Methods Overview

[mhoram]

Based on this thread I thought it might be interesting to have a description of the different staging methods.

Corrections and additions welcome.

There are two classes of staging methods: serial staging and parallel staging

Serial staging

Serial staging is the classic way of staging.

Each engine burns only during a single stage and is dropped after the fuel of this stage has run out.

Pro: Allows a lean design for decreased drag in real life (has no physical relevance in KSP 0.23.5). No fuel routing required.

Con: Engines are not put to best usage

Parallel staging

Parallel staging allows engines of different stages to burn at the same time.

In most cases all engines are started at the begin of liftoff.

Fuel routing between stages is optional.

Pro: More efficient than serial staging.

Con: Large shear forces at the end of stages. Fuel routing needs to be set up.

There are two widely used subforms of parallel staging with fuel lines between stages: Asparagus and Onion staging.

In some cases solid fuel boosters are used to help with the ascent.

Asparagus staging

A 2-times symmetry is used for dropping tanks.

Fuel is only drawn from the outermost stages, that are ejected next.

This method allows a fast dropping of unneded fuel tank hulls and engines while still maintaining a symmetrical rocket.

Someone researched the  origins of the name  (forum post no longer available) (see here or here).

Wiki Page

Onion staging

In onion staging rocket the stages are dropped like an onion in circular layers.

Fuel is only drawn from the outermost stages, that are ejected next.

While it is less efficient than asparagus staging because unused fueltanks are dropped later, it is more easily set up.

Side booster staging

I could not find a name for this method - any suggestions?.

It adds the advantage of serial staging (no fuel ducts).

The stages can be set up for a specific TWR-profile.

Here is an example.

Rarer used staging methods

Drop tank / Slack tank / Breadcrumb staging

This method is used if a decrease in TWR in later stages is not needed.

Origin of the name Breadcrumb

Bamboo / Train staging

It is a subform of drop tank staging where the droptanks are in the axis of the ship.

It is also similar to twisted candle staging where the engines are only placed at the last stage.

Origin of the name Bamboo

Origin of the name Train

Pancake staging

It is a subform of serial staging where each stage has multiple engines. (Original video is no longer publicly available)

Twisted Candle staging

A staging method that is more efficient than asparagus staging, since tanks are dropped at twice the rate than in asparagus staging.

The setup is however even more complicated because one has to consider placement of engines.

Origin of the name Twisted Candle.

Edited September 5, 2022 by mhoram
updated links

[Red Iron Crown]

Nice tutorial. I've heard Bamboo staging called "Breadcrumb" or "Train" staging, too, might want to add that.

[mhoram]

@Red Iron Crown: thanks for the hints - never heared these names before. But I think Breadcrumb is not the same as Train and Bamboo.

[Red Iron Crown]

Ah, I had thought of breadcrumb as dropping one tank at a time, thanks for the clarification/correction.

[Pecan]

Hmmm, I don't know how comprehensive/abstruse you want to make this :- 'overview' as in the title or 'reference dictionary'. This is my take on things (which may be completely wrong, so I'm glad you're putting this together!)

Classic "Serial" (aka "Stack") staging, fine although "Con: Engines are not put to best usage" is probably not accurate. One of the advantages being that you can use lighter engines on higher stages but the big disadvantage being that you have to carry them around until their one brief "moment of f(l)ame".

The train and twisted candle strategies you show when you add fuel lines to serial staging are fine (and I must use them more!). Note that you can mix those two so only 'some' of the twisted candle stages have extra engines, just when the TWR is getting low and needs a bit more thrust. Also, the engines don't have to be the same on every stage so you can add light engines for 'a bit' more thrust or heavy engines for a lot.

"Radial" staging I usually use to describe 'side booster' staging where outer boosters fire first, then inner ones, then up the stack (if present). No fuel lines, as you say, but specifically not having all engines firing at once, which I leave for ...

"Parallel" staging - without fuel lines. Inner engines will have to be more fuel-efficient or have more fuel in their stacks in order to keep buring longer.

Once you add fuel lines to parallel you have "asparagus" at symmetry 2 or "onion" at 3+. Again, you can put lighter or heavier engines on different stages according to TWR need.

Drop tanks in twisted candle/onion/asparagus (doesn't make sense in serial, radial or parallel, already there in train) are also known as 'slack tanks' and, just as mentioned above for twisted candle, mean you can have extra fuel for inner stages that already have enough thrust and only need the extra mass of more engines on stages where the TWR is getting low.

Edited April 9, 2014 by Pecan

[John FX]

Ah, I had thought of breadcrumb as dropping one tank at a time, thanks for the clarification/correction.

I think of it as breadcrumb staging also.

[michaelhester07]

Asparagus staging works with the new liquid fuel boosters. It's a technique to consider for launching those huge rockets for asteroid captures.

[mhoram]

Hmmm, I don't know how comprehensive/abstruse you want to make this :- 'overview' as in the title or 'reference dictionary'. This is my take on things (which may be completely wrong, so I'm glad you're putting this together!)

I wanted to make it more comprehensive and think that overview fits more.

Classic "Serial" (aka "Stack") staging, fine although "Con: Engines are not put to best usage" is probably not accurate. One of the advantages being that you can use lighter engines on higher stages but the big disadvantage being that you have to carry them around until their one brief "moment of f(l)ame".

And that is exactly the reason why I think that they are not used in the best way possible (main diffrence to Asparagus staging).

The train and twisted candle strategies you show when you add fuel lines to serial staging are fine (and I must use them more!). Note that you can mix those two so only 'some' of the twisted candle stages have extra engines, just when the TWR is getting low and needs a bit more thrust.

I do not want to include mixed staging strategies, as this would complicate this whole tutorial: there are so many different possibilities.

Also, the engines don't have to be the same on every stage so you can add light engines for 'a bit' more thrust or heavy engines for a lot.

Agreed, but for the simplicity of this overview I keep the pictures as simple as possible.

"Radial" staging I usually use to describe 'side booster' staging where outer boosters fire first, then inner ones, then up the stack (if present).

Timing of starting engines is a concept that I do not want to include for simplicity reasons, but this sounds a bit like serial staging with a horizontal build form.

No fuel lines, as you say, but specifically not having all engines firing at once, which I leave for ...

"Parallel" staging - without fuel lines. Inner engines will have to be more fuel-efficient or have more fuel in their stacks in order to keep buring longer.

Once you add fuel lines to parallel you have "asparagus" at symmetry 2 or "onion" at 3+. Again, you can put lighter or heavier engines on different stages according to TWR need.

After thinking for a while about this, it makes sense, to distinguish serial and parallel staging by the question "Do engines from different stages burn at the same time?" and leave the fuel routing out of the question. Will update the pictures accordingly.

Drop tanks in twisted candle/onion/asparagus (doesn't make sense in serial, radial or parallel, already there in train) are also known as 'slack tanks' and, just as mentioned above for twisted candle, mean you can have extra fuel for inner stages that already have enough thrust and only need the extra mass of more engines on stages where the TWR is getting low.

Thanks for the info about slack tanks ... will add it.

I think of it as breadcrumb staging also.

According to the original post where Breadcrum staging was mentioned, mutiple tanks were dropped ad the same time.

So I think that it makes sense to call drop tank stages "Breadcrumb staging" no matter if only a single or multiple tanks are dropped at the same time. And Bamboo/Train staging is just a subcategory of this.

Edited April 20, 2014 by mhoram

[Pecan]

Nice job again mhoram. Glad to have added anything and very glad that it's you sorting out arguments, not me!

[Comwarrior]

What about things like asparagus with tri-simetry?

Whats about serial and parallel asparagus staging?

and then theirs Zistu staging...

[Red Iron Crown]

Tri-symmetry asparagus is a subset of onion staging. Not familiar with Zistu, what is it?

[mhoram]

What about things like asparagus with tri-simetry?

Whats about serial and parallel asparagus staging?

and then theirs Zistu staging...

1) Onion Staging is a superset of tri-symmetry.

2) I did not want to mix the staging methods for simplicity of this overview.

3) A quick search for Zistu staging was not successful. Du you have a link with a description of that method?

[Pecan]

Ninja'd

Edit: mhoram - you rock!

(asparagus symmetry-3 is really just a mistake in understanding as far as I can tell - but parallel asparagus? He's having a laugh.)

Edited May 16, 2014 by Pecan

[Red Iron Crown]

Serial asparagus: One asparagus on top of another.

Edit: Moar boosters!

Edited May 16, 2014 by Red Iron Crown

[Pecan]

Well, sort of - except it isn't asparagus if the upper rockets aren't firing and it isn't serial if they are. I'm assuming that as lower pairs are dropped the upper engines, now clear, start to burn and take their fuel from the remaining lower tanks? But's that's just asparagus not done properly - you have to push useless engine-mass until it is cleared to contribute. The physical arrangement doesn't affect the logical fuel-flow, just delay (and impede) it.

(Sorry, I'm just back from the pub as I type this) - what I mean is, you could do the same thing more efficiently but less aerodynamically by combining the upper stages with the 'real' asparagus lower ones.

[Red Iron Crown]

It was mostly an experiment in making a high dV asparagus arrangement somewhat aerodynamic. The 2.5m lower asparagus works alone, the upper works as you describe, with upper engines igniting as lowers are dropped. It's not pure asparagus, nor is it pure serial, more of a hybrid of the two.

[Pecan]

I have used the same arrangement in a couple of launches where the payload engines are LV-Ns. They don't provide much thrust but what they do give is cheap - better to have it working than waiting, so arrange launch-vehicle stages so that the payload engines are clear, and can contribute, as soon as possible. (We know what we're talking about anyway. It'll be interesting to see if this 'Zistu staging' is something new).

[Red Iron Crown]

It'll be interesting to see if this 'Zistu staging' is something new).

I think it's actually Zisteau, and maybe it's referring to what's shown in

(Skip to around 4:35 for the interesting rocket). Looks like an asparagus rocket sitting on top of a bunch of solid boosters, with another bunch of SRBs mounted radially. I could be wrong, maybe he's got something more innovative in the other 80 or so videos, but it looks like he used the same technique for his Eve ascent vehicle.

I'm not a fan of SRBs in general, I feel they're outperformed by liquid engines in almost every scenario, but maybe that will change if they're significantly cheaper when money is a concern.

[Iansoreta]

It was mostly an experiment in making a high dV asparagus arrangement somewhat aerodynamic. The 2.5m lower asparagus works alone, the upper works as you describe, with upper engines igniting as lowers are dropped. It's not pure asparagus, nor is it pure serial, more of a hybrid of the two.

I resort to that staging technique only when huge amount of delta v is required. For instance, Tylo and eve are the hard to fly planet and moon cause of high delta v requirement. Another advantage to that is it increases twr and efficiency progressively while keeping aerodynamic profile low, meaning the upper stage engine and lower stage engine are both active at the same time, only the lower stage feeds the upper stage(in other word, the upper stage engine is consuming fuel from lower stage while the lower stage engine is active).

[Dispatcher]

I have made several craft which rely on various staging methods and I've used most of the ones discussed above (including staging of tanks).  I understand why onion staging is so called.  I propose that we redesignate "asparagus staging" as "celery staging" due to the celery stalks peeling off the central base.  

On May 17, 2014 at 5:46 PM, Red Iron Crown said:

I think it's actually Zisteau, and maybe it's referring to what's shown in

(Skip to around 4:35 for the interesting rocket). Looks like an asparagus rocket sitting on top of a bunch of solid boosters, with another bunch of SRBs mounted radially. I could be wrong, maybe he's got something more innovative in the other 80 or so videos, but it looks like he used the same technique for his Eve ascent vehicle.

I'm not a fan of SRBs in general, I feel they're outperformed by liquid engines in almost every scenario, but maybe that will change if they're significantly cheaper when money is a concern.

Is this the correct video?  I'm not seeing any multiple engine rocket here.

[Red Iron Crown]

6 hours ago, Dispatcher said:

Is this the correct video?  I'm not seeing any multiple engine rocket here.

It is not, the embed must have gotten messed up in the forum migration. Forgive me, but I don't have the patience to trawl though a hundred videos to find the right one.

[mhoram]

22 hours ago, Dispatcher said:

I propose that we redesignate "asparagus staging" as "celery staging" due to the celery stalks peeling off the central base.

Dont know ... asparagus staging is an already widely used phrase for this kind of staging. Rebranding it in this thread will probably not change its usage and might confuse others who read this.

[Dispatcher]

10 hours ago, mhoram said:

Dont know ... asparagus staging is an already widely used phrase for this kind of staging. Rebranding it in this thread will probably not change its usage and might confuse others who read this.

I just knew I should have added the smiley emoticon.  

[wumpus]

One note: while classic bamboo staging is unstable (it follows the pendulum fallacy), I've had a lot of success using it (only stacking the extra tank or two on top of the capsule) for early missions to Mun and/or Minmus.  Once you have upgraded the buildings enough for EVAs (which you want before landing on a moon, probably before orbiting), you can stack fuel tanks on top of the capsule and manually move the fuel to the bottom, and then jettison the fuel tank.  Obviously, this is typically only done for staging beyond the atmosphere (where you can turn and stage away from yourself), but can make for a much more efficient top stage (and not require a second decoupler or fuel lines).

I'd also recommend following a "nautilus staging" method.  Typically, asparagus stages are nearly all the same, while when using serial staging it is more obvious to use stages at least geometrically larger than the later (top) stages.  There really isn't a reason not to do this in parallel staging, and strongly recommend it.  I also think "breadcrumb" staging is underutilized (probably because they are just called "drop tanks"), but as KSP has kept adding stronger and stronger engines (which tend to work better than asparagus staging), it makes more sense to have drop tanks that are nearly as large as the rocket itself.

In practice, there are also differences in how onion staging punches through at atmosphere vs. asparagus (while rare, sometimes an increasing  TWR is an advantage).  Still, you can typically create a more efficient system by combining breadcrumb and asparagus stagining (you always could before 1.0 enforced even semi-real aerodynamics on you.  Attaching the power of multiple engines on a single stage in versions >=1.0.0 is an exercise for the reader).   An example is replacing eight terrier boosters in an onion configuration would be nearly equal to two asparagused staged terrier engines.  Should you spread out the fuel tanks by using "breadcrumb" staging (with 2 stages aspargused, and 6 stages as breadcrumbs to the asparagus stages) you should always be more efficient than the original 8 onion stages once the first two drop (and have a TWR slighly higher than the onion, something that a normal asparagus won't match).

 

[Pecan]

Agreed - I see asparagus more about the fuel-flow allowing opposite pairs of stacks to be jettisoned at the same time than about equal stages.  As you point out it's not really a very necessary or useful art any more but when I do/did use it I am happy to tune each stage for its section of flight, especially through atmosphere.