Twin Asparagus - You're going to go even further, kid!

[Xyphos]

Okay, so you may be aware of Asparagus fuel routing:

Aux-->Aux-->Aux-->Main<--Aux<--Aux<--Aux

and I've been using the above method for quite a while now, it's the "traditional" asparagus method, butI've discovered an even better method (I think)

Aux-->\                      /<--Aux
      |                      |
      +-->Aux-->Main<--Aux<--+
      |                      |
Aux-->/                      \<--Aux

In comparison between the two, the traditional method often stages at 2500m, 7500m, 25000m depending on payload,

but twin aparagus stages at 12000m, 35000m, and the last stage at some point during or after circulation.

another advantage of using the twin method is, it reduces the total stage count by 1, and jettisons 4 tanks (dead weight) on the first stage allowing the rocket to go further with just 2 aux tanks left attached.

try it out and let me know what you think.

Edited May 14, 2015 by Xyphos

[Reddeyfish]

Once the outer 4 aux tanks are at 50%, wouldn't it be more efficient to transfer all the fuel from 2 of the outer aux tanks to the other two outer aux tanks, then stage the empty tanks? You wouldn't need to bring those tanks any further, gaining some delta v and efficiency.

(unless there are engines on those tanks, maybe)

Edited May 14, 2015 by Reddeyfish

[Xyphos]

Once the outer 4 aux tanks are at 50%, wouldn't it be more efficient to transfer all the fuel from 2 of the outer aux tanks to the other two outer aux tanks, then stage the empty tanks? You wouldn't need to bring those tanks any further, gaining some delta v and efficiency.

fuel ducts, terminal velocity.

[Grumman]

another advantage of using the twin method is, it reduces the total stage count by 1, and jettisons 4 tanks (dead weight) on the first stage allowing the rocket to go further with just 2 aux tanks left attached.

I don't see how that is true. You are not jettisoning any tanks until four are empty, instead of the usual two, so you're actually jettisoning dead weight later than you normally would. This:

Aux-->\                      /<--Aux
      |                      |
      +-1>Aux-2>Main<2-Aux<1-+
      |                      |
Aux-->/                      \<--Aux

...is functionally identical to this:

Aux-->Aux-1>Aux-2>Main<2-Aux<1-Aux<--Aux

...which is the same as traditional asparagus staging if you never jettison the first pair of tanks until the second pair is also empty.

If there is an advantage here, it is because your standard asparagus staging had the first two engines running out of fuel and being jettisoned earlier than they should have been.

[Norcalplanner]

What you're describing is a hybrid between onion staging and asparagus staging. Sometimes onion is helpful to keep a higher TWR for a longer period of time in the first stage - I tend to use a further modified onion method for that very purpose on extremely large rockets, with a core, an inner ring of six stacks that all stage at the same time, and an outer ring of twelve stacks (two feeding into each inner ring stack). Here's an example (from 0.90 aero days) that takes this to an extreme -

Javascript is disabled. View full album

[Xyphos]

What you're describing is a hybrid between onion staging and asparagus staging.

I never heard of onion staging... I'll have to google it.

also, if this isn't any better than traditional then please ignore my ignorance.

[CalculusWarrior]

I never heard of onion staging... I'll have to google it.

also, if this isn't any better than traditional then please ignore my ignorance.

Onion staging is simply where the outer boosters all transfer fuel to the central tank at the same time, as opposed to asparagus where only two at a time do so. So named because its like cutting an onion when the boosters separate you forgot to attach sepatrons, and so you cry as your rocket explodes.

[Xyphos]

Onion staging is simply where the outer boosters all transfer fuel to the central tank at the same time, as opposed to asparagus where only two at a time do so. So named because its like cutting an onion when the boosters separate you forgot to attach sepatrons, and so you cry as your rocket explodes.

...so basically onion is essentially a larger, linear version of asparagus; eg, instead of "going around full circle" the fuel is routed from outter to inner, but each "leaf" going to the main engine. gotcha...

[martinborgen]

Yes. The advantage is that you mantain a higher TWR compared to an asparagus.

[sgt_flyer]

Heh used almost the same thing with my Chaos star (both for the 1000t payload version 0.90 and the 1500t mk2 version

Though, it was using 8x symmetry for the inner ring (which fed the core), and 'twin' x8 boosters for the outer ring (each of the 8 twin boosters fed 1 of the inner ring boosters). With the new aero, it helps maintaining high twr before reaching 10000m - also, using an hybrid onion staging helps a lot with upper stage stability, when dealing with such heavy payloads (not sure it would be as stable if i was discarding only a part of the boosters earlier)

[Superfluous J]

I've done before what others suggest you do instead, and used drop tanks in my first stage to drop. The idea is to have enough TWR to launch, and then when your outer tanks are empty (the outer aux in your first diagram, that don't have engines on them) I drop them, lose mass, but lose no thrust.

I don't use it anymore, because it goes counter to what seems to me to be the best launch profile: Keep TWR from going too high in the lower atmosphere. Dropping mass but keeping all your thrust (or in your case keeping all your thrust longer than asparagus would) just gives you more TWR low in the atmosphere. Which - for me at least - means spinning craft at best, and scrubbed missions (and open slots in the roster) at worst.

[martinborgen]

Dropping only tanks with no engines on the first stage of an asparagus is something I tended to do too - as the outermost tanks get drained very quickly on a big setup - so your TWR is going to be enough to lift those without engines on them because after the first 12 seconds or so your rocket would have to make do without them anyways.

[rkman]

I've discovered an even better method (I think)

fuel ducts, terminal velocity.

So it is "better" not in terms of fuel use/delta-v

[NecroBones]

Just adding ye-olde diagram to the discussion: (the upper right diagram is the one that we call "Onion")

Edited May 14, 2015 by NecroBones

[mikegarrison]

Drop tanks usually don't make a lot of sense compared to having an engine to help lift the weight of the fuel in those tanks, but it all depends on your thrust needs. Whether "onion" or "asparagus", the advantage is that all of your engines are thrusting rather than being carried as dead weight.

What you need to know to design the most efficient lift is the payload you and to take into orbit. From there you want to try to balance your thrust and your delta-v. Too many engines (or too powerful) and you have a wasteful amount of thrust. But too few engines at any stage and you waste delta-v because instead of accelerating your rocket you are only just burning fuel to avoid falling back down again.

So depending on the payload and the engines you have available to you, any of these can be right.

[Ival70]

Just to make things complicated, I use asparagus x3 staging. (great for when you want the efficiency of asparagus, combined with the higher TWR of onion staging).

So instead of:

S4>>S3>>S2>MAIN

S4>>S3>>S2>MAIN

You have:

S3>>S2>>MAIN

S3>>S2>>MAIN

S3>>S2>>MAIN

You can also do any other level of symmetry with asparagus.

x4, x5, x42, even x1. But let's not get started on bamboo staging.. (also Stages 1/2).

[martinborgen]

Just to make things complicated, I use asparagus x3 staging. (great for when you want the efficiency of asparagus, combined with the higher TWR of onion staging).

So instead of:

S4>>S3>>S2>MAIN

S4>>S3>>S2>MAIN

You have:

S3>>S2>>MAIN

S3>>S2>>MAIN

S3>>S2>>MAIN

You can also do any other level of symmetry with asparagus.

x4, x5, x42, even x1. But let's not get started on bamboo staging.. (also Stages 1/2).

Yeah, I often do an asparagus where you drop outer boosters one by one, but the core is a bundle of three, five or even seven, to maintain positive TWR...

I also arrived at the sollution refered to as bamboo-staging before the term was coined, like many others I'm sure, but I found that for the first booster, it's ....e to pendulum-fallacy. For my first mun landers, I use it often, as the landers have plenty of thrust, so I just stick a tank beneath it.

[Idrryl]

Interesting... I haven't used asparagus in quite a while (FAR kinda beats that out of you ) but I might give it a shot now.

[luizopiloto]

I use this method of aspargus since 2013 kid... you don't even know the things I did at Eve using this...

[LostOblivion]

You can get to the Mun, land, and return with only ~5000 funds by using bamboo staging. :-)

[martinborgen]

You can get to the Mun, land, and return with only ~5000 funds by using bamboo staging. :-)

Interesting. I'm more into overbuilding things, and I reckon even a single engine is going to cost 20% of that. Fuel is also expensive? picture?

[Xyphos]

You can get to the Mun, land, and return with only ~5000 funds by using bamboo staging. :-)

bamboo?

[Ival70]

bamboo?

Bamboo staging is a type of staging in which the engines are attached radially, and tanks are dropped off from a central stack as their fuel is drained. Most commonly, there are only engines on the top stage, though they can be added to other stages as well.

For example:

https://imgflip.com/gif/lir3z

The gif didn't turn out so well.. here is the video if you don't feel like squinting: (Can't figure out how to have it start at the right place, so skip to 22 seconds)

There was a great Imgur album that showed bamboo staging, but I can't find it.

[Bill Phil]

It's better to get rid of dead weight faster. I don't see a big advantage in this...

This only doubles the propellant in the first Aux tank, really. Which then pumps into the second and finally into the core.

[xtoro]

I've done this a few times just to get extra thrust to a higher orbit, as mentioned earlier, but I don't really find it necessary anymore. With simple asparagus of only 4 engines around the main center tank in 2 stages, it's more than enough for most heavy loads. For more I just add 4 SRB's so I can run at 1/3 throttle until they burn out, which leaves me with more dv higher up. This allows me to lift 85t into LKO.

To lift very large ships, I just make sure their tanks are almost empty and refuel in orbit.