Asparagus staging overrated?

[Red Iron Crown]

Well done for being very precise, and also rather confusing. Nonetheless, for people who want to understand the basics of asparagus staging, what I said is accurate enough.

Not really, what you said isn't accurate at all; it creates confusion rather than reducing it. The direction in which the tanks and engines are dropped is not important to what asparagus staging is or how it works.

[Pecan]

OK so here is my Mun orbiter craft. Total cost 11,585.5 payload mass 2T...

Thanks John, I shall play more with SRB-based designs.

(Real life has caught-up with me again. Busy)

.

[OhioBob]

Really, is there an alternative to Asparagus when it comes to lift something from Eve's sea level to orbit? Provided you have to land this thing first.

It is clear from the OP that I wasn't talking about Eve. The overwhelming majority of anyone's launch cost is going to come in getting off of Kerbin. It is launching from Kerbin surface to low orbit where cost efficiency is a primary driver, and it is this that is the context of the discussion. Launching from Eve is a special case that requires a rebalancing of priorities. In the Eve scenario mass efficiency becomes much more important than cost efficiency.

Edited November 13, 2014 by OhioBob

[The_Rocketeer]

Not really, what you said isn't accurate at all; it creates confusion rather than reducing it. The direction in which the tanks and engines are dropped is not important to what asparagus staging is or how it works.

I'd be interested to see an asparagus staging design that doesn't drop empty tanks from the outside of the rocket.

[OhioBob]

I just changed this thread from "Unanswered" to "Answered". I think we've had some pretty good discussion. It seems that, for the most part, people agree that asparagus staging is not the most cost effective method for reaching Kerbin orbit. Of course cost has only recently become a important consideration, and then only in career mode. Everyone seems also to agree that asparagus staging is one of the most mass efficient configurations. When cost is not a factor, such as in sandbox mode, or in some special cases, such as launching from Eve, asparagus staging is still one of the best ways to go.

[Jouni]

Really, is there an alternative to Asparagus when it comes to lift something from Eve's sea level to orbit? Provided you have to land this thing first.

Eve landers are just a bit bigger without asparagus staging. As a quick estimate, a 200-tonne lander should be able to lift 1 tonne of payload by using two Mainsails in the first stage, a Skipper in the second stage, an LV-T30 engine in the third stage, and two 48-7S engines in the fourth stage.

I'd be interested to see an asparagus staging design that doesn't drop empty tanks from the outside of the rocket.

Take your generic asparagus-staged rocket, use cubic octagonal struts and fuel lines to attach booster engines radially, arrange the boosters vertically in two stacks, and drop the boosters from top to bottom, using sepratrons when needed.

The point was, however, that while asparagus-staged rockets usually drop spent stages from sides, not all rockets dropping fuel tanks (or spent stages or even spent stages with fuel crossfeeding) from sides use asparagus staging.

[deepspacecreeper]

I kinda played with SRBs after accepting a suggestion of "using SRBs instead of asparagus" because "it was cheaper".

I tested that myself. I slapped 8 Kerbodyne SRBs (0.23.5) onto a liquid core, and also did an asparagus config without the SRBs. Currently I tested 2 payload ranges. Results were:

(Payload/With SRB cost/Asparagus cost)

30/50000/90000

60/157000/180000

From this experiment i conclude: SRBs save you a lot of money.

But I thought of the reliability of SRBs, especially when decoupled. There is a bug which will cause the boosters to crash back on the liquid core, even with seperatrons. Asparagus staging helps you keep the rocket small and structural issues minimal, and you dont have to slap 8x2=16 SRBs on a single 3.75m core stage. But it is more expensive compared to a SRB+LF rocket.

Im sorry about the wrong values that I entered (anyone noticed?), but it should be fixed now, and the values above is now right.

[The_Rocketeer]

Take your generic asparagus-staged rocket, use cubic octagonal struts and fuel lines to attach booster engines radially, arrange the boosters vertically in two stacks, and drop the boosters from top to bottom, using sepratrons when needed.

The point was, however, that while asparagus-staged rockets usually drop spent stages from sides, not all rockets dropping fuel tanks (or spent stages or even spent stages with fuel crossfeeding) from sides use asparagus staging.

I may have misunderstood your design description, but that does rather sound like the tanks are being jettisoned from beside the centre stack.

Since the term 'asparagus' is used to describe the arrangement of parts being being dropped, whether or not they include an engine component they are still asparagus. I would accept an argument that said that they were not 'stages' unless they included such a component, but that doesn't seem to be the distinction that is being made. Any arrangement that sequentially sheds parts in a radial configuration uses an asparagus arrangement to shed them. If they happen to be or include thrust-generating parts, then it can be correctly deemed 'asparagus staging'.

[OhioBob]

(anyone noticed?)

Yes, I did. I just figured it was a typo.

[Red Iron Crown]

I'd be interested to see an asparagus staging design that doesn't drop empty tanks from the outside of the rocket.

I whipped up a quick example of a non-radial asparagus arrangement for you:

It is true that this is not a typical arrangement, it is far more common to have the asparagus pairs attached radially. But the important thing is that it is not the physical arrangement of the pairs that makes it asparagus, it is instead the logical arrangement of fuel flow and staging.

For something to be asparagus staged, it must meet the following criteria (and only these criteria):

1. All engines must fire simultaneously.

2. All engines must draw fuel from the lowest tanks in the staging order.

3. Tank/engine assemblies must be staged in pairs.

The problem with your earlier statement "Asparagus staging means empty tanks fall off the side." is that there are many non-asparagus arrangements that have empty tanks fall off the sides, like onion staging or radial boosters that aren't crossfed. The statement reduces one's understanding of asparagus.

[The_Rocketeer]

We have a fundamental disagreement about what "asparagus staging" means. Your design is an example of bamboo shedding, not asparagus.

I won't argue anymore cos frankly I cba, but I don't accept your assertions.

Asparagus staging doesn't need to fire all engines simultaneously, although it can.

Not all engines need to draw from the furthest tanks.

Assemblies do not need to be paired.

[Jouni]

We have a fundamental disagreement about what "asparagus staging" means. Your design is an example of bamboo shedding, not asparagus.

There is no fundamental disagreement here. You are using established terminology in a non-standard way.

The term 'asparagus staging' is specific to the KSP community, even though there are some obscure real-world connections. It's a poor name for a concept, because if you don't know what asparagus staging means, hearing the term doesn't really help. There is only one valid excuse for using such opaque terminology: as codewords for complex but useful concepts that don't have simple definitions. If the concept is already familiar to you, hearing the term gives you a fairly precise idea what the other person is talking about.

'Asparagus staging' is a useful codeword for "multiple layers of boosters with fuel crossfeeding, with two boosters on each layer", because it's a well-known narrowly defined relatively useful design pattern. Using it to refer to radially attached drop tanks and boosters in arbitrary crossfeed configurations would be a bad idea, because it doesn't tell anything you couldn't describe with simple transparent terms.

[Red Iron Crown]

We have a fundamental disagreement about what "asparagus staging" means. Your design is an example of bamboo shedding, not asparagus.

I won't argue anymore cos frankly I cba, but I don't accept your assertions.

Asparagus staging doesn't need to fire all engines simultaneously, although it can.

Not all engines need to draw from the furthest tanks.

Assemblies do not need to be paired.

You are of course free to define asparagus however you want in your own mind. Just as I could define "fork" as anything used to put food in my mouth and then argue that spoons and chopsticks are forks. I would expect disagreement from people when using that definition of "fork", you should probably expect the same using your definition of "asparagus".

Late edit to add: The ship I posted is not bamboo staged. Bamboo staging is when all the engines are in the uppermost stage, and tanks are drained and dropped one at a time. Mhoram wrote an excellent overview of the common staging methods used in KSP here, it's worth a read.

Edited November 13, 2014 by Red Iron Crown

[The_Rocketeer]

Actually the term wasn't invented by this community. Mis-use it and claim it if you must, but it doesn't make you right.

Edit: See this issue of Popular Science from March 1978

Edited November 13, 2014 by The_Rocketeer

[Pecan]

Humpty-dumpty words ("When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to meanâ€â€neither more nor less." Through The Looking Glass)

When I use a word:

Radial = side-mounted stages used and jettisoned before the next-stage engine(s) are ignited

Parallel = side-mounted stages used at the same time as the next-stage engine(s) but jettisoned before

Onion = as parallel but using fuel lines to keep the inner/core fuel tanks full until all earlier stages have been jettisoned

Asparagus = special-case of Onion using symmetry-2

It would seem by my definitions that side-mounting is a necessary part of the definition of 'asparagus' (as The Rocketeer is arguing), whereas there are other crossfeed configurations that I use and still consider such.

The conclusion is that I can't even come-up with a consistent definition in my own terms. Ho hum :-(

[sal_vager]

Guys, the asparagus we use is not quite the original, seen here:

But when we use the term, we do mean a specific kind of booster arrangement where fuel is fed into the next pair (or batch, doesn't have to be individual boosters) to keep the remaining boosters fully fuelled during flight.

So please, no more arguing, we're all wrong

[GoSlash27]

Rocketeer,

I think by the OP's wording, he's referring to the same concept the rest of us are.

Asparagus staging refers to parallel tank/ engine assemblies where all engines are firing and the outer stages crossfeed fuel and oxidizer to the inner stages and are discarded when empty.

Simply radially attaching boosters is not "asparagus staging"... at least not by anyone's definition except yours.

I think Red Iron said it best:

I could define "fork" as anything used to put food in my mouth and then argue that spoons and chopsticks are forks. I would expect disagreement from people when using that definition of "fork", you should probably expect the same using your definition of "asparagus".

Best,

-Slashy

[Red Iron Crown]

Actually the term wasn't invented by this community.

I never claimed otherwise.

Mis-use it and claim it if you must, but it doesn't make you right.

I'm not "claiming" it, just trying to help you understand it as the community commonly uses it.

[Jouni]

Actually the term wasn't invented by this community. Mis-use it and claim it if you must, but it doesn't make you right.

Edit: See this issue of Popular Science from March 1978

I wrote "The term 'asparagus staging' is specific to the KSP community, even though there are some obscure real-world connections." Other people had used the word 'asparagus' in connection with similar staging methods before, but those were rare isolated cases, and even they didn't call their staging methods 'asparagus staging'. Essentially every use of the term 'asparagus staging' is within the KSP community, so it's reasonable to say that the term is specific to the community.

As a related note, KSP players are probably going to redefine some rocketry terms, if the game remains popular in the long term. Some time ago, the most frequent meaning of the term 'SSTO' in the world was "KSP spaceplane". 0.24 probably changed that by making SSTO rockets relevant, but the lesson was that KSP players can easily outnumber the people using rocketry terms in a real-world context.

[worir4]

I don't need staging at all!!! (This is where my speach ends to the new recruits)

(Privately) My rockets never survive long enough for a fuel tank to run out...

[GoSlash27]

Eve landers are just a bit bigger without asparagus staging. As a quick estimate, a 200-tonne lander should be able to lift 1 tonne of payload by using two Mainsails in the first stage, a Skipper in the second stage, an LV-T30 engine in the third stage, and two 48-7S engines in the fourth stage.

Jouni,

My asparagus lander does the same job (1 tonne to Eve orbit) with a total mass on the surface of 52 tonnes, so it's more than just a little more mass-efficient. And my design traded off mass ratio for aspect ratio, structural rigidity, and ability to be refueled on the surface, so it *could've* been lighter.

Asparagus staging can make a huge impact on mass ratio.

Best,

-Slashy

[The_Rocketeer]

Simply radially attaching boosters is not "asparagus staging"... at least not by anyone's definition except yours.

I think you've misread my posts.

As a related note, KSP players are probably going to redefine some rocketry terms, if the game remains popular in the long term.

I laughed at this, but a small sick part inside me knows it's true.

This is literally my last post in this thread, I'm not even going to check here again so please don't address any more replies to me.

Who knew that space-Nazis really do exist?

[GregA]

/spacexfanboy

The SpaceX Falcon Heavy, is three Falcon 9 rockets bolted together with struts and cross feed. When it is launched later this year, it will be the heaviest lifter devised, but for the Saturn rocket that launched Apollo Missions. However IRL, the amount of fuel that is needed to feed a rocket makes SpaceX's cross feed only a partial solution. The center rocket will still be throttled down until first stage separation, to conserve fuel in the center tank.

If Kerbal wanted to make fuel cross feed more realistic, they would simply limit the rate which fuel is capable of flowing through the crossfeed. But it is an efficient way to make bigger rockets (IRL, I am not going to argue with SpaceX's methods, but then Im a fanboy) it add nominal weight to rockets, it uses the existing engine turbo pumps to move the fuel around.

As far as the aerodynamics is concerned... I was a Space Shuttle fanboy for many years, and I have spoken to numerous NASA engineers and astronauts about this... The space shuttle had ~horrible~ sub hypersonic aerodynamic qualities. They deliberately launched the Space Shuttle at sub optimal rocket equation speeds until something they called MaxQ to compensate for this. I qualify with, I am not an aerospace engineer...

The reason Asparagus staging works so well in Kerbal, and not irl is because Kerbal rocket hardware is a much larger percentage of total vehicle weight than IRL. IRL, there is not as much advantage to building with an Asparagus design.

[GoSlash27]

I don't need staging at all!!! (This is where my speach ends to the new recruits)

(Privately) My rockets never survive long enough for a fuel tank to run out...

Actually, I really *don't* use staging on Eve. Not anymore.

My colonization plan requires SSTO everywhere to simplify logistics, so I cheated like Hell. Infiniglide coupled with Kraken drive gets me from Eve surface to orbit and back to base without a drop of fuel.

Ain't 'shamed,

-Slashy

[Jouni]

My asparagus lander does the same job (1 tonne to Eve orbit) with a total mass on the surface of 52 tonnes, so it's more than just a little more mass-efficient. And my design traded off mass ratio for aspect ratio, structural rigidity, and ability to be refueled on the surface, so it *could've* been lighter.

Asparagus staging can make a huge impact on mass ratio.

Do you have a link to the lander? Usually the Eve landers that can launch a Mk1 command pod from sea level are at least 150 tonnes.