I’ve rediscovered asparagus staging! And have officially given up on SSTO rockets.

[Pecan]

35 minutes ago, SSgt Baloo said:

I think that's called "onion staging".

Yes - asparagus staging is just a special-case of onion staging using symmetry-2.  The reason it's more mass-efficient is that it's quicker to use and jettison 2 tanks of a given size than 3 or more.  Dropping one tank at a time is even better but you can't drop a tank from just one side and expect a rocket to fly straight ^^.

@Gaarst - on that subject.  I disagree with your perscription for mass efficiency.  That's exactly where asparagus wins.  Take the typical example of a core plus 2 "liquid fueled strap-on boosters", for examples.  Add two fuel-lines -> asparagus.  You already have the decouplers and with the fuel lines you can reduce mass by taking less fuel.  Whether the saving is worth it in current KSP I won't argue.

Edited June 29, 2016 by Pecan

[tomf]

Asparagus can still be pretty cost efficient too. 90% of my lifters end up with a pair of side mounted boosters. For my typical payloads I find a stage powered by a mainsail isn't quite enough to get to orbit, and rather than having to go up a size category and put a Mammoth on the bottom it is considerably cheaper to strap another pair of mainsails onto the side.

[Archgeek]

Heh, it seems the bar for asparagus categorization has fallen a bit.  'Used to be a single layer of crossfeed was just that, a few boosters cross-fed into the core.  It wasn't onion staging until you had a ring of outer boosters feeding inner boosters, like the layers of an onion; and it wasn't asparagus staging until you had at least one pair of boosters feeding into another, which I very often do if I've got 4 side stacks.  If they're there already, I figure why not crossfeed 'em?

[Tw1]

1 hour ago, Archgeek said:

Heh, it seems the bar for asparagus categorization has fallen a bit.

I agree. It's not truly onion or asparagus until you've got these layers.  

[HebaruSan]

2 hours ago, Pecan said:

Dropping one tank at a time is even better but you can't drop a tank from just one side and expect a rocket to fly straight ^^.

That may no longer be the case with careful use of the rotate gizmo. I might have to spend some time in the VAB today...

[LaytheDragon]

11 minutes ago, HebaruSan said:

That may no longer be the case with careful use of the rotate gizmo. I might have to spend some time in the VAB today...

Do you mean placing the engines radially or on a beam below the fuel tanks, and having seemingly-stack-attached fuel tanks connected with radial decouplers and fuel lines, rotated to be in line with what appears to be a center stack? The I-Beam approach would make the beam part clip inside the fuel tanks, but the radial engines wouldn't.

Or, even better, you could have two I-beams going around the fuel tanks attached in that manner described above, so they'd eject out of one of the two open sides, while an I-beam would wrap around each of the other two parallel sides leading to an engine attached on one of them at the bottom (the beams would be strutted together at the bottom below the fuel tanks, and the engine would look like it were attached to both). If done so the top fuel tanks in the "stack" ejected first, it would look like what one would imagine would be called "banana staging", and the fuel lines would conveniently lead directly down, from fuel tank to fuel tank, straight to the last fuel line on the bottom ejectable tank that would feed to the engine.

Edited June 29, 2016 by LaytheDragon

[HebaruSan]

17 minutes ago, LaytheDragon said:

Do you mean placing the engines radially or on a beam below the fuel tanks, and having seemingly-stack-attached fuel tanks connected with radial decouplers and fuel lines, rotated to be in line with what appears to be a center stack? The I-Beam approach would make the beam part clip inside the fuel tanks, but the radial engines wouldn't.

Or, even better, you could have two I-beams going around the fuel tanks attached in that manner described above, so they'd eject out of one of the two open sides, while an I-beam would wrap around the other two parallel sides leading to an engine attached on one of them (the beams would be strutted together at the bottom below the fuel tanks, and the engine would look like it were attached to both). If done so the top fuel tanks in the "stack" ejected first, it would look like what one would imagine would be called "banana staging", and the fuel lines would conveniently lead directly down, from fuel tank to fuel tank, straight to the last fuel line on the bottom ejectable tank that would feed to the engine.

Sorry, I don't quite follow what you're getting at with those ideas, but here's a stock craft (Orbiter One) that hints at what I had in mind:

[Green Baron]

When it comes to putting something heavy up, and doing it fast and efficient, asparagus is mandatory. The simplest is 3 cores, like described by Pecan. It reduces unneeded mass and prolongs burntime. Combined with the right engine choice (rocket parts pack(s)) it's hard to imagine anything more efficient.

SSTOs are nice, but 200t 80t payload into orbit is hard work ... (nothing against hard working people :-))

 

Edited June 29, 2016 by Green Baron
boasting corrected

[Corona688]

7 hours ago, Gaarst said:

So you're saying that, because SSTO rockets are difficult to recover and engineer and can be inefficient, you have switched to the most inefficient way of staging a rocket (cost- and mass-wise): asparagus ?

Is "asparagus" just a synonym for "wide", these days?  As I understand the term, my smallest and most efficient rockets are generally asparagus.  Even my mammoth superlifter got smaller when I converted it from traditional to asparagus staging, needing to discard fewer engines on the way up.

Of course, people can and do use this principle to go even heavier and larger, but asparagus certainly doesn't force you to do that.

Edited June 29, 2016 by Corona688

[Gaarst]

4 hours ago, Pecan said:

 - on that subject.  I disagree with your perscription for mass efficiency.  That's exactly where asparagus wins.  Take the typical example of a core plus 2 "liquid fueled strap-on boosters", for examples.  Add two fuel-lines -> asparagus.  You already have the decouplers and with the fuel lines you can reduce mass by taking less fuel.  Whether the saving is worth it in current KSP I won't argue.

Yes, a simple asparagus with 2 boosters is an efficient design.

What I was thinking of was the usual 6 boosters configuration of asparagus, or multi-layer design, which are extremely heavy and not very efficient. I should have made that clearer.

15 minutes ago, Corona688 said:

Is "asparagus" just a synonym for "wide", these days?  As I understand the term, my smallest and most efficient rockets are generally asparagus.  Even my mammoth superlifter got smaller when I converted it from traditional to asparagus staging, needing to discard fewer engines on the way up.

Of course, people can and do use this principle to go even heavier and larger, but asparagus certainly doesn't force you to do that.

Asparagus is a core, with 2 side boosters that fuel feed the core, 2 side boosters that fuel feed the 2 other boosters, 2 side booster that fuel feed the second pair of boosters and so on. That way, fuel from only the "outer" booster will be drained and you will drop them first, followed by the next pair and so on.
Though asparagus can be as light as one core and 2 boosters with crossfeed (like FH was supposed to be).

I find strange that your heavy lifter got smaller with asparagus than otherwise. Of course it depends on how it is designed in the first place, but I remember going the other way round (getting lighter) when switching all my asparagus rockets to more conventional types back in 1.0.

Edited June 29, 2016 by Gaarst

[Corona688]

30 minutes ago, Gaarst said:

Asparagus is a core, with 2 side boosters that fuel feed the core, 2 side boosters that fuel feed the 2 other boosters, 2 side booster that fuel feed the second pair of boosters and so on. That way, fuel from only the "outer" booster will be drained and you will drop them first, followed by the next pair and so on.

That's exactly what I thought.  Until they nerfed the little red engines, I could make orbit with two of them and the lander engine -- but only in an asparagus arrangement.  With that little thrust, it was a fine line between being able to make orbit and being able to lift off at all.

Mathematically speaking, you can balance things kind of like asparagus by making your outer stages smaller and moving more fuel tanks into the core -- but the higher you go, the more dead-weight empty tanks the core must carry.  Stacking stage atop stage lets you ditch empty tanks, but then you carry dormant engines instead, which amount to literal tons of dead weight until those engines finally become available.

Asparagus lets you do both -- get rid of unneeded engines and empty fuel tanks simultaneously, without forcing you to carry any engines which don't contribute thrust.

In real life, of course, asparagus is very difficult, you can't just pipe lox around like so much beer from keg to tap.  All the same I bet it'll happen sooner or later.  The benefits are obvious.

[edit] Actually, it has been done actually, hasn't it -- in the Space Shuttle.  The external tank didn't have its own rockets, but otherwise the idea is similar.  Not that the space shuttle is any example of great efficiency, but much like many monstrosities here, the wondeer is that it managed to orbit at all.

Edited June 29, 2016 by Corona688

[LaytheDragon]

1 hour ago, HebaruSan said:

Sorry, I don't quite follow what you're getting at with those ideas

That is why I just was tasked with building it myself. Behold, Banana Staging! (Please, if you can, help me find a better name for it) 

In the background, I am starting Banana Staging Test 2, so I'll post that soon, @HebaruSan.

 

Edited June 29, 2016 by LaytheDragon

[Corona688]

51 minutes ago, Gaarst said:

I find strange that your heavy lifter got smaller with asparagus than otherwise.

When your stages are all mainsails, that's a lot of big engines being wasted!  Asparagus let me throw away more tanks than engines.   It also let me control more conveniently and exactly when staging happened, just by making the side pods shorter or higher.

Also, the rocket equation is a tyrant and no design can really be "converted" that easily.  A stacked design blindly converted to asparagus will end up under-engined, requiring more fuel more engines to carry the fuel, I don't know why she swallowed the fly, perhaps she'll die.

Edited June 29, 2016 by Corona688

[Tyko]

26 minutes ago, Corona688 said:

In real life, of course, asparagus is very difficult, you can't just pipe lox around like so much beer from keg to tap.  All the same I bet it'll happen sooner or later.  The benefits are obvious.

The Space X Falcon Heavy uses asparagus staging - at least from outer tanks to main stack. It's not the complex multi-layers monstrosities that we make, but it does work.

EDIT: this was proposed, but not implemented:

Cancelled propellant crossfeed

Falcon Heavy had originally been designed with a unique propellant crossfeed capability, where some of the center core engines are supplied with fuel and oxidizer from the two side cores, up until the side cores are near empty and ready for the first separation event.^[35] This allows engines from all three cores to ignite at launch and operate at full thrust until booster depletion, while still leaving the central core with most of its propellant at booster separation.^[36] The propellant crossfeed system, nicknamed "asparagus staging", comes from a proposed booster design in a book on orbital mechanics by Tom Logsdon. According to the book, an engineer named Ed Keith coined the term "asparagus-stalk booster" for launch vehicles using propellant crossfeed.^[37] Elon Musk has stated that crossfeed is not currently planned to be implemented, at least in the first Falcon Heavy version.^[38]

Edited June 29, 2016 by tjt
corrected my earlier statement about Falcon Heavy

[Corona688]

Well, nuts.  Though I'm not surprised.  They always want to do that but it's hard enough to make welds which hold liquid gases, let alone a self-sealing quick-release mechanism.

 

[Zamite]

The only reason I do SSTOs and Asparagus is because I like to have fun

Then again, that's true for everything I do in this game.

[Tyko]

1 minute ago, Zamite said:

The only reason I do SSTOs and Asparagus is because I like to have fun

Then again, that's true for everything I do in this game.

Agreed...furthermore whenever I start to think that "this isn't entirely realistic" I remind myself that the game isn't set on Earth and these aren't humans. Just because there are striking similarities to Earth projects doesn't mean the technology has to be identical. Kerbals solved ways to move fuel around. They've also, apparently, solved how to go for days/months/years without entertainment or food.

[Zamite]

1 minute ago, tjt said:

Agreed...furthermore whenever I start to think that "this isn't entirely realistic" I remind myself that the game isn't set on Earth and these aren't humans. Just because there are striking similarities to Earth projects doesn't mean the technology has to be identical. Kerbals solved ways to move fuel around. They've also, apparently, solved how to go for days/months/years without entertainment or food.

Mystery of the space frogs.

[Corona688]

57 minutes ago, LaytheDragon said:

That is why I just was tasked with building it myself. Behold, Banana Staging! (Please, if you can, help me find a better name for it)

If that were an aircraft, it'd be a drop-tank.  So, drop-tank.

Why not use the radial engines, so you can stage fuel tanks below them?

[GoSlash27]

Asparagus staging *can* be cheap if done right, even cheaper than most recoverable designs.

Here's my entry for the "cheap and cheerful" challenge:

http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/CnCRocketFactoryII/IIc2

135t to orbit at under $650 per tonne without bothering to recover any of the launch vehicle. It uses a scheme that I dubbed "quasi-asparagus" staging, where SRBs are used to impart boost thrust while lifting asparagus staged LF&O tanks.

 Now that I think about it, all of the top scoring entries in that competition used an asparagus staging scheme.

Best,
-Slashy

 

 

Edited June 29, 2016 by GoSlash27

[Corona688]

Nothing wrong with asparagus + sustainer engine.  Cool.

8 hours ago, Gaarst said:

since 1.0 and the aerodynamics overhaul, people realised that asparagus had become very draggy reducing its efficiency further down.

Are aerodynamics still calculated per-part instead of some sort of cross-section?  Because large asparagus things were always incredibly draggy.

Edited June 29, 2016 by Corona688

[LaytheDragon]

2 hours ago, Corona688 said:

If that were an aircraft, it'd be a drop-tank.  So, drop-tank.

Why not use the radial engines, so you can stage fuel tanks below them?

I am testing the radial engines version, but with Banana Staging.

Edit: After testing, as far as I can tell, I have created an inline version of asparagus staging (still two engines are being dropped at once, and two sets of one engine each with half the fuel is identical, except in radial form). I DID create a way to drop one drop tank at a time though for rockets, by making the drop tanks inline. Also, no fuel lines are required for either of these if docking ports are used rather than stack or radial decouplers, though only using a 0.75 meter docking port as a decoupler also saves mass from using stack and (rocket) radial decouplers.

Edited June 30, 2016 by LaytheDragon

[herbal space program]

10 hours ago, Johnny Wishbone said:

Once we had stock parts with that kind of power and fuel capacity, asparagus staging quickly became a thing of the past. The new parts made lifter designs a lot simpler and reduced part count.

It really just depends on what you're trying to do. If you're trying to maximize the deltaV you can get out of a given launch weight off the pad, then you'll still want to use asparagus staging. If it's about money or you  just want to put something into orbit without a lot of fuss, then you can always just use an OP lower stage and recover it or not.

[MDZhB]

I've been using asparagus for most of my big lifters this whole time. I picked up the idea back when I had the demo, and I've kept it since. It seems to work fairly well for me. I never need to make SSTOs anyway because I play almost exclusively on sandbox.

[herbal space program]

1 hour ago, GoSlash27 said:

Asparagus staging *can* be cheap if done right, even cheaper than most recoverable designs.

Here's my entry for the "cheap and cheerful" challenge:

http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/CnCRocketFactoryII/IIc2

135t to orbit at under $650 per tonne without bothering to recover any of the launch vehicle. It uses a scheme that I dubbed "quasi-asparagus" staging, where SRBs are used to impart boost thrust while lifting asparagus staged LF&O tanks.

 Now that I think about it, all of the top scoring entries in that competition used an asparagus staging scheme.

Best,
-Slashy

 

 

So even if money is the key consideration asparagus can still be still the way to go. I guess it depends on how expensive the engines you drop are. I imagine that Reliant and Swivel-based stages could often be more economical to just drop.