New SLS vs Asparagus

[CalculusWarrior]

whackjobs next task - bring a class E asteroid down to kerbin, and then launch it back into orbit

Why stop there? He could do a grand tour with the asteroid!

[NecroBones]

Last night I spent my time building new lifters for a variety of test payloads. I think Asparagus isn't going to go away any time soon, but the new parts certainly reduce the incentive to use it.

For instance, for a 200 Ton test-payload (the cluster of 5 orange tanks + 5 poodles at the top, in the image below), I built a booster that uses some vertical staging, plus four 3.75m boosters that are asparagus-staged, plus four 2.5m boosters that are technically "onion" staged (though the pairs run down and eject at different times due to their virtual "distance" from the center stage). Instead of something like 18+ mainsails in an asparagus/pancake lifter, I get something that's a lot prettier (still bulky, but not a pancake):

[mellojoe]

I agree with the sentiment that asparagus isn't going away.

Take the same payload-to-oribt, and now you can do it with much less parts, much less lag, and many fewer stages. Using the same number of stages, the same amount of parts, just swapping to the larger sized parts & engines will simply mean larger payloads to orbit in a single shot.

I have found that my 100-Ton-to-Orbit craft is so much simpler using the larger parts. My previous Heavy-Lifter had a capability of about 140-Tons-to-Orbit as a maximum, and it was nearly a dozen stages, with orange tanks as drop danks, 8-way asparagus staged, needing tons of struts and winglets to keep it straight and steady, etc etc. So much simpler now. Even with zero planning, I was able to boot-strap a lifter stage using much fewer parts, much less headache and hassle.

[Pecan]

Spartwo:

I don't like it because..

1:It looks ugly.

2:It requires a ton of staging.

3:I don't really care about mass efficiency more about part efficiency,and linear staging leaves me with a lower part count for almost all ships.

1. Not if you do it right.

2. Fewer stages, or no more than other strategies, since you don't need as much fuel in the first place.

3. Fair comment, and a good reason not to use it. Part Count (2 decouplers + 2 fuel lines vs 1 decoupler = -3 to asparagus).

maccollo:

"Regardless of whether the aerodynamic model is accurate or not asparagus will still be the most efficient method."

Yup.

Moar Boosters:

==> Summed up these two points of view perfectly.

jwenting:

"Hardly. I rarely use it, and when I do it gives me about a 1% increase in the dV of the affected stages on average. Not worth writing home about, if you're that critical in your dV budget it's time to rethink your design concept."

Indeed, if it was only worth 1% it wouldn't be worth the fiddly fuel lines. I'm surprised though - I usually get ~10% better than 'onion' (same thing, higher symmetry) and ~20-30% better than stack/radial/parallel. I'd like to see some of your 18%+ payload-ratio designs that use something other than asparagus so that I can learn from them.

AmpsterMan:

"Meh. I like using serial staging for one simple reason. It usually has a higher TWR than a asparagus stage. ... snip ... For launchers I use cheap (i.e. Low part), reliable vehicles whereas my spacecraft are part heavy machines."

a. Not if you balance the engines

b. Low part - yup, been covered as a good reason for not asparagus.

(these are different anyway, so I might have missed the point you really meant?)

Sophistry:

"I think the thing that would actually kill Asparagus would be accurate modelling of the inertia of the fuel - which I don't think is likely. All that fuel sloshing rapidly inwards and sideways would make the rocket spin like crazy until it flew apart."

Yes - conservation of rotational energy is the most plausible 'real world' argument against asparagus.

Cantab:

"Simply putting a significant mass on the fuel lines, essentially assuming their mass includes the fuel pumps needed as well, would nerf asparagusing."

I used to think that too, but 'direct' feed to the engines needs more or less the same fuel pumps anyway. Nevertheless they probably should be nerfed a bit - such as giving them any mass in flight.

[Red Iron Crown]

I think the thing that would actually kill Asparagus would be accurate modelling of the inertia of the fuel - which I don't think is likely. All that fuel sloshing rapidly inwards and sideways would make the rocket spin like crazy until it flew apart.

I don't think it would matter. Moving fuel is a zero sum game acceleration-wise in that the reaction force from pumping the fuel from the source tank is balanced by the reaction force of the fuel stopping moving in the destination tank.

[tygoo7]

What about SLS + Asparagus? That'll get a lot to orbit.

[cantab]

I used to think that too, but 'direct' feed to the engines needs more or less the same fuel pumps anyway.

Indeed. Those pumps, however, can be regarded as part of the engine's own mass.

As for fuel flow between tanks in a stack, I sort of handwave that away as an abstraction, the rocket "really" has one tank the full length.

[Pecan]

@cantab above, if I've typed quickly enough:

Yes, I don't think we'd have too much disagreement about this. Totally agree about stacked tanks. What to do about cross-stack fuel lines (which is all asparagus comes down to) I'm not so sure, partly because 'onion' is perfectly legitimate/real-life (side-stacks into core).

[merendel]

Why stop there? He could do a grand tour with the asteroid!

oh you are thinking way too small. Grand tour with landings on every planet with a surface (droping down to 0m on jool optional) topped off by puting it into a retrograde low kerbol orbit The fuel required to do that with a class E would be staggering.

[Eric S]

@cantab above, if I've typed quickly enough:

Yes, I don't think we'd have too much disagreement about this. Totally agree about stacked tanks. What to do about cross-stack fuel lines (which is all asparagus comes down to) I'm not so sure, partly because 'onion' is perfectly legitimate/real-life (side-stacks into core).

Agreed, any attempt to make asparagus non-viable based on reality needs to go after the fuel lines, either making them expensive, capping their maximum fuel flow, or something like that. I don't like the idea of just making them expensive because the same fuel lines that enable asparagus monstrosities enables drop tanks which I don't think anyone has a problem with. I though about making different fuel lines with different flow limits, but I don't think we need to add to the number of parts. Maybe if tweakables can adjust the max fuel flow and affect the cost (or maybe even give them a mass based on fuel flow), then that would resolve the whole thing in my mind.

Asparagus staging is the natural reaction to the combination of 1) low TWR engines, 2) high dry-mass fuel storage, and 3) low cost infinite flow, infinite reliability fuel pumps. I don't think changing the balance of the entire game to get rid of Asparagus staging is worth changing #1 or #2, and I also support the devs on their infinite reliability of parts, so that doesn't leave much to attack.

Aerodynamics really isn't the way to go about trying to nerf asparagus staging. You might manage to reduce the number of wider-than-tall rockets out there, but I'd be willing to bet that across the general KSP population, that would account for a fairly small percentage of asparagus rockets. I know that for me, it would be close to 1% of all asparagus launches.

[xzxvrx]

Who cares

Make a rocket so complicated it'll explode or something

That's what makes the game fun, when things go wrong and they are horrifically funny.

No matter what type of staging you go with, make sure it explodes in some way I'm tired of things going flawlessly.

[Pecan]

...Maybe if tweakables can adjust the max fuel flow and affect the cost (or maybe even give them a mass based on fuel flow), then that would resolve the whole thing in my mind...

Now that's an interesting idea. If, as cantab said, we can assume 'normal' pumps are included in engine mass then all this would mean is a bigger/fast fuel-line 'includes' a heavier pump. It might seem a bit like micro-management but it's certainly sensible.

EDIT: I APOLOGISE AND TAKE IT ALL BACK. I've now had a chance to download and actually play this version and, yes, it'll kill asparagus. Now I can single-stage a pod to Mun and back without breaking a sweat (VAB, 5 parts to make it look decent) there's not much point in staging and there's definitely no point in the construction and parts involved in asparagus. Who knew real rocket science was so easy?! That whole 'design' thing isn't necessary at all any more.

Edited April 3, 2014 by Pecan

[karolus10]

Who cares

Make a rocket so complicated it'll explode or something

That's what makes the game fun, when things go wrong and they are horrifically funny.

No matter what type of staging you go with, make sure it explodes in some way I'm tired of things going flawlessly.

KSP paradox: Enjoying the fireworks while everything went horribly wrong... this made trial&error learning fun instead being frustrating.

EDIT_1: Personally I didn't used asparagus staging as most heavy stuff I had launched needed only single core with 2 mainsails in the first stage.

If one mainsail aren't enought just add one more... right ?

EDIT_2: I also think that larger parts won't stop people from building "Asparagus" (I hate this name) rockets, it would just create bigger versions of them.

Edited April 3, 2014 by karolus10

[ArmchairGravy]

I use 2-deep onion stages for most everything, and only use asparagus if I absolutely have to. I've never had to use separatrons before, but I had to use them to kick the SLS LFB-KR's away. I could build an equivalent interceptor with non-SLS parts, but it'd take orbital assembly. SLS just saves me on parts and time it would take to assemble. Am I going to asparagus SLS? To futz around, sure, but it won't replace the onion/asparagus booster sets I've already created. Whingeing about people using asparagus because it offends your sensibilities is just plain silly as no one is forcing you to use it.