Asparagus Staging

[almagnus1]

Something that I used to do in KSP1 that I stopped doing (because they fixed the game) was asparagus staging.  How well does this work in KSP2?

Also, how are fuel tanks emptied in KSP2?

[tstein]

17 minutes ago, almagnus1 said:

Something that I used to do in KSP1 that I stopped doing (because they fixed the game) was asparagus staging.  How well does this work in KSP2?

Also, how are fuel tanks emptied in KSP2?

Asparagus still worked and gave you some advantage in KSP1. THey just made a simpler way to achieve the same effect.

 

In KSP 2 it is not reliable due to the fuel flow issues.

[LameLefty]

I’ve had no problem with “Delta Heavy/Falcon Heavy” style rockets with crossfeed from boosters to core stage, but those are the only kind I’ve tried. I have not tried a true 4 or more booster design. 

Edited March 3, 2023 by LameLefty

[magnemoe]

1 hour ago, LameLefty said:

I’ve had no problem with “Delta Heavy/Falcon Heavy” style rockets with crossfeed from boosters to core stage, but those are the only kind I’ve tried. I have not tried a true 4 or more booster design. 

It was more relevant earlier as we only had 2.5 m tanks. I had more use for this for Eve exits or very high dV intercepts.

[almagnus1]

12 hours ago, tstein said:

In KSP 2 it is not reliable due to the fuel flow issues.

What is it doing that's making it difficult?

 

[Sequence]

2 hours ago, almagnus1 said:

What is it doing that's making it difficult?

 

There's a performance issue with fuel moving between tanks. So both fuel lines and multiple engines drawing from the same tank are impacted. Asparagus staging is probably best avoided until these issues are resolved else you'll see a significant drop in FPS. 

[Mutex]

AFAIK in KSP2 currently, a fuel line will only transfer fuel from one tank to another, not a cluster of connected fuel tanks to another. Say for example, if you have two fuel tanks in your core stage, and two side boosters each with two fuel tanks, you want to connect fuel lines from each booster fuel tank to the corresponding core stage tank. This is what I did yesterday and it worked fine.

I haven't tried linking boosters to boosters (so that you can drop a pair of empty boosters each time you stage) yet.

[Fullmetal Analyst]

sounds like some sort of deadly disease

[caipi]

I've actually tried Asparagus Staging and right now, due to technical issues with fuel flow, it is not worth it. But even if fuel flow would be working correctly, it is much harder to do due to VAB disimprovements.

But let me explain in detail.

I used a simple rocket with an upper stage (including an upper stage tank and engine, let's call them UST for upper stage tank and USE for engine respectively), a main stage tank (MST) and engine (MSE), and 6 attached tanks and engines (outer stage tanks/engine A, B, C - OST/OSE A, OST/OSE B, and C - A dropped first, C dropped last, fuel pumps from A > B > C > MST). The MSE was more for a low pressure environment, so it was supposed to fire when I dropped the first tanks and engines, OST/OSE A. So, first stage, ignite engines OSE A-C, which should be fed from tank OST A. I started watching the tanks empty. OST A and B were emptying, A emptied twice as fast as B. So What I assume that happened is that OSE A and B were correctly fed from OST A, but OSE C was fed from OST B (because the fuel pump was going from OST B to OST C) - it looked like the fuel pumps do not daisy-chain correctly.

Second stage, I dropped OSE and OST A and ignited MSE. OST B and C were emptying (C at a slower rate). I temporarily disabled the MSE to check, and OST C wasn't been drained anymore. So same problem as above, there is a fuel pump from OST C to MST, but the MSE did not recognize the daisy chain from OST B to C. OSE C was correctly fed by OST B. Everything clear so far? Okay, now comes the weird part.

When I eventually dropped OST C (the last outer stage), suddenly the upper stage tank and the main stage tank were drained by the main stage engine even though there was a separator between them and cross fuel flow was disabled. But this appears to be a known bug. Not all parts have the "cross fuel flow = false" parameter. That leads to an issue. If it is not present in a part, the system seems to think that cross fuel flow = true for some weird reason (at least that's what I read on steamcommunity). So some parts like a parachute, landing legs, and/or an antanna, which does not have cross fuel flow in its part parameters seems to have falsely activated that for the entire stage...

Those were the current technical issues/bugs. Now let's come to the design issues.

Fuel Flow Priority has been removed and cannot be set manually anymore - I considered this a vital piece of KSP1. Don't ask me why it has been removed. I think it might even fix the issue the incorrect cross fuel flow.

If you add parts in a symmetry, you cannot separate them in staging by clicking on them anymore, like we did in KSP1. So adding 6 decouplers and separating them into 3 stages is not possible. They can only be put and triggered into one stage. But the Action Group manager still allows you to decouple them in pairs. So I put the two Decouplers for OST A on button 1, for OST B on 2, and OST C on 3. That's a workaround for a "small" and simple rocket design. But as soon as you have more than 10 asparagus stages or want to use the action manager for other stuff, you're gonna run out of options. So you'll have to pause the game and manually decouple stuff. Yay! -_-'

Not being able to "remove part from symmetry" also makes it harder to place fuel pumps, as you cannot do so in symmetry mode anymore. You have to place each one on its own. That, again, might still be fun for a small design, but as soon as you hit a big part count, that's gonna be a real nightmare.

Finally, if you think that you can just circumvent the current issues with fuel transfer: The new interface is just a nightmare (it can still be done, but is now under resource manager) and the fuel transfer stops once the tank was full for a split second. There is no continuous fuel transfer into a tank. Yet another disimprovement.

 

I hope it helped and that you could follow my explanation. If anything was unclear, let me know.

[Chilkoot]

Wait - is asparagus not really necessary in KSP 1 anymore?  I thought it was still quite a bit more efficient if you were all liquid-fuel powered boosters.

[whatsEJstandfor]

4 minutes ago, Chilkoot said:

Wait - is asparagus not really necessary in KSP 1 anymore?  I thought it was still quite a bit more efficient if you were all liquid-fuel powered boosters.

I thought so, too. As far as I knew, it's so efficient that, if the engineering and cost were feasible to do it in real life, it'd pretty much be the standard way to launch to deep space.

[Soda Popinski]

23 minutes ago, whatsEJstandfor said:

I thought so, too. As far as I knew, it's so efficient that, if the engineering and cost were feasible to do it in real life, it'd pretty much be the standard way to launch to deep space.

Asparagus staging is useful in KSP(1) because of the unrealistic dry weight of the fuel tanks and rockets.  So it makes much more sense to dump the extra weight, unlike real rockets, where 99% of the mass if fuel.

The other reason asparagus staging worked well in early KSP1, was the simple aero system.  Early KSP (beta), had drag per part, where having parts in line with each other didn't help.  Once having parts in-line reduced drag, it made more sense to make longer rockets instead of flatter ones.

[Starhawk]

Asparagus staging is inherently more efficient in KSP1 and, I am certain, continues to be the case in KSP2.

And, as pointed out, since this isn't real life but a simulation without many of the real limitations (fuel in KSP moves at the speed of calculation) asparagus staging works wonderfully.
The engineering is much trickier, however, even in the kerbal universe.
 

Happy landings!

[LameLefty]

It is also absolutely worth pointing out that when 3.75m parts were added with the Asteroid Redirect stuff, it became substantially easier to launch reasonable masses to LKO without the need for anything more complicated that strap-on solids or liquids cross-feeding into the core booster stage. Giant docking ports made it easier to build massive interplanetary stations and stage missions from orbit without needing utterly ridiculous single-launch monstrosities unless you were a YT creator doing it as a stunt for the clicks and the "Look what I did, lolsokerbalamiright?" factor. 

[Jarin]

11 hours ago, Fullmetal Analyst said:

sounds like some sort of deadly disease

"Give it to me straight, doc. I can take it."

"You have stage 3 Asparagus, I'm sorry."

[Mutex]

45 minutes ago, Jarin said:

"Give it to me straight, doc. I can take it."

"You have stage 3 Asparagus, I'm sorry."

Main symptom is it makes your urine smell funny

[Starhawk]

This is a pic of extreme asparagus staging in KSP1.  This was from a craft I made back in 2015.  No proper aerodynamics at that point so we built pancake rockets.

There is also a type of staging known as onion staging.  In onion staging the fuel lines would run from the central core straight out along each 'arm' from tank to tank.    Each ring of boosters is dropped together.  A bit more efficient than conventional staging but nowhere near as good as asparagus.  Much simpler to set up however.

Happy landings!

Edited March 9, 2023 by Starhawk
Clarity

[RocketRockington]

5 hours ago, Starhawk said:

Asparagus staging is inherently more efficient in KSP1 and, I am certain, continues to be the case in KSP2.

And, as pointed out, since this isn't real life but a simulation without many of the real limitations (fuel in KSP moves at the speed of calculation) asparagus staging works wonderfully.
The engineering is much trickier, however, even in the kerbal universe.
 

Happy landings!

 

2 hours ago, Starhawk said:

This is a pic of extreme asparagus staging in KSP1.  This was from a craft I made back in 2015.  No proper aerodynamics at that point so we built pancake rockets.

There is also a type of staging known as onion staging.  In onion staging the fuel lines would run from the central core straight out along each 'arm' from tank to tank.    Each ring of boosters is dropped together.  A bit more efficient than conventional staging but nowhere near as good as asparagus.  Much simpler to set up however.

Happy landings!

Onion staging has at least been in real world blueprints.  Falcon heavy was meant to have fuel crossfeed that would have been that -scrapped for complexity and reliability.  The UR-700 was a rocket that saw significant development but never made it past the design stages for.. Soviet reasons and because it would have been a toxic disaster when it (inevitably) had pad failure.

[K^2]

On 3/3/2023 at 10:31 AM, tstein said:

In KSP 2 it is not reliable due to the fuel flow issues.

It's annoying, but you can work around it. A bit in advance of where you expect to drop the tanks, pause the game, go into resource manager, and set up the transfer. Unpause the game, and watch the gauges. Once the drop tanks are empty, jettison them. You don't have to time the fuel transfer perfectly. If you start a bit early or a bit late, you'll just be carrying the extra weight a little longer, but you'll still have all the same engines firing, so the loss of efficiency is fairly minimal.

Because building up results in very wobbly rockets, despite the inconvenience, I would still recommend relying on asparagus heavily. It gives you good places to attach struts to give your craft the rigidity it needs to survive the ascent gracefully.