I love building asparagus rockets in KSP but don't see them much in real life.

[hobbsyoyo]

Thats my main concern with the orion capsule. They said literally: We have a million lines of code to get to the moon, and when we are there we'll have a million lines more." I also like the comparison Neil DeGrasse Tyson made between the Soyuz and the Space Shuttle. The shuttle was described as the most complicated machine man ever has designed, so naturally many things can go wrong. The Soyuz is dead simple. Just short of point and fire actually. Its a good work horse that has redundancy. So it is no surprise that Soyuz 5 survived a disastrous fall from space while the shuttle lost some wing tiles and disintegrated (I know it isnt right to downplay it, but I am describing the complexity of the Space Shuttle right now) I would rather have a sturdy and reliable workhorse of a craft then something that has a million and one ways to fail.

Don't get me wrong, I have full faith in the engineers working at and for NASA. There are SOOOOOOOO many success stories (lets not even get started on voyagers and Opportunity/Spirit,) but a complicated craft is not necessarily a good craft. If you don't have to deal with dangerous fuel lines IRL, then don't do it. Often times it is even more expensive and doesn't give you a net benefit (in costs and safety.) But it is good that somebody is trying it out IRL.

two things:

You're downplaying the serious accidents the Soyuz has had.

You're also downplaying the fact that a lot of the complexity of the shuttle was due to the enormous amount of redundancies it had (of course, there were some notorious single point of failures) and the fact it was reusable.

Adding some flames to the discussion

Asparagus staging in KSP is so good because people are lazy and design their rockets more by visuals rather than actual mission requirements. Even in KSP it's possible to make no fuel cross feed rocket to be almost as good as asparagus one. (For standard designs of course. For the ones stretching engine efficiency as hard as possible, cross feed will be much better.)

For example this rocket that was designed to as a Tylo land and return mission: Last three stages are the same, both rockets have the same engines and the same amount of fuel. There are no fuel lines in firsts pic, and there is asparagus staging on the first 3 stages in the second pic. The difference is only 8146m/s to 8327m/s and the asparagus has 0,01 more TWR on second stage.

8146m/s No fuel lines8327m/s asparagus with the same engines, launch mass and TWR.

So you are saying asparagus stagers are lazy, yet you build basically the exact same rocket that an asparagus stage-user would without the fuel lines and staging....am I missing something? If anything that would make you the lazy one. (no insult intended)

[Kasuha]

8146m/s No fuel lines8327m/s asparagus with the same engines, launch mass and TWR.

That asparagus one looks pretty sophisticated. It almost looks like you built a non-asparagus rocket and then built an asparagus rocket which matches its parameters. It might be interesting to watch that being done the other way.

I agree with you that asparagus is simpler to set up. And every time you stage, you have a rocket full of fuel, i.e. with highest possible ratio of fuel vs dead weight.

[Nao]

That asparagus one looks pretty sophisticated. It almost looks like you built a non-asparagus rocket and then built an asparagus rocket which matches its parameters. It might be interesting to watch that being done the other way.

I agree with you that asparagus is simpler to set up. And every time you stage, you have a rocket full of fuel, i.e. with highest possible ratio of fuel vs dead weight.

Of course you can make asparagus in such way that i would be impossible for similar no cross-feed rocket to compete. But it would be possible to design a reasonable asparagus launcher first and get similar efficiency out of no-asparagus modification.

In the end what matters are particular TWR of stages so the flight profile is efficient and engines are doing similar job (only real difference is fuel tank mass that gets accelerated further on no asparagus rocket), that's why i moved the fuel around and end up with fractions seen on the first stage of asparagus rocket (it's hard to divide a tank into three parts while moving fuel from center stack into the outers). If done the other way it would mean that the fractions would be on the no-asparagus one instead.

Also I'm currently designing no-asparagus ship for the Payload Fraction Challenge and I'm already at 17% mass efficiency at only 3 stages. Which is very close with other ships that use fuel lines. //Edit: got an entry with 4 stages and 18% payload efficiency, tied for the lead as of writing this//

So you are saying asparagus stagers are lazy, yet you build basically the exact same rocket that an asparagus stage-user would without the fuel lines and staging....am I missing something? If anything that would make you the lazy one. (no insult intended)

Not all asparaguses are lazy of course , but there are some designs where people blindly go "i need to add asparagus to my rockets to increase efficiency" but due to bigger errors in rocket design they don't make good use of the system.

I think it's easier to design efficient asparagus rocket just because each stage starts from full state, so we just add stage after stage to existing rocket keeping the same TWR and the whole thing flies well. But then if you look closely we end up with something like stock Kerbal X (not saying it's bad, its great for what it is supposed to be) with first 3 stages burning only 15-20s and next flying for 100s. And as we know, for engines with similar ISP the most effective use of staging is when each stage has very similar burn time.

Also since this thread is about why we don't see asparagus IRL while we often do in KSP, i wanted to point out that while asparagus can increase performance of any launch system, similar performance can be achieved by careful design. And since in IRL it's more costly to use those fuel lines we see efficient use of no cross-feed staging instead.

Edited October 29, 2013 by Nao
info on challenge entry added

[magnemoe]

Adding some flames to the discussion

Asparagus staging in KSP is so good because people are lazy and design their rockets more by visuals rather than actual mission requirements. Even in KSP it's possible to make no fuel cross feed rocket to be almost as good as asparagus one. (For standard designs of course. For the ones stretching engine efficiency as hard as possible, cross feed will be much better.)

For example this rocket that was designed to as a Tylo land and return mission: Last three stages are the same, both rockets have the same engines and the same amount of fuel. There are no fuel lines in firsts pic, and there is asparagus staging on the first 3 stages in the second pic. The difference is only 8146m/s to 8327m/s and the asparagus has 0,01 more TWR on second stage.

8146m/s No fuel lines8327m/s asparagus with the same engines, launch mass and TWR.

Simple and genial, you did the fuel balancing that asparagus provides and did it manual.

However you will have one loss, asparagus staging also drop empty fuel tanks used to carry fuel for upper stages. This is the main purpose of asparagus,

Not so visible on this design as you only have two booster stages, more visible with three.

Note that this will also make the rocket look more weird as you increase the size of the first boosters. Now you only miss two trashcans on each of the boosters

[WafflesToo]

As Eric S points out, think of that much mass moving in a clockwise direction *and stopping* -- you get no angular momentum from just moving mass around.

Where you might get into trouble is that if something exterior (i.e. the atmosphere) imparts angular momentum upon your rocket, and then you draw mass inwards. That makes you spin faster.

And I disagree with his conclusion. I do not see where the fuel "stops" until it reaches the inside tank at least, and at that is at a mechanical disadvantage.

Wouldn't be to difficult to an experiment, a few soda bottles and a bit of thread maybe? A couple of ballons to provide pressure to the outermost "tanks"?

[Eric S]

Asparagus staging in KSP is so good because people are lazy and design their rockets more by visuals rather than actual mission requirements.

I like your non-asparagus design. It achieves much of the advantages of asparagus staging by thinking outside the box. It doesn't surprise me that your "lazy" asparagus version of it doesn't show much improvement, but that's because the design wasn't made with asparagus in mind. By having three mainsails and three skippers, you're locked into a three branch, two stage design, and that's not particularly efficient.

[numerobis]

Wouldn't be to difficult to an experiment, a few soda bottles and a bit of thread maybe? A couple of ballons to provide pressure to the outermost "tanks"?

How about this experiment? You're trying to disprove conservation of angular momentum.

[Nao]

I like your non-asparagus design. It achieves much of the advantages of asparagus staging by thinking outside the box. It doesn't surprise me that your "lazy" asparagus version of it doesn't show much improvement, but that's because the design wasn't made with asparagus in mind. By having three mainsails and three skippers, you're locked into a three branch, two stage design, and that's not particularly efficient.

It's true that the rocket was designed to work without asparagus first. But I don't think number of stages changes much here, especially when it is the asparagus that gains advantage of lower number of stages. (low number of stages, more Dv per stage, more fuel tank mass to tow for the non asparagus version).

The idea behind my design is just exploiting each of the different propulsion system to its full potential. Engines are decoupled before their fuel tank mass becomes too bit to affect performance in a big way. This chart (idk who made it so can't give credit ) shows correlation of fuel mass to Dv for each engine. If we want to use the engine over long burns for maximum Dv gain then yes, asparagus delivers great performance. But for engines with very high ISP or designs with low burn time (low Dv requirement) does not benefit from asparagus as much. I dont think of this as gimmicky or thinking out of the box but just using the tools available to their greatest potential. That's why i used the term lazy - as you can't go wrong strapping another stage on asparagus ship, but designing similar non asparagus one is much harder, but doable half of the time.

Going further, in my opinion, one of the reasons fo Falcon Heavy to use fuel cross-feed is because they use low ISP engines (much lower than for example Space Shuttle's engines). So even thou they have super light fuel tank, the mass fraction of it becomes big enough to warrant investment into cross-feed to increase performance.

Also, for this challenge: Payload Fraction Challenge, I've just created an ascent rocket, that delivers payload to orbit at 18% mass fraction and uses 4 stages, i would call that efficient, and it doesn't use any fuel transfer method.

[WafflesToo]

How about this experiment? You're trying to disprove conservation of angular momentum.

No need to be terse. And we're talking about which condition satisfies the conservation of momentum. I fail to see how you can move material around inside the machine in one direction without imparting movement on the rocket in the opposite direction.

[numerobis]

No need to be terse.

Well, brevity *is* the soul of wit and all that. I'm not sure how to explain conservation of angular momentum using more words. If you draw fuel from the outside to the inside, no matter the path taken there, the rocket must have the same angular momentum when you start as when you end. That means you can speed up a roll that already exists (because you've redistributed the mass inwards), but you can't create a new roll.

The complication is that the rocket isn't a closed system: you're venting spent fuel. However, in order to build up angular momentum in the rocket, you would need to eject the spent fuel out the side a bit. A good nozzle is designed instead to have the spent fuel all go straight out the back, since anything else wastes propellent.

[WafflesToo]

Well, brevity *is* the soul of wit and all that. I'm not sure how to explain conservation of angular momentum using more words. If you draw fuel from the outside to the inside, no matter the path taken there, the rocket must have the same angular momentum when you start as when you end. That means you can speed up a roll that already exists (because you've redistributed the mass inwards), but you can't create a new roll.

The complication is that the rocket isn't a closed system: you're venting spent fuel. However, in order to build up angular momentum in the rocket, you would need to eject the spent fuel out the side a bit. A good nozzle is designed instead to have the spent fuel all go straight out the back, since anything else wastes propellent.

You may have been breif but you were hardly consise. Outside of a vague description of an experiment involving effectively pendulum weights revolving around a common axsii; lacking conditions for the actual experiment or any published results. I fav to see how that link supports your statement.

What I'm seeing is two parts if a system; a storage tank and the liquid inside. The storage tank is suspended and free to move. A pump is applying force on the liquid to rotate it in a clockwise direction inside the tank. This pump just be attached to the tank. IAW Newton's third law, if the pump is applying N force on the fluid the fluid must apply -N force on the pump forcing the tank to rotate in a counter-clockwise direction.

If I'm mistaken I will gladly accept correction, but I will not accept being insulted and told, "because I / person said so".

Edited October 29, 2013 by WafflesToo

[Nao]

...and then the high speed liquid hits a bend in a tube that tells it to move downward toward combustion chamber, we get back all the rotational momentum and we even get some thrust out of the moving fluid!

[WafflesToo]

...and then the high speed liquid hits a bend in a tube that tells it to move downward toward combustion chamber, we get back all the rotational momentum and we even get some thrust out of the moving fluid!

And that is the piece I was missing.

The funny bit is I came to that conclusion this morning and if you hadn't been rude about it I would've recanted at about 9am my time.

[Nao]

Glad to help. I guess in real rockets there are some things that may make the rocket spin, like the bell nozzle cooling exhaust or something like drains etc. The newest Falcon 9 did suffer uncontrollable rotation problem when returning to earth... But i guess thats all out of the scope of the game.