Asparagus Staging in Real Life?

[CalculusWarrior]

I was launching yet another heavy payload into orbit with my favourite asparagus-staged rocket, and I was curious to know why there aren't any (that I know of) asparagus-staged rockets in the real world. Are they only more efficient in KSP than real life, or are they too expensive/complicated/dangerous to be used by any major space agency?

[Sleipnir]

I was launching yet another heavy payload into orbit with my favourite asparagus-staged rocket, and I was curious to know why there aren't any (that I know of) asparagus-staged rockets in the real world. Are they only more efficient in KSP than real life, or are they too expensive/complicated/dangerous to be used by any major space agency?

As far as I know Fuel transfers (and therefore "Asparagus" designs) are really really complicated and hard to do IRL, and as of right now only one rocket does it and that is the new NASA rocket SLS ( http://en.wikipedia.org/wiki/Space_Launch_System )

if I am correct

[AlternNocturn]

Too complicated, and side-mounted boosters aren't normally used due to added drag I believe.

[DerekL1963]

I was launching yet another heavy payload into orbit with my favourite asparagus-staged rocket, and I was curious to know why there aren't any (that I know of) asparagus-staged rockets in the real world. Are they only more efficient in KSP than real life, or are they too expensive/complicated/dangerous to be used by any major space agency?

Fuel transfer is complicated and difficult, and the associated pumps, piping, and couplings add complexity (things to go wrong) and weight. Also, there's considerable ram drag when the atmosphere tries to flow between the stages. Also supersonic and hypersonic flow can do funny things - forcing the stages apart at one speed while sucking them together at another, adding significant dynamic forces. Then there's the issue of all those interacting shockwaves....

[RRoan]

As far as I know Fuel transfers (and therefore "Asparagus" designs) are really really complicated and hard to do IRL, and as of right now only one rocket does it and that is the new NASA rocket SLS ( http://en.wikipedia.org/wiki/Space_Launch_System )

if I am correct

you are incorrect

the falcon heavy will come with crossfeed

[Ession]

The Falcon Heavy will do some fuel cross-feeding as well.

http://www.spacex.com/falcon_heavy.php

[yongedevil]

I don't know if there are any currently flying rockets that use fuel transfer; however, check out the wikipedia article on the Falcon Heavy rocket being developed by Space X.

Engines from all three cores ignite at launch, but until fuel runs out in the booster cores, the main core uses little or none of its own propellant. Falcon Heavy is being designed with a unique propellant crossfeed capability, where fuel and oxidizer are fed to power most of the engines on the center core from the two side cores, up until the side cores are near empty and ready for the first separation event,

So there may not be any rockets using asparagus staging right now, but there will be.

[paleorob]

It is interesting that people tend to poo-poo asparagus designs for the real world since nothing currently flying uses it. I wonder if the KSP community has actually independently invented something new that has real-world utility (like the Falcon Heavy) that traditional "in the box" aerospace engineers had not previously though of.

[astropapi1]

Well, they had a lot of trouble for the furl teansfer between the orange tank and the shuttle. Now imagine the process of creating an asparagus staged monster like the ones we use.

And that's just one of the problems...

[NovaSilisko]

Classic KSP-style "asparagus" staging (6-8 boosters, dropping away in pairs) is also impractical IRL due to the number of staging events - ideally you want to have as few as possible, so there's less risk of things going wrong.

Besides that, it's quite simply a case of "easier said than done".

[Temstar]

Fuel crossfeeding is a very old concept, in fact Mikhail Tikhonravov first came up and wrote about the idea in 1947. The concept is pretty simple though and many people since Tikhonravov have interdependently rediscovered the idea. For example Chelomei came upon the idea again when he designed the UR-700 rocket as an alternative to the N1 moonshot:

(on the top left is UR-700 at lift off, in the middle is it again with the outer ring of asparagus boosters jettisoned)

but it's never been put into practice at this point, though as others have mentioned Falcon Heavy will have a go at it.

The thing that makes it so overwhelming popular is because the engines in KSP are at least 4 times heavier than real life rocket engines for the same thrust, and fuel tanks in KSP are 10 times heavier than real life tanks for the same capacity. Because engines and tanks are so heavy in KSP the advantage of getting rid of them early becomes huge. In real life rocket hardware make up a tiny fraction of the fully fuelled weight of the rocket so the benefit of getting rid of them early is not nearly as pronounced.

[Eric S]

There's several theories as to why asparagus staging isn't used in real life.

The ones that I think are real are:

1) Too many parts, and unlike the Saturn V or Falcon 9, if the wrong fuel pump were to fail (a common problem from what I've read on causes for failed launches), the mission would have to abort unless they had redundant pumps. The Saturn V was able to launch on multiple occasions despite engine failures, and the Falcon 9s have the same ability, though I don't know if any launches have had engine failures yet.

2) It wouldn't provide as much benefit. The reason asparagus staging works is because you're discarding fuel tanks and engines as soon as possible. Real engines and tanks weigh about a quarter what they do in KSP for the same thrust or tank volume, so the delta-V benefits are significantly reduced. (I haven't done the math on this, but I plan on doing the math to verify this).

[magnemoe]

There's several theories as to why asparagus staging isn't used in real life.

The ones that I think are real are:

1) Too many parts, and unlike the Saturn V or Falcon 9, if the wrong fuel pump were to fail (a common problem from what I've read on causes for failed launches), the mission would have to abort unless they had redundant pumps. The Saturn V was able to launch on multiple occasions despite engine failures, and the Falcon 9s have the same ability, though I don't know if any launches have had engine failures yet.

2) It wouldn't provide as much benefit. The reason asparagus staging works is because you're discarding fuel tanks and engines as soon as possible. Real engines and tanks weigh about a quarter what they do in KSP for the same thrust or tank volume, so the delta-V benefits are significantly reduced. (I haven't done the math on this, but I plan on doing the math to verify this).

Falcon 9 was able to launch with one engine out once.

Falcon heavy will fuel 3 of it main engines with fuel from boosters. should still have engine out while crossfeed however it complicate stuff.

Engine and dry weight is main reason why its so useful in KSP in short you have low twr. Try to put something like an orange tank in orbit and you find that an serial stacked rocket will be far heavier.

Parallel stacking in real world is mostly used as an cheap way to get more cargo capacity on an rocket.

In real world you can also use different trust on boosters and main stage, launch something with mechjeb with plenty of solid boosters and watch mechjeb pull the throttle far back to reduce drag loss. Now think if you could do this with liquid boosters.

[Crush]

and side-mounted boosters aren't normally used due to added drag I believe.

You mean except for the Ariane V, the Soyouz, almost all members of the Delta family, the Proton, the retired Space Shuttle, the SLS, the Falcon Heavy or pretty much every heavy lifter used or designed in this century?

Edited May 10, 2013 by Crush

[Brotoro]

You mean except for the Ariane V, the Soyouz, the Delta IV Heavy (and most Medium variants), the Proton, the SLS, the Falcon Heavy or pretty much every heavy lifter used in this century?

The Proton launch vehicle does not use side boosters. The center tank holds the oxidizer and the surrounding tanks hold the fuel -- they are not boosters that separate from the stage.

[Crush]

The Proton launch vehicle does not use side boosters. The center tank holds the oxidizer and the surrounding tanks hold the fuel -- they are not boosters that separate from the stage.

Yes, but we were talking about aerodynamics.

[magnemoe]

Yes, but we were talking about aerodynamics.

Yes and it make it interesting that they selected this design, it probably made the stage lighter and cheaper with the higher drag less of an issue.

[Temstar]

The shape of the Proton was selected to facilitate rail transport. Since the rockets are going to be built in Moscow and transported to Baikonur by rail for finally assembly each individual piece much fit within existing railway wagons and platforms. What Chelomei did was he built a centre core with a single large tank used for oxidiser. This tank was designed with the largest possible diameter that could be transported by rail. Then once it arrived at Baikonur it's mated with a ring of segments each holding a smaller fuel tank and engine. Thus you then have a large first stage with all components rail-portable yet require only minimal assembly at Baikonur.

And yes if you're think Proton kind of looks a bit like the UR-700 I posted above, pat yourself on the shoulder - Proton is actually UR-500. Chelomei designed his rockets so that both UR-500 and UR-700 shared the "maximum railway diameter" tanks. Only difference is UR-500 would use one in its first stage while UR-700 would use 18 of those tanks in the first two asparagus stages and a UR-500 first stage as its third stage.

Edited May 10, 2013 by Temstar

[geb]

One set of fuel crossfeed pipes is tricky to do, but it can be done, and has been. The Falcon Heavy fuel crossfeed system is pretty much the same as the system the space shuttle used to use for moving fuel from its external tank.

One pair of asparagus staged boosters can be done.

The problem is that as you add more boosters and more engines, the fuel flow rate has to increase. If you have two pairs of boosters, all the fuel pumps and pipes have to be more than twice as big. If you have three pairs, each fuel crossfeed system would need to be about four times as big, and you need four sets of pipes and pumps, so more than sixteen times as much huge heavy junk bolted to your vehicle. It's not just adding a little yellow tube in reality, since you need to be able to handle tonnes per second of liquid under high pressure, and you need to do it near perfectly smoothly.

[rosenkranz]

one supposes that if you really wanted to see the difference, make a clean copy of ksp and then mod the cfg files for the tanks and reduce their dry weight by a factor of 10 and reduce all engine masses by a factor of 4. then do some testing of your own.

really, about the only thing you couldn't simulate is mechanical failures. But, otherwise, the results might be interesting.

[MK3424]

The Saturn V was able to launch on multiple occasions despite engine failures, and the Falcon 9s have the same ability, though I don't know if any launches have had engine failures yet...

Well it happened during the apollo 13 mission that during the 2nd stage burn the center stage shut down so that the spacecraft adjusted his ascent to compensate for the loss.

[Kerba Fett]

Have they even tried using a yellow pipe with arrows painted on it?

NASA's always trying to make stuff seem complicated to keep their huge budgets.

[NeoMorph]

The Saturn V was able to launch on multiple occasions despite engine failures, and the Falcon 9s have the same ability, though I don't know if any launches have had engine failures yet.

Yup... They had a pretty big fail on the ISS resupply mission and the thing kept on trucking.

http://motherboard.vice.com/blog/spacex-s-non-fatal-failure

[Xeldrak]

also: conservation on momentum - if tons of fuel are pumped clockwise around the rocket - the rocket will start to roll couterclockwise

[SDIR]

It's too bad things don't work like that in real life. But sometimes simplicity is really the best option.