Wasn't Asparagus Staging Supposed to be a Good Thing?

[Semnae]

I built 3 rockets with some sciency stuff at the top and tested them. Here are the results:

5 vertical X200-16 tanks with a skipper on the bottom - 652139m
3 vertical tanks with 2 staged tanks off to the sides and 3 skippers - 1231577m
Same setup as above with fuel ducts and staged like in asparagus staging - 1156787m

I keep reading about how awesome asparagus staging is, but asparagus staging seems to make rockets in the game worse, not better. What's going on?

[Semnae]

Just to be sure, I did a fourth experiment. This one had one center tank and two tanks on each side. It was also set up like asparagus staging. This one did even worse. 702381m.

[Ottomic]

Well, your vehicle seems to be losing delta-v as it loses weight. The only reason I could see for that is that you are discarding fuel along with the cans.

You made sure the parts you are jettisoning are empty?

[Unconventional]

http://wiki.kerbalspaceprogram.com/wiki/Asparagus_staging

look here but it has more detail

[ChillestBro]

Asparagus staging works very well for efficient use of fuel, but doesn't always mean you can get out farther with it in use. If set up correctly and precisely, you can create rockets that use asparagus staging that keep a constant(ish) TWR and get the most Delta-v out of the boosters and fuel on board.

[GRockGames]

As much as I love Asparagus Staging, I have to admit that the profits are marginal if it's not used properly. Asparagus Staging is a perfect idea in theory, what with the fuel being most efficiently used from engine to engine, but the more you use it, the less profit you get. So don't make an entire rocket where the final stage runs the whole time, and the rocket's a pancake. HOWEVER, if used conservatively, Asparagus Staging can give you pretty good profit on fuel over a couple of stages, enough to give you that extra Delta-V to get past the atmosphere, or perform those costly orbital maneuvers.

[Ottomic]

Also, putting a smaller rocket in the middle *and* cans you're shedding will make your asparagus more effective, since you'll lighten up more along your ascent.

[DaSkippa]

Asp staging is great for lifting stupidly unrealistic payloads
http://steamcommunity.com/sharedfiles/filedetails/?id=251922683
or going for eve landers/jool divers. For rational types of payloads/gravity/atmo thickness however the benifits are more marginal. Asp staging generaly gets better/ more efficient the bigger you go at the price of parts count. With the new NASA/SLS parts realistic mission types & payloads no longer benifit that much from asparagus.

[Xcorps]

You're testing methods are flawed. You don't test rockets based on how far up they go. You test them based on how much payload they lift.

Sciency stuff is not your payload.

Build a 50 ton payload and lift it with ONE rocket.
Then lift it with TWO rockets.
Then lift it with THREE rockets.
Then lift it with four rockets.
Then lift it with five rockets.
Then lift it with six rockets.
Then lift it with seven rockets.
Then lift it with eight rockets.

Then repeat with asparagus staging. You will see that as you leave atmosphere, your remaining DV will be higher than with onion or standard staging.

You build rockets with the intention of putting them somewhere, not to see how far they fly with some sciency stuff attached to the up goer at the front of the space car.

[El Rushbo]

Don't forget moar boosters.
http://steamcommunity.com/sharedfiles/filedetails/?id=245468420
http://steamcommunity.com/sharedfiles/filedetails/?id=245470202
http://steamcommunity.com/sharedfiles/filedetails/?id=245468503
This rig actually used onion staging rather than asparagus. It was built to test the excess that can be applied with the new NASA engines.

[The_Mell]

Messaggio originale di TWC_Xcorps:

You're testing methods are flawed. You don't test rockets based on how far up they go. You test them based on how much payload they lift.

Sciency stuff is not your payload.

Build a 50 ton payload and lift it with ONE rocket.
Then lift it with TWO rockets.
Then lift it with THREE rockets.
Then lift it with four rockets.
Then lift it with five rockets.
Then lift it with six rockets.
Then lift it with seven rockets.
Then lift it with eight rockets.

Then repeat with asparagus staging. You will see that as you leave atmosphere, your remaining DV will be higher than with onion or standard staging.

You build rockets with the intention of putting them somewhere, not to see how far they fly with some sciency stuff attached to the up goer at the front of the space car.

Where is the difference between a payload of 50 t and x tons of science equipment?
What is it while looking at delta v, the ability to do maneuvers, and an actual maneuver like gaining altitude?
Why is it inacceptable to put a space car with sciency stuff attached to it on a parabolic path with max possible distance to ground?

The problem with staging is not an easy thing. There are quite some variables.
2 of them are TWR and drag of your start stage. With a too low ratio of thrust to weight, your rockets acceleration will be too low and gravity will drain your fuel constantly. Think about a worst case scenario where TWR is below 1 and it can only lift of after it lost some weight by burning fuel. On the other hand increasing speed leads to increasing loss by drag - especially at low altitude.


The tests of Semnae show this - have a look at his runs 2 (without fuel lines) and 3 (with fuel lines):
At launch both TWRs are equal but on 2 the 'booster tanks' are empty earlier. Therefore the vessel loses not only weight but 2/3 of its thrust by separating and the center fuel tanks are full and heavy resulting in a bad TWR for this second stage.
With 3 there is a longer use of all three engines and therefore a better TWR. And when the boosters are gone, TWR of run3-second-stage is just at level like run2-second-stage after emptying 1/3 of its fuel capacity.
So the question is how do run2-first-stage-longer-high-TWR compare to run3-second-stage-low-TWR.

And i guess run 4 has a miserable result because those 'double booster' simply result in a too long three engine high TWR time so that speed raises too high and drag becomes relevant...

[DaSkippa]

Messaggio originale di The_Mell:

Messaggio originale di TWC_Xcorps:

You're testing methods are flawed. You don't test rockets based on how far up they go. You test them based on how much payload they lift.

Sciency stuff is not your payload.

Build a 50 ton payload and lift it with ONE rocket.
Then lift it with TWO rockets.
Then lift it with THREE rockets.
Then lift it with four rockets.
Then lift it with five rockets.
Then lift it with six rockets.
Then lift it with seven rockets.
Then lift it with eight rockets.

Then repeat with asparagus staging. You will see that as you leave atmosphere, your remaining DV will be higher than with onion or standard staging.

You build rockets with the intention of putting them somewhere, not to see how far they fly with some sciency stuff attached to the up goer at the front of the space car.

Where is the difference between a payload of 50 t and x tons of science equipment?
What is it while looking at delta v, the ability to do maneuvers, and an actual maneuver like gaining altitude?
Why is it inacceptable to put a space car with sciency stuff attached to it on a parabolic path with max possible distance to ground?

The problem with staging is not an easy thing. There are quite some variables.
2 of them are TWR and drag of your start stage. With a too low ratio of thrust to weight, your rockets acceleration will be too low and gravity will drain your fuel constantly. Think about a worst case scenario where TWR is below 1 and it can only lift of after it lost some weight by burning fuel. On the other hand increasing speed leads to increasing loss by drag - especially at low altitude.


The tests of Semnae show this - have a look at his runs 2 (without fuel lines) and 3 (with fuel lines):
At launch both TWRs are equal but on 2 the 'booster tanks' are empty earlier. Therefore the vessel loses not only weight but 2/3 of its thrust by separating and the center fuel tanks are full and heavy resulting in a bad TWR for this second stage.
With 3 there is a longer use of all three engines and therefore a better TWR. And when the boosters are gone, TWR of run3-second-stage is just at level like run2-second-stage after emptying 1/3 of its fuel capacity.
So the question is how do run2-first-stage-longer-high-TWR compare to run3-second-stage-low-TWR.

And i guess run 4 has a miserable result because those 'double booster' simply result in a too long three engine high TWR time so that speed raises too high and drag becomes relevant...

Ok I think I see your problem. Your conception apears(unless I misunderstood) to be that "distance from ground" matters. The only thing that is relevant to orbital manuevers/interplanetary transfers is dV and to a lessser extent TWR. The benefit T Asp staging vs other types is that it it will always provide more end dV for obital manuevers than an onion or SSTO for a given payload size, obital altitude. With a payload of <100 tons the benifit is not as pronounced. For massier payloads the effficency of Asp becomes more and more apparent as paylod mass increases.

This is why SSTO's and in some cases oninons hit point of vanishing returns when they can no longer lift payload + fuel budget MUCH earlier than asparagus.

[Gertjan]

indeed, 'distance from ground' isn't a good measure of rocket design, you are better off measuring the % of starting fuel (or dV, if you use kerbal engineer or mechjeb to calculate it) left once you hit a certain altitude.
you'll see that asparagus is a lit better.
if i use my basic launcher in different fuel-transfer modes for the same launch profile (mechjeb-piloted to keep human error out of the comparison), there is a lot of difference.
if i use no crossfeed, just the boosters first, i can barely get 40 tons in 80km orbit, union crossfeed (all engines fire, all boosters directly into the main tank) gets me 50 tons in 100km, easy, and asparagus gets me 90 tons (max weight off the pad) into 200km orbit without even needing the main tanks, many interplanitary missions launched with that thing get their initial 'kick' from the launchers main engine; it has enough dV to get that 90 tons in orbit around moho, with just the launcher itself, while union staging doesn't even get that 90 tons in orbit around kerbin.

there's your difference ;)

[DaSkippa]

See if the following clarifies it some:
These lifted a 100.63 ton payload
Modified SSTO with SRB assists (so not quite SSTO :D)
http://steamcommunity.com/sharedfiles/filedetails/?id=263452580
http://steamcommunity.com/sharedfiles/filedetails/?id=263452654
http://steamcommunity.com/sharedfiles/filedetails/?id=263452672

Modified Onion
http://steamcommunity.com/sharedfiles/filedetails/?id=263452717
http://steamcommunity.com/sharedfiles/filedetails/?id=263452789
http://steamcommunity.com/sharedfiles/filedetails/?id=263452809

Mini Asparagus technicilly this doesn't even qualify as Asparagus as it only has 2 "stalks" wyhole lotta onion in that asparagus. but was as small as I could get to derive similar operating characteristics/equiptment/final dV to the SSTO
http://steamcommunity.com/sharedfiles/filedetails/?id=263452844
http://steamcommunity.com/sharedfiles/filedetails/?id=263452881
http://steamcommunity.com/sharedfiles/filedetails/?id=263452899

The SSTO burned a CRAP ton more fuel than either the Onion of mini asparagus
For moderate payload sizes like this the onion shows it's legs 500+dV, however some of that was simply due to not going up against a true asparagus stalker( I think I flubbed the grav turn as well). If I felt like spending an hour designing a 200+ton payload SSTO I could show off better how SSTO's Onions Asparagus's perform with bigger payloads. But the above should give you an idea
As an extreme varient, you wont find any SSTO's and perishing few onions doing this:
http://steamcommunity.com/sharedfiles/filedetails/?id=252104705
This thing had over 12k Atmo dV 25k Vac dV I think

[DaSkippa]

Above I constraned my self to give the various types similar operating characteristics to show fuel use and launch weight, while ending up with a similar final dV and still using almost identicle equiptement.
Below shows the differnce when the systems are used correctly using the EXACT same vehicle with the only variation being staging events and fuel flow.

all vehicles used a 61ton Payload
True SSTO 7.1k dV after circle
http://steamcommunity.com/sharedfiles/filedetails/?id=263495222
http://steamcommunity.com/sharedfiles/filedetails/?id=263495263

True Onion 8.8kdV after circle
http://steamcommunity.com/sharedfiles/filedetails/?id=263501535
http://steamcommunity.com/sharedfiles/filedetails/?id=263501560
http://steamcommunity.com/sharedfiles/filedetails/?id=263501598

True Asparagus 9.6dV after circle
http://steamcommunity.com/sharedfiles/filedetails/?id=263495472
http://steamcommunity.com/sharedfiles/filedetails/?id=263495496
http://steamcommunity.com/sharedfiles/filedetails/?id=263495554
http://steamcommunity.com/sharedfiles/filedetails/?id=263495588
http://steamcommunity.com/sharedfiles/filedetails/?id=263495612

As you see there is a slight :D difference in final dV, heck the difference between the SSTO and the Asparagus is a free one way trip to most planets in the solar system, even the difference vs the onion is the better part of a Mun insertion. Now I may not be a god of gravity turns but even on my worst day I'm not gonna flub it and loose 700dV(Onion) or even worse 2.5kdV(SSTO)

[Dryd]

While people are happily making huge posts I will just say this;

WIth nearly 200 hours in KSP and still going strong by far the most economical way to reach orbit is a asperagus staged system (although currently im being lazy & having an onion of Liquid fueled boosters to get me the first 10km up, then switching to Asp).

The other things to bare in mind are the angles, start & end points of gravity turns. The is a great python script out there for calculating this for you.