Revisiting an old, simple one: The 10 fuel tank challenge.

[Ziff]

Two 1/2's equals 1

The limitations:

- You have 10 of the FL-T400 fuel tanks, plus an unlimited number of all other parts, subject to the other limitations.

- Stock Parts only.

- No Solid Boosters or RCS tanks, and no fuel tanks other than those 10.

- Continuous full-throttle burn. Obviously, we'll have to take you at your word on this one, but this is both to avoid the fuel consumption bug in 0.16 and to keep Jeb happy.

- Anything goes as far as staging, angling to take advantage of orbital speed, etc.

- post a screenshot showing your craft's altitude and speed at burnout.

I dunno, it seemed pretty specific to me. 10 FL-T400 tanks, no half tanks.

[trekkie_]

Two 1/2's equals 1

perhaps you didn't pay attention. the point is by having 2 half tanks, he was able to add an extra engine and have weight balance.....had he used the regular full tanks, he would have to of taken an entire fuel tank from the center mass in order to add 2 extra engines....or make due with less engines/another design.

the point of using 10 of the same fuel tanks is not only being limited by fuel....but also being limited in how you can design your rocket and what stages get X amount of fuel, how the weight is balanced, etc. for example, to add 2 side engines with 2 full size fuel tanks to attach them to, he would of for example, had to of taken a full tank off of the 20 thrust lv909, which would have severely limited his distance later on in the launch. (if we didn't follow strict rules, we could just use any tank as long as it came up to the equivalent amount of fuel, which would give a severely mixed bag of results) after all it's called the 10 tank challenge, not the 9 normal tank and 2 half tank challenge.

not to mention I timed the amount of the time it would take to burn through all of his fuel at full throttle the entire flight with immediate decoupling.....which took about 14:56 ......however he ran out of fuel at 15:12, which is a HUGE discrepancy. so either he cheated by using a different design than he showed, or an extra booster, or didn't decouple/coasted for well over 16 seconds at some point, which is unacceptable. either way he didn't follow the rules in multiple instances. what's the point of participating in a challenge if you're not going to follow the rules of it?!

so in conclusion he broke at least 2 rules:

1) he didn't use the right tanks, which allowed him to use a design that he otherwise couldn't without taking fuel from other stages

2) he coasted with engines off for at least 16 seconds! (or throttled below maximum thrust)

I'm guessing he coasted when he decoupled the first stage. 16 seconds of coasting before activating a second stage is obviously unacceptable. his speed is also FAR more than it should be, so he could have used some solid fuel boosters too, or it's a result of his coasting. either way, his flight time is well above the time it would take to burn through all the fuel with his design in the allotted time.

the math simply doesn't lie.

Edited August 11, 2012 by trekkie_

[TheDarkStar]

Neither point should be an issue.

1. Although he used 9 tanks + 2x1/2, the challenge creator said it was allowed, and it actually adds to drag.

2. He used the aerospike, which has constant fuel usage, and two gimballing engines, whose specific impulse changes as you get higher in the atmosphere (they need less fuel the less air there is).

[semininja]

2) There is a bug which scales fuel consumption by the square of the throttle, which means that any engine gets more efficient as you decrease throttle. That's definitely cheating, regardless of the first point.

Edited August 11, 2012 by semininja

[trekkie_]

Neither point should be an issue.

1. Although he used 9 tanks + 2x1/2, the challenge creator said it was allowed, and it actually adds to drag.

2. He used the aerospike, which has constant fuel usage, and two gimballing engines, whose specific impulse changes as you get higher in the atmosphere (they need less fuel the less air there is).

you obviously don't understand the implications.

1. drag doesn't affect distance or speed all that much, especially only 0.2 extra of it. drag is meaningless in a vacuum, and even further, at a 100,000,000m journey, only 10% of of the total flight distance suffers any of that miniscule 0.2 lag anyways.

however, the extra configuration options from using 2 half tanks changes everything alot. it allows him to add 2 side engines in a first stage without having to take any fuel from the second stage. the second stage using the 20 thrust power lv909 engine heavily depends on 2 full tanks to reach distances. it consumes fuel very slowly, but goes very far when on an escape trajectory.

2. this is all meaningless since I've already proven he couldn't have possibly gotten that as far as he did with his design, without cheating. he only has enough fuel to burn at full throttle for 14 minutes and 56 seconds, taking into consideration all of his engine types. his flight time was 15 minutes and 12 seconds. this is a discrepancy that outright proves he wasn't burning his engines at all for 16 seconds at some point in the flight. that's 16 extra seconds he shouldn't have, on top of two half tanks he shouldn't have, which drastically alters the results he would have had if he followed the rules. as I said before, the math doesn't lie.

[tjoreilly]

Let's be sure to keep this discussion civil, friends.

[Ziff]

Neither point should be an issue.

1. Although he used 9 tanks + 2x1/2, the challenge creator said it was allowed, and it actually adds to drag.

2. He used the aerospike, which has constant fuel usage, and two gimballing engines, whose specific impulse changes as you get higher in the atmosphere (they need less fuel the less air there is).

Actually, Khyron said -not- to use the half tanks.

Likewise, using the larger tanks would give you a free ride by reducing overall drag during early flight. Because it would have different results, I'd prefer to keep this challenge to the FL-T400's only.

Not sure why this keeps coming up. It is a 10 tank challenge limited to the FL-T400's. He also said using Jet part's would be counted separately. So let's get back on track with this challenge.

[khyron42]

Kerb and Darkstar and Ziff, I think you missed the testing I performed earlier in the thread after the part Ziff quoted. There appears to be absolutely no drag difference or weight difference between tanks, since it seems like the drag rating is a coefficient that gets applied to the mass of the part.

Hmm... the drag thing requires testing for confirmation then. Best test: fly to 10 km altitude with identical designs with the only difference being the fuel tanks (flying at full throttle.) Note time of reaching 10 km and speed at that mark. Any speed/time differences will be due to drag differences.

Design: pod, ASAS, 5 FL-T400 tanks, LV-T45 small engine. 1:29 time to 10 km, 238.9 m/s speed.

Same design with 10 FL-T200 tanks. 1:29 time to 10 km, 238.3 m/s speed.

With 1 FL-T16 and 1 FL-T400: 1:29 time to 10 km, 239.2 m/s speed.

The small differences were just a measurement issue - I was hitting escape to pause the game when I crossed 10 km. Cool, I learned something new about the game today!

So I guess any (non-jet) stock tank combination is okay as long as the total fuel is 4000. The jet tanks are horribly unbalanced compared with the four "normal" tanks.

However, I'll have to try simplemunrocket's design and see what's up with that. He may have coasted, or he may have burned just the outer two during stage one instead of both them and the aerospike. Your attempt to refly it burns all three at once, but his doesn't show that setup in the staging.

Edited August 11, 2012 by khyron42

[Ziff]

Kerb and Darkstar and Ziff, I think you missed the testing I performed earlier in the thread after the part Ziff quoted. There appears to be absolutely no drag difference or weight difference between tanks, since it seems like the drag rating is a coefficient that gets applied to the mass of the part.

Thank you for the clarification. Can you edit the OP so it is obvious to future participants? Thanks.

[trekkie_]

Kerb and Darkstar and Ziff, I think you missed the testing I performed earlier in the thread after the part Ziff quoted. There appears to be absolutely no drag difference or weight difference between tanks, since it seems like the drag rating is a coefficient that gets applied to the mass of the part.

However, I'll have to try simplemunrocket's design and see what's up with that. He may have coasted, or he may have burned just the outer two during stage one instead of both them and the aerospike. Your attempt to refly it burns all three at once, but his doesn't show that setup in the staging.

I tried both configurations, one with the 2 side engines burning first, and another with all engines burning from the start....the latter actually got the 916K meter distance, the former got only 760K meters or so. like I said before, no matter what his configuration couldn't have gotten him as far as he stated. that's why I said he either used boosters or coasted or both. either way he couldn't have possibly reached his stated distance no matter what with the ship he showed.

[Bluejayek]

Is it cheating to get out and push with your kerbal after burnout?

4.95MJ/kg without this. Staging was messed up though, and I have a terrible T/W ratio, so I think I can do better.

352km altitude, 4161m/s.

8:10 flight time

Edited August 12, 2012 by Bluejayek

[trekkie_]

I built one very similar to that one, the 20 thrust lv909's aren't worth it due to their weight and lack of thrust, even when you're able to decouple the tanks. in fact, the extra decouplers add drag and weigh you down too. think about it, you have a whole bunch of engines with 1 tank each that will all run out at the same time. which means you're going to have to decouple them all at the same time anyways, so multiple decouplings are useless.

also, there is no reason to share fuel between them if they both have a single tank each and the same engines....they'll still burn fuel at the same rate...and the fuel lines add even more weight and drag. those 20 thrust engines weigh more than a 1200 thrust lv909 combined and only produce 160 thrust combined while incurring 8 mass extra weight. basically they produce less thrust than your main engine and weigh much more, which negates their slow fuel usage. and you're burning them at take off which is when you need either the most thrust and more fuel for the higher thrust engines to get momentum going. if you rework your design a bit I'm sure you could push it further.

the best design is that which decouples tanks as they're used up, one at a time, otherwise you're carrying all that extra weight with you.

for example, if you took all of the outer 20 thrust engines off, and connected them via fuel line to your main engine; then stage them to where the engine feeds off of them one at a time (and the tank it's connected to for last) while also staging to decouple them as they're used up, you'll lose a lot of weight and drag. also, so far on your final stage with the center 20 thrust engine, it's best to give those at least 2 full fuel tanks to themselves if you're trying to go for distance.

Edited August 12, 2012 by trekkie_

[Optical9090]

Attempting this challenge.

Final velocity: 5731 m/s

Final height: 2772 km

Someone please help me with the maths because i'm getting 19.something on this, i might be slightly off.

at last screenshot i was half a second from burnout, so numbers might have been a tad higher if i went the distance, don't matter.

[simplemunrockets]

I tried both configurations, one with the 2 side engines burning first, and another with all engines burning from the start....the latter actually got the 916K meter distance, the former got only 760K meters or so. like I said before, no matter what his configuration couldn't have gotten him as far as he stated. that's why I said he either used boosters or coasted or both. either way he couldn't have possibly reached his stated distance no matter what with the ship he showed.

I actually exploited the rotation of Kerbin and did a sort of outward spiral.

[trekkie_]

broke the (my) old altitude record (the legitimate one that followed the rules) by just a smidgeon with a wacky, inefficient but sneaky design...

now here's the trick, the basic jet engines use very little fuel but provide a lot of thrust, even with 6 of them and the extra weight such as the nacelles and the ram air intakes. anyways, with these mounted, they will bring you to around 6-7K meters before they stall out, because that's too high for them to operate enough to give you forward momentum (much more efficient than the aerospike except it doesn't operate in all altitudes).

so once I reach that height, I jettison them. the pay off is using very little initial fuel to steal several thousand meters while also getting a free ~65m/s at the same time. this is essentially like taking off at several thousand meters instead of on the launchpad, for the cost of less than a quarter tank. using this method should be able to benefit every other submissions performance by a large margin.

since the design was woefully inefficient, I expect to be able to break this distance record too. but it did get MUCH farther than it would have on its own. I forget what the distance was of the rocket without the basic jet engines, but I'd say it got anywhere from 2-5 times as far, definitely 2x at the very least.

EDIT:

yep, broke it again....by a lot, with my original altitude record holding design. virtually doubled the distance, thanks to the basic jet engine. these things are soo efficient I don't think I'll ever launch a ship again without adding them into the mix for the initial launch stage, they save a tremendous amount of fuel.

EDIT2:

BEHOLD my mighty efficiency! this is one for the record books.

might not be a rocket, but that's pretty dang far!

Edited August 12, 2012 by trekkie_

[Bluejayek]

I built one very similar to that one, the 20 thrust lv909's aren't worth it due to their weight and lack of thrust, even when you're able to decouple the tanks. in fact, the extra decouplers add drag and weigh you down too. think about it, you have a whole bunch of engines with 1 tank each that will all run out at the same time. which means you're going to have to decouple them all at the same time anyways, so multiple decouplings are useless.

a) The low thrust engines are worth it; I get further with then without.

The radial decouplers now weight very little, 0.025. While this was a serious concern in previous versions, it no longer is.

c) If you look at my screenshot, you can see in the staging that they are staged symetrically in pairs. All engines run off the fuel tanks of the first two, I eject them, and then repeat. They do NOT all run out at the same time.

In this thread you appear to be taking great pleasure in tearing down other peoples submissions for no good reason (e.g. calling somebody a liar and a cheater for having a flight time 16 seconds too long). If this is all you are going to do, I would appreciate it if you would stay out of this thread.

[khyron42]

Kerbtrek and Optical 9090 - sorry to do this, but when I revised the rules to allow different tank configurations, I also updated them to say no jet engines (or jet tanks; any rocket tank is fine as long as the craft totals 4000 fuel at launch.)

I made that edit shortly after Ziff asked me to clarify the initial post.

And - simplemunrockets, can you repeat that performance? The burnout time has been called into question, and I'm re-flying the flight pattern myself to see if it's right.

If people prefer, I can change it to really require only 10 of the 400-fuel tank, but I was surprised and pleased to see a better option get found, and wanted to leave it noted. What I'll do for now is separately note "10 tank results" vs. "4000 fuel results".

-----

Something absolutely bizarre must be going on. Using the exact design simplemunrockets and kerbtrek flew and got 14:56 and 15:12 burnout times with, I did an almost straight-upward launch and burned out at 16:51 - immediate staging after stage 1 and about a 2-second dead time between the aerospike and LV-909 stages. I'm doing this on a low-performance laptop right now, and I wonder if something in the new specific impulse system causes higher fuel efficiencies on laggy machines. It's also possible that it's just because the straight-up aerospike burn let me light my LV-909 at 68 km instead of lower the atmosphere, resulting in better specific impulse for the early part of the LV-909 burn - but it shouldn't be that huge of a difference!

Edited August 12, 2012 by khyron42

[Optical9090]

Ah, fair enough,

back to the drawingboard.

Btw, Aerospikes allowed? i noticed your own entry uses one and it's on the leaderboard for distance.

Edited August 12, 2012 by Optical9090

[trekkie_]

a) The low thrust engines are worth it; I get further with then without.

The radial decouplers now weight very little, 0.025. While this was a serious concern in previous versions, it no longer is.

c) If you look at my screenshot, you can see in the staging that they are staged symetrically in pairs. All engines run off the fuel tanks of the first two, I eject them, and then repeat. They do NOT all run out at the same time.

In this thread you appear to be taking great pleasure in tearing down other peoples submissions for no good reason (e.g. calling somebody a liar and a cheater for having a flight time 16 seconds too long). If this is all you are going to do, I would appreciate it if you would stay out of this thread.

a) honestly, you don't get further (nor faster) with it. maybe further than other less efficient designs you've tried, sure.

weigh little or not, over tens of thousands of meters, they do make a difference in distance and speed. I've had just 2 decouplers make as much as a 200K meter difference in a 1000KM journey.

even if you are jettisoning them in order from outer to inner, you're still forcing them to carry the extra weight of the inner engines which are dead weight until they're activated. basically think about how many of those 20 thrusts you have activated at once, and figure out a way to keep only those while jettisoning just the tanks. that way you're not carrying the extra weight of engines when you already have other engines providing the same thrust, only to throw them away, while still carrying their weight and drag twice fold in previous stages....get it?

"In this thread you appear to be taking great pleasure in tearing down other peoples submissions for no good reason (e.g. calling somebody a liar and a cheater for having a flight time 16 seconds too long). If this is all you are going to do, I would appreciate it if you would stay out of this thread. "

actually, I'm giving honest and fair tips. I'm not saying "you suck!", I'm saying "you can do better!" in a positive way. as for the lying/cheating......that was a legitimate gripe. it wasn't just about the flight being clearly longer than the available fuel burn time, it was also about the distance that flight achieved in that time frame, and the use of parts that were explicitly disallowed in the rules which allowed completely different ship configurations that wouldn't have been an option otherwise.

Edited August 13, 2012 by trekkie_

[Tigga]

even if you are jettisoning them in order from outer to inner, you're still forcing them to carry the extra weight of the inner engines which are dead weight until they're activated. basically think about how many of those 20 thrusts you have activated at once, and figure out a way to keep only those while jettisoning just the tanks. that way you're not carrying the extra weight of engines when you already have other engines providing the same thrust, only to throw them away, while still carrying their weight and drag twice fold in previous stages....get it?

You don't seem to understand. They can be activated off the launchpad and be configured to only use the fuel from the outermost tanks. All you do as you go up is jettison the outermost tanks (and engines). You don't have to light up any more engines. The inner engines are not dead weight as they're activated at the same time as the outer engines.

[khyron42]

OP has been updated with separate category for the non-10-tank results from simplymunrockets flight, making my earlier 10-tank 1037 km (15:55 burnout) still stand as the 10 tank record.

kerbtrek, It's fine to provide feedback but ideally, do so by flying an improvement of their design and showing them how it can be better, not arguing. If thier design can't be made better, suggest (and show) alternate designs that try to accomplish similar things. Give people something to go "wow, that really is better!"

Here's the latest attempt by me to do something different - 10 tanks, no ASAS, no aerospikes, just hand flying with the pod's SAS, boost to orbit and then use the high-efficiency LV-909 to boost directly pro-grade.

Burnout speed ~4847.5 m/s

Burnout altitude ~651 km

Specific orbital energy 8.92 MJ/kg

Not an improvement in any category, but it might be something people can improve on further. Just putting aerospikes on the first stage might do it, but I'm tired; I'll try it tomorrow if no one else does.

----

I stayed up a little later than I should, and swapped out the first stage engines for aerospikes.

5.0795 km/s

858.5 km

10.48 MJ/kg <--- new record!

Edited August 13, 2012 by khyron42

[trekkie_]

You don't seem to understand. They can be activated off the launchpad and be configured to only use the fuel from the outermost tanks. All you do as you go up is jettison the outermost tanks (and engines). You don't have to light up any more engines. The inner engines are not dead weight as they're activated at the same time as the outer engines.

which would bring me back to my original point....they provide what....160 thrust or so, for 4.0 weight and 1.6 drag. on top of the extra weight and drag from the extra decouplers. that honestly does not negate the 0.8 weight incurred by the empty tanks, even taking into account their low fuel usage. this is more apparent considering it didn't break any altitude nor speed records, so in comparison it's fair to say it's not worth it when going the distance nor for speed. don't take offense to the facts people.

[mathmavin]

I think I've got a ship that beats the current records for both altitude and energy. I came pretty close to the velocity record on one run, too - it's possible that a tweaked trajectory could allow for this ship to pass it, but it's a 15:02 flight time, so I only did 2 runs - I'm sure I don't have perfectly optimal trajectories in either the highest altitude or the highest energy cases.

http://imgur.com/a/bEdet

Difference between the two runs was pretty much how much I angled the craft when I started my gravity turn at ~10 km.

For the altitude run, the screen shot has 1493 km, but I think I took it 1 or 2 seconds after burnout, so if you account for the current velocity and direction of flight, it'd probably be something between 1485 and 1489 km.

The energy run has an altitude at burnout of 1456 km and a velocity of 5239 m/s. This gives an end result of 12.0 MJ/kg, if my math is right.

[trekkie_]

not counting jet engines (which aren't even counted anymore anyways), yeah thats pretty far. how high were you when you got down to the last stage?

[mathmavin]

I think I was somewhere around 60 km? I don't remember off the top of my head.