The Launch Efficiency Challenge [0.17 STOCK]

[ChronicSilence]

Good day fellow Kerbalnauts,

With v0.17 comes the delicious challenge of getting to other planets. In order to do this, you need a solid spacecraft design, and that is what we're going to work on today. There are countless different design methods, and we are going to try to find the most efficient of them.

Objective:

Carry the greatest payload (fuel in unopened tanks) to a circular Kerbin parking orbit of 300,000m

Rules:

- You may burn no more than 45,000 L of fuel

- 350 part count limit

- No jet engines: rockets only

- No aerospike or atomic engines, as their efficiency is not in line with the others and will skew the results

- Only stock parts, with the exception of MechJeb. MechJeb launch is actually encouraged, since it removes the human error as a factor. However, when you post your result also post the settings you used for MechJeb (turn start, turn end, final path angle, approx. location of turn shape slider)

People can self-report their values on this thread, and then I'll personally test the top few to confirm. And then we will know the best launch configuration! If there's lots of interest, we can add some different categories for different efficiency challenges.

Good luck o7

Results:

1) ----------

2) ----------

3) ----------

4) ----------

Edited September 23, 2012 by ChronicSilence

[Designer225]

300000 kilometer? The Kerbin Sphere of influence is 80000 kilometers (KM), and you expect us to do it? You must be out of your mind.

[Designer225]

And keep in mind that I won't do the challenge unless you prove you are not joking.

[ChronicSilence]

Oh don't pretend you didn't know what I meant. I've fixed the mistake to 300,000 metres.

[EndlessWaves]

Are the mechjeb pods allowed or does it have to be a stock pod?

[Designer225]

Actually...

I saw your thread yesterday and it says km.

Anyway, I'm in.

[Designer225]

I guess I will use a one-manned capsule and use stock parts. Also MechJeb.

[MaverickSawyer]

Challenge Accepted! starting KSP now...

EDIT: do we have to recover the capsule, or is leaving it on orbit allowable?

[MaverickSawyer]

OK, here's my entry's specs:

25 parts

2 stages

3800 liters of fuel

arriving with ~180 liters remaining at peak of the orbit...

Recovery is NOT an option with this one. I'll work on a recoverable version next.

Pic after orbital circularization: [ATTACH=CONFIG]33509[/ATTACH]

Ship: [ATTACH]33510[/ATTACH]

EDIT: Derp. Forgot the specs for MechJeb. Set Ascent Autopilot to ascend to 300 km, all other elements at default.

Edited September 25, 2012 by MaverickSawyer

[Analogy]

I went ahead and just adapted my old Hercules design and did a flight which took 16800 liters to orbit using an un-optimized mechjeb trajectory.... before I realized that I was supposed to do it burning less than 45,000 liters, ha. I burned 127,200 to get that 16800 up there. Still, you could probably build a craft that could pull off a grand tour of the Kerbin system with that kind of payload mass, especially using nuke engines.

BRB working on a lifter that will sit within the fuel limit...

[Analogy]

All right, this time I burned about 44,500L of fuel to put 6,800L into orbit. Again, completely unoptimized mechjeb trajectory, and the craft becomes a bit unstable just before the second stage separation so that probably wasted a bit of fuel... I probably need to work on where the craft's center of gravity goes relative to its center of thrust as fuel gets used up but too lazy to do it now.

Anyway... Yeah.

EDIT: Added a new .craft which adds a NERVA to the top stage and modifies the struts. The NERVA's so tall that is raises the center of gravity by pushing the top stage's tanks further away, so there is no longer the instability as the second stage runs out of fuel, and as a bonus, you can now explore the Kerbin system with your 6400 L of fuel. I dunno what that is in delta-V, but at 800 isp it's like, a lot. You'll have to add a parachute and another decoupler if you wanna come home though. That might bust the fuel requirements for launch over 45kL, unless messing with the launch trajectory gets you some extra efficiency.

Edited September 25, 2012 by Analogy

[MaverickSawyer]

Wait, we're supposed to deliver fuel to orbit? Dang it, I KNEW that was too easy! Back to the drawing board!

[Peppe]

New to this, but burn limit seems hard to build for and are solid rocket boosters allowed?

I'd be interested in the most efficient way to get up a double large fuel tank.

I got one large barrel (1600L) into 300k orbit.

Also got the large double barrel into orbit (3200L) with a similar design and just adding a booster first stage.

I think i could scale it to 3 large doubles... part limit might be issue at 3 or more.

[Analogy]

New to this, but burn limit seems hard to build for and are solid rocket boosters allowed?

I'd be interested in the most efficient way to get up a double large fuel tank.

I got one large barrel (1600L) into 300k orbit.

Also got the large double barrel into orbit (3200L) with a similar design and just adding a booster first stage.

I think i could scale it to 3 large doubles... part limit might be issue at 3 or more.

I would bet that SRBs are allowed... I tend to avoid them in my designs since they make very little difference in the overall payload capacity of my rockets unless I use a lot of them, to the point where my vehicles stop being simple and elegant.

Part limit is not my limitation to getting mass into orbit. I got 5 large tanks (16,000L) into orbit with around 200 parts, still way under the 350 part limit. The limitation is fuel. IMO it would be fairly difficult to get very much more than 2 large tanks (6,400L) on 45kL of fuel burned unless you resorted to an extremely kerbalish rocket... I tend toward simplicity with my vehicles which resulted in me using the large but fairly inefficient rockomax engines on my launcher... If you were willing to put up with the complexity it's possible that a large cluster of the smaller engines might do you better. More mass for the same thrust, but higher isp, I haven't done the legwork to figure out if the trade is worth it.

[Peppe]

I would bet that SRBs are allowed... I tend to avoid them in my designs since they make very little difference in the overall payload capacity of my rockets unless I use a lot of them, to the point where my vehicles stop being simple and elegant.

Part limit is not my limitation to getting mass into orbit. I got 5 large tanks (16,000L) into orbit with around 200 parts, still way under the 350 part limit. The limitation is fuel. IMO it would be fairly difficult to get very much more than 2 large tanks (6,400L) on 45kL of fuel burned unless you resorted to an extremely kerbalish rocket... I tend toward simplicity with my vehicles which resulted in me using the large but fairly inefficient rockomax engines on my launcher... If you were willing to put up with the complexity it's possible that a large cluster of the smaller engines might do you better. More mass for the same thrust, but higher isp, I haven't done the legwork to figure out if the trade is worth it.

Your simply designs posted anywhere?

I've deleted most designs I came up with even if they worked they ended up pretty ugly.

Only played a couple days and still figuring it all out. Learned about gravity turns last night and found a whole new world of options.

If they add docking/fuel transfer/cargo type activities then I think these designs will be very useful. If they stay simple all the better.

I assume kerbalish is when you stop looking like a rocket and start looking more like your launching building.

[Analogy]

Your simply designs posted anywhere?

Pretty much everything I do is a variant of the first craft I posted in this thread. A bunch of boosters around a central core feeding fuel into each other so that just one pair of boosters is draining fuel at any time. I'll vary the number of boosters, amount of fuel, and types of engines depending on what my payload requirements are. The second craft I posted is an example of this process in action. Because I was only allowed to burn a certain amount of fuel, the craft ended up a lot lighter, so I used fewer booster pairs so that the amount of thrust was matched to the weight of the vehicle, and also to reduce the amount of vehicle weight tied up in engines. I switched the inner engine to a trio of lighter engines with higher isp to get myself better fuel efficiency once the vehicle was light enough and high enough that it didn't need a lot of thrust anymore.

I assume kerbalish is when you stop looking like a rocket and start looking more like your launching building.

Heh, exactly.

[Designer225]

I don't get it at all.

[Designer225]

Un.... It is okay to reach a lower orbit, then boost up to higher orbit?

[quarthinos]

I got 6400L into a 300km orbit with no solids. I'm not sure how much "fuel" a solid is considered to be anyway. I used something close to the standard ascent profile with mechjeb (I'd been fiddling with it for another rocket, and I'm not sure it's exactly in the middle). I'll post the craft file when I get home. I had some fuel left in the tanks after the 6400 launch, so I stuck an extra 200L tank on top and hit launch before I left for work. I'm sure that'll get to orbit, but I'm not sure if it'll be a 300km circle. Next up is fiddling with the gravity turn and maybe try some 3m engines, as I'm currently using clusters of 1ms right now.

Edit: This configuration gets the 7400L of fuel above the topmost decoupler to a 233 x 300 orbit. Take off the 200L tank, and it'll get the specified orbit.

Edited September 28, 2012 by quarthinos