[0.22-0.23.0] Delta-V Maximization Challenge

[NeilC]

TUFOM, your stage 0 is different than the challenge rules. Check the other designs - it must be just the probe core, mechjeb, and the decoupler.

Stage 0 has 0 delta-V, you only get 5 "real" stages to play with.

tavert, what does the on-paper 37km/s design look like in terms of # / type of engines? Does it use Aerospikes? Even if the 48-7S is theoretically more efficient, I found 1xaero to be more practical than 16x 48-7S in terms of actually building something that flies.

Hopefully 0.23 will correct some of the issues in the VAB. Right now, building rockets this large is a challenge unto itself.

[obi_juan]

OK.

I made the modifications and I have my new flight.

The orbit was higher than I specter...

And now after the stage separation...

But I don't think that this is my best ship... is only the heaviest until now... Later I will show the best ship that I made for this challenge, I need to build the launcher.

[tavert]

tavert, what does the on-paper 37km/s design look like in terms of # / type of engines? Does it use Aerospikes? Even if the 48-7S is theoretically more efficient, I found 1xaero to be more practical than 16x 48-7S in terms of actually building something that flies.

I constrained it on part count, not mass, so it looks like an even larger version of my previous design, but with one more huge LV-N drop-tank stage instead of the 48-7S final stage. I fixed a bug with the fuel flow in the optimization and it's now 38 km/s on paper:

stage 1: 1 LV-N, 12 tons of fuel, 11.2 km/s

stage 2: drop tank, 96 tons of fuel (3 jumbo), 11.7 km/s

stage 3: drop tank, 608 tons of fuel (19 jumbo), 11.0 km/s

stage 4: 16 mainsails, 1088 tons of fuel (34 jumbo), 2.32 km/s

stage 5: 35 mainsails, 2528 tons of fuel (79 jumbo), 2.17 km/s

Total mass over 5000 tons. Theoretically only 200 parts, before adding struts and splitting parts up for symmetry/structural reasons. Realistically probably more like 4 or 5 hundred parts, at least.

Edited December 4, 2013 by tavert

[numerobis]

That's basically the same as I was trying to build, except I merged the mainsails to get a mainsail SSTO with the 700ish tons aloft split over four stages.

[obi_juan]

This is the one that I think that is my best design until now:

The spaceship with the nuclear engine weight less than 100t, is very easy to bring that ship at low orbit around Kerbin. But I wanted to improve the ship so I use only spikes 7*6+7*12= 126 engines (the problem for me is with all these part is impossible for me pilot it manually, my computer is a little old)... with that rocket I reach orbit with more than 1/3 of the fuel of the stage 4 so I keep more than 2000m/s to start the interplanetary travel.

And here is my real question: Worth making a rocket that weighs 150% more than this for just a 22% increase in delta-V?

(yes, in this challenge worth it, and I hope to see the next ship of tavert.)

[numerobis]

Bedtime here, but progress: this SSTO has just one strut per column (apart from the central column, which has none). I'm hoping to scale this up with just an extra 2 struts every third column. Looks like locking gimbals will be necessary though; I forgot on this test run.

The name of my game is building big with few parts.

[Superfluous J]

Your ship has almost exactly the same TWR, ISP, and dV as the central column would have on its own. See below the readings from Kerbal Engineer Redux, and proof that it's not some weird bug or something. I got my ship in orbit as well.

Amusingly, this is the very first SSTO I've ever made (and actually put into orbit. I've made a few ships that may have had the capacity but never bothered to put them in orbit).

Edited December 4, 2013 by 5thHorseman
I proved my theory, which I now state as a fact.

[Nao]

You guys are doing one thing wrong . There should be only one high twr stage. For example a rocket SSTO (based on 2/3 mainsail thrust and 1/3 aerospikes) with only ~1.3 TWR can have payload fraction of almost ~12%.

I have a plans for craft with 33,7km/s dV and launch weight of around 1300-1400 tons using SSTO but i don't have time to actually do the first stage design and launch the whole thing. Good luck !

edit: and suddenly numerobis with an SSTO , this forums needs an "new posts since refresh" warning hehe.

[tavert]

Your ship has almost exactly the same TWR, ISP, and dV as the central column would have on its own. See below the readings from Kerbal Engineer Redux, and proof that it's not some weird bug or something. I got my ship in orbit as well.

The difference is higher payload at the same dV and TWR.

You guys are doing one thing wrong . There should be only one high twr stage. For example a rocket SSTO (based on 2/3 mainsail thrust and 1/3 aerospikes) with only ~1.3 TWR can have payload fraction of almost ~12%.

I have a plans for craft with 33,7km/s dV and launch weight of around 1300-1400 tons using SSTO but i don't have time to actually do the first stage design and launch the whole thing. Good luck !

My optimization algorithm begs to differ, at least based on part-count constraints up to 200 (just counting fuel tanks and engines). If the extra stage of LV-N fuel were valuable enough to offset the decreased payload fraction of a single-stage lifter, the solver would've returned that as optimal.

[Nao]

My optimization algorithm begs to differ, at least based on part-count constraints up to 200 (just counting fuel tanks and engines). If the extra stage of LV-N fuel were valuable enough to offset the decreased payload fraction of a single-stage lifter, the solver would've returned that as optimal.

Well i guess I'll need to do some work it seems . Pretty sure it's possible to get 33,5-34km/s below 200parts (including struts) with ~1600t SSTO launcher.

I didn't followed the thread closely thou, so I'm unsure if 33,7km/s is enough to beat your algorithm thou.

[numerobis]

Theoretically, if part count is no object, you do four LV-N stages with infinite fuel ratio, and get 69 km/s off those, then you bring that to orbit with an SSTO based presumably on the 48-7S (or maybe a mix), with TWR 1 on the pad.

Since part count matters, the SSTO may not be optimal. But it's fun to try to build!

My construction needs an extra O(ln(n)) struts; the columns that bear the payload need to be reinforced, because the jumbo tanks are so floppy.

Edited December 4, 2013 by numerobis

[TUFOM]

Now this should be by the rules:

Possibly I could made to 30km/s dV by improving this design but this took 7 hours time to design... so this is far as I would go with this challenge.

Total ÃŽâ€V @vac 25 438m/s

Edited December 5, 2013 by TUFOM

[numerobis]

Harumph. I'm starting to get annoyed at The Wobble . Physics initialization is wonky -- you get a big jerk at the start -- and then instead of dampening, PhysX seems to increase the oscillations. So my larger spacecraft tear themselves apart on the pad, before I even get to launch.

That said, the editor extensions mod has lovely vertical snapping that I've always wanted, among other things; it really speeds up construction a lot. The only thing on my wishlist still missing is snapping for the second endpoint of a strut.

[TUFOM]

Harumph. I'm starting to get annoyed at The Wobble . Physics initialization is wonky -- you get a big jerk at the start -- and then instead of dampening, PhysX seems to increase the oscillations. So my larger spacecraft tear themselves apart on the pad, before I even get to launch.

That said, the editor extensions mod has lovely vertical snapping that I've always wanted, among other things; it really speeds up construction a lot. The only thing on my wishlist still missing is snapping for the second endpoint of a strut.

Good news then for you my friend. Maxmaps told in twitch stream that wobble will be gone in 0.23.

[rkman]

When you add a category for 100 ton mass, here's my entry for it at 21580 m/s (and 195 parts, was optimizing for mass not part count though):

Those engines on the sides don't normally attach like that to the girder segments do they? Looks like modded for surface attachment.

[tavert]

Those engines on the sides don't normally attach like that to the girder segments do they? Looks like modded for surface attachment.

Wasn't using any construction mods, just stock cubic octagonal struts. Looks like it was 3 horizontal, 1 vertical.

[totalitor]

My rocket: deltav is 26219 m/s. Parts used 167. Stages 2 and 3 are asparagus.

On orbit

Another picture on orbit

[obi_juan]

My rocket: deltav is 26219 m/s. Parts used 167. Stages 2 and 3 are asparagus.

Exceptional design, the idea of use only one stage to take the ship into orbit is an elegant solution.

Probably I will change one of my ships for this challenge following you idea. When I saw your ship I remember that my last ship had delta-V of 5000m/s with only stage 4.

[numerobis]

Good news then for you my friend. Maxmaps told in twitch stream that wobble will be gone in 0.23.

Oh, nice! I guess I'll just wait until then...

[TUFOM]

Used same core design as earlier... proved to be potential for tweaking.

Total ÃŽâ€V @vac 27 303m/s

[Nao]

Edit: OK got that mess of a post and silly mistakes cleared out.

It was done quick since i was short on time. Build from scratch, no testing, one launch. Everything went pretty much perfect (E: had to launch the second time due to lack of decoupler on the probe core )

34434m/s 197parts The rocket itself is 131parts, and damn in this patch Mainsails don't like touching ground.

On pad (with F3 and throttle up- showing that it's stable on pad)

In space (had to burn +8minutes on Nerva and briefly return to atmosphere (Pe 60km)

It uses 24 RT-10s, 12x Mainsails, 7x Skippers, and one LV-N With every engine except the NERVA in SSTO configuration.

Edited December 8, 2013 by Nao
corrections galore.. im so bad at posting >_<

[tavert]

Don't think I can beat that at 200 parts, at least not with anything that doesn't fall apart during flight. Orange tanks make my large rockets fail for no good reason, despite quite a bit of strutting. I have some designs built at 35 and 36 km/s that should eventually work at higher part counts, given enough time tweaking and probably replacing all orange tanks with 32's. I'm frustrated enough at the structural failures that I give up for now.

Using skippers is an interesting approach, letting the mainsails run out of fuel first to improve Isp - it's not much of an improvement though, I'm surprised it's worth their lower TWR.

[lump]

Here's a 9124 m/s SSTO at under 100 tons:

And in orbit, same number of parts (246) minus the 3 launch clamps:

I'm pretty sure this is a record for a rocket-only SSTO that can get itself into orbit (until shown otherwise by another entrant here, I guess). The vertical design was so I didn't have to worry about symmetry and complicated fuel flow. There's a little gap below each set of 48-7S's with a couple of cubic struts, attached in a way that they don't crossfeed. Could've also used docking ports and disabled crossfeed that way, but they're heavier than struts

MechJeb doesn't get the TWR right, since all of the 48-7S engines are out of fuel by the time this reaches orbit. 60 kN thrust from 1 LV-N, divided by (26.67 tons times 9.81 m/s^2) gives TWR = 0.23, at least at the point the screenshot was taken. Minimum TWR is a little lower, right at the moment the last of the 48-7S engines runs out of fuel.

I'm finaly back frommy half a year vacation from the forums, and tavert, awesome rocket, although it's beatable:

i made it too fast to give it a name but it only uses 77 parts and has over 4100m/s delta-V once in orbit, there are plenty of things i could do to improve this i'm sure but it's still simply awesome.

[numerobis]

Are you going to hint at how you built that thing? I can't see anything.

[lump]

Well its got one nerva in the middle, and 8 48-7s rockets on each fuel tank, and no fuel lines, it was really really simple and easy to make, no complicated fuel flow shizzle here.

Edit: i think i can make a manned one with parachutes and whatnot to make a round trip to duna.

Edit Edit: yeah ok this is going to work fine, i have got this craft up to orbit with 3600m/s delta-V to spare, thats:

-1100 for transfer to Duna

=2500

-1700 for going up to duna orbit

=800

-800 for transfer to kerbin

=0

these values are very rough and a but too pessimistic but its's more than possible

some pics:

Edited December 17, 2013 by lump