[0.22-0.23.0] Delta-V Maximization Challenge

[mhoram]

With the arrival of new engines in version 0.23.5 consider this challenge finished and closed. Please do not submit new entries.

Thanks to all participants for their creative crafts.

This Challenge is mostly directed to Rocket Builders and I got inspired by the Poodle vs Lv30/45 thread.

There was a similar discussion back in May.

This thread should be helpful.

If you get past these theoretical bounds, I would like to get a hold on the .craft file.

Mission Description

Create a Rocket with the largest amount of Delta-V.

Scoring

The score is the Vacuum-Delta-V value of the rocket on the launchpad according to MechJeb.

The higher the better.

Rules

• Only Stock-Parts may be used with MechJeb for evaluation of the Delta-V value.
  
• The payload consists of an Okto2 core, the MechJeb Module and a TR-2V stock decoupler at the bottom and no additional parts (example .craft)
  
• The Rocket must be stable and powerful enough to leave Kerbins atmosphere (either by getting into a non-decaying Kerbin orbit or by leaving Kerbins SOI)
  
• Ion- and Jetengines are forbidden
  
• A maximum of 6 stages including the payload are allowed (0 to 5)
  
• No cheating, debug console, part clipping, infiniglide
  
• Only decouplers can be used for decoupling. (No dockingports, no decoupling by explosion, ...)
  

A valid submission contains:

• The number of parts of the rocket on the launchpad
  
• a screenshot of the rocket on the launchpad where Vacuum-Delta-V and Min-TWR are visible
  
• a screenshot of the rocket outside of Kerbin atmosphere
  

Sanity Check:

• Stages can only be decoupled when their fuel is depleted
  
• After starting the engines, the rocket must not touch the ground
  

Awards

Classic Staging Award: do not use Asparagus staging

SSTO Award: the propellant consists of a single stage

Leaderboard

1. 34522 Sensi (698 parts, 4665.6 ton, 0.02 TWR)
   
2. 34434 Nao (197 parts, 1743.1 ton, 0.02 TWR)
   
3. 33208 obi_juan (562 parts, 2253.04 ton, 0.02 TWR)
   
4. 32587 tavert (145 parts, 1219.06 ton, 0.03 TWR)
   
5. 27550 dcethe (581 parts, 2082.9 ton, 0.14 TWR)
   
6. 27303 TUFOM (294 parts, 1184.22 ton, 0.04 TWR)
   
7. 26742 chlue (132 parts, 393.930 ton, 0.14 TWR)
   
8. 26219 totalitor (167 parts, 849.63 ton, 0.13 TWR)
   
9. 26128 mhoram (189 parts, 738.92 ton, 0.14 TWR)
   
10. 24840 NeilC (271 parts, 469.17 ton, 0.10 TWR)
    
11. 23872 Seanner (217 parts, 705.55 ton, 0.30 TWR)
    
12. 09124 tavert (294 parts, 96.92 ton, ~0.23 TWR) SSTO Award
    
13. 08778 Seanner (109 parts, 66.33 ton, ~0.32 TWR) SSTO Award
    

Attic (keeping the leaderboard clean)

1. 33152 obi_juan (555 parts, 2249.67 ton, 0.02 TWR)
   
2. 31202 obi_juan (750 parts, 1975.52 ton, 0.06 TWR)
   
3. 25438 TUFOM (182 parts, 742.07 ton, 0.06 TWR)
   
4. 23069 mhoram (71 parts, 339.35 ton, 0.16 TWR)
   
5. 21707 obi_juan (223 parts, 334.61 ton, 0.14 TWR)
   
6. 21580 tavert (195 parts, 99.99 ton, 0.24 TWR)
   
7. 21441 obi_juan (193 parts, 289.31 ton, 0.14 TWR)
   

Edited April 1, 2014 by mhoram
Closed challenge

[mhoram]

Here is my sample entry with 23069 dV. (.craft)

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Edited November 27, 2013 by mhoram

[Superfluous J]

Seems like this contest will benefit those who can use the most parts.

[mhoram]

Seems like this contest will benefit those who can use the most parts.

I don't want to restrict the number of parts. But you are right, so i will require that each submission contains the information about how many parts are used.

In this way the leaderboard gets a bit more comparable.

[NathanKell]

Sounds like you want pure asparagus with either 48-7S clusters or LV-T30 clusters; I haven't quite crunched the numbers. It's just whether you get more from the mass ratio increase of 48-7S, or the Isp increase of LV-T30. Certainly it should be a single 48-7S on the core stage.

[tavert]

Can you clarify exactly what you mean by "powerful enough to leave Kerbin (Kerbin orbit or Kerbin-escape)"? Does initial TWR have to be >= 1?

[Kasuha]

Obvious solution is to have one nuclear engine and as much fuel as you can lift in five stages, then use the sixth stage for lifter from land directly to orbit. Whatever dv left in the lifter will add up with insane dv from the nuclear engine and its five stages.

[mhoram]

@tavert

The ship must be able to leave the atmosphere of Kerbin.

The idea behind this rule is that

- it's structure is solid enough to be usable (survive the ascent through Kerbin's atmosphere)

- it has enough thrust to be useful (it can get into space)

One way to show this is to get into a non-decaying orbit above Kerbins atmosphere and another is to leave Kerbins SOI.

In order to accomplish this, the initial TWR should be >= 1.

I will clarify this in the OP.

@Kasuha

In my tests I got better results by having a 48-7S-stage after the LV-N stage.

Currently I think about introducing categories based on the number of parts (<100, <200, >=200) or the mass (<100, <500, >=500)

Edited November 28, 2013 by mhoram

[tavert]

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):

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Edited November 28, 2013 by tavert

[Seanner]

I prefer brute force myself, so weighing in at just under Jool:

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I have a nitpick with the staging award, because for max deltaV per stage you would want serial/onion staging. The award should perhaps be "fancy staging" for users of asparagus.

Just messing around in the editor it looks like a nuke can break 15k but for overall part count reasons I didn't go all out. I only used 4 stages too, so 15k+15k+15k serial then 2 for liftoff, or as suggested, 1 for liftoff (absolutely ridiculous number of mainsails needed....) you could do 4*15k or more in nuke stages. Max deltaV could approach 70k but my computer seems happy with 23-24k for now.

edit: Cool design tavert...super small for such deltaV!

Edited November 28, 2013 by Seanner
15k not 19k

[numerobis]

Seems like this contest will benefit those who can use the most parts.

Pretty much. The trick is just to pack as much fuel as possible in the top 4 stages with one LV-N, and put that on a high-TWR stage with ~4500 m/s. I'm currently waiting on precisely this (2k parts... might not load before I need to leave for dinner).

[Seanner]

Oh right I forgot about drop tank method....so my math is wrong for max possible...what's your delta V in this setup?

[numerobis]

30 km/s... but I gave up after a half-hour. I'll have to try on my desktop.

I had enough launch dV and TWR to add another 2-5 km/s also.

[tavert]

I had a 29+ km/s design built to a 500 ton limit (and something like 600 parts), but it kept losing control after dropping the first stage. I think I'll need to impose a minimum percentage of vectored thrust to keep it controllable.

Also, mhoram, I tweaked my original design a little for another few hundred m/s about an hour after initially posting, hoping no one would notice.

[mhoram]

I have a nitpick with the staging award, because for max deltaV per stage you would want serial/onion staging. The award should perhaps be "fancy staging" for users of asparagus.

Besides deltaV you also need enough TWR to bring it into space. So far I am not convinced that serial/onion is easier than asparagus.

Also, mhoram, I tweaked my original design a little for another few hundred m/s about an hour after initially posting, hoping no one would notice.

Sorry, but I did not notice the change. Updated the leaderboard.

[tavert]

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.

Edited November 29, 2013 by tavert

[NathanKell]

tavert: nice!

Although, heh, I find it deeply humorous that it's still less than is required for LEO (via RSS)

[mhoram]

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

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

This is an amazing innovative design.

The idea of disabling engines by inner-stage-tank-depletion is something I never thought about.

[tavert]

This is an amazing innovative design.

The idea of disabling engines by inner-stage-tank-depletion is something I never thought about.

Thanks, glad you liked it! Setting up the fuel tanks to deplete low-Isp, high-TWR engines before high-Isp, low-TWR engines was how I got a rocket-only "SSTOMAB" to work, many months ago (before the 48-7S and its current overpowered-ness): http://imgur.com/a/uA4c5

This technique is the only way to get around the single-stage limit at TWR=1 of 6746 m/s for a 48-7S with zero payload.

I'm looking now at a different way of laying out the design with no fuel lines at all, just clever timing of engine-to-fuel-tank ratios and burn times. This might look saner (build out instead of up), but the optimization problem's a very different formulation. My two designs so far were both determined by a mixed-integer nonlinear optimization solver, and the code for the SSTO was fairly similar to the asparagus version, just had to change the dry mass calculation to account for not dropping empty tanks and burnt-out engines.

[Seanner]

I too have an entry for a light-ish deltaV craft:

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The half-high orbit was me being lazy and not wanting to figure out how to get 0.25 TWR into standard orbit, so I just climbed entirely too high while I had the thrust to buy time to circularize. I forgot about min TWR but the one screenshot shows it pretty close to it since not much fuel was used by the nuke post-rocko-burnout.

The keen observer of our entries sees that we burned far over 4500m/s to acheive orbit (due both to horrible takeoff TWR and usage of nuke at low Isp), and so the deltaV figures given are sort of padded by using lots of fuel to maintain a hover more or less.

edit: Is it better to lift the nuke with more tiny rockos for a couple thousand feet? I know in general one wants to use all engines where possible but the nuke becomes far more efficient pretty quickly so intuitively it seems like if one waits a bit then activates it...I mean does 0.3 mass of rocko really lower the dV beyond what is saved by not burning through nuke fuel for the first minute?

Edited November 30, 2013 by Seanner

[mhoram]

The keen observer of our entries sees that we burned far over 4500m/s to acheive orbit (due both to horrible takeoff TWR and usage of nuke at low Isp), and so the deltaV figures given are sort of padded by using lots of fuel to maintain a hover more or less.

Thanks for the submission!

While designing the challenge, I thought about scoring by the fuel left after reaching an orbit. My reasoning was that this challenge should be about building rockets and not piloting them. Would you find it interesting to have a separate category for this?

[Seanner]

If enough other people do, sure. It goes hand-in-hand with optimal ascent, and leads to the best overall craft I guess.

[tavert]

edit: Is it better to lift the nuke with more tiny rockos for a couple thousand feet? I know in general one wants to use all engines where possible but the nuke becomes far more efficient pretty quickly so intuitively it seems like if one waits a bit then activates it...I mean does 0.3 mass of rocko really lower the dV beyond what is saved by not burning through nuke fuel for the first minute?

The losses due to atmospheric Isp are pretty minor with only one LV-N, even at the 1.2 takeoff TWR our SSTO's are using. Take initial vacuum dV minus final vacuum dV minus dV expended from ascent stats, and the difference is under 200 m/s. Try with a pure-aerospike rocket and you'll see that difference should be nearly zero.

Overall payload fraction is a slightly different story, since the low TWR increases the delta-V cost of ascent. What I've been doing here is imposing a minimum TWR constraint at each staging (or pseudo-staging, engine burnout for the SSTO) event, using a function of cumulative dV in lower stages. For my staged design I used TWR >= 1.5 - dv^2 / 1.35e7, and for the SSTO I used TWR >= 1.2*erf(4 - dv/1125), lower starting value but stays higher a little longer.

This is a heuristic, but quite a bit easier than putting the full flight physics into the optimization problem along with the integer design variables, and doing simultaneous optimization of both the design and the ascent trajectory.

Edited November 30, 2013 by tavert

[numerobis]

Odd; KSP glitched and set up my beautiful spacecraft with about a third of it piled sideways just off the pad, on the opposite side from where it was supposed to be, and throttled up. Also, an orange tank was on top of my probe, but I hadn't put one there.

Then physics started up, so a couple hundred orange tanks started flying around KSC and crashing into things.

The second part makes sense given the first, but the first part is very odd. This is a clean install too!

Edited November 30, 2013 by numerobis

[NeilC]

Here's my entry. Riding the mass vs Delta-V curve way up past the point of diminishing returns, I give you this behemoth:

271 parts

469.17 tons

24840 delta-V

0.10 min TWR

The design uses 4-way asparagus on the LV-N orbital stage for the bulk of the delta-V, a central sustainer booster using a TON of those overpowered 48-7S engines, and 4 crossfed first-stage boosters using aerospikes for high-ISP TWR during the early launch.

Although the engines are definitely overlapping visually, part clipping was not used. I think it's a combination of the collider mesh for the 48-7S being smaller than the model, and part attachment being pretty buggy in general.

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Edited November 30, 2013 by NeilC