Optimal Architecture Comparison Challenge I: Mun

[Jasonden]

Apologies if this has been done before -- if it has, my brief search didn't turn up any evidence. I was inspired by reading this article at Universe Today about the design architecture for the Apollo missions. There was a very real and impassioned debate as to what mission design architecture to pursue for the American Apollo program. This debate took the form of three competing mission architectures:

1: Direct. 1 launch. All of the mission hardware would be launched at once, head to the Moon, land, and then head home. No rendezvous, no docking, no refueling. Simple, elegant -- and requiring a gargantuan launch vehicle to dwarf the Saturn V.

2. Earth Orbit Rendesvous (EOR). Mission hardware in one launch, fuel in a second launch. Then as in the direct approach the entire apparatus (minus spent stages) lands on the Moon, and heads back.

3. Lunar Orbit Rendezvous (LOR). One launch, but a separate lunar lander heads to the surface while hardware for the Earth return remains in lunar orbit. This was ultimately the route chosen and successfully implemented for Apollo.

---

Challenge: Design a system to send at least one Kerbal to land on the Mun and return safely to Kerbin. Your design should (but is not required to) fit into one of the three Apollo design architectures, but other than that diversity and creativity are encouraged.

Constraints:

• No cheating -- no debug menu, hyperedit, etc.
  
• No part clipping, even that allowed by the editor: all parts must not intersect -- exception: part-clipping on engines to create clusters is okay (if you want a 30-engine N-1, go for it)
  
• Stock parts only -- exceptions: informational mods that don't affect performance are okay. MechJeb and other flight-assistance is allowed: this is primarily a design challenge, not a flight challenge. Also: stretchy-tanks/stretch-SRB's are allowed to free you from the bonds of quantized fuel tanks
  
• Rule modification: part clipping and non-overpowered mod parts may be used under the condition that such entries include at least 2 different architectures to allow for intercomparison
  
• No performance-affecting mods; FAR is right out.
  
• Conventional rockets only -- no jets, ions, or nukes. SRBs and liquid-fueled chemical engines (including aerospikes) are the only allowed mechanisms for propelling your craft. Or use monoprop if you want to, that's fine too (if crazy?).
  
• Kerbals must be in a pressurized vessel except for Munar EVA -- no ladders or command chairs
  
• Crew manifest is allowed: no need to EVA to get your Kerbals through a docking port 1.25m or larger
  

Scoring:

Following the lead of MagiMaster in his Apollo Style Redux challenge, your final score will be the PRODUCT of the following subscores:

• Launch Mass (LM) = 100 t divided by your initial launch mass. If using multiple launch vehicles, this is the sum of their masses. To simulate the benefits of manufacturing in bulk, if using IDENTICAL launch vehicles (with different payloads of course), then multiply by the 4th root of the number of launches (i.e., for 2 launches multiply by ~1.2).
  
• Staging (S) = 1 for asparagus, 2 for conventional
  
• Kerbals (K) = 1 + log_2(# of Kerbals that land on the Mun, walk on the Mun, and are returned alive to Kerbin)
  

That's it. Final score = LM * S * K. I realize that the scoring is a bit arcane and mathematical, but it's not rocket science! That's the rest of the challenge.

Ultimately what I am interested in seeing is the relative value of each of these architectures for pursing the Apollo Moon-race goal of landing and returning safely. This is OACC1 in the sense that if it proves successful, I'd like to try the same for other targets. I think that the result might be different for Minmus relative to the Mun, for example. If you come up with a different architecture, distinct from the above, I would be interested including it, too, in a separate section. I am not looking for extensive evidence or proof of your exploits, but some pictures of your flights and the vehicle in the VAB would be nice. Multiple entries from a single person for different architectures are encouraged.

Scoreboard:

Direct:

1. tavert (2) -- 18.8
   
2. tavert -- 15.873
   
3. donfede -- 13.298
   
4. Deathsoul097 -- 10.88
   
5. 1Revenger1 -- 2.433
   
6. panzerknoef -- 2.217
   
7. Epthelyn -- 1.427
   

Kerbin Orbit Rendezvous (KOR):

1. PLAD -- 18.04
   
2. donfede -- 15.025
   
3. Jasonden -- 2.85
   
4. _
   
5. _
   
6. _
   

Munar Orbit Rendezvous (MOR):

1. donfede -- 9.860
   
2. 1096bimu -- 8.79
   
3. Tigik -- 5.44
   
4. _
   
5. _
   

Other Architectures:

1. MagiMaster (2) -- 5.664; 2-launch KOR+MOR
   
2. borisperrons -- 2.324; 4-launch KOR+MOR
   
3. MagiMaster -- 1.027: 3-launch KOR+MOR
   
4. _
   
5. _
   
6. _
   

This challenge will close for official submissions after 2014 February 28. At that point, we can look at the best scores and evaluate the wisdom (or foolhardiness) of the Apollo architecture choice. Or we might find that some intrepid Kerbal rocket scientist has come up with something that's better than any of these architectures -- 4-launch KOR combined with MOR anyone?

Edited February 26, 2014 by Jasonden

[MagiMaster]

Glad I could be of some inspiration. I think I might have to submit something for the Other category. KOR+MOR with 3 identical launchers sounds like an interesting build.

Edit: Thinking about it, I can see why this wouldn't be a realistic mission design though. It requires either someone waiting around in orbit or an automated docking. I'm still going to see how it all works out though.

Edited January 10, 2014 by MagiMaster

[SRV Ron]

Just some interesting info;

You need to do the NASA figure eight slingshot which has the fail safe return to Kerban. (Ideally, the aerobraking reentry should be a 20k one, not so steep as shown in this screenshot.) This was not easy to set up. http://airandspace.si.edu/explore-and-learn/multimedia/detail.cfm?id=5317

NOVA was the proposed rocket for NASA to do a direct mission. That huge rocket never made it beyond the planning stage.

http://news.discovery.com/space/history-of-space/nasas-biggest-rocket-120624.htm

Edited January 10, 2014 by SRV Ron

[Jasonden]

Is that Log <# of kerbals> base 2 or what is it ?

Yup -- 1 + log base 2 of the number of Kerbals. Hence 0 Kerbals gets you -infinity, 1 gets you 1 point, 2 gets you 2 points, 4 Kerbals get you 3 points, etc. This way there's a point of diminishing returns when it comes to Kerbal quantity.

[Sirine]

@Jasonden

Staging (S) = 1 for asparagus, 2 for conventional

Why promoting conventional launch? Asparagus is proven more effective, and harder to build. no?

[Jasonden]

@Jasonden

Staging (S) = 1 for asparagus, 2 for conventional

Why promoting conventional launch? Asparagus is proven more effective, and harder to build. no?

Well, mostly this was to better simulate the choice facing the creators of Apollo -- asparagus is more effective in the Kerbal universe, with super-heavy engines and crappy TWR, but not so much IRL. I suppose, though, that since this IS a Kerbal Universe, maybe the better approach would be to have 2 sets of standings, one for asparagus, one without. If you and others speak up on behalf of that, I'll do it!

[Jasonden]

Just some interesting info;

You need to do the NASA figure eight slingshot which has the fail safe return to Kerban. (Ideally, the aerobraking reentry should be a 20k one, not so steep as shown in this screenshot.) This was not easy to set up.

Nice free-return, Ron! I haven't managed to do that yet myself. I guess this seems to require a retrograde trajectory around the Mun then? I suppose that it, like our Moon, is rotating slowly enough that it doesn't make much difference which way you go 'round . . .

[tavert]

Encouraging non-asparagus designs with a score bonus could lead to some designs that are a little different than you usually see, so it's an interesting feature. But how would you classify Soyuz-style staging, with multiple stages starting to burn from the start but with central stages having more fuel than the boosters?

Your scoring also seems to encourage repeating the same mission multiple times, or at least to LKO just for the purpose of increasing number of Kerbals...

[Jasonden]

Encouraging non-asparagus designs with a score bonus could lead to some designs that are a little different than you usually see, so it's an interesting feature. But how would you classify Soyuz-style staging, with multiple stages starting to burn from the start but with central stages having more fuel than the boosters?

Hmmm. Given that Soyuz uses it, it's conventional, so will count as the 2x multiplier.

Your scoring also seems to encourage repeating the same mission multiple times, or at least to LKO just for the purpose of increasing number of Kerbals...

Well, I don't think so. Let's do a thought experiment. You launch one 2-Kerbal crew into orbit on a Mun mission, worth 1+ln(2)=2 points. Say your vessel masses 33t. If that mission were to be successful, then you would score 100/33=3 points from the rocket. Say it was asparagus, for the sake of argument, so that multiplier is 1x. So your score here is 6.

Now say you want to try to repeat the same thing to jack up your score. You launch a second, idential mission. Now the total number of Kerbals is 4, worth 1+ln(4) = 3 points. You have twice the rocket mass, so that's 100/66 = 1.5 from the rocket, times 1.2 for identical launches. Your score is now 5.4. So with this second launch, you've actually decreased your score by 20%.

OTOH, if you'd had only 1 kerbal initially, then 2 missions probably WOULD increase your score.

Incidentally, the 2nd-identical-ship scenario doesn't fit any of the 3 specified architectures, so perhaps it doesn't particularly matter, unless you're going for the open category.

[Markus Reese]

Aaah but tavert, trick to doing it is still within one of the three mission parameters. If you want to launch 20 kerbals, then it is one go, land a whole assembly that you assemble in kerbin orbit, or assemble in lunar orbit, then re-dock that back to your orbiting fuel payload.

Like all challenges, it really encourages pushing the envelope. Though I do think that launch mass (if I am reading the rules right) is quite exploitable. I can throw on inefficent and TWR of 1 engine assemblies onto the big orange tanks just to peak out the mass? I dunno if what I mean is making sense or not. I do like that more kerbals landed at once, is better score. If want a colony, just drop all 20 down

Edit: Oh, 100/33! Got ya, so extremely heavy is bad. Misread!

Edit^2: Hrm, never looked up my masses in KSP. Can you actually get said info in game without any mods? I don't feel like tallying up my weights ^.^

Edited January 10, 2014 by Markus Reese

[Jasonden]

Edit^2: Hrm, never looked up my masses in KSP. Can you actually get said info in game without any mods? I don't feel like tallying up my weights ^.^

Actually, yes! In the Map view, focus on your ship. Then click the 'i' on the right-hand side of the screen. It will tell you your mass in metric tons.

[tavert]

I slightly misread what you meant with the 4th-root bonus then. I thought instead of 2x the mass for a second identical launch, it would only cost 1.2x. Instead you're saying it costs 2x, but you apply the 1.2x bonus separately. So if n is the number of Kerbals and we assume mass depends linearly on n, the overall score goes as (1 + log_2 n) * n^0.25 / n? This would give 1.19 for n=2, but lower for all other integer n.

[Markus Reese]

I am actually quite interested in sandboxing this challenge. Adds some nice roleplay, I like that you have the objective side of it. Really creates variable. Go for heavy, but multiple kerbals, or lightweight and speedy, get that multiplier bonus.

[Jasonden]

I slightly misread what you meant with the 4th-root bonus then. I thought instead of 2x the mass for a second identical launch, it would only cost 1.2x. Instead you're saying it costs 2x, but you apply the 1.2x bonus separately. So if n is the number of Kerbals and we assume mass depends linearly on n, the overall score goes as (1 + log_2 n) * n^0.25 / n? This would give 1.19 for n=2, but lower for all other integer n.

Yeah, lets calculate this out. It looks to me that if, as you assume the mass depends linearly on n given your multiple-launch approach, and you're sending 1 Kerbal per launch, then if n=1, score~(1+0)*1 = 1. If n=2, then score ~(1+1)*1.2/2 = 1.2. For n=3, score ~(1+1.585)*1.32/3=1.14. For n=4, score ~(1+2)*1.41/4=1.06. So, actually pretty flat as a function of n, but peaked at 2, as you stated.

But should you bring just 1 Kerbal per launch? Could you not launch with 2 on a single launch instead, and increase your score that way? Up to you to figure out!

[MagiMaster]

Ugh. I got half way through the mission before I realized I kind of forgot what I was doing and had only built the lander to handle one kerbal. Oh well, it's still a valid entry, but I'm pretty sure I wouldn't have had to double my mass to send an extra kerbal up.

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Launch mass - I used the same launcher for all three launches but drained some fuel to keep the dV around 5000. I think I ought to have sent the tug up empty and sent the fuel up with the light return module. Oh well. That gives: 100 / (85.991 + 75.258 + 94.987) * 1.316 = 0.5136 points

Staging - Conventional staging. There are pipes, but they only connect radially attached tanks that don't separate. 2 points

Kerbals - Only 1 kerbal walked on the Mun unfortunately. 1 point

For a final score of 1.027

Not great, but an interesting challenge. I might try again and see if I can't do a bit better, but no promises.

Edited January 10, 2014 by MagiMaster

[Jasonden]

high score run with 4 kerbal landing and traditional staging, 68.28 tone launch mass.

Okay! This looks like a MOR run, score: (1+ln_2(4))*2*100/68.28=8.79

[tavert]

Here's a direct-ascent 1-Kerbal Soyuz-staged vehicle at 12.6 tons. Really doesn't take much to get to the Mun and back.

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I think the score here should be (1+log_2(1))*2*100/12.6 = 15.873.

It's probably possible to play with the staging on a multi-Kerbal version of this for slightly better payload fraction. Or add docking ports and launch twice for the 19% bonus.

[tavert]

Optimize my designs subject to different constraints? The strut just provides free connection points that can often be obtained in other ways if need be. The small engine is overpowered, definitely. As long as it's allowed and as long as its statistics make it the optimal choice, I'll continue to use it whenever it is the best choice to do so. The small decoupler makes a pretty minor difference overall, but if you care about function over form then there's no reason not to use it. And this design didn't use the landing gear for once.

Glitchy physics and part balance should be fixed, I agree there. But complain to Squad, not me if you don't like the way optimized designs turn out.

[700NitroXpress]

I basically did this challenge when I did a showcase for my Atlas V Lunar rocket. Would this count for method 3? What kind of staging would you classify this as? It's not really asparagus since I'm not dropping sets of 2 tanks, but I'm using fuel lines.

Spoilers: Niel Armstrong Memorial

[Deathsoul097]

MoonMission1.

My direct ascent mission to the mun.

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Score:

100/36.37=2.72

2.72*2= 5.44

5.44*2=10.88

(I think this is right, but feel free to correct me if I am wrong.)

Edited January 10, 2014 by Deathsoul097

[tavert]

What kind of staging would you classify this as? It's not really asparagus since I'm not dropping sets of 2 tanks, but I'm using fuel lines.

Some people occasionally call that onion staging, but it's basically the same as asparagus just in symmetry groups of 4 instead of symmetry groups of 2. If you're burning the engines of multiple stages simultaneously, and you have fuel lines from an early stage feeding a later stage such that the later stage is full of fuel when the early stage is dropped, and the dropped stage includes both fuel tanks and engines, then I'd call that some form of asparagus.

MoonMission1.

Edit out the #0 from your imgur link and the embedding will look nicer. Oh, and when you don't need the monopropellant in the capsule, you can get rid of it with tweakables for some extra delta-V!

Edited January 10, 2014 by tavert

[Deathsoul097]

Thank you, that is much better!

[larsmaehlum]

Commenting here so I remember to try this during the weekend. Will upload video if everything goes as planned

[tavert]

A 2-Kerbal design with more stages (still no asparagus, only fuel lines are between tanks within the same stage) does the job in 21.278 tons.

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(1+log_2(2))*2*100/21.278 = 18.8

[MagiMaster]

Wow. I thought my score looked low before. I'm not sure I can beat those scores with a 3 launch mission. (I'd need to keep the total mass of all 3 launches under 29 tons to tie tavert's score.)