"How you use it that counts": Most Mass on Smallest Engines

[Blue]

Considering the recent challenges of Payload Fractions, thrust to weight ratios and whatnot, I was thinking about if the thought driving those challenges were turned around a bit: say, landing instead of taking off.

Therefore, the "How you use it that counts" Mass to Engine Fraction Challenge.

The objective is to land the heaviest craft you can on another world, using the smallest, and fewest, engines you can. Or, simply land with the largest possible mass you can, using rocketry only.

This isn't payload fraction or thrust-to-weight. This is final-mass-to-engine-size. Score is dictated by your ship's final mass once landed on the surface of another world (multiplied by the difficulty of that world, see below) as a ratio of your engine's size score. The Starting Position of your vessel is in orbit around your target world. It matters not how your lander gets to that location, since the thing that matters is the final mass resting on the smallest engine(s). In regards to stages, see below as well.

Since this is a rocket challenge, Lithobraking, Parachuting and Aerodynamic parts such as wings, are against the spirit of the challenge, and entries utilizing those things will not be counted.

Each engine you use on your lander adds to your engine score:

(These points are subject to change as this challenge is refined for balance.)

80 points - Rockomax Mainsail

40 points - Rockomax Skipper

35 points - LV-T30

32 points - LV-T45

30 points - Rockomax Poodle

20 points - TurboJet Engine

20 points - Basic Jet Engine

20 points - Toroidal Aerospike

20 points - LV-909

16 points - Rockomax Mk.55 Radial

15 points - LV-N[uclear]

8 points - Rockomax 48-7S, Rockomax 24-77

3 points - LV-1, LV-1R

1 point - PB-Ion

1 point - Place-Anywhere 7 Linear RCS Port

1 point - RV-105 RCS Block

Due to the difficulty of trying to balance the scoring for use of solid fuel engines for thrust and weight, and also considering the intrinsic difficultly in landing using them, I have decided to not include them in this challenge. They count towards your Engine Score, but if you stage them, they do not count towards your Final Mass.

40 points - Rockomaxx BACC SRB

25 points - RT-10 SRB

9 points - Sepratron I

Mass is straightforward. You can see your vessel's mass in the Map Screen from the little "i" tab.

However, Mass is also multiplied by the gravitational and atmospheric difficulty of the world you land on. If you land on an easy world, your mass will remain unchanged, or negatively affected. If you land on a hard world, your score will increase ()

Thus, Final Mass is determined by multiplying your ship's final mass by the gravity difficulty of the world you land on. Landings must be powered, and cannot have parachute assistance.

World Scores

(These points are subject to change as this challenge is refined for balance.)

Gilly x 0.25

Pol x 0.75

Bop x 1

Minmus x 1

Ike x 2

Dres x 2

Mun x 2

Eeloo x 3

Vall x 3

Moho x 3

Duna x 4

Laythe x 5

Kerbin x 5

Eve x 6

Tylo x 15

(These multipliers were calculated on the comparison of Minmus's gravity being 1, and then rounded and adjusted for balance.

Changed: increased Gilly and Eeloo, decreased Duna, Laythe, Kerbin, Eve and Tylo, reordered according to point multiplyer.)

In regards to stages, you can have them as you please in whatever manner you wish, but be aware that the Final Mass includes only what is on the ground when all is said and done, but the Engine score includes all engines used for the course of your landing (even if they were jettisoned).

So here's my example entry, to prove it's possible and fun!

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My score for landing an 18.58t vehicle on Minmus (gravity score 1.0) with only one Rocko-48-7S (8 engine points):

(18.58t x 1) / 8 = 2.3, which is my final score.

It's not the size that matters, it's

"How you use it that counts" Mass to Engine Fraction Challenge Leaderboards:

Stock Engines

1. Dave Kerbin - 7.8 (124.9 tons on Kerbin with 1 Mainsail)

2. Johnno - 4.2 (16.7 tons on the Mun with 1 Rocko. 48-7S)

3. Blue - 2.3 (18.58 tons on Minmus with 1 Rocko. 48-7S)

4.

5.

Mod Engines

1.

2.

3.

4.

5.

For mod engines, I'll probably have to come up with a figure for it comparing to stock engines of the same sort.

Good Luck!

(PS: This is my first challenge I believe I've made, so any critique of my game theory or challenge itself is welcome.)

Edited November 14, 2013 by Blue

[TheAwer]

In regards to stages, you can have them as you please in whatever manner you wish, but be aware that the Final Mass includes only what is on the ground when all is said and done, but the Engine score includes all engines used for the course of your landing (even if they were jettisoned).

You should define "course of your landing" more clearly. Maybe it could be the engines that landed on or crashed into the planet? That may be difficult to track though.

Great challenge though!

[Kasuha]

I believe aircraft wing parts should be excluded too. Otherwise you can land on any planet with atmosphere with the smallest engine or even just RCS thrusters.

[sgt_flyer]

Be careful with atmospheres - you will be able to land on eve with way much more fuel remaining than on tylo, for example ex, on tylo, you have to burn around 3000 m/s of delta-v to land (and as you need to bring that kind of fuel, you need an engine capable of a twr > 1 - maybe not from the start, but at least for a good part of the landing) - whereas at eve near sea level , way much less delta-v for a powered landing is needed - i think you could even land safely with a twr < 1 - you only need to slow down enough from 60 m/s of terminal velocity near sea level.

So in the end, a tylo lander will spend most of it's fuel for the landing, weigthing much less (and if you take additional fuel, you'll need to upgrade the engines) whereas on eve, you can come in with a lot of fuel, and just enough engines to slow down a few hundred meters before landing - and you will spend almost no fuel for that.

I'll try to make an example showing the problem

Edited November 13, 2013 by sgt_flyer

[TheCanadianVendingMachine]

So, Gilly is 0.1x score. But what if it is with a mainsail?

[Dave Kerbin]

Due to the difficulty of trying to balance the scoring for use of solid fuel engines for thrust and weight, and also considering the intrinsic difficultly in landing using them, I have decided to not include scoring for them. So it doesn't help your score to use them.

Is that worded correctly? If solid boosters are not factored in then it seems they can provide a lot of thrust for 'free' without reducing your final score. Yes it is very difficult to land with only solid fuel boosters (though it has been done), but it is not nearly as difficult to land using mostly solid boosters - perform all but the final braking using a series of solid boosters. Should solid boosters be disallowed unless a specific value can be determined?

There was also the question about "course of your landing". Maybe you should clarify that you begin from a stable orbit (any transit stages can be ejected here without cost) and then you begin your landing with whatever engines are attached to the ship at that time. So the score is Final Craft Mass times World Score divided by Orbital Engine Score.

As far as game theory goes could someone do a sanity check on my assumption: Since the weight of the engine (if we don't eject it) is counted as payload for scoring we can use its raw thrust as a linear measurement of how much total payload it could theoretically land (in order to slow down it must be able to overcome the acceleration due to gravity, so T/W must be greater then 1 at some point during the process). With that number we can work out a point per ton value for each engine, with higher values being worse (since our final payload score will be divide by it). The best engine by far seems to be the Mainsail which can score 60 times more then the two worst (LV-1 and PB-Ion).

Anyway, I'll see if I can find a third option for a high scoring lander that doesn't need to exploit the engine score table.

[zekes]

That's cute.

35 tons, x4 60N Nukes. TWR of better than 1 on Duna, Is able to get to Duna, land, and return without refueling.

[Dave Kerbin]

That's cute.

35 tons, x4 60N Nukes. TWR of better than 1 on Duna, Is able to get to Duna, land, and return without refueling.

Is the mass 35 tons after landing or while still in orbit? Does the mean it scores (35 x 6) / (4 x 15) = 3.5 points

[zekes]

Is the mass 35 tons after landing or while still in orbit? Does the mean it scores (35 x 6) / (4 x 15) = 3.5 points

It's like 60 in orbit, landing you ditch the Transfer Fuel Tank and land at about 35-36 tons.

[Johnno]

35 tons, x4 60N Nukes. TWR of better than 1 on Duna, Is able to get to Duna, land, and return without refueling.

It appears however that you've used parachutes to land which automatically disqualifies you from entering this challenge.

The fact that you have a TWR better than 1 just means you potentially could do a powered landing, unless you actually do so you're not eligible for this challenge.

Please read the challenge rules carefully before entering.

[Johnno]

Here's a quickie entry I made, craft design similar to Blue's.

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Landed mass: 16.73 tons

Engine: Rockomax 48-7S (engine score 8)

Location: Mün (multiplier 3)

Final score: (16.73 x 3) / 8 = 6.27 ~ 6.3

Edit:

After looking over the list of engines and pondering designs I'm inclined to suggest that engines simply be scored by thrust. With drop tanks that don't count for scoring in any way fuel efficiency isn't necessary.

Also even though radial engines are listed as "with greater difficulty" it's not all that difficult to just use one, placed below the craft in a way that ensures a centered thrust aimed straight down, like this:

With that design and the current scoring it would be possible to land slightly over 70 tons (two full orange tanks) on Mün with a single Mk55 radial engine, getting a final score around 20. Even if you're forced to use several radial engines the way they're scored now (at least the Mk55) would simply mean you add more mass onto the craft and get it down for a higher score. Two Mk55 engines could land roughly 146 tons on Mün, scoring 21.9 or so.

I also agree with what's been mentioned about locations with atmospheres (and aerodynamic parts at that).

Edit#2: Mathwise, a single mainsail landing ~900 tons on Mün, score 54.

Edited November 13, 2013 by Johnno
Additional stuff

[Dave Kerbin]

Since there has been no word on solid boosters (which could allow a divide by zero score) here is a basic run of the third option for high scoring landing. After some low altitude testing to see that the design worked I put on a big booster (and it wasn't enough to get into stable orbit, so I attached some solid boosters for the second attempt) and managed a landing on the first attempt.

3 Kerbals

Landing on Kerbin starting from 70km x 70km orbit

No solid boosters on lander

No aerodynamic parts

No parachutes

Landed mass 3.5t

One Place-Anywhere 7 Linear RCS Port

Ship is launched into 70km orbit, last launch stage is ejected and the main lander engine is fired up.

About 7 minutes of burn time is required to line up the landing path.

Lots of space to ensure a landing on relatively flat terrain, no chance of a water landing.

Getting orientation correct

Landing systems activated

And that is how a kerbal lands

Edited November 13, 2013 by Dave Kerbin
Agree with Johnno

[Johnno]

As the challenge rules specify powered landing I think lithobraking shouldn't be allowed at all, it's not really in the spirit of the challenge.

[Dave Kerbin]

Ok, as I mentioned back on page 1 certain engines are better simply based on the score assigned to them. From a meta-game perspective the Mainsail in particular is almost twice as good as the skipper in terms of its theoretical maximum score. The bodies are also biased but not nearly as much. Ignoring the atmosphere (which is more of a piloting and planning challenge) and going with a mathematically 'perfect' craft the two stand out bodies for best score are Tylo and Eve. Half of the remaining bodies are roughly equal and a second group (Bop, Vall, Dres, Ike, Mun) are about 10% less effective then the main group for maximum scoring, though most are relatively easy to land on. The only body that seems specifically bad for scoring is Laythe. Now unlike the engines, where the best engine was about 60 times better then the worst, Tylo is only about twice as effective as Laythe, making it a much tighter field.

Anyway I wasn't going to travel far and I made some quick calculations to come up with the weight I wanted to put on a single mailsail to land on Kerbin. I didn't quite max out the weight since I'm flying without any mods and so a little margin of error was needed. I went through 3 designs and surprisingly getting a landing at the correct speed was pretty easy flying by the math (resulting in a successful orbit to ground flight on the first attempt). The hard part was building landing legs that didn't immediately tip over the ship after it touched down. Since even the large landing gear isn't big enough to reach past a mailsail I had to extend them with girders.

My first design didn't bother with real lander legs at all, I just used those Modular Girder Adapters to give the girders 'feet' to rest on. This design never even left the ground as the whole structure would constantly wiggle on the launchpad.

The second design replaced the feet with proper landing gear and the first few low altitude flight tests worked fairly well - the powered landing went well almost everytime (the problems came when I forgot a step) but the lander would tip over, and weighing over 100 tons, smash into the ground and explode.

The third design changed the fuel tank placement in order to drastically lower the landers center of gravity. I replaced fuel tanks in the center with smaller T800 tanks attached to each of the lander leg girders. This design was fairly robust though even with 12 landing legs in total they struggled to hold up the weight of the ship and sunk into the ground. Retracting the legs while on the ground was impossible, since as soon as the weight of the craft was shifted it would break off whichever leg was unfortunate enough to be on the side it was tilted to, usually resulting in a complete collapse and lots of explosions.

Getting it up into orbit was the next challenge. I build lean ships so an orbiter that weighed about 150 tons was out of my league. After a few attempts I just stuck a big booster under it and hooks up fuel lines so that the orbiters own tanks could get it up. I added a docking port to the top so that it could be refueled back to its original mass in orbit.

The ship on the left is one of the refuelers, these where all deorbited before landing. The four T800 tanks that have solar panels on the lander are fuel for deorbiting, and get ejected after even though they'll still be more then half full. That's because their mass is not accounted for in the landing calculations.

After fueling the tanks are locked so that only the deorbit tanks can be used. We make a little burn to line up a nice grassy landing site. We should come down somewhere between the coast on the left and those mountains after the atmosphere slows us down. The extra weight is ejected and final landing prep is made: Fuel tanks needed for the landing are unlocked (we will burn from the center tanks only), engine is locked and thrust set, alignment is made for a vertical touchdown.

The next critical point in the landing will be made from the cockpit view. I have an action group to switch on the engine (at the preset throttle) and lower the landing legs when the radar altitude reachs the correct point. When the needle hits 1500m from the actual ground everything will be started.

With a single continous burn we slow down. Our T/W isn't a lot more then 1 (though it goes up as we burn fuel) so the ground is still coming up very fast.

We touch down with a small bounce. There was a good deal of lateral velocity but the legs held and stop wobbling in a few seconds. They are compressed to the maximum on the side we where moving into, but the mission report shows no breakage. The landing used a little less fuel then in testing - I was a fraction later in engaging the engine and that ate up my entire safety margin (in testing there was a small margin where thrust could be reduced half a second before touch down to finely set speed, in this landing we just barely made it).

Final score: Kerbin 20, Mass 124.99, Engine 50

(124.99 x 20) / (50 x 1) = 49.996

[sgt_flyer]

@dave kerbin

yes, that 's a similar technique i thought about for eve. - which can be even more effective there. - basically, for having a 1.1 twr on eve with a mainsail, you will have a craft weighting around 81 tons.

As the atmosphere slows you even more than kerbin's, you only have to slow down from 60 m/s (terminal velocity above sea level) - so you can start braking even later than on kerbin. Even if you burn a few tons of fuel for the landing, you'll still have a score around (or more) than 60.

(Ex, you burn 3 tons of fuel for landing, you still have 78 tons on eve's surface - giving you a score of 62.4.)

Yup : i think the engines / planet scoring dhould be slightly tweaked

[Dave Kerbin]

You'll probably burn more then 3 tons, even with my dumb luck to get the burn spot on it still went through 15 tons of fuel in the 30 second panic burn. Earlier testing where I managed a bit of a safety margin resulted in 18 tons of burned fuel.

My biggest reason for doing it in an atmosphere was that it lets you determine the velocity you will be traveling when you reach a specific altitude ahead of time (not the sea level altitude but the true radar altitude above the ground). Unless you can find a really flat area with a known altitude (maybe the salt 'sea' on Minmus would work) you're faced with too many real time calculations to determine exactly when you need to start burning if both the altitude and velocity keep changing in relation to each other. In an atmosphere you hit terminal velocity and stay there, so you can simply plot your acceleration curve ahead of time and know the exact height above the ground where you need to start burning so velocity and height hit zero at about the same time.

[Blue]

Yeah sorry I couldn't get back to you all sooner. No excuses :'(

I believe aircraft wing parts should be excluded too. Otherwise you can land on any planet with atmosphere with the smallest engine or even just RCS thrusters.

You are right. I almost never build or fly aircraft in this game, so it makes sense that I'd forget about excluding those. This is supposed to be a rocketry challenge.

So in the end, a tylo lander will spend most of it's fuel for the landing, weigthing much less (and if you take additional fuel, you'll need to upgrade the engines) whereas on eve, you can come in with a lot of fuel, and just enough engines to slow down a few hundred meters before landing - and you will spend almost no fuel for that.

I had an earlier model that had different point awards for planets, rather than simply being factors of their gravity. I think I'll change the World Scores.

So, Gilly is 0.1x score. But what if it is with a mainsail?

Then your homework for next Wednesday is to land an Empire State Building or two on that engine.

That's cute.

35 tons, x4 60N Nukes. TWR of better than 1 on Duna, Is able to get to Duna, land, and return without refueling.

You'd only be awarded a score if that landing you managed without parachutes, bub.

Edit:

After looking over the list of engines and pondering designs I'm inclined to suggest that engines simply be scored by thrust. With drop tanks that don't count for scoring in any way fuel efficiency isn't necessary.

Also even though radial engines are listed as "with greater difficulty" it's not all that difficult to just use one, placed below the craft in a way that ensures a centered thrust aimed straight down, like this:

With that design and the current scoring it would be possible to land slightly over 70 tons (two full orange tanks) on Mün with a single Mk55 radial engine, getting a final score around 20. Even if you're forced to use several radial engines the way they're scored now (at least the Mk55) would simply mean you add more mass onto the craft and get it down for a higher score. Two Mk55 engines could land roughly 146 tons on Mün, scoring 21.9 or so.

I also agree with what's been mentioned about locations with atmospheres (and aerodynamic parts at that).

I see. I'll change the engine score of radial mounts to be identical to their node-connected counterparts.

Even so, I'll reiterate that I'll revise the world scores. I knew it was going to be hit-and-miss from just putting up some numbers. In the words of Cave Johnson, "Throwing science on the wall and seeing what sticks." Which means, upon revision, everyone's scores are going to be different.

Since there has been no word on solid boosters (which could allow a divide by zero score) here is a basic run of the third option for high scoring landing. After some low altitude testing to see that the design worked I put on a big booster (and it wasn't enough to get into stable orbit, so I attached some solid boosters for the second attempt) and managed a landing on the first attempt.

Lithobraking (controlled or uncontrolled) is against the spirit of the challenge in the same way wing-assistance in atmospheres is; Johnno presumed correctly.

Even so, my plan was to also give a number to solid rocket motors which also counted into your Engine Score (which would do you a disservice if you staged them before landing.)

I'm going to edit the OP now.

___________________________________________________________________________________________

You guys' critiquing the game balance is of great help!

The plan is to have a curve of difficulty so that one can actually choose, rather than mathematically identify the ideal, of what they want to land on. For example, why I chose to make Laythe and Kerbin the same for the gravity multiplier is that Kerbin is easier to access, but Laythe now awards a higher score proportional to its gravity and atmospheric difficulty. Tylo has also been boosted a bunch because if its special challenges.

In all honesty I sort of made this challenge to see if a non-cheating screenshot could come into existence of someone landing on Tylo using an Ion engine to land a large orange tank

Edited November 14, 2013 by Blue

[Blaster]

...

In all honesty I sort of made this challenge to see if a non-cheating screenshot could come into existence of someone landing on Tylo using an Ion engine to land a large orange tank

If someone can manage to do that, they win KSP, hands down.

[Dave Kerbin]

If someone can manage to do that, they win KSP, hands down.

Yeah, mathmatically an ion engine just can't land on Tylo, the ion engine's mass alone is far too much for it to overcome Tylo's gravity. And that's before you add the xenon tank or solar panels or any payload.

Unfortunately I don't think there is a lot of room for competitive entries. There are only 2 good ways to post a new high score. The first is with a Mk.55 Radial on Dres, Eeeloo or Ike which has a very small chance of being able to break the record. The second is a landing on Tylo for which there are a handful of competitive options, though it will really be about who does the skipper (which is probably the best balance for points and reasonable weight) and then the mainsail which will have to be heavier then my Kerbin lander. Once the mainsail has been done properly on Tylo that pretty much finishes it - to post anything higher you would need to build a Gilly lander in the 2500 ton range just to inch by the Tylo score.

[Johnno]

Unfortunately I don't think there is a lot of room for competitive entries.

This is why I haven't bothered with any more entries. I build a Kerbin mainsail lander that beat yours by a few tons, but couldn't be bothered finetuning it to the max. The way scoring still is it's going to be a mainsailfest no matter where you go, it simply outscores any other engine(s) with the thrust vs scoring.

If atmospheric planets were removed from the scoring list and engines scored by thrust then it would be up to what you wanted to land where to get fairly competetive scores. But really right now it's just about taking the heaviest thing you can land with a mainsail.