Boat Momentum Efficiency Challenge

[foamyesque]

Hydrofoils? We don't need no stinkin' hydrofoils.

 

 

Momentum: 49531 tonne*m/s.

Part efficiency score: 1651

Power-fuel efficiency score: 55980

Funzies score: 6432

 

:v

[seanth]

38 minutes ago, foamyesque said:

Momentum: 49531 tonne*m/s.

Part efficiency score: 1651

Power-fuel efficiency score: 55980

Funzies score: 6432

 

:v

Actually, maybe you do need hydrofoils....

I get a different value for your Power-fuel efficiency value

• Thrust: 179kN
• Velocity: 90.6m/s
• Fuel usage: 7.70L/s

(179*90.6)/7.70 = 2106.16

Rest of the numbers look good.

Hey! This means with your two entries, you are in 1st place in two categories (and last place in one )

 

Edited July 20, 2016 by seanth

[foamyesque]

29 minutes ago, seanth said:

Actually, maybe you do need hydrofoils....

I get a different value for your Power-fuel efficiency value

• Thrust: 179kN
• Velocity: 90.6m/s
• Fuel usage: 7.70L/s

(179*90.6)/7.70 = 2106.16

Rest of the numbers look good.

Hey! This means with your two entries, you are in 1st place in two categories (and last place in one )

 

Eh? KER reports my thrust as 4756kN. 179kN is my torque.

 

EDIT: I mean, 179kN isn't even one Goliath running at full throttle, and I have 16 on there :p)

Edited July 20, 2016 by foamyesque

[seanth]

3 minutes ago, foamyesque said:

Eh? KER reports my thrust as 4756kN. 179kN is my torque.

DOH. I am an idiot. You are absolutely correct. I'm fixing your score on the 1st post now....

And I have to say, I am a bit confused that you got such great thrust. 16 Goliath, with an ideal thrust of 360kN is 5760kN. You're wallowing in that ship, but your thrust is 4756kN. That's 82% of optimal thrust. Doesn't seem like it should be that high, but you've clearly hit upon a design that is working!

Edited July 20, 2016 by seanth

[foamyesque]

12 minutes ago, seanth said:

DOH. I am an idiot. You are absolutely correct. I'm fixing your score on the 1st post now....

And I have to say, I am a bit confused that you got such great thrust. 16 Goliath, with an ideal thrust of 360kN is 5760kN. You're wallowing in that ship, but your thrust is 4756kN. That's 82% of optimal thrust. Doesn't seem like it should be that high, but you've clearly hit upon a design that is working!

 

The Goliath thrust curve drops until just before supersonic speeds, so you actually get a higher percentage of their rated thrust with slower boats. Or, I guess, if someone manages to build a supersonic hydrofoil, but that's gonna be tricky.

[seanth]

5 hours ago, foamyesque said:

 

The Goliath thrust curve drops until just before supersonic speeds, so you actually get a higher percentage of their rated thrust with slower boats. Or, I guess, if someone manages to build a supersonic hydrofoil, but that's gonna be tricky.

Huh. So...does that mean that a craft with two Goliath engines operating at 50% would have a better overall thrust than the same craft with a single engine working at 100%? Edit: no. derp. The performance is related to speed.

Unfortunately, I think the way the rules ended up the being formulated, there's only one way to beat a Power score, and that's by increasing speed.

Thrust and fuel consumption are pretty tightly linked, so as you increase your thrust you are increasing your fuel usage. There's just no way to decouple thrust and fuel usage that I can think of.

I wonder what scores would look like if we had gone with the original (mass*velocity)/Ls-1/#parts formulation. To the spreadsheets!

Person	Ship name	Momentum/L/s/part
(foamyesque)	We don't need no stinkin' hydrofoils	214.43
(foamyesque)	Unnamed	146.92
(Ezriilc)	Orca 5.3	143.64
(The_Rocketeer)	Soviet R	124.95
(seanth)	Franklin My Dear, I Don't Give A Damn	120.68
(seanth)	Crick in my Neck	113.54
(Ezriilc)	Orca 6	101.47
(seanth)	Crick in My Neck-full throttle	97.85
(Ezriilc)	Orca 3.4	64.20
(Ezriilc)	Sea Train	89.85
(Ezriilc)	Sea Train-depleted fuel	63.17
(SpannerMonkey(smce))	Challenge Cat	55.09
(seanth)	Watson Your Mind	22.22

I find the values for Crick in My Neck and The Sea Train of particular interest here, because those craft have two entries under two different operating conditions. Crick in My Neck scored better at lower speeds, even though the mass was essentially the same; probably due to better fuel efficiency at lower speeds. The Sea Train also scored better at lower speeds, but because the faster run had much less mass.

If we were to think about scoring this way, what sort of crafts would be able to tie with @foamyesque's  We don't need no stinkin' hydrofoils? To make it easy, let's lock in velocity at 90m/s and the fuel usage at that speed to 1.75L/s

You could equal that score with a ship that was 334 tonnes and 80 parts (the current average number of parts per ship), traveling at 90m/s and using 1.75L/s of fuel to do so.

Blarg. Maths.

 

Edited July 21, 2016 by seanth

[foamyesque]

14 hours ago, seanth said:

 

@foamyesqueThrust and fuel consumption are pretty tightly linked, so as you increase your thrust you are increasing your fuel usage. There's just no way to decouple thrust and fuel usage that I can think of.

 

There isn't one. Thrust/fuel consumption = Exhaust velocity, which is directly proportional to Isp. So the power efficiency rating is, functionally, about going as fast as you can with the highest Isp you can, which probably means goliaths with as little drag as can be managed. Somewhat remoter possibilities are Wheezleys or non-afterburning Pathers, but they need to be going significantly faster for the same score than a Goliath would.

Edited July 21, 2016 by foamyesque

[foamyesque]

And, since it is just a speed competition, looky here:

I make that a power-fuel efficiency score of 201560.7. (It subsequently left the water and became a plane :v)

[seanth]

11 minutes ago, foamyesque said:

And, since it is just a speed competition, looky here:

I make that a power-fuel efficiency score of 201560.7. (It subsequently left the water and became a plane :v)

WOW! That is amazing! I love it. Craft file available?

 

Edited July 22, 2016 by seanth

[foamyesque]

27 minutes ago, seanth said:

WOW! That is amazing! I love it. Craft file available?

 

 

Sure: https://www.dropbox.com/s/i8nsx0byxiaqzn4/Hydrofoil 2.craft?dl=0

I have another run that edged my speed slightly, but much as I want to break Mach 1 I can't seem to find a way to keep it in the water.

Score of 203989.9.

[seanth]

21 minutes ago, foamyesque said:

 

Sure: https://www.dropbox.com/s/i8nsx0byxiaqzn4/Hydrofoil 2.craft?dl=0

I have another run that edged my speed slightly, but much as I want to break Mach 1 I can't seem to find a way to keep it in the water.

Score of 203989.9.

It's just a thing of beauty. Scores are posted. You're officially in 1st in all categories, though different boats.

Edited July 22, 2016 by seanth

[Heffy]

Introducing the "Make KSP Great Again" fuel freighter, boasting a liquid fuel capacity of over HALF A MILLION! New to posting here, and I'm semi drunk right now so I don't want to do the math. Imgur wouldn't take my screenshot with the mass for some reason...sorry... You'll have to take my word for it, the mass is 3343.213.  Actual max speed after letting the ship go for a few minutes was 6.0 mps. And the consumption rate was actually about 2.72.  Wasn't about breaking the records, it was about building a BIG ship lol.

[The_Rocketeer]

So at what point does the 'boat-that-can-sometime-accidentally-fly' become a 'plane-that's-dipping-one-toe-in-the-water'?

[Ezriilc]

1 hour ago, The_Rocketeer said:

So at what point does the 'boat-that-can-sometime-accidentally-fly' become a 'plane-that's-dipping-one-toe-in-the-water'?

Well, anyone that's piloted a hydrofoil race boat will tell you, there genuinely isn't much difference - and neither do well when fully in the other medium.

[The_Rocketeer]

36 minutes ago, Ezriilc said:

Well, anyone that's piloted a hydrofoil race boat will tell you, there genuinely isn't much difference - and neither do well when fully in the other medium.

I don't think that's a very accurate answer. If a hydrofoil gets properly airborne, that's really bad news of the driver. If a seaplane comes in to land, that's not.

My point is that this seems to no longer be a challenge for boats, it's now a challenge for any vessel as long as it has part of a fin in the water. This interests me little.

[seanth]

3 hours ago, Heffy said:

Wasn't about breaking the records, it was about building a BIG ship lol.

That is a big ship. Take another screenshot showing the mass, # of parts, and the thrust and I'll list you.

[seanth]

1 hour ago, The_Rocketeer said:

I don't think that's a very accurate answer. If a hydrofoil gets properly airborne, that's really bad news of the driver. If a seaplane comes in to land, that's not.

My point is that this seems to no longer be a challenge for boats, it's now a challenge for any vessel as long as it has part of a fin in the water. This interests me little.

I'm inclined to agree. Maybe it's time to wrap up this challenge unless someone can think of a way to salvage it with rule tweaks or a reformulation of the scoring.

[foamyesque]

2 hours ago, The_Rocketeer said:

My point is that this seems to no longer be a challenge for boats, it's now a challenge for any vessel as long as it has part of a fin in the water. This interests me little.

It actually isn't -- you can't put a fin in the water at that speed without tearing it off. It has to >start< in the water, which means it has to be a boat and deal with all of the boat's problem's in accelerating up onto the foils.

[The_Rocketeer]

20 minutes ago, foamyesque said:

It actually isn't -- you can't put a fin in the water at that speed without tearing it off. It has to >start< in the water, which means it has to be a boat and deal with all of the boat's problem's in accelerating up onto the foils.

That's not really the point. Boats, even hydrofoils, do not use aerodynamic lift to raise themselves from the water, they use hydrodynamic lift and natural buoyancy. There's no way that the parts in contact with the water on your latest craft are producing the majority of the lifting force involved - most of it is probably body lift. Once a craft is lifting itself primarily with aerodynamics, it's no longer a boat - it's a seaplane, or possible an ekranoplan but KSP doesn't do ground effect to my knowledge.

I appreciate that the physical principles are much the same in any case, but in practice there are significant differences between hydroplaning and flight.

Edited July 22, 2016 by The_Rocketeer

[foamyesque]

14 minutes ago, The_Rocketeer said:

That's not really the point. Boats, even hydrofoils, do not use aerodynamic lift to raise themselves from the water, they use hydrodynamic lift and natural buoyancy. There's no way that the parts in contact with the water on your latest craft are producing the majority of the lifting force involved - most of it is probably body lift.

Have you seen what the actual boats for watercraft speed records look like?

 

 

The sustained average speed for the record is around 141m/s, to give you a context for how damn fast KSP hydrofoils go. Planes don't take off at Mach 0.9, generally, either.

Edited July 22, 2016 by foamyesque

[The_Rocketeer]

@foamyesque I'm not sure what your point is. The boat in the video doesn't use aerodynamic lift, it uses hydrodynamic lift generated by the planing attitude of the boat. If you point to the pitch stabiliser, you'll find that's actually creating aerodynamic downforce to hold the boat on the water. The boat rises out of the water because the water pushes it up, not because the air pulls it up. Air pulling would be flight. Water pushing would be float.

[foamyesque]

@The Rocketeer: My point is that the world's fastest boat is very slow compared to the speeds you can push a KSP hydrofoil to; once you get up to certain speeds aerodynamic body lift is just going to be a thing. For what it's worth, here's a screenshot of me (going faster than SoA) while the majority of my lift is hydrodynamic:

I'm thinking about doing some design revisions so's to get more aerodynamic downforce, but the wildly different operating regimes going from "displacement @ 5m/s" to "hydrofoil lifting at 70m/s" to "Mach 0.9 stable" make things tricky. The upswept nose, for example, gives me better lift out of the water at the transition speeds but actively pulls it up at high ones. Darby used a T-tail for pitch stability; I'm tinkering a bit with the rear canards I'm using for pitch trim and roll stabilization with the same goal.

The biggest hassle is actually the damn Goliaths. There can't be any downward motion as they clear the water or else they "splash down hard" and just evaporate.

[The_Rocketeer]

@foamyesque I don't know enough about how KSP deals with aqueous lift to speak with any authority, but I suspect that the majority of the lift force on those 'hydrofoils' is actually still aerodynamic - if the craft actually took off and became airborne (which it must be incredibly close to doing), I doubt the tails would be any shorter.

[foamyesque]

8 minutes ago, The_Rocketeer said:

@foamyesque I don't know enough about how KSP deals with aqueous lift to speak with any authority, but I suspect that the majority of the lift force on those 'hydrofoils' is actually still aerodynamic - if the craft actually took off and became airborne (which it must be incredibly close to doing), I doubt the tails would be any shorter.

 

If you look up at the max-speed screenshot you can see the difference; at more than double the speed, when they're mostly out of the water, the tails are so short as to be non-existant. That lift is almost all hydrodynamic; a self-stabilizing V-structure. A fully submerged T layout would be less draggy, but KSP's fly-by-wire stuff isn't adequate to the job of stabilizing it at that speed.

EDIT: Also, man, I posted the craft file earlier, you can test it out yourself.

Edited July 22, 2016 by foamyesque

[The_Rocketeer]

3 minutes ago, foamyesque said:

 

If you look up at the max-speed screenshot you can see the difference; at more than double the speed, when they're mostly out of the water, the tails are so short as to be non-existant.

Lol, in other words you freely admit that in your 'max speed' screenshot you are literally airborne, i.e. not floating, i.e. a seaplane, not a boat.