Some criticisms

I don’t think they &quotshould&quot add any explanation if they don’t want, nor that it’s that reasonable that anything is a linear function of anything.
You just need to know that

  • the more engine power a ship has (plus eventual engine efficiency bonus), the faster it goes;
  • the heavier the ship, the slower;
  • the more the cargo (so, the heavier), the slower the ship.
    (I’m assuming these three are implemented, I didn’t experiment that much with engines and ships, I just noticed the difference when I upgrade my engine wrt the starting one).

Beside these general rules, I don’t see why Failbetter should be -obliged- to tell more.
edited by Master Polarimini on 2/9/2015

Failbetter isn’t really obliged to do much of anything now that they have provided a working game, so that’s not much of an argument. If one gun does 10 damage and another does 15, I can map that directly to the amount of hull an enemy looses. But the speed numbers don’t directly map to anything. As is, I will not be purchasing an engine until I have a clear idea what it does. I simply can’t afford the risk.

While I agree that it’s not logically reasonable to assume that anything is a linear function of anything, intuition is often illogical. A good middle ground between outright explanation and keeping things as-is might be to use a different numbering system to display the engine stats – kind of like pH, but in reverse, I guess.

I agree with Dewar.

I don’t understand why the workings of a standard ship engine should remain obsfuscated to the point of being non-intuitive. More esoteric engines found on the far reaches of the Unterzee, sure, they can have hidden properties and all. But it’s very well reasonable to expect linear functions when the game doesn’t give you any reason to expect otherwise, particularly when other systems are precise to a fault.

Take combat, for instance. You have weapons which deal, say, 8-15 damage points, and the effect on a target is a loss of 8-15 HP per hit. Not 5-30 nor 2-12. And if I upgrade my guns, I know what kind of performance improvement I can expect.

So why can’t engines have a predictable effect? What’s the reasoning for breaking the game’s consistency in precise linear systems? If there’s a number on an item, even if it’s arbitrary, you expect it to be indicative beyond &quotwell, it’s better to an unknown amount&quot. If the number’s not going to help, then might as well get rid of it. Judging by pricetag is just as accurate.

You say that, but there are indeed esoteric engines found on the far reaches of the Unterzee, and having a definite number representing power - even if we don’t know precisely what that number means - lets us compare those engines with the ones found in the shops.

(Has anyone actually tried sitting down with a stopwatch and a lot of echoes and actually testing different ship/engine combinations for speed? Actually, I’ve got a rich savefile and a phone - back inna minute.)

This is the most there is at present: (Bug?) 1500 engine power same speed with default engine :: Sunless Sea General Discussions

RESULTS - from a standing start in Wolfstack Docks to the ship’s bow passing the southernmost point of the large rock south of Hunter’s Keep.

Eschatologue-Class Dreadnaught, Weight 5000.
With an Elderly Steeple-Engine, Power 800 - 48 seconds.
With a Caminus Yards &quotCompulsion&quot, Power 3500 - 27 seconds.

Lampad-Class Cutter, Weight 300
With an Elderly Steeple-Engine, Power 800 - 36 seconds.
With a Caminus Yards &quotCompulsion&quot, Power 3500 - 25 seconds

Conclusion of these preliminary tests: ship weight undoubtedly has an effect on speed, but a larger ship benefits far more from a larger engine than a smaller ship.
edited by Sir Frederick Tanah-Chook on 2/10/2015

So the effect of ship weight on ship speed is exponential or something?

I haven’t got the mathematical chops to interpret my own data, but what I’m taking away from that is that a small ship will be quick no matter what, but a large ship needs a powerful engine to get any decent sort of speed.

There are several likely-relevant numbers in the constants.json file. Taking Sir Fred’s data, adding to it, and plotting against those would allow you to both correlate and derive equations.

I suppose I didn’t express myself correctly. I meant esoteric engines can be allowed to have hidden qualities and non-intuitive workings, whereas mundane ones cannot. If the arbitrary engine power figure is only useful as a barely accurate means to compare different engines, then it’s a superfluous stat, as the item’s price (or sale price in the case of non-purchaseable engines) fills that role just as well.

Not really - those other engines might not be sellable, and, when they are, they have other bonuses that affect their sale price - they might, for instance, provide big stat boosts, or provide bonus fuel efficiency, while having a lower power level. Engine power might not be a simple “double the power, double the speed” equation, but it still lets us know which engines are more powerful versus which are useful in other ways.

It is worth pointing out that Compulsion has a COST of 5000, but an Engine Power of 3500. The 5000 power engine is the Impeller …

Quite right, of course! I’ve edited my post accordingly.

[quote=Master Polarimini]- the heavier the ship, the slower;

  • the more the cargo (so, the heavier), the slower the ship.
    (I’m assuming these three are implemented, I didn’t experiment that much with engines and ships, I just noticed the difference when I upgrade my engine wrt the starting one).[/quote]
    There seems to be an effect on acceleration related to cargo and weight, but I can’t tell whether it also affects max speed. Fred, your numbers strongly suggest the main issue is slower acceleration.

Efficiency bonus only affects fuel consumption, not speed.
edited by Olorin on 2/10/2015
edited by Olorin on 2/10/2015

For those people who have access to more expensive engines and have been doing testing (Thanks Sir Frederick,) can you confirm whether the same engine has the same fuel usage regardless of ship weight?

Edit: Nevermind, already posted at
edited by Dewar on 2/10/2015

Yeah, I’m just saying, as per Dewar’s example, if two cannons said they had 5 “damage power” and 10 “damage power,” and it turned out that was not only not the actual damage dealt, but eventually determined that the more powerful one was only 20% stronger, that’d be a bizarre and terrible labeling system for them.

Thanks to gregg, we now know that engine power actually does scale linearly to fuel consumption, so I’m much more content with knowing there IS a reason for the values given, and something you can easily and directly tell from them, rather than the values seeming arbitrary and confusing.

I wondered about that, but I took my Dreadnaught, put each type of engine on it, and pointed it at a long stretch of open water - and, no matter how long I let it go, the less powerful engine never reached the same speed as the more powerful one. And some preliminary tests involving running starts produced times that were narrower in their range, but still not identical.
edited by Sir Frederick Tanah-Chook on 2/10/2015

That makes sense to me. At a certain point, putting a more powerful engine on a small ship is going to be a really bad idea for its structural integrity. Great mental image, though.

(As an incidental data point - I don’t think I ever assumed the engine power was linearly related to speed. Like I could easily see a 2000 engine going 150% as fast as a 1000 engine because of engine weight. I didn’t know it was linear with fuel consumption though, so that’s useful for figuring out supplying needs.)

Given this is Unity, it actually wouldn’t surprise me at all if the Engine Power stats were the actual power values being fed into the physics system. Not thrust, but power.

This does a couple of things:

  • It makes achieved speed a function of energy – and v = sqrt(e/m), so you’ll need to quadruple the energy spent to double your speed.
  • In real life, things like propellers and wheels and feet produce a lot less force when they’re moving at nearly the same speed as the medium they’re pushing against, so whatever physics-thing they’re using might simulate that!
  • There’s almost certainly physics-drag, which can easily be exponential rather than linear.

Point is, that in real life doubling your horsepower does not double your top speed by any stretch of the imagination. And while physics has definitely taken some manner of vacation in the Neath, it wouldn’t surprise me at all if they were using a physics model that works on similar principles, since that’s useful for helping lend driving around a good sense of physicality without requiring the devs to do a bunch of stuff from scratch.

. . .

tl;dr - I’m fairly certain that if you upgrade your Engine Power from 800 to 1500, that is actually changing the physics-number of &quothow hard to push the boat?&quot from 800 to 1500, and that any complicated maths are part of the physics plugin rather than something Failbetter cooked up to obfuscate what the boat is actually doing. Ditto for weight!

And given that it’s physics, trying to back-calculate all that stuff to get you an effective top speed increase is…probably gonna be pretty complicated, and a tooltip that pops up and says &quotThis engine will give you a 21.3% increase in top speed!&quot feels pretty out of place.