Author Topic: "Standard" speeds for engine tech; an idea that really needs feedback  (Read 1186 times)

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Offline Iestwyn (OP)

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Quick caveat: I'm only barely getting back into Aurora after a few years.  I haven't even really been able to play yet; I'm still figuring out the classic resolution issues (I guess some things don't change).  Things might be VERY wrong here, so please let me know.

In looking at the designs in the Bureau, I notice that a common criticism is that designs are slow given their engine tech.  The assumed argument is that at a given tech, there's a kind of "standard speed" for most ships; any slower and NPRs at the same tech level will be able to dictate the engagement range.

One tip that I've seen is to dedicate a third of a ship's tonnage to engines (often slightly boosted).  Plugging that into the formula for speed and engine power suggests that the average ship would have a speed equal to the tech's EP per HS * 1000 / 3.

If that's true, then a possible list of "standard speeds" (with a lot of rounding) would be:

Conventional - ~70
Nuclear Thermal - ~1700
Nuclear Pulse - ~2700
Ion - ~4000
Magneto-Plasma - ~5500
Internal Confinement Fusion - ~6750
Magnetic Confinement Fusion - ~8500
Inertial Confinement Fusion - ~10,250
Solid-Core Antimatter - ~13,250
Gas-Core Antimatter - ~16,750
Plasma-Core Antimatter - ~20,000
Beam Core Antimatter - ~26,750
Photonic - ~33,250

I should say that I don't even know if this feels right.  I'm looking forward to literally anything you guys have to offer.  Thanks in advance!
 

Online Bremen

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #1 on: November 09, 2020, 09:26:17 PM »
Strictly speaking, I think the "standard" speed might be equal to the fire control speed at the same tech level. However I think most people aim for faster than that, because speed is so crucial to combat.
 
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Offline Iceranger

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #2 on: November 09, 2020, 10:56:25 PM »
There are many preference to this, so there is nothing wrong about your choice. I also define my fleet speed based on engine tech. The formula is similar to yours, basically engine tech's EP/HS rating * 500 km/s. This can be achieved with 40% engine with 1.25x power boost, or ~30% engine with 1.35x power boost.
 
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Offline Iestwyn (OP)

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #3 on: November 09, 2020, 11:05:42 PM »
Quote from: Bremen link=topic=12053. msg142823#msg142823 date=1604978777
Strictly speaking, I think the "standard" speed might be equal to the fire control speed at the same tech level.  However I think most people aim for faster than that, because speed is so crucial to combat.

That's. . .  so simple and easy.  I'll have to check in the morning and see how they compare.  Thanks!
 

Offline nuclearslurpee

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #4 on: November 10, 2020, 01:49:54 AM »
The approach I take for warships is to define a percentage of ship tonnage dedicated to engines for the fleet (may vary for fighters/FACs) and use the maximum engine boost at that tech level, since warships usually don't worry about fuel range that much the maximum boost is almost always optimal.

The techs for max EP modifier run out well before you're even halfway through the main engine techs, so the tech levels may not be exact in terms of what people consider TL1, 2, 3, etc. That being said, you can ballpark something like this using, for sake of example, 30% engine mass:

Tech Level 0: Conventional 1.0 EP/HS * conventional 1.0x modifier * 0.30 * 1000 km/s = 300 km/s
TL1: NTE 5.0 EP/HS * 1.25x modifier * 0.30 * 1000 km/s = 1875 km/s
TL2: INTE 6.4 EP/HS, 1.5x modifier --> 2880 km/s
TL3: NPE 8.0 EP/HS, 1.75x modifier --> 4200 km/s
TL4: INPE 10 EP/HS, 2x modifier --> 6000 km/s
TL5: Ion Drive 12.5 EP/HS, 2.5x modifier --> 9375 km/s
TL6: M-P Drive 16 EP/HS, 3x modifier --> 14400 km/s
TL7: IntCF Drive, 20 EP/HS, still 3x modifier --> 18000 km/s

After this the max modifier is capped at 3x, so the relative increase for the succeeding tech levels is not as sharp. You'll notice that the biggest percentage jump comes at TL5 and TL6 when the amount of the modifier jumps from 0.25 to 0.5 per tech level, which may be why you see people highlighting ion drives as a major tech breakpoint.

It seems to me that usually, the issues with speed on ship designs comes from designing to a specific tonnage and choosing the weapons loadout first, so settling on the engines first and fitting in whatever weapons you can on the remaining space ensures you have a good speed. Either too small of a space fraction for the engine, or forgetting to use the maximum modifier (not only do warships not need as much fuel/range compared to other types of ships, but extra fuel storage is usually less net tonnage than an inefficient engine) are probably the main reason you see a lot of designs that get criticized for low speed
 
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Offline Iestwyn (OP)

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #5 on: November 10, 2020, 02:19:40 AM »
That makes a lot of sense.  Out of curiosity, how do you define the tech levels?
 

Offline Zap0

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #6 on: November 10, 2020, 03:10:13 AM »
The speeds you show in your starting post look fine to me for the NPE-ION era from experience. A beam warship might want a little more, a missile warship can often do with a little less speed.

Always maxing the power modifier does not seem very flexible. What good does a warship if it can barely reach the asteroid belt and then go home? If it needs to be paired with slow tankers to go anywhere more than 1b or 2b away it loses the strategic advantage from it's speed. Max modifier designs like this can be viable (otherwise fighters wouldn't exist), but there'll be a bunch of downsides.

When designing warship engines I tend to look for their engine efficiency to be somewhere between, say, 30% and 130%. When designing a warship I'll have an idea of how big I want it to be and then start with the engines, filling anything from 20% to 50% of the ship with engines to start with.
 
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Offline froggiest1982

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #7 on: November 10, 2020, 03:33:25 AM »
When designing a warship I'll have an idea of how big I want it to be and then start with the engines, filling anything from 20% to 50% of the ship with engines to start with.

Agreed. So I start with what I want: Destroyer for instance 15,000 displacement. Then:

Armour
Engines
Fuel Std
Payload
Engineering
Fuel to round up tonnage
 
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Offline xenoscepter

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #8 on: November 10, 2020, 07:49:44 AM »
http://aurora2.pentarch.org/index.php?topic=10614.msg119799#msg119799
^I did a quick write up on this subject... kind of. This will help you calculate what speed you are getting for any given combination of EP and Ship Tonnage. From there you can figure out what a "standard" speed at any given tech level is if by "standard" you mean the average.
 

Offline Iestwyn (OP)

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #9 on: November 10, 2020, 09:21:37 AM »
Quote from: froggiest1982 link=topic=12053. msg142832#msg142832 date=1605000805
Agreed.  So I start with what I want: Destroyer for instance 15,000 displacement.  Then:

Armour
Engines
Fuel Std
Payload
Engineering
Fuel to round up tonnage

This is SO useful.  Thanks!
 

Offline nuclearslurpee

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #10 on: November 10, 2020, 12:15:23 PM »
That makes a lot of sense.  Out of curiosity, how do you define the tech levels?

Here I just went up one level of both techs per "tech level" starting from conventional. This might not be exact and people will define them differently, but in this case the RP requirement is pretty similar for the engine and boost techs at each "level". Notably, the way I did it gives you 4,000 km/s at NPE pretty easily with 30% engine mass, which seems broadly in line with the numbers I remember seeing here at that level.

If you do a default TN start, you'll automatically have NTE engine tech but not the 1.25x modifier tech, so you could define the tech levels relative to that in which case every modifier in my listing gets knocked down a level until you reach the 3x modifier.

Always maxing the power modifier does not seem very flexible. What good does a warship if it can barely reach the asteroid belt and then go home? If it needs to be paired with slow tankers to go anywhere more than 1b or 2b away it loses the strategic advantage from it's speed. Max modifier designs like this can be viable (otherwise fighters wouldn't exist), but there'll be a bunch of downsides.

Usually, a "smaller" engine with a higher boost modifier and extra fuel storage will be more tonnage-efficient than a bigger engine with a lower boost modifier and less fuel storage, because (a) fuel is pretty space-efficient, and (b) bigger engines require more crew spaces. This may not be a hard and fast rule but it seems to work in my experience. Admittedly, this approach is intended to work with a pretty well-developed fleet logistics arm (notably, pre-positioning tankers ahead of a planned offensive) but you can still get warships with 10-15b km ranges which is usually enough to jump into a hostile system, shoot everything with superior speed, and jump back to wherever your tanker is.

This might start to break down once you get into the high-powered engines at fusion tier and higher, since those are just so fuel-hungry in general, but usually by that stage of the game you should have a very strong logistics system to manage your big empire and you can be more specific in your ship designs to counter specific NPRs instead of relying on general principles/doctrines.
 

Offline Iceranger

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #11 on: November 10, 2020, 12:29:25 PM »
Usually, a "smaller" engine with a higher boost modifier and extra fuel storage will be more tonnage-efficient than a bigger engine with a lower boost modifier and less fuel storage, because (a) fuel is pretty space-efficient, and (b) bigger engines require more crew spaces. This may not be a hard and fast rule but it seems to work in my experience. Admittedly, this approach is intended to work with a pretty well-developed fleet logistics arm (notably, pre-positioning tankers ahead of a planned offensive) but you can still get warships with 10-15b km ranges which is usually enough to jump into a hostile system, shoot everything with superior speed, and jump back to wherever your tanker is.

It can be mathematically proven that the optimal engine:fuel ratio, in terms of the minimum space taken, is 3:1 in tonnage/HS, given a range and speed goal. Of course in the game, the engine size/boost and fuel size choices are all discrete, so the practical optimal may sway a bit from the theoretical 3:1 ratio, but not by much unless you hit a boundary of the above design parameters.

A corollary to this is that, if your engine:fuel ratio is much smaller than 3:1, it means you can use larger but less boosted engines with less fuel to achieve the same fuel range and speed while taking less space. On the other hand, if your engine:fuel ratio is much larger than 3:1, it means you can use smaller and more boosted engines and more fuel to save space.

Going with max boosted engine is almost never the optimal choice except for extremely fast and short-ranged ships.
 
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Offline Iestwyn (OP)

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #12 on: November 10, 2020, 12:42:17 PM »
If your engine:fuel ratio is much smaller than 3:1, it means you can use larger but less boosted engines with less fuel to achieve the same fuel range and speed while taking less space. On the other hand, if your engine:fuel ratio is much larger than 3:1, it means you can use smaller and more boosted engines and more fuel to save space.

This is FASCINATING. So glad someone can do all the hard math and give us the interesting conclusions.
 

Offline nuclearslurpee

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #13 on: November 10, 2020, 12:57:18 PM »
Usually, a "smaller" engine with a higher boost modifier and extra fuel storage will be more tonnage-efficient than a bigger engine with a lower boost modifier and less fuel storage, because (a) fuel is pretty space-efficient, and (b) bigger engines require more crew spaces. This may not be a hard and fast rule but it seems to work in my experience. Admittedly, this approach is intended to work with a pretty well-developed fleet logistics arm (notably, pre-positioning tankers ahead of a planned offensive) but you can still get warships with 10-15b km ranges which is usually enough to jump into a hostile system, shoot everything with superior speed, and jump back to wherever your tanker is.

It can be mathematically proven that the optimal engine:fuel ratio, in terms of the minimum space taken, is 3:1 in tonnage/HS, given a range and speed goal. Of course in the game, the engine size/boost and fuel size choices are all discrete, so the practical optimal may sway a bit from the theoretical 3:1 ratio, but not by much unless you hit a boundary of the above design parameters.

A corollary to this is that, if your engine:fuel ratio is much smaller than 3:1, it means you can use larger but less boosted engines with less fuel to achieve the same fuel range and speed while taking less space. On the other hand, if your engine:fuel ratio is much larger than 3:1, it means you can use smaller and more boosted engines and more fuel to save space.

Going with max boosted engine is almost never the optimal choice except for extremely fast and short-ranged ships.

Interesting! Do you happen to have a useful link that lays out the math behind this? I don't doubt you at all, but I'm curious how optimizing two different but related quantities in speed and range would consistently give a nearly 3:1 ratio regardless of the desired values.
 

Offline misanthropope

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Re: "Standard" speeds for engine tech; an idea that really needs feedback
« Reply #14 on: November 10, 2020, 01:08:38 PM »
sure, now include the cost of tankers and fuel infrastructure, and see if that "optimality" doesn't change a wee bit.
 

 

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