As Jorgen said, I should have mentioned the gallicite and sorium benefits of building large, low-boost engines; that is the primary benefit I am chasing in my game ATM. Since minerals are the primarily finite resource (second only to the player's time  ), and gallicite in particular can be a pinch point, this is a big deal.

Also, the reduction in engine cost significantly reduces the BP required, which in turn reduces the build time. Even though my Mk4 cargo ship is 250k size with 175k cargo space and 1700km/s, it actually builds FASTER than my Mk3 cargo ship which is 160k size with 100k cargo space and 2700km/s.

You also should think about speed, speed equal tonnage moved as well... also more speed means less production shortfall from facilities moved as well. Some fuel efficiency can be sacrificed for more speed. That is why I don't like too fuel efficient engines.

Quote from: nakorkren on November 24, 2021, 09:27:31 PM

Put the largest, most reduced power engine you can on your cargo and colony ships that your tech allows, and then build the largest ships your shipyards support. It's counter-intuitive, but large, reduced power engines actually are cheaper and less mineral intensive, and also build faster, so you can build more of them and negate the fact that they're (somewhat) slower by moving more cargo at a time.

This isn't really a general truth. For colony ships in particular, but also other commercial ships such as transports which have expensive mission modules, the engines are often a minor part of the total cost, so reducing their cost may not reduce the cost of the class very much. For example, a size-60 commercial ion drive with 0.5x modifier (375 EP) costs 93.75 BP. A 40,000-ton (approx.) colony ship at this tech level can cost roughly 1500 to 2000 BP, with four engines making up only 375 BP of that cost. A significant fraction but firmly the minority.

If we have the same engine with a 0.25x modifier (187.5 EP; 4000 RP for the tech, reasonable for early Ion tech) each engine costs only about 23.44 BP, and four engines cost 93.75 BP. This is indeed a 75% reduction in the cost of engines, but probably only a 15%, maybe 20% reduction in the overall cost of the ships. It's questionable I think whether it is worth building 15%-20% more ships which travel at only half the speed.

A better argument for this strategy would be the savings in gallicite, which can still be significant even though commercial engines are much cheaper than military engines already, and the savings of fuel if your refining or tanker capability is not too impressive. Especially later in the game, large fleets of very large ships can place significant demands on these two resources, along with duranium as always, and in my opinion this is a much better reason to prefer the lower-efficiency engines in the mid to late game.

It is worth noting, though, that the advice to build commercial ships as large as possible is generally very good as large shipyards are more efficient - a single large ship will take longer to build than a single small ship, of course, but it will be built more quickly than the same tonnage in multiple smaller ships.

A few remarks... larger ships is not more efficient to build in terms of population employed as it is more efficient with two slipways of 50kt each than one at 100kt. There are not as many benefit with building really large commercial ships as there are for military ships, even relatively small commercial ships can still use the most fuel efficient and large engines you can build and big engines is not a direct cost for commercial ships as they don't pay maintenance.

The benefit with larger ships is spending less cost for the armour belt. Good captains with logistics ratings that benefit loading/unloading rates. There are some cost benefit from building a larger cargo ship as there are some benefit to fuel storage, cargo holds etc... from my early game I just made two equal ships and the benefit are about 25% in cost. but that gap usually become smaller with increasing technology but will still be important. There are going to be rather small benefit with increasing the size from 125t to 250t cargo transport capacity for example, but more to gain from going from 25kt to 125kt...

One of the greatest benefit of low powered engines is definitely better fuel efficiency as fuel usage for commercial ships is a huge issue.

In general I use the smaller cargo ships for short trips with faster load/unload speeds and larger ships for long hauls and who don't need fast load/unload speeds as they spend most of their time travelling from point to point anyway. So I keep two main cargo classes around, one at 25kt and one at 125kt capacity. I then also have mineral haulers with even smaller cargo capacity.

There also are dubious reasons to upgrade commercial ships as well unless you have fuel problems rather than just building new ships to increase the capacity that way. There are a few things to think about here. When you ship a mine you are loosing mineral production while it is in transit so having a ship with twice the speed will cast you mineral production as well as probably more fuel as the engine is less efficient. So... upgrade your ships with careful consideration and not too often.

Put the largest, most reduced power engine you can on your cargo and colony ships that your tech allows, and then build the largest ships your shipyards support. It's counter-intuitive, but large, reduced power engines actually are cheaper and less mineral intensive, and also build faster, so you can build more of them and negate the fact that they're (somewhat) slower by moving more cargo at a time.

This isn't really a general truth. For colony ships in particular, but also other commercial ships such as transports which have expensive mission modules, the engines are often a minor part of the total cost, so reducing their cost may not reduce the cost of the class very much. For example, a size-60 commercial ion drive with 0.5x modifier (375 EP) costs 93.75 BP. A 40,000-ton (approx.) colony ship at this tech level can cost roughly 1500 to 2000 BP, with four engines making up only 375 BP of that cost. A significant fraction but firmly the minority.

If we have the same engine with a 0.25x modifier (187.5 EP; 4000 RP for the tech, reasonable for early Ion tech) each engine costs only about 23.44 BP, and four engines cost 93.75 BP. This is indeed a 75% reduction in the cost of engines, but probably only a 15%, maybe 20% reduction in the overall cost of the ships. It's questionable I think whether it is worth building 15%-20% more ships which travel at only half the speed.

A better argument for this strategy would be the savings in gallicite, which can still be significant even though commercial engines are much cheaper than military engines already, and the savings of fuel if your refining or tanker capability is not too impressive. Especially later in the game, large fleets of very large ships can place significant demands on these two resources, along with duranium as always, and in my opinion this is a much better reason to prefer the lower-efficiency engines in the mid to late game.

It is worth noting, though, that the advice to build commercial ships as large as possible is generally very good as large shipyards are more efficient - a single large ship will take longer to build than a single small ship, of course, but it will be built more quickly than the same tonnage in multiple smaller ships.

Really wish NPR would use reduced size ASM launchers. I have completely dropped AMM because they don't, no point on wasting galicite on them when a simple railgun or gauss turret on every ship will negate any NPR ASM.

i think i'd like to see your work there, dr slurp. 

gonna hafta disagree with you on one point, somebody.  a dash of AMM support can make a big improvement in your ability to weather a serious alpha strike.  reduced size AMM launchers fit the niche better, if you're heavily committed to point defense.

A. My "rules of thumb" are few. Here are some of them:

For commercial ships:
1. Engines should usually be ~40-50% of the size of the ship. Why so large? Engine cost is proportional to the square of its power rating, up to 100% power, and so - for most commercial ships - it pays to drop the rating and upsize. Other advantages include: faster construction of ships that are cheap compared to their size, more fuel-efficient engines, and reduced engine research costs.

2. Look for opportunities to off-load the engines to dedicated tugs. For starters, anything that stays in one place for years at a time really ought to be a station.


For warships:
1. Most warship designs benefit from a focus on both a single mission and a single combat range. Field ships that know what they're about.
1a. That is not to say that putting point-defence on a beam battleship is wrong - it's not. However, if you put most of your point-defence on dedicated ships, you can tailor fleets to either be better at stopping missile spam, or better at lighting up enemies, depending on local opposition. Indeed, you can send in the point-defence craft (or heavily shielded and/or armoured stuff, whichever) to beat off the missiles, with the beam boys kept safely out of trouble until things settle down.
1b. Same story with combat ranges. Move weapons having sufficiently different ranges to different ships. Move the ships to their optimal combat ranges - when conditions are favorable.
Warning: adopting this proposal, while it makes ship design easier, does mean that you need to be more mindful of both fleet organization and battlefield positioning.

2. Look for ways to off-load non-mission components and costs to other ships or stations. Your ship design might not need...
a. A full sensor suite. Sensors are among the most expensive items around for their size, and you only need to see the enemy once, so be smart about how you achieve redundancy.
b. Armament (especially if expensive) that doesn't carry out the primary mission.
c. Luxurious deployment time, multi-year maintenance life, abundant fuel, or quite that many missile reloads. Why burn fuel carrying more fuel?
d. Engines. If it doesn't have to move often, can a tug tow it around? Even if you do want it to move, can you park it behind a jump gate or Lagrange point and wait in ambush? Or just give it extra long-range missiles and hit first?
e. Heavy armour. At high tech levels, shields are king - as pointed out previously by nuclearslurpee.
f. Jump drives. Alternatives include dedicated jump squadron ships, unarmed jump ship support, or building a gateway.

3. For mobile warships, start with engines totaling 30% of the mass of the ship ... but then focus on the mission, not the rule. Reduce size (down to 20-25%) for slower ships, and also for lower-range ships with little need for fuel and thereby reduce costs. Increase size (up to ~40%) for faster ships, and also for ships needing more range.


B. Considering the OP's examples of advice others might proffer:

"warships should be 25% engine": My warships are either fast or slow - and they know which one they are. If fast, they have something like 30% to 45% of space devoted to engines. Superior speed means a better chance of imposing your preferred combat range on the enemy, and that might be half the victory right there. However, I also build a lot of "monitors" - warships with puny engines (often ~20% of total size) that tank and dish out a lot of damage for their cost.

"the ideal engine-to-fuel ratio is 3:1": I seldom put anything like that amount of fuel on my ships, because they either will (almost) always have tanker support (mobile ships), or hop from station to station (defensive ships). Exceptions might include survey ships, scouts, and long-range raiders - but even for these I tend to find ways to get a tanker involved.

"4 layers of armour for every 4k tons": For me, armor is all about the mission (and the combat range). Early on, I put a lot of armour on. Later, it's mostly about the shields.

"20b km range is enough for most warships": Range on my warships varies dramatically. 20b km would be at the upper end for my "typical" design, but I have had occasion to go much higher for armed raiders and convoy protection ships.


C. Considering a few Rules of Thumb from other posters in this thread:

Jorgen_CAB:
"I usually divide up war ships in terms of mission tonnage and none mission tonnage. Mission tonnage is weapons, magazines, hangars and sensors while the rest is armour, engines, fuel, crew quarters and engineering sections. If you can have about 40-50% mission tonnage you are  probably alright for a balanced main capital or escort warship.":
I'd second this thinking.

Lord Solar:
"15% of mass weapons on a warship."
I would almost never have so few weapons on a warship. My warships are born so that others might die and might easily devote 30-40% of total space to either "open fire" or "time to reload" (with apologies to Schlock Mercenary).

nuclearslurpee:
Agreed with most, especially on shields, maint. life, and armor. One point of difference is with missile design; there are major advantages to large, multi-warhead missiles, the most important of which are range and closing speed.

xenoscepter:
Sage advice on always having at least two engines.

 --- I always put at least 3 layers of armor on a warship except in extraordinary cases.

 --- I tend to put 1 full Engineering Space per 1,000 Tons. This varies on a ship to ship basis, but it's my yardstick... Anything above or below is measured relative to it.

 ---- My carrier's should have enough fuel, MSP, and ammunition for at least three sorties. The logic of this being, 1 sortie of attack, 1 sortie of pursuit, 1 sortie of opportunity.

 --- Non-carrier vessels with parasite craft carry enough fuel, ammo and MSP for at least one sortie, though there are usually exceptions for fuel-hungry fast scouts or short range crafts where 5,000~10,000 litres can be tantamount to 6 or 7 sorties.

 --- Two engines on anything military, sans stations of course. It sucks to be stranded.

 --- Enough MSP to battle damage repair the most expensive component at least once, preferably thrice. Varies a lot on a ship to ship basis, but this is my yardstick.