My experience has been that there are really a few splits.

1) Tankers: If you just need fuel and the ability to move it around, dedicated tankers are the answer. The good news is that these can be small, fast, and fairly inexpensive. I use them all the time for use in fleet trains and in moving fuel from colony to colony or bases. Use them all the time.

2) Harvesters: These are going to be big slow and expensive. No way of getting around it. To be honest, I tend to use these as a "set and forget" type of ship if they are just harvesters. If they are pure fuel barges, they can be slow and it really doesnt matter. Let them scoop and dump the fuel in a system. In many cases, where I have these running, they are dead last priority to upgrade. They just work. I honestly use these fairly often when I have a colony system with sorium gas giants. Its cheaper than building refineries, and lets the workers focus on stuff like construction factories first. A couple of harvesters, and a colony with a fuel transfer station and your set for fuel in the short term. Once system infrastructure gets built out, and the population can support its own refineries, I move these along to the next frontier colony. If the colony has huge amounts of sorium in gas giants, then these things tend to stay and they just run until I remember to upgrade them.

3) Mobile support: So these guys are purely situational. These are big, slow, very expensive but have massive fuel tankage, harvesting, fuel transfer, and large supply bays. I use them as "one stop shops" for ships out on the front/fringe of explore space. Instead of my scouts/surveyors having to run all the way back to a colony, they stop off at one of these ships for fuel and stores and then back to work. Honestly, these ships are purely situational. I use them when I have big long warp chains that have systems I dont really want to drop colonies in. In those cases, its worth it to drop one of these in a system with a gas giant and just leave them. Their duration times are huge, so they dont move often.

As far as efficient, it depends. If its just moving fuel around, tankers. If its skimming sorium and dumping it on an established colony, just basic harvesters work, and they arent too expensive, especially if fuel transfer is available from the colony. That kind of ship is harvesters, fuel tankage and small engines. They are slow, but comparatively cheap. My "set and forget" harvesters fall into this catagory.

As soon as you get into harvesting, refueling, and tankage the cost of the ships goes way up, as does the size. They are efficient, and in terms of overall expense, they can pay for themselves over the long haul as they dont need to be updated very often, but they are big and expensive and slow to build initially. They will need to be updated when engine tech changes, just to keep up with the frontier pushing out, but arent high priority.

Mobile bases or the "one stop shop" approach are NOT efficient. They are big, expensive, and need to be updated and resupplied regularly. I dont use these unless I really have to, and thats dictated purely by terrain. i.e. lots of poor/no mineral systems in a long chain. Otherwise, I try not to build these.

As far as tugs are concerned, I dont use them for harvesters very often, I think the dedicated ships are more efficient. Ditto for tankers. For the big mobile bases, then yes, the tugs are actually beneficial. Especially if they are going to be long term deployed bases. Getting rid of the engines and letting the tugs do the work is much more efficient. Engine failures eat up a ton of supplies, so getting rid of them cuts way down on the maintenance supplies consumed by the base, which extends their deployment time. Especially if the bases have shore leave facilities, at that point they become so big that tugs are definitely the way to go.

I tend to build fewer, but larger tugs rather than lots of small ones. I think they are more efficient, and it cuts down on the micromanagement. Tugs are for big projects, otherwise I build ships.

For fuel harvesters - I use slow harvester ships and designate one of the inner moons as a fuel dump.  I use tugs to deploy the harvesters to their station and to move them to their new station if the current giant runs out of sorium.  The engines are often recycled from scrapped ships as their only purpose is to move the harvesters from the gas giant to the moon and back once every year or so.  As long as they can make it from the gas giant to the moon and back in 5-10 days that's plenty fast. 

By doing this I don't have to worry about managing the harvesters - just "drag and drop" and the fleet will automatically dump fuel when it is full then go back to harvest more.  The colony serves as the system's refueling stop and can double as the collection point for mass drivers - the freighter can refuel while picking up minerals.   

My tugs are also tankers - fuel tanks are fairly light/small, so throwing an ultra large tank or two on the design doesn't slow them down by much. 

I find fuel harvesters useful to stage forward bases. For example, if I colonize a system to keep an NPR out, or I need a forward base to prosecute a war. In those cases, the fuel harvesters move in, drain the local gas giant and dump the fuel on the forward base. The forward base has the deep space sensors, defense, and refueling stations.

I also occasionally use them as fuel waypoints in very long warp chains. Those ships are big, with harvesters and refueling capability to gas up and resupply ships moving up and down the warp chain, just to shorten the logistical chain.

Otherwise, I dont use them much. They are big, expensive and slow.

I never use them as for me it's both a logistical and RP issue. I only ever mine bodies that have 100k or more of a mineral. Generally I want at least 300kt total of minerals on a body before I invest in mining operations run by the state. Everything below that I leave for the CMCs. We already know in the real world that most of the space mining will be conducted by civillian companies, so I like to keep things similar and just by the minerals from them. Logistically it is far easier to manage the build up of wealth and then spend that buying minerals. This also means I can focus all my investments into 500AM batches at a time for large scale mining operations.

Fuel is a different matter, I get 70% of my empire fuel from orbital stations. Big heavy things that are fitted with a single engine for <400kms speed, they lumber into place in massive fleets and sit their sucking dry entire gas giants. Then any sorium mined on bodies is used for industry instead. I have a single wolrd that is devoted to fuel production, after all worlds have got the sorium they require the surplus gets sent to my refinery world. For fuel transport it is a simple matter of tankers setup on repeat orders to collect and deliver, you do a little bit of math at first to set their speed so there is always plenty of fuel in the station tankes, then forget about them for the rest of the game.

Regarding fuel harvesters I prefer ships over stations since they can fly to a planet, dump their fuel and return all by themselves. No need to micro a tanker to come by every few years.

I use a classification system.

Priority class 1: System is rich in minerals and requires a long term commitment. These systems can be generally harvested in 100/150 years. I find automated mines to be ideal as some of the bodies are planets and you can use also mass drivers to have 1 collection point.

Priority class 2: System is rich in minerals but scattered. Small ships with orbital modules (not necessary fast) can mine these systems fairly easily. Again, to have a body to use as warehouse and also with a refuel station can help on the long term and the refuel station can be picked up on your way to a new system. The refuel station can be loaded with fuel from a colony or if there is any gas giant nearby you can harvest your own.

Priority class 3: System has a mineral which is important for the empire but the rest is not worth the investment. Usually, I handle these with a Tug and a powerful station in orbit. Fast deployment and fast mining. Once done move to a new one.

Furthermore, something I have seen not coming up is the investment in time to stabilize multiple jump points to get there with stations. I think it is important to fully understand the strategic implications of opening a way to your capital or inner systems. As I approach Aurora in a very "realistic" way and mostly challenge myself running not only multiple races but recently also 1 alien menace, I always weight in the possibility of stretching my defenses too much. If you add this into the mix, I am finding the combination Orbital Miners, Tugs and Tenders strategically more valuable for both Class 2 and 3 systems, while Class 1 gets the bonus only if possible to be colonized at some point. It's a kind of risk versus reward thing.

I forget; do station mines just put the minerals on the planet or do they need cargo space?

Orbital miners leave the extracted minerals on the planet.
I think if they have cargo space they fill that first but I might be wrong.
Fuel harvesters need to store it all on board.

Quote from: Borealis4x on May 02, 2021, 01:32:57 PM

why would you use mining stations when you can just use automated mines?

Orbital mining modules are the same cost as a normal surface mine.
Automated mines are twice the cost.

Orbital mining modules are 5,000T.
Automated mines require 25,000T of cargo space to move.

In other words, it is way more expensive to build and haul automated mines than to use orbital modules.

I forget; do station mines just put the minerals on the planet or do they need cargo space?