c)Have mining ships any advantage against auto mine?
Mining ships are much more efficient to build, and much easier to move around.
One orbital mining module does the same amount of work as one auto mine.
One auto mine costs 240 wealth and 240 corundium.
One orbital mining module costs 120 wealth and 120 corundium.
To move one auto mine requires one cargo hold, which weighs 25kt.
One orbital mining module weighs only 5 kt.
Of course, there is the cost of building a ship with the modules, and moving the ship to a colony.
But this cost is small compared to the cost of the modules themselves.
And you can use the "no armor" checkbox to make the ship cheaper, and to build it with construction factories (instead of needing a shipyard).
My early mining stations are these:
Digger class Mining Platform 254,775 tons 2,516 Crew 6,793.9 BP TCS 5,095 TH 0 EM 0
1 km/s No Armour Shields 0-0 HTK 327 Sensors 5/5/0/0 DCR 1 PPV 0
MSP 16 Max Repair 120 MSP
Squire Control Rating 1 BRG
Intended Deployment Time: 3 months
Orbital Miner: 50 modules producing 800 tons per mineral per annum
ASS AS18-R100 Anti-Ship (1) GPS 1000 Range 18.5m km Resolution 100
EM Sensor EM1.0-5.0 (1) Sensitivity 5 Detect Sig Strength 1000: 17.7m km
Thermal Sensor TH1.0-5.0 (1) Sensitivity 5 Detect Sig Strength 1000: 17.7m km
This design is classed as a Commercial Vessel for maintenance purposes
This design is classed as a Space Station for construction purposes
This station has 50 modules on it (plus some scanners, which I put only for fun). For the same cost, you can build only 28 auto mines.
But auto mines do have an advantage: they can be used on any colony. Orbital mining modules can only be used on very small bodies.