Behold!
Obsidian class Orbital Mining Platform 150,000 tons 1,225 Crew 3,621.7 BP TCS 3,000 TH 300 EM 0
100 km/s Armour 1-251 Shields 0-0 HTK 195 Sensors 6/6/0/0 DCR 1 PPV 0
MSP 15 Max Repair 120 MSP
Cargo 25,000 Cargo Shuttle Multiplier 2
Lieutenant Commander Control Rating 1 BRG
Intended Deployment Time: 3 months
Orbital Miner: 23 modules producing 276 tons per mineral per annum
Fokin Drive Systems NPE-100 Skywalker (3) Power 300 Fuel Use 8.94% Signature 100 Explosion 5%
Fuel Capacity 1,184,000 Litres Range 15.9 billion km (1838 days at full power)
Arslangiin-Damdinsuryn AD-6100K Mark 6 Waveform Detector (1) Sensitivity 6 Detect Sig Strength 1000: 19.4m km
Angulo-Guindo AG-6M T6 Series Infrared Scanner (1) Sensitivity 6 Detect Sig Strength 1000: 19.4m km
This design is classed as a Commercial Vessel for maintenance purposes
Designed to be completely self-sufficient for an almost indefinite length of time, the Obsidian-class orbital mining platform comes equipped with a 25,000-ton cargo bay expressly for the purpose of lugging around a Mass Driver as it lumbers from asteroid to asteroid mining up minerals for my empire.
Is this optimal? Probably not, but it was fun to build and now you know that at least one person uses mass drivers.
More seriously I suspect there's a few reasons that most people use the platform/tug/freighter setup instead:
- Large orbital platforms without engines can be build as space stations using planetside construction, which notably means you don't need a shipyard big enough to build a 150,000-ton monster ship. Personally I don't see this as a big hindrance since 150,000 tons of commercial shipyard is the same as 15,000 tons of naval shipyard and nobody would call the latter excessive.
- Using tugs means you don't have to put engines on your mining platform, which once you've built the platform it's good forever assuming all you put on it were OM modules. The tug is the only thing that needs replacing as tech advances and you only need a couple of tugs to manage your mining platforms since they are park-and-forget installations.
- Freighters over mass drivers makes sense since most asteroids only have one freighter-load of minerals anyways (depending how big your freighters are), so if you have to make one trip either way why not ship the minerals instead of the mass driver not to mention having to spend money building the things? Of course, mass drivers give you the minerals as soon as you mine them, which can be very useful if you're experiencing a crunch
That said, my setup is perfectly fine, as the only issues are needing a "big" shipyard (eh) and "wasting" tonnage on engines and cargo handling, but the logistics are a lot simpler with only one ship instead of three (please ignore the fact that I then promptly complicate things by having my tugs fly around the galaxy towing sensor platforms into place...ah, simplicity...
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EDIT: I do also use the AM + Mass Driver setup early in the game, mostly to mine comets. It works in the early game, but AMs are more expensive than both regular mines and OM modules (240 corundium versus 120 for the others) so it's better once you get going to conserve AMs for use on worlds where conventional colonies are too expensive but the body is too big for orbital mining. In those cases you can either use AMs or use normal Mines plus habitat modules if you're scraping the bottom of your corundium barrels or just want to build more big space stations.