An Explanatory Guide About Mining and Boost
Once you get space resources, you can use the “build in space” option when constructing modules (Not founding new platforms/outposts).
Space resources will be used instead of boost for any resource you have enough of and boost will be used for the rest.
For instance, a space science module costs about 0.5 volatiles and 1 metal.
To get that into low earth orbit (LEO) that normally costs 1.5 boost.
If you have 1 metal, building in space then costs 1 metal and 0.5 boost instead (assuming you’re building in LEO).
If you can build using only space resources, then you also get the module faster (nothing needs to be sent from Earth).
Boost costs increase the further out you get, so it usually makes sense to build a mine on Luna to get enough resources (mines cost a lot of metal, so primarily that) to make a mine somewhere more profitable (Mars or its moons, typically).
However, it is possible to instead use a combination of technology and a bit of extra boost to start on Deimos instead. But obviously only one faction can do that.