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The escape velocity for Earth is 11 km/s. The escape velocity for mars is 5 km/s. The situation for a ground launched projectile is of course worse because of air resistance losses.

It's still really difficult to accelerate something to 5 km/s. (It's 2.5 km/s on the moon)

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Wikipedia says there are prototype railguns that can shoot at 3km/s now (wording: "can regulary exceed 3km/s")... are we at a point now where I could put a rail gun and a bunch of solar panels and batteries on the moon and just shoot (tiny) stuff into orbit?

Not like the rocks on the moon are that useful for anything, but....

Apparently there is helium-3 on the moon which could be used as a fusion reactor fuel.

https://en.m.wikipedia.org/wiki/Helium-3

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