There are bigger fish to fry in terms of the environment.
Getting something in orbit will always be expensive and prohibitive, even when space elevators are built, so there will be enough incentive to start building things in space.
Orbital fabrication and mining are intertwined, but together they're the key to any long-term human presence outside Earth.
Four/eight year military service spent policing/polluting the world could be replaced by short "tours" in asteroid belt operations.
The key to all of this would be constant launches and flow of material/labor, ideally with international cooperation. The high frequency of launches in itself is a safety feature - stranded crews would be able to expect fly-bys.
It would be expensive at first because we would essentially be ejecting many resources away from the planet. But the promise of heavy-industry eventually zoned outside of our natural atmosphere could be the [non-classical] incentive.
It would seem more efficient with a field rather than constantly ejecting usable material.
How is the inverse squared law applied to space fission? Ease of cooling?
If you double the distance, the radiation hazard reduces by a factor of four. This is why the Sun — an unshielded fusion reactor — hasn’t already killed everyone.