Effectively, what we need to do is to get some kind of space resource rush going. Similar to what fueled the likes of the East India Company.
The question has always been what resource, with 3He and platinum being the two main contenders.
Otherwise, it could be like coal mining in Antarctica, or manganese module mining from the deep seafloor - technically possible, but not profitable, and certainly not enough for a new EIC.
Ideas. That crazy nuclear experiment you want to run? Fat chance in Montana. But on the far side of Mars? Why not.
The best I could come up with would if be it leads to a fuel production source, like the satellite at the end of Heinlein's "Blowups Happen". But we know of no such thing, nor do the economics seem to work out.
There's about 1,000 atoms per cm^3 of interplanetary space. Let's say you've got 1 kg of silicate rock -- SiO4. That's 4 parts oxygen (atomic weight 16) to 1 part silicon (atomic weight 14).
A kilogram is about 10^30 atomic masses. So we need 10^27 cubic centimeters, which works out to about 100 million km^3.
The Earth has a volume about 16,000 times larger -- which means at the average density of interstellar space, there would be about 16,000 of those rocks you have in hand, or 16 tonnes of matter. Rather than the six thousand billion billion tonnes of matter actually in the Earth.
We've met the space resource rush and it is us.