Hi Hugues. Yes, you have pinpointed the problem today with regard to global warming: people cannot migrate the way they used to (not to mention the impact on the oceans). And yes, our ancestors suffered hardship — that was what life was like then. Climate does not change in one’s lifetime: one is born into whatever it is during that 50 year period. People migrated from Asia to North America along the coastline apparently, when North America was covered by the Laurentide ice sheet. Today people cannot simply pick up and move as easily.

Regarding fusion, I would not call it science fiction. There is active research on it now, and it is promising. Creating a fusion propulsion system is apparently an easier problem than creating a contained reaction. Perhaps it will be something that is “always 10 years away”, but it is hard to tell. In any case, it is not fantasy — there are scientists and engineers right now who are trying to build fusion propulsion systems; and your article was about the future anyway!

Yes, the rocket equation expresses the constraints. Fusion would produce a vastly higher particle velocity in the exhaust, resulting in a higher efficiency for a given amount of reaction mass. The weight of fusion fuel would be negligible, so the reaction mass is the mass that would appear in the rocket equation. With fusion, we won’t be achieving near light speed; we will merely achieve speed that is at best an order of magnitude faster than with a chemical rocket. Still, that is a big improvement!

Not sure what you mean about not being able to go anywhere beyond low Earth orbit. We have already gone to the Moon. I am looking forward to chemical rockets taking humans to Mars. With fusion, we might be able to get there is half the time. If I had a choice between spending six months for the trip or three months, three months sounds a-lot better!