Total world energy usage is about 1/10,000 what the sun provides. Bumping that up an order of magnitude means 1/1,000 instead. Seems reasonable for solar.

I don’t see research into fission power doing anything useful for spacecraft. The big bottleneck right now is getting stuff to orbit. The rest is easy, relatively speaking. And getting stuff to orbit is not practical with nuclear unless you use something like Orion, which has some downsides to put it mildly, and is already doable with 1950s tech.