Hi, I tried out bob after a long hiatus, and found that the plutonium requirement is currently too harsh for space science.
Basically, I built all the other science and researched practically everything before going into space science. Then I suddenly found that the only way to get plutonium is to breed it in a reactor, which is cool, and realistic, and so on, but it also means that I not only had to build a reactor just for that, I also had to artificially increase electricity usage, as science is basically the only thing that uses the electricity and I had no science to research left (infinite science tiers require space science...).
As end result, I built lots of beacons and other items as there is no nice way to just waste electricity, and I still had to wait 4 hours to get all the required plutonium, while not being able to do anything useful.
Thats neither realistic nor fun, nor balanced, IMHO.
I would suggest having another recipe to get plutonium, such as a breeding recipe in some machine (or maybe a special breeding reactor). Otherwise I fear especially people starting new games will maneuver themselves into a dead end, like I did, when they research non-space science first and then find themselves with this requirement, and no easy way to fulfill it.
Just my 2¢.