One thing I felt the need to correct:
The spaceship that goes to Alpha Centauri does not travel faster than light in SMAC at least. In SMAC the Unity leaves Earth in 2060 and arrives at the Alpha Centauri system in 2100, so it takes 40 years to travel 4.37 light years. This speed of about 0.1c is actually theoretically possible with the technology that we have today (using nuclear propulsion), it would just ridiculously expensive.
Still, a GDR would probably be cheaper and easier to make than such a spaceship but militarily impractical as its such a big target.
I think its actually debatable that a fusion-powered robot would be easier to create at this point than a space ship which could reach AC. If we pooled together a ton of resources with current technology I think you're right in that we could maybe build a ship that could reach AC on a 40 year journey or so *if everything went right.* But I don't know if we could actually create a fusion-powered robot with current technology no matter how many resources we threw at it.
First off, for those saying maybe the uranium is used is to start the fusion process, that doesn't seem like a viable excuse. Afaik the only current fusion devices that absolutely require uranium are bombs that use a small fission reaction to create the pressure and heat required for the fusion reaction.
It does require a large amount of energy to start a fusion reaction, but that could come from any type of power plant. It'd be a horrible design to have to put a fission power source in the robot just to ignite the fusion reaction, cause once the fusion reaction got going it'd ideally be self-sustaining. If that were the case, it'd make the most sense to start the reaction with an external power source. But that's assuming you could fit a self-sustaining, net energy gain, fusion reactor in a robot. And that might be just as unrealistic of an assumption, if not more unrealistic, than building a spaceship to reach AC.
I can't recall whether anybody has ever actually conducted a net-plus energy fusion reaction (i don't think so), but either way we're still probably 20-50 years from being able to build a sustained-fusion reactor. If that. One thing that makes the robot more unbelievable in this context is that we seemingly simply have to make them bigger and bigger in order to be able to sustain a reaction. So even when we ever do figure out how to create reliable fusion reactors, it seems highly unlikely we'd ever be able to scale it down so that it fits into a robot as its power source. I guess it depends on exactly how big the robot is though eh. Maybe if its like the size of that one from "The Day the Earth Stood Still" x5 lol.
Then there's the problem of the surrounding materials becoming radioactive. Its a popular misconception that fusion has no problems at all concerning radiation. While the reaction itself doesn't emit radiation, it emits high quantities of neutrons which can and will crash into the nuclei of surrounding materials. Over time, the robot would become radioactive and, maybe more importantly, brittle. Maybe the uranium armor is supposed to help with that =p
Btw, I'm just shooting
. I don't care how realistic the robot is or isn't. Wouldn't hurt to change the requirement to fission though just to make it a bit more believable. Unless the thing is going to fire missiles with fusion warheads.