So, first, the clear bugs. The loco accepts burnable fuel (and the non-craftable uranium fuel cells). The decision not to allow other nuclear fuels than thorium may or may not be deliberate.

Second, the reason it needs a buff.

At a very similar technology level we have access to trains with half the weight, twice the power, and more than 1.5* the top speed. With a space elevator, we are essentially required to use these much better trains. It does not make sense to run anything else on the ground tracks which is so slow as to just serve as a track blockage for the space trains, when we could just run the space trains everywhere. Or at least the locos. The nuclear train has no point, and it would be good if it did, by having the same top speed as space trains, and at least twice the power it currently has.

I also just looked through the rest of the trains and the future train, which is a higher tech level than space trains is also inferior, though the second tier is faster and more powerful, if heavier.

Another option, I guess, would be to nerf the space trains.

I think that was different in 1.1 so something is wrong with the migrated code.

I think that was different in 1.1 so something is wrong with the migrated code.

This is not, as far as I can tell, the case. (Or not mostly.) Comparing the last version in my 1.1 directory to now, some of the names have changed, but the stats haven't. It's -odd- IMO that not all of the fuel rods are allowed in the nuclear locomotive and that many non-nuclear fuels are, but it sure looks like that's how it was.

As far as the comparison goes, I think you may be just looking at raw stats and not taking into account fuel bonus. (And to be honest I had an entire reply written before remembering them, so you're in good company.) I don't think the disparity is quite so bad between the nuclear locomotive and the space locomotive with that factored in - the former can go nearly as fast on thorium fuel rods, though the acceleration is lower.

The EM suspension train 1, with fuel bonus, has much higher acceleration than the space locomotive regardless of fuel used, along with modestly higher speed. The locomotive is a lot heavier. I'm... honestly not sure how much of a difference that makes? I did a straightline sprint test, and using thorium fuel rods with a simultaneous start, LCC trains for both, the space train took an early lead, the suspension train pulled ahead in the middle, then came in just a little behind at the finish. With uranium fuel rods (slightly higher acceleration bonus), it's similar but almost a simultaneous finish. That's with no braking force research. BF5 seems to help the EM train a bit more, but it's not huge. I don't know if turbochargers would help one more than the other or not. (It's odd IMO that they work at all on non-diesel trains.) I don't know how likely one would be to run their trains on the superior mox or high energy mox fuel rods.

Overall... I think the nuclear locomotive is more or less okay, though if it were me I might make it available a bit earlier. (If we can make a train nuclear reactor at rocket science, why not a train that has a nuclear reactor built in?) The EM suspension train 1 suffers from it's high weight, though I don't know how much of a difference that makes in practical applications. Still, if it's to be a clear upgrade, it might stand being dialed down a bit, or possibly something else tweaked.

As far as the comparison goes, I think you may be just looking at raw stats and not taking into account fuel bonus. (And to be honest I had an entire reply written before remembering them, so you're in good company.) I don't think the disparity is quite so bad between the nuclear locomotive and the space locomotive with that factored in - the former can go nearly as fast on thorium fuel rods, though the acceleration is lower.

I was under the distinct impression that fuel only affected acceleration. Maybe that's a vanilla thing? Regardless, I see that you are quite right about this.