[mvpel]

The answer is nuclear power. With sufficient cheap energy, any amount of synfuels can be manufactured.

You could have a nuclear-powered locomotive, too, with a closed-cycle gas-turbine engine.

[norraad]

I'll take two!

[boris]

It would be enormous. Imagine a train wreck with a nuclear loco. I happen to live about a mile from a major rail line and frequently wonder how the folks whose houses are right up next to it can stand the noise. Imagine the NIMBY reaction to a nuclear locomotive. To carry enough shielding would result in gigantism. Familiarize yourself with the technical issues that killed the nuclear airplane and look into Project Pluto. You might even look at the studies of the outcomes of a crash of a nuclear aircraft. Double-plus ungood.

--Boris