Could be, but I don’t think I’d want a steam locomotive, which are known to emit copious amounts of sparks, near a hydrogen gas balloon.
At any rate, this is SF. It doesn’t give a date, but somewhere in mid to later 21st century. The zepplin’s frame is made of carbon fibre; it has multiple gasbags, some with hydrogen, some with helium.
Wouldn’t this work better if you had two locomotives at front and back keeping the wires exactly taut between them with computer controlled driving to maintain the precise distance. That would keep your blimp at an exact height and stop it drifting off with the wind to left and right. To land you just winch in and bring the locomotives to a halt, you can get the blimp to land exactly on the tracks between the locomotives this way.
I can imagine a post scarcity society making something like this for a tourist scenic journey, just because they can, because they have unlimited energy to waste (nuclear or renewables or whatever) and its just a cool thing to do. But yeah it doesn’t have much practical value over a train or a blimp.
Actually, most steam locomotives that ran on coal or wood had spark arrestors. Otherwise they’d have started fires in cities and forests all the time.
Spark arrestors weren’t perfect; sparks still escaped and started fires. So that doesn’t change the fact that it would be a bad idea to have a steam locomotive near a hydrogen zepplin.
Dean Ng had a sci-fi treatment, The Big Lifters, of lighter-than-air craft to be used as mobile cranes. They could load and unload modular railroad freight cars anywhere, so you weren’t dependent on lifting cranes in railyards. Pretty good book, and a more believable premise than Brin’s.
Brin’s idea might work for isolated local tourist loops, such as a special tour train near the Grand Canyon. But for existing routes, it would require the elimination of every single overhead bridge in the rail system. Lotta investment for minor return.
Also…safety engineering. A very small side-gust of wind could end up toppling the pulling car. Doesn’t seem this could be sufficiently stable.
I must confess that I have seen a computer-generated clip depicting this concept somewhere on the internet. Trouble is, I’ve been looking all day on Youtube and elsewhere to find it, but it is nowhere to be seen.