I'm pretty sure the model of train is a proper name and it's named after the satellite. I don't think I would describe any train as a literal "sputnik" of the rails.

Also Russian is full of composite words like that. "Explorer" in russian would be "исследователь" (issledovatel') - ис (completely) + след (trace/footstep) + оват (make, imbue) + ель (he who). Literally it would be "he who makes (places) completely (covered in) footsteps"