In Frank Herbert's Dune, all faster-than-light travel is under the Spacing Guild's monopoly, leading to some interesting political situations.
How do they travel through space? The miniseries made it look like a Battlestar Galactica-esque jump drive, but I pictured more of a hyperspace-based system, sicne Dune contains references to them spending at least a bit of time on board.
No huge spoilers from the sequels please, I haven't read them yet.
None really. They fold space. That's all that is really said about it from Frank Herbert's works.
Dune is a book about politics within a layer of science fiction. It isn't meant to be a "how did they make a ghola?" (though that is explained in some of the prequels). Or the actual biology of wtf did he do with that sand trout?!
As described in wikipedia on soft science fiction:
Frank Herbert's Dune series is a landmark of soft science fiction. In it, he deliberately spent little time on the details of its futuristic technology so he could devote it chiefly to addressing the politics of humanity, rather than the future of humanity's technology.
Don't worry about it. FTL happens. It is a tool of political control - not a piece of technology to be worried about.
Trying to understand fold space in the context of the Frank Herbert Dune novels is counter to the actual ideas and goals of the author and a distraction to the reader.
"Are the Guild ships really that big?" he asked. The Duke looked at him. "This will be your first time off planet," he said. "Yes, they're big. We'll be riding a Heighliner because its a long trip. A Heighliner is truly big. Its hold will truck all our frigates and transports into a little corner -- we'll be just a small part of the ship's manifest." - Plenty of room for misunderstanding the duration vs distance there. The key thing is the shear size and political nature of the guild.
“That's part of the price you pay for Guild Security. There could be Harkonnen ships right alongside us and we'd have nothing to fear from them. The Harkonnens know better than to endanger their shipping privileges.” - that they are their own political entity, and a powerful one. So powerful that the greatest rivals in the universe will calmly sit in what amounts to neutral territory.
In the novels, Frank Herbert describes FTL travel being achieved using "Holtzman generators" in order to fold space (rather than jumping or traveling through hyperspace) between two star systems. However, space travel is risky without the unique talents of Spacing Guild navigators, who use mélange (the spice found on Arrakis) to find the safest path through folded space to the destination. How, exactly, Holtzman generators fold space is not made clear in the novels.
By the way, David Lynch's 1984 film Dune seemed to suggest FTL travel was accomplished by the boosted mental powers of the Guild navigators alone via spice, but the novels are explicit there was a mechanical aspect to FTL. In my opinion, the more trippy explanation of using drugs to enhance mental powers to fold space and travel to other stars would have been far more interesting and evocative. Science fiction is rife with hyperdrives and FTL field generators so it's disappointing Herbert fell back on old cliches.
