I hope Idahopotato doesn't mind my reposting this here
from Dumb Novels, but I though it deserved more of a response than it got over there (TheByrainTrust: "Yup. Either one is plausible."):
IdahoPotato wrote:I have always thought that fold space technology used mathematicians akin to pre-mentat abilities to navigate the ships. They would obviously not be able to end up in nearly as accurate locations as the guild operators would be able to, thus shaving off months or even years of transport needed from the freight liners to the planets. I figure that this type of travel would have been available in the time of Dune, but since Dune revolved around noble houses, the only one that could afford the enormous price the spacing guild would have charged, it appears that it is the only means of interstellar travel. However, I don't recall (and I am sure someone here will correct me if I am wrong) anything saying that it wouldn't be possible for mentat navigators to still operate fold space technology with far less accuracy than the navigators do. That or perhaps the fact that the navigators could do it so much more efficiently, they created a monopoly that drove everyone else out of business. Either explanation is plausible, no?
Remember that there is absolutely nothing mystical or special about space-folding technology; anybody could operate it, even a machine.
Think back to this, in the first part of
Dune:
[Mohiam] nodded. "We have two chief survivors of those ancient schools: the Bene Gesserit and the Spacing Guild. The Guild, so we think, emphasizes almost pure mathematics. Bene Gesserit performs another function."
So one way of looking at Navigators (besides as funky deformed space druggies) is as Math-Mentats-with-Prescience.
The mathematical computations required to plot course/destination coordinates and all that could have been done by computer (if you accept space-folding before the Jihad & Guild), or by Mentats with some extra training (after the computers were gone). What the prescient Navigators made possible (and
what sealed the Guild monopoly) was being able to plop a ship right into orbit around a planet with no chance of collision with some object already in the target star system (or something like a ship folding in from elsewhere). (The use of prescience also represented a built-in double-check of the destination coordinates, because if the Navigator made a mistake and set a course ending up inside a star or planet, he'd see that when he looked into the future.) The risk of collision with a non-prescient navigator, even a Mentat or computer/AI, would have necessitated folding into the target system at significant (=safe) distances from the destination planet. (And even then there was no 100% guarantee of safety.) Which would in turn mean having to move the ship after arrival, using some other propulsion method, to get close enough for shuttles to and from the surface. And
that would be much more expensive in terms of fuel/resources & time.
So it was no doubt the combination of safe and quick travel provided by the Guild that drove any competitors out of business. (And if anyone got the bright idea of trying to set up and challenge them again in later millennia, maybe the Navigators detected the threat and the Guild was able to muscle other parties, like the Emperor, into squashing them.)
For all practical purposes at the time of
Dune, the Guild is the only form of interstellar travel available. All the other, older methods were still possible, of course (again, I prefer to exclude FTL), but just too slow and expensive compared to the (instant?) transportation offered by the Guild. (Only the richest Houses would have been able to afford to build an alternate starship, and even with Mentats trained to fly it, why would they want to spend decades or centuries or millennia in space?)
Good luck!
