Why Hyperspeed instead of Hyperspace?
A good question I fear.

FTL travel has always been a moot point in Battlestar Galactica. That and a load of other topics. The books though, corrected this point by stating that ships used hyperspace to jump to other star systems, and for the books, I think this works very well. But not quite so well for the series itself.

With the limited amount of information from the series, I have sort of deduced the following. (Actually, to be fair, I had an epiphany on this subject a few months back, but I never really acted on it because while it suddenly came to me, I have since lost the reasoning behind that, so I am now making this up as I go along trying to get back my though processes. And the moral of this? Always carry paper and pen when out of the house!)

The term light speed is banded about a couple of time, most notably in "The Living Legend" and "Experiment in Terra". Obviously travelling at light speed itself is impossible, so the term is an archiac expression. However, the mention of light speed does imply that the ships have FTL capability (which we knew anyway). But stating light speed instead of jumping, or hyperspace or something, is revealing in my view, that FTL travel is 'simply' much faster travel rather than jumping.

In addition, in "Baltars Escape" (I think that is the one, or else its the one after), when the Vipers are trailing the Eastern Alliance destroyer, how would the destroyer be able to detect the Vipers if they were travelling in hyperspace? Yes, you could argue that the ships at that point were actually travelling at sublight speeds, but then how did the Vipers follow the ship through hypespace? Finally, "Experiment in Terra" actually shows us the bridge view of the Galactica at light speed, and it looks more like hyperspeed to me rather than jumping into hyperspace.

Having hyperspace travel could have allowed the fleet to escape so many scrapes. For starters, the Ravashol Pulsar laser would have been ineffective as the fleet could have detected it and then jumped away to a new system. Baltars baseships would have had a harder time to track the fleet as they would be constantly jumping, whereas we get the impression that the fleet are constantly on their scopes. Would the Nova of Madagen minefield be a threat to a fleet that could jump past it? Finally, if ships could simply jump from one location to another, why was Apollo showing two completely different routes to get to Carillon in "Saga of a Star World"? If you look at the indirect course he plots, it is a spiral course. Even if the minefield was effective against hyperspace ships, surely it would be meaningless as the ship could simply jump to the other side of Carillon and then approach without entering the minefield?

So, I get the impression that the fleet uses hyperspeed. In my mind, this is much like the travel used in Star Wars. The ship itself stays in normal space, just travels incredibly quickly. As the ship is still in normal space, it can be interacted with by objects like planets and stars, so you have to plot a course around them. Or you could use the for slingshot effects, using their gravity wells to propel the ship. Minefields, would then become proper threats as a ship would still have to travel through them - meaning certain destruction at hyperspeed. Communications between ships travelling at hyperspeed can still occur as the ship uses FTL communications, but combat between two ships is impossible as weapons are only sublight. Hyperspeed does have other limitations. Like most sci-fi hyperspace jumps, hyperspeed is effected by gravity wells and it is not wise to activate the drive while the ship is around a planet, although at hyperspeed you could slingshot around the planet.

So that is my take on the subject. I am sure it has many flaws, but at the moment, it seems to work for me!