During preproduction for TNG, the only Starfleet vessel model built was the 6-foot and 2-foot Enterprise-D. They didn't want to spend the money to build more because a) they didn't know how long the show would last, and b) they had the four movie models to use. However, I wish they had had the foresight to build two more newer ships (one to act as the "ferry" that the Excelsior was always doing), and one to be the little science vessel that always got into trouble and needed the Ent-D to rescue it.
Why do we consider warp 8 (new scale) as a low top speed? Warp 9 is more something top of the line vessels can do, its regarded as REALLY fast. Ships seem to cruise around at warp 6-ish speeds most of the time anyway. Not all cars here on the road can do the 420 Kmph as the Veyron can do either...
Perhaps we're thinking about this wrong. Sure, the Intrepid class' top speed is Warp 9.975, but it doesn't sustain that speed forever. Someone worked out that Voyager's 70 year journey was actually based on a speed around Warp 6 or something, far less than top speed. In aircraft design, military jets in particular, they are designed with an efficient cruise speed and a dash speed, which is the top (although unsustainable and inefficient) speed. Maybe the Nova class' engines, due to it only being a survey ship, is only capable of cruise speed, and not a dash speed. In that regard, the Nova class would likely matches the Intrepid class' cruise speed, which is what it would be traveling at most of the time anyway.
What's said in "Caretaker" is "...sustainable cruise velocity of warp 9.975" which indicates she can go even faster for short periods.
Exactly. IMO, all ships can in theory go faster than their top-rated speed, but usually at the risk of burning out the engines (or even flying the ship apart). The Voyager might be capable of hitting warp 9.99 in an emergency, but probably not for very long and at extreme risk.
The actual words from "Caretaker" are "Stable cruise velocity of warp 9.975" - Coppola fumbles her line to this effect. But stable=sustainable, I guess. And the claim is repeated in "Relativity", where Janeway says "Top cruising speed, warp 9.975". Both times, there's the "cruise" bit, heavily implying longterm sustainability, and Lt Stadi even redundantly adds stability to that. Of course, the ship never cruises at such a speed - indeed, she never even attains such a speed, the computer shitting herself at warp 9.7 already and claiming total destruction in less than a minute if Chakoteya keeps accelerating. But that's battle damage and skipping of annual dockyard visits for ya. Back in "Caretaker"/"Relativity", the ship might actually have been capable of the stated speed. Perhaps relevantly, the puny little nacelles of the Voyager show marked lack of correlation between size and speed. Small ships have small nacelles, big ships have big nacelles, and ships known to be fast for their time may well have small nacelles relative to their overall size (Intrepid, Galaxy). The looks of the Nova engines are probably indicative of nothing much, then. Timo Saloniemi
For all we know, the Voyager may only be able to hold her "sustainable cruise velocity" or "top cruising velocity" for 12 hours. She may be able to maintain a normal/nominal cruising velocity of warp 6 or so until fuel exhaustion.
In most episodes it appears Voyager is at most capable of playing in the warp 9.5+ range and for much of her journey seemed to be averaging around warp 8-ish. I mean the engines complained as early as "Threshold" about high warp speeds so I doubt it's long-term problems that eventually made it slower.
Indeed, we might be better off arguing that whatever performance drop the ship suffered, it came from the initial "Caretaker" damage that they never had the chance to properly repair. The fun thing about warp speeds, backstage and in onscreen action, is the steepness of the curve. Warp six ain't twice as fast as warp three - ships capable of warp six are fast, while ships capable of warp three are worthless tubs. And the ability to up the ante to warp nine means superfast, not merely half again as fast as warp six. OTOH, moving from warp six to warp eight makes Scotty whine like the last trump - the speed change is serious business, even if it sounds like nothing much when only two warp factors are added. It appears perfectly natural in the Trek context for cruise speed to be perhaps a thousand times slower than top speed, and possibly ten thousand times slower. However, whenever there is a chase scene, it seems that both sides can attain pretty much the same dash speed and sustain it for a couple of minutes at least. There are very few episodes where being superfast allows one to make a clean getaway... A good example is "Equinox" itself, where it doesn't matter that the titular ship is both superslow and superfast (depending on whether they are doing the throwing-space-dolphins-into-the-boilers thing), chases with the Voyager can still take place. That's not necessarily a technological contradiction: as said, warp coils do appear to be capable of infinite speed by default, and the rest of the drive train can be abused to varying degrees to create the desired speed. Some ships can abuse their powerplants or whatnot for an easy ten minutes of superspeed, others will rip their power systems to shreds in five and a half minutes, but both cases allow us to see a chase scene lasting for five minutes. I'd like to think that the low speed of the Nova is a safety issue: the small and weak ship cannot afford to toy with high speed dashes that might leave her stranded in deep space. The same goes for Scotty's worries about warp eight and beyond: the Constitution can easily attain warp sixteen, but anything beyond warp eight may be fatal during a deep, deep, DEEP space mission, which is the sort of mission that this ship type so often performs. Timo Saloniemi
To add to what Timo and others have said, especially regarding the lower-power but easier-to-govern warp core, I am inclined to think that the Nova-class was designed to be able to sustain Warp 8 indefinitely, or at least as long as is needed to get where it's going. Seems like most Trek ships are described on websites and in tech literature as having three rated speeds:cruise, maximum, and 12-hour dash, and it appears that cruise is probably for best efficiency and fuel consumption, while maximum is sustainable for as long as they wish without causing damage or problems. Larger capital ships seem to be in the ranges of Warp 6 cruise, Warp 9 maximum, and Warp 9-point-whatever for dash. That being the case, a relatively small ship like the Nova-class sustaining Warp 8 indefinitely is pretty respectable, gets them to where they need to be within an acceptable time frame, and frees up the in-depth exploratory missions so the larger capital ships can go about their business. Clearly, the "Equinox" plot required the Nova to have a reason to be slower than an Intrepid, but the Warp 8 maximum speed still fits acceptably well with in-universe explanations above.
The main reason is that it is super cool. It doesn't need to rush like those other cruiser scrubs, Nova takes its time and gets there in style, sometimes even fashionably late