Can TNG-era warp drive be used to travel at sublight speeds?

Question

In Star Trek: The Next Generation and its contemporaneously set sequels (Star Trek: Deep Space Nine and Star Trek: Voyager), impulse engines are used for moving spacecraft at sublight speeds, whereas the warp drive is used for travelling at light or faster-than-light speeds. Warp drive speeds are measured in "warp factor", an irregular numeric scale with values known to range from 1 (light speed) up to but not including 10 (infinite speed).

My question is whether it has been definitely established that it is possible in the TNG era to use the warp drive to travel at sublight speeds, which would correspond to a warp factor of less than 1. In particular, I am looking for the following types of evidence, in descending order of priority:

1. An unambiguous depiction in the primary canon (i.e., the TV shows and feature films) of sublight warp travel.
2. A statement in paracanonical works such as the Star Trek: The Next Generation Technical Manual or the Star Trek: Deep Space Nine Technical Manual that warp drives can operate at sublight speeds.
3. An unambiguous depiction in official but non-canonical works (e.g., novels, comics, computer games) of sublight warp travel.

As discussed in the answers to this more open-ended question, I am aware that some Trek shows set before the TNG era occasionally referenced ships travelling at warp factors less than 1. However, these shows used a different warp factor scale and depicted a more primitive warp technology. My question is specifically about TNG, DS9, and Voyager, and about the warp technology and the warp factor scale in use in that era. I'm looking for actual depictions of sublight warp travel in this era, or in-universe statements in this era that such travel is possible. I'm not interested in extrapolations from what we know about ENT- or TOS-era warp.

Answer 1

If Cochrane's flight in First Contact counts as TNG-era, then this includes a period of a few minutes where the warp engines are on but they haven't reached light-speed yet. I'd personally consider this to be morally TNG-era in the sense that although the warp drives are pre-TOS technology, the film was made according to a TNG understanding of how warp drive works.

What we see in the film, interspersed with scenes from other plotlines, is:

1. The Phoenix zooms up into space, then turns off its big rocket engine and unfolds warp nacelles.
2. Riker brings the warp core online. Cochrane says "Engage!". Geordi says "Warp field is looking good." Riker says they're going at 20,000 kilometres per second.
3. Riker says "Approaching light speed"; Cochrane says "We're at critical velocity"
4. From outside, we see the ship zooming across the screen and then disappearing in the usual warp "flash".

In the novelization, some added thoughts from Riker flesh this out:

The thrill he felt at that instant was nothing compared to the next, when Cochrane turned back toward his controls, and - eyes passionately ablaze with determination, expression utterly composed - ordered, "Engage."

Riker immediately tensed, waiting for what would surely be an incredibly intense sensation of acceleration, then forced himself to relax. The ship did, indeed, accelerate, but this was not a starship; it would take a few minutes to attain warp speed.

Later:

Riker looked back down at the speedometer display. "Approaching light speed..."

Light speed - such an outdated term; warp one, he had almost called it, but the standard would not be coined for almost another decade.

Warp one, considered in the twenty-fourth century to be the speed of molasses.

Warp one had never seemed so fast.

I think that what's going on here is using the warp engines to travel at warp less-than-one while accelerating to warp one. It could be that they're using some other tech to move the ship itself, but my reading of the warp field being up is that it's this which is responsible for their acceleration. Riker's thoughts in the book indicate that TNG-era ships do this much more quickly but there is still some amount of time before warp one is reached.

There doesn't seem to be an obvious reason why a ship couldn't continue to cruise along at a sub-warp speed, except perhaps increased power usage or something like that.

Answer 2

To be fair this isn't a physics question but a search for examples. As the OP acknowledges the motion picture.

I'll argue that the term millicochrane is probably the closest you'll get in a Berman era script. A metric physics unit where 1 Cochrane of subspace field strength gets you warp 1. However the examples listed in Memory Alpha tend to be regarding space distortions not velocities. But there are some engine specs I'll quote at the bottom. https://memory-alpha.fandom.com/wiki/Cochrane_(unit)

But the fact the TNG era considers this a useful unit of measurement does imply that a starship emitting 500 mC would be going less than Warp 1 and more than 0. The alternative that only integer multiples of light speed is possible with warp drive doesn't seem supported even if personally I'd rather it worked that way. Merely it just doesn't seem worth mentioning in-universe considering acceleration rates and total velocity. The Motion Picture build to Warp 1 was out of caution and would probably be even faster in a TNG era warp core.

Edit from Memory Alpha 750 millicochranes: Federation Type 15 shuttlepods were equipped with two long-range 750 millicochrane impulse driver engines. (TNG: "Descent") The Star Trek Encyclopedia (4th ed., vol. 2, p. 42) defined millicochrane as "one one-thousandth of the force necessary to establish a field of warp factor one." Cochrane 1.25 cochranes: Federation Type 6 shuttlecraft were powered with two 1,250 millicochrane warp engines. (TNG: "The Outcast")

Edit 2: from TNG technical manual section 6.2. "Efficiency ratings for impulse and warp engines determine which flight modes will best accomplish mission objectives. Current impulse engine configurations achieve efficiencies approaching 85% when velocities are limited to 0.5c. Current warp engine efficiency, on the other hand, falls off dramatically when the engine is asked to maintain an asymmetrical peristaltic subspace field below lightspeed or an integral warp factor (See: 5.1). It is generally accepted that careful mission planning of warp and impulse flight segments, in conjunction with computer recommendations, will minimize normal clock adjustments. "

Additional note the asymmetrical peristaltic subspace field is what makes the ship move - not newtonian thrust - from the chapter on warp drive operation.

Answer 3

While not necessarily using the Warp Drive to move, the Enterprise moves at sub–light speeds while maintaining a Warp Field in the episode Deja Q (S03E13), using it to reduce the effective mass of a moon so that they can push it back into orbit.

Answer 4

This article on Ex Astris Scientia talks about an occasional occurrence of 'Warp 0.5' in the TNG era, but it doesn't list a specific episode. It does list a reference to the TNG Technical Manual. The following paragraph (emphasis mine) seems to argue for the case that sublight speed equals impulse drive only.

Warp factors below Warp 1 are occasionally mentioned in Star Trek, mostly in the scope of the 24th century scale. Consequentially these refer to sublight speeds. The question whether something like Warp 0.5 exists has some relevance. Warp 0.5 could either mean that the warp drive also operates at sublight speeds, without a need to activate the impulse engines, or that the warp scale is simply extrapolated below Warp 1, even if only the impulse drive is on. With the note in the TNG Technical Manual [Ste91] that the impulse drive makes use of subspace driver coils the latter makes sense also technically, because if the warp factor generally describes the formation of a subspace field, it may as well apply to the field generated by the driver coils at sublight speed.

Answer 5

Not sure how canon this is, but the Star Trek: Starfleet Corps of Engineers series has a story where a colony ship had accelerated to such a speed that it was far above impulse speed, but below warp 1, so the crew of the da Vinci, and a nearby Klingon ship modify their warp engines so that they essentially cycle four different warp coils (or similar) to generate warp bubbles in quick succession, instead of having a single warp bubble constantly on.

The end result being that, practically speaking (but not technically), the ships fly in "warp" at less than warp 1.

Answer 6

I think the short answer is "yes", but in practice they don't usually do it because it is not energy efficient. I don't have my copy of the TNG Technical Manual with me right now to find an exact citation, but I remember a section which discusses/graphs the energy requirements for traveling at any given warp speed including fractional warp factors in some detail.

The energy required to go faster is not a perfectly linear relationship, so speeds like warp 6.7 are possible, but at a certain point it actually ends up taking less energy per unit of velocity to climb to warp 7 and stay there. For this reason, you don't typically see starship captains ordering helm to fractional warp speeds except for speeds significantly over warp 9.0 in emergencies since warp 10 is unattainable--except that one time in Voyager nobody likes to talk about :)

For this same reason, I think sublight warp is definitely possible in the TNG universe, but there are few good reasons to do it when impulse engines are up to 85% efficient up to 0.5c per the section lucasbachmann quoted above. It might make sense in some scenario where they need to match speeds with some object moving at 0.95c. It could also make sense if a character needed to quickly intercept another ship on the opposite end of a star system. Though the warp speed isn't actually stated, something like this actually happens in Star Trek DS9's season 5 episode entitled By Inferno's Light when Kira makes an in-system warp jump to prevent Bashir's Changeling impostor from detonating a bomb which would destroy the Bajoran sun. Kira might have used warp 1 or even warp 2, but for a very short duration. This brings up the question of acceleration. How long does it take the ship to get from 0 to light speed (warp 1) ?

Since the warp drive is usually the most powerful energy source on a ship in Star Trek, it makes sense to me that acceleration to high sublight speeds would be faster with warp power. In Star Trek Generations, Picard jumps Enterprise-D to warp 1 to avoid the shockwave from Armagosa being destroyed in about as much time as it takes Data to press the button.

As such, I can also imagine special cases where the distance which needs to be covered ASAP can be covered in less time than it takes the engaged warp engines to reach warp 1, and drastically less time than impulse engines at maximum power.