Just how fast is impulse?

[Timo]

A better question is how fast is 1/4 impulse in ST:III? Based on the known size of the Enterprise, leaving spacedock is done at somewhere between 25-45 mph.

Well, if "1/4 impulse" is a throttle setting, then the acceleration provided by it will depend on the throttle, and on the engine coupled to the throttle. "1/4 impulse" on a tiny shuttle ain't going to be the same as "1/4 impulse" on a big starship - and "1/4 impulse" on a damaged starship will be different from what it would be on an undamaged one...

As regards using the rocket equation on Trek ships, and echoing the previous post, let's remember that they have found some energetically cheap way to cheat gravity and inertia. That should throw the rocket equation out of the airlock completely: fuel could be massless when stored in the tank, yet hypermassive when exhausted, while the ship could also have the mass of a compact car at times. Or then mass as a factor could be ignored altogether, and the actual Newtonian moment of action and reaction could be directly mucked with - but the device could still be a rocket for all practical purposes, if that was to the liking of the engineers. Perhaps it is indeed reasonable to first build a fairly conventional rocket and then apply gravity magic on some of its components? Certainly many of today's technologies are based on similar seeming anachronisms: aircraft built by taking an ages-old glider form and applying turbojet or turbofan propulsion on it, cars built by taking a horse carriage and replacing the horse with an internal combustion engine, and computers built around typewriter and television elements.

Timo Saloniemi

 

[Christopher]

You accelerate up to a point where your forward motion is as fast as the exhaust that leaves your engine after that you can exhaust every bit of fuel you have if your engine can't dish out its exhaust at a faster speed it will be a futile exercise.

That's a misconception, one I used to make myself until I was corrected (and then checked my old physics notes and realized I'd known and forgotten the right answer years before). Actually the point where forward velocity equals exhaust velocity is the point of maximum efficiency. Above that (and indeed below that), your thrust efficiency decreases, but you certainly do keep accelerating as required by Newtonian physics. This is why low exhaust-velocity drives such as ion rockets can theoretically be used to achieve high interplanetary velocities, and indeed are ideal for doing so due to their low fuel consumption (as long as you're not in a hurry).

So how fast is impulse? Depends on how long you've been accelerating. Theoretically an impulse engine could get you up to several times the speed of light if you had a big enough "runway" of open space, but it's still quite a bit slower than warp, so it's not a very efficient way to travel.

What? No, no, no. You can't accelerate to above the speed of light. That's the whole reason warp drive is needed in the first place -- because accelerating through space can only get you asymptotically closer to lightspeed. It would take infinite time and energy to accelerate to exactly lightspeed, because relativistic effects would increase your mass to infinity at lightspeed. So accelerating above lightspeed is completely impossible. The only ways to surpass lightspeed are by bending space with a warp or wormhole, traveling through a hyperspace dimension, achieving a macroscopic quantum leap, turning your ship into tachyons, or otherwise doing something more complicated than just keeping your foot on the gas.

Other than that, you're right. Theoretically, any drive system, no matter how feeble, can get you arbitrarily close to lightspeed if you have enough time and enough fuel. Or if you use a propulsive method like a lightsail or magnetic sail, something where the ship itself doesn't carry any fuel.

Which isn't what I said. My argument isn't that it's physically impossible for an object to be accelerated to high sublight speeds--it's that it's physically implausible for a starship measuring a few hundred thousand cubic meters to be accelerated to high sublight speeds by a classical action-reaction system. Fusion does not provide enough energy per unit to move a ship of that size to that speed without fuel kept as degenerate matter. Hell, matter/antimatter annihilation doesn't provide enough energy per unit, and you are not going to get more energy per unit than "all of it."

Yes, it's established that impulse drive uses some form of inertial mass reduction or similar spacetime effect to enable rapid acceleration. But that's in conjunction with reaction thrust, which is why it's called impulse drive. It's not the same as an actual warp drive even if it incorporates some related concepts.

Besides, forget the technical explanations -- it's a TV show, so it's really not that hard to figure out why they'd give easily distinguishable names to their sublight and hyperlight propulsion methods rather than confuse the audience by using similar terms for both.

 

[Crazy Eddie]

So how fast is impulse? Depends on how long you've been accelerating. Theoretically an impulse engine could get you up to several times the speed of light if you had a big enough "runway" of open space, but it's still quite a bit slower than warp, so it's not a very efficient way to travel.

What? No, no, no. You can't accelerate to above the speed of light.

Absolutely you can. You just need to change the speed of light with respect to an outside observer. So to an observer INSIDE your subspace field, the speed of light is still 300,000km/s. Yet an observer on the outside would see photons passing through that field at several million km/s and then returning to "real" light speed on the other side of it.

Warp fields seem to work the same way, except the speed of light is biased in a particular direction so the ship "moves" without actually accelerating anywhere. Deflector shields probably work on a similar principle, changing the speed of light in a boundary region so everything that touches it has a natural tendency to move very quickly away from the ship.

It would take infinite time and energy to accelerate to exactly lightspeed

If you try to do it with a bottle rocket and a tank of kerosine, yes. When you have subspace driver coils to tinker with the laws of physics, all bets are off.

Or if you use a propulsive method like a lightsail or magnetic sail, something where the ship itself doesn't carry any fuel.

And even Bajoran sailing ships are capable of traveling faster than light. It turns out subspace fields aren't that hard to produce, in fact if you have a tachyon source and the right materials, you can even produce one ACCIDENTALLY.

 

[Christopher]

What? No, no, no. You can't accelerate to above the speed of light.

Absolutely you can. You just need to change the speed of light with respect to an outside observer. So to an observer INSIDE your subspace field, the speed of light is still 300,000km/s. Yet an observer on the outside would see photons passing through that field at several million km/s and then returning to "real" light speed on the other side of it.

You need to read up on your Einstein. The whole point of relativity is that the speed of light is always measured exactly the same by every observer in every frame of reference, no matter what. The speed of light is a fundamental factor in many laws of physics, and the laws of physics apply universally. That's what "relativity" means -- that the universe appears the same to all observers, that there's no preferred absolute frame of reference. This is why travelling at high speed relative to another observer causes time dilation and length contraction (as perceived by said observer). Speed is distance over time. You and the other observer are moving at different speeds relative to a beam of light, but you both have to observe the exact same speed of light or else the laws of physics don't work, so your perceptions of time and distance change to compensate for your motion. The (measured) speed of light in a vacuum is the only thing that is absolute.

Besides, what you're claiming here has nothing whatsoever to do with what you claimed before, that a ship could "get up to several times the speed of light" simply by accelerating at impulse. It's a total non sequitur.

Warp fields seem to work the same way, except the speed of light is biased in a particular direction so the ship "moves" without actually accelerating anywhere.

No, it has nothing to do with the speed of light. "Warp" means "distortion." A warp drive creates a pocket of spacetime that moves relative to the spacetime around it, carrying a ship with it inside the pocket. Since the ship is stationary relative to the space it occupies, it's travelling slower than light relative to that space. But spacetime itself is not material, so it has no limit on how fast it can expand, contract, or distort. So warp drive produces effective superluminal travel without affecting the speed of light in any way. The whole issue of lightspeed is simply bypassed.

Deflector shields probably work on a similar principle, changing the speed of light in a boundary region so everything that touches it has a natural tendency to move very quickly away from the ship.

Where are you getting this? Deflector shields are gravity fields. They push matter and bend light away from the ship.

 

[Gepard]

Besides, what you're claiming here has nothing whatsoever to do with what you claimed before, that a ship could "get up to several times the speed of light" simply by accelerating at impulse. It's a total non sequitur.

I think newtype is working from the "impulse is a non-Newtonian, warp field-like propulsion" hypothesis. That may also be the genesis of Myasishchev's "low warp" comment that you objected to.

 

[Crazy Eddie]

What? No, no, no. You can't accelerate to above the speed of light.

Absolutely you can. You just need to change the speed of light with respect to an outside observer. So to an observer INSIDE your subspace field, the speed of light is still 300,000km/s. Yet an observer on the outside would see photons passing through that field at several million km/s and then returning to "real" light speed on the other side of it.

You need to read up on your Einstein. The whole point of relativity is that the speed of light is always measured exactly the same by every observer in every frame of reference, no matter what.

Incorrect. The presence of a gravitational field (i.e. a non-inertial reference frame) changes the equation. A subspace field apparently has exactly the same effect, toying with space-time geometry in ways that are not conventinoally possible.

Geordi alluded to this in "Q-Less" (I believe it was) where Q suggests the only way to move the asteroid is "change the gravitational constant of the universe." Geordi, realizing this is impossible, does the next best thing: he extends the warp field around part of the asteroid, which has essentially the same effect.

The speed of light is a fundamental factor in many laws of physics, and the laws of physics apply universally.

Dude, you're talking about a TV show where starships, missiles, asteroids, even 1970s space probes regularly travel faster than light. It's obvious that scientists of the trekiverse have found this concept to be erroneous.

Besides, what you're claiming here has nothing whatsoever to do with what you claimed before, that a ship could "get up to several times the speed of light" simply by accelerating at impulse. It's a total non sequitur.

Not at all. You can... by accelerating AT IMPULSE. That's because of the way impulse engines work. You change spatial geometry in your own reference frame, then it doesn't matter what anyone else observes in THEIR reference frame. Both observers simply note the passing of one flipping enormous tachyon, but the light from said tachyon still arrives at the speed of light (relative to each observer) no matter what the actual observers are doing.

Warp fields seem to work the same way, except the speed of light is biased in a particular direction so the ship "moves" without actually accelerating anywhere.

No, it has nothing to do with the speed of light. "Warp" means "distortion."[/quote]
And a gravitational distortion does WHAT to light? Bends it, deflects it, changes its path.

When an object in motion changes its path, it is doing what? Accelerating. And since gravity is defined as a "fictitious force"--a distortion, if you will--then a gravitational field is a region of space within which every particle--even photons--have a tendency to move in a particular direction even when they are at rest. This means the speed of light is faster towards the center than away from it. This is the reason why black holes are black, by the way: at the event horizon, the speed of light in the "up" direction is exactly "zero."

Though warp drives operate on a different principle, the effect is exactly the same. Essentially it functions like a kind of gravity surfboard where every particle in the field has a natural tendency to move in one direction. The intensity of the field tells you how fast those particles move in that direction, just like the intensity of a gravitational field tells you how fast those particles fall into the barrycenter. A true warp field is rather like an event horizon this way: it is a distortion so great that all particles are accelerated in one direction at or faster than the speed of light.

That seems to be the constant in the Trekiverse, isn't it? The ability to control all fundamental forces--gravitational, electromagnetic, strong and weak--implies certain abilities that defy modern physics. If you can control gravity, there are all kinds of "constants" that fly right the hell out the window.

Deflector shields probably work on a similar principle, changing the speed of light in a boundary region so everything that touches it has a natural tendency to move very quickly away from the ship.

Where are you getting this? Deflector shields are gravity fields. They push matter and bend light away from the ship.

I believe I said that.

 

[Crazy Eddie]

Besides, what you're claiming here has nothing whatsoever to do with what you claimed before, that a ship could "get up to several times the speed of light" simply by accelerating at impulse. It's a total non sequitur.

I think newtype is working from the "impulse is a non-Newtonian, warp field-like propulsion" hypothesis.

No. Impulse engines are basically fusion rockets where part of the exhaust energy powers a driver coil that screws with local space geometry. You could think of it light a jet engine hooked up to an electromagnet; a jet-powered car can only go so fast due to ground friction, but if have it levitating on a magnetic field it can go as fast as a jet fighter.

Perhaps a more direct analogy would be a supercavitating torpedo. A normal torpedo has to deal with drag from the water, but a torpedo with a rocket motor can inject some of the exhaust gases through the nosecone to create a supercavity, eliminating friction altogether. An impulse engine is basically a newtonian engine with a "cheat," the driver coils that stack the action/reaction balance so you get more buck for your bang.

 

[Myasishchev]

Where are you getting this? Deflector shields are gravity fields. They push matter and bend light away from the ship.

Gravity doesn't push.

 

[Cary L. Brown]

Besides, what you're claiming here has nothing whatsoever to do with what you claimed before, that a ship could "get up to several times the speed of light" simply by accelerating at impulse. It's a total non sequitur.

I think newtype is working from the "impulse is a non-Newtonian, warp field-like propulsion" hypothesis. That may also be the genesis of Myasishchev's "low warp" comment that you objected to.

I think Newtype and I are on the same page as far as "FTL impulse" goes. I doubt very much that he needs to "read up on Einstein," particurly when you realize that most of what people think of as Einsteinian is only a SIMPLIFIED version of those equations (the E=mc^2 equation only holds when certain terms are dropped out... as they do at speeds wherein we're accustomed to seeing).

Christopher, I know you've heard this one before... so I'm not at all sure why you consistently act as though you've never heard it. But anyone who has never heard it:

"Impulse" is a classical, newtonian term. It as absolutely, undeniably Newtonian. You can no more redefine that term than you can redefine "mass" or "velocity" or "acceleration."

Still, we know (without ANY room for debate) that in TOS, and at least a few cases in TNG-era shows, that "impulse" can be FTL.

How can that be?

Simple... and there's plenty of in-universe backup for this (both in TOS and in TNG-era times).

We know two things about "subspace fields," both 100% canonical.

1) Subspace fields reduce the "apparent mass" of an object (that is, the amount of an objects "real" mass which is seen by the "real" universe). This was used several times in TNG, and in the pilot to DS9, and probably a few other times as well.

2) Static subspace fields are NOT "warp fields," but allow the local speed-of-light to be increased to a speed greater than that seen in the "real" universe. This, again, is repeatedly and consistently seen in TNG-era "treknology." The most common application of this is in the TNG-era "ftl computers."

We also know the following:

1) The Romulan War was fought with "impulse only" craft... pretty ludicrous unless you're willing to accept decades between engagements, isn't it? Of course, if you have "FTL impulse" you can get around that.

2) TOS shuttlecraft have both a central "impulse engine" and nacelles. Why both? We're also led to understand that these ships aren't "warp capable" but we know that they're capable of doing things that are 100% clear as being impossible (or at least utterly impractical) if they're sublight-only. Every time we saw one in TOS we see it doing something that would be ludicrous to try with a sublight-only craft, except for when they were being used to search for a craft which couldn't have been lost as it was if it were sublight-only.

3) The Enterprise tried to cross the "barrier" and lost its warp drive, and yet was able to travel to another star system, not years later or decades later, but just a matter of DAYS away. There are no star systems anywhere outside of the galactic core where they are mere "light days" away. In our local neighborhood, we're talking about light-YEARS between star systems. As you get further from the center, they're spaced further apart, as well. In other words... IT HAD TO TRAVEL FTL to get to Delta-Vega.

4) We know that sometime between the crash of Vina's transport and the "rescue" by the Enterprise (under Pike), there was a breakthrough in FTL transportation which was a "quantum leap" in technology.

5) We know that the Bonaventure was the "first ship with Warp drive" but it's clearly not the first FTL ship (you can disregard this point if you're inclined to reject TAS, but I don't do so, personally).

(Now, the series "Enterprise" sort of contradicts a lot of this... but where two series contradict each other, I choose to accept the SOURCE material (aka the earlier work) as being "more true." The later stuff needs to be fixed, to match the original, not the other way around, in other words.)


Okay... so, put this all together, and what do you get?

"Static-subspace-bubble Impulse Drive."

Generate a static (non-"warped") bubble of subspace around your ship. This allows you to accelerate much faster, and to a speed much higher, than you can in "real" space/time, but you're still using Newtonian techniques. Just "modified" Newtonian calculations, with the modifiers associated with C and with m.

Perhaps generating an appropriately-sized Subspace bubble reduces your "projected mass" on the real fabric of space-time to 1/100 of a percent of your "real mass... or 1/10,000. This means that, for a given thrust output, you'd accelerate 10,000 times faster than you would without that "subspace" boost, then your inertial effects (as seen by you, from inside the "bubble" would be similarly affected... meaning that you wouldn't see F=ma effects as though it were in "real" space/time at that acceleration, but only as seen within your "pocket universe" bubble.

So, you produce propulsive acceleration at 700m/s^2. Apply that in "real" space/time over ten seconds, and you accelerate to 7,000m/sec. But apply it in the "static subspace bubble" (assuming that 1/10,000 ratio, which I'm sure wouldn't be the REAL number, just one I chose for ease-of-understandint)....

... and you see (internally) the equivalent of 700m/s^2 acceleration, but (externally) something more like 7,000,000m/s^2 acceleration.

Furthermore, since the "local speed of light" inside this little pocket universe you're inside of (the "static subspace bubble" isn't REAL space/time, though it's very nearly "colocated" with "real" space/time) is higher (relative to real space/time)... well... it's almost as though the outside universe "looks smaller" from inside the bubble.

You're still seeing the speed of light as a constant... but whereas the moon is about eight light-seconds from earth in "real" space/time, if you're inside this bubble, it might be 1/8 of a second away... not because you're (locally) going faster, but simply because the SCALE is different viewed from these two different perspectives.

It's commonly accepted that (due to our current understanding of relativistic physics) about 0.75c is the "speed limit" before you start to see unacceptable effects due to time-dilation. Well, I've kind of arbitrarily (based less upon hard-science and more upon fictional "trek history") determined that the "FTL impulse" speed limit... where you start to see relativistic effects within this subspace-bubble "pocket universe"... is 75c.

Why 75c?

Well, several reasons... first off, it's consistent with a relatively small range of reachable systems, but allows for interstellar travel easily enough.

Second... using the old (WF^3)*C = V formula (nearly universally accepted before TNG came along and "redefined" the scale), this is the equivalent of WF4.2, which is what was defined about the time of TMP by Sternback and Co in the Starflight Chronology as the "speed limit." So I'm paying homage to that.

Third... it allows you to keep 99% of what we see, on-screen, in "Enterprise" without having to "redefine" any of the real storytelling. "WF4.2" is certainly the range that our hero's ship tends to travel at most of the time. If you can "retcon" away the "warp speed" nomenclature, everything else from "Enterprise" can be kept. (If you don't do that, you have to toss away a lot of TOS/TAS stories, however)

Finally, it seems to fit well with all the other on-screen evidence (including the shuttlecraft pursuit in "The Menagerie") from TOS. And still leaves Jose Tyler's "you won't believe how fast we can get back" making a certain amount of sense!

The one final piece of evidence comes from the change in terminology from the time of Pike to the time of TOS... Pike was using far more formalized language ("Time Warp Factor" and so forth) than was in use a short time later. This infers that when Pike was using it, the technology was still reasonably new, and hadn't fallen into slang-usage yet. Sort of like how when the Army replaced it's jeeps and pickups, the vehicle they did this with was the High-Mobility Multi-Wheeled Vehicle, and that's what we called it. The abbreviation was HMMWV. Over time, this became to be "slang-i-fied" into "Hummvee." And then "Hummer."

We know that there was an FTL propulsion breakthrough not long before "The Cage." We know that impulse is a newtonian term. We know the effect of static subspace fields. We know that "impulse" must be able to drive a vehicle FTL in the Trek universe.

The only solution I've ever seen that really matches EVERY requirement... both real-physics and "trek historical" in nature... is the "FTL impulse as real newtonian propulsion inside of a static subspace bubble" explanation.

It's all make-believe, of course, so there is no "right" answer. But unless you're willing to toss aside either our understanding of real-world physics, or a major portion of Trek-universe fiction, I don't think you can accept any other solution.

You're welcome to disagree, of course. But please at least stop pretending you've never heard the argument before, K?

 

[Brent]

A lot of people say that impulse is warp-lite, so .5c-ish is possible. Begs the question why they don't just call it low warp.

Probably because impulse involves fusion reactors, whereas the warp drive involves subspace travel.

I always thought impulse was developed in the early 21st century (the stuff that made sleeper ships obsolete) and Cochrane's warp was developed in 2063.

23rd and 24th century impulse probably developed ten times faster than 21st century impulse.

A "hyper-impulse drive" existed in the 29th century, which may have been some sort of non-subspace but FTL drive (if that's even conceivable).

My theory on what Hyper Impulse is:

Since 29th century Starfleet vessles are capable of time travel, the hyper impulse allows lower than 1c travel, think like .9c WITHOUT the effects of time dilation. Therefore, they can travel at .9c, right up to the edge before you go to Warp, without suffering from time passing quickly around them, they stay in the current time to the rest of space.

 

[Timo]

A couple of points that I thought were argued down recently already?

We also know the following:

1) The Romulan War was fought with "impulse only" craft... pretty ludicrous unless you're willing to accept decades between engagements, isn't it? Of course, if you have "FTL impulse" you can get around that.

The Romulan War was fought with primitive ships that had primitive atomic weapons. Absolutely nothing was said about their method of propulsion, or capabilities inherent in that method. For all we know, Romulan ships in that war were actually markedly faster than the one Kirk encountered in "Balance of Terror", just like destroyers in WWII were markedly faster than destroyers today.

2) TOS shuttlecraft have both a central "impulse engine" and nacelles. Why both? We're also led to understand that these ships aren't "warp capable" but we know that they're capable of doing things that are 100% clear as being impossible (or at least utterly impractical) if they're sublight-only.

How are we "led to understand" that these craft aren't warp-capable? There is no TOS episode to my knowledge that would make the statement or even the suggestion. And as you say, there are several episodes where the craft move at high speeds that are probably best interpreted as warp.

3) The Enterprise tried to cross the "barrier" and lost its warp drive, and yet was able to travel to another star system, not years later or decades later, but just a matter of DAYS away. There are no star systems anywhere outside of the galactic core where they are mere "light days" away. In our local neighborhood, we're talking about light-YEARS between star systems. As you get further from the center, they're spaced further apart, as well. In other words... IT HAD TO TRAVEL FTL to get to Delta-Vega.

But the episode is explicit about Delta Vega being a few light days away, not merely a few travel days. The distance is fixed in unambiguous terms, and there is no requirement for FTL drive if one crosses a few light days in a few days.

Of course, Kirk didn't travel from star system to star system. He merely traveled from where he was to Delta Vega. There's no natural law that would dictate he couldn't have been within a few light days of Delta Vega to begin with. Hell, perhaps he took a path towards the Galactic Barrier that grazed Delta Vega specifically because he wanted to use Delta Vega as a base camp!

Also, a bit of musing:

5) We know that the Bonaventure was the "first ship with Warp drive" but it's clearly not the first FTL ship (you can disregard this point if you're inclined to reject TAS, but I don't do so, personally).

For all we know, the ship could literally have been the first one "with warp drive fitted", as the dialogue goes. Only it then shouldn't have been the ship we saw prominently at the center of the viewscreen, because that ship looks a bit too modern. Unless, of course, the Bonaventure was refitted more often than the ship of Theseus, out of respect to this venerable grandfather of all vessels.

But then again, the episode dialogue could refer to some other ship seen elsewhere on that viewscreen - the name Bonaventure is painted nowhere on the hull of the centerpiece ship, after all.

Timo Saloniemi

 

[buzzknox]

I was rewatching STIII the other day, and noted that both Kirk and Stiles ordered 1/4 impulse when departing Spacedock. In the case of the Enterprise, that resulted in a fairly slow reverse thrust (which indicates a glaring script error as a reverse thrust order would have been appropriate).

That would indicate that impulse is not a reaction based drive system as some argue. There were materials in the area that would have been affected by any fusion byproducts, particle streams, etc consistent with a reaction drive.

It also shows that the acceleration provided by impulse is measured in "units of plot" rather thank KPS.

 

[Plecostomus]

KPS: Korny Plots Per Second.

 

[SicOne]

Didn't NX-02 Columbia have to travel at super-high impulse in the first Destiny book, trying to use relativistic speeds to compress the subjective duration of their journey, when they encountered the Caeliar?

 

[Timo]

I was rewatching STIII the other day, and noted that both Kirk and Stiles ordered 1/4 impulse when departing Spacedock.

Do I recall correctly that they both specified "1/4 impulse power", instead of the more usual "1/4 impulse", when starting up their starships?

One might speculate that the two captains minded the regulation that precludes impulse engine use within Spacedock, but had their engines ramped up in advance to the power required for implementing 1/4 impulse as soon as they cleared the doors.

Timo Saloniemi

 

[buzzknox]

I was rewatching STIII the other day, and noted that both Kirk and Stiles ordered 1/4 impulse when departing Spacedock.

Do I recall correctly that they both specified "1/4 impulse power", instead of the more usual "1/4 impulse", when starting up their starships?

One might speculate that the two captains minded the regulation that precludes impulse engine use within Spacedock, but had their engines ramped up in advance to the power required for implementing 1/4 impulse as soon as they cleared the doors.

Timo Saloniemi

I thought Kirk at least called for 1/4 impulse but will recheck.

 

[Saturn0660]

Think of it like naval vessels. 1/4 speed is not the same for all ships. Much like top speed isn't the same. Think of fleet actions. The carriers flank speed might be slower then an escorts flank ship. Starships are 100% the same.
Some ships full impulse might be say .95c where another might be .65c.

 

[Jadzia]

I think they used 'inertial dampeners' to reduce the effective mass of the ship, making it easier to accelerate with less thrust.

This might explain discrepancies between observations: Coming out of dock, a ship is seen crawling along at quarter impulse, taking ten seconds or more to travel it's own length, while another ship is supposed to be going a fraction of light speed at quarter impulse. It might be that the inertial dampeners were offline while in dock?

 

[buzzknox]

In STIII, Kirk and Stiles do in fact both call for impulse power. The confusion came because Sulu responded with "1/4 impulse" rather than "impulse power." Either they use the terms interchangeably or Sulu's discipline was a little lax.

In STVI, Kirk calls for 1/4 impulse power and Valeris reminds him that regulations only allow for thrusters in spacedock. He repeats the impulse command. I think that shows that a call for impulse power in this context is an engine order, and not just a command to prep for the use of impulse power. It also shows a cear distinction between thrusters and impulse engines.

 

[MarianLH]

I think Cary L. Brown pretty much nailed it. And while STIII may imply a lack of exhaust by inference, in at least two cases (ST VI and TNG's "Preemptive Strike") such an exhaust explicitly existed and was used as a plot point.


Marian