Impulse Drive, Therories on how it works?

[Go-Captain]

...How fast an impulse drive achieves any given speed in Trek is unknown, by and large. Impulse travel is seldom if ever directly associated with speeds: "Full impulse!" may be commanded, but what is achieved with it and when is not explicated.

Impulse commands may be speed settings or then throttle settings. Given how it is possible for us to estimate impulse speeds even when they are not explicated, and given how the same command may yield extremely different speeds (cf. the crawling achieved with "One quarter impulse!" in the TOS movies), the evidence would seem to point towards throttle settings, with different engines then giving different accelerations which translate to different speeds depending on the duration of acceleration (and, thankfully, making "contradiction" an inapplicable concept here!).

All the calculable moments of impulse I recall put the speeds in the high 70% to high 90% speed of light, I think the episodes are the one where Voyager flies between a pair of stars, All Good Things, and an ENT episode where only T'Pol is awake and thinks Phlox is with her and they have to escape a black hole. If you don't account for time dilation is goes slightly above the speed of light.

Two of the most interesting impulse situations which aren't calculable are in "Shuttlepod One" and The Motion Picture. In the former I believe they state the pod speed maxes out at 1/4 impulse, and in the latter they call out sub-warp speeds as 0.# warp fractions.

The thing is if impulse works more like real life warp theory then it does depend on the normal energy and field strength combined. The field acts as a speed magnifier, while the normal engine provides real space velocity (speed and heading) and acceleration. Alternatively, it is just a low level warp field, and some ships have engine bells is just an expression of uncertainty in the technology, or an expression of its power intensity and that it cannot be used all that much early on.

 

[Henoch]

The Enterprise got towed by Balok's ship at 0.64 c. I am surprised that the highly advanced First Fed ship was at sublight speeds and not towing at warp speed. Kirk and crew don't seem too surprised at 0.64 c speeds, so, I surmise that those speeds are capable to be reached by the Enterprise at impulse.

 

[Timo]

Two of the most interesting impulse situations which aren't calculable are in "Shuttlepod One" and The Motion Picture. In the former I believe they state the pod speed maxes out at 1/4 impulse, and in the latter they call out sub-warp speeds as 0.# warp fractions.

Interesting points both. If "impulse" is a throttle setting, why does the shuttlepod have a throttle lever that refuses to go past the 1/4 mark? Or, why would the heroes discuss the performance of their shuttlepod in relation to the performance of their mothership, when they aren't trying to outrun her or anything? (However, I can't spot any reference to 1/4 impulse in the transcript?)

What is not calculable about ST:TMP? The heroes are sailing from Earth to Jupiter, being seen right next to both planets. No more than 1.8 hours have passed, unless we assume Kirk's log is not in sync with the visuals. The beeline distance would be between 4 AU and 6 AU, depending on how we want to date TMP (mid-2270s would give greater average distances than early or late ones, with Earth's own movement naturally accounting for about 2 AU of wobble annually). And at the speeds involved, the only reason to depart from a beeline would be if the Sun got in the way.

So it's about twice the speed of light, and we can fudge the acceleration profile relativistically pretty much any way we wish.

The thing is if impulse works more like real life warp theory then it does depend on the normal energy and field strength combined. The field acts as a speed magnifier, while the normal engine provides real space velocity (speed and heading) and acceleration. Alternatively, it is just a low level warp field, and some ships have engine bells is just an expression of uncertainty in the technology, or an expression of its power intensity and that it cannot be used all that much early on.

Famously, "engine bells" in Trek demonstrate lack of connection to rocketry in several ways: they point in whichever direction, they are far away from the supposed thrust line, they don't seem to involve an exhaust jet of any Newtonian sort because such would sometimes blast straight at the ship's own structures and both negate thrust and do damage, and their glow or lack thereof does not correlate with the ship's state of motion. Generally, they thus seem to be exactly what they are stated to be in ST6:TUC: "tailpipes", nonpropulsive exhaust routes for byproducts from the impulse process.

Since warp, too, has been shown to work fine even when impulse engines are down for the count, we may surmise that the mass-reducing, space-mangling subspace fields can be applied to create propulsion all by themselves. Perhaps through some sort of field asymmetry, even though this is mere noncanon backstagetalk - or perhaps through some sort of peristaltic pulsation, which we see on some display screens, its exact significance handwaved away.

Timo Saloniemi

 

[Mytran]

What is not calculable about ST:TMP? The heroes are sailing from Earth to Jupiter, being seen right next to both planets. No more than 1.8 hours have passed, unless we assume Kirk's log is not in sync with the visuals. The beeline distance would be between 4 AU and 6 AU, depending on how we want to date TMP (mid-2270s would give greater average distances than early or late ones, with Earth's own movement naturally accounting for about 2 AU of wobble annually). And at the speeds involved, the only reason to depart from a beeline would be if the Sun got in the way.

So it's about twice the speed of light, and we can fudge the acceleration profile relativistically pretty much any way we wish.

What is twice the speed of light? Not the speed they're travelling, that's for sure! Earth and Jupiter range from 628,743,036 km to 928,081,020 km apart.
1.8 hours equals 6,480 seconds
At most that's 143,222 KM/S or 0.48 times lightspeed, close enough to Kirk's order of "Warp 0.5" to make no difference IMO

 

[Timo]

Oops, yeah: the distance is about 50 lightminutes, and they do it in about 100, not vice versa.

When they do it in the reverse, in "Best of Both Worlds", that's where they (to wit, the Borg Cube) only spend 27 minutes doing the 50-minute run. But that's at their "current speed", which is after the Borg drop to impulse but also after they supposedly further stop to near-standstill in order to fight the Jupiter defenses.

Perhaps Riker and Crusher agree that "current speed" is the average of the Borg progress through Sol, factoring in all those droppings out of warp at Saturn and Jupiter and Mars and so forth, and the immediate returning to warp thereafter? That would work better in the given circumstances than assuming impulse, relativity, and a specific point of view. Even if it means we lose our chance to learn anything further about impulse speeds.

Timo Saloniemi

 

[Mytran]

I thought it (the website) the perfect balance between reading around the math to get the gist of it all and doing the math if you were into that.

Orbital mechanics are just something I never fancied getting into - I prefer triangles

I dunno, I think she is just being concise, giving her CO a brief summary of what he is seeing without getting into minutiae. So I think "and back" is implied. YMMV.

Yet she only says it took "years to travel from one planet to another" - the "and back" is conspicuous by its absence.

Oops, yeah: the distance is about 50 lightminutes, and they do it in about 100, not vice versa.

When they do it in the reverse, in "Best of Both Worlds", that's where they (to wit, the Borg Cube) only spend 27 minutes doing the 50-minute run. But that's at their "current speed", which is after the Borg drop to impulse but also after they supposedly further stop to near-standstill in order to fight the Jupiter defenses.

Perhaps Riker and Crusher agree that "current speed" is the average of the Borg progress through Sol, factoring in all those droppings out of warp at Saturn and Jupiter and Mars and so forth, and the immediate returning to warp thereafter? That would work better in the given circumstances than assuming impulse, relativity, and a specific point of view. Even if it means we lose our chance to learn anything further about impulse speeds.

Timo Saloniemi

I actually enjoyed (re)discovering that the speeds given in TMP are accurate to the furthest possible distance of Jupiter - although given the insane amount of detail put into the movie, perhaps I shouldn't be surprised!

The timing in those final few moments of BOBW is all out of whack. Sequential warp jumps are as good an explanation as any.

 

[Henoch]

What is twice the speed of light? Not the speed they're travelling, that's for sure! Earth and Jupiter range from 628,743,036 km to 928,081,020 km apart.
1.8 hours equals 6,480 seconds
At most that's 143,222 KM/S or 0.48 times lightspeed, close enough to Kirk's order of "Warp 0.5" to make no difference IMO

"Warp 0.5" must be slang for moving at Warp Factor 0.794 to achieve ~0.5 c...if you use the stupid warp factor cubed formula, Warp Factor 0.5 equates to only 0.125 c (0.5^3 c), or if the Cochrane Variable is 4.0, then Warp Factor 0.5 equates to 0.5 c (4x(0.5^3) c).

 

[Mytran]

That's not the only example either: After the asteroid incident Decker gives the Enterprise's speed at "Warp point-eight" so was the ship's actual speed 93% of the speed of light? Those are some impressive Impulse engines! Time dilation gets problematic at that speed though, with relative time on board running at only 37% to that of an outside observer. No wonder V'ger got so close to Earth!

Alternatively we could say that the cubed-factor formula thingy probably doesn't apply to "space normal" speeds.
Because of...reasons
TOP reasons.

The cubed WF formula really is dumb

 

[XCV330]

my take on it

Impulse something like a Woodward drive

the impulse drive creates an electromagnetic pulse across a dialectric body (the glowing thing on the end of the impulse drive) creating a transient mass displacement due to Mach effect, through banks of quick discharge capacitors (what powers them is not really important. some sort of reactor, probably) the dielectrics mass density will fluctuate asymmetrically under acceleration (more in the direction of thrust or "full ahead". the system has no exhaust, indeed requires no propellant, save the power put into it, so is not a rocket. The thrust of the impulse is equal to the mass fluctuations across a large dialectric (Some some sort of piezoelectric material) or multiple banks of said materials. The system is still confined by the rules of General Relativity, so unless there is some Star Trek magic gizmo able to prevent the ship from relativistic effects at near-light velocities, it in itself cannot reach c.

This would explain why warp drive was developed as a practicality before impulse. Both systems, being necessary to running a starship in the long term (Though a warp vehicle combind with chemical or nuclear rockets apparently works). Impulse drive has been shown to be able to go faster than light on occasion, and this must be assumed to have some sort of auxiliary system to still produce a warp bubble even if the warp drive itself is not entirely functioning.

 

[Henoch]

Those are some impressive Impulse engines!

No, they are using the Warp Engines at sublight speeds, not the Impulse Engines. This also voids the time dilation affects. The base formula gives Warp 0.8 = 0.8^3c = 0.512 c. If the Cochrane Variable is about 4 outside of a planet's gravity well for example, then Warp 0.8 could be 4x(0.8^3)c = 2 c.

 

[Tenacity]

the glowing thing on the end of the impulse drive

Did the Enterprise during the TOS TV series have a different system, because it certainly lacked any glow.

 

[Mytran]

No, they are using the Warp Engines at sublight speeds, not the Impulse Engines. This also voids the time dilation affects.

That would be handy but doesn't make much sense with the onscreen dialogue:

SCOTT: Intermix set. Bridge, impulse power at your discretion.
KIRK: Impulse power, Mister Sulu. Ahead, warp point five. ...
(Impulse Engines light up and the Enterprise zooms away from the camera)
...
Captain's log, stardate 7412.6. one point eight hours from launch. In order to intercept the intruder at the earliest possible time, we must now risk engaging warp drive while still within the solar system.​

 

[CorporalCaptain]

Yeah, warp point five is a sublight speed value for the impulse drive that's just measured on the warp scale (at least in the case of TMP).

 

[Henoch]

That would be handy but doesn't make much sense with the onscreen dialogue:

SCOTT: Intermix set. Bridge, impulse power at your discretion.
KIRK: Impulse power, Mister Sulu. Ahead, warp point five. ...
(Impulse Engines light up and the Enterprise zooms away from the camera)
...
Captain's log, stardate 7412.6. one point eight hours from launch. In order to intercept the intruder at the earliest possible time, we must now risk engaging warp drive while still within the solar system.​

Yikes, this is confusing. So, I guess this dialog establishes that impulse power is used to generate a low level warp field without using warp drive. This can probably remove/reduce the ship's mass making the impulse thrust more efficient plus negate the time dilation and other relativity effects. It may even be capable of FLT in interstellar space with favorable Cochrane values...

Checking their math: 1.8 hours at the lower speed of WF 0.5 = 0.125 c would move the ship to ~1.6 AU from Earth; still within the solar system but not out to Jupiter, yet. If WF 0.5 = 0.5 c, then after 1.8 hours they would be ~6.5 AU from Earth; also still within the solar system and depending on planetary positions, near or just past Jupiter as seen in the movie.

 

[CorporalCaptain]

Yikes, this is confusing. So, I guess this dialog establishes that impulse power is used to generate a low level warp field without using warp drive. This can probably remove/reduce the ship's mass making the impulse thrust more efficient plus negate the time dilation and other relativity effects. It may even be capable of FLT in interstellar space with favorable Cochrane values...

No, it doesn't mention that at all.

 

[Henoch]

No, it doesn't mention that at all.

You're correct. I'm stretching the dialog to where no man has gone before.

 

[Kamen Rider Blade]

https://imgur.com/aMvIw37

 

[Mytran]

Yikes, this is confusing. So, I guess this dialog establishes that impulse power is used to generate a low level warp field without using warp drive. This can probably remove/reduce the ship's mass making the impulse thrust more efficient plus negate the time dilation and other relativity effects. It may even be capable of FLT in interstellar space with favorable Cochrane values...

If the Impulse engines work on thrust then some sort of mass reduction field would be vital in order for them to reach 0.5c without running out of fuel in the first few seconds!
Is the field generated by the Impulse Engines? The TNG tech manual says so, although it also suggests that the inclusion of a subspace driver coil in the IE is a relatively recent development.

In DS9's pilot episode, O'Brien modified the station's deflectors to generate a subspace field around the station of sufficient strength to lower its mass by at least 60 times, and that was with equipment apparently not even designed for that function!

Would 23rd century deflectors be up to the task? Maybe not. But I'm sure those great big nacelles would be able to generate a meagre subspace field around the ship, just idling in standby mode. Manipulating energy fields many times as powerful is their bread and butter, after all.
BTW, this would not be the same as "engaging warp drive" since the nacelles aren't performing at FTL speeds, just giving the Impulse engines a little helping hand.

 

[Timo]

Simple. Blue glow = warp field tomfoolery. Many starships: blue glow only on nacelles. The ship in TMP: blue glow also right on top of the impulse engine.

So when ships desire high impulse performance, they get it from turning on either the blue lights in the warp nacelles, or the blue lights in the impulse engine. In TOS, the latter wasn't available, so the ship was wallowing like a garbage scow until and unless Scotty managed to activate the nacelles. But blue glow next to impulse systems is found in NX-01, NCC-1701-refit/A, -B and -D at least, and they can do high STL without pumping any power into warp nacelles.

Or then it's vice versa, and ships with the blue dome next to the impulse engine use that for manipulating the warp energies of the warp nacelles for mass reduction purposes, while ships that lack such a dome achieve the mass reduction with wholly internal impulse coils. Which doesn't work all that smoothly with TMP, though, even though it rather perfectly matches the backstage doubletalk associated with those blue domes on NX-01 and NCC-1701-refit/A

Timo Saloniemi

 

[Deks]

Weren't we given an explanation for how 24th century sublight engines work?
O'Brien and Dax in DS9 pilot suggested that starships usually generate their own low level subspace fields to both maneuver and achieve high speeds at sublight.

Without this field, you wouldn't be able to lower the mass of a given object to achieve needed speeds or maneuverability we see for both fighter/shuttle class ships and large ships.

So, subspace technology is the underlying needed baseline needed to achieve these speeds.
I think the technical manuals say a ship can move at about 75 000 km per second (which is 1/4 of light speed).
Obviously, on-screen, we've seen ships achieve higher speeds than that using impulse.

Thrusters work more along the lines of 'standard rockets' but I suspect they don't use 'propellant' in the same sense but likely ample supply of what is generated on board using recycling, excess matter and existing storage.

Impulse engines have no visual exhaust that we've really seen and are highly efficient.
We've also seen how ships can travel in REVERSE at both impulse and Warp speeds (TOS used Warp in reverse in the Corbomite maneuver episode if I'm not mistaken, and TNG showed that you can engage full impulse in REVERSE).

This implies that a subspace field might actually be needed for effective Impulse travel (and obviously Warp)... as you can use it to push the ship both forward and backwards at either Impulse or Warp... in essence, neither Impulse or Warp engines have to face forward or backward as they don't seem have exhaust per say, but rather, you manipulate the FIELD generated by the whole ship by Impulse or Warp engines.

A low level subspace field is perhaps needed for Impulse drive to function, whereas a higher powered one would be required for Warp drive use.