Impulse Drive: What do we know? (Non-canon speculation)

[Crazy Eddie]

As for the attack ship, the entire rear pod is lined with large exhaust grilles that are clearly not part of the warp drive and just as obviously meant to be interpreted as an impulse engine of sorts. Considering the attack ship is already meant to be something of a diving/swooping speed demon at impulse, what is the reason not to interpret this as a very high-capacity impulse engine?

Well didn't we set that standard before?
Large Glowy things and what-not?
If you're interpreting the bottom belling of the ship to be an impulse engine exhaust, may I remind you that this orientation has absolutely no design benefit for the ships identified forward moment?

Since the glowing grillework is on the REAR of the ship and only has clearance facing directly off, I'm not sure what point you're making.

The question is: Is it separate from the RCS thrusters?

Probably. The tech manuals certainly suggest they are. And I can't think of any good reason why the ship's primary maneuvering thrusters would be using chemical propellants, unless 24th century tech is a lot less advanced than we'd like to believe (it very well might be, but I prefer to avoid that option as most TrekBBSers tend to find that possibility very upsetting).

That wasn't the question I recall.

Then why did you even bring up the forcefield around the Enterprise' warp core?

 

[blssdwlf]

The Trek fact of the matter is that the ship always moves bow first

That's not completely so, especially for pre-TNG stuff. The Reliant is moving backwards in relationship to the Enterprise when they first encounter each other in TWOK. Enterprise makes a "conical interception" of V'ger and looks it over front and back. You've got TOS episodes where the wonky FX has the ship not always going straight ahead but you also have episodes where the ship moves laterally, in reverse, etc.

Using warp drive in orbit is plenty possible. Kirk did it with the BOP in TVH, used it to escape PSI2000 in "The Naked Time" and zip around a couple of suns. The TOS warp drive shouldn't have a problem being used at subwarp speeds at all. The TNG+ warp drives, OTOH, might have a problem the way they are written as they don't appear as flexible but probably could work as well given how they use subspace fields to move DS9.

I hadn't considered it until this thread that the "glowy exhausts" might not be providing thrust but merely radiation vents as mentioned in "Obsession"....

However, there isn't any reason to assume that warp and impulse use the same kind of field drive. Warp isn't called "super impulse" or "turbo impulse" and impulse isn't called "baby-warp". Perhaps impulse fields are not very efficient and require far more thrust (fuel) to move a ship than warp fields but are kept around because they are different field types and impulse fields are more reliable for emergency use (in TOS)? In TNG, the production folks made an effort to put impulse as a sublight-only system so I understand TOS wouldn't apply to TNG tech

 

[Saquist]

Since the glowing grillework is on the REAR of the ship and only has clearance facing directly off, I'm not sure what point you're making.

I guess my point would be it's on the bottom, not the rear.
That's what I said in the previous post. No one would design and engine for the specific necessity of a 90 degree articulation of thrust.

The purpose of the glowing bottom section of the bug ship is pure speculation, we have no idea.
Probably. The tech manuals certainly suggest they are. And I can't think of any good reason why the ship's primary maneuvering thrusters would be using chemical propellants, unless 24th century tech is a lot less advanced than we'd like to believe (it very well might be, but I prefer to avoid that option as most TrekBBSers tend to find that possibility very upsetting).

I can't see a problem with it you're already speculating impulse engines are pretty much the same. Large amounts of fuel would still be required for both and it's a capacity the ship can't sustain.

That wasn't the question I recall.

Then why did you even bring up the forcefield around the Enterprise' warp core?[/QUOTE]

I didn't , Timo did.

 

[shipfisher]

Might be late to the party here, but please endure my 2 bits worth.

Impulse drive - Diane Carey's "Internally Metered PULSE" aside, the term suggests a pulsed-thrust principle, perhaps tuned to an oscillating, inertial mass damping subspace field courtesy of those nifty "driver coils". Tune the thrust pulse maxima to surf out along the local field minima with most of their inertial punch intact, while the ship experiences an overall field average mass dampening effect and viola, we have a Newtonian rocket punching well above its weight. We'll assume the field also conveniently transfers the accelerative forces smoothly and uniformly throughout the ship. Thrust reversing shield configurations would get fairly involved to preserve performance, which would probably be reduced.

The above is my favorite scenario, however the idea that the term impulse drive encompasses a whole slew of different propulsion principles in trek can't be dismissed. The canon tech references to it are pretty thin and far between.

 

[Mister_Atoz]

I agree that "Warp Drive" and "Impulse Drive" are probably broad umbrella terms for different types of engines that use similar principles. It would sort of be analogous to the terms "Nuclear Powered" and "Conventionally Powered" used today.

 

[Santaman]

As for the so called impulse exhaust, no.. its the exhaust of the fusion reactors, doesn't do anything thrust wise but gets rid of waste material and heat...

Why the hell would you want to vent the exhaust from a fusion reactor? 99% of the exhaust is un-fused deuterium, the rest is ionized helium. There is literally NO reason to dump the "exhaust" from a fusion reactor that hasn't been completely fused into helium, UNLESS you're using it as a propulsive reactant mass. If the exhaust itself produces no thrust then there's no reason to get rid of it, just run it through the driver coil and cycle it back into the fusion reactor.

Easy, to get rid of heat, also, in TUC thats exactly the downfall of the BOP, it got hit right into its tailpipe..
Besides that I assume that by the time its vented the exhaust won't contain anything usable.

 

[John O.]

I agree that "Warp Drive" and "Impulse Drive" are probably broad umbrella terms for different types of engines that use similar principles. It would sort of be analogous to the terms "Nuclear Powered" and "Conventionally Powered" used today.

I think it's almost always implied by the context that there's a fundamental difference in the physics going on, though, between impulse and warp. It might be more of an appropriate contemporary analogy to refer to subsonic versus supersonic flight. Assuming the 'superluminal barrier' is in fact just an engineering barrier as the sound barrier was, the analogy holds.

 

[Crazy Eddie]

Since the glowing grillework is on the REAR of the ship and only has clearance facing directly off, I'm not sure what point you're making.

I guess my point would be it's on the bottom, not the rear.
That's what I said in the previous post. No one would design and engine for the specific necessity of a 90 degree articulation of thrust.

I'm looking at the orthos for the jem'hadar attack ship.
The grilles have plenty of clearance directly aft of the ship.
No "90 degree" articulation is required or even implied.
What are you talking about?

I can't see a problem with it you're already speculating impulse engines are pretty much the same.

Actually I'm speculating that impulse engines (not "the" impulse engines) by definition are any engine that requires some application of force over distance to move the ship, thus differentiating it from a warp drive, which imparts no force whatsoever and produces movement by the warping of space. The TNG tech manual clearly describes this as a newtonian thrust-generating system using fusion reactor exhaust as a reactant mass and a subspace driver coil to massively increase the engine's ISP. I stated upthread that other impulse engines may use any number of methods; reactant mass, particle beams, magnetic fields, artificial gravity pulses, nuclear explosions, whatever; the thing that makes them IMPULSE engines as opposed to WARP engines is that they produce movement by applying force, not by warping space.

I'm not really sure what the hell that has to do with the canonical fact that emergency thrusters use chemical propellants and are (IMO) probably not related to RCS thrusters. Unless you're trying to claim that RCS thrusters are also warp drives...

That wasn't the question I recall.

Then why did you even bring up the forcefield around the Enterprise' warp core?

I didn't , Timo did.

 

[Crazy Eddie]

As for the so called impulse exhaust, no.. its the exhaust of the fusion reactors, doesn't do anything thrust wise but gets rid of waste material and heat...

Why the hell would you want to vent the exhaust from a fusion reactor? 99% of the exhaust is un-fused deuterium, the rest is ionized helium. There is literally NO reason to dump the "exhaust" from a fusion reactor that hasn't been completely fused into helium, UNLESS you're using it as a propulsive reactant mass. If the exhaust itself produces no thrust then there's no reason to get rid of it, just run it through the driver coil and cycle it back into the fusion reactor.

Easy, to get rid of heat

Then you should be dumping coolant, not exhaust product. And even then you would have virtually no need to dump the coolant through an enormous thermal exhaust port on the back of the ship; you could put the ports anywhere you want to, and even ray shield them so Luke Skywalker has to use proton torpedoes.

I agree that "Warp Drive" and "Impulse Drive" are probably broad umbrella terms for different types of engines that use similar principles. It would sort of be analogous to the terms "Nuclear Powered" and "Conventionally Powered" used today.

I think it's almost always implied by the context that there's a fundamental difference in the physics going on, though, between impulse and warp. It might be more of an appropriate contemporary analogy to refer to subsonic versus supersonic flight. Assuming the 'superluminal barrier' is in fact just an engineering barrier as the sound barrier was, the analogy holds.

That's completely backwards, since a jet engine can work just as well at subsonic as well as supersonic speeds. "Conventional" and "nuclear" powered engines WOULD be consistent with two completely different physical processes, enough to fit the analogy between impulse and warp drives in the same way. That impulse engines can be used at FTL velocities would also reflect this, much the way a nuclear-powered aircraft can probably achieve hypersonic velocities alot more effectively than an ordinary turbojet.

 

[Mytran]

Actually I'm speculating that impulse engines (not "the" impulse engines) by definition are any engine that requires some application of force over distance to move the ship, thus differentiating it from a warp drive, which imparts no force whatsoever and produces movement by the warping of space. The TNG tech manual clearly describes this as a newtonian thrust-generating system using fusion reactor exhaust as a reactant mass and a subspace driver coil to massively increase the engine's ISP. I stated upthread that other impulse engines may use any number of methods; reactant mass, particle beams, magnetic fields, artificial gravity pulses, nuclear explosions, whatever; the thing that makes them IMPULSE engines as opposed to WARP engines is that they produce movement by applying force, not by warping space.

I like the idea that "impulse" and "warp" are just general terms - it gives a lot more flexibility to the tech applications.

I had another thought - if the impulse engine "sub space driver coil" reduces the overall mass of the vessel in increasing amounts, it should be possible for the ship to accelerate to near lightspeed using comparatively little thrust (of course, the ship would need to have a mass of virtually zero by this stage).

If the decrease in mass continued (using a stronger and stronger subspace field), could a ship have zero mass? Negative mass? Might this be a way for an impulse engine to reach FTL speeds?

 

[Saquist]

I'm looking at the orthos for the jem'hadar attack ship.
The grilles have plenty of clearance directly aft of the ship.
No "90 degree" articulation is required or even implied.
What are you talking about?

That maybe but it does not standard fit we know of as a Rocket or Engine. It's pure speculation. As size goes they've never displayed any superior maneuverability that isn't merely a quality of it's size rather than engine power and output. The thing is I think they are impulse engines but not a Rocket because such a Rockt with Exhuast of that size would be expending prodigous amounts of fuels and the quality of thrust management requires chambered restriction to produce that thrust. You won't get that with an exhaust that size. That's primitive. Like the ideas of nuclear blast propelling a ship.

Side Note;
I noticed one occasions where thrusters were used at impulse speeds. In Shattered Mirror Sisko tells Smiley to fire thrusters at 1/4 impulse.

 

[Santaman]

Why the hell would you want to vent the exhaust from a fusion reactor? 99% of the exhaust is un-fused deuterium, the rest is ionized helium. There is literally NO reason to dump the "exhaust" from a fusion reactor that hasn't been completely fused into helium, UNLESS you're using it as a propulsive reactant mass. If the exhaust itself produces no thrust then there's no reason to get rid of it, just run it through the driver coil and cycle it back into the fusion reactor.

Easy, to get rid of heat

Then you should be dumping coolant, not exhaust product. And even then you would have virtually no need to dump the coolant through an enormous thermal exhaust port on the back of the ship; you could put the ports anywhere you want to, and even ray shield them so Luke Skywalker has to use proton torpedoes.

Well... now you mention it.. the thing at the back of the saucer can't be an exhaust port.. its covered by a grill like those on the nacelles, good point, even more proof that impulse engines are non newtonian.

 

[Crazy Eddie]

I had another thought - if the impulse engine "sub space driver coil" reduces the overall mass of the vessel in increasing amounts, it should be possible for the ship to accelerate to near lightspeed using comparatively little thrust (of course, the ship would need to have a mass of virtually zero by this stage).

If the decrease in mass continued (using a stronger and stronger subspace field), could a ship have zero mass? Negative mass? Might this be a way for an impulse engine to reach FTL speeds?

Or it could go the other way around in some designs, INCREASING the mass of the propellant relative to the ship while retaining its exhaust velocity. That would accomplish about the same effect with a much smaller subspace field, although the acceleration imparted on the ship would be far greater and would require heavier use of inertial dampeners.

 

[Crazy Eddie]

That maybe but it does not standard fit we know of as a Rocket or Engine.

Oh really?

The thing is I think they are impulse engines but not a Rocket because such a Rockt with Exhuast of that size would be expending prodigous amounts of fuels and the quality of thrust management requires chambered restriction to produce that thrust.

Since when? Fuel consumption of most MODERN rocket engines has practically nothing to do with their nozzle size and everything to do with chamber pressure. In ion engines and magnetoplasma drives it's purely a function of power output, and in nuclear-thermal designs it's a function of reactor temperature.

All of which, by the way, would be classified as "impulse engines" under the scehem I suggested. As far as the Jem'hadar, a type of relativistic particle beam like an ion drive on steroids would seem to fit the bill, especially if the Jem'hadar fighters are expected to make very long voyages without regular refueling stops and layovers.

Well... now you mention it.. the thing at the back of the saucer can't be an exhaust port.. its covered by a grill like those on the nacelles, good point, even more proof that impulse engines are non newtonian.

Heh? The grillework on the impulse engine looks nothing like the warp nacelles. It's a porous grid, in fact it's almost identical to the exhaust vent on the HiPep ion thruster.

 

[Mytran]

I had another thought - if the impulse engine "sub space driver coil" reduces the overall mass of the vessel in increasing amounts, it should be possible for the ship to accelerate to near lightspeed using comparatively little thrust (of course, the ship would need to have a mass of virtually zero by this stage).

If the decrease in mass continued (using a stronger and stronger subspace field), could a ship have zero mass? Negative mass? Might this be a way for an impulse engine to reach FTL speeds?

Or it could go the other way around in some designs, INCREASING the mass of the propellant relative to the ship while retaining its exhaust velocity. That would accomplish about the same effect with a much smaller subspace field, although the acceleration imparted on the ship would be far greater and would require heavier use of inertial dampeners.

That's a nifty idea! It would certainly work well for very large ships (ie Galaxy Class) since it would dispense with the neccessity for large SS bubbles. However, the strain on Inertia Dampeners etc would put a limit on how fast such a ship could travel - say 0.25c?

 

[Santaman]

Well... now you mention it.. the thing at the back of the saucer can't be an exhaust port.. its covered by a grill like those on the nacelles, good point, even more proof that impulse engines are non newtonian.

Heh? The grillework on the impulse engine looks nothing like the warp nacelles. It's a porous grid, in fact it's almost identical to the exhaust vent on the HiPep ion thruster.

Except that there's absolutely nothing exhausted, in TMP we see it right in the throat when the 1701 accelerates at full impulse and there's zero exhaust coming from it.

As for the ion engine, definitly a visible trail.

 

[Timo]

Invisible exhaust wouldn't be all that unusual - many rocket exhausts today manage to be invisible to the naked eye even within Earth's atmosphere.

And we know for a fact that impulse leaves some sort of a footprint: there's the exhaust from ST6, and the marks on the Dyson Sphere from "Relics". Something does come out, although we don't know if it comes out of the glowing bit. And ST6 is pretty explicit that this something is plasma.

Since tracking by impulse trail has never worked anywhere in Trek, the tracking in ST6 may have involved occasional burps of plasma rather than a constant propulsive jet. Doesn't completely rule out the use of said plasma as a Newtonian propellant, though: the villain ships being tracked might only occasionally fire their Newtonian rockets and mostly coast, even if (and regardless of whether) typical innocent starships tend to have their Newtonian impulse engines active 100% of the time.

The main argument against impulse engines being rockets or vectored rockets still would appear to be the idiotic positioning of the glowing bits, nowhere near where a rocket nozzle ought to go in most cases. OTOH, if an impulse engine absolutely requires a vulnerable radiator or tailpipe the size of a truly giant barn door, it makes tactical sense to tuck it between the nacelles somewhere on the stern side of the ship, away from the enemy who'll be off the bow in most cases. The more obscured the location, the better...

Timo Saloniemi

 

[Mister_Atoz]

I'm a little out of my element when it comes to physics. I thought 'Impulse' necessarily implied a Newtonian rocket. However, it seems 'impulse' can imply any sort of drive that applies force to drive the ship forward instead of warping the space around the vessel.

With that in mind, is there a concept for impulse power that would be consistent with what we've seen on screen but doesn't make the impulse engines just a miniature warp drive?

What about a concept that would "warp" the space inside the impulse engines, contracting it so that the drive thrust is ejected at a much greater rate. Could this conceivably allow for some of the speeds we've witnessed? would this do anything at all?

would the "off-axis" glowing bits matter if they were just for radiating waste heat from the ship?

 

[Crazy Eddie]

Well... now you mention it.. the thing at the back of the saucer can't be an exhaust port.. its covered by a grill like those on the nacelles, good point, even more proof that impulse engines are non newtonian.

Heh? The grillework on the impulse engine looks nothing like the warp nacelles. It's a porous grid, in fact it's almost identical to the exhaust vent on the HiPep ion thruster.

Except that there's absolutely nothing exhausted

What about that "fusion reactor exhaust" you mentioned earlier? Or do you want to walk that one back too?

As for the ion engine, definitly a visible trail.

Actually, ion engines don't leave a visible trail, especially in a vacuum.

 

[Crazy Eddie]

The main argument against impulse engines being rockets or vectored rockets still would appear to be the idiotic positioning of the glowing bits, nowhere near where a rocket nozzle ought to go in most cases.

Once again....

Many real space craft do mount their orbital engines significantly off-axis from the center of gravity. Those engines are angled so that they fire through the center of gravity regardless of their position; on the space shuttle, they're even gimballed for fine control.