Good day all. In digging through the forums and the net, it seems that a general consensus is that Impulse Drive is some type of very high energy plasma thruster. Fusion reactors supply plasma to an accelerator coil system that directs the plasma out the back to generate thrust. Has there been any other theories on how impulse works?
Well, the competing one would have to do with the control of inertial mass that our heroes practice with their subspace fields (first explicitly brought up when they move DS9 to the wormhole mouth, but you really have to do magic with inertia whenever you move at sublight in Trek). Power up a miniature warp coil (there's dialogue on "impulse coils", after all) and you control the ship's apparent mass and therefore its Newtonian movement. The powering may optionally involve fusion, which creates waste exhaust, which then may or may not be used for additional thrust much like a propeller-engined aircraft's tailpipe exhaust may or may not contribute to its thrust. ...Perhaps Inertial Mass is what contributes the first two letters to the IMPULSE acronym? It is remarkable IMHO that the intense glow from supposed impulse engine nozzles has nothing to do with their state of motion. Most ships glow all the time; the TOS ship in the remastered episodes glows only when straining to accelerate, but not every time she's under thrust. This would be consistent with these being tailpipes rather than propulsive nozzles, and indeed "tailpipe" is the word used on screen in ST6:TUC, while "nozzle" is not used. This, along with the fact that the tailpipes are incorrectly located if one wants them to serve as Newtonian rocket nozzles (they would just send the ships spinning, or blast straight at the ship's own structures), makes it dubious that the exhaust would directly contribute to propulsion. Further refinement to this model would come from those fancy blue domes sometimes associated with impulse engines. Backstage doubletalk calls them "impulse crystals" and "warp field governors", depending on whom you ask; combining the two, we could say that impulse in those ships is achieved by governing the warp field with this crystal doodad. Ships lacking the dome would achieve impulse with separate internal impulse coils, even if using the warp field would be a fallback option, and using the impulse coils to boost warp another such option. Since Kirk's TOS ship is one of 'em domeless ones, the numerous references of him using impulse to complement warp or vice versa (starting with "Corbomite Maneuver" already) would fall neatly in place... Timo Saloniemi
Since it's slower than light speed, I had assumed it was some high-powered fusion and/or ion drive. Some mechanism of that nature. But I'm not an educated scientist, so that's my layman's general guess.
If it's STL, we know what the upper speed limit is, it's 1.0c. The only thing that really matters is how close to 1c can your vessel get without straining the STL engine systems, and what are you doing to compensate for time dilation that becomes significant past 0.25c? My bet is that Static Warp Bubble that O'Brien rigged up to move DS9 from Bajor to be right next to the Worm Hole is similar to what is needed to exceed the 0.25c barrier and allow faster acceleration close to the limit.
What would really matter is acceleration, yes. Any stupid thruster can do .99 lightspeed if provided with the magic propellantless capabilities of the impulse drive. It may just take millions of years for it to reach that speed. But ťat's how long it would take for the E-nil and E-A, too, judging by their "Spacedock departure at 1/4 impulse" scenes... A trick like the static warp bubble is needed to defeat the rocket equation and to eliminate propellant mass as a factor - without such magic, a rocket cannot fly to the stars or even to the planets as depicted, regardless of the nature of the rocket. It then becomes a question of how much magic we use. Does the magic turn a rocket into an interstellar or interplanetary engine, by, say, shrouding the mass? Or does it replace the rocket altogether, with a "field drive" of some sort? It's only after this that one needs to worry about relativity. And Trek control of inertial mass could intuitively well be the part that outdates Einstein for good. If the control stems from warp/subspace fields, all the better - one doodad makes the whole universe Newtonian as witnessed. If it were even theoretically possible to build an impulse drive that obeys relativity, we'd probably see relativity in action somewhere. And we have to squint hard to see any in Trek. Timo Saloniemi
I remember watching an interview with Mike Okuda (think it was part of a TNG special or something like that), and he was always quizzed on how certain bits of technology worked and he joked about how his reply was: Very well, thank you.
I've always belived that the impulse system worked to reduce the apparent mass of the ship to where a ships thrusters have the power to push the ship where you need to go, and the "exhaust" is its main thruster. Basically it works like how Ds9 was moved, some type of "field" to decrease mass. I say this because a "Fusion Exhaust" to push that ship would have a tail burn hundreds of meters long so called "Torch Ship" and the acceleration wouldn't be that much. So to get from 1/4 speed of light to zero in like 5 seconds wouldn't work, and would be like 5000g's of deceleration.. ahh inertial compensators.. In the Honor Harrington universe, they have a sub light propulsion they call a wedge, and it can do like 500 g's of acelleration, but your still hours of travel, sometimes days in system, and in battle the compensators get hit.. your Raspberry jam against the wall.. Now for impulse speed I think its been said somwere some episode that they limit it to 1/4 light speed to negate realatavistic time slippage, I looked at a graph once, its really only once you get past 0.9 lightspeed where the graph peggs out on time.. Where 1/2 lightspeed is for emergencies like V'ger. faster is possible but requires some re engineering, and accepting the time dilation.. ( Like in Destiny, the Columbias warp drive is fried and no source of help, so they kick up the impulse to .99 but experiance 3 years time dilation to the nearest planet) So its not a "Warp Bubble" in that it incases the ship in its own space/time bubble where realativity won't matter since your not "Technacally" moving but some type of mass canceler to make a low thrust system work, or like the Vulcan shuttle from TMP, it has some type of intertia less engine..
I think reducing mass had a lot to do with the shuttle bay venting being able to move the ship in Cause and Effect, The entire impulse system didn't work, but the reduce mass piece did.
I was assuming the impulse ports were thrust nozzles of some sort but that force fields were used to vector the exhaust to provide a balanced thrust (or some sort of "gyroscopic stabilizing" effect was in play). As to the impulse drives being low powered warp drives that provide sublight speeds, perhaps it's the other way around, a plasma or ion drive that uses warp technology to vastly accelerate the exhaust to near-lightspeed giving a huge amount of thrust for minimal output. (Ultimately of course it's what looks good and what's needed for the plot, isn't it.)
The Making of Star Trek by Roddenberry and Whitfield, page 191, says that the impulse drive is sub-light only. From STAR TREK WRITERS/DIRECTORS GUIDE, THIRD REVISION by Gene Roddenberry (April 17, 1967), page 8: The Enterprise has a secondary propulsion system. These are impulse power engines (same principle as rocket power), located at the rear of the saucer section". Vessel speed, when using the impulse engine is, of course, less than the speed of light. The TNG Tech Manual by Sternback and Okuda, pp. 75-78, says that the impulse drive uses fusion-powered engines to generate thrust, and as of the Ambassador class (Enterprise-C), spacetime driver coils are used to reduce the inertial mass. The Galaxy class did not accelerate the plasma exhaust beyond lightspeed, because it was determined that that did not improve performance. Seems pretty unambiguous and conclusive. The impulse drive is not a kind of warp drive. The impulse drive is basically a high-energy fusion rocket with plasma exhaust, but later starship classes use a mechanism to reduce inertial mass, thereby increasing effective performance of the rocket and allowing the ship to accelerate to higher sub-light speeds much faster than without it. The idea of using shields/force fields to vector the impulse engine exhaust has been discussed in fan circles since at least the 1970s, but I have no source to cite for that. It's noteworthy, though, that that idea would allow the thrust to be vectored in any direction whatsoever without moving the ship.
Yup. The only problem is, it's not true. In the universe of Star Trek, impulse engines don't have rocket exhaust. This would require rocket nozzles; instead, starships have vents that are aimed at bits of the starship itself, or in directions other than aft, and/or are located off the thrust line. Blasting a rocket exhaust out of those could never make the ship move forward. The only way for the ships to be propelled by a rocket exhaust would be if the flame were completely invisible, and the nozzle shooting it out were equally invisible. Why bother to postulate invisible things when there are visible ones being presented to us by this thoroughly visual show? Things might be different if even a tiny bit of those backstage musings made it into actual episode dialogue at some point. This doesn't happen, though: if starships have rockets, they are never equated with the impulse system, and if starships have exhaust flames, these are never discussed. Indeed, when ships or shuttles move at close quarters, being right behind the glowing bits is not a dangerous thing to do at all. Things discussed outside the Star Trek universe are, well, a separate issue. If a background book describes a hero as a dashing young fellah but the fans see a balding wimp, the background book can be excused for its "slight inaccuracies" but the wimp doesn't get any more dashing... (On a related note, the "impulse only goes up to .25c" isn't an onscreen thing. It isn't even a backstage thing. The only place where this figure is mentioned is the TNG Tech Manual, which on another page happily discusses impulse travel in the high .9c range. Since impulse engine commands in onscreen Trek are basically never combined with actual speed readings, we can't readily tell whether our heroes normally fly at .25c or .97c when doing full impulse. Which is for the better...) Timo Saloniemi
Many times on this site, it was shown that Impulse Power/Engines generate Faster Than Light (FTL) speeds in TOS episodes. Analyses are scattered over this site, but the key episodes are WNMHGB, Balance of Terror, and The Doomsday Machine. (Numerous posts associated to Balance of Terror are in The Romulans.) My head canon: Impulse is an alternative drive system that burns fuel reserves and does not involve any space/time warp technology. The fuel is not a rocket propellent, rather it is used as an energy source (in fusion reactors) to generate some unknown force which provides thrust (probably a gravity drive; the ship has artificial gravity and inertial dampening, so, why not a drive system, too?). For the TOS Enterprise, the gravity drive emitters will need to be physically mounted to structural hard points on the saucer. The obvious ship feature puts the main gravity emitters associated to the extended rear housing at the rear of the saucer. These gravity emitters are the impulse engines which provide the forward and reverse propulsion. Another prominent ship feature is the top spine above the impulse drive. The entire spine itself can be another elongated gravity emitter, or a series of smaller emitters along its length, primarily used for maneuvering the ship in a straight line, or up, down, side-to-side, plus rotate and pivot in any direction (e.g. Pitch, Roll and Yaw). The spine feature acts as the ship’s impulse rudder and keel. Additionally, an anti-gravity field around the ship results in a mass elimination effect. With mass elimination, all Einstein and Newtonian physics that involve mass are circumvented, so, no increase in mass with high speed hence no speed limit of c and no time dilation. This field also eliminates the effects of inertia and acceleration inside the field, so, high acceleration maneuvers are possible. I suspect that the field is the ship's inertial dampening system. One more powerful gravity emitter array is present on the TOS E, this is the main deflector which generates a powerful long range, cone of force (reverse gravity) to push all matter away from and around the front of the ship as it moves though space. This effect is comparable to a bow wake. Together, mass elimination and directional gravity thrust, you have the impulse drive. The strength of the drive is directly related to the energy levels supplied from the different power systems, i.e. main power (M/AM reactors or “warp” power), auxiliary power (fusion reactors or “impulse” power) and emergency power (capacitor banks or batteries). Regardless of the power source, the top speed of the system is somehow limited by the gravity force used for thrust (speed of gravity?) which in TOS is about 5 to 10 c or equivalent to about Warp 1.8 to Warp 2.
No flames if you are ejecting ions or He atoms. Bigger problem,without reducing the inertial mass to nearly zero, is the amount of energy needed to move a starship to .25c versus the amount of Deuterium on board.
Exactly. Incorporating a subspace driver coil into 24th century Impulse Engines is a nifty idea, but the notion that ships prior to that didn't use any form of mass reduction is absurd from a fuel use perspective! Fortunately, all starships come equipped with one or more nacelles which with all their subspace manipulation capabilities should be more than capable of lowering the vessel's mass at STL speeds. I like that! Nicking it
Argued? Certainly. Shown? With at best variable results. Since intent was so clear from the very beginning, what these episodes show is that the writers didn't follow the premise they established carefully enough for the fans not to find fault with what they were doing. Translation: the fans understood the premise better after the fact than the writers did when constructing the episodes, at least on the technical side of things. (That doesn't mean that fans could write better episodes.) Impulse is just case #47 / 1,771,561 when Star Trek physics are unfaithful to real world physics. And even then, the episodes aren't as conclusive as some fans think. Examples: in WNMHGB, there's no reason for the Valiant to have anything more than sublight drive, since it got to the galaxy's edge after getting swept up in a magnetic space storm. The storm itself could have provided some sci-fi effect to carry the Valiant at FTL to the barrier. Similarly, the Enterprise entered the barrier at warp, and the barrier could have ejected the ship and flung it back into the galaxy at FTL, so that when it finally coasted back to sublight it was close enough to limp to Delta Vega at sublight. Various proposals have been floated about how to square BoT, including the idea that while their cloaking device is running, the Bird of Prey has to stay sublight, but with cloaking off they can travel at warp. Etc.
And James Blish (in one of his Star Trek books) compared the impulse engine to "a giant blow torch." But unless such descriptions make their way on screen or into dialog they're meaningless. It's what's on screen and in the actors dialog that counts. "The writer's intent," while possibly interesting, simply doesn't matter. Apparently not even the malnuvering thrusters were what could be called "rockets." The impulse engines were a sci-fi techno-babble fictional propulsion system. In the episode where Ensign Ro makes her last showing, it is said that the impulse engines are in fact venting something and the ship's shields had to take this into account. Or Ro was making stuff up for the guy sitting next to her (been a while since I saw the episode).