Just how fast is impulse?
- Thread starter cwl
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I've seen anywhere from 1/3 - 3/4 the speed of light.
This is a good reference: http://memory-alpha.org/en/wiki/Impulse_drive
Along with any canon tech manual.
This is a good reference: http://memory-alpha.org/en/wiki/Impulse_drive
Along with any canon tech manual.
Slow, unless the fuel is contained at a density similar to a neutron star.
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).
Old Warp Factor Scale put full impulse at 269,824,250 kph.
I don't know what it is on TNG, sorry!
James
I don't know what it is on TNG, sorry!
James
I could be mixing my "real" theoretical FTL concepts with my Star Trek FTL but warp drive doesn't take place in subspace, does it? As far as the Alcubierre concept of warp drive, it's just a matter of stretching/compressing normal space. While subspace is very cool and yields all kinds of other sweet technologies like subspace radio, I don't think that's related to subspace.
What freaked me out my first semester of linear algebra is how often the term "subspace" is used in any topological math class!
Back to the point though... I've always wondered how they don't run into massive relativistic problems with something like impulse. You start to see time dilation around .3c and above .5c, there's been that recent paper about "negative gravity" effects based on the new solutions to the relativistic form of the general field equations...
Another thing I've never been comfortable with (hope this isn't too off point) is the way that in some episodes or movies (First Contact does this and TOS did quite a bit) the way they 'accelerate' up to warp 1 in a totally Newtonian sense of the idea of acceleration. Makes no sense at all. There should be no motion involved in going to warp, but I guess they can make it up however they want... claim you need some speed to maintain a stable warp field or something.
But the relativistic effects of a starship entering and exiting warp in this way, under high impulse, would really start to accumulate into time differences. Ship's clocks would have to resynchronize every time they returned to Earth, and short of a galaxy-wide time broadcasting network (lol, like a 24th century NTP server!) there'd be no way to keep universal time. Really screws with the logistics of running a Federation.
I explained away their being at impulse because they were doing some sort of analysis (Valtane did had Sulu a PADD) and they talked about mapping the entire sector. Maybe they were on their way home at impulse and were going to go to warp once the scans were done.
Toward the middle of Voyager I think they established the .25 as the maximum impulse speed.
Toward the middle of Voyager I think they established the .25 as the maximum impulse speed.
To reach the speeds people want/are stated, you need some kind of non-relativistic drive. Accelerating an object from rest to .5c demands billions of tons of fused hydrogen--even without calculating the increase in mass of the object from the approach to lightspeed, even without calculating the truly shocking fuel expenditures from moving the fuel itself. It can be fusion driving the engine, that's fine--Cochrane's flight shows that fusion or even electric batteries can run a Warp 1 field, unless one chooses to believe in the psychotic notion that Cochrane obtained quantities of antimatter in post-atomic horror America--but if you want high sublight speeds you absolutely need some kind of technology that is essentially low warp. So why bother with the fusion drive at all if your M/A annihilator drive is available?
I'm pretty sure I've seen this figure somewhere else. One of the old Star Trek Encyclopedia's? Think it was one before the end of Deep Space Nine and definitely before the end of Voyager, if that helps to date it.
It's a mistake to think of powered motion through space in terms of a fixed speed. Remember, in space there's negligible friction. Driving on the ground or flying through the air, you have friction slowing you down so you need to have forward thrust to cancel that out and maintain a steady velocity. In vacuum, that doesn't happen. You maintain a steady velocity just by coasting. If you apply thrust, you accelerate continuously. And there is no speed limit in space short of the speed of light, or rather the speed at which the negligible friction of the interstellar medium becomes great enough to cancel out your thrust, which is probably going to be over 95% of lightspeed anyway.
So speaking of the speed of impulse drive is a contradiction in terms. As long as the impulse drive is activated, a ship's speed is constantly increasing (or decreasing if it's reverse impulse). The way to talk about propulsion in space is in terms of acceleration, how quickly your speed increases. And that's a function of power. Maximum impulse doesn't refer to a speed limit, but to a thrust limit, the hardest acceleration you can manage.
There's a common misconception in fandom that "full impulse" equals a quarter of lightspeed, but that's based on a misreading of the TNG Tech Manual. What it actually says is that .25c is the preferred maximum speed for normal operations, in order to avoid relativistic effects. Generally if you need to cover a distance too great for a quarter lightspeed to be practical, it's simpler just to use warp drive. It's analogous to a posted speed limit -- it's not the fastest your car is capable of going, just the fastest it's recommended or safe to go in normal circumstances. There's nothing preventing any impulse engine from accelerating to nearly lightspeed, as long as it has enough fuel, enough power, and enough time.
So speaking of the speed of impulse drive is a contradiction in terms. As long as the impulse drive is activated, a ship's speed is constantly increasing (or decreasing if it's reverse impulse). The way to talk about propulsion in space is in terms of acceleration, how quickly your speed increases. And that's a function of power. Maximum impulse doesn't refer to a speed limit, but to a thrust limit, the hardest acceleration you can manage.
There's a common misconception in fandom that "full impulse" equals a quarter of lightspeed, but that's based on a misreading of the TNG Tech Manual. What it actually says is that .25c is the preferred maximum speed for normal operations, in order to avoid relativistic effects. Generally if you need to cover a distance too great for a quarter lightspeed to be practical, it's simpler just to use warp drive. It's analogous to a posted speed limit -- it's not the fastest your car is capable of going, just the fastest it's recommended or safe to go in normal circumstances. There's nothing preventing any impulse engine from accelerating to nearly lightspeed, as long as it has enough fuel, enough power, and enough time.
besides at .5c it would take 9 years to get from Earth to Alpha Centauri. not exactly 'warp speed' now is it?
Because "warp" doesn't mean "fast," it means "distortion," specifically the distortion of spacetime geometry to achieve effective superluminal travel. You wouldn't refer to propeller-driven flight as "low rocket," because it's a totally different method from rocket propulsion.
That's certainly what it sounds like. The fact that they are going home is fresh news indeed: Sulu has probably not even given the order to head home when we hear his log, because Valtane has not yet told him that they can go home. Remember that oftentimes, Captain's Logs sound as if they were dictated some time after the events, as added-on narration on an automated recording on events that at the time didn't appear logworthy yet. In ST6, Sulu would do well to afterwards add a narration of "See, here we're starting to head home, and soon the Praxis Explosion will happen but we don't know it yet - just wait for it, the good part's about to start", even if he adds it slightly too early for it to make complete logical sense.
Impulse is given as "half" or "full" or "1/4" or so forth, so it's probably a throttle setting. At full throttle, at first you go very slowly, but after a while you go very fast. At 1/4 throttle, at first you go very slowly, but after a while you go very fast. It's just a question of how long you want to wait for "very fast".
Oh, at some point, a limiting factor might cut in, so 1/4 throttle wouldn't get you past a "strong headwind" or "subspace drag" or whatever while full throttle would. And full throttle could run into a limiter, too, such as "more subspace drag". But perhaps not before the ship was going at something like .999999999999 lightspeed, and crossing galaxies in a matter of (subjective) seconds.
Timo Saloniemi
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.
Truly rediculous.
Truly rediculous.
In vacuum there is no classical retarding force, but there is enough gas, dust and other interstellar matter to retard spacecraft motion at relativistic speeds,
Althought not canonical, I think of full impulse as getting up to 1/4 c.
Althought not canonical, I think of full impulse as getting up to 1/4 c.
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.
Since impulse engines appear to work as a kind of fusion-powered thruster boosted by driver coils, theoretically "impulse power" is a unit of output, not speed. When the captain orders "one quarter impulse" he's not calling for a speed, he's calling for an engine gear level that determines how much thrust the engines will generate and how quickly the ship will respond. Similar to a submarine where, for example, a commander may order the ship to dive to 500 feet, but depending on how fast he needs to get there he can quote any angle from 5 to 30 degrees (and newer submarines can actually dodge torpedoes by making very rapid ascents at high speeds, from deep water to shallow water in a matter of seconds).
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.
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.
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."
Given the constraints of a starship's dimensions, you can either have an object able to accelerate to high sublight speeds in any reference frame, or you can have a basically Newtonian drive--you cannot have both.
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