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Go Back   The Trek BBS > Star Trek TV Series > Deep Space Nine

Deep Space Nine What We Left Behind, we will always have here.

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Old October 23 2008, 01:52 AM   #1
Photon
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Location: Dixie
Full impulse

How fast is impulse compared to warp or thrusters?

For some lame reason I always assumed full impulse was 1/10 of warp 1

If ships star drives differ, lets just use the E-E or Defiant as examples
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Old October 23 2008, 03:22 AM   #2
Dyabolikal
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Re: Full impulse

I believe the TNG technical manual states it's 0.25 of Warp 1 (which is the speed of light, or 1c). I don't own the manual however.
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Old October 23 2008, 04:33 AM   #3
FalTorPan
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Re: Full impulse

I don't see why "full impulse" needs to be the same for all impulse-driven ships. Some ships are bound to have higher slower-than-light maximum speeds than other ships.
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Old October 23 2008, 04:35 AM   #4
msbae
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Re: Full impulse

Dyabolikal wrote: View Post
I believe the TNG technical manual states it's 0.25 of Warp 1 (which is the speed of light, or 1c). I don't own the manual however.
0.23c
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Old October 23 2008, 05:11 AM   #5
FalTorPan
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Re: Full impulse

Nah. 0.250000001c.
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Old October 23 2008, 05:20 AM   #6
SoM
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Re: Full impulse

FalTorPan wrote: View Post
I don't see why "full impulse" needs to be the same for all impulse-driven ships. Some ships are bound to have higher slower-than-light maximum speeds than other ships.
Well, quite. Not all engines are the same, and ships certainly have different masses.
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Old October 23 2008, 06:27 AM   #7
Inquisitive
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Re: Full impulse

This is something I have thought about as well. I cannot recall, but how do ships move about withing a star system? Do they warp from planet to planet, or travel at impulse? If they are warping from planet to planet, then you can assume that impulse speed must be relatively slow, and not very useful for traveling any great distance. In this case, Impulse Drives could be viewed as both a back-up (very limited) to Warp Drive, and as short range maneuvering thrusters for docking and such. Otherwise, we can assume that traveling at Warp is "expensive", meaning that traveling between planets would be easier done with an Impulse Drive, rather than wasting Dilithium or whatever to travel a relatively short distance. If this was the case, Impulse Drives would be capable of something like 25/50/75 percent of c, allowing travel from one end of a solar system to other within a day.
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Old October 23 2008, 08:36 AM   #8
Timo
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Re: Full impulse

In DS9, the runabouts always travel to and from Bajor at impulse, the trip taking anything from two to six hours. They don't warp even in emergencies.

OTOH, the Defiant unhesitantly goes to warp immediately after releasing docking clamps in many episodes.

Make of this what you wish. I like to believe in "subspace weather" that is especially bad near Bajor, and in most days makes it too rough for tiny boats to go to warp there. It's easier to warp outwards from the star, or to warp with a bigger and steadier ship. And some other stars may have calmer weather, so that warping in and out of there is easier. (Earth seems like a stormy place, given that the E-D slowed down to impulse there even in an armageddon-level emergency, in "Best of Both Worlds"!)

Impulse speed as such is indeed relatively slow for interplanetary travel, as lamented by Scotty in "Elaan of Troyius" - but still fantastically fast by today's standards. The guesstimate of one day to cross a star system sounds about right.

However, I'd like to insist that not only is "maximum impulse" dependent on the type of ship and engine in question, it's also not a speed at all. Rather, it's a throttle setting.

If you accelerate at 1/4 impulse, or 1/16 impulse, you eventually reach the very same speed as if you accelerated at full impulse. It just takes longer if you use the lower setting, or have a less powerful engine, or a heavier ship.

This essentially means that we can safely ignore all onscreen references to definite impulse settings: all travel times associated with such settings are always correct, because there are too many hidden variables there for us to be able to cry foul.

And we need those hidden variables. Otherwise, Trek would be too full of contradictions on the impulse setting vs. speed issue.

Timo Saloniemi
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Old October 23 2008, 10:08 PM   #9
dave_R_treker
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Re: Full impulse

If your traveling at full impulse your going the same speed whether you are a shutle craft or a galaxy class ship. Full impulse is 1/4 the speed of light.

If your traveling 55 miles per hour its the same if your on a motorcycle, a car, or even a large truck. it may take longer to reach the speed, but the actuall speed is the same regardless.
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Old October 23 2008, 11:07 PM   #10
SoM
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Re: Full impulse

Inquisitive wrote: View Post
This is something I have thought about as well. I cannot recall, but how do ships move about withing a star system? Do they warp from planet to planet, or travel at impulse?
They don't generally warp into a system (Jadzia was shocked when Kira ordered her to warp the Defiant toward the Bajoran sun to catch the Bashir changeling in time). Sometimes, if they have a clear path, they warp out of a system though.

dave_R_treker wrote: View Post
If your traveling at full impulse your going the same speed whether you are a shutle craft or a galaxy class ship. Full impulse is 1/4 the speed of light.

If your traveling 55 miles per hour its the same if your on a motorcycle, a car, or even a large truck. it may take longer to reach the speed, but the actuall speed is the same regardless.
If it makes any sense, "full impulse" is "press the impulse accelerator (gas pedal) to the floor". Unless you have a top speed of 55mph, you're going to keep accelerating past that until you start to level off. And where you level off is dependent on mass, fuel reserves and engine power.
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Old October 24 2008, 10:36 AM   #11
Timo
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Re: Full impulse

It should also be noted that in chase scenes, "warp 5" is a universal measure of speed: our heroes and villains can both declare "we are traveling at warp 5", which then means that neither is gaining or falling back. The speed a certain warp factor corresponds to is not dependent on the ship, its engines, or its history of acceleration, then.

In contrast, there is no such universality about the command "full impulse" or "1/4 impulse" in the dialogue of any episode or movie. One ship's full impulse may well be insufficient in catching up with another ship's one-quarter. And the engines may be set at 1/4 impulse and still only move the ship at crawling speed initially, as we see several times when Kirk's ship leaves the spacedock in the TOS movies.

Nor is there any indication that the speeds reached by impulse engines would really be limited to 0.25 c. This is just a Starfleet recommendation that is mentioned in the Tech Manual, not something that would limit all heroes and villains on screen. For all we know, our heroes regularly do something like 0.75 c at impulse. That is, after they have accelerated to that speed, which may take hours or days of running at full impulse.

Timo Saloniemi
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Old October 24 2008, 01:05 PM   #12
FalTorPan
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Re: Full impulse

Timo wrote: View Post
It should also be noted that in chase scenes, "warp 5" is a universal measure of speed: our heroes and villains can both declare "we are traveling at warp 5", which then means that neither is gaining or falling back. The speed a certain warp factor corresponds to is not dependent on the ship, its engines, or its history of acceleration, then.

In contrast, there is no such universality about the command "full impulse" or "1/4 impulse" in the dialogue of any episode or movie. One ship's full impulse may well be insufficient in catching up with another ship's one-quarter. And the engines may be set at 1/4 impulse and still only move the ship at crawling speed initially, as we see several times when Kirk's ship leaves the spacedock in the TOS movies.

Nor is there any indication that the speeds reached by impulse engines would really be limited to 0.25 c. This is just a Starfleet recommendation that is mentioned in the Tech Manual, not something that would limit all heroes and villains on screen. For all we know, our heroes regularly do something like 0.75 c at impulse. That is, after they have accelerated to that speed, which may take hours or days of running at full impulse.

Timo Saloniemi
Agreed on all counts.

As for the Tech Manual suggesting that staying below 0.25c effectively avoids the inconvenience of relativistic time dilation... I don't buy it. Warp drive, the transporter (which, if you buy into references from TNG, does not utilize subspace), and subspace communications already completely ignore relativity. Why should impulse drive be any different?
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Old October 8 2011, 03:39 PM   #13
Wade
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Re: Full impulse

In TNG episode "Suspicions" Jobril states that he is one million km from the corona of the star and will arrive in 3 minutes at 3/4 impulse.

Here is what I've worked out:

Shuttle can travel 1,000,000 km in three minute at 3/4 impulse.

(This takes no hypothetical acceleration curves in to account and assumes a constant speed.)

This means that the shuttle can travel 20 million km in one hour

20,000,000 km = 12,427,423.845 miles

1/4 impluse = 4,142,474.615 mph

Full impulse = 16,569,898.46 mph

Speed of light is 670,616,628 mph

Full impulse = 0.0247084515476702 of the speed of light
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Old October 8 2011, 07:12 PM   #14
defiantfan
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Re: Full impulse

Timo wrote: View Post
In DS9, the runabouts always travel to and from Bajor at impulse, the trip taking anything from two to six hours. They don't warp even in emergencies.
I'm confused because I thought that the main difference between runabouts and shuttlecrafts was that runabouts can warp am I wrong about that?
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Old October 8 2011, 07:22 PM   #15
Ln X
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Re: Full impulse

defiantfan wrote: View Post
Timo wrote: View Post
In DS9, the runabouts always travel to and from Bajor at impulse, the trip taking anything from two to six hours. They don't warp even in emergencies.
I'm confused because I thought that the main difference between runabouts and shuttlecrafts was that runabouts can warp am I wrong about that?
Yeah runabouts can go to warp, but it's Starfleet protocol (or sound advise) not to travel inside a star system at warp. So yes the runabouts could go to warp to reach Bajor, but regulation or something means they go at impulse.
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