Star Destroyer Fast Deceleration in TESB
Posted: Mon Feb 12, 2007 7:24 am
Hot damn.
This page on the Falcon's acceleration abilities points to the Falcon having acceleration measured in the tens of g.
However, I think I've found something that totally breaks that wide open.
This new part of the weapon range page shows that the two-second shot of the ISDs "comin' right at us" shows that they close by about 60 kilometers in those two seconds, for an average velocity of 30km/sec . . . which sure seems hella-fast for them, but whatever. It was weird enough for me to point out on the page when I was making it.
I was then working on my Imperial power generation page, wherein at one point I needed an estimate of Star Destroyer acceleration ability in open space. My other example was totally ballparked, so I decided to see what I got by taking the 30km/sec, counting how many seconds it took for the pair of ISDs and the Falcon/Avenger pair to get close for the dive scene, and then see how fast the pairs were going relative to each other. This would, theoretically, give me a deceleration rate for the ISDs.
After the out-the-window shot from the Falcon cuts to an interior view, it's about ten seconds until the scene when the two Star Destroyers are visible as the Falcon dives away, with Avenger right behind. The vessels at that point are moving at a relative velocity of perhaps a hundred meters per second, or effectively zero compared to the earlier relative velocity of both pairs.
There is no way to know how much forward velocity any of the parties shed on their way to close encounter (and, in the case of at least two of the ISDs, a minor collision). At maximum, one or the other pair of ships dropped from 30km/sec to near-zero. Alternately, both were at about 15km/sec and came to nearly a relative stop. This range would imply an ISD deceleration of between 1500m/s² and 3000m/s².
That said, a vessel at 15km/sec stopping in ten seconds with a deceleration of 1500m/s² would require a distance of 75 kilometers, which happens to be in good agreement with the vessel distance at the end of the scene of the Star Destroyers out the Falcon's window. A vessel at 30km/sec stopping in 10 seconds with a deceleration of 3000m/s² would require 150 kilometers, meaning the vessels would still be moving quickly as they passed. Thus for one of the pairs to be moving at 30km/sec with the other more or less stationary would require that the decelerating pair decelerate at some 6000m/s².
So the maximum value here is 6000m/s², or 611g. The low end is 153g.
Obviously, that's a helluva lot more than the 210m/s² (21.5g) I found for the Falcon previously.
Reviewing the script and novelization doesn't seem to suggest that there is more time that we don't see, so the ten second value seems solid. And the ships were definitely moving at a relative average velocity of 30km/sec in those two seconds. Even assuming that they were already decelerating (thereby giving us 12 seconds) doesn't really change the final value. (You can try it yourself with the cheat-sheet calculator here.
The way I see it, applying the Falcon acceleration from that scene as a maximum was wrong in one or more of the following ways:
1. Despite the afterburner, the Falcon was not, in fact, accelerating to maximum ability.
2. The Falcon is not the most "accelerative" ship at sublight (implied by the novelization description of the "coming right at us" scene's text)
3. The ISD in the afterburner scene decelerated/reversed, driving up the Falcon's true acceleration.
4. The camera was not even close to stationary, which is required for most of the Falcon calcs.
Or:
5. There's something wrong with my analysis of the "comin' right at us" scene.
#1 seems invalid on an instinctual level. It doesn't make sense in light of the rest of the films.
Personally, I don't think #2 is valid. Han insists that Lando take the Falcon to Endor because she's the fastest . . . this would not logically have squat to do with hyperspace speed because the whole fleet was supposed to arrive at the same time in hyperspace. To be sure, the Falcon kept getting caught by Star Destroyers in the films, but in most cases this is readily explained by ISDs getting a head start as the Falcon achieves orbit while a Star Destroyer is already at orbital speed.
#3 and #4 are entirely possible, though there's no real indication of #3.
And really, I don't see how #5 is possible.
But, I wanted other opinions. Thoughts?
This page on the Falcon's acceleration abilities points to the Falcon having acceleration measured in the tens of g.
However, I think I've found something that totally breaks that wide open.
This new part of the weapon range page shows that the two-second shot of the ISDs "comin' right at us" shows that they close by about 60 kilometers in those two seconds, for an average velocity of 30km/sec . . . which sure seems hella-fast for them, but whatever. It was weird enough for me to point out on the page when I was making it.
I was then working on my Imperial power generation page, wherein at one point I needed an estimate of Star Destroyer acceleration ability in open space. My other example was totally ballparked, so I decided to see what I got by taking the 30km/sec, counting how many seconds it took for the pair of ISDs and the Falcon/Avenger pair to get close for the dive scene, and then see how fast the pairs were going relative to each other. This would, theoretically, give me a deceleration rate for the ISDs.
After the out-the-window shot from the Falcon cuts to an interior view, it's about ten seconds until the scene when the two Star Destroyers are visible as the Falcon dives away, with Avenger right behind. The vessels at that point are moving at a relative velocity of perhaps a hundred meters per second, or effectively zero compared to the earlier relative velocity of both pairs.
There is no way to know how much forward velocity any of the parties shed on their way to close encounter (and, in the case of at least two of the ISDs, a minor collision). At maximum, one or the other pair of ships dropped from 30km/sec to near-zero. Alternately, both were at about 15km/sec and came to nearly a relative stop. This range would imply an ISD deceleration of between 1500m/s² and 3000m/s².
That said, a vessel at 15km/sec stopping in ten seconds with a deceleration of 1500m/s² would require a distance of 75 kilometers, which happens to be in good agreement with the vessel distance at the end of the scene of the Star Destroyers out the Falcon's window. A vessel at 30km/sec stopping in 10 seconds with a deceleration of 3000m/s² would require 150 kilometers, meaning the vessels would still be moving quickly as they passed. Thus for one of the pairs to be moving at 30km/sec with the other more or less stationary would require that the decelerating pair decelerate at some 6000m/s².
So the maximum value here is 6000m/s², or 611g. The low end is 153g.
Obviously, that's a helluva lot more than the 210m/s² (21.5g) I found for the Falcon previously.
Reviewing the script and novelization doesn't seem to suggest that there is more time that we don't see, so the ten second value seems solid. And the ships were definitely moving at a relative average velocity of 30km/sec in those two seconds. Even assuming that they were already decelerating (thereby giving us 12 seconds) doesn't really change the final value. (You can try it yourself with the cheat-sheet calculator here.
The way I see it, applying the Falcon acceleration from that scene as a maximum was wrong in one or more of the following ways:
1. Despite the afterburner, the Falcon was not, in fact, accelerating to maximum ability.
2. The Falcon is not the most "accelerative" ship at sublight (implied by the novelization description of the "coming right at us" scene's text)
3. The ISD in the afterburner scene decelerated/reversed, driving up the Falcon's true acceleration.
4. The camera was not even close to stationary, which is required for most of the Falcon calcs.
Or:
5. There's something wrong with my analysis of the "comin' right at us" scene.
#1 seems invalid on an instinctual level. It doesn't make sense in light of the rest of the films.
Personally, I don't think #2 is valid. Han insists that Lando take the Falcon to Endor because she's the fastest . . . this would not logically have squat to do with hyperspace speed because the whole fleet was supposed to arrive at the same time in hyperspace. To be sure, the Falcon kept getting caught by Star Destroyers in the films, but in most cases this is readily explained by ISDs getting a head start as the Falcon achieves orbit while a Star Destroyer is already at orbital speed.
#3 and #4 are entirely possible, though there's no real indication of #3.
And really, I don't see how #5 is possible.
But, I wanted other opinions. Thoughts?