Criticism against Wongs 72.000G calculation

[His Divine Shadow]

Found this on SB, since it's a direct criticism against Wong's calcs I think it's only fair he be notified:

And once more comes the 'thousands of G's' claim. The Proton Luke fired was moving SLOW AS ALL HELL when it made its turn into the exhaust port! The calcs for a 75,000 G turn IIRC are bassed on the assumption of a speed of 1 klick per second for the torpedo. AT 1 klick per second every second its covering 1000 meters. The final screen where we see the torpedo as it makes its final dive into the Death Star. Using the exhaust port (2 meters wide) as a refrence, we can calculate the total distance travaled to be around 10 meters, upper limit. Now it took roughly 4 frames for each torpedo to move from the edge of the screen and reach the exhaust port and start to dive into it. At 25 frames per second that works out roughly to be 70 meters per second....not 1000.

Not to mention the torpedoes didn't reach the port and instanly in one frame do a snap 90 degree course change. They took 3-4 frames to curve from the side in a diving turn, they didn't just arive directly over the top ofthe port and make a 90 degree course change without a problem.

[Chris OFarrell]

Hey cool, Mike himself made these calcs :p I thought it was Poe (Oh well no flame war with him......this time.....)

Realy when you get down to it, my main problem is that Mike did not calculate the speed of the torpedoes but picked a totaly arbitrary number (1 klick per second) and applied that to get the 72,000 G number which has been branded about as a 'proven figure' by a heck of a lot of people. However even the most basic scaling of the sceen from the stated 2 meter exhaust port will show that at the time it took for the torpedoes to cross the distance shown, they could not have been moving any faster then 100 meters per second, not the 1000 meters per second used.

I'll admit my numbers are VERY rough, but I'd expect them to be reletivly accurate.

[SPOOFE]

Chris, you ever consider that the 72,000 G calc also refers to the deceleration the torpedoes would've naturally made in order to make that turn easier?

[Chris OFarrell]

Chris, you ever consider that the 72,000 G calc also refers to the deceleration the torpedoes would've naturally made in order to make that turn easier?

Not realy. The calcs as far as I knew never claimed to show that, only to show the torpedoes made a 72,000 G turn to enter the port. Which is the context I have always heard of them in.

And on the idea of that, exactly what WOULD we be using for an initial velocity of the X-Wing to calculate any 'torpedo slowdown'? THe entire sequence is FUBAR beyond Voyager. YOu have tarkins countdown saying one thing, the timer of the VCR another, Lukes rangefinder saying another. I mean the Trench is only supposed to be 50 klicks long right? It took them a hell of a lot longer then 50 seconds to cover the distance from start to finish IIRC.............

[His Divine Shadow]

Have you tried only measuring the time in which we see the trench?

And wasn't it a longer bit than 50km they had to travel?

[Darth Wong]

Are they seriously suggesting that the protorp arrived at the port with a miniscule fraction of its launch speed? That it knew where the port was and decelerated preparatory to the turn? How did Luke's fighter not overtake the torp if it slows down so much, and why does it accelerate away from his fighter when it's launched? Slow-mo may be an undesirable rationalization, but at least it works better than arguing that the protorp accelerated away and then slowed down, and that Luke slowed down with it.

[Vympel]

One thing I always wanted to know was that since Luke turned off his targeting computer ... how did the torpedoes even make the turn? Wouldn't they have just gone straight?

[Andras]

Maybe all the torpedos were programmed to make the turn when they lifted off Yavin, The computer was only to make sure the fighter was pointing the torpedos at the correct angle to go in, ie to hit the right launch point.

Not only that, but the torpedo had to be cooking right along to hit the center of the DS in about 5 seconds or less ( time from launch to explosion, assuming an instantaneous chain reaction.) I have the timeline at home, but not here.

[Alyeska]

Maybe all the torpedos were programmed to make the turn when they lifted off Yavin, The computer was only to make sure the fighter was pointing the torpedos at the correct angle to go in, ie to hit the right launch point.

Not only that, but the torpedo had to be cooking right along to hit the center of the DS in about 5 seconds or less ( time from launch to explosion, assuming an instantaneous chain reaction.) I have the timeline at home, but not here.

I rather think there was a bit of a time dialation in there. Look how long it took them to approach the DS. Why would they be running away so much faster when a quick approach is the most important thing?

[Darth Wong]

I rather think there was a bit of a time dialation in there. Look how long it took them to approach the DS. Why would they be running away so much faster when a quick approach is the most important thing?

They had to slow down to get through the shield.

[Evil Sadistic Bastard]

One thing I always wanted to know was that since Luke turned off his targeting computer ... how did the torpedoes even make the turn? Wouldn't they have just gone straight?

Well, maybe Luke was subconciously using the Force to guide the torps. I mean, even Wedge, an ace pilot missed them, and yet Luke, the rank amateur, blows up a Death Star with two micro nukes.

Meanwhile, this is completely unrelated to the topic. I shall now flagellate myself for my impudence.

[Darth Servo]

Can we get a pic of the exhaust port? Based on the visuals, it seems to be significantly smaller than two meters. Assuming when we actually see the thing but I could be mistaken.
The port appears to be less than 3x the width of the torp.
http://www.theforce.net/swtc/Pix/cards/wide/anhtorp.jpg
The x-wing launch tubes are clearly smaller than a person's head.
http://www.theforce.net/swtc/Pix/Xbrooklyn/Xwing2.jpg

So the two meter figure actually exaggerates the size of the port and therefore the 72,000g figure is actually conservative.

[CmdrWilkens]

What might need to be done is to check the torpedo velocity when they are in the trench running free, after they leave Luke's fighter but before making the turn. Admittedly there aren't any real good references but even figuring how fast the camera is moving along the rench (and how fast the torps are moving relative to the camera) ought to give us an idea.

[Asst. Asst. Lt. Cmdr. Smi]

I don't think Luke used the Force to guide the torps in, yet tell the exact time to fire, for a direct hit.

[Grand Admiral Thrawn]

One thing I always wanted to know was that since Luke turned off his targeting computer ... how did the torpedoes even make the turn? Wouldn't they have just gone straight?

Well, maybe Luke was subconciously using the Force to guide the torps. I mean, even Wedge, an ace pilot missed them, and yet Luke, the rank amateur, blows up a Death Star with two micro nukes.

Meanwhile, this is completely unrelated to the topic. I shall now flagellate myself for my impudence.

Red Leader missed.

[Darth Yoshi]

Do we know the width or depth of the trench? If that's the case, then you can check the camera speed by scaling protrusions along the trench on a frame by frame basis.

[consequences]

We can scale the dimensions of the trench from the size of a x-wing, or we could probably get the statistics needed from the Technical Commentaries,

[Slartibartfast]

It doesn't make the sense that the torpedoes would have required the Force to get in the exhaust. Otherwise, they would have only sent Jedi to do the job

Even with only the targeting computer, there must have been at least a chance of success. Granted, with the Force guiding Luke's AIM, the odds were much greater.

I agree with the slow-motion. There's no way that the filmmakers would have you watch: "look, there's the torpedo... no sorry, it's gone, you missed it. it was only one frame long."

[Connor MacLeod]

According to analysis of the targeting computer display readout when moving down the trench, the X-wings were moving at least at 1 km/s, but no more than 3 km/s (probably more like 2.5 or 2 km/s). This is presumably what Mike is basing his calcs off of. I dont think the visuals contradict this except for the one example where the torp actually goes down the shaft.

As for luke using hte Force - its not neccesary for the scene. Remember that the pilots were only required to target/hit the "exhaust port" (probably because jamming prevented the missile from finding it itself from any reasonable distance.) Once the missile is close to the port (as we saw) - it could easily lock onto the port/reactor (or its emissions or silhouette or whatever they use to target it) itself, and/or use preprogrammed manuvers to turn and hit the shaft.

[Illuminatus Primus]

It doesn't make the sense that the torpedoes would have required the Force to get in the exhaust. Otherwise, they would have only sent Jedi to do the job

Even with only the targeting computer, there must have been at least a chance of success. Granted, with the Force guiding Luke's AIM, the odds were much greater.

I agree with the slow-motion. There's no way that the filmmakers would have you watch: "look, there's the torpedo... no sorry, it's gone, you missed it. it was only one frame long."

The targeting computers wouldn't work because the Empire added heavy-duty jammers capable of fucking up even fighters even at that range after the plans were compressed and stolen by the Rebels. (Source: Essential Guide to Weapons and Technology)

[CmdrWilkens]

According to analysis of the targeting computer display readout when moving down the trench, the X-wings were moving at least at 1 km/s, but no more than 3 km/s (probably more like 2.5 or 2 km/s). This is presumably what Mike is basing his calcs off of. I dont think the visuals contradict this except for the one example where the torp actually goes down the shaft.

As for luke using hte Force - its not neccesary for the scene. Remember that the pilots were only required to target/hit the "exhaust port" (probably because jamming prevented the missile from finding it itself from any reasonable distance.) Once the missile is close to the port (as we saw) - it could easily lock onto the port/reactor (or its emissions or silhouette or whatever they use to target it) itself, and/or use preprogrammed manuvers to turn and hit the shaft.

My bet is that the Torps were set to turn at a given distance and at a given velocity, one where the CEP would be less than about 1m. However that distance and velocity would be based off of a known start point and launching a fraction early or late would cause a mishit thus I think Luke's "Force power" here is simply getting the timing so perfect.

[Andras]

Here's the timing of various events related to the final run in the DS trench.

timing of various events from SW ANH SE videotape
At Alderaan
Commence Primary Ignition 1:11:46
Fires the beams 1.12.01
15 seconds from CPI to firing at "real"time

At Yavin
3 minute warning @ 2.04.12
1 minute warning @ 2.06.20
the final run by X-Wings begins 2.06.39
30 second warning @ 2.08.05
clear to fire @ 2.09.10 -
Commence Primary ignition 2.09.20
Torps enter the port- 2.09.55
Explosion 2.10.05

up to the 1 minute warning, the movie could be said to be running in "real" time, that is no time distortion. after that though things slow down,
from 1 minute to 30 second warnings- 75 seconds
from 30 second to clear- to- fire warnings- 55 seconds
the entire Firing process takes 45 seconds, 3 times longer then at Alderaan
the last X-Wing run lasts 3.26 and they started 19 seconds after the 1 minute warning

the true time from the 1 minute to firing warning to the destruction of Yavin 4 should have been 1 minute plus 10 seconds to order the shot plus 15 seconds to fire the superlaser or 1m25s. Instead screen time is 3m45s, or an overall time distortion of 2.65.

The first X-wing run gives us a distance from the port of 28000 somethings, and 32 seconds later they are at zero range and fire, assumption 28000m in 32 seconds= 875mps, 2870feet per sec, or 1913mph.

Second Xwing run ( at full throttle) range of 20000 units at 2.0.27, shot at 2.09.55= 1min 28 sec for an event that took 22 seconds to cover the same 20000 units( 20/28*32) at a supposedly slower speed. distortion factor 4.00 or more

now take the 10 sec torp run and divide by 1.85( last 30 sec), 2.50( first 30 sec), 2.65( overall event), 3( superlaser firing process), or 4.00 final run, to get torpedo speed.

duration(s) average speed(km/sec)
5.4 14.81
4.0 20.00
3.77 21.22
3.33 24.02
2.5 32.00

If the X-Wings started with a speed of at least 875mps, then the torps would actually have to accelerate to almost twice the average velocity by the time of impact, assuming a continous acceleration, unless the torpedos were able to instantaneously assume the average speed upon firing.

[Master of Ossus]

It doesn't make the sense that the torpedoes would have required the Force to get in the exhaust. Otherwise, they would have only sent Jedi to do the job

Even with only the targeting computer, there must have been at least a chance of success. Granted, with the Force guiding Luke's AIM, the odds were much greater.

I agree with the slow-motion. There's no way that the filmmakers would have you watch: "look, there's the torpedo... no sorry, it's gone, you missed it. it was only one frame long."

If the Force actually had been required, Dodonna would have tried to evacuate the base as best he could. The attack was a million to one against, but it was the best they could do. If the Force had been required, he would have recognized the impossibility of the task.

[Connor MacLeod]

It doesn't make the sense that the torpedoes would have required the Force to get in the exhaust. Otherwise, they would have only sent Jedi to do the job

Even with only the targeting computer, there must have been at least a chance of success. Granted, with the Force guiding Luke's AIM, the odds were much greater.

I agree with the slow-motion. There's no way that the filmmakers would have you watch: "look, there's the torpedo... no sorry, it's gone, you missed it. it was only one frame long."

The targeting computers wouldn't work because the Empire added heavy-duty jammers capable of fucking up even fighters even at that range after the plans were compressed and stolen by the Rebels. (Source: Essential Guide to Weapons and Technology)

That would only force combat ranges up closer - to allow for targeting systems to punch through the jamming (which is why we saw combat occur at the ranges it did - and why they had to get so close to the port.)

You'll notice they still used electronic targeting gear to lock on to both fighters AND the port (and hte port could be acquired from many tens of km out despite jamming, even if it wasn't going to be guaranteed an accurate shot.

Get teh warhead close enough and it would home in on its own

[Evil Sadistic Bastard]

It doesn't make the sense that the torpedoes would have required the Force to get in the exhaust. Otherwise, they would have only sent Jedi to do the job

Even with only the targeting computer, there must have been at least a chance of success. Granted, with the Force guiding Luke's AIM, the odds were much greater.

I agree with the slow-motion. There's no way that the filmmakers would have you watch: "look, there's the torpedo... no sorry, it's gone, you missed it. it was only one frame long."

Well, I'm not saying that the torps REQUIRED the Force, just that it helped a lot. And Dodonna believed the Jedi were extinct. Even if he didn't, how could he know Luke was one?