Question about the Trench Run

Butterbean569 · Post by **Butterbean569** » 2004-12-17 01:53pm

This might be a small nitpick, but...

Alright, we have the rebel snubfighters going down the Death Star Trench in ANH. At the same time, the DS was travelling towards Yavin 4 at a very high rate of speed, right? This got me to thinking: How would the starfighters be able to keep up with the movement of the DS?

It was travelling much faster than any of the starfighters could go (at attack speed anyway), and there would be no way that the pilots would be able to adjust their flight path enough to stay in the trench. I'm not really sure where the trench was in relation to the DS's movement. If it was in the fore area, then the fighters would basically be run over and smash against the bottom of the trench. If it was in the aft, then the fighters would keep popping above the trench. If it was on the dorsal side, then they would have smacked against the sides of the trench...same goes for the ventral side.

Any thoughts? I doubt this has been discussed before, but just in case it has...*Disclaimer* Sorry for talking about something that's already been discussed

Post by **Ghost Rider** » 2004-12-17 01:57pm

Are you saying...given that they were able to keep up with the acceleration of the Death Star the entire TIE fighter battle...that suddenly in the Trench they are unable to?

Butterbean569 · Post by **Butterbean569** » 2004-12-17 02:05pm

I assumed it went like this:

The rebels launch from Yavin 4 and head towards the DS. The DS is heading towards them, so they close very fast on one another. This is where it gets weird IMO. They slow down to "attack speed", which is slow enough for humans to actually be able to react to. Yet, the DS is still travelling at a very fast speed (I have no idea how fast it was going, I'm sure someone has figured it out somewhere. Doesn't really matter though, we know it has to be going much faster than those snubfighters). It seems like the DS is easily able to cover one length of itself in tens of seconds...while it took those starfighters a few minutes to travel down a small fraction of the base.

Perhaps I should have rephrased my question. I really meant that once they got to the DS, how could they have kept a stable position in relation to it if it was going so much faster than them? I was just thinking of the trench itself because that would have been exponentially more impossible (lol), but the fight prior to the trench run can also be included.

Post by **Ghost Rider** » 2004-12-17 02:09pm

You then have to show at some point the X-Wings unable to compete with the Death Star, and given they have shown the ability to hold themselves over the surface as well as fly down into the surface while still holding position, they have the ability.

So what we see is not only the DS accelerating but that the X-Wings can maintain that and more but looks slower as the compete with it running away from them.

So far nothing visual has shown the DS accelerating away from them in any aspect.

Tribun · Post by **Tribun** » 2004-12-17 02:14pm

You could also ask:
"How could airplanes hold a stable relative position to Earth?"
Earth moves with a speed, you would think of as high. But still anything reamains relative to Earth.

Butterbean569 · Post by **Butterbean569** » 2004-12-17 02:40pm

Good points

I was going for more of the "realisim" of the whole thing, but I guess that with suspension of disbelief that's kinda thrown out of the window hehe

So we know that the snubfighters have the ability to keep a relative speed in comparison to the DS, but is there anything that can explain this? The only thing I could come up with is that they used some sort of repulsor technlogy to keep them a minimum distance from the surface. I wouldn't think that thrusters would be powerful enough for them to be able to keep a stable distance. Their main engines only point one way...so being able to go forward, while moving in a different direction to keep a relative distance, seems pretty damn hard.

I'm not a physics major (obviously), but this just doesn't seem possible without some far out sci-fi explanation lol

Edit: Thinking about it more, they would be able to get their momentum to be equal to that of the DS, thus travelling "vertical" at the same speed that the DS is travelling "forwards". This would take precise timing and thrust management I would think (as well as valuable time), and would assume that the DS didn't speed up or slow down at all during the whole battle. So that might be an explanation

Post by **Ghost Rider** » 2004-12-17 02:44pm

Given the complexities of the manuvers of the TIEs as well and the X-Wings, let alone the Millenium Falcon and the ISD. They have the tech.

The ICS have gone into better details but I don't have them on me, but deeming them as just forward engines is a tad faulty since all of SW craft have the enginges in that fashion but have shown immense capabilites regardless.

nasor · Post by **nasor** » 2004-12-17 02:52pm

Tribun wrote:You could also ask:
"How could airplanes hold a stable relative position to Earth?"
Earth moves with a speed, you would think of as high. But still anything reamains relative to Earth.

I think what he’s saying is that the fighters only seem to be traveling a few hundred miles/hour along the surface of the death star, but the death star itself would have been moving through space several orders of magnitude faster than that. It’s possible that the death star was moving at a constant velocity and the fighter ‘matched speed’ with it before beginning their attack run.

But even then, since the fighters were barely skimming along the DS’s surface any sudden acceleration on the part of the DS should have sent the fighters crashing into the surface or flying out into space. Since the death star apparently has fantastic acceleration abilities (100 Gs at least), it’s not clear why whoever was driving the death star didn’t just accelerate briefly and smash into the fighters. Or, during the trench run, they could presumably have decelerated suddenly and flung the fighters out of the trench and into space, where they could be easily picked off by defensive turbolasers. If the rebels were flying 100 meters from the surface and the DS accelerated suddenly the pilots would have had less than half a second to react before they crashed. Maybe their flight computers have some sort of 'terrain following' setting or something.

Since the earth doesn’t accelerate, air planes don’t have this problem.

Butterbean569 · Post by **Butterbean569** » 2004-12-17 02:53pm

That's a pretty good explanation of what I was trying to get at

Batman · Post by **Batman** » 2004-12-17 02:54pm

Butterbean569 wrote:Good points
So we know that the snubfighters have the ability to keep a relative speed in comparison to the DS, but is there anything that can explain this?

Yes. Real world physics.

The only thing I could come up with is that they used some sort of repulsor technlogy to keep them a minimum distance from the surface.

We see them using repulsors in the very same movie. There's no need to 'come up with' anything.

I wouldn't think that thrusters would be powerful enough for them to be able to keep a stable distance.

Since the power reqirement for keeping a stable distance is none whatsoever, thrusters are entirely capable of handling it.

Their main engines only point one way...so being able to go forward, while moving in a different direction to keep a relative distance, seems pretty damn hard.

Care to explain why? Once they have attained standstill relative to the Death Star, there is no effort involved in maintaining that standstill.
Quite to the contrary, the X-Wings would have to actively change their speed WRT the DS.

I'm not a physics major (obviously), but this just doesn't seem possible without some far out sci-fi explanation lol

It's not only possible but actually REQUIRED by ordinary real-world physics.
I'm no physics major either but this should be blindingly obvious.

Post by **Ghost Rider** » 2004-12-17 02:56pm

And the answer is just as simple...it's not a starship wherein you can just twist and go "There.".

Unless someone would like the show the Death Star has that type of agility.

Butterbean569 · Post by **Butterbean569** » 2004-12-17 03:03pm

Ghost Rider wrote:And the answer is just as simple...it's not a starship wherein you can just twist and go "There.".

Unless someone would like the show the Death Star has that type of agility.

What Nasor and I were talking about was a simple change in speed, not a change in direction because of a turn.

Batman:

Yes, it's possible to get the correct momentum in order to be going the same speed as the DS. This would be time consuming, and any change in speed would ruin your day.

nasor · Post by **nasor** » 2004-12-17 03:04pm

Ghost Rider wrote:And the answer is just as simple...it's not a starship wherein you can just twist and go "There.".

Unless someone would like the show the Death Star has that type of agility.

According to this analysis, the DS could pull at least 100 Gs of acceleration.

http://www.stardestroyer.net/Empire/

Actually the problem gets even worse if the DS was still accelerating toward the planet rather than simply ‘coasting’ – and since the imperials were presumably trying to reach the planet as quickly as possible in order to blow it up, that might have been the case. Then matching velocities in the normal sense would have been impossible and the fighters would have had to constantly accelerate in the direction of the DS’s flight in addition to whatever other maneuvers they were performing. And since they were flying all over the curved surface of the DS while maneuvering erratically, that direction of acceleration would have been constantly changing from their point of view.

Edit: woops, that link actually just points to Mike's main page. Look under Technology-->propulsion-->sublight to find what I was trying to link to.

Post by **Ghost Rider** » 2004-12-17 03:08pm

Yes, it can do a lot of things...but do you even think for a second this is going to be sudden in any context to the Starfighters?

Something with the fighters were allowing for it to know the acceleration fo the Death Star and allowed for them to utilize a greater acceleration, so you think if a bunch of DS engineers decided to give a change of speed, the rebel fighters are ignorant somehow.

Explain that part.

Butterbean569 · Post by **Butterbean569** » 2004-12-17 03:11pm

As Nador said in another post, another explanation for this might be an automatic flight control system that is able to "follow terrain". Considering the constraints of human reaction time, this might be the only plausable explanation.

Post by **Ghost Rider** » 2004-12-17 03:14pm

Butterbean569 wrote:As Nador said in another post, another explanation for this might be an automatic flight control system that is able to "follow terrain". Considering the constraints of human reaction time, this might be the only plausable explanation.

Given how useless that would be in many of the other situations, that's obviously not the only thing they have on their computers.

nasor · Post by **nasor** » 2004-12-17 03:15pm

Ghost Rider wrote:Yes, it can do a lot of things...but do you even think for a second this is going to be sudden in any context to the Starfighters?

100 Gs of acceleration might not be sudden from the perspective of a fighter that can pulls thousands of Gs, but it would still be 'sudden' from the perspective of the human flying the craft. With 100 Gs of acceleration you can change your position relative to another object by 100 meters in less than half a second, meaning that if the rebels were flying 100 meters from the surface they would have had less than half a second to react if the DS accelerated.

Something with the fighters were allowing for it to know the acceleration fo the Death Star and allowed for them to utilize a greater acceleration, so you think if a bunch of DS engineers decided to give a change of speed, the rebel fighters are ignorant somehow.

Explain that part.

I'm not sure what you're saying here. If you're asking why the fighters didn't encounter this problem, it could be because the DS was moving at a constant velocity and it didn't occur to the imperials to try a sudden change in acceleration.

nasor · Post by **nasor** » 2004-12-17 03:18pm

Butterbean569 wrote:As Nador said in another post, another explanation for this might be an automatic flight control system that is able to "follow terrain". Considering the constraints of human reaction time, this might be the only plausable explanation.

The thing is, since the fighters were performing all sorts of erratic maneuvers during their attack this would imply that a fighter can pull at least 100 Gs of acceleration in any arbitrary direction regardless of how it’s oriented. Which I suppose is possible, but it would be a bit of a surprise to me.

Butterbean569 · Post by **Butterbean569** » 2004-12-17 03:19pm

A side note:

Does anyone know why Luke's X-Wing was unable to get out of the swamp in Dagobah? Were the thrusters damaged, or was it just "stuck"? If it was just "stuck", then that might show that the thrusters really aren't that powerful...and might not be able to keep up with a DS acceleration without help from the main engines.

Batman · Post by **Batman** » 2004-12-17 03:32pm

Butterbean569 wrote: Yes, it's possible to get the correct momentum in order to be going the same speed as the DS. This would be time consuming, and any change in speed would ruin your day.

Proof that it would be time consuming, please. Especially since we saw the X-Wings do it. Given that the fighters accelleration is at least an order of magnitude higher than the DS's, and given the fact that the Ds DID achieve whatever speed it had at that point...
I'll think about the problems of the DS changing speed once somebody presents evidence that it actually did. I'm reasonably certain that we're not required to explain how the X-Wings dealt with a situation that never happened.
As for Luke's X-Wing on Dagobah, I can't recall him ever even trying to get out of the swamp. For all we know it would have been a trivial exercise.

Post by **LadyTevar** » 2004-12-17 03:38pm

Here's a silly question gentlemen:

Since the DeathStar was the size of a small moon, and had a magnetic field surrounding it (as per ANH), could the Death Star not have had a gravity well that would have allowed the Snubfighters to 'orbit' at a relative speed, and pull off the TrenchRun as if it was on a true planet?

Batman · Post by **Batman** » 2004-12-17 03:47pm

LadyTevar wrote:Here's a silly question gentlemen:
Since the DeathStar was the size of a small moon, and had a magnetic field surrounding it (as per ANH), could the Death Star not have had a gravity well that would have allowed the Snubfighters to 'orbit' at a relative speed, and pull off the TrenchRun as if it was on a true planet?

Impossible to tell without knowing the mass of the DS, and I fail to see how the manetic field factors into it.
Unless it's absurdly dense, though, (caveat:which it actually might be due to the hypermatter fuel)I can't see it having enough gravity to matter.

Hardy · Post by **Hardy** » 2004-12-17 03:49pm

Since the DeathStar was the size of a small moon, and had a magnetic field surrounding it (as per ANH), could the Death Star not have had a gravity well that would have allowed the Snubfighters to 'orbit' at a relative speed, and pull off the TrenchRun as if it was on a true planet?

Yes.

When you're moving in a circle with an 80 km radius at 1 km/s, the centripital force is 12.5 N/kg. That kind of acceleration is about the same as Earth's gravity(9.8 N/kg), the gravity of the Death Star's interior, the gravity of 1E21 kilograms of matter/antimatter(Death Star Fuel?) at 80km away(10.4 N/kg), and consistent with Saxton's derivation of the surface gravity of Coruscant(13.9 N/kg).

Butterbean569 · Post by **Butterbean569** » 2004-12-17 03:51pm

I'm not going to be able to prove that it would be time consuming with figures, but this is how I see it. The DS is travelling very fast towards Yavin 4. The snubfighters are travelling very fast towards the DS. The fighters would have to basically "double back"...by actually reversing course in order to be "caught" by the DS and be travelling at its speed. These fighters can pull off massive G's, so it's definatly possible...but I would think it would take at least a few seconds to get oriented...at which point they would be sitting ducks for TIE's and turbolasers. Not very long, to be sure...but that would still be a bitch to have to do in the middle of a fire fight.

Post by **Ghost Rider** » 2004-12-17 03:52pm

Why would it take a few seconds, given they are accomplishing magintudes of order greater acceleration then the DS?