How do Star Destroyers deaccelerate?

[YT300000]

Acceleration Compensators or a tech closely related might be utilized not only to protect the crew from massive G's for acceleration and deceleration but might also be used to help (read stop/slow in this instance) a vessel in high G manuvers.

And would explain why SW fighters maneuver like in space as if they were in an atmosphere.

How?

Well, the fighter turns itself, but would still be flying in the direction it was moving before it turned. The Compensator could kill all the velocity in that direction, allowing the fighter to change tangents very quickly, like it would in an atmosphere.

[PainRack]

Star Wars doesnt have gravitic drives (in the sense of a reactionless dirve, a'la Minbari war cruisers) - the closest thing are repulsors and tracor beams, and in such cases you need a nearby mass to push against

I know

[Connor MacLeod]

And would explain why SW fighters maneuver like in space as if they were in an atmosphere.

How?

Well, the fighter turns itself, but would still be flying in the direction it was moving before it turned. The Compensator could kill all the velocity in that direction, allowing the fighter to change tangents very quickly, like it would in an atmosphere.

And what is it supposed to react against, exactly?

[Crown]

And what is it supposed to react against, exactly?

Local gravitational attractions; planets, capital ships, other fighters.

Just speculating here, but it does explain a lot.

[Winston Blake]

Case in point:Luke used his accelleration compensators to come to a dead stop in HttE.
While this manouver 'did' severly damage his hyperdrive, that may simply be a function of the 'rate' of decelleration instead of a principle problem.
At any rate, it shows such a use of ACs is generally feasible.

Accel compensators are the same thing as inertial dampers (Boba Fett did the same thing in TBH and the SOTE comic to stop/.slow himself).

So ships can use their acceleration compensators/inertial dampers to slow themselves down. Although if Luke was flying his X-Wing and Boba Fett was flying Slave I, then perhaps this technique only works on starfighter-sized craft.

Firing the ship's weapons probably can be used for deceleration purposes as well (via recoil), at least in combat situations)

Ion cannons could also very well double as ion thrusters.

I find it hard to believe that every time an ISD fires a weapon it is accelerated as much and efficiently as firing a thruster would (a piece of technology specifically designed to accelerate the ship).

Can you imagine how difficult space combat would be if every SW ship got jolted around whenever it fired? Not to mention we never see that magnitude of recoil (enough to push the ship around) anywhere.

Using weapons as thrusters is ridiculous.

Well, the fighter turns itself, but would still be flying in the direction it was moving before it turned. The Compensator could kill all the velocity in that direction, allowing the fighter to change tangents very quickly, like it would in an atmosphere.

If "The Compensator" could exert enough force on a fighter to cancel out the ships velocity in any particular direction, then re-accelerate it in another direction, WHY BOTHER WITH ENGINES AT ALL? With the force required to make a Newtonian fighter in space behave like an atmospheric fighter you could just as easily have reactionless drives on every single fighter! It's not like the fighter needs engines to push against an atmosphere and change velocity from the reaction force against wings.

Using acceleration compensators/inertial dampers as thrusters is also ridiculous because reactionless engines violate conservation of momentum. OTOH the quotes at the top of this post can be rationalised by saying thay only small craft use them, and only to decelerate.

Also, reverse thrust (in the literal meaning, not the modern meaning that has been debated in this thread) seems unlikely considering ISDs have huge engines on the back and there is no precedent for forward facing engines that are so small and distributed they are invisible.

From my point of view, this thread could have ended with the very first reply:

Probably just like modern spacecraft do. They turn around and burn with their main engines.

[YT300000]

If "The Compensator" could exert enough force on a fighter to cancel out the ships velocity in any particular direction, then re-accelerate it in another direction, WHY BOTHER WITH ENGINES AT ALL?

Perhaps so that if you're in really deep space, with virtually no gravity around, you don't lose the ability to change course?

[Darth Yoshi]

From my point of view, this thread could have ended with the very first reply:

Probably just like modern spacecraft do. They turn around and burn with their main engines.

The only problem is, we've never seen them do that.

[Winston Blake]

Perhaps so that if you're in really deep space, with virtually no gravity around, you don't lose the ability to change course?

Hmmm, but that really depends on how the compensators work. I assumed from this:

Well, the fighter turns itself, but would still be flying in the direction it was moving before it turned. The Compensator could kill all the velocity in that direction, allowing the fighter to change tangents very quickly, like it would in an atmosphere.

that compensators could exert a force in any direction, anywhere.

Is there any evidence for how compensators work? Do they work like repulsors, and 'push against' gravitational fields? Or can they push in any direction provided a gravitational field is present? Do they weaken with distance from a gravitational field?

It was my assumption that in this context, fighters ALWAYS moved like atmospheric fighters, so the compensators could exert a force any direction, in any part of space.

From my point of view, this thread could have ended with the very first reply:

Probably just like modern spacecraft do. They turn around and burn with their main engines.

The only problem is, we've never seen them do that.

I can't actually recall any scene or anything where an ISD had to slow down. I'd appreciate it if someone knew of some evidence where an ISD should have slowed down by "turning and burning", but didn't.

[Darth Yoshi]

ROTJ, when the Imperial fleet comes around from the far side of Endor. Of course, it's been a while since I've seen the movie, so I may be wrong about that.

[YT300000]

Perhaps so that if you're in really deep space, with virtually no gravity around, you don't lose the ability to change course?

Hmmm, but that really depends on how the compensators work. I assumed from this:

Well, the fighter turns itself, but would still be flying in the direction it was moving before it turned. The Compensator could kill all the velocity in that direction, allowing the fighter to change tangents very quickly, like it would in an atmosphere.

that compensators could exert a force in any direction, anywhere.

Is there any evidence for how compensators work? Do they work like repulsors, and 'push against' gravitational fields? Or can they push in any direction provided a gravitational field is present? Do they weaken with distance from a gravitational field?

To be honest, no one knows how they work.

[Connor MacLeod]

And what is it supposed to react against, exactly?

Local gravitational attractions; planets, capital ships, other fighters.

Just speculating here, but it does explain a lot.

Yes, but that's technically what a repulsor does (or tractor beams for that matter.) They're all "gravitic" devices, so its not surprising that an Acceleratio compensator could do that (its just not designed for it, so its pretty much an emerrgency thing. ) Gravity Well projectors have been utilized to do the same thing (Solo Command - an Imperial Interdictor used its gravity well projectors to avoid a collision)

This is only effective close to any sort of mass or gravity well (other ships, planets, etc.) And as we know from the ANH novelization, repulsors tend to have ranges no greater than a quarter-light second. It generally won't do much good in deep space, though.

[Connor MacLeod]

So ships can use their acceleration compensators/inertial dampers to slow themselves down. Although if Luke was flying his X-Wing and Boba Fett was flying Slave I, then perhaps this technique only works on starfighter-sized craft.

It can, although it does Bad Things to the ship doing it. Its not designed to do things like that. (presumably that is what tractor beams and repulsorlifts are for.)

I find it hard to believe that every time an ISD fires a weapon it is accelerated as much and efficiently as firing a thruster would (a piece of technology specifically designed to accelerate the ship).

Turbolasers have *immense* momentum, particularily the heavy mounts. Considering acclamator guns have yields in the hundreds of gigatons, and as a massless beam (both established in the AOTC ICS), you have a recoil in the e12 kg*m/s range (trillions in other words). Considering that a Star Destrroyer probably masses in the tens or hundreds of millions of tons (probably including fuel) at least, and that a ISD has dozens of such guns ( to say nothing of the heavy turrets, each of which is orders of magnitude more destructive than the Acclamator TLs) , we're talking about some *hefty* recoil.

As for ion cannons, they're streams of relatavistic-moving charged particles (much like an ion engine, duh.) What makes them different in principle, exactly?

Can you imagine how difficult space combat would be if every SW ship got jolted around whenever it fired? Not to mention we never see that magnitude of recoil (enough to push the ship around) anywhere.

Considering the sorts of outputs they are capable of (we're talking teraton/petaton range salvos here), this is inevitable.

Using weapons as thrusters is ridiculous.

So we assume they use magical force fields that act against no discernable mass or other field to manuver, right?

If "The Compensator" could exert enough force on a fighter to cancel out the ships velocity in any particular direction, then re-accelerate it in another direction, WHY BOTHER WITH ENGINES AT ALL? With the force required to make a Newtonian fighter in space behave like an atmospheric fighter you could just as easily have reactionless drives on every single fighter! It's not like the fighter needs engines to push against an atmosphere and change velocity from the reaction force against wings.

Its not a reactionless drive. You need something to PUSH against to generate any sort of propulsive effect. Do you seriously not understand this?

Using acceleration compensators/inertial dampers as thrusters is also ridiculous because reactionless engines violate conservation of momentum. OTOH the quotes at the top of this post can be rationalised by saying thay only small craft use them, and only to decelerate.

If they have some sort of mass to p ush against (another ship, parrticularily a larger one, or a planet), then it makes sense. How the hell do you think repulsors can keep a ship aloft above a planet, exactly?

Also, reverse thrust (in the literal meaning, not the modern meaning that has been debated in this thread) seems unlikely considering ISDs have huge engines on the back and there is no precedent for forward facing engines that are so small and distributed they are invisible.

So explain Endor. How did the Rebel fleet decelerate on its approach to Endor? They didn't spin around and use tail thrusts. (We should point out that X-wings DO Have retros as per the OT ICS, so reverse thrusters are not unheard of.)

From my point of view, this thread could have ended with the very first reply:

Probably just like modern spacecraft do. They turn around and burn with their main engines.

Fine, explain the Rebel fleet decelerating on its approach to Endor.

[Connor MacLeod]

Is there any evidence for how compensators work? Do they work like repulsors, and 'push against' gravitational fields? Or can they push in any direction provided a gravitational field is present? Do they weaken with distance from a gravitational field?

They act to accelerate all objects in their field of influence at a uniform rate equal to the accecleration produced by the ship's engines, thereby eliminating inertia. (If the ship accelerates at 300 gees, then the Acceleration compensators accelerate crew, cargo, etc. at 300 gees.)

And yes, they are related to repulsors and tractor beams.

It was my assumption that in this context, fighters ALWAYS moved like atmospheric fighters, so the compensators could exert a force any direction, in any part of space.

First off, if any device does this, it would be repuslors and tractor beams, and that will only work when they have something to actually *push* against. And even then, how is this going to simulate "atmospheric" flight?

[Winston Blake]

I find it hard to believe that every time an ISD fires a weapon it is accelerated as much and efficiently as firing a thruster would (a piece of technology specifically designed to accelerate the ship).

Turbolasers have *immense* momentum, particularily the heavy mounts. Considering acclamator guns have yields in the hundreds of gigatons, and as a massless beam (both established in the AOTC ICS), you have a recoil in the e12 kg*m/s range (trillions in other words). Considering that a Star Destrroyer probably masses in the tens or hundreds of millions of tons (probably including fuel) at least, and that a ISD has dozens of such guns ( to say nothing of the heavy turrets, each of which is orders of magnitude more destructive than the Acclamator TLs) , we're talking about some *hefty* recoil.

That's useful trivia, but so what? It's clearly not enough force to move the ship around like its engines do. Did you read what you quoted?

As for ion cannons, they're streams of relatavistic-moving charged particles (much like an ion engine, duh.) What makes them different in principle, exactly?

Maybe how one is a weapon and the other is an giant engine. Are you seriously suggesting that ISDs use their weapons to slow down? Because that's what i was responding to. I clearly quoted what i was responding to.

Can you imagine how difficult space combat would be if every SW ship got jolted around whenever it fired? Not to mention we never see that magnitude of recoil (enough to push the ship around) anywhere.

Considering the sorts of outputs they are capable of (we're talking teraton/petaton range salvos here), this is inevitable.

Not if the ship is heavy enough. Maybe i should have chosen a better term than 'jolt'. Recoil is inevitable, but i can't see an ISD being thrown back by a single weapon discharge.

Using weapons as thrusters is ridiculous.

So we assume they use magical force fields that act against no discernable mass or other field to manuver, right?

Did you actually read what i wrote? I was saying that they can't use magical force fields! Have you read the rest of this thread?

If "The Compensator" could exert enough force on a fighter to cancel out the ships velocity in any particular direction, then re-accelerate it in another direction, WHY BOTHER WITH ENGINES AT ALL? With the force required to make a Newtonian fighter in space behave like an atmospheric fighter you could just as easily have reactionless drives on every single fighter! It's not like the fighter needs engines to push against an atmosphere and change velocity from the reaction force against wings.

Its not a reactionless drive. You need something to PUSH against to generate any sort of propulsive effect. Do you seriously not understand this?

I never said it was a reactionless drive. Did you seriously not read the rest of this thread? There are examples of when acceleration compensators have been used to slow ships down, with no mention of a planet directly in front of them. That means applying a magical reactionless force.

I was responding to this:

And would explain why SW fighters maneuver like in space as if they were in an atmosphere.

How?

Well, the fighter turns itself, but would still be flying in the direction it was moving before it turned. The Compensator could kill all the velocity in that direction, allowing the fighter to change tangents very quickly, like it would in an atmosphere.

Using acceleration compensators/inertial dampers as thrusters is also ridiculous because reactionless engines violate conservation of momentum. OTOH the quotes at the top of this post can be rationalised by saying thay only small craft use them, and only to decelerate.

If they have some sort of mass to p ush against (another ship, parrticularily a larger one, or a planet), then it makes sense. How the hell do you think repulsors can keep a ship aloft above a planet, exactly?

You've accused me of proposing reactionless engines when i was obviously using their impossibility as evidence against claims that ships can use their acceleration compensators as retro-thrusters. You've quoted me as saying "is also ridiculous because reactionless engines violate conservation of momentum" when in the previous paragraph you accused me of supporting the idea! You've insulted my intelligence twice, and put words in my mouth.

And i don't know exactly how repulsors work. Qui-Gon/Jar-Jar weren't crushed by an overhead MTT in TPM. Therefore they apparently don't push indiscriminately against matter to generate a reaction force. I was under the impression they somehow pushed against gravitational fields, which you would have seen if you'd read my subsequent post.

So explain Endor. How did the Rebel fleet decelerate on its approach to Endor? They didn't spin around and use tail thrusts.

Well, i don't actually remember that scene (or the one Darth Yoshi mentioned "when the Imperial fleet comes around from the far side of Endor"). I would appreciate if you described it to me.

(We should point out that X-wings DO Have retros as per the OT ICS, so reverse thrusters are not unheard of.)

This is new evidence to me. I've checked my copy and judging by the size difference of a retro-thruster to a main engine, i'm convinced that ISDs could have tiny retro-thrusters. BTW, on the X-Wing, i don't understand how something that small is supposed to counter the engine's force.

From my point of view, this thread could have ended with the very first reply:

Probably just like modern spacecraft do. They turn around and burn with their main engines.

Fine, explain the Rebel fleet decelerating on its approach to Endor.

With your OT ICS evidence, i now think that ISDs have many retro-thrusters over their surface which are too small to be seen, just as Coalition said on the first page.

BTW, can anyone tell me how to put in images from my computer? I can do it with images from the internet, but not from my computer.

[Darth Wong]

Has anybody considered the fact that starships in orbit around a planet may be able to use their repulsorlift drives to push against parts of the planet?

[Winston Blake]

It was my assumption that in this context, fighters ALWAYS moved like atmospheric fighters, so the compensators could exert a force any direction, in any part of space.

First off, if any device does this, it would be repuslors and tractor beams, and that will only work when they have something to actually *push* against. And even then, how is this going to simulate "atmospheric" flight?

I was originally responding to a proposal that acceleration compensators explained why fighters moved like WWII planes. I quoted it:

Well, the fighter turns itself, but would still be flying in the direction it was moving before it turned. The Compensator could kill all the velocity in that direction, allowing the fighter to change tangents very quickly, like it would in an atmosphere.

This implies that the acceleration compensators applied just the right forces in just the right directions to make an X-Wing fly like an airplane. Considering the X-Wing can move in any direction, the acceleration compensators would have had to be capable of applying force in any direction, reactionlessly. I then explained why this didn't make sense, therefore explaining why acceleration compensators can't be responsible for the WWII appearance of fighters!

[Winston Blake]

Has anybody considered the fact that starships in orbit around a planet may be able to use their repulsorlift drives to push against parts of the planet?

To maneuver, or to maintain orbit? I think starships should be able to use repulsors to maintain orbit, because DS1 did it in ANH.

[Darth Wong]

IDEA: if the repulsorlift of a spacecraft points in a certain direction (say "down", so it can do VTOL) and combat occurs in a planet's gravity well (which is almost always the case, since SW ships use hyperdrive to appear in relatively low orbit), it is possible that banking would actually be useful because they would be using their repulsorlift drives to push them in a direction which appears identical to the direction of force produced by aerodynamic lift in modern aircraft.

[Winston Blake]

That's a very interesting idea, i might include that in a scifi story i'll write some day. It certainly solves the space combat manuevering problems well, and in a lot of different scifi at the same time.

But it still doesn't explain why ships engines are always "on" (ie accelerating) when there's no air to generate drag.

And if an ISD inverted to perform a BDZ, it would promptly drop out of the sky.

This idea is similar to the Trekkie one that impulse engines apply force in such a peculiar way as to require banking/etc.

[Darth Wong]

Has anybody considered the fact that starships in orbit around a planet may be able to use their repulsorlift drives to push against parts of the planet?

To maneuver, or to maintain orbit? I think starships should be able to use repulsors to maintain orbit, because DS1 did it in ANH.

It depends on how flexible repulsorlifts are. If they can point them at an arbitrary portion of the planet rather than being limited to its centre of gravity, then they can push themselves around in directions other than up or down in the planet's frame of reference.

[Darth Wong]

That's a very interesting idea, i might include that in a scifi story i'll write some day. It certainly solves the space combat manuevering problems well, and in a lot of different scifi at the same time.

But it still doesn't explain why ships engines are always "on" (ie accelerating) when there's no air to generate drag.

That's a Star Trek problem. I don't believe Star Wars has ever gone into enough dialogue detail on propulsion to make it clear that they actually decelerate when they reduce engine power.

And if an ISD inverted to perform a BDZ, it would promptly drop out of the sky.

Perhaps a capital ship has a more complex and flexible repulsorlift system than a fighter (seems reasonable, given its vastly greater size and complexity); it may be able to point in many directions.

This idea is similar to the Trekkie one that impulse engines apply force in such a peculiar way as to require banking/etc.

True; it is a difficult conundrum to resolve but one that is often necessary because so many special-effects people use aerodynamic movement as a model for spacecraft movement.

[Winston Blake]

That's a very interesting idea, i might include that in a scifi story i'll write some day. It certainly solves the space combat manuevering problems well, and in a lot of different scifi at the same time.

But it still doesn't explain why ships engines are always "on" (ie accelerating) when there's no air to generate drag.

That's a Star Trek problem. I don't believe Star Wars has ever gone into enough dialogue detail on propulsion to make it clear that they actually decelerate when they reduce engine power.

That's not what i was talking about. I meant the way ships' engines are always glowing red/blue/green/etc but they're moving at constant velocity.

[Darth Wong]

That's not what i was talking about. I meant the way ships' engines are always glowing red/blue/green/etc but they're moving at constant velocity.

How do you know they're moving at constant velocity? And might it not be hypothesized that the exhaust cones also serve to dump waste gases produced by the reactor, so that there's a certain minimum output regardless of whether the ship is attempting to accelerate?

[Winston Blake]

Okay, so it's not a problem. Point conceded.

(I was about to mention ships lifting off such as the shuttle in the jungle (ROTJ) and the MF on Tatooine (ANH), but then i realised they were probably using repulsorlifts)

BTW Darth Wong, i sent you an email a few weeks ago about this page on your site:
http://www.stardestroyer.net/Empire/Tec ... ur-SW.html
I mentioned that the picture you labeled "Flash speeder" was actually of a Gian speeder. You drew some conclusions from its identity later on.

[18-Till-I-Die]

Um, i'm no scientist, so if this sounds impossible let me know, but this is always what i thought:

The ion engines aft of teh ship push it forward, countless invisibley small thrusters break it. I figure this happens continuously. The engines push it forard, the breaks stop it, causing it to be imobile until they need to move forward or backwards, at which point they cut the forward or aft engines respectivly. Cutting the 'break's sends the ship hurtling 'forwards'; given enough time and space, it's forward engines can be reactivated and therefore it can break. And the opisate would also be true, of course the forward thrusters are less power so it cant move 'backwards' as fast as it can move' forwards'.

Like a tank moves one tread or another to turn, so then would a shp be able to 'turn' using one side of breaking thrusters. Because fighters are smaller, they can tur faster than larger ships, making it seem like atmospheric maneuvers.

Anyway, i dont think anyone had said this yet, and i think it sounds possible, but i may be wrong.