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Ships should have only an acceleration value and not a speed one


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#21 Kitkun

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Posted 21 January 2009 - 01:05 AM

According to this, your statement, Kitkun, isn't true, as particle shields are the ones that protect ships against micrometeorites, not ray shields.

Right. I was working with the idea that fighters and other small vessels have no particle shields (as stated on Wook), which means that the fighter must have some other form of protection against them, since it's not likely the hull could stand the impact at that speed.

Kitkun, I have the Essential Guide to Vehicles and Vessels in e-book format, just tell me if you want me to send it to you.

Sure! Thanks! If you don't want to upload the whole thing, the first few sections before it starts detailing the units should be fine.

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#22 anakinskysolo

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Posted 21 January 2009 - 01:34 AM

According to this, your statement, Kitkun, isn't true, as particle shields are the ones that protect ships against micrometeorites, not ray shields.

Right. I was working with the idea that fighters and other small vessels have no particle shields (as stated on Wook), which means that the fighter must have some other form of protection against them, since it's not likely the hull could stand the impact at that speed.

Kitkun, I have the Essential Guide to Vehicles and Vessels in e-book format, just tell me if you want me to send it to you.

Sure! Thanks! If you don't want to upload the whole thing, the first few sections before it starts detailing the units should be fine.


Wook states that some fighters and other small vessels do not have RAY shields, but all DO have PARTICLE shields. I think you got it the other way around.

I've attached to this post the first part of EGVV. If you (or anyone) want more of it, just tell me.

BTW, feld, you're welcome, I'm the happiest one here because lots of people have given their opinion on my thread :p

#23 feld

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Posted 21 January 2009 - 02:53 AM

but what you say doesn't explain why all ships that I have seen above a planet have their ion engines activated.

That's true. You don't miss much! Two explanations. First maybe the ion engines must be "idled" at a very low level of power to keep them ready for sudden action. There is some precedent for this. Some real life spacecraft fuel lines have to have heaters on them so that the liquid fuel doesn't freeze between engine firings. Many electronic components don't function properly until warmed up. An ion drive might be similar. There are limits to how fast the steam turbines on warships and other big machinery can safely be taken from "cold iron" to full power.

Second is the idea that the ion engines also generate power for the ship. The could be "bimodal hypermatter reactors". "Bimodal" means that they're designed to generate both thrust and ship's power. I got the idea from a nuclear fission engine that NASA has been working on. Picture here. The NASA design is a nuclear fission rocket that can double as nuclear electric power generator. Here's a slide I did for a class presentation. The stuff is four or five years old but not much has been happening in this area so it's probably still pretty current:

Bimodal_Nuclear_Reactors.jpg

The NASA version was a "closed cycle" power plant, meaning it recycles a working fluid (in this case helium gas). The SW version (in my imagination at least) is a ridiculously much bigger "open cycle" power system, like an automobile or locomotive engine. It expells an exhaust to carry away waste heat. This is good for a spacecraft because you don't need to carry as much waste heat radiator mass around. At "low" power outputs ("only" a 8x10*11 Watts or so - that's Saxton's figure for an ISD with engines at idle) the acceleration from the power stream wouldn't be noticeable to a ship the mass of a Star Destroyer. Crank up to max output by burning more hypermatter fuel and you can start using the reactor for a rocket.

Never did understand why the ISD needed a reactor bulb or a main reactor. The thing has six perfectly good reactors at the back of the ship...with built in exhaust ports called "drive nozzles".

Oh yeah...there is a little tiny bit of SW canon that supports this second theory: Luke blows up the DS 1 by hitting a "thermal exhaust port". That's basically what I'm talking about here. He stuck a pair of proton torpedoes up DS1's tailpipe...

r/
feld

Edited by feld, 21 January 2009 - 02:56 AM.


#24 Kitkun

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Posted 21 January 2009 - 03:18 AM

Commonly, larger ships and structures were protected by both types of shield, though starfighters often only projected ray shields.

I think the way Wook presents it is kinda odd.

Also, the main engines could supplement the repulsorlifts for increased acceleration.

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#25 SpardaSon21

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Posted 21 January 2009 - 03:43 AM

From what I have heard repulsors are hard to scale. Since bigger ships are bigger than fighters, repulsors take more power for their greater mass and capitals simply don't have the room to spare for massive repulsor arrays anyways since they are built and operated entirely in space with no need for atmospheric entry. The Clone Wars ships all doubled as troop transports and landing vessels, which is presumably why they had comparatively less armament for their size than Star Destroyers. They had massive repulsor arrays, which take up vital space. If a ship isn't going to enter atmosphere, repulsors just take up room that could be used for more reactors or armor or guns or ration storage or anything else. That's why the Lusankya needed a massive purpose-built array of repulsor coils to leave Coruscant's atmosphere. It didn't have any of its own. It just had lots of guns and ammo.

#26 Tropical Bob

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Posted 21 January 2009 - 08:05 AM

That's why the Lusankya needed a massive purpose-built array of repulsor coils to leave Coruscant's atmosphere. It didn't have any of its own. It just had lots of guns and ammo.

Could be that since the Lusankya started from "ground level," it would have needed a much larger power output to escape the more powerful gravitic pull of Coruscant at that altitude, so they needed more than what was installed on the ship. Also, the power needed to generate all that might detract from shielding and weapons, which it would need to fight its way out of the planetary shield, past whatever Golan platforms and fleet elements were stationed nearby. So the repulsor cradle might have also hidden extra power generators. Or maybe cradle was installed for the extra output it provided, allowing for a faster escape than if it had been working off of its own power alone.

Wookiepedia mentions that an Executor-class does have repulsors that allow for atmospheric travel.

#27 Kaleb Graff

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Posted 21 January 2009 - 02:53 PM

Wookiepedia mentions that an Executor-class does have repulsors that allow for atmospheric travel.

When did that happen? I thought I'd read all of those books.
Edit: that comes from a Marvel comics source, but contradicts Krytos Trap, which I think is more canon.

Edited by Kaleb Graff, 21 January 2009 - 02:57 PM.


#28 Tropical Bob

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Posted 21 January 2009 - 08:11 PM

Wookiepedia mentions that an Executor-class does have repulsors that allow for atmospheric travel.

When did that happen? I thought I'd read all of those books.
Edit: that comes from a Marvel comics source, but contradicts Krytos Trap, which I think is more canon.

Stackpole didn't appear to have the correct technical specifications of an Executor-class at the time, though (i.e. 8km length, and mention of enough weaponry to reduce only a city to rubble). I also just noticed, glancing back over the passage, that the way the Lusankya's escape was authored could point to the ship being buried more or less vertically, even though other parts of the book describe the burial otherwise. A vertical burial would allow its engines to lift the ship, instead of relying on the repulsorlift cradle.

I still think that any ship would be fitted with repulsorlifts efficient enough for at least simple atmospheric travel. Like, say, if a ship's engines failed or were disabled in combat, and it was pulled into a planet's atmosphere, it would need to be able to right itself and be able to land relatively safely. Then it would need to be able to get back into space somehow.

Edited by Tropical Bob, 21 January 2009 - 08:13 PM.


#29 Kitkun

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Posted 21 January 2009 - 09:37 PM

Well, up until Force Unleashed came out, the Victory and Venator were supposed to be the largest ships able to enter an atmosphere. The ISD was was not supposed to be able to.

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#30 Ki-Tarn

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Posted 21 January 2009 - 10:19 PM

My $0.02 is that they use both for manuvering, hence why everything 'flys' as if in an atmosphere. Hence the 'etherial rudder' commented in one of the fighter data books is the repulsors, cause if they were using just the ion thrusters for maneuvers they'd act more like the Star-Furies from Babylon 5 and be dependent of thrust for motion rather than having to adjust thrust to move around.

Though a Star-Fury would be fun to take on a TIE with as you can't get 'behind' them with their 360x3 axis turns as it continues moving away. :3

Edited by Ki-Tarn, 22 January 2009 - 04:15 AM.


#31 Guest_StarWars_*

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Posted 22 January 2009 - 12:25 AM

Well, up until Force Unleashed came out, the Victory and Venator were supposed to be the largest ships able to enter an atmosphere. The ISD was was not supposed to be able to.

The ISD can't do it in the game either. The thing that happened is that it 'crashed' down to the atmosphere. And I'm sure alot of its systems were horribly damaged from it too.

#32 Kitkun

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Posted 22 January 2009 - 12:44 AM

Oh. My bad. I haven't actually finished the game yet. :p

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#33 Pred the Penguin

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Posted 22 January 2009 - 12:51 AM

Horribly damaged is an understatement. A crash like that, and an ISD will never fly again.

feld's posts make a lot of sense.

I would think that you would need more repulsor power to achieve atmospheric flight, hence certain larger ships with "maneuvering" repulsors only not being able to.

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#34 Pellean

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Posted 22 January 2009 - 02:36 AM

I would think that repulsorlift effective range depended on the design, an probably increases with power and so by size of ship as well. I would also think that there would be decreasing effectiveness the farther away you are.

Yup! Also, you could generate greater torque (hence faster turning rates) by mounting your repulsor coils farther from the center of mass. VICTORY class hull extensions maybe? I've also played with the idea that ships might need to "focus" repulsor coils on a target in pairs...and that mounting them farther apart allows you to "focus" on a planet that is further away...but none of those ideas are really supported by canon one way or another. The Battle of Coruscant observations are on film though.


The pairs idea makes sense. All a repulsor can do is push (or pull- can they do that, or are tractors and repulsors separate engines?). Therefore, all that a single projector could manage is to slide the vessel through space; you need at least two forces to turn something without a fixed pivot point efficiently and without change in position.

An interesting but probably irrelevant thought: We know that vessels with sufficiently strong repulsorlifts can move bodies far more massive than themselves (Centerpoint Station). Inertia usually causes the object with less mass to experience the acceleration; why is the space station able to move planets across the galaxy without being subject to the massive torques involved?
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#35 Tropical Bob

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Posted 22 January 2009 - 05:56 AM

The ISD can't do it in the game either. The thing that happened is that it 'crashed' down to the atmosphere. And I'm sure alot of its systems were horribly damaged from it too.

Play the Kashyyyk mission again, but look off to the right at the beginning.

The one on Raxus Prime did actually enter the atmosphere by itself as well. Starkiller just strained the repulsors and pulled it out of it controlled entry, causing it to crash.

The pairs idea makes sense. All a repulsor can do is push (or pull- can they do that, or are tractors and repulsors separate engines?). Therefore, all that a single projector could manage is to slide the vessel through space; you need at least two forces to turn something without a fixed pivot point efficiently and without change in position.

An interesting but probably irrelevant thought: We know that vessels with sufficiently strong repulsorlifts can move bodies far more massive than themselves (Centerpoint Station). Inertia usually causes the object with less mass to experience the acceleration; why is the space station able to move planets across the galaxy without being subject to the massive torques involved?

I do believe repulsors are for pushing, and tractors are for pulling. Which also begs the question of how did Centerpoint pull the planets to the Corellian system?

The planetary repulsors on each planet supplemented Centerpoint. And while I'm definitely not an expert on this, I know that you can expand and compress space using gravity, so perhaps it's possible to do the same with anti-gravity. Centerpoint had two poles, each containing a large repulsor generator; one could have been used to draw the planet it, while the other held Centerpoint in place by compressing space (Relative to Centerpoint "facing" the planet) "behind" it and expanding space "in front of" it, all enough to the point where the distance traveled by Centerpoint would be infinitesimal. Though I might be wrong (Might? More like probably...).

#36 Pred the Penguin

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Posted 22 January 2009 - 01:21 PM

The fact is, Star Wars isn't an "exact science." Much of it doesn't even make any sense. So unless there's established canon, we'll never know...

But I think we all agree that repulsors are used for ships during atmospheric flight. Even though an ISD is a little out there. It also fits with the Coruscant battle. The question I have now is, how could that possibly be implemented in-game.... :p

I do believe repulsors are for pushing, and tractors are for pulling. Which also begs the question of how did Centerpoint pull the planets to the Corellian system?

Wook says:
A tractor beam (also sometimes called a grappling ray) was a type of controlled force field that could be used to manipulate objects caught within its range and field-of-view.
So I guess it doesn't just pull, but can also move stuff all over the place.. =/

A few things on Wook that are really confusing. Like how tractor beams/repulsors are made.

Anyways, if I get any deeper into this I want be sleeping tonight...

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#37 feld

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Posted 22 January 2009 - 08:53 PM

I agree with those who say that SW ships routinely use both propulsion systems (repulsor and rocket) to varying degrees.

But I think we all agree that repulsors are used for ships during atmospheric flight. Even though an ISD is a little out there. It also fits with the Coruscant battle. The question I have now is, how could that possibly be implemented in-game.... :p

In PR? We don't need to. All the theory "explains" is why it's makes sense for SW spaceships to have a "top speed": it's got something to do the relative velocity between the repulsorlift coil and the body that they're pushing off of. PR doesn't need to change a thing. I suppose you could give ships designed for atmospheric flight a really short wait time for the bombard ability to simulate them entering the atmosphere and hovering 100 miles above the ground combat map providing continuous fire support. This is what I'd want a VSD to do for me if I was a stormie but it's probably very unbalancing in a game. It's probably something the Empire would do...but not sure that you'd want it in the game.

<break><break>
@Tropical Bob: I've thought through your theory about MGLT and max speed being a max "operational" speed. It's a tough call. Saxton's generally right: in free space (i.e. no gravity, drag, etc) a rocket's speed is limited only by the amount of propellant it carries onboard. If we're not assuming repulsorlift, then you're left with the rocket drive. MGLT *could* be the maximum linear speed at which that the maneuvering thrusters can have enough thrust to keep the spacecraft's thrust vector and nose pointed in roughly the same direction (i.e. keep the spacecraft flying generally like an aircraft). Tough to imagine why this is good though...seems like being able to point in directions other than the one I'm going in would be very handy...

EDIT: MGLT *could* be SW-talk for "delta vee" or "velocity increment". i.e. the change in velocity a rocket gets when it expells its entire fuel load. It isn't a "speed" in the traditional sense of "who will win a race"...but it is a measure of how much the propulsion system can change your orbit. The spacecraft with more delta vee could thrust for longer in combat. That would make it more a measure of endurance or maneuverability than speed. Does that make sense with the MGLT chart?

Edited by feld, 22 January 2009 - 08:58 PM.


#38 Guest_StarWars_*

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Posted 22 January 2009 - 09:21 PM

Play the Kashyyyk mission again, but look off to the right at the beginning.

The one on Raxus Prime did actually enter the atmosphere by itself as well. Starkiller just strained the repulsors and pulled it out of it controlled entry, causing it to crash.

We could debate this all day, first off we could assume during the Kashyyyk mission that thoses were Victory-class Star Destroyers and they didn't put in a model for them. Also for the one on Raxus Prime, it actually did crash, via falling from the oribital shipyards most likely in the higher atmosphere where some gravitational pull could move it. Plus, I believe that ships could put their sublight drive on in the atmosphere, but it caused a huge ecosystem damage. And Raxus Prime didn't reallly have an ecosystem...(but this could be just for smaller ships and it could of been higher in the atmosphere, since I remember Han once mentioning it and doing that in the Falcon, the spaceport was not happy with him)

#39 Tropical Bob

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Posted 23 January 2009 - 01:06 AM

EDIT: MGLT *could* be SW-talk for "delta vee" or "velocity increment". i.e. the change in velocity a rocket gets when it expells its entire fuel load. It isn't a "speed" in the traditional sense of "who will win a race"...but it is a measure of how much the propulsion system can change your orbit. The spacecraft with more delta vee could thrust for longer in combat. That would make it more a measure of endurance or maneuverability than speed. Does that make sense with the MGLT chart?

I think it would be tough to make that work with MGLT/s values. Unless that value is what acceleration can be achieved per second by using max thrust...Up until you reach the max velocity. Unfortunately, that would mean that ships would only be able to use maximum thrust for a very short time.

We could debate this all day, first off we could assume during the Kashyyyk mission that thoses were Victory-class Star Destroyers and they didn't put in a model for them. Also for the one on Raxus Prime, it actually did crash, via falling from the oribital shipyards most likely in the higher atmosphere where some gravitational pull could move it. Plus, I believe that ships could put their sublight drive on in the atmosphere, but it caused a huge ecosystem damage. And Raxus Prime didn't reallly have an ecosystem...(but this could be just for smaller ships and it could of been higher in the atmosphere, since I remember Han once mentioning it and doing that in the Falcon, the spaceport was not happy with him)

We can't really assume those are Victory-class Star Destroyers, because they're Imperial-class...If the developers wanted them to be Victory-class, they would have done that.

I thought I remembered the chick calling Starkiller on the comm and saying that the Star Destroyer was coming after him. Plus, if it was crashing, Starkiller wouldn't have to bring it down, because it would have crashed anyway.

Sure, ships can use sublight drive in-atmosphere. The drives push laterally, however, so they can't maintain altitude unless they can create enough lift to do so, but spaceships aren't designed to create lift, so they'd end up nose-diving.

#40 Pred the Penguin

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Posted 23 January 2009 - 02:39 AM

If the developers had thought what they would do to canon by putting an ISD in the sky, then this debate would be going in a different direction.

Anyways, it probably wouldn't be very cost effective to bring an ISD into atmosphere, when you have several perfectly working alternatives.

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