StarDestroyer.Net BBS

Ender wrote: There are two portions to a shield, the dissipation rate (how fast it dumps energy back into space) and the heat sink. We only have numbers for the dissipation rate for a a few ships, and none for the heat sink. That said, I think I figured out how to derive the numbers for the heat sink.

On a well designed ship, the firepower is approximately the peak reactor power. We see at Endor that during a slugging match, it takes ~30 minutes for shields to fail.

We also see from timing the Devestator chase that the guns can each fire every other second (I have not yet timed the rate of fire shown for heavy guns in ROTS, that could alter this).

This raises the question of where the energy goes when the shields fail, but I believe I have an answer for that.

pg.218: A pair of fighters streraked by, spitting fire. The Falcon's shields glowed and pulsed, absorbing the energy, feeding it into the reactors. There were limits to the amount that could be absorbed that way - in which case the reactor would come apart, taking the ship and everything within a thousand kilometers with it - but for now, each unsuccessful pass fed the Millenium Falcon's engines and her guns.
LANDO CALRISSIAN and the FLAMEWIND of OSEON

Excess energy is pumped into the power system - and this would include the reactor heat sinks. Thus I propose that upon the failure of the shields the energy is directed into the ships heat sinks and radiator system in an attempt to prevent it from destroying the ship itself. One could thus interperate the glowing of the armor of the Imperator hit by the HTL in ROTJ not to be them dissipating the energy of the shot, but the overwhelming energy fomt he shield failure being dumped into the armor as a last resort to stave off destruction.

For the life of me I cannot get this to work in my head. Dissipation rate is usually 1/3 ro 1/5 the peak power,

with the exception being the senatorial barge, which has shielding with a dissipation rate twice that of the peak power. I suspect this may have something to do with the surface area to volume ratio of these ships (owing to radiation being proportional to surface area) but When I check it mathmatically, it doesn't seem to follow. If anyone has any idea how to approximate the dissipation rate, I'd love to hear it.

I have not yet timed the rate of fire shown for heavy guns in ROTS, that could alter this

Connor MacLeod wrote:

Ender wrote: There are two portions to a shield, the dissipation rate (how fast it dumps energy back into space) and the heat sink. We only have numbers for the dissipation rate for a a few ships, and none for the heat sink. That said, I think I figured out how to derive the numbers for the heat sink.

There *might* be three. The rate at which shields can absorb, the heat sink capacity, and the dissipator capacity. I only say "might" though because my impression has always been that the absorption mechinism is very efficient with little to no energy being "lost" in the transfer to the heat sinks. This would I suppose depend on how the transfer actually occurs, though, so I'm largely speculating on this.

On a well designed ship, the firepower is approximately the peak reactor power. We see at Endor that during a slugging match, it takes ~30 minutes for shields to fail.

I'm actually not sure where that comes from - if its an approximation, or if its fact. The Imperials are being bombarded by a smaller number of inferior vessels, and the Imperials (supposedly) aren't really firing back (they're holding back massive broadsides and heavy guns at least early on.. again supposedly.) Which is kind of misleading.

And there is of course, the Core ship in AOTC. If the SPHA-T is in reality equivalent to an ISD HTL (as Curtis believes), then the Core ship's heat sink capacity could not possibly hold half an hour's worth of energy (unless the SPHA-T's firepower was greatly in excess of a HTL, but this would create recoil and momentum problems even greater than already exist with the assumption.)

The Executor in ROTJ could also be problematic for large heat-sink capacities,

as could the Queen's Yacht in TPM (it only takes the core ships a matter of seconds to knock down the Yacht's shields, and I have doubts those bolts were much greater than low to mid GT range, given the observed momentum - or rather the lack thereof.)

Of lesser note are examples such as the ISD battles in "Isard's Revenge" and other novels.. one would be hard-pressed to stretch

Another problem with large heat sink capacities is that all that energy would contribute GREATLY to the mass of the ship - greatly exceeding its dry mass easily.)

Generally, I suspect "effective" heat sink capacities (minus dissipation rate) are designed to withstand probably several minutes worth of sustained bombardment. I would probably also want to emphasize a much greater "dissipation rate" to get rid of energy quicker (as well as to handle larger quantities of energy delivered very rapidly.)

We also see from timing the Devestator chase that the guns can each fire every other second (I have not yet timed the rate of fire shown for heavy guns in ROTS, that could alter this).

LAst time I did timings for the Venators (like in the invisible hand fight) the HTL turrets were firing several times a second (and there is at least one scene in the movie where one witnesses Venator fire three shots off from the same barrel in quick succession.)

This raises the question of where the energy goes when the shields fail, but I believe I have an answer for that.

pg.218: A pair of fighters streraked by, spitting fire. The Falcon's shields glowed and pulsed, absorbing the energy, feeding it into the reactors. There were limits to the amount that could be absorbed that way - in which case the reactor would come apart, taking the ship and everything within a thousand kilometers with it - but for now, each unsuccessful pass fed the Millenium Falcon's engines and her guns.
LANDO CALRISSIAN and the FLAMEWIND of OSEON

Excess energy is pumped into the power system - and this would include the reactor heat sinks. Thus I propose that upon the failure of the shields the energy is directed into the ships heat sinks and radiator system in an attempt to prevent it from destroying the ship itself. One could thus interperate the glowing of the armor of the Imperator hit by the HTL in ROTJ not to be them dissipating the energy of the shot, but the overwhelming energy fomt he shield failure being dumped into the armor as a last resort to stave off destruction.

I think I suggested that the energgy is "recycled" for use by weapons and engines (something that Ssi-Ruuk fighters supposedly do. There was also a smuggler ship by the name of Kierra that IIRC had shields like that. And of course there were the "viper automadons" from Dark Empire 2.) And Lando Calrissian and the Starcave of ThonBoka also suggested naval warships (Imperial I think) carried "recycling" shields. However, someone pointed out to me that there might be problems in converting the "heat" stored in the heat sinks from shield impacts into useable energy (I think - its been awhile since I last discussed the idea.) I'm not sure I buy that, but there you go.

For the life of me I cannot get this to work in my head. Dissipation rate is usually 1/3 ro 1/5 the peak power,

Which is coincidentally consistent with the "Shields 25% of the reactor output" statement from the ISB, though that obviously isnt the original intention.

with the exception being the senatorial barge, which has shielding with a dissipation rate twice that of the peak power. I suspect this may have something to do with the surface area to volume ratio of these ships (owing to radiation being proportional to surface area) but When I check it mathmatically, it doesn't seem to follow. If anyone has any idea how to approximate the dissipation rate, I'd love to hear it.

AFAIK, surface area/volume doesn't have a great deal to do with heat dissipation capacity. SW ships (at least going by the ICSs) tend to have very small radiating surfaces and they clearly don't glow brightly, so it seems that with a neutrino-based radiator (which is mentioned in the AOTC/ROTS icses) surface area isn't a major factor.

The probable reason for the unusually high "dissipation rate" relative to the power generation systems is that the ship is an unarmed consular ship, and the high dissipation rate allows it to better deal with very rapid deliveries of large amounts of energy (Curtis implied on his SPHA-T page that if you deliver a given quantity of energy very quickly, you can locally overwhelm the shielding, at least temporarily. Heat dissipation rates are measured in watts remember, so the faster the energy is delivered, the less energy can actually be radiated away in a given amount of time.)

Its quite possible and likely that shield characteristics and designs vary greatly according to dissipation rate, heat sink capacity, and whatnot. Some ships might favor much greater heat sink capacities (especially if they have the "recycling" s hields and such systems do exist and can reliably work.) over dissipation rates, whereas some ships might favor much higher dissipation rates over heat sink capacities.

SPHAT page wrote:The maximum continuous heat disposal by the shield system of a core ship is rated as 6×1023 W [statistics in AOTC:ICS]. Up to this total limit, continuous attacks from all directions can be absorbed into the shield mechanisms and re-radiated in harmless forms, while the energy field comprising the shield is simultaneously replenished. A sufficiently strong and abrupt surge could deplete the shield's potential energy locally (exposing a region of the hull), but the duration must be short. Firstly there is a naturally time-scale of feedback between the generators and the affected location of the shielded space. Secondly, there may be diffusion or wave propagation between neighbouring regions of the field. The shields, being massless, are probably mediated by light-speed phenomena, in which case local shield effects would only be apparent for surges of less than a few microseconds (width of the core ship's shields divided by c). Thus local shield failure isn't a plausible explanation for the success of SPHA-T attacks lasting a second or so. For long-duration attacks, we must compare total firepower and shield power directly.

Power Technologies page wrote:The process of ray shielding involves the reflection, diffusion or absorption and transfer of harmful energies. However the firepower that the shield disposes can be far greater than the power that the shield generator draws from the ship's reactor. A mirror consumes no power when it reflects a ray of light. An initially concentrated light beam may diffuse in an opaque fog, without the fog requiring power input — this is an example of passive scattering. Analogously, the perfect deflection or splintering of incoming blaster fire may require little or no energy consumption.

Splintering events are analogous to particle decay tracks photographed in the bubble chambers of old-fashioned particle physics experiments. The incident beam splits into daughter beams in a way that (generally) conserves the total momentum and energy. The daughter rays may decay further. The decay probability per unit length along a ray must depend on the energy density ratio between the beam and the ambient shield. If the decay rate is high enough, the recursive splintering cascade reduces the initially coherent beam into a diffuse ball of energy. When the decay rate is low, the shot passes through the shield volume with minimal (if any) splintering events.

Incoming firepower that is absorbed by the shield system must ultimately be re-radiated as waste heat of some kind. If starships are to avoid being melted by energy thermalised by their shields during enemy barrages, then they need two things: internal heat sinks with enormous heat capacities, and an efficient means of eventually removing the heat accumulated in these sinks. In effect, this aspect of the shield system acts like a refrigerator heat-pump, which consumes some power in order to transport and expunge a much larger amount of heat energy.

The mechanism to expunge waste heat might consist of warm radiators surfaces exposed to space, giving off thermal photons (in other words, “blackbody radiation”). However photonic radiators have the inevitable disadvantage that a fraction of the emissions falls upon adjacent areas of the ship's own hull. Self-heating might indirectly limit the effectiveness of shielding systems. Furthermore, few observed ships have hulls that are as black as an efficient radiator must be, and the absence of visible thermal glow implies temperatures no more than a few hundred K. A device that emits neutrinos as carriers of heat energy would be a better possibility. Neutrinos interact with atomic matter negligibly, and can shine freely through everything except perhaps the most exotic constituents of the ship. Neutrino emission is significant in some natural objects, e.g. harmlessly carrying away half the energy released in a supernova explosion. A starship with an extensive and effective shield system with heat sinks linked to neutrino radiators might be able to endure firepower far greater than the vessel's own maximum reactor output.

Prequel technologies page wrote:Shields
Shield technologies are represented in a very striking way in The Phantom Menace, but they're not necessarily irreconcilable with the movies of the classic STAR WARS era. The key difference is that the shields seen in action in The Phantom Menace were mostly in atmosphere, and they are not necessarily all the same type.

The first noteworthy and novel example of shielding in The Phantom Menace is the person-scale shielding projected by the droidekas of the Trade Federation. Droids using their shields usually remain stationary (with the one exception being the last droideka fleeing Anakin Skywalker's defence of the Theed hangar). It is unknown whether the shields innately make movement difficult, can only be activated by a motionless droid, or whether there is a deliberate restriction on droideka behaviour. Perhaps the absorption of heavy fire by the shields produces a kick that can knock over a droideka that doesn't stand with braced legs. (Whether their legs protrude from the shields, and whether the shields penetrate the ground may also have some bearing on this question.)

Shielded droidekas appear to be surrounded by a soft purple spherical haze. This haze is probably due to the interaction between the shield and the air aboard the Trade Federation ship. It may be airglow due to ionisation of the air in contact with a part of the shield that sits at an energy level or potential corresponding to an appropriate atomic or molecular transition of a constituent of the air.

An alternative, more complex explanation would be that the shield permeates the air but causes some kind of sharp alteration of the air's optical properties along a certain surface. Such an effect would have to be very sensitive to the wavelength of incident light in order to create the observed monochromatic haze. This is not the best theory, since it requires the specification of much more awkward ad hoc detail.

In any case, droidekas operating in vacuum would not show any visible shield effects; except for the ordinary splintering and absorption of incident blaster bolts.

Another interesting feature of the droideka shields is that the machines' own blasters are able to fire through them. This implies that these particular ray shields (and perhaps ray shields in general) are a vector or tensor effect. In other words, the effectiveness of shielding against incident bolts depends on direction, rather than all blaster shots being degraded equally. This model of shielding could account for the ability of large warships to fire upon their foes whilst keeping their own shields raised.

Second theory: the shields are lowered in instantaneous synchornism with the firing of the blaster bolts. This fine timing should be within the scope of droid technology, since comparable precision is achieved in many kinds of devices on Earth today, including the synchronised firing of machine-guns through propellers of World War I aircraft. However the initial activation of droideka shields is slow, taking an appreciable fraction of a second. The slowness of changing the shield activation state may preclude the rapid activation and deactivation needed to account for the observed bolt-passing. Perhaps shield generators have more complex capabilities permitting rapid switching despite the sluggish response implied by the initial activation, but it would be hard to prove on the basis of the presently slender evidence.

A seemingly simpler possibility is that the droids actually poke the muzzles of their blasters outside the shields when firing. Inanimate matter that moves sufficiently slowly can penetrate most particle shields, and ray shields needn't impede the movement of material objects at all. (In the hangar scenes it is obvious that the shield penetrates the floor, and therefore it should be possible for the guns to protrude as well.) Judging by eye, the muzzles certainly seem very close to the verge of the shield. On the other hand the blaster shots also cause an expanding elliptical flash or reflection that appears to propagate on along the shield's airglow surface. This flash suggests an interaction between bolts and shields. Bolt-shield interaction may require the bolt to be within the shield at that point, or alternatively it may be a kind of reflection effect.

A final interesting observation concerning the droideka shields is the fact that they were either invisible or inactive during the battle with the Grand Army of the Gungans. The significance of this is uncertain:


It may be that the shields are somehow inhibited when they are projected within the Gungans' stronger theatre shield. If it was a case of incapacity or inhibition then it seems to have been the shield itself that was affected, and not just its airglow, because Jar Jar Binks managed to blast the leg off a droideka, using a conventional infantry gun.

Alternatively, there may have been a tactical reason for fighting without shields. The Gungans weren't (initially) equipped with blasters and their blue explosives may be too substantial for shields to block, so the droids may have decided that shielding was redundant. Power unspent on shields may then be redirected to weapons or other systems.

A third possibility is that the common droids deployed on the battlefield lack shield generators, which may be a non-standard luxury option reserved for the security droidekas aboard the Trade Federation spacecraft. This theory is supported by the fact that Kenobi recognised the shielded versions as "destroyers" (implying familiarity) but then he was surprised by the shield capabilities. Such a distinction between security and infantry models would also agree with the apparent differences of intelligence between the security and ordinary battle-droids.
The Gungans deploy combined ray and deflector shielding from both large area generators and hand-held personal devices. These shields create striking airglow effects and also appear to refract light along a shell-like volume near the limits of the shield's range. This is probably due to the momentum-damping function of the particle shield. Molecules in the air crossing into the shield tend to be slowed or repelled away more rapidly, depending on the shield's settings. On the macroscopic scale this influence may be felt as a dramatic alteration of the temperature and density of the gas. The visible result is similar to a natural mirage effect formed by air layers of different temperatures near a hot ground.

A blaster bolt striking ray shielding in empty space becomes divided into a shower of lesser daughter bolts which must radiate their energy as harmless light more rapidly because of the increased surface area. The daughter bolts are necessarily more susceptible to further decay, and when the shield is stronger than the bolt the shower decays into an almost indefinite cascade of branching splinters so that it is dissipated as a mere blink of light. (These effects are obvious in frame-by-frame inspections of the shot that incapacitated the Tantive IV and the superlaser striking Alderaan's global shield in A New Hope.) The presence of atmosphere when a bolt strikes a shield changes the manner of dissipation. Some of the cascade energy can interact with the gas molecules via the shield, as well as with the shield directly. This additional mechanism changes the visible characteristics of the bolt diffusion. This was seen when battle droids fired upon Anakin Skywalker's grounded N-1 Naboo starfighter inside the hangars of the droid control ship. The bolts were instantly converted into a flash of pearly airglow diffused across a shield contour.

These pretty effects are unlike the visible manifestations of shields in previous STAR WARS movies. However they are not inconsistent, because they are demonstrations of shield-atmosphere interactions, which were rarely seen before. Shields in space are always invisible, and their influence on shots from beam weaponry is to create either a visible bolt-shower or a tighter flash-like decay cascade. The N-1 fighters hit by enemy fire in space did not show a pearly glow, and the most powerful example of shielding in the movie, the shields of the Federation control ship, behaved the same as the shielding of large vessels in every other STAR WARS film.

The Naboo pilots found the droid control ship's shields to be too strong for their attacks to be effective within the time available for their mission. We can assume that this refers to the ray shielding, which could effectively dissipate blaster fire from the fighters within a distance short enough that the hull remains unharmed. The ship must have had powerful deflector shielding as well, in order to give it immunity to any physical attacks, such as figher collisions and the impact of any proton torpedoes fired by the Naboo.

There were two noteworthy incidents involving the Federation vessel's shield capabilities. The first was when three N-1 fighters flying and firing in formation managed to destroy a large antenna dish and were engulfed in the ensuing explosion. This demonstrates some kind of weakness; perhaps the shielding is less effective around structures with sharp edges, or perhaps the shielding is weaker in the presence of the dish transmissions. In any case, this incident demonstrates that the Naboo mission was not totally hopeless, although they may have needed to much more time before they could hope to eliminate the rest of the transcievers.

The second interesting incident was when Anakin Skywalker's violently spinning fighter penetrated the droid control ship by passing through the aperature of the starboard hold. The ineffectiveness of the shield at that moment needs explanation. Some commentators assume that deflector shields are only scalar phenomena, failing to differentiate between incoming and outgoing objects, which would mean that the shields would have to be lowered during the launch of Federation fighters. This would expose the ship's interior in a wide variety of combat situations, and is therefore unvelievably impractical. If we indulge this theory, for the sake of argument, then Skwyalker must have entered the hold while Federation craft were entering or exiting. More realistically, the shields may be directional, but they were temporarily turned inwards because of incoming Federation fighters. Skywalker's pursuers might have triggered this effect automatically.

Alternatively, there may have been something about Skwyalker's motion that allowed him to pass the shield unscathed. Conventionally, deflector shields are less effective on slow-moving objects; so perhaps the damaged N-1 fighter was moving slowly enough that it wasn't discriminated. However the N-1 seemed fast enough to be a dangerous projectile, even though it was slower than a proton torpedo, and therefore a well-designed deflector shield ought to have impeded or blocked it. Perhaps the permission of Anakin's N-1 had something to do with its spin; it looked as if the fighter had more rotational kinetic energy than linear kinetic energy. If deflector shields exert a complicated vector or tensor force then perhaps a transient configuration of the hangar shield had an effect that was concentrated against the fighter's spin, or which coupled the spin to the forward motion in some way.

The Phantom Menace also reveals more of the tacit properties of ray shielding. The Gungan personal shields represent the first known example of ray shielding that causes a deflection of a blaster bolt. The Gungan infanry used their shields to reflect blaster bolts back in the general direction of their attackers. Ray shields on starships usually either cause an incident bolt to decay into a cascade of splinters or a more instantaneous blossum of harmless light if the shield is stronger. The reflection of undivided blaster bolts can probably be regarded as an extremely weak version of the splintering interaction, in which there is no splitting. The mirror-like agreement between the angles of incidence and reflection would then be a straightforward consequence of the conservation of energy/momentum.

Sometimes the blaster bolts seemed to be changed by reflection. A hail of bolts reflected from the front-line shields had less than the expected deadly effect on the advancing battle droid ranks. This may mean that the bolts lost energy despite remaining unsplit. However at least one blast was reflected by a Gungan during the later melee, and the attacking droid was disabled convincingly. There must be some variability in either the blaster setting, the effect of relfection, or the durability of the droids. (Perhaps that particular droid had already sustained damage.)


Asides:

In The Empire Strikes back the Millennium Falcon received enemy fire on its shields while in Bespin's atmosphere. None of the pearly glow effects were seen, which may say something about the power or concentration of the freighter's shields. Perhaps the difference occurs due to the absence of deflector shielding, which usually but not necessarily operates in conjuction with ray shielding. It is the deflector shields that interact directly with matter such as projectiles and air molecules. In one noteworthy instance, an enemy strike was dissipated at a point that was several metres from the freighter's hull. This must be the minimum extent of the freighter's ray shields, and it obviously isn't a tightly hull-hugging effect. These blossums of dissipated bolts are also seen in abundance in space battles throughout the STAR WARS movies. Each of these flashes can be understood as a bolt shower that is so heavily branched and rapidly diffused that it appears as a continuous blob of luminosity.

In The Courtship of Princess Leia Prince Isolder used a personal deflector and ray shield [pp. 51-52] similar to those of Trade Federation droidekas. The airglow effects described in the book are almost identical to those seen onscreen. The book explains several important aspects of their use: contact with the shield scorches living tissue (which is a concern for live soldiers but not for droids); and personal shields don't have power sources that are great enough and portable enough for extended use by infantry. Thus they are an expensive anti-assassination device for humans but combat droids designed to carry their sufficiently heavy power systems could benefit from shielding. The Gungan personal shields may also be a short-duration device, perhaps recharged by the mobile power generators behind their lines. (It is interesting to note that no Gungan personal shields were seen in action after the collapse of their theatre shield generators.)

In Entertainment Weekly Rob Coleman, animation director for TPM, confirms an important element of particle-shield physics. The effect of particle shielding is velocity-dependent.
Why is it that Qui-Gon, Obi-Wan and the Trade Federation droids can pass through the Gungan bubbles and force fields, but laser beams can't? It's because those things are made out of a plasma-like material -- mined from the ocean floor by the Gungans -- that can be penetrated only by moving "reeeeeeaaallly" slow, 'If you hit it very violently, you don't get in,' says Coleman. 'Velocity is important.'

Alderaan page wrote:Alderaan's Shield
The superlaser beam strikes the planet and a bright glow spreads away from the point of contact and expands to cover the entire globe within a few frames of the movie. Let's consider several possible explanations for the nature of this time-varying glow.

Reflected glow from the superlaser beam: We see any superlaser/turbolaser/blaster beam because its constituent massless quanta can radiate or decay to produce visible photons as a byproduct, and this emission shines in all directions off to the sides, not just the original beam direction. The glow on the face of Alderaan might be explained as a reflection of the beam's lateral emissions. This illumination should be maximum where the beam hits the globe, and appear dimmer with radial distance. However the glow on Alderaan spreads and brightens, and this doesn't make sense because the superlaser beam (as a direct light source) remains constant (from the camera's point of view).
Directed illumination: The glow could be a conical beam of light shone from the Death Star witihin some angle surrounding the superlaser beam. Imagine it as something like a spot-light that rapidly expands in angle. But why would the superlaser weapon need such an effect, or (alternatively) what could account for such a highly directed side-effect that varies even while the superlaser remains constantly intense? This explanation seems implausibly non-functional and complicated.
Beam/shield interaction: According to Lord Vader [ANH novel, pp.129-130] Alderaan's defences were as good as any in the Empire. That implies a full planetary shield system like that of Coruscant [e.g. The Last Commmand]. Every ray shield attempts to limit the damaging effecs of an incident beam by inducing it to split into a cascade of less intense daughter rays, which are scattered through large angles, and also by direct absorption and re-diffusion of incident energy. Absorbed energy is dumped into internal heat sinks for later, gradual irradiation (e.g. in the form of relatively harmless neutrinos from some starships [AOTC:ICS]). The spreading glow on the face of Alderaan may be the visible consequence of superlaser beam power being partially diffused away from the point of contact. After this momentary effort, the shield is overwhelmed (both in terms of its diffusive and absorptive capacities) and the planet explodes.
The visible beam/shield interaction is presently simplest and most self-consistent explanation. This commentary proceeds by adopting that conclusion.

In this case the destruction of Alderaan is a valuable demonstration of some aspects of shield physics. In the interval between frames 2 and 3, the extent of the glow has increased (approximately) from ¼ to ½ of the planetary diameter. If the movie has the standard 24/s frame rate, then the characteristic speed for the diffusion of an energy surge in the Alderaan planetary shield is approximately 0.25c. This is an interesting measurement in shield physics. Do other shields handle incident beams with a comparable diffusion speed? Is this speed a characteristic of the propagation or fluxes of the energy quanta that carry the invisible field effect that we call a "ray shield"?

Ender wrote: True, there is definately a time delay, but given observed transfer rates (EG the Alderaan shield spreading the DS blast at about .25C) I think it can be ignored for now.

I always kinda figured it was fact, as it is on this site and has been a staple of the vs debate for a long time and I can't imagine it not getting challenged long ago if it was just an estimate.

Further, the ROTS novel says the Battle of Coruscant had been going on a couple of hours (Grievous's comments to Dooku about getting out of the system), so I figure 30 minutes of heavy bombardment would be conservative. But yeah, it would be nice to nail it down a bit more.

I figure intensity and absorbtion rates come into play to explain that away. With a surface area of 1.52*10^6 meters and a dissipation rate of 6*10^23 watts then the shields has a local dissipation rate of 3.9*10^17 watts/m^2. Since it takes time to transfer energy across the shield (Alderaan), intensify definately plays a factor. A quick shot of a lot of energy could overcome the local dissipation rate and then either the local heat sinks of absorption rate to penetrate. So there doesn't have to be a contradiction here. Especially since we don't know the actual intensity of the SPHA-T beam.

I don't think so - while the shields dissipation rate would follow with the overall surface area, the fact that only certain sections of shields can fall ijmplies to me that the heat sinks are local. So the heat sink capacity for the bridge shields would be much less then the total heat sink capacity for the shields.

Right now I'm soley dealing with warships, to me the shields of small transports like that and fighters have clearly got to have something different going on in terms of the combo between absorption, capacity, and dissipation.

I don't know. We don't see a lot of that battle. It's joined, and then it cuts to all the heavy weaponry destroyed and them engaging with just the light weapons.

I don't think that's much of an issue - very little manuvering is done during combat due to all the ships having vry close accelerations. So if you keep adding to your mass like that it shouldn't change too much.

Yeah, we need to quantify the time applied firepower is good for better.

Interesting

Well converting heat into usable energy is very inefficient - Carnot law and all that. I remember getting told in power school that 30% was the physical limit, but they simplified and dumbed down so much stuff there I'm not sure that is accurate. Plus when you account for the differences in material technologies you could probably expect a shift. But yeah, heat engines are pretty poor.

That statement isn't really relevent though, as it is about power consumed to power and maintain the shields, not the shields capabilities.

I think that's for taking care of the waste heat produced on the ship itself. I'm talking about the dissipation rate for the shields. It is readily observable that shields spread the energy overthemselves as they reradiate it (Alderaan, Droidekas, Mon cal ships at Endor). Therefore the surface area of the shields would be a factor. The fact that they convert most of it to neutrinos may complicate things though, but the basics of heat transfer should still apply.

Right, but if higher dissipation rates then the power of the reactor can be done, one would expect that on the warships as well unless there is some reason not to. The Senatorial barge's unusual shape gives it a greater surface area then volume, which firs with heat transfer and is why I suspected that surface area played a role. For other ships like the coreship and Acclamator the values are lower. Of course none of the ships in AOTC ICS are dedicated warships, maybe that is what is making this tough. Fucking DK and axing the numbers in ROTS ICS.

See the bit about shields/surfaces glowing brightly. I think that a big role played is how quickly the energy is "released" TL bolts in the movies deliver their energy in a fraction of a second consistently. Since they use capacitors, it does make sense that they can probably "alter" how quickly it can be delivered (although this negates the ability to deliver sustained fire.. it would be less a "slugging" match and more of a sniping/fencing battle.) Missiles warheads are probably more effective at this than beam weapons in general, though.

Oh I definately think that is the case, it would best explain things WRT transports and fighters. however one would expect warships to all go for the same combo in terms of absorption rates, capacities, and dissipation rates because one combo would have been determined to be optimal for combat. So I'm trying to figure out how we derive values for that combo.

and the Invisible Hand (Anakin firing on the atmospheric containment shield.. there are cirular interactions before the bolts damage the target.)

Connor MacLeod wrote:

Ender wrote: True, there is definately a time delay, but given observed transfer rates (EG the Alderaan shield spreading the DS blast at about .25C) I think it can be ignored for now.

On further reading of Curtis's stuff (as noted below and discussedo n AIM) I'm not sure the third one exists (or at least Curtis doesnt seem to think it does, in the way mentioned. Perhaps thats what that "brief" localized hole a rapid delivery of energy can create is about... but that would just be it.

I always kinda figured it was fact, as it is on this site and has been a staple of the vs debate for a long time and I can't imagine it not getting challenged long ago if it was just an estimate.

I've never really seen it discussed, so I can't say if there's a quote for it or not. (I do know that it took "minutes" for the Rebel fleet to get into point blank range with the Imperials, if that means anything. But it might not, for the reasons I outlined above (dispartiy in power, Imperials holding back, etc.)

Further, the ROTS novel says the Battle of Coruscant had been going on a couple of hours (Grievous's comments to Dooku about getting out of the system), so I figure 30 minutes of heavy bombardment would be conservative. But yeah, it would be nice to nail it down a bit more.

There's an awful lot of variables I cna think of that would complicate such a generalization (are the Republic naval forces out numbered? did they get reinforcements - like the Open Circle fleet arriving... etc.) From watching the movie I didn't notice many examples of "shield interactions", save on the battleships (you can consistently see multipel blue flashes) and the Invisible Hand (Anakin firing on the atmospheric containment shield.. there are cirular interactions before the bolts damage the target.)

I figure intensity and absorbtion rates come into play to explain that away. With a surface area of 1.52*10^6 meters and a dissipation rate of 6*10^23 watts then the shields has a local dissipation rate of 3.9*10^17 watts/m^2. Since it takes time to transfer energy across the shield (Alderaan), intensify definately plays a factor. A quick shot of a lot of energy could overcome the local dissipation rate and then either the local heat sinks of absorption rate to penetrate. So there doesn't have to be a contradiction here. Especially since we don't know the actual intensity of the SPHA-T beam.

As I mentioned before, intensity may be a non-factor where the dissipation rate is concerned (it might be more of a factor for the "brief hole" created by very rapid deliveries of energy, but that seems to be it.) Again, according to Curtis, local failures do not adequately explain the SPHA-T incident.

I don't think so - while the shields dissipation rate would follow with the overall surface area, the fact that only certain sections of shields can fall ijmplies to me that the heat sinks are local. So the heat sink capacity for the bridge shields would be much less then the total heat sink capacity for the shields.

It probably varies according to design. Localized individual heat sinks provide better redunacny (losing one does not neccesarily take out your entire capacity), but the individual capacity could be much lower (and thus its easier to "burn out" specific sections by raw firepower.) Whereas a more centralized sink capacity is probably larger and can absorb more punishment, but it feeds into all facings equally.

Right now I'm soley dealing with warships, to me the shields of small transports like that and fighters have clearly got to have something different going on in terms of the combo between absorption, capacity, and dissipation.

The Queen's yacht is nearly of the scale of a Blockade Runner and Republic Cruiser, so I imagine it would be a fairly valid benchmark, even if it isnt a military vessel. Its certainly not small enough to qualify as a fighter.

I don't know. We don't see a lot of that battle. It's joined, and then it cuts to all the heavy weaponry destroyed and them engaging with just the light weapons.

You have to breach the shields first in order to reach the weapons, though. The scenario doesnt offer much wiggle room to allow half an hour or more, though

I don't think that's much of an issue - very little manuvering is done during combat due to all the ships having vry close accelerations. So if you keep adding to your mass like that it shouldn't change too much.

Depends on your strategy and situation. Since you can dump max output into either guns or engines, you generally have to balancec between one or the other in combat. You're not gonna move much if you are using full powered guns, but then you're also a fairly predictable target (even at long ranges) Moving at least has the benefit of giving one the ability to avoid getting hit by at least some fire and forces your opponent to spread out his shots in order to gain at least some hits.

Yeah, we need to quantify the time applied firepower is good for better.

Well my point is is that while heat sink capacity is important to an extent, an effective way to get rid of the energy is likewise important (even moreso, since if youo can dump it out alot faster than it can come in, you don't neccesarily need as greater a sink capacity to begin with.)

Well converting heat into usable energy is very inefficient - Carnot law and all that. I remember getting told in power school that 30% was the physical limit, but they simplified and dumbed down so much stuff there I'm not sure that is accurate. Plus when you account for the differences in material technologies you could probably expect a shift. But yeah, heat engines are pretty poor.

If the Viper is any indication they can do it quite efficiently (at least where ground combat is concerned.) Then again, they appear to be able to convert waste heat into massless particles like neutrinos, it woudl stand to reason they can convert it into other forms (like charged particles or EM energy.) And its possible any energy absorbed might come from momentum (momentum from an impact is going to impart *huge* acceleration to the generator, which must be braced against Perhaps they tap that acceleration/recoil somehow.)

I think that's for taking care of the waste heat produced on the ship itself. I'm talking about the dissipation rate for the shields. It is readily observable that shields spread the energy overthemselves as they reradiate it (Alderaan, Droidekas, Mon cal ships at Endor). Therefore the surface area of the shields would be a factor. The fact that they convert most of it to neutrinos may complicate things though, but the basics of heat transfer should still apply.

The obvious problem I see with this is that the radiators we see in the DK books are too tiny to be effective in any thermal sense with the magnitude of energy we deal with. Certainly too tiny to be effective against the energies expected to overwhelm the dissipation rate. (wouldn't the shield have to "glow" brightly with all the emitted heat? Since we're dealign with stellar scale power levels and such. Which also has the undesirable side effect of making you a much more observable target to your enemy... stealth would be much more pointelss at this point I imagine.)

On the other hand, we know they DO have neutrino radiators.. what possible reason would preclude their use on shields (even if we didnt know already frrom the DK book sthat they ARE used with shields?) Its a rather good way of disposing of waste heat.

Right, but if higher dissipation rates then the power of the reactor can be done, one would expect that on the warships as well unless there is some reason not to. The Senatorial barge's unusual shape gives it a greater surface area then volume, which firs with heat transfer and is why I suspected that surface area played a role. For other ships like the coreship and Acclamator the values are lower. Of course none of the ships in AOTC ICS are dedicated warships, maybe that is what is making this tough. Fucking DK and axing the numbers in ROTS ICS.

See the bit about shields/surfaces glowing brightly.

I think that a big role played is how quickly the energy is "released" TL bolts in the movies deliver their energy in a fraction of a second consistently.

Since they use capacitors, it does make sense that they can probably "alter" how quickly it can be delivered (although this negates the ability to deliver sustained fire.. it would be less a "slugging" match and more of a sniping/fencing battle.)

Missiles warheads are probably more effective at this than beam weapons in general, though.

Oh I definately think that is the case, it would best explain things WRT transports and fighters. however one would expect warships to all go for the same combo in terms of absorption rates, capacities, and dissipation rates because one combo would have been determined to be optimal for combat. So I'm trying to figure out how we derive values for that combo.

There's enough variation in Star Wars (with its technology) to allow for some "advantages" to be gained by doing things differently (think of the SPHA-T.) If it were that consistent, then it would simply be a matter of "biggest ship always winning" - which does not really mesh with ROTJ and the Executor and the communications ship (even IF you factor in "holding back" -the communications ship was obviously not "held back" enough to actually destroy the ship or ships engaging him, and the Rebels did not have the equivalent of 100 ISDs at Endor.)

EDIT: also, consider the fact the Separatists appeared to be making extensive use of heavy projectile/warhead weapons against the Republic, despite their advantages (and the fact their energy weapons were consistently weaker than their Republican counterparts.)

Ender wrote:Yeah, the heat transfer rate to the sinks doesn't seem to ever be particularily relevent, and frankly I don't know enough about it to be able to say if it is a factor or not. I figure just ignore it as the elephant in the corner for now.

Well, the Imps holding back isn't relevent as the assumption is that Mon cal cruisers are at least as powerful.

I need to get bit torrent figured out so I can get a non POS copy to analyze.

Then lets call it transmission rate then, the time it takes for the energy to be absorbed or transfered to the radiators.

And while I haven't looked real hard at it, what exactly is so messed up with the SPHA-T incident?

How do you figure? In terms ove volume, surface area or something? The yacht is no where near as long as the others, nor I beleive as deep. In role yes, they are similar, but not in scale.

Yes, but most accelerations we see in battle are single or double digit Gs at best.

Further, when you convert it, the mass added by the energy seems to be less then the total mass of the ship by at least an order of magnitude, so it wouldnt' change its flight characteristics that much.

A bigger issue whould be its relation to the thruist source and center of mass for recoil concerns.

I'm not sure how sound those ideas are WRT engineering and plausibility. I definately know that using a difference in temperature produces a current though.

Yes, but its a bit tricky when you start thinking about it in other scales. Look at planetary shields - they use the crust as a heat sink. That gives you a pretty limited capacity before you start fucking up your biosphere.
Then you have the fact that as a heat sink, it sucks. It doesn't transmit energy fast enough for the scale we are talking about. You would melt the ground around the shield generator station. Then you have to draw it back out into the neutrino radiator, which again has problems with transmission.

My original idea was that the material that makes up the shield would break down into neutrinos when large ammounts of energy were applied. The heat sinks would handle the excess and resupply it to the shields as soon as they could dissipate it. Since the material breaks down, you would have to resupply it a lot (hence the importance of directing more power to the shields, the basic fields that control the shape of the shields would not be affected as the shield wore down as near as I can figure.

Well, I figure ifthe shields are rereleasing the energy as neutrinos, then since neutrinos don't react with your eyes the glow bit is less relevent.

So far as I know, all timing showed 1/15th of a second. But I don't think anyone has checked the prequels yet.

I figuired capacitors were so that the ship could continue to fight for a period if the reactor scrammed, or so that they could fight back and defend themselves in the time it takes to bring the reactor online to peak power if they were sneak attacked

In varying the power levels? I don't see how. Reactions are set by physical limits as far as I know.

Flak bursts for CWIS makes sense in space. And what evidence says their guns are consistently weaker? The biggest guns in the BoC were on seppie ships.

Ender wrote:I just retimed the battle of Endor. At 1 hour 40 minutes in, the Liberty is destroyed. The novel describes it as being engaged in a furious long range battle. So while the Empire might have been holding back, the rebels sure weren't. At 1 hour 44 minutes, we see rebel fighters fly over a damaged star destroyer (Its sensor globe is destroyed). Thus by 4 minutes the shields were at least flickering.

However, as we also see shields still deflecting explosions immediately prior to and after that, it appears flickering is the case, though it might just have been the one ships was pounded especially hard and the others were not.

Further, we don't know how long the rebel cruisers had been pounding imperial ships prior to that point, making this a very low end number.

This is also when the order goes out to engage each other at point blank range, ensuring that from this point on as much firepower as possible is being poured onto the Imperial ships.

At 1 hour 50 minutes we again see the space battle, and see definate cases of shields flickering, and some shots are blocked while at the same time some get through. At time 1 hour 58 minutes though, it is clear shields have failed when we see a Mon cal cruiser annihilate an Imperator class.

While the argument can be made that these times are unreliable because we don't know if the cut scenes are sequential or simultaneous, the counter argument is that there is clear evidence of time cuts that mean we should lengthen the time it takes to knock down the shields - example given when han calls for help to et the blast doors open.

Alan Bolte wrote:One really interesting sequence for fighter shields would have to be the Slave I chasing Kenobi's fighter and firing at it continuously. I've watched that sequence many times, and I strongly get the impression that Kenobi's shields are getting hit many times during the chase. Eventually, you see a lot of pyrotechnics, a couple of blast marks appear on the ship, and Boba declares "You got him!" Why Jango doesn't just finish him off with lasers then and there I don't know, but it would seem to me that we have a duration for the craft going from minimal heat stored to full heat sinks, as well as what it looks like for fighter shields to fail. Perhaps now that the heat sinks are fairly full, and possibly some damage has been done to the shielding system, a single powerful blast is more useful than putting energy into keeping the heat sinks full while occasionally getting a damaging hit. On the other hand, perhaps Jango had nearly depleted his cannons' capacitors.

Alan Bolte wrote:I think I be gaining some understanding of this.

So far I have yet to see any real evidence that the deflector shield itself is in any way involved in the dissipation of heat stored in the heat sink(s). As far as dumping heat into the planet goes, I don't really see why it's necessary to dump the majority if you have neutrino radiators. Obviously there will still be some heat that must be dissipated as blackbody radiation, but hopefully not enough to cause the problems you're describing.

I don't think shield glow really has anything to do with the listed dissipation rate, instead it seems reasonable to me that it is only the result of splintering or diffusion events. The glow is the color of the impacting bolt because it consists of many small bolts with a vastly increased rate of decay.

I suppose it is possible in some cases that shield interaction causes a change in color or the light produced by beam decay, but I feel that glows of a different color are more likely the result of some other mechanism.

Most of the energy remains invisble, as it is in a laser beam. As a result, being next to a scattering event would be like getting hit with an explosion or a relatively low intensity beam, even though the visible glow doesn't come anywhere near you.

Absorbtion does not necessarily and probably does not have any kind of visible result. This may explain why we so frequently see bolts impact a warship with no visible result at all: their relative intensity and angle relative to the shield geometry prevented significant scattering events, but the shield was able to completely absorb the incoming energy.

A particular segment of a shield is weakened for only a few microseconds before the generator can send more power to to the relevent projector, thereby replenishing the potential energy of the force field. Obviously, the projector must be able to channel this power surge into the generator, which is then able to transfer it safely to a heat sink, otherwise the equipment would be damaged by the heat. A much greater power surge could potentially damage the generator, causing the entire shield to collapse. Of course, on a ship with multiple generators, only the shield region would fail. This is prevented by the fuse-like nature of the projector's "matrix boards" (EGWT), which supposedly can be replaced in minutes if the projector is accessable.

The situation is a bit different for a ship with full heat sinks. As suggested in the OP (I think, not entirely sure I understood you), incoming bolts cannot be absorbed, so only scattering and relection events can occur.
Many bolts will simply be spread by the shields, causing the hull to glow as it is heated somewhat evenly in a small area around the impact. The superconducting nature of the armor helps spread the heat even more. Just how incoming fire is absorbed by the system I'm not clear on, nor whether this would require the projectors to decrease the energy content of the shields.

Connor MacLeod wrote:And of course we don't know the exact output of the guns. The ymight be max power, they might not be.