How did the AT AT's breach the shield

[Imperial528]

Yeah I suspect it is less to do with how cold Hoth is (airspeeders are of course specifically designed for atmosphere and so were probably tuned for a range of temperatures and pressures that did not include ice worlds as cold as Hoth) and more to do with the tactical considerations.

[Adam Reynolds]

Something I will note about theater shields is that the grounding argument cannot be entirely accurate, given that unprotected organic soldiers have no problem passing through the shields in Clone Wars or Rebels. This contradicts the ICS books, which indicated they were supposed to be killed on contact (one of the advantages of stormtrooper or clonetrooper armor).

What Clone Wars seems to indicate is that it is more about velocity and ground contact (which has been argued to also be the case with capital ship shields to varying degrees).

[Shroom Man 777]

Wait, the frying of unprotected organics might be inconsistent. People are routinely trapped by ray shields. Maybe particle shields might have Dune-esque "the slow blade penetrates the shield" stuff. And there are some "compound" shields blending ray and particle effects...

Heck this might be something that involves the sophistication and computing power of the shield transmitter/projector array and whatever computers direct them... like dumb ones might be only set to either absolutely block anything or block a set of things but leave themselves open for another category of things, whereas the advanced arrays are so smart that they can selectively permit what can and can't go through! Pretty person goes through the field, but water can't. Forbidden/exiled dumb gungans also can't!

[Wien1938]

It occurs to me that there's not really a problem with the ground assault vs planetary shield scenario, if we view a planetary shield as a form of projected energy, materialising at a certain distance and arc from the generator.
If the shield was protecting the airspace above the base of operations, then unless part of a repeating network of projectors, the outer reach would be finite.
Think of it like an umbrella held overhead but wide enough and dipping low enough to keep out the rain. Thus, with a gap between the ground and the edge of the umbrella, the Imperial landing force could land away from the shield edge - also far away from any counterattacking Rebel force covered in their assembly area by orbital bombardment from Star Destroyers - and launch a formal ground attack under the shield.
There they would be able to access air support (with a bit of difficulty), but would lack orbital firepower until the planetary grade shielding had been disabled.
So, no esoteric explanations needed, just standard military logic.

[Galvatron]

Based on what was shown in Zero Hour, I think it's safe to say that the "umbrella" shields extend all the way to the ground.



Note that even the much smaller troop transports accompanying the AT-ATs have to penetrate it as well:



The baffling thing about that scene to me, however, is that TIE fighters then descended from the sky to give the AT-ATs air support against the rebel A-wings, but how did they get through the shield?

[Wien1938]

The answer is probably dramatic licence.The other problem with a pure bubble-shield projection is that the shield would have to emitted under the ground.

[Elfdart]

I always assumed that slow-moving objects could wade through, while high speed objects (including bullets, blaster bolts, etc) would be deflected. Like what you see in TPM.

[Galvatron]

The answer is probably dramatic licence.The other problem with a pure bubble-shield projection is that the shield would have to emitted under the ground.

What makes you think it's a bubble and not a dome?

[Batman]

Hell we KNOW they can do dome shields, and with above-ground generators. Much as we all would prefer to forget it, TPM.

[Galvatron]

Hell, Rebels clearly showed us that the shield protecting Chopper Base was a dome.



The above scene takes place right after Thrawn orders his fleet to cease their orbital bombardment.

[Q99]

Should starfighters that can operate in the freezing vacuum of space be as vulnerable to the cold as atmospheric airspeeders are? I'm not an engineer so I'm truly asking in a non-rhetorical way.

Absolutely. Planets offer a ton of problems space does not.

Stuff icing over? Flying through snow? Parts getting too cold making you run your heaters to the point *other* parts get too hot? (and btw, *that* factor was the one that they were having trouble with with the snowspeeders, they needed to adjust the radiators so it'd keep important stuff warm without melting anything.
That's right, unmodified, they got too *hot* when flying on Hoth) All problems you do not meet in space.

Atmosphere not only changes how much heat you need but how you need to distribute your heating. Stuff that normally would not get cold gets cold, stuff that normally would not get hot gets hot.

[Galvatron]

The new EU also implies that turbolaser firepower is significantly reduced within an atmosphere. Any idea why that would be?

[Q99]

The new EU also implies that turbolaser firepower is significantly reduced within an atmosphere. Any idea why that would be?

Atmosphere dwelling plot fairy steal their power.

[DarthPooky]

The new EU also implies that turbolaser firepower is significantly reduced within an atmosphere. Any idea why that would be?

Hu? We're do you get that from? We know from the Thrawn novel that whether can effect targeting but but I don't remember anything about it effecting the actual firepower.

[Captain Seafort]

Hu? We're do you get that from? We know from the Thrawn novel that whether can effect targeting but but I don't remember anything about it effecting the actual firepower.

I suspect he's talking about this scene. In which what looks like a direct hit from one of an ISD's heavy aft batteries knocks a bloke off his bike. I'd chalk that up to being the most extreme outlier in the history of scifi analysis.

[Galvatron]

Hu? We're do you get that from? We know from the Thrawn novel that whether can effect targeting but but I don't remember anything about it effecting the actual firepower.

I suspect he's talking about this scene. In which what looks like a direct hit from one of an ISD's heavy aft batteries knocks a bloke off his bike. I'd chalk that up to being the most extreme outlier in the history of scifi analysis.

Indeed. I took that into account as well.

As for the Thrawn novel, I can't recall anything about an atmosphere affecting turbolaser targeting, so I'd like to see a citation for that. For my part, it was the following excerpt that led me to believe that turbolaser firepower is diminished by atmosphere:

“Still, Star Destroyers are pretty tough ships. The island also has only one turbolaser, and it’s firing through atmosphere. He may wiggle out yet.”

Notice the context. Why mention the ISD's durability if the speaker wasn't specifically talking about the turbolaser's firepower?

Perhaps this is yet another reason why planetary sieges are so difficult. Planetary atmospheres may dilute orbital laser bombardments to the point that even a relatively weak shield is enough to protect the surface. A stronger shield, like the one on Hoth, may be sufficient to fend off such an attack indefinitely.

[Adam Reynolds]

It also explains why an ion cannon is used at Hoth, that they are likely dissipated less and are thus superior in that context.

[Batman]

Though given the firepower numbers we usually throw around, would atmospheric dispersal really be much of an issue?

As for why they used an ion cannon on Hoth, not only don't I see why the atmospheric dispersal would affect it any less than a turbolaser, but there'a a gazillion possible reasons for that. Space amazon had a sale on ion cannon, turbolasers were out of stock, they found a slightly used one cheap, they didn't have up-to-date drivers for turbolasers...

[Galvatron]

Though given the firepower numbers we usually throw around, would atmospheric dispersal really be much of an issue?

Who knows? We're still talking about a fictional technology. Turbolasers are clearly able to vaporize asteroids in the vacuum of space, but the new canon has both shown and told us that planetary atmosphere has a weakening effect on them. Hell, maybe it's a combination of both atmosphere and range.

And maybe ion cannons are different enough that they aren't affected by either. However, their usefulness is limited because all they seem to do is disrupt a target's power systems without inflicting any actual physical damage.

[DarthPooky]

The more likely explanation of the low OB fire power is that Thrawn ordered the Turbo lasers on lower power because he had orders to take prisoners.

As for Galvatrons quote. I thought that was due to things like cloud cover effecting targeting.

[Galvatron]

There was no indication in the novel that the island had any trouble targeting the ISD.

But this time it wasn’t an ion cannon burst that shot upward from the island’s western shoreline. Instead, it was the intense green fire of a turbolaser salvo from an emplacement to the north of the western ion cannon. The barrage struck the Judicator’s starboard superstructure, burning into and through the hull metal.

A second burst of fire shimmers through the atmosphere, again delivering its energy against Durril’s flagship. Again, Durril makes no move to counter or evade.

A third turbolaser salvo rakes the Star Destroyer. The four undamaged escort ships fire toward the weapon, but once again are too late as the island’s shield closes over it. There is a pattern to the attacks, but Durril fails to recognize or exploit it.

The island’s turbolaser blasts continue to batter the Judicator, tearing at its hull and weapons. The ion cannons have again opened fire, sending fresh barrages at the escort ships, preventing them from moving to assist.

So where did you get this idea about cloud cover or targeting problems?

[DarthPooky]

Sorry I thought I read something like but I'm probably mistaken. I stand corrected.

[texanmarauder]

A planetary shield (like Endor, or Alderaan, or Skarif) has to be breached either by massive power (Death Star), or opened under specific circumstances (the gate over Skarif), or technobabble (StarKiller Base).

Edit: I'll have to take another look at the Last Jedi trailer, now....

just wondering where you got a planetary shield for alderaan? never saw a canon source say they ever had one.....

[Gandalf]

A planetary shield (like Endor, or Alderaan, or Skarif) has to be breached either by massive power (Death Star), or opened under specific circumstances (the gate over Skarif), or technobabble (StarKiller Base).

Edit: I'll have to take another look at the Last Jedi trailer, now....

just wondering where you got a planetary shield for alderaan? never saw a canon source say they ever had one.....

From what I recall, it's mentioned in the New Hope novelisation. Also, it can be inferred from watching the explosion.

[texanmarauder]

From what I recall, it's mentioned in the New Hope novelisation. Also, it can be inferred from watching the explosion.

I used to have that book and I don't remember it ever being mentioned in the novelization. the book did mention some weapons. its kind of irrelevant at this point since the novelizations are now non canon. not really sure how it can be inferred from watching the explosion. sounds like an interpretation based kinda thing.