Sea Skimmer wrote:Simon_Jester wrote:Shooting it repeatedly with 'merely ordinary' heavy antiship weapons might do the job- you'd cause so much shattering that you might well knock the thing back into a stable orbit, and would tend to reduce the problem to one of large numbers of individually smaller fragments you could take on the planetary shields.
To a certain size that would work, and actually project mass back into higher orbits. Past a point though gravity is a thing, and you planet could face being drown in a thick layer of dust if nothing else. If it settled on top of your shield it could block out the sun!
True, but an industrial civilization that can build life support or generate electrical power on the scale of Star Wars might be able to deal with having the sun blocked out, or other kinds of Chicxulub-level planetary disasters. It wouldn't be
good, but it could very well be possible given skill, determination, and planning.
Blowing up my planet, by contrast, is the kind of thing I'm not going to get to rebuild from. Hence the Death Star superlaser.
Or on not wanting to gamble on their eternal superiority. It's like building walls for your city in an ancient or medieval context. You hope your field army can keep them at bay, but it's so much better to have walls and not need them than to need walls and not have them!
Yeah but on the other hand nobody ever built walls that would repel the entire planet attacking, and in Star Wars a single city being attacked by the whole world is the kind of force mismatch you would precisely expect.
Well, you can't build a mobile fleet to withstand the whole galaxy attacking either. Remember that a lot of the incentive to build these defenses is against threats significantly smaller in scope than the Republic as a whole. As some hypotheticals:
1) Suppose you're worried about a Trade Federation blockade fleet, or its equivalent. The Trade Federation may be big, but there are going to be limits on how much fleet they deem it profitable to send. Being able to reach up from orbit with the equivalent of V-150 heavy ion cannon and zap their droid battleships might just deter them from trying to attack at all.
2) Suppose you're worried about a purely local conflict between your own planet and a neighboring one. There is ample evidence in the EU (much of it old EU, admittedly) that the Republic does not always intervene in such conflicts, or does not do so in a timely manner.
3) Likewise, suppose you're concerned about some of the larger and more formidable pirate forces out there. Warlike opportunists have gotten their hands on star destroyer-sized ships before. And, again, the Republic doesn't always put them down as quickly as you might like.
There would be a lot of worlds in the Star Wars galaxy for which some or all of these issues are not a concern, but they do represent plausible reasons to fortify your planet, without building up fortifications to a level that could stop the Republic (or the Empire) if they mobilized their full strength.
Notionally such platforms could be in clusters protected by a collective shield overlaid on top of a planet wide shield, forming a series of space based strongpoints, or even by shields projected from the planetary surface if that someone provides an energy generation advantage. Such platforms though must have some engine, or the enemy could just shove them out of orbit. But then that would also mean they could cluster and disperse too. In peacetime they might be in much higher orbits too, because that's better for securing local space.
I'm reminded of the Golan platform series, though those appear to have been entirely immobile and not generally well integrated into planetary shields.
Yeah, but you saw me do the math. No matter how tall your flak towers are, you don't really want to have to fire parallel to the horizon or at extremely shallow angles. So you do wind up needing at least 6-8 sites to cover the whole planet properly, and more would be highly desirable.
Shallow angles? I want usable depression on these guns. Remember just by employing any anti capital weapon were are accepting some kind of probability that 1-10 mile scale exploding starships fall out of the sky onto our world because that's how gravity works. Were not going to limit the firing arcs on our guns out of fear. Not if its more then a token defense anyway.
Getting good
depression on these guns is pretty much a non-starter.
I ran the numbers two pages ago for a fifty-kilometer flak tower, which is so high it's almost exoatmospheric.
Assuming there's nothing sticking up above sea level to get in your line of fire, your maximum angle of depression is 7.16 degrees. And any shot you fire at a significant angle of depression will skim the lower atmosphere for hundreds of kilometers. Now, assume for the sake of argument that we don't care about the energy releases on the planetary surface, even though said releases take place hundreds of kilometers from the flak tower's base, so that they could potentially cause major collateral damage
per shot even if we built the tower in the middle of nowhere with a 200-km exclusion zone around the base or something.
Even so, punching through that much air is almost certainly going to cause major problems with accuracy and beam dispersion for an energy weapon. You are unlikely to be effective from a tactical standpoint, compared to firing the same weapon up at a significant angle of elevation. Or even firing on the level, if you've got a flak tower like that to shoot from.
Angles of depression on less batshit insane flak towers, or for turrets mounted on a realistic mountaintop, are going to be a lot smaller. And you still have the problem of skimming through huge amounts of atmosphere.
So I'm not arguing against relying on these guns having angles of depression "out of fear." I'm arguing that the guns are likely to be relatively ineffective
and cause unusual collateral damage when fired at angles of depression, so that it's a bad idea to plan the defense around that happening.
Agreed. The catch is that if you only have a single-digit number of installations spread across the entire planet providing surface-to-space firepower, the blind spots in your firing arcs are hundreds of kilometers high. That stretches the definition of "low altitude" pretty far.
Yeah but you'd site that so those blind spots are over oceans, while you have gun coverage over your cities. Of course a lot depends on how many shield generator sites are needed, and if they each sector scan or actually project a uniform field.
That would help, although it also means that your gun emplacements are closer to places you don't want wrecked either by sidescatter or by enemy fire.
Like having mounting the fortifications on islands hundreds of miles offshore or on top of remote mountains whose sides have been artificially steepened into 200-meter cliffs. Rioters aren't going to be able to get close unless they're flying. At which point you have light surface beam mounts to ionize and tractor anything that flies too close without a transponder code.
They have flying cars in this universe! Seriously, this whole universe is predicated on ultra high mobility for everyone, everywhere and up to the scale of a galaxy. Physical defenses don't solve the riot mob problem, that's a problem of the willingness of the people defending them to keep them out of the hands of the mob. The advantage of mobile platforms is you can remove them from the disturbed area, hopefully before you have a problem, and put them under the control of your elite regime protection mooks at a safe spot. Can't do this with giant fixed buildings.
Well, if the people manning planetary defense installations don't have the will to keep out rioters or strange YT-1300s, you're probably screwed anyway.
Plus, things like 200-meter cliffs or the gun platform being on a remote island may not
stop rioters, but they certainly tend to discourage them. If people have to travel for a couple of hours at supersonic speeds, out into the middle of the Siberian tundra or its equivalent, and then enter an air traffic exclusion zone where turreted ion cannons can zap their car, just to get to the perimeter fence of your installation...
At that point, you're not really worrying about rioters attacking the installation. You're worrying about an armed revolutionary movement of fifth columnists, committed enough to launch military attacks against military facilities. Which is certainly a plausible threat, but if so then your real problem isn't your ability to defend the planet from a space attack. It's the ongoing civil war being fought
ON your planet.
In that context the mobile platforms are very much useful, though the fixed platforms also remain useful by doing exactly what they did at Hoth: deterring the enemy from sending heavy starships in over the areas still under your control to provide direct orbital fire support, and preventing the attacker from establishing a close blockade. At that point, they are back to being deterrent weapons instead of trading fire with the attacking fleet, though.
That's why it doesn't make sense to invest in more then minimal defenses. Like I said before, the enemy will just decline to grant you a battle that will make it pay off. The offensive value of a fortress is in providing a fixed pivot for maneuver, not in blowing up attackers. It's always been this way, the long walls of Athens for example mattered because they secured the Athenian Navy.
I think we're in agreement on this, and the only question is what constitutes "minimal defenses" and how to design them. I figure a lot of planets that don't
specifically fear attack might just establish a planetary shield and give up, aside from maybe some fighters in key areas just to stop random pirates from showing up in the equivalent of a Corellian corvette while your shields are down for maintenance.
Planets that anticipate attack being a realistic threat might well want anticapital guns, in which case the minimum required to consider yourself "defended" would be about, oh, ten plus or minus two installations- as few as four or six maybe, but that might be pushing it.
Avoiding close blockade seems relevant to a theater shield much more so then a whole planetary fortress. If you want to get serious about avoiding a blockade the only option I see is building in orbit, even adding moons if you could and fortifying those, until you have a protected roadstead and fleet base in orbit big enough for hyperjumps. But installations like this would be rare. Also this would protect all the civilian stuff your bound to have in orbit too.
I was discussing close blockade in the context of
after the enemy has a bridgehead on the planet, but while you're still trying to resist them getting to expand it. Basically, you don't want the enemy operating freely in low orbit over
your part of the planet that they don't occupy yet. And if they try that, you want the option of either potting a few of their ships, or of being able to do something like the Rebels did at Hoth and run blockade runners out through the planetary shield under covering fire from your own defense guns.
Conversely, you want to deter them from even trying to operate in low orbit over unoccupied territory, because they know damn well you can do that.
A big variable in this is just how much of the power generation on starwars ships is needed for firepower vs mobility. Hyperdrive can use the same power weapons do for example, because you never fire in hyperspace, while all sublight power, which is clearly linked to hyperspace power but not completely the same, needs to be usable while firing. It seems unlikely that an ISD for example can go full speed and use utter maximum firepower, but no reason exists why it could not. Its possible the power systems are totally non compatible, and that the ship actually has a large over design margin of power. We don't know.
Generally though the more and more power weapons-shields are going to eat, probably the less it matters if you have engines too as long as your ship isn't trying to be fast.The cost difference for ground based weapons may be very low. We have rather strong cost divisions in real life because in real life because we never pushed gun performance all that high.
True. On the other hand, I remember hearing arguments derived from the old calcs that a star destroyer actually needs something like 90 to 99% of its power output for the engines, and that even at maximum Base Delta Zero firepower the weapons are dramatically less energetic than the sublight drive. I could be misremembering, I suppose, but
if true that would make static fortifications (planetary or orbital) a lot more economical than mobile vessels. Unless those mobile vessels were so slow compared to starships that they were functionally nailed to the floor in tactical terms.