Possible justifications for Point Defenseless

[Sea Skimmer]

It's also possible they open Honorverse style 'gunports' (or for the Rhodanites, 'Strukturlücken') in the shield for their weapons to fire through. If timed closely enough (which should be easily doable with modern day computing, leave alone a civilization that casually uses advanced AI for farm labour) that'd be visually indistinguishable from firing through the shield.

Really that might not require anything more complex then a power relay connected to the trigger in a manner not unlike an interruptor to fire a machine gun through a propeller. Would depend on how a shield generates it's specific geometry. But nothing says that has to involve computers either, it might be largely set by antenna geometry on installation.

[Q99]

Point defense not being a thing might be a thing if armor is tough, but putting small guns in makes holes and it's just not effective as a defense to put in a small gun and thus open up a path via which small guns will work.

Or the big guns are just too good at stripping them off a large target....

[Jub]

Point defense not being a thing might be a thing if armor is tough, but putting small guns in makes holes and it's just not effective as a defense to put in a small gun and thus open up a path via which small guns will work.

Or the big guns are just too good at stripping them off a large target....

Why do you need a hole? Mount a self-contained unit outside the main armor layer and rely on your other defenses to keep it alive long enough to deter enemy craft light enough to be bothered by point defense. Modern ships don't have to carve holes in their armor to mount their CIWS options so I don't see why a sci-fi ship should need to. Even if they get stripped away they keep fighters and missiles off of you until the enemy's capital ships can engage and tie up/jam/destroy those defenses which already means that enemy carrier style attack need additional support to be effective which means just the threat of point defense has done its job.

Sometimes the threat of a system is enough to force changes in enemy attacks and, with most defensive systems, that's the best you can hope to do.

In Star Wars how much less effective would Rebel hit and fade fighter attacks have been if Imperial escorts were optimized to engage fighters while having enough oomph to make engaging with anything smaller than a light cruiser a risky engagement? Suddenly you're forcing the enemy to send more resources for each attack and even if they're raids are still working you've made them more costly. That's a win even if such defenses aren't as useful in a full-on pitched battle.

[Patroklos]

Why do you need a hole? Mount a self-contained unit outside the main armor layer and rely on your other defenses to keep it alive long enough to deter enemy craft light enough to be bothered by point defense. Modern ships don't have to carve holes in their armor to mount their CIWS options so I don't see why a sci-fi ship should need to. Even if they get stripped away they keep fighters and missiles off of you until the enemy's capital ships can engage and tie up/jam/destroy those defenses which already means that enemy carrier style attack need additional support to be effective which means just the threat of point defense has done its job.

Sometimes the threat of a system is enough to force changes in enemy attacks and, with most defensive systems, that's the best you can hope to do.

I tend to agree with you regarding hull and armor belt penetrations being unnecessary, but given the weapons yields fighters can deliver and we know they can just withstand, its not unreasonable to assume that some primary tap to the ships main power is required for point defense weapons. This should be easy to provide through the armor without compromising the armor. Of course since those fighter weapons can be powered by only a portion of the volume of the fighter itself, you don't need a capital ship reactor to do so. However, note:

1.) Fighter's choose the engagement window usually based on circumstances, so they don't need sustained weapons power when compared to a capital ship point defense which is a.) reactive b.) generally dealing with multiple threats at the same time or quick succession if the enemy is doing it right and c.) given the WWII intentional parallels is usually relying on volume and saturation to ensure hits rather than one shot one kill pinpoint accuracy which means more power required per hit.

2.) Cost. You might be able get self contained PD systems including power, but it would probably mean the equivalent of strapping an X-wing or TIE fighter to your hull per emplacement (minus some systems of course). If PD system costs versus fighter craft costs resemble the real world in any way that becomes a giant cost, as well as cost efficiency loss because you could have just bought some fighters instead to act as a PD screen and be able to do other things when that isn't needed.

[Jub]

1.) Fighter's choose the engagement window usually based on circumstances, so they don't need sustained weapons power when compared to a capital ship point defense which is a.) reactive b.) generally dealing with multiple threats at the same time or quick succession if the enemy is doing it right and c.) given the WWII intentional parallels is usually relying on volume and saturation to ensure hits rather than one shot one kill pinpoint accuracy which means more power required per hit.

Most fighter systems are likely to require rather large power outputs on their own, especially shields and propulsion with extra overhead for a hyperdrive in many fighter models. So being able to cut shields, sensors, propulsion, hyperdrive, etc. will stretch your reactor's power significantly further than a fighter would be able to in terms of endurance. In the case of Star Wars, some fighters have multiday level endurance while that isn't likely to involve them running at full power, it does suggest decent fuel reserves.

You could also run power cables out from existing holes in the armor. It's a bit of a cludge compared to a self-contained unit but it gets you extremely light PD emplacements with very high endurance. Or you could emplace external generators that run clusters of PD emplacements though this is probably worse than making your single emplacements more capable.

2.) Cost. You might be able get self contained PD systems including power, but it would probably mean the equivalent of strapping an X-wing or TIE fighter to your hull per emplacement (minus some systems of course). If PD system costs versus fighter craft costs resemble the real world in any way that becomes a giant cost, as well as cost efficiency loss because you could have just bought some fighters instead to act as a PD screen and be able to do other things when that isn't needed.

I doubt they'd cost nearly as much as a fighter would given the systems you'd be able to strip from a fighter. They're also going to be less voluminous without the need for a pilot which, in the case of something like a TIE, is a significant fraction of a fighter's volume. Having them might also save you from having to launch fighters to deal with certain threats which isn't an insignificant advantage over any sort of prolonged campaign. They also have the advantage of not needing additional crew, not needing service time after each deployment, and engaging missiles/torpedos which a fighter currently engaged in a dogfight wouldn't be able to.

Lastly, when fighters are as large a threat as they seem to be in Star Wars, it also behooves you to design your capital ships to defend against them. After all, we didn't stop putting AA on ships just because they were in a fleet with a carrier.

[Q99]

Why do you need a hole? Mount a self-contained unit outside the main armor layer and rely on your other defenses to keep it alive long enough to deter enemy craft light enough to be bothered by point defense. Modern ships don't have to carve holes in their armor to mount their CIWS options so I don't see why a sci-fi ship should need to. Even if they get stripped away they keep fighters and missiles off of you until the enemy's capital ships can engage and tie up/jam/destroy those defenses which already means that enemy carrier style attack need additional support to be effective which means just the threat of point defense has done its job.

Sometimes the threat of a system is enough to force changes in enemy attacks and, with most defensive systems, that's the best you can hope to do.

In Star Wars how much less effective would Rebel hit and fade fighter attacks have been if Imperial escorts were optimized to engage fighters while having enough oomph to make engaging with anything smaller than a light cruiser a risky engagement? Suddenly you're forcing the enemy to send more resources for each attack and even if they're raids are still working you've made them more costly. That's a win even if such defenses aren't as useful in a full-on pitched battle.

You need power to get to it, don't you? If you've got a self-contained unit separate everything, then now you're spending a lot of expense for something you need very redundantly. If it's drawing from ship's power, it's got a vulnerable point.

And quite possibly, you might be talking something that a proximity blast could scrap off, since it's not behind the good armor. So you get a paradigm where if enemies have PD, then you fire one wide-angle low-penetration blast, and then with the PD removed, can now begin with stuff that could penetrate.

[Jub]

You need power to get to it, don't you? If you've got a self-contained unit separate everything, then now you're spending a lot of expense for something you need very redundantly. If it's drawing from ship's power, it's got a vulnerable point.

And quite possibly, you might be talking something that a proximity blast could scrap off, since it's not behind the good armor. So you get a paradigm where if enemies have PD, then you fire one wide-angle low-penetration blast, and then with the PD removed, can now begin with stuff that could penetrate.

The way I see it have three options for your point defenses that don't cut holes in your armor deck:

1) Self-contained units that have their own power supply and ammo as well as a local control unit. They'd hopefully share sensor data with the ship's main sensors via relays that don't puncture the main hull. This saves the cost of a dedicated sensor suit for each pod.

2) Partially self-contained units that are feed from a small reactor placed outside the main armored hull. These would likely have their own armor and shielding so they're not such easy targets but they'd still be easier to knock out that the ships main weapons. This unit might also serve as a sensor hub for a PD cluster.

3) Units that are powered off of the main reactor with conduits run through existing holes in the main hull. This makes them the hardest to knock out but requires long cable runs that may be hard to design into a ship. You can run the sensor data for these PD turrets along side the power so they probably don't need much by way of sensors.

As for PD being vulnerable, that's true of any external system. It's no more vulnerable than something like a sensor dome, and in Star Wars we've even seen fully enclosed turrets taken down by fighters. Not to mention that if something is tied up going after your PD then it's already made them spend resources both in battle at the tactical level and the strategic level. The goal of PD isn't to make you immune to missiles or fighters but instead to make such attacks more costly for your opposition.

[Q99]

You could very well have stuff like sensor domes retracted behind thicker armor for fights, while PD has to be exposed. It's quite possible for the technologies of a universe to exist where none of those 3 options are really all that worthwhile.

[Patroklos]

You need power to get to it, don't you? If you've got a self-contained unit separate everything, then now you're spending a lot of expense for something you need very redundantly. If it's drawing from ship's power, it's got a vulnerable point.

Not really. The PD weapon itself probably sited on top of penetration , so it doesn't present a weakness to the PD emplacement and it is iherently defended from certain threats by the optimal defensive option. The penetration to the armor probably causes no vulnerability the ship because there are very easy ways to make this the case. You can have the power connection itself be armor, as many armor materials are good conductors. You can have doglegs in the route of the penetration which is effective against things that have to travel in straight lines (radiation, lasers, etc.). This was pretty well solved in real life armored warships. Unless you are talking about an actual hatch transferring physical objects which may require stages of locks (the risk from which can and was 100% designed away, though human error and malfunction still exist in these arrangements) the risk is minimal for something passive like a power cord.

And quite possibly, you might be talking something that a proximity blast could scrap off, since it's not behind the good armor. So you get a paradigm where if enemies have PD, then you fire one wide-angle low-penetration blast, and then with the PD removed, can now begin with stuff that could penetrate.

This was exactly how belligerents attempted to deal with PD in WWII. The British, for instance, when attacking in port warship in France, would send in a flight of mosquitos to rake the ships unarmored (by BB standards) AA and secondary armaments with machine gun fire and bombs in an attempt to kill their crews or otherwise degrade their effectiveness, and then send in a flight of torpedo bombers that would hopefully have a much easier time on their straight predictable attack runs delivering the actually ship killing strike.

You really can't avoid this trade off.

If you make the PDs so armored and powerful they detract from the primary mission armament or other equipment of the ship (assuming PD isn't its primary mission), you start calling into question the necessity of the existence of such ships in the threat environment in the first place.

If you make PDs so vulnerable that they are essentially irrelevant and have the threats they are supposed to counter be dire ship killers (the SW status quo), then you detract from the ship's primary mission's operational feasibility. This is where SW sits now, partially due to effects limitations of at the time for the OT, partially due to story telling considerations given our main characters are fighter jockies of various types, and partially due to video game mechanics over the decades. Its fun to kill a capital ship, and its fun to see them get killed, and its easier to tell an exciting story from a fighter cockpit than a warship bridge. But in reality, almost everything we see in SW space combat calls into question the existence of capital ships in the universe. At least as anything resembling the form we see in canon. They are far to vulnerable to starfighters, and there is very little they do that can't conceivably be accomplished by other means at far less cost. Usually by star fighters.

Also something to consider is that the assumption in this thread seems to be you make PDs self contained because if they get destroyed you don't want that to harm the ship behind them in the process. While thats not something to be ignored, thats not how self contained PDs work in the real world. In the real world the concern is the opposite, that if the SHIP gets disabled (you lose primary power or sensors), the PDs are similary disabled and now the ship is completely defenseless and just sitting around waiting for the finishing blow. The situation is a bit different than SW as modern warships are essentially unarmored and thus more vulnerable to a first hit disabling than a WWII BBs or SW ISD, but keep that in mind.

[Jub]

You could very well have stuff like sensor domes retracted behind thicker armor for fights, while PD has to be exposed. It's quite possible for the technologies of a universe to exist where none of those 3 options are really all that worthwhile.

You can retract your sensors in combat where you need them most? So you're suggesting that when a fight starts you blind yourself before the enemy has a chance to do it?

[U.P. Cinnabar]

Why sensor domes? Why not a phased array like what's installed on the Arleigh Burke class destroyers?

[Simon_Jester]

How do you know that the sensor domes on an ISD aren't phased arrays, or the equivalent of phased arrays for Star Wars sensor technology? We don't see clear evidence of mechanically pointed devices 'under' those domes.

[U.P. Cinnabar]

True. I assumed domes meant like the ones on AWACs craft.

[Patroklos]

I am not sure why you guys think phased arrays are any less, if not more, fragile than sensor domes (keep in mind 99% of of real world sensor "domes" are just old school mechanically spinning arrays encased in a near radiation transparent balloon for protection from the elements) . They are not armor plates, just a collection of fragile electronics in a different form.

Sure they are not as vulnerably placed regarding lines of sight, but they are also hull con formal meaning each array has small sensor arcs, and these sensor arcs rarely overlap for redundancy.

We use phased arrays because they are a superior sensor technology, not because of any advantage in fragility or vulnerability.

[U.P. Cinnabar]

That's what I meant, Patraklos, that they're not as exposed, not that they're any less fragile.

[Sea Skimmer]

I am not sure why you guys think phased arrays are any less, if not more, fragile than sensor domes (keep in mind 99% of of real world sensor "domes" are just old school mechanically spinning arrays encased in a near radiation transparent balloon for protection from the elements) . They are not armor plates, just a collection of fragile electronics in a different form.

Sure they are not as vulnerably placed regarding lines of sight, but they are also hull con formal meaning each array has small sensor arcs, and these sensor arcs rarely overlap for redundancy.

We use phased arrays because they are a superior sensor technology, not because of any advantage in fragility or vulnerability.

No they are much less vulnerable, because each of the hundreds to thousands of array element is independent of the others. If hit by say, shrapnel, a large percentage of the array elements must be hit before the array will stop working. This is also a giant advance for basic reliability against electronics failures. While a simple reflector antenna has little ability to function with holes in the reflector, and none what so ever if the feed horn is damaged.

Downside is they tend to weigh more and consume more power. This is why phased arrays haven't automatically negated all prior tech, though with AESA having come down in price they are now well on the way to doing so.

It is however entirely possible to have a phased array which still has reflector type feedhorns, but the only warship radars to work like that I know of that were like that were the Soviet S-300F fire control sets, which were kinda kludge jobs and obsolete even before the USSR fell. Many missile control sets have a feedhorn to the rear of the phased array, like Patriot, but that isn't a vulnerability problem as the array would protect the feedhorn from shrapnel or strafing kind of threat. The arrays phase shifter redundancy remains.

Phased arrays also may or may not rotate. Plenty of stuff is built new spinning because it means you only need one antenna instead of three or four, and a target centered in a phased array will always be picked better then one at a sharp angle. But the data rate, how many times in a given window you actually detect the target passively or actively, for fixed arrays is vastly superior and that leads to much better tracking data against anything moving at a significant speed. If the target changes course at all the advantages of the fixed array multiply rapidly.

The US worked on armored radar domes using craploads of layers of bonded polyethene but it's pretty clear you wouldn't stop anything stronger then a machine gun bullet or fairly light piece of fragmentation with a sane level of that kind of armor. The weight would add up to the point that it's better to add more antennas.

[Patroklos]

No they are much less vulnerable, because each of the hundreds to thousands of array element is independent of the others. If hit by say, shrapnel, a large percentage of the array elements must be hit before the array will stop working. This is also a giant advance for basic reliability against electronics failures. While a simple reflector antenna has little ability to function with holes in the reflector, and none what so ever if the feed horn is damaged.

In theory, yes. In reality, if you have worked with something like SPY-1D on a regular basis, you know that array elements can be disabled by sea spray on occasion, and anything resembling a high order warhead detonation anywhere on the ship will mission kill the sensor. If not by damaging the elements themselves then by affecting any of the thousand other failure points behind them from wave guides to unseating one of a million circuit cards. The systems are just delicate no matter what you do.

Or the ship just loses power, which given actual battle damage or just DC electrical isolation its a near certainty you won't have the power generation to keep a high end phased array up. At least not in high power.

The good news is that most sntups do have multiple arrays, sometimes with significant separation like the CG-47s, so if you do not suffer a system wide failure you could still have some sectors active. From experience I highly doubt it though. Modern warships just are not designed to be mission capable after a major hit. Some would claim they are not really designed to survive at all after a major hit, but I think that's exaggeration (though not very far off the mark).

[Starglider]

In theory, yes. In reality, if you have worked with something like SPY-1D on a regular basis, you know that array elements can be disabled by sea spray on occasion, and anything resembling a high order warhead detonation anywhere on the ship will mission kill the sensor. If not by damaging the elements themselves then by affecting any of the thousand other failure points behind them from wave guides to unseating one of a million circuit cards. The systems are just delicate no matter what you do.

That was an early generation passively-scanned array. Modern actively scanned arrays don't have all the waveguides and phase shifters, and the transceivers are sealed shock-proof modules.

[LaCroix]

*snip*

c.) given the WWII intentional parallels is usually relying on volume and saturation to ensure hits rather than one shot one kill pinpoint accuracy which means more power required per hit.

True for WWII with projectile weapons (Flak or MG based), where flight time of the projectile was long enough to allow for evasion by simply not flying perfectly straight, and accurracy was impeded by gravity, air density, wind, and a ton of other factors.

Beam weapon PD, otoh, will pretty much insta-hit on the ranges we see in the engagements, the speed of fighters is low enough to visibly track them, so systems should be more than up to it. Beams not arc due to gravity, and there is no air in space. The only thing left is the intrinsic accurracy of their gun setup. So the volume of fire requirements go waaaay down.

[Patroklos]

Turbolasers are not beam weapons as we understand them, and are visibly slower then bullets in many cases. They seem more analogous to really energetic bullets than c traveling beams.

Like kinetic weapons prior to TLJ fucking the setting up, there must be a reason why actual beam weapons are not much in evidence given the truth of the benefits you describe. Some really easy tech that negates their effectiveness.

[The_Saint]

.....
Sometimes the threat of a system is enough to force changes in enemy attacks and, with most defensive systems, that's the best you can hope to do.

In Star Wars how much less effective would Rebel hit and fade fighter attacks have been if Imperial escorts were optimized to engage fighters while having enough oomph to make engaging with anything smaller than a light cruiser a risky engagement? Suddenly you're forcing the enemy to send more resources for each attack and even if they're raids are still working you've made them more costly. That's a win even if such defenses aren't as useful in a full-on pitched battle.

This does come up in universe (old canon) with much discussion amongst Rebel/New Republic pilots regarding Carrack-class light cruisers that are "designed in response to massed fighter attacks".

Pretty much all the old-EU comics and novels have the various pilots stating that hanging around a capital ship in a fighter is tantamount to suicide and that survival is either due to 'luck', devious prior planning or the ever present character shields.

[Q99]

You can retract your sensors in combat where you need them most? So you're suggesting that when a fight starts you blind yourself before the enemy has a chance to do it?

Depending on the tech base, sure. Detonate some area-clearing bombs near you or let your own fighters out (including sensor-carrying ones so you get your info even while minimizing vulnerabilities), or what have you. Temporarily hiding main sensors while under fire is a possible strategy if it greatly reduces your odds of being long-term blinded, increases your survivability, and if you have alternatives.

Hm, a ship who's strategy is to fire off sensor buoys around the area...

[Jub]

You can retract your sensors in combat where you need them most? So you're suggesting that when a fight starts you blind yourself before the enemy has a chance to do it?

Depending on the tech base, sure. Detonate some area-clearing bombs near you or let your own fighters out (including sensor-carrying ones so you get your info even while minimizing vulnerabilities), or what have you. Temporarily hiding main sensors while under fire is a possible strategy if it greatly reduces your odds of being long-term blinded, increases your survivability, and if you have alternatives.

Hm, a ship who's strategy is to fire off sensor buoys around the area...

So you want to retract your own much larger and more powerful sensors and rely on those of much smaller and less capable craft right at the point in time when you need the highest quality sensor data the most... This doesn't make any sense and if you suggested this to an actual designer you'd be laughed out of the damned room. Having an integrated set of data from all sources to help make better combat decisions is a good idea blinding yourself in the middle of a battle and relying on such a system is stupid.

This idea is like wearing a full tint welding mask to a fist fight because they might poke you in the eye or shine a bright flashlight at you. It does solve those problems but at far too great a cost to make any practical sense.

Plus, if you can do this, why not do things the other way around? This lets you use your main sensors in battle alongside your other options while keeping the option of using the other methods if/when your own integrated array isn't an option. Or, to return to the fist fight analogy, like letting your friends take you to the ER if you do get jabbed in the eye at your first fight.

The sensor bouys idea, as a primary sensor system, is also fraught with issues. For one it takes time to deploy such a sensor net so it's difficult to do offensively outside of a seige. Second, your bouys are by necessity going to be broadcasting when in use and thus very easy to track and destroy/disable. Three, you've just given the enemy even more of a reason to run heavier ECM to disrupt the data flow between bouy and command vessel. In theory, it's not a bad idea to deploy a something like sensor bouys if/when time allows as a cheap way to get some early warning in an area without more permanent installations designed for this purpose but in general having proper primary sensors and dedicated AWACs craft will be a better way to go.

[Q99]

So you want to retract your own much larger and more powerful sensors and rely on those of much smaller and less capable craft right at the point in time when you need the highest quality sensor data the most... This doesn't make any sense and if you suggested this to an actual designer you'd be laughed out of the damned room. Having an integrated set of data from all sources to help make better combat decisions is a good idea blinding yourself in the middle of a battle and relying on such a system is stupid.

Unless doing so results in you actively being blinded permanently, and once you're in close the information situation degrades period and that's just part of how things work, once the slugfest begins data degrades and part of the tactics is knowing when to go close for blinding and when done- and if you can do a brief pass when your opponent has their sensors out and you are then you permanently blind them more and then you can kite them to death thanks to your superior sensors since they can't pop them back out.

Remember, we're talking hypothetical tech bases for a space opera. There is no 'it has to work this way,' if writers want to make it so that fighting involves making that kind of choices that's how it works. A paradigm of mutual sensor blindness when battle is engaged would make for some interesting tactics and choices and figuring out how to gain info edges by engaging with some units to blind opponents while keeping others away or what have you could be a very interesting one.



Or heck, maybe you can just weave the sensors into the armor, your whole hull works as a big sensor array, and there's nothing vulnerable at all, unlike PDs, and what blinds you is total armor degradation, if you don't want to do it but still have PD be less good, but I think it's fun.

This idea is like wearing a full tint welding mask to a fist fight because they might poke you in the eye or shine a bright flashlight at you. It does solve those problems but at far too great a cost to make any practical sense.

Plus, if you can do this, why not do things the other way around? This lets you use your main sensors in battle alongside your other options while keeping the option of using the other methods if/when your own integrated array isn't an option. Or, to return to the fist fight analogy, like letting your friends take you to the ER if you do get jabbed in the eye at your first fight.

That really assumes you have a choice in the matter. If you have a choice between a thick visor that mostly-blinds you and being blinded in an eye for a much longer period/permanently, you tolerate the visor... until/unless you can take away their blinder. And note that 'blinding laser weapons' is something that has seen RL research, it's not like blinding opponent ships isn't a line of research weapons designers wouldn't leap at, for pretty much these reasons.

Not quite sure what you mean by 'the other way around.' Of course you use your main sensor when it's an opinion, but the local weapons setup making it not be an option is why you need to have a way to hide them in the first place.

The sensor bouys idea, as a primary sensor system, is also fraught with issues. For one it takes time to deploy such a sensor net so it's difficult to do offensively outside of a seige. Second, your bouys are by necessity going to be broadcasting when in use and thus very easy to track and destroy/disable. Three, you've just given the enemy even more of a reason to run heavier ECM to disrupt the data flow between bouy and command vessel. In theory, it's not a bad idea to deploy a something like sensor bouys if/when time allows as a cheap way to get some early warning in an area without more permanent installations designed for this purpose but in general having proper primary sensors and dedicated AWACs craft will be a better way to go.

That'd be the part of the game, wouldn't it be? You need to send out buoys when you have a chance, you can't let them get too far or the opponent will shoot them down or cut you off from them, while meanwhile you try and take our theirs, and they tell you when your opponent is far enough to pop open main ship sensors- but your opponent will try and fool you and aim to make it so you pop at the wrong time and then they can blind you for real, and meanwhile you're trying to do the same to them, and buoys are a limited resources so you're trying to win before running out and they're trying to run you out....


You say 'You can't doe it this way,' I say 'it sounds to me like some tough tactical calls for commanders.'

[PoisonSymic]

Point defense not being a thing might be a thing if armor is tough, but putting small guns in makes holes and it's just not effective as a defense to put in a small gun and thus open up a path via which small guns will work.

Or the big guns are just too good at stripping them off a large target....

Why do you need a hole? Mount a self-contained unit outside the main armor layer and rely on your other defenses to keep it alive long enough to deter enemy craft light enough to be bothered by point defense. Modern ships don't have to carve holes in their armor to mount their CIWS options so I don't see why a sci-fi ship should need to. Even if they get stripped away they keep fighters and missiles off of you until the enemy's capital ships can engage and tie up/jam/destroy those defenses which already means that enemy carrier style attack need additional support to be effective which means just the threat of point defense has done its job.

It is clearly indicated in TLJ that the siege dreadnought's defensive guns work exactly this way: Poe is able to destroy them even though it's explicitly stated that his X-Wing's weapons are too light to penetrate the dreadnought's hull armor belt.

It is also stated that those defensive guns would lethally no-sell the rebel bomber attack if even one or two survived, thus the need for Poe's Act Of Plot Ace.

In Star Wars how much less effective would Rebel hit and fade fighter attacks have been if Imperial escorts were optimized to engage fighters while having enough oomph to make engaging with anything smaller than a light cruiser a risky engagement? Suddenly you're forcing the enemy to send more resources for each attack and even if they're raids are still working you've made them more costly. That's a win even if such defenses aren't as useful in a full-on pitched battle.

This, too, is largely Act of Plot. The Empire initially underestimated the threat of high end multirole starfighters, and subsequently chose to focus point defense on dedicated platforms -- Lancer class frigates -- which are conveniently absent anytime Rebel Fighter Heroes do their thing.