The Role of Ground Forces in Interstellar Warfare

[Marduk]

@Marduk

1) And volume and weight are going to be important constraints on anything mobile, which is critical to long term survival.

No, not really. Look at current AA system designs. Who cares, get bigger trucks, or split the system between several trucks. Not everything is a tank or submarine.
Trucks may not be free, but they are dirt cheap compared to the cost of miniaturizing high performance ground to air or ground to orbit systems.

2) I'm not sure if this is a language issue, but something built somewhere else, and imported in, is imported. They are imported aircraft, unless they're a high performance aircraft built in Africa I'm unaware of.

My point was t hat they aren't imported in a hurry when a war seems to be closing in, so the import time is irrelevant, they are kept around.

3) Or, should a tank have zero anti air ability, or is a 50 cal on a tank still useful, if marginal? That's the relevant comparison.

Look at modern tank designs, the answer is there. Useless, except against ground targets lol.

4) I don't get your point here.

If they have such large industrial capacity, they would be far better off using it to make, or failing that, buy some at least somewhat up to date gear than mass producing such weapons of desperation.

5) Yes. When did I say otherwise? 76 mm strikes me as the minimum scale to squeeze such a system in as a practical weapon system. At least on the anti orbital. I'm not sure its all that terrible anti-missile. But yes, 76 is a general purpose good enough round. Which is its benefit.

And the whole discussion up to that point was me arguing that it's not really practical, it's a weapon of desperation level of practical. Yes, it is that terribly marginal for such work.
There is a bloody reason why modern armies just don't bother playing with that, even against basic tactical jets, how do you imagine it being worthwhile against 25th century equivalents.

6) yes, the 76 mm guns primary job is like to be ground or low flying aircraft like helicopters and drones. Rocket propelled rounds lets you then squeeze in extra velocity, either for high penetration or range, either in the vertical or or horizontal.

At the price of smaller payload.

A couple of rocket rounds thus dramatically shrinks the absolute safety range for the enemy, and keeps the enemy on their toes, imposing virtual attrition and giving local forces the ability to punish the enemy if they get lazy. If the enemy support asset does stop maneuvering and follows a very predictable standardized path, you have something to shoot at the target.

If that's the only thing keeping them on their toes as opposed to some much better defenses with much higher performance envelope, you are screwed, and they aren't really being kept on their toes. You are talking of using heavy artillery equivalent vehicles (which you also need to support logistically, which is pretty logistics heavy as far as vehicles are concerned) revealing themselves just to mildly annoy enemy support spacecraft. Tell me this isn't the definition of a weapon of desperation.

Point defense probably optimizes for a faster burn than I had for reaching orbit though: the rocket gives something like 2-3 km extra delta v. So, start with initial 800 m/s muzzle velocity, 100 g rocket burn would be 2 seconds of burn, so you've got to something like 3 km/s at roughly 3-4 km. This likely increases danger to aircraft.

Those are also fantasy figures. If RAP shells could get half of this kind of dV we would be using them instead of APFSDS, which normally get up to 1.5-1.8 km\s, also bolters would be a perfectly reasonable IRL weapon. At this proportion of dV from gun and rocket the engineering would get insane, you are forcing yourself to use a huge, cumbersome launch platform to launch a full sized medium range missile out of a cannon, instead of just using a missile rack and slightly longer missiles with much lighter tolerances for shock, acceleration and so on.

 

[JagerIV]

1) Once again, we seem to come to opposite conclusions from the same evidence.
2) This is also irrelevent, but okay.
3)Same evidence, different conclusions, excetera.
4) Digging ditches is different than precession manufacturing.
5) I don't take it as much as a given as you, but at least you seem to have accepted 60s tech is achievable in the far future, rather than some impossibility. This comes down to a setting dependent question of optimization.
6) Sure. But also in a smaller package than a Stinger missile. Doctrine and setting question.
7) Is a Stinger a weapon of desperation? It would seem likely to be so by how you define it. Is it thus pointless? Or are layered defence, combined arms a thing?
8) And were back to saying the achievements of the 1960s is unrepeatable magic. RAPs have a different function. They are thus, shocker, designed differently, using older rocket fuels rather than cutting edge rocket fuels, with tighter cost constraints to have a viable weapon.

Bolters are actually perfectly reasonable weapons. By their generally given stat line, their not even all that impressive. As depicted their dramatically oversized for what they are.

Is your contention Excalibur type guided rounds won't be a thing in the future? If guided artillery rounds are in general a non-entity, then its expense specialized tech. If they do exist, its moderately different use of future military off the shelf technology.

Your back to arguing technology and weapon systems that currently exist, don't exist, and don't have any reason to exist. Maybe in the future all gun artillery will be obsolete and we will only have rocket artillery. That has not occurred yet however, and I would lean to artillery existing in the future.

I just don't understand your insistence the 1950s is the absolute best artillery can be.

 

[Doomsought]

Bolters are actually perfectly reasonable weapons. By their generally given stat line, their not even all that impressive. As depicted their dramatically oversized for what they are.

Gyrogets have issues with muzzle velocity and accuracy.

It is likely for a space based civ to come up with a man portable reconciles riffle with an exhaust port that gets tucked under the armpit for zero-G use.

 

[JagerIV]

Gyrogets have issues with muzzle velocity and accuracy.

It is likely for a space based civ to come up with a man portable reconciles riffle with an exhaust port that gets tucked under the armpit for zero-G use.

60s gyrogets built in a garage had problems with muzzle velocity and accuracy. Important clarification. Its not an issue intrinsic to the technology. Its also true the tech doesn't really have much of a place currently: you don't actually get much benefit getting significantly higher muzzle velocity over current rounds, and a more expensive round to achieve the same muzzle velocity is a bit of a waste: having fired an 5.56 mm gun, you already have extremely light recoil: a more expensive bullet for an even lighter recoil doesn't promise much extra.

Most grenades get the performance they need out of the high-low system, so currently don't need gyrojets, though higher performance grenades could.

The closest actually deployed weapon to Bolter operation I can think of is the Grom:

A small PG-15P powder charge is used to boost the projectile from the gun barrel at 400 metres per second (1,300 ft/s). Once the projectile has travelled 10–20 m (33–66 ft), the rocket motor starts and accelerates it to 700 m/s (2,300 ft/s).

This was admittedly not a particularly stellar weapon. RPG-7 also has something similar I remember.

Hm, recoilless traditionally have the problem of needing a lot of propellant, and historically were heavier than other options, though I don't think that's a rule. Carl Gustaf is not super light, but its not super heavy either.

Not sure the exact trade offs of recoiless vs rocket, but they both seem like they should work pretty well as low recoil systems.

 

[Marduk]

1) Once again, we seem to come to opposite conclusions from the same evidence.

Because for some strange reasons you think primary performance characteristics of long reach AA (as in the long reach and its payload) for tertiary characteristics like munition size and cost to the point of reducing the former to a level barely better than useless, creating a system with at best trace levels of combat effectiveness.

3)Same evidence, different conclusions, excetera.

Except you have no evidence at all. Almost no modern tanks have AA that's useful against modern airpower that's not doing something stupidly ballsy or isn't extra short ranged point defense.

4) Digging ditches is different than precession manufacturing.

We are talking long range artillery, we're way past the point of having decent industrial capability and precision manufacturing, so why the red herring of digging ditches. They would be better off manufacturing future spoons and children's toys with that to buy 2 generations backwards pre-owned ground to orbit lasers than this.

5) I don't take it as much as a given as you, but at least you seem to have accepted 60s tech is achievable in the far future, rather than some impossibility. This comes down to a setting dependent question of optimization.

Possible and combat effective are 2 different things. Just barely reaching the required altitude with minimal payload and with well over a minute of flight time is already of very little utility against modern aircraft, nevermind future aerospace assault craft.

6) Sure. But also in a smaller package than a Stinger missile. Doctrine and setting question.

>package
Here's your problem. Any system involving a cannon is a huge package if you see it as a system, and there is no reason not to.

7) Is a Stinger a weapon of desperation? It would seem likely to be so by how you define it. Is it thus pointless? Or are layered defence, combined arms a thing?

Stinger is actually very good within the parameters of its job. High altitude defense is a job 76mm guns are not considered good at even now, and against future, higher performance craft, nevermind space, they can't possibly be any better than that.
Using a WW2 style 7.62 AAMG to shoot down a low flying tactical jet (aka Stinger's job) is a weapon of desperation, because it's most likely to fail completely.

8) And were back to saying the achievements of the 1960s is unrepeatable magic. RAPs have a different function. They are thus, shocker, designed differently, using older rocket fuels rather than cutting edge rocket fuels, with tighter cost constraints to have a viable weapon.

If you have tighter cost constraints, you don't get cutting edge rocket fuel. If you have cutting edge rocket fuel and it's cheap, why not ditch the whole cannon and make a proper missile system.

Bolters are actually perfectly reasonable weapons. By their generally given stat line, their not even all that impressive. As depicted their dramatically oversized for what they are.

Is your contention Excalibur type guided rounds won't be a thing in the future? If guided artillery rounds are in general a non-entity, then its expense specialized tech. If they do exist, its moderately different use of future military off the shelf technology.

Great, that may be the point you are drawing massively wrong implications out of. Excalibur type guided munitions get their impressive range figures out of tricks like low powered sustainer motors sometimes combined with gliding ability. The problem is gliding ability and aerodynamically optimal speeds are fucking useless for purposes of going up, nevermind going up quickly, which is what air\space defense projectiles need to do.

Your back to arguing technology and weapon systems that currently exist, don't exist, and don't have any reason to exist. Maybe in the future all gun artillery will be obsolete and we will only have rocket artillery. That has not occurred yet however, and I would lean to artillery existing in the future.

I just don't understand your insistence the 1950s is the absolute best artillery can be.

The main US SPG system firing these Excalibur rounds is still the M109, which dates back to Vietnam. The round design and targeting got better since then, but dimnishing returns are absolutely a thing.
The fact is that large caliber AA guns are already pretty much history, and lasers are slowly gunning for the small caliber niche already.

 

[JagerIV]

What does excalibur's range have to do with anything I said? The point of excalibur is "does guided artillery rounds exist"?

If yes, guidance packages for other guided artillery rounds is, repeat after me "off the shelf technology". And not some crippling cost to shells. Because all the other guided artillery round tech for everything else already exists and is being mass produced.

Your contention is that guided artillery shells are some super expensive, impossible technology. My contention is its off the shelf technology of the future, and thus having some additional specialized ammo is a trivial logistical cost. When you have a gun anyway, throwing 5 extra shells for long range fires is a trivial expenditure.

 

[Marduk]

What does excalibur's range have to do with anything I said? The point of excalibur is "does guided artillery rounds exist"?

If yes, guidance packages for other guided artillery rounds is, repeat after me "off the shelf technology". And not some crippling cost to shells. Because all the other guided artillery round tech for everything else already exists and is being mass produced.

So? Guidance packages are not made equal and don't do the same things.

Your contention is that guided artillery shells are some super expensive, impossible technology.

Where the fuck did i say that?

My contention is its off the shelf technology of the future, and thus having some additional specialized ammo is a trivial logistical cost. When you have a gun anyway, throwing 5 extra shells for long range fires is a trivial expenditure.

They are low maneuverability, GPS or laser guided usually. Both methods being useless for hitting aircraft already, nevermind aerospace craft. And even if they had useful guidance, their performance envelope is equally bad for AA work much beyond point defense anyway.
Unless you design some weird shell that's essentially a gun boosted missile. But at that point you may as well get rid of the gun to ease design requirements and get a better, simpler and more mobile system.

 

[Agent23]

Short answer: Space Marines are cool so keep your logic to yourself, everytime you bring logic in a space fantasy debate God kills a cat girl.

Long answer, tech will have to progress for space flight and ships will become increasingly expansive and power armor might become common, as might energy weapons, since those will be improved by related developments, like better materials and denser power sources.

As this happens boarding actions might become necessary, anti-terrorist and anti-piracy activity might become necessary, and gradually we will get something akin to Space Marines.

And eventually, some space bound force will find the need to take moons, asteroids and other hardened installations without causing the equivalent of a nuclear winter on the planet they are on, or turning the terrestrial body or space station into swiss cheese.

As to taking out orbitals from a planet's surface, meh, might work in some situations, like a planetary blockade/siegr, but space based assets will probably do best, since launching stuff into space would require a decent amount of time and energy to hit something in orbit and you are dealing with friction, drag, gravity, the countermeasures will likely see it thousands of miles away.

 

[JagerIV]

So? Guidance packages are not made equal and don't do the same things.

Where the fuck did i say that?

They are low maneuverability, GPS or laser guided usually. Both methods being useless for hitting aircraft already, nevermind aerospace craft. And even if they had useful guidance, their performance envelope is equally bad for AA work much beyond point defense anyway.
Unless you design some weird shell that's essentially a gun boosted missile. But at that point you may as well get rid of the gun to ease design requirements and get a better, simpler and more mobile system.

Are you aware you can have guns and missiles? The trade off your suggesting simply doesn't exist. Its both and, not either or.

Your the one making the argument gun launched rounds, which we have now, are some giant impossible cost which will interfere with better missiles, somehow. When instead they're harmonious technology. Better rocket fuel allows better missiles and better gun launched missiles. Higher G tolerance allows higher acceleration missiles.

Gun launched guided rounds exist, and aren't actually all that expensive. High performance missiles are likely to cost at least as much, and likely more.

Another gun launched rocket added to an existing gun launched rocket system just doesn't offend me in the same way it seems to offend your sensibilities. And your constant back and force over if the future could in fact be more advanced the the 1960s-modern day. If Italy can fund a guided point defense round, I think future space civilizations might be able to squeeze that into the budget. Especially if it was squeezed into the budget 200 years ago.

You know the great thing about being rich? You can afford more stuff and don't have to make as hard trade offs. We are endlessly complaining about a rounding error in the budget. And you were the one who spent endless time arguing the critical importance of solid propellant for its long term storability!

So, if your space America scale polity with a $30 trillion dollar GDP in general peace with 1% defense spending, some $300 billion in annual spending, you spend 1/10th of 1% of your defense spending on 10,000 anti orbit rounds a year, and have your 10 year stockpile of 100,000, so your guard and ships have some increased point defense capability if they need to be dispersed to survive a contested orbit, and you have a round that's not a waste to shoot at an illegal cube sat, and you can afford some more live fire exercises with.

 

[Marduk]

Are you aware you can have guns and missiles? The trade off your suggesting simply doesn't exist. Its both and, not either or.

You can also have guns and missiles alongside ballistae. But what's the bloody point.

Your the one making the argument gun launched rounds, which we have now, are some giant impossible cost which will interfere with better missiles, somehow. When instead they're harmonious technology. Better rocket fuel allows better missiles and better gun launched missiles. Higher G tolerance allows higher acceleration missiles.

Better materials allow us to build better ballistae than ever before right now! You can't deny that...

Gun launched guided rounds exist, and aren't actually all that expensive. High performance missiles are likely to cost at least as much, and likely more.

They are in the same cost region as medium range guided missiles, which is dramatically, 1-2 orders of magnitude higher than unguided artillery. As such, they are seen as a capability expansion for already bought and operated artillery systems, rather than a main way of using tube artillery.
And that's with, as i explained, a lot of potential tricks for extending the horizontal range of artillery that guidance enables (RAPs, nevermind gliding munitions, are notoriously inaccurate at long ranges if unguided) being already weighted in, that are not a factor for anti aerospace role.

Another gun launched rocket added to an existing gun launched rocket system just doesn't offend me in the same way it seems to offend your sensibilities. And your constant back and force over if the future could in fact be more advanced the the 1960s-modern day. If Italy can fund a guided point defense round, I think future space civilizations might be able to squeeze that into the budget. Especially if it was squeezed into the budget 200 years ago.

But why? Why would they resurrect large caliber AA guns at all, when they are already mostly retired, and then invest massive R&D and industrial resources to try give them unlikely and proportionally expensive capabilities of barely any worth in ground to space role.... in the name of what, cheapness?
Point defense guided rounds make far more sense than anti orbit gun assisted missiles- far less complex, and the limited velocity is not much of an issue in point defense role of all things, and that's with it being meant for ships, which need to carry around the gun anyway for non-AA purposes.

You know the great thing about being rich? You can afford more stuff and don't have to make as hard trade offs. We are endlessly complaining about a rounding error in the budget. And you were the one who spent endless time arguing the critical importance of solid propellant for its long term storability!

Well if they are rich, why are they bothering with that kind of desperate, low capability weapon at all? Neither USA nor Saudi Arabia are working on anti-tank ballistae as far as i know.
If anyone is, it's the likes of ISIL, and they aren't using state of art modern materials and engineering for it.

So, if your space America scale polity with a $30 trillion dollar GDP in general peace with 1% defense spending, some $300 billion in annual spending, you spend 1/10th of 1% of your defense spending on 10,000 anti orbit rounds a year, and have your 10 year stockpile of 100,000, so your guard and ships have some increased point defense capability if they need to be dispersed to survive a contested orbit, and you have a round that's not a waste to shoot at an illegal cube sat, and you can afford some more live fire exercises with.

>increased
Here is your critically mistaken assumption. Increased over what? What increase of capability do gun launched missiles offer over proper missiles, nevermind railguns, lasers et al?
Want to shoot at annoying cube sat and other trash targets? Any ground to orbit laser will do the job far better and still far cheaper.
No, their overall capability would be decreased by the need to carry around very expensive in terms of electronics and training, general IADS integrated gun, with all its required size increase in the relevant platforms (big guns have recoil, weight, size, specialized ammo storage etc), for the sake of having an minimal performance ground to orbit weapon, while also presumably carrying proper ground to orbit weapons too, and could carry more of those instead for the same cost.
It's as weird of an idea that you are pushing ridiculously for some ridiculous reason, it's like the idea of mounting a ballista on a tank as a "cheap" secondary weapon.
Which in practice would be mostly pointless and not so cheap at all.

 

[JagerIV]

You can also have guns and missiles alongside ballistae. But what's the bloody point.

Better materials allow us to build better ballistae than ever before right now! You can't deny that...

They are in the same cost region as medium range guided missiles, which is dramatically, 1-2 orders of magnitude higher than unguided artillery. As such, they are seen as a capability expansion for already bought and operated artillery systems, rather than a main way of using tube artillery.
And that's with, as i explained, a lot of potential tricks for extending the horizontal range of artillery that guidance enables (RAPs, nevermind gliding munitions, are notoriously inaccurate at long ranges if unguided) being already weighted in, that are not a factor for anti aerospace role.

But why? Why would they resurrect large caliber AA guns at all, when they are already mostly retired, and then invest massive R&D and industrial resources to try give them unlikely and proportionally expensive capabilities of barely any worth in ground to space role.... in the name of what, cheapness?
Point defense guided rounds make far more sense than anti orbit gun assisted missiles- far less complex, and the limited velocity is not much of an issue in point defense role of all things, and that's with it being meant for ships, which need to carry around the gun anyway for non-AA purposes.

Well if they are rich, why are they bothering with that kind of desperate, low capability weapon at all? Neither USA nor Saudi Arabia are working on anti-tank ballistae as far as i know.
If anyone is, it's the likes of ISIL, and they aren't using state of art modern materials and engineering for it.

>increased
Here is your critically mistaken assumption. Increased over what? What increase of capability do gun launched missiles offer over proper missiles, nevermind railguns, lasers et al?
Want to shoot at annoying cube sat and other trash targets? Any ground to orbit laser will do the job far better and still far cheaper.
No, their overall capability would be decreased by the need to carry around very expensive in terms of electronics and training, general IADS integrated gun, with all its required size increase in the relevant platforms (big guns have recoil, weight, size, specialized ammo storage etc), for the sake of having an minimal performance ground to orbit weapon, while also presumably carrying proper ground to orbit weapons too, and could carry more of those instead for the same cost.
It's as weird of an idea that you are pushing ridiculously for some ridiculous reason, it's like the idea of mounting a ballista on a tank as a "cheap" secondary weapon.
Which in practice would be mostly pointless and not so cheap at all.

1) Ballista's prove - what exactly? You seem to think your making a point, but I'm not seeing it. I already started with "assuming chemical guns aren't obsolete", which I personally don't find likely, but do admit is possible.

2) You keep not believing me when I say the Excalibur's range has zero impact on my analysis. Please stop hallucinating my argument. I've also never argued for this as the primary use of these weapons. Its an add on to existing gun systems to give them a little bit of self defense by adding some specialized shells.

3) Well, I'm not resurrecting anything. the 76 mm is probably the most popular ship gun caliber, and is an AA gun. 127 mm might be the most common naval gun, based on being the primary arment of US Navy destroyers. Gun artillery like the archer is still a thing, which is why it was included in the picture as an example earlier. The larger rounds would be optional specialty rounds for artillery guns. You fire one round and then scoot.

Something more advanced along the lines of the PzH with its rapid burst fire mode might be able to get more than a shot off in the engagement window.

The rounds give your already long range artillery some way to engage space assets and contribute to the planetary defense, either in a non-landing situation or to better engage the enemy while in the process of landing forcing further deployment, at which point you can engage in longer range rocket assisted ground fire. And if your operating on a tight budget, shipping 10 extra special rounds with the artillery you know your going to need may be cheaper than sending a second heavy vehicle for a "might need" situation.

Or general tyranny of location: a planet is big, and your garrison placed in the outback so it can't be taken completely unopposed might not be able to get equipped the best of everything, so it be nice if they had the option to be equipped with something. You need the artillery there so if commandos land you can bring overwhelming firepower, and you give them some anti-orbit rounds so its not completely safe to overfly their location, even if they might need to get initial targeting data from a station in Russia, who then radio them the GPS coordinate and time to fire.

4) Eh, the extra velocity is useful for point defense since shorter response times gives higher chance to hit, or allows further engagement range: its one reason many current point defenses are moving to 35-40 mm rather than the older 20 mm systems, which just don't have much practical range, and why they were trying to get the 76 mm onto a vehicle platform, because smaller caliber guns have woefully insufficient range against missile armed helicopters.

Good high velocity with some guidance expands the high lethality range significantly. For the 76 mm, the anti orbital round takes that existing technology and optimizes it for the limit of its performance. Its still a primarily point defense/anti air weapon though. The 127 and up either get the same range, but a larger warhead (and maybe more substantial guidance) for more deadliness in that limited envelope, or stage to get better range. 10 inch/250 mm was about the upper limit I figured where gun launch systems were plausible: past that your really pushing past the point where guns can reasonably still be kept mobile, and where gunpowder bags may be still giving cost savings vs an actual first stage rocket.

5) Well, as I've explained, its a logical outgrowth of existing technologies to fill a nitch we don't need filled now, but could need in the future, to make use of an existing, widely available weapon system I suspect would likely be widely operational in the future, namely gun artillery. As far as I'm aware, neither the US or Saudi Arabia have thousands of ballista in their inventories currently which could use a logical upgrade to current capabilities. The ballista comparison simply isn't accurate.

US also of course is a bit bad in this comparison because the force is basically designed with the assumption of air superiority. Armies who might find themselves in a situation where their armies aren't guarantied air superiority, let alone space superiority, will have different priorities.

6) If guns in general are opsolete, sure. I find that less plausible, but if you don't have chem artillery in your inventory, it would be silly to have them just for anti orbital use. Secondary back up use is admittedly not good enough to justify use if primary use is not available.

Power density (volume and mass) makes viable laser and railgun systems for mobile systems a big ask, so that getting equal performance to a chem system in a laser/rail mobile system seems very questionable without very high technology, but also not impossible. Reducing back to a question of cost efficiency rather than capability: If you can build a laser fighting vehicle, how much more expensive is that than a gun fighting vehicle vs the additional capacity?

And can the outback garrison in middle of nowherestan keep it functional?

 

[Marduk]

1) Ballista's prove - what exactly? You seem to think your making a point, but I'm not seeing it. I already started with "assuming chemical guns aren't obsolete", which I personally don't find likely, but do admit is possible.

Chemical guns aren't obsolete for very different roles than ground to orbit. Just like prop driven planes aren't obsolete... it's just you won't bring them to fight for air superiority, they are obsolete for that.

2) You keep not believing me when I say the Excalibur's range has zero impact on my analysis. Please stop hallucinating my argument. I've also never argued for this as the primary use of these weapons. Its an add on to existing gun systems to give them a little bit of self defense by adding some specialized shells.

Why would there be existing large caliber AA gun systems in the future? They are considered borderline obsolete already, chiefly due to effective range limitations.

3) Well, I'm not resurrecting anything. the 76 mm is probably the most popular ship gun caliber, and is an AA gun. 127 mm might be the most common naval gun, based on being the primary arment of US Navy destroyers. Gun artillery like the archer is still a thing, which is why it was included in the picture as an example earlier. The larger rounds would be optional specialty rounds for artillery guns. You fire one round and then scoot.

My point exactly, it's popular on *old* ships. Many newer ones go even lower in caliber, new US ships favor the 57mm, like FFG(X). And even that is not really an AA weapon, but a swiss army knife weapon with a secondary point defense weapon function. It's not useful for shooting down enemy jets even.
Land gun artillery didn't get AA integration since the age of jets, and there are reasons for it.
Guns on ships are going into even further multi-role combination of CIWS and "warning shot gun", which is trending towards fast firing 30-60mm calibers.

Something more advanced along the lines of the PzH with its rapid burst fire mode might be able to get more than a shot off in the engagement window.

You don't understand. Beyond few kilometers, even with modern aircraft, there is no engagement window against a mach 2 jet for them. The problem is that by the time the shell reaches the place where the jet should be according to current course calculation, the jet may well decide to slightly change course and be a kilometers away from that point.

The rounds give your already long range artillery some way to engage space assets and contribute to the planetary defense, either in a non-landing situation or to better engage the enemy while in the process of landing forcing further deployment, at which point you can engage in longer range rocket assisted ground fire. And if your operating on a tight budget, shipping 10 extra special rounds with the artillery you know your going to need may be cheaper than sending a second heavy vehicle for a "might need" situation.

And you are still running on the assumption that IADS integration of artillery is free.
We don't even have that now...
And for very good reasons. It would cost a fortune, complicate training, and let's not even get into the electronics and gun laying... And we don't even need some absolutely insane high performance shells for reaching the orbit while at it. They are fucking useless for reaching a jet 15 km high and 30 km away, which would be far easier than what you want.

Or general tyranny of location: a planet is big, and your garrison placed in the outback so it can't be taken completely unopposed might not be able to get equipped the best of everything, so it be nice if they had the option to be equipped with something. You need the artillery there so if commandos land you can bring overwhelming firepower, and you give them some anti-orbit rounds so its not completely safe to overfly their location, even if they might need to get initial targeting data from a station in Russia, who then radio them the GPS coordinate and time to fire.

These anti orbit rounds are near useless for military purposes (might shot down a civilian sat or shuttle with some luck), while the ability to fire them makes the artillery 2x as expensive to build and run. Instead of them, any sane defence analyst will tell them to replace a quarter of the SPGs with self propelled lasers on the same chassis for same cost and massive increase in G2A and G2O capability.

GPS guidance? What the hell? This is useless for AA or ASAT purposes. Hitting a moving truck with that is an art, good fucking luck with anything that flies.

4) Eh, the extra velocity is useful for point defense since shorter response times gives higher chance to hit, or allows further engagement range: its one reason many current point defenses are moving to 35-40 mm rather than the older 20 mm systems, which just don't have much practical range, and why they were trying to get the 76 mm onto a vehicle platform, because smaller caliber guns have woefully insufficient range against missile armed helicopters.

They aren't trying, it was done in the cold war already, and no one wanted it already.

Otomatic - Wikipedia

en.wikipedia.org

It's just not worth it and no one wanted them anymore as missiles got better.
Italians even planned to put it on Centauro chassis, but again, no one wanted to buy it.

Good high velocity with some guidance expands the high lethality range significantly. For the 76 mm, the anti orbital round takes that existing technology and optimizes it for the limit of its performance. Its still a primarily point defense/anti air weapon though. The 127 and up either get the same range, but a larger warhead (and maybe more substantial guidance) for more deadliness in that limited envelope, or stage to get better range. 10 inch/250 mm was about the upper limit I figured where gun launch systems were plausible: past that your really pushing past the point where guns can reasonably still be kept mobile, and where gunpowder bags may be still giving cost savings vs an actual first stage rocket.

Look at the effective range given for the guided 76mm point defense round... It's somewhere in single digit km...
Point defense, yes, anti air, well if enemies fly B-17's, sure. Anti orbit, at this point it's nothing like a 76mm gun we know it, it's a pointlessly gun launched missile.
And no, inflicting extra miniaturization goals on the further, truly expensive stages of the projectile is the opposite of cost savings.

5) Well, as I've explained, its a logical outgrowth of existing technologies to fill a nitch we don't need filled now, but could need in the future, to make use of an existing, widely available weapon system I suspect would likely be widely operational in the future, namely gun artillery. As far as I'm aware, neither the US or Saudi Arabia have thousands of ballista in their inventories currently which could use a logical upgrade to current capabilities. The ballista comparison simply isn't accurate.

As i argue all the time, the devil is in the details. It would be expensive and it wouldn't really work for much. Seriously, if it was feasible to shoot so high with the normal SPG scale guns, rather than beefed up naval ones, imagine the insane range they could get out of firing gliding rounds this high...
There is a reason why these experiments used naval guns, and then made them bigger.

US also of course is a bit bad in this comparison because the force is basically designed with the assumption of air superiority. Armies who might find themselves in a situation where their armies aren't guarantied air superiority, let alone space superiority, will have different priorities.

I'm not talking about the US, the same applies to all the world's armies. Where are the hybrid SPG/AA superguns of Russia, China, or Iran?

6) If guns in general are opsolete, sure. I find that less plausible, but if you don't have chem artillery in your inventory, it would be silly to have them just for anti orbital use. Secondary back up use is admittedly not good enough to justify use if primary use is not available.

We have lots of them now, and we could be using them against much lower performance flying targets, yet we aren't. Do you know even half the reasons why?

Power density (volume and mass) makes viable laser and railgun systems for mobile systems a big ask, so that getting equal performance to a chem system in a laser/rail mobile system seems very questionable without very high technology, but also not impossible.

Not really. A modern tank\SPG chassis already comes with a ~1MW engine by default, it's just a matter of already ongoing conversion to hybrid electric drive to make it available for weapons, plus supercapacitors.

Reducing back to a question of cost efficiency rather than capability: If you can build a laser fighting vehicle, how much more expensive is that than a gun fighting vehicle vs the additional capacity?

And can the outback garrison in middle of nowherestan keep it functional?

In the age of interstellar travel, more than likely. Much like today you may well get an old Mig-21 for less money than a brand new COIN turboprop plane, nevermind cheapest new fighter, and it's still going to be a better fighter.
If push comes to shove, if you can afford to have lots of such fancy artillery shells and fancy electronics in every SPG, you may as well just use all those resources to put more anti-orbit and anti-air missiles on trucks instead. Cheaper than busying SPGs with a role they are bad at distracting them from their main jobs, while delivering far better performance.

 

[JagerIV]

1) If 2022 is considered very old, we just have some radically different definitions. And yes, modern small American ships are being equipped with an evolved 1970 weapon system, which makes it so much more advanced than an evolved 1964 weapon system.

2) Yes, jets are not spacecraft. An aircraft will constantly change velocity unless power is added to maintain its velocity, making its heading unstable. Over short periods (days generally) spacecraft on a current heading will maintain their current heading unless acceleration is applied. These are very different targets.

3) I'm sorry, how does an artillery peace that needs to fire guided rounds anyways at 800 m/s become dramatically more expensive - firing other guided rounds at 800 m/s?

4) Oh look, you quoted the "they were trying" design back at me as proof it didn't exist! Amazing how often you seem to do that.

5) Or its a different job we don't need done now, like I suggested. Just a thought that maybe pointless weapons that couldn't do anything particularly useful under current conditions aren't designed. I know, crazy.

6) See above, as has been pointed out multiple times at this point.

7) Yes, aircraft are different, and guided artillery rounds are cutting edge tech, not generic common tech. We've gone over all this nonsense repeatedly, you pretending we haven't doesn't help your case. Is your plan to just out stuborn me and claim victory by default?

8) Yes, the first easiest step might be coming to practicality soon. I get a feeling though discussing laser tech with you would be as equally pointless as this whole excessive has been.

9) Eh, could be. But, this may be enough bashing of head on a brick wall.

 

[Marduk]

1) If 2022 is considered very old, we just have some radically different definitions. And yes, modern small American ships are being equipped with an evolved 1970 weapon system, which makes it so much more advanced than an evolved 1964 weapon system.

Yeah, Italian... It's an OPV, and Italy makes those guns. I was talking of a trend at the high end of naval air defense, not general use.

2) Yes, jets are not spacecraft. An aircraft will constantly change velocity unless power is added to maintain its velocity, making its heading unstable. Over short periods (days generally) spacecraft on a current heading will maintain their current heading unless acceleration is applied. These are very different targets.

Spacecraft in current civilian use. Civilian airliners also rarely change course and velocity and you could absolutely gank one with a sufficiently big cannon.
Chances are that by the time we have interplanetary invasions, spacecraft will absolutely be doing that too. Especially invasion spacecraft entering atmosphere. If not, they are completely fucked by more capable weapons anyway.

3) I'm sorry, how does an artillery peace that needs to fire guided rounds anyways at 800 m/s become dramatically more expensive - firing other guided rounds at 800 m/s?

Compare the barrel length, maximum elevation, rotation speed and targeting systems of a SPG and SPAAG. You need a major redesign of the turret, internal space for gun to recoil when in very high elevation, different targeting and so on.

4) Oh look, you quoted the "they were trying" design back at me as proof it didn't exist! Amazing how often you seem to do that.

And you as always proceeded to put on the rose tinted glasses and used that to assume that this means it was a great idea. My point is that they made it and no military wanted it...
I'm not arguing that it's physically impossible to build, i'm arguing that it's going to be ineffective at its job and as such no military will want it.

5) Or its a different job we don't need done now, like I suggested. Just a thought that maybe pointless weapons that couldn't do anything particularly useful under current conditions aren't designed. I know, crazy.

Performance wise the ground to orbit job is if anything more challenging. Logically, if it can hit a target on friggin low orbit, hitting anything between here and low orbit is even easier for it. The interception delay and tracking doesn't get any easier for higher altitudes, it only gets worse.

6) See above, as has been pointed out multiple times at this point.

7) Yes, aircraft are different, and guided artillery rounds are cutting edge tech, not generic common tech. We've gone over all this nonsense repeatedly, you pretending we haven't doesn't help your case. Is your plan to just out stuborn me and claim victory by default?

Yes, they are different, it takes a lower performance to intercept them.

8) Yes, the first easiest step might be coming to practicality soon. I get a feeling though discussing laser tech with you would be as equally pointless as this whole excessive has been.

Yes it does show that out of all things, power won't be an issue for ground vehicle based power hog weapons up for at low double digit megawatts. This is a very theoretical point you have chosen to bring up and it is one that is this weak.

 

[JagerIV]

Yeah, Italian... It's an OPV, and Italy makes those guns. I was talking of a trend at the high end of naval air defense, not general use.

1) Spacecraft in current civilian use. Civilian airliners also rarely change course and velocity and you could absolutely gank one with a sufficiently big cannon.
Chances are that by the time we have interplanetary invasions, spacecraft will absolutely be doing that too. Especially invasion spacecraft entering atmosphere. If not, they are completely fucked by more capable weapons anyway.

2) Compare the barrel length, maximum elevation, rotation speed and targeting systems of a SPG and SPAAG. You need a major redesign of the turret, internal space for gun to recoil when in very high elevation, different targeting and so on.

3) And you as always proceeded to put on the rose tinted glasses and used that to assume that this means it was a great idea. My point is that they made it and no military wanted it...
I'm not arguing that it's physically impossible to build, i'm arguing that it's going to be ineffective at its job and as such no military will want it.

4) Performance wise the ground to orbit job is if anything more challenging. Logically, if it can hit a target on friggin low orbit, hitting anything between here and low orbit is even easier for it. The interception delay and tracking doesn't get any easier for higher altitudes, it only gets worse.

Yes, they are different, it takes a lower performance to intercept them.

5) Yes it does show that out of all things, power won't be an issue for ground vehicle based power hog weapons up for at low double digit megawatts. This is a very theoretical point you have chosen to bring up and it is one that is this weak.

1) I'm talking about a fundamental difference. If the engine of an aircraft turns off, it falls out of the sky. If a spacecraft engine is off, it mostly follows the same orbit on a almost completely predictable path (some gravitational/drag perturbations, but order of magnitudes less than atmosphere).

2) Not really, but I know you don't believe the low capacity rounds I'm talking about can do anything. Increasing the capacity over what I'm talking about and then using your increased capacity rounds higher requirements as an argument against mine is annoying.

3) Considering we do have new weapon systems with them being installed, the idea that their completely obsolete, if marginal, weapon system seems wrong to me, but I've always said from the beginning that its quite possible the gun might be a generally obsolete weapon in the future.

4) Not necessarily, for the fundamentally different kind of target an orbital target is. Planes in atmosphere have many reasons for being an inherently more agile tech. Intercepting in low atmosphere also puts in a lot of drag losses, which dramatically lower ranges.

Once you get over the thick atmosphere, your range for a given delta v goes up a lot. Remember from my earlier 88 flak video that absent atmospheric drag, the 88 would have a range of 69 km, compared to its actual range with atmospheric drag of roughly 14 km. Your down to about 10% atmosphere 18 km, 1% atmospheric density by 30 km, so any delta v expended that high is going to give you much more range than intuitions for lower level high drag situations suggest. For comparison, civil aircraft generally fly about 10 km up, F-16 has a listed ceiling 18 km, and blackbird tops off at 26 km.

But, in general I agree, being able to hitting targets in low orbit, especially an actively maneuvering targets, does imply some ability to better hit closer targets too. I've never been the one who's argued things can't be more advanced in the future. For example, cutting edge guided rounds may over time become increasingly common rounds, or at least some of the guided tech for high performance guided rounds like excalibur could be used to make "common" rounds more effective.

5) Ah, I see the confusion: when I said the power to weight of the Laser/railgun system, you interpreted that as meaning the power to weight of the electricity generator, instead of the whole laser/railgun system.

Lets take as given we have a mobile electric generator with a power to weight of 1 MW/ton.

We want a 1 MW Laser system.

Lets say the Laser optics and laser generator has a power density of 5 MW/ton, so we have only 1 tons of optics. Nice. It has a 20% efficiency, so to output 1 MW, we need 5 MW electricity production. So, we also need 5 tons of electric production. Laser efficiencies are very sensitive to temperature as well. So, we need to at least get rid of 4 MW of waste heat. If we need to refrigerate bellow ambient temperature for optimal operation, you need an even bigger refrigeration system. I don't know the power to weight of refrigeration tech in general, so I'll just assume 4 MW/ton for ease of a nice round 1 ton.

So, these critical parts of the system, laser, generator, refrigerator, gives a total system weight of 7 tons, for an overall power to weight of 0.14 MW/ton. As a point of comparison, a Vulcan Cannon shoots 100 20mm rounds a second with an energy of roughly 50 KJ, so its energy output is 5 MW in a 112 kg system, or a power to weight of 44 MW/ton. Taking the entire M163 Vulcan equiped vehicle, you still get an overall vehicle power to weight with its weapon of 0.4 MW/ton for the 12.5 ton vehicle. If the laser vehicle has an overall power to weight of 0.05 MW/ton, a 1 MW system would be 20 tons. A 5 MW system would be 100 tons.

Refrigeration and laser optics also tend to not be particularly dense, since both require quite a bit of open space to work. So a 20 ton laser vehicle is likely to require a much physically larger vehicle than an M113.

Hopefully that clears up the confusion.

 

[Marduk]

1) I'm talking about a fundamental difference. If the engine of an aircraft turns off, it falls out of the sky. If a spacecraft engine is off, it mostly follows the same orbit on a almost completely predictable path (some gravitational/drag perturbations, but order of magnitudes less than atmosphere).

So? Just because it can do it, doesn't mean it's a wise idea to do it while invading a hostile planet. Just like tactical jets in a war don't fly using the same economically efficient altitudes and speeds commercial airliners do.

2) Not really, but I know you don't believe the low capacity rounds I'm talking about can do anything. Increasing the capacity over what I'm talking about and then using your increased capacity rounds higher requirements as an argument against mine is annoying.

No one cares if they can do *anything*. The question is, can they do anything worthwhile, as in combat effective? "just barely threatening enemy craft of minimal theoretical performance" is an "anything" but doesn't count as "combat effective" for example.

3) Considering we do have new weapon systems with them being installed, the idea that their completely obsolete, if marginal, weapon system seems wrong to me, but I've always said from the beginning that its quite possible the gun might be a generally obsolete weapon in the future.

>new
Technically new, technologically not exactly bleeding edge. The bleeding edge ones don't do that, that was my point.

4) Not necessarily, for the fundamentally different kind of target an orbital target is. Planes in atmosphere have many reasons for being an inherently more agile tech. Intercepting in low atmosphere also puts in a lot of drag losses, which dramatically lower ranges.

When invading planets becomes a thing, the spacecraft meant for it will need to be able to deal with far more dangerous weapons, which is why i'm so skeptical of weapons of marginal capacity to engage them at all.
Also any gun firing into space will absolutely need to shoot through the equivalent of at minimum a medium range missile's maximum range through atmosphere already, so guns have to it either way.

Once you get over the thick atmosphere, your range for a given delta v goes up a lot. Remember from my earlier 88 flak video that absent atmospheric drag, the 88 would have a range of 69 km, compared to its actual range with atmospheric drag of roughly 14 km. Your down to about 10% atmosphere 18 km, 1% atmospheric density by 30 km, so any delta v expended that high is going to give you much more range than intuitions for lower level high drag situations suggest. For comparison, civil aircraft generally fly about 10 km up, F-16 has a listed ceiling 18 km, and blackbird tops off at 26 km.

Yeah, sure... but the round has to get through it anyway, and then you need an essentially gun hardened missile to do any further intercepting, guiding and maneuvering.

But, in general I agree, being able to hitting targets in low orbit, especially an actively maneuvering targets, does imply some ability to better hit closer targets too. I've never been the one who's argued things can't be more advanced in the future. For example, cutting edge guided rounds may over time become increasingly common rounds, or at least some of the guided tech for high performance guided rounds like excalibur could be used to make "common" rounds more effective.

What you are implying here is that guided rounds will become the common rounds, which requires massive improvements in the manufacturing economics. But that kind of advances will apply the same way to missiles.

5) Ah, I see the confusion: when I said the power to weight of the Laser/railgun system, you interpreted that as meaning the power to weight of the electricity generator, instead of the whole laser/railgun system.

Lets take as given we have a mobile electric generator with a power to weight of 1 MW/ton.

We want a 1 MW Laser system.

Lets say the Laser optics and laser generator has a power density of 5 MW/ton, so we have only 1 tons of optics. Nice. It has a 20% efficiency, so to output 1 MW, we need 5 MW electricity production. So, we also need 5 tons of electric production.

No we don't. Bad theoretical engineering math. In practice, the laser will not be firing for hours non-stop, so it doesn't need the power supply to allow that. You don't need that. You may prefer, for example, 300 MJ worth of battery or supercapacitor that can be filled by the vehicle's hybrid drivetrain when not firing. Even existing supercapacitors reach 0.03 MJ/kg, which gives us a 30 MJ/ton, or a 10 ton supercapacitor bank. Too much for a M113 but that's not a heavy artillery chassis either. Perfectly fine for a MBT based chassis, which is something many modern SPGs use.

Laser efficiencies are very sensitive to temperature as well. So, we need to at least get rid of 4 MW of waste heat. If we need to refrigerate bellow ambient temperature for optimal operation, you need an even bigger refrigeration system. I don't know the power to weight of refrigeration tech in general, so I'll just assume 4 MW/ton for ease of a nice round 1 ton.

So, these critical parts of the system, laser, generator, refrigerator, gives a total system weight of 7 tons, for an overall power to weight of 0.14 MW/ton. As a point of comparison, a Vulcan Cannon shoots 100 20mm rounds a second with an energy of roughly 50 KJ, so its energy output is 5 MW in a 112 kg system, or a power to weight of 44 MW/ton. Taking the entire M163 Vulcan equiped vehicle, you still get an overall vehicle power to weight with its weapon of 0.4 MW/ton for the 12.5 ton vehicle. If the laser vehicle has an overall power to weight of 0.05 MW/ton, a 1 MW system would be 20 tons. A 5 MW system would be 100 tons.

More terrible theory to circumvent practical common sense. No one cares about the total energy output of gun based systems due to their specializations completely overriding the value of it and scaling being also dictated by such. The same Vulcan cannon will also have far better "energy output" than a tank's 120mm smoothbore, but no one will care, because it can't do the job of one no matter what, like piercing another MBT's front armor, even if it blasts its whole ammo load at it. A 12 ga automatic shotgun also has massively bigger "energy output" than a 7.62 NATO sniper rifle, but we all know which has more reach and better anti armor performance at the same time. For reaching and "touching" spacecraft, the accuracy, delay, reach and engagement range are far more relevant than energy output, and in half of these qualities you can't beat lightspeed.

Refrigeration and laser optics also tend to not be particularly dense, since both require quite a bit of open space to work. So a 20 ton laser vehicle is likely to require a much physically larger vehicle than an M113.

Hopefully that clears up the confusion.

A gun that reaches orbit will be unlikely to fit on a MBT chassis, nevermind a M113 (in fact even the 76mm SPAAG mentioned before is on a MBT chassis).
If cooling becomes that much of an issue, wouldn't be surprised if the heavy anti-aerospace vehicles would use something like liquid nitrogen tanker trucks as their equivalent of ammo resupply.

 

[JagerIV]

Eh, I think we've beat the anti orbital round to death. I think the important agreement is that they are actually possible, then its a setting question of it their cost effective/have a roll. So we can move on to discussing that. I'll just re-iterate I think your overestimating the cost difference between gun launched and missile launched: hardning the hardware to survive artillery rounds does not seem to be a primary driver of costs in such systems, and in the future such hardware is likely centuries old tech, not cutting edge this generation (some 70s-80s systems, admittedly) tech. Its something every advanced economy will likely have the ability to trivially do. The question will come down to usefulness, not possibility.

As to lasers, I didn't realize we were getting such good super capacitors. Generally I've seen capacitors had worse power to weight than generators, so for a given power need having an overpowered turbine was better power to weight than batteries/capacitors. But if they are getting better, it does make the tech a bit more viable. I've never questioned the possibility of them being viable weapons.

Well, the point was power density, so its not irrelevant. If the weapon system gets better "efficiency" for its power output is a different question, which I would assume so if its worth using. And as a slight tangent, within the second of firing, you have roughly equivalent MW output, and of course in the moment of firing 1 round vs another, you have 120x energy output. For roughly equivalent mass gain too.

Its useful approximation for getting a rough sense of how heavy a weapon you need for a given energy output. For raw energy density, laser or railguns are going to have a very hard time matching chemical energy density. But, like your suggesting, if they can get more efficiency out of that energy output, so they need less energy to achieve the same job, that minimizes many of the costs.

 

[Marduk]

Eh, I think we've beat the anti orbital round to death. I think the important agreement is that they are actually possible, then its a setting question of it their cost effective/have a roll.

We have established that is is *technically* barely possible, which translates to shite performance skirting the line of combat effectiveness in fairly bulky and not so cheap form.
A weapon of desperation if anyone would use it at all, rather than something to be perfected, mass and stockpiled in peacetime.

So we can move on to discussing that. I'll just re-iterate I think your overestimating the cost difference between gun launched and missile launched: hardning the hardware to survive artillery rounds does not seem to be a primary driver of costs in such systems, and in the future such hardware is likely centuries old tech, not cutting edge this generation (some 70s-80s systems, admittedly) tech. Its something every advanced economy will likely have the ability to trivially do. The question will come down to usefulness, not possibility.

It makes them cost way more than similarly guided, overall bigger and more powerful JDAM. Let that sink in. And it's moot for AA purposes because GPS guidance is utterly useless for that. The 76mm AA guided one uses fucking RC guidance, which is generally considered a no good in modern missiles anymore, though the low range minimizes the problems with it. Where are the radar or IR guided (which are more expensive and complex) shells?

As to lasers, I didn't realize we were getting such good super capacitors. Generally I've seen capacitors had worse power to weight than generators, so for a given power need having an overpowered turbine was better power to weight than batteries/capacitors. But if they are getting better, it does make the tech a bit more viable. I've never questioned the possibility of them being viable weapons.

Well, the point was power density, so its not irrelevant. If the weapon system gets better "efficiency" for its power output is a different question, which I would assume so if its worth using. And as a slight tangent, within the second of firing, you have roughly equivalent MW output, and of course in the moment of firing 1 round vs another, you have 120x energy output. For roughly equivalent mass gain too.

If other factors change the efficiency of transferring the "power output" to the most important performance characteristics by orders of magnitude, well, it's kind of a useless statistic to measure for comparison purposes.

Its useful approximation for getting a rough sense of how heavy a weapon you need for a given energy output. For raw energy density, laser or railguns are going to have a very hard time matching chemical energy density. But, like your suggesting, if they can get more efficiency out of that energy output, so they need less energy to achieve the same job, that minimizes many of the costs.

It's an extremely inaccurate comparison for purpose of judging or comparing effectiveness, which as i've shown in the example, gets really bad even in apple to apple comparison to other guns.

 

[JagerIV]

Agree to disagree on all the above.

 

[JagerIV]

To pull back to the bigger picture, I'll try summarizing some of my thoughts on ground forces.

1) Ground assets are likely cheaper than space assets.

To be useful, space assets have to have longer range and accuracy than a ground asset. A modern tank gun is extremely accurate over a 1-2 km range. An accuracy of 100,000 nanoradians gives a spread at 2 km of roughly 0.2 m. The same accuracy over a 100 km gives a spread of 10 meters, 1,000 km 100 meters.

An order of magnitude in improved accuracy/range likely implies more than an order of magnitude increase in cost (depending on the exact cost curve).

2) Holding and controlling territory with air assets alone is very difficult/impossible, space generally increases all those problems: much higher minimum useful accuracy, longer range, shorter time over target, observation difficulties, likely comparatively high upkeep/sustainment costs and thus also high logistical cost, high unit cost which leads to lower number of units available/increased difficulty of replacement, which further makes attrition costs extreme.

3) Combined arms is a thing, and I believe would still be a thing in space. For example, dispersion, high mobility, and heavy fortifications are all effective mitigating the effective firepower of space. Heavy dispersion however makes the enemy weaker at resisting ground forces, and some types of cover that may hide a target against distant space targets may be dramatically less effective against surface level scouting, and having to protect against orbital bombardment and infantry/armor dramatically increases the complexity of fortifications and raises the minimum viable scale of a mobile units: it would be quite unpleasant to lose an expensive anti orbital system to a commando with a demolition charge, but adding a IFV with infantry to guard every such platform likely represents a large increase in logistic consumption and makes a larger vehicle group, increasing chance of detection.

Now, some of the immediate counter arguments, and why I think they may be relatively limited.

1) Orbital superiority: The classic argument that who has the high ground wins. That once the space battle is over, the surface might as well surrender due to their compete helplessness. I obviously disagree with this.

a) If both the space and planetary forces are on equal technological footing, they likely have roughly equivalent range and accuracy: if a space weapon can accurately engage a surface target at x range, a surface vehicle likely has comparable range against a space target. While there would be some variations dependent upon the specific technology, for the same tech level I would expect a degree of completeness between space and surface assets, rather than crushing advantage one way or the other.

b) If anything, I expect a degree of superiority to surface assets, due to their grounded nature: easier to hide, less dependent on high tech for basic functionality (a space cruiser may be 10% by mass advanced weapons and 40% advanced engines to maneuver: a space cruiser can just be 10% advanced weapons, so for the same "advanced tech" budget you can equip 3-5 cruisers, built out of cheaper materials because saving every gram is not as critical. Or you can power laser batteries off the general grid and move equipment by truck/train/barge, requiring less tight and exacting weight optimization.

Generally, something along the lines of a defenders advantage. Tactics, doctrine, and details of the tech will swing the specifics, but for relatively equivalent investments space having the decisive advantage on its own seems unlikely to me.

c) Even with complete orbital superiority, that seems likely to push enemy ground forces directly to a guerilla campaign, which will require a ground forces anyways. If Orbitals can't be contested, that suggests the correct response is to not contest them: Don't defend what can't be defended, instead focus on force preservation and try to stretch the enemy thin. If the enemy for example wanted to conquer Texas for oil production because the broader campaign their fighting requires oil, don't seriously contest the conquest of Texas, certainly not to the degree of overly sacrificing forces for it, but let them go in, preserve your own people and infrastructure as much as you can, and pull back to the limit of their logistical ability.

Getting a perimeter around those big oil producers around Texas is about a 5,000 km perimeter, with an interior of roughly 2 million km^2. If they're deploying an army of 1-2 million men, that's likely something like the limit if you can maintain an army in being capable of at least threatening and harassing that perimeter (with the enemy having orbital superiority, decisive breakthroughs are probably less likely, and just highly risky). You can keep the enemy control limited and in a position to be atritted, while preserving a lot of your people and infrastructure.

Exactly how this is carried out is of course setting dependent, and probably more viable the more politically complex the situation is. Invading Space Afghanistan is complicated if the Taliban can set up a government in exile in space Pakistan a system over, from which they can lobby other powers and smuggle weapons and general support to the resistance. Even more complicated if the space Pakistan is in the same system, or on the same planet . . .

d) Combined arms I think does make the forces more effective: Space and ground forces are likely more effective together than each alone. This is important in any resource constrained situation: If you can afford to just have space cruisers zapping bunkers as identified for 10 years, then you don't need to bother. But if you have senators questioning the progress of the campaign compared to its expense? Or your in a situation where winning in the orbital of this planet doesn't mean the enemy fleet is destroyed: maybe the enemy Admiral could also do the math and knew his chance of victory was low, so gave up the orbital without a fight and withdrew to some asteroid naval fortresses to also carry out space guerilla war/wait for a favorable opportunity.

This mean you want to secure the planet more thoroughly, because if you do weaken the space force to chase the enemy fleet or move onto another target, if there are significant reserves on the planet, they might be able to inflict serious casualties on the garrison force, or if the enemy is able to move a relief space force, your ships will be caught between the planets firepower and the relief forces.

2) Transporting is expensive in space, and an invasion force is too heavy.

Invading a planet, especially a heavily populated one, is a huge undertaking, and with current space costs completely infeasible. I have two main counterpoints:

a) Its not necessarily all that much in the grand scheme of things. Lets say 1 million man force, equipped with 10 tons of equipment per man, a fairly heavy level of supply, so 10 million tons. That is quite a lot of mass. However, in comparison the US navy has roughly 4.6 million tons of displacement, and would be a pretty small fleet compared to world conquering. Earth's total civilian fleet transport capacity in 2022 had roughly 2.2 billion tons of cargo capacity. If the future space empire had as much space logistical capacity as we currently have navally on earth, and those craft only made 1 trip a year, moving 1 million man army would represent 0.45% of the merchant marine capacity. If they're averaging monthly trips, 2.2 billion tons of cargo represents the ability to move 26.4 billion tons per year.

In that case, moving a force to invade earth at the optimal occupation rate of 1 soldier per 40, so for our 8 billion man planet a force of 200 million men, with 10 tons of equipment per soldier for 2 billion tons transported, represents some 7.6% of cargo capacity. Not a trivial ask, but not a crippling one either. Maybe to appease the shipping companies the burden can be lowered by determining conquering earth is a 4 year campaign, not a 1 year campaign, so they only need to deliver 1 million men a week to the surface, and the civilian fleet only needs to commit 1.9% of their annual output to the campaign.

And all cost benefit analysis has to of course be "compared to what?" Maintaining a fleet in combat is also unlikely to be a logistically cheap operation either: Say your fleet had a loaded mass of 10 million tons, "only" roughly twice America's navy weight. Spaceships are quite fuel hogs under almost all plausible tech, but lets say they only consume 1% of their mass per day of operation in fuel and other consumables on average. That still means the fleet is consuming 100,000 tons of material per day. In a year of operation that's a good 36.5 million tons.

A ground campaign is quite logistically intensive, but an orbital campaign is also likely to be quite logistically intensive. And forces on a planet can "live off the land" to a degree ships in the void of space can't. Though obviously securing other, easier targets to give some ability to live off the land to the battleships would be quite useful too.

3) Landing is overly dangerous and difficult: between the effectiveness of defense, the specialized vehicles, and other concerns, actually carrying out a landing against a defended planet is hideously expensive and unlikely to suceed: the last 300 km (or 300,000km, depending on where the defensive envelop starts), is a killing zone you can't plausibly land an invasion force through in any condition to fight.

This is the issue I am the least confident in, and I can see the logic of it. I still think ground troops can make through, in sufficient numbers sufficiently in tact, but also see there are some plausible tech assumptions where this is not the case. I think its less likely, but can't certainly rule it out.

This last one may be worth further thought and clarification, but this is long enough as it is. Really meant to get something more bullet point out than this turned into. Something for another day.