Mk16G = 12" / 50 mark 8 naval gun or 8"/55 RF Mark 16

TFLYTSNBN wrote:BB guns could have much higher muzzle velocity without any exotic technology. They do not because increased air resistance which scales with velocity​ squared reduces the range so profoundly that it is not worth the increased propellent charge and barrel wear.

The theoretical range of a 16" AP from an Iowa is 62 km.
Actual range is 42 km.

Given reduced atmospheric density and increased pressure gradient, actual range would be closer to theoretical. Double gravity reduces range but that can be compensated for with a sqrt(2) increase in muzzle velocity. Saboted rounds with better aerodynamic shape could yield 100 km range easily.

High gravity planet would be bigger so range to the horizon is greater. Ship mounted radar can handle fire control. Flight time is about the same so hit percentage should remain about 2%.

Though a saboted round implies that it's a smaller shell. You could keep the mass the same by using denser metals (tungsten or depleted uranium) but the smaller shell volume still implies a smaller bursting charge so your post penetration effects are going to be reduced compared to the historic Mark 8 Super Heavy shell.

So there are definite tradeoffs to going with a saboted round for longer anti-ship range. (Plus of course the longer range brings with it, in unguided rounds, the magnified issues of fire control prediction and dispersion of your shots. A round that would be 50 yards off the aim point at 40 km would probably be 125 yards off at 100 km because the longer distance lets the smaller errors in pointing accumulate more - so your patterns are almost guaranteed to be less concentrated.

So I'm not sure where the tradeoffs you have to make to get ever increasing range stop being worth it.

TFLYTSNBN wrote:SNIP
High gravity planet would be bigger so range to the horizon is greater. Ship mounted radar can handle fire control. Flight time is about the same so hit percentage should remain about 2%.

not necessarily true - depends on overall density. Having said that I'm not familiar enough with current planetary formation theory to know if there is some upper limit on the density of earth like entities.

Obviously, you have never had the privilege of watching a 120mm tank cannon fire a APFSDS round then examine the target. You could easily have an 8 inch diameter x 6 foot long, fin stabilized spear that will ream BB deck armor in a plunging trajectory. Explosive bursting charge irrelevant.

Jonathan_S wrote:

TFLYTSNBN wrote:BB guns could have much higher muzzle velocity without any exotic technology. They do not because increased air resistance which scales with velocity​ squared reduces the range so profoundly that it is not worth the increased propellent charge and barrel wear.

The theoretical range of a 16" AP from an Iowa is 62 km.
Actual range is 42 km.

Given reduced atmospheric density and increased pressure gradient, actual range would be closer to theoretical. Double gravity reduces range but that can be compensated for with a sqrt(2) increase in muzzle velocity. Saboted rounds with better aerodynamic shape could yield 100 km range easily.

High gravity planet would be bigger so range to the horizon is greater. Ship mounted radar can handle fire control. Flight time is about the same so hit percentage should remain about 2%.

Though a saboted round implies that it's a smaller shell. You could keep the mass the same by using denser metals (tungsten or depleted uranium) but the smaller shell volume still implies a smaller bursting charge so your post penetration effects are going to be reduced compared to the historic Mark 8 Super Heavy shell.

So there are definite tradeoffs to going with a saboted round for longer anti-ship range. (Plus of course the longer range brings with it, in unguided rounds, the magnified issues of fire control prediction and dispersion of your shots. A round that would be 50 yards off the aim point at 40 km would probably be 125 yards off at 100 km because the longer distance lets the smaller errors in pointing accumulate more - so your patterns are almost guaranteed to be less concentrated.

So I'm not sure where the tradeoffs you have to make to get ever increasing range stop being worth it.

isaac_newton wrote:

TFLYTSNBN wrote:SNIP
High gravity planet would be bigger so range to the horizon is greater. Ship mounted radar can handle fire control. Flight time is about the same so hit percentage should remain about 2%.

not necessarily true - depends on overall density. Having said that I'm not familiar enough with current planetary formation theory to know if there is some upper limit on the density of earth like entities.

Yes.

A hypothetical 2 gee planet might be not quite so much bigger but denser.

TFLYTSNBN wrote:Obviously, you have never had the privilege of watching a 120mm tank cannon fire a APFSDS round then examine the target. You could easily have an 8 inch diameter x 6 foot long, fin stabilized spear that will ream BB deck armor in a plunging trajectory. Explosive bursting charge irrelevant.

Tanks are relatively compact targets full of fragile, burnable and/or explosive things. A long rod penetrator or a heat round that penetrates the hull will usually find something critical to break.

In comparison ships are vast airy castles full of lots of much less immediately critical bits (bunks and heads, passageways, food stores, etc, etc.

And part of the reason that long rod penetrators are so damaging to tanks is that they tend to fragment and spray the interior with lots of almost molten, very fast, shards that ricochet around the whole interior - not entirely dissimilar to a gods own fiery shotgun. But against a very large compartmentalized target like a battleship that translates into a lot of damage to the first compartment they hit but very little carry through deeper into the ship. (And battleship designers try to keep as much of the vitals as possible as far away from the desk and sides as possible.

Scale a 120mm M829A2's 27mm diameter penetrator up to a 16" (406mm) gun[1] 91.35 mm (~3.6" diameter) penetrator. Punching a 3.6" hole (followed by highly energetic fragments into a random spot on a battleship, even at over 1000 m/s is unlikely to do critical damage.

Now if you can close the range to perform direct fire and take precision shots into it's turrets that's quite possible a different matter. But you're not sniping like that from 40+ km out.

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[1] And ignore problems like fin stablization and rifling are good mixes.

Jonathan_S wrote:Scale a 120mm M829A2's 27mm diameter penetrator up to a 16" (406mm) gun[1] 91.35 mm (~3.6" diameter) penetrator. Punching a 3.6" hole (followed by highly energetic fragments into a random spot on a battleship, even at over 1000 m/s is unlikely to do critical damage.

Now if you can close the range to perform direct fire and take precision shots into it's turrets that's quite possible a different matter. But you're not sniping like that from 40+ km out.

----------------
[1] And ignore problems like fin stablization and rifling are good mixes.

There are few places where a few hundred pounds of burning depleted uranium scattered through the next few decks won't cause some fairly serious issues.

I've been told that with a tank, penetration by a long rod penetrator tends to remove the crew out via several inch diameter exit hole.

kzt wrote:

Jonathan_S wrote:Scale a 120mm M829A2's 27mm diameter penetrator up to a 16" (406mm) gun[1] 91.35 mm (~3.6" diameter) penetrator. Punching a 3.6" hole (followed by highly energetic fragments into a random spot on a battleship, even at over 1000 m/s is unlikely to do critical damage.

Now if you can close the range to perform direct fire and take precision shots into it's turrets that's quite possible a different matter. But you're not sniping like that from 40+ km out.

----------------
[1] And ignore problems like fin stablization and rifling are good mixes.

There are few places where a few hundred pounds of burning depleted uranium scattered through the next few decks won't cause some fairly serious issues.

I've been told that with a tank, penetration by a long rod penetrator tends to remove the crew out via several inch diameter exit hole.

Look at the periodic table. Actenides are explosively flammable. Burster charge irrelevant.

There should, in principle, be an upper limit on density for a rocky planet. I have no idea what, I'm afraid, but it would be related to the fact that greatly exceeding the mean density of the earth would mean adding significant quantities of the very heavy non-volatile elements, which aren't in great abundance to start with. And also means adding a lot of radioactives to the mix, which turns into a lot more internal heat generation. At some point that heat will affect density by thermal expansion and eventually by making solid surface formation impossible but that's a separate issue, although probably easier to calculate if you start from an arbitrary composition. Off the top of my head, I doubt that it's physically possible to double the mean density of the earth without changing the radius, which is what it would take to get a 2g surface gravity.

For a constant density, surface gravity scales with radius, since mass is proportional to radius cubed while g is inversely proportional to radius squared. A 2g planet with the same bulk composition as the earth would be twice the radius and 8 times the mass. That would have some interesting effects on geology and tectonics, BTW.

TFLYTSNBN wrote:SNIP
High gravity planet would be bigger so range to the horizon is greater. Ship mounted radar can handle fire control. Flight time is about the same so hit percentage should remain about 2%.

TFLYTSNBN wrote:

isaac_newton wrote:
not necessarily true - depends on overall density. Having said that I'm not familiar enough with current planetary formation theory to know if there is some upper limit on the density of earth like entities.

Yes.

A hypothetical 2 gee planet might be not quite so much bigger but denser.

You can dramatically increase the AVERAGE density of a rocky planet simply by making the very dense core larger relative to the diameter of the planet. The thicknes, composition snd density of the crust and mantle could remain unchanged.

TFLYTSNBN wrote:You can dramatically increase the AVERAGE density of a rocky planet simply by making the very dense core larger relative to the diameter of the planet. The thicknes, composition snd density of the crust and mantle could remain unchanged.

Of course this rather ignores how we think planets are formed to begin with. Its rather miraculous, according to our guesstimate of planet formation if you think about it, that there is ANY element floating around a solar system denser than IRON to begin with.

Or, it just shows we don't know what the Hell we are talking about regarding solar systems and planet formation. <<Highly likely>>