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

Well, the power required for a level flight can be approximated as:
P = sqrt (3.33*M^3*g^3/ρ*S*F^2)

where:
P = power in Watts
M = plane's mass in (kg)
g = planet's gravitational acceleration (m/s^2)
ρ = air density (kg/m^3)
S = wing area (m^2)
F = finesse (dimensionless: 5-25 for birds, 16 for a 747, 40-60 for advanced sailplanes)

See that doubling the planet's gravitational acceleration
increases the required power by 2.8, while doubling the planet's air density decreases the required power by 1.4.[/quote]

Very good!
What happens if you double gravity but decrease the air density by half?

Even increasing gravity by 50% while decreasing air density by 50% makes high performance aircraft far less feasible.

Even jet engines give you less thrust.

Propellers and turbofans needed and the best you can hope for with 20th century technology is low performance observation planes.

Meanwhile the Battleships are getting rapid fire 3" guns with proximity fused projectiles to ensure that any silly aircraft stupid enough to attack is dead meat.

Oh, did I mention that thinner atmosphere with higher pressure gradient results in 16" guns having much greater range? Saboted projectiles at 1600 m/s have even greater range. Imgine the battle of Midway fought at the same ranges but with battleships using radar on blimps for fire control.

The whole equation is moot with counter-grav

runsforcelery wrote:

TFLYTSNBN wrote:Ever consider how warship designs might continued to evolve on a planet with a thinner atmosphere and may be higher gravity which would reduce the viability of aircraft?

I actually have the outline for an entire series where that's the case <he said in a small voice>.

Is this one of the ten series you proposed a few decades ago?

Hegemon wrote: Well, the power required for a level flight can be approximated as:
P = sqrt (3.33*M^3*g^3/ρ*S*F^2)

where:
P = power in Watts
M = plane's mass in (kg)
g = planet's gravitational acceleration (m/s^2)
ρ = air density (kg/m^3)
S = wing area (m^2)
F = finesse (dimensionless: 5-25 for birds, 16 for a 747, 40-60 for advanced sailplanes)

See that doubling the planet's gravitational acceleration
increases the required power by 2.8, while doubling the planet's air density decreases the required power by 1.4.

TFLYTSNBN wrote:Very good!
What happens if you double gravity but decrease the air density by half?

Even increasing gravity by 50% while decreasing air density by 50% makes high performance aircraft far less feasible.

Even jet engines give you less thrust.

Propellers and turbofans needed and the best you can hope for with 20th century technology is low performance observation planes.

Meanwhile the Battleships are getting rapid fire 3" guns with proximity fused projectiles to ensure that any silly aircraft stupid enough to attack is dead meat.

Oh, did I mention that thinner atmosphere with higher pressure gradient results in 16" guns having much greater range? Saboted projectiles at 1600 m/s have even greater range. Imgine the battle of Midway fought at the same ranges but with battleships using radar on blimps for fire control.

But air density and gravity are not completely independent quantities; you can decrease the air density for a given gravity force only by decreasing the total amount of air in the atmosphere. Assuming people breathing an oxygen - nitrogen atmosphere for metabolism, then decreasing air and increasing gravity decreases the ability to work or even think. Meanwhile everyone needs to cover up or use SPF 500 else the ultraviolet will get you.

TFLYTSNBN wrote:Oh, did I mention that thinner atmosphere with higher pressure gradient results in 16" guns having much greater range? Saboted projectiles at 1600 m/s have even greater range. Imgine the battle of Midway fought at the same ranges but with battleships using radar on blimps for fire control.

Hmm. lets do some number crunching.
Assume double gravity, and what the heck 50% higher muzzle velocity on the 16" armor piercing shells (so 1143 mps).

To get a quick ballpark I found a javascript ballistic calculator online and I doubled it's gravity acceleration value. It seems to ignore air resistance, but it says a shell fired at 1143 mps at a 45 degree angle, in double gravity will have a range of 66,587 meters (about 41 miles) with a time of flight of 82.3 seconds.

One issue, even with blimp radar spotting[1] is that in that 82 seconds a target moving at even just 25 knots will travel a bit over a kilometer. It wouldn't take much target evasion to make even radar spotting at that range too laggy for unguided projectiles to have much of a probability of hit. (And guided artillery shells are still decades off from Midway, and would have less steering authority anyway in the reduced atmospheric pressure you're calling for)

So at some point extending the range of your ship's guns isn't worthwhile against targets that can maneuver.


--------------------------------
[1] With more gravity and less air pressure you'd need a fairly large blimp or balloon to carry a WWII radar set - and the ability to transmit the radar's plan-form plot back to a surface ship wasn't available until almost the end of the war[2] so the blimp would likely need someone determining the MPI and error and transmitting that by voice down to each battleship.

[2] Look up Project Cadillac - basically using a TV camera to transmit the picture of an airborne radar's screen back to a carrier's fighter direction department.

Large ships moving at speed are not exactly highly maneuverable.

kzt wrote:Large ships moving at speed are not exactly highly maneuverable.

But in this scenario you've got a km and the better part of 3 [correction: 1.5] minutes to play with. Deflecting your course just 5 degrees to the side offsets you roughly 90 meters from your original expected location. That's almost enough to slide entirely out from under a pattern well aimed at your original course.

At those really long ranges and relatively lengthy flight times you don't need to dodge much to get away from your projected future position. Of course the solution is obvious and straightforward - if you can't get hits at extended ranges move closer.

82 seconds isn’t nearly 3 minutes where I live.

But sure, long range fire is always a matter of probability. You roll enough dice you eventually get lucky. Hopefully before they do.

Jonathan_S wrote:

kzt wrote:Large ships moving at speed are not exactly highly maneuverable.

But in this scenario you've got a km and the better part of 3 [correction: 1.5] minutes to play with. Deflecting your course just 5 degrees to the side offsets you roughly 90 meters from your original expected location. That's almost enough to slide entirely out from under a pattern well aimed at your original course.

At those really long ranges and relatively lengthy flight times you don't need to dodge much to get away from your projected future position. Of course the solution is obvious and straightforward - if you can't get hits at extended ranges move closer.

Actually, 90 meters is not nearly enough to slide you out from under a well-aimed pattern. The spread on a salvo of eight or nine 16" guns is significant. It is true that moving 90 meters from the center point of the salvo will almost certainly decrease the possible number of hits you will receive; it will not get you outside the dispersion zone of the salvo. Indeed, the USN observed that dispersion actually increased the "danger zone" of its salvos at extreme range. There's also the fact, as someone else mentioned, that large vessels do not alter course-- even by 5 degree increments --- with whirlwind speed. And, finally, that's one of the things the rate change calculator in a fire control system is designed to work with in order to predict where a ship is headed so the shells can arrive at the same point.

Would the fire be a whole bunch more accurate and deadly at lower ranges with less flight time for the shells? Sure it would. It wouldn't be unworkable, by any stretch of the imagination, at the ranges specified and with the spotting specified. Probably waste a lot of ammo without hitting anything, but the extremely steep angle of descent on the shells would mean that any hit you did score would have an excellent probability of inflicting decisive damage to engineering or other systems protected below the armored deck.

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%.