GarryB Mon Dec 25, 2023 7:30 pm
There are several ways of improving range performance, the most common is increasing muzzle velocity, but that means nothing if you don't also optimise the shape and weight of your projectile.
If you look at the shape of a cannon ball you will see it is very much not aerodynamic and is designed to roll down a barrel easily for loading.
To improve aerodynamics you make the projectile bullet shaped, so if it is supersonic then a pointy nose helps it cut through the air but a short stumpy bullet makes the projectile light for its calibre which means it has less momentum to push through the air.
The most aerodynamic shapes are long and thin like a Javelin (the sporting equipment, not the missile), where its narrow diameter means low drag as long as it is moving point forward and its length gives it mass to push through the air efficiently without slowing down very much.
The opposite of that is an inflated balloon.... it is very light so if you throw it it accelerates quickly but when you release it it does not push the air in front of it aside very well because it is big and draggy and has very little mass so while you can get it up to high speed it rapidly loses speed when you release it because its huge surface area has to displace a lot of air for it to move and it has very little weight to do so.
Early rifle bullets had round noses and flat bases, but pretty quickly they went to pointed bullets or spire point bullets and what are called boat tails where the rear end of the bullet gets narrower and then as a flat base that is narrower than the full width of the projectile.
The pointy nose helps it cut through the air at supersonic speed and the boat tail massively reduces drag once the projectile is subsonic.
Your standard rifle bullet like the 5.45mm leaves a barrel at almost mach 3 but by the time it has travelled 7 or 800m it is subsonic.
Older 30 calibre rifle bullets had a similar problem and when the 303 went from a flat tailed bullet to a boat tailed bullet the increase in performance was impressive.
With a flat based bullet the ballistic range of the bullet was about 2km. With a boat tailed bullet it is about 4 to 5km.
Regarding this new artillery shell making the projectile more aerodynamic allows it to maintain a higher velocity which dramatically increases flight range.
By being low drag if a projectile can maintain a higher flight speed it will travel further and they also use all sorts of tricks to do that as well.
One is rocket assisted where they put a rocket motor in the base of the round to accelerate the projectile after it as left the barrel of the gun.
Base bleed is like a very low energy rocket in the base of a shell that does not accelerate the round in flight... what it does is fill the air pocket behind the round in flight, which essentially reduces its drag to near zero so it maintains its flight speed for longer.
The more speed you keep the more energy you retain the further you travel.
If you have held you hand out of a car window while the car is moving you will know it is strong in the suburbs where you are going 50km/h, but on the motorway the force is much much stronger and it is hard to hold your hand in that airflow.
It keeps getting worse the faster you go, so a supersonic projectile has an enormous force of wind blowing on it so being a slim aerodynamic shape lets you cut through the wind minimising the force of the air you are travelling through to slow you down.
How does Coalitia reach so far?
A longer barrel gives the projectile more time to accelerate to a higher speed.
An optimised shell shape and design will also maximise its range, so low drag, as well as perhaps a reduced weight to allow it to accelerate to a higher speed in the barrel of the gun.
I would also suspect the propellent being used is designed to reach peak pressure rapidly if not immediately which means the projectile accelerates as quickly as it can along the length of the barrel... meaning it reaches top possible speed when it exits the barrel.
They were talking about extending range even further to 180km, but I suspect that might be using ramjet assistance, or perhaps a reduced calibre low drag design that is like a fat APFSDS round but instead of being a solid metal dart designed to penetrate armour it would be a longer thinner projectile with HE.
So with a 152mm shell it might be an 80mm calibre dart that is twice as long as a 152mm HE shell that might have 30kgs of HE and fragments instead of 50kg of HE and fragments... an 80mm shell would be much lower drag in flight than a 152mm shell so it will retain speed much better and therefore land further away.
Previously that was pointless because the extra range would be too inaccurate to be useful for anything at all but with every shell with some sort of guidance getting it into a 5-15m circle of where you are aiming then that is no longer a problem.
Obviously an 80mm calibre round could have a 20mm tube around it (total diameter 120mm... 20+80+20) that could be a ramjet strapped around the core HE projectile with its guidance etc, and you could fill the rear portion of the outer tube with solid rocket fuel and ramjet fuel so you fire it and it fires its rocket fuel to accelerate after it leaves the gun barrel and then the nose fairing falls away when the solid rocket fuel is burned out and air gets sucked into the nose intakes and compressed and liquid fuel is burned with the air going into the air intake to accelerate the projectile for a 30 or 40 second period of time or so and then the outer case could fall away leaving the core to continue with reduced drag to the target area.
It is something they can already do with their missiles like the SA-6 and Kh-31 and Moskit and Onyx and Zircon (except the ramjet falling away of course).
Make it a ramjet and even old 152mm guns will have long range reach... scramjet powered shells could have enormous range and I hope they develop them for 152mm and perhaps 203mm new artillery guns for the Navy and the Army.
The west talks about defeating air defences with swarms but actually putting that into practise is hard because to be a swarm you need numbers and to get numbers they need to be small and cheap which makes long range and high speed a problem.
A 152mm gun firing 16 rounds a minute in the land based model and perhaps 90 rounds per minute in a naval version would be an excellent way of building up a swarm attack on naval targets... even a ramjet powered shell could be relatively cheap... ramjets are simple and the guidance component is relatively cheap cellphone level technology these days too.
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