Chinese Supergun?

3

313230

New Member
Wow, very well informed post. From long time, I felt that gun is more efficient than rocket like exactly what you said, but can get any source to confirm

Here is a link states typical energy consumed in small fire arm (I followed it from wiki)
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Mechanical energy
Projectile motion 32%
Barrel friction 2%

Thermal energy
Hot gases 34%
Barrel heat 30%

Chemical energy
Unburned propellant 1%

It is for small arm, so for large caliber cannon, there are some differences:
The friction may come up since contact area may up with power of 2 compare to bore diameter.
The propellant of large gun often is slow burnt, while in small arm it often burns very fast. This may increase efficiency.

Otherwise, it seems friction loss is low and heat loss is the most. If the barrel can be isolated, i.e by a thin layer of thermal isolating material, then wonder how thing will go?

Since this topic is about long range delivery system, it seems the most efficient way for delivery long range pay load is cruise missile.
It is air breath so less weight of propellant.
It can use fuel which is very energy density (I don't know how dense is energy of propellant of gun and rocket compare to petroleum)
And important thing is it travel at low speed so air drag is low.
Cons are expensive air breath engine, low speed is vulnerable to anti air.

Another way is to shoot projectile very high which avoid air drag. This is typical for ballistic missile and maybe supergun? Don't know which method is more efficient, ballistic missile or cruising missile.
 
duskylim

duskylim

Junior Member
VIP Professional
Actually, a large gun will be MORE efficient that a smaller one (again, up to a point).

This is because of the Surface Area to Volume ratio relationship.

The surface area of a projectile (area of contact with the gun barrel, which produces the friction) increases with the Square of the projectile's diameter.

The volume of the projectile (and hence the weight it delivers to the target) increases with the Cube of the projectile's diameter.

So if you double the diameter of the projectile, the frictional area increases by four times (4x), but the volume (or mass) of the projectile increases by a factor of eight (8x).

Example.

If the initial bore was 5 cm (~2 inches) the area is proportional to 5^2 or 25 (A1), and the volume as 5^3 or 125 (V1).

If we double the bore to 10 cm (~4 inches) the area is proportional to 10^2 or 100 (A2) and the volume to 10^3 or 1000 (V2).

Now A2 / A1 = 100 / 25 = 4 times the original area.

But V2 / V1 = 1000 / 125 = 8 times the original volume.

Note V1 / A1 = 125 / 5 = 5 units of volume per unit of area.

But V2 / A2 = 1000 / 100 = 10 units of volume per unit of area.

So the second gun can deliver twice the projectile mass (firepower) per unit of frictional area.

Of course, there is the issue of bursting strength of the barrel which is always greater for a larger caliber gun.

This means the larger gun's weight goes up faster than in simple volume ratio comparisons.

As to the propellant burn rates, both the small caliber guns (small arms) and large caliber guns (artillery) try to utilize slow-burning powders, as these reduce the shock load on firing the weapon.

Too fast a burn rate will tend to destroy the weapon as the shock load comes like a hammer blow on firing.

Indeed, in machine design, the sections needed to resist shock loading are all out of proportion compared to those needed to resist more gentle applications of the load.

This will tend to create very large, bulky and heavy weapons, which will neither be cheap nor mobile.

Fast burning also means faster heat produced during a given time, resulting in very high temperatures that are detrimental to gun life.

Slow burning also reduces peak pressures (the source of shock loading) which are very high in fast burning powders.

As to the issue of thermal insulation, it is mainly used in weapons like tank guns (where it is called a 'thermal sleeve'), and is used so that the barrel heats up uniformly and does not bend, which gravely compromises accuracy.

This distortion is the result of uneven cooling of the barrel - say from a cold wind in winter blowing on one side.

It is not used to increase the thermal efficiency of the weapon, as rapid, repeated firing causes the gun to heat up - sometimes to red heat.

Since the Second World War, it has become common for larger caliber guns to have a replaceable 'sleeve' or 'liner' inside the main gun tubes, when the specified number of rounds have been fired, the worn liner is replaced by a new one, rather than having to scrap the whole barrel.

The Germans took this idea a step further, dividing the gun's liner into several parts, the 1st 'commencement of rifling' from the chamber to about a third of the barrel length and the 2nd main liner. This first part wore out the most and was replaced most frequently.

They also used variable twist rifling, slow pitch at first, progressively faster pitch further on, but I digress.

So back to thermal insulation of the gun barrel.

In fact the opposite is done in naval weapons like the Creusot-Loire Compact 100mm gun, where the gun is water-cooled (not insulated!) and air-purged after every shot, and is capable of firing up to 90 rounds per minute!

Musing about theoretical weapons, I would use a low-pressure gun to accelerate a rocket-powered jet to about 100 meters per second, whereupon a rocket motor would ignite, powering a hybrid rocket-jet engine.

Hah! I have to say to myself - Dream on.
 
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3

313230

New Member
duskylim said:
Actually, a large gun will be MORE efficient that a smaller one (again, up to a point).

This is because of the Surface Area to Volume ratio relationship.

The surface area of a projectile (area of contact with the gun barrel, which produces the friction) increases with the Square of the projectile's diameter.

The volume of the projectile (and hence the weight it delivers to the target) increases with the Cube of the projectile's diameter.

So if you double the diameter of the projectile, the frictional area increases by four times (4x), but the volume (or mass) of the projectile increases by a factor of eight (8x).

Example.

If the initial bore was 5 cm (~2 inches) the area is proportional to 5^2 or 25 (A1), and the volume as 5^3 or 125 (V1).

If we double the bore to 10 cm (~4 inches) the area is proportional to 10^2 or 100 (A2) and the volume to 10^3 or 1000 (V2).

Now A2 / A1 = 100 / 25 = 4 times the original area.

But V2 / V1 = 1000 / 125 = 8 times the original volume.

Note V1 / A1 = 125 / 5 = 5 units of volume per unit of area.

But V2 / A2 = 1000 / 100 = 10 units of volume per unit of area.

So the second gun can deliver twice the projectile mass (firepower) per unit of frictional area.

Of course, there is the issue of bursting strength of the barrel which is always greater for a larger caliber gun.

This means the larger gun's weight goes up faster than in simple volume ratio comparisons.
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While I knew what you mean, I didn't get it. There are several problems:
1/ Increasing diameter increases squared friction and cubed volume for projectile. But the base area of the projectile is only squared, so if peak pressure is the same, the pushing force per base area is the same, and the pushing force per mass is reduced, it means reduced muzzle velocity.
In short: one unit of diameter -> a squared unit of area (both contact area and base area) -> squared pushing force and squared friction - > pushing force per friction is the same (assume the same peak pressure). So not better efficiency

2/ As diameter increase, the thickness of the barrel is increased, given the same peak pressure and steel strength.

E.g small arm works at a little smaller peak pressure than cannon but its barrel thickness is very small compare to say 120mm gun. IMO it is because the diameter increases the internal area per length, which make the force tearing the barrel apart increased, and so needs thicker barrel to cope with.

One unit of increased diameter leads to one unit of area (per length) -> one unit of force -> one unity of thickness of barrel for the same barrel yield strength.
As to the propellant burn rates, both the small caliber guns (small arms) and large caliber guns (artillery) try to utilize slow-burning powders, as these reduce the shock load on firing the weapon.

Too fast a burn rate will tend to destroy the weapon as the shock load comes like a hammer blow on firing.

Indeed, in machine design, the sections needed to resist shock loading are all out of proportion compared to those needed to resist more gentle applications of the load.

This will tend to create very large, bulky and heavy weapons, which will neither be cheap nor mobile.

Fast burning also means faster heat produced during a given time, resulting in very high temperatures that are detrimental to gun life.

Slow burning also reduces peak pressures (the source of shock loading) which are very high in fast burning powders.
Click to expand...
I understand that the distance to accelerate projectile inside small arm is so small, e.g 10cm for pistol, 50cm for rifle, but very long for large caliber gun, e.g 8m for 52cal 155mm. Assume they achieve similar muzzle velocity, e.g 950mps, the rifle needs to done this on the 50cm distance while big gun has 8m so acceleration is (guessed) ten times smaller on big gun which mean slowly burnt rate is allowed.
As to the issue of thermal insulation, it is mainly used in weapons like tank guns (where it is called a 'thermal sleeve'), and is used so that the barrel heats up uniformly and does not bend, which gravely compromises accuracy.

This distortion is the result of uneven cooling of the barrel - say from a cold wind in winter blowing on one side.

It is not used to increase the thermal efficiency of the weapon, as rapid, repeated firing causes the gun to heat up - sometimes to red heat.

Since the Second World War, it has become common for larger caliber guns to have a replaceable 'sleeve' or 'liner' inside the main gun tubes, when the specified number of rounds have been fired, the worn liner is replaced by a new one, rather than having to scrap the whole barrel.

The Germans took this idea a step further, dividing the gun's liner into several parts, the 1st 'commencement of rifling' from the chamber to about a third of the barrel length and the 2nd main liner. This first part wore out the most and was replaced most frequently.

They also used variable twist rifling, slow pitch at first, progressively faster pitch further on, but I digress.

So back to thermal insulation of the gun barrel.

In fact the opposite is done in naval weapons like the Creusot-Loire Compact 100mm gun, where the gun is water-cooled (not insulated!) and air-purged after every shot, and is capable of firing up to 90 rounds per minute!

Musing about theoretical weapons, I would use a low-pressure gun to accelerate a rocket-powered jet to about 100 meters per second, whereupon a rocket motor would ignite, powering a hybrid rocket-jet engine.

Hah! I have to say to myself - Dream on.
Click to expand...
Thanks for the infos

What is hybrid rocket jet? What advantages does it bring over pure rocket or jet?

And what is the point of accelerate a rocket jet to about 100 meter per second? If you want to use rocket why didn't add a booster which then doesn't require a gun? And if it needs a gun then ramjet is more efficient as it doesn't need to carry oxidant?

About water cooler, I did some search and could not find out how it works. How do they pump water into barrel? Is chamber closed and sealed while water is pumped in? And then when loading the next round, chamber needs to open, isn't that making the water splits all over internal turret?
 
D

delft

Brigadier
OT
Penetrator rods made from tungsten or depleted uranium are fired by tank guns - armor piercing fin stabilized discarding sabot. They have a smaller mass than a full caliber shell, do not engage in rifling and so have a lower friction. They have a muzzle velocity above 1600 m/s, while ordinary shells stay below 1000 m/s. Mounting a tank gun in a howitzer type mount would give a pretty high range. The German railway smooth bore gun of 310 mm fired a similar projectile over 100 km. With a rocket boost the range became 160 km. This weapon was of little use at the end of WWII with a depleted Luftwaffe. Similar weapons were proposed in the '70's ( IIRC ) possibly using liquid fuel and reaching a muzzle velocity of 1800 to 2000 m/s. I think we'll never see them. They will be superseded by rail guns without ever having reached service.
 
C

chuck731

Banned Idiot
duskylim said:
Actually, a large gun will be MORE efficient that a smaller one (again, up to a point)..
Click to expand...

I think you are forgetting the same square vs cube law also makes a proporationally larger gun barrel structurally weaker and less efficient than a proportionally smaller gun barrel. The hoop strength of a gun barrel represents the ability of a barrel to resist bursting under the pressure of the propellant charge. It seems to me the hoop strength in turn increases in proportion to the square of the dimension of the gun barrel.

But the power of the prepellant charge, on the other hand, goes up in proportion to the cube of the dimension of the gun.

So all else being the same, a super gun barrel would need to be proportionally much heavier and thicker walled than a smaller gun in order to have the same resistance to bursting upon firing.
 
duskylim

duskylim

Junior Member
VIP Professional
Dear Charlie:

I am well aware of the role hoop tension plays as it is one of the calculations I perform regularly when determining pressure vessels' strengths.

That is why I qualified my statement with "Of course, there is the issue of bursting strength of the barrel which is always greater for a larger caliber gun. This means the larger gun's weight goes up faster than in simple volume ratio comparisons."

The key to clarifying this issue is defining what we mean by 'efficiency'.

On my earlier posts I considered a weapon's 'efficiency' to mean delivering the largest payload over a given range using the least propellant.

This was because I looked at them from a thermodynamic point of view - i.e. as heat engines converting the propellant's chemical energy into the projectiles kinetic energy.

I did not examine them from the other points of view - as this was not my purpose.

It is not clear to me what your definition of 'efficiency' is.

But from my point of view, the mass of the resultant gun is not relevant to it's thermodynamic efficiency.
 
S

Skywatcher

Captain
Well, the US Army's graphic for that 1,600km range Strategic Strike Cannon shows two tracked vehicles, the cannon itself and what is presumably an ammo carrier.

Though I suspect that the SSCA or its Chinese counterpart would probably be happy with a 500km-700km range.

And this is where the Strategic Strike Artillery Cannon would come into the picture. The INF does not cover such weapons, regardless of their range.
A cannon firing a chemically or electro-magnetically propelled round nearly 1,000 miles away could offer a way to strike targets well within denied areas, but in a way that is clearly compliant with the INF. The Army would actually have a surprisingly deep knowledge base to draw from in this regard, too. The service captured examples of the lesser known Nazi “vengeance weapons,” the V-3 long range gun, during World War II and extensive evaluated them afterwards.
Then, during the 1960s, the United States and Canada teamed up on the High Altitude Research Project, or HARP, which used modified 16-inch naval guns from fixed sites on land to explore the possibility of the system as a cost-effective means of launching objects into space. Though that weapon set an attitude record for a gun-launched projectile, it was only 110 miles.

It could serve as a good starting place for a larger “supergun,” though. The HARP gun’s designer, Gerald Bull, definitely thought so, shopping the idea of an ultra-long-range artillery weapon around the world after the project ended due to steadily improving rocket boosters and a loss of interest on the part of both the American and Canadian governments.

Infamously, Bull finally pitched an improved concept to Iraqi dictator Saddam Hussein in the 1980s. The Babylon Gun’s design was supposed to offer a range of more than 450 miles, which would have put targets within Iran and Israel in strike distance.

The final weapon never came to fruition though. Assassins, alternately linked to Israel’s Mossad or Iran’s VEVAK, killed Bull in the Belgian capital Brussels in 1990. British customs also seized components for the weapon before they could reach Iraq and the project came to a complete halt after the United States-led intervention to liberate Kuwait and beat back Iraqi forces in 1991.

Bull’s concept for a multi-chamber artillery piece would still likely be one of the best chances for the Army to achieve the ranges it’s looking for with a gun system. The V-3 used a similar mechanism, with the Nazis referring to its multiple sections as a “high pressure pump” to cover its true function.
These types of designs work by propelling a shell with multiple explosive charges. Combined with a long barrel, this method gradually builds up pressure behind the projectile just like a rocket, which extends range and reduces wear and tear on the system at the same time.
Another option would be to pursue a larger railgun that might offer similar range. The conceptual design of the Army’s 32 mega joule electro-magnetic gun already requires two separate vehicles to carry the necessary power source and offers a maximum range of around 100 miles. A system with 10 times that range could have immense power requirements.

It’s questionable how mobile either a chemical supergun or a massive railgun might be at all, though. Historically, plans for super guns have called for them to be fixed in place, aimed broadly in the direction of a large target, such as a city, intended to cause terror and chaos rather that than more specific strategic effects. The World War I-era Paris Gun could traverse 360 degrees, but was still effectively immobile, as were the guns the Germans and the British used to shell each other across the English Channel during World War II.

The Strategic Strike Artillery Cannon might not need to move though. A fixed and properly hardened position could be able to hold a wide area at risk, which could deny an enemy freedom of movement through a large area.

This could be useful for trying to close of access to certain areas in a potential European conflict, especially in constrained multi-domain environments, such as the Baltic Sea or Black Sea. In those cases, various long range artillery weapons could work to neutralize anti-ship threats, as well as anti-aircraft ones, too.
By the strategic weapons, missiles or guns, might actually be better suited to the Pacific theater, where being able to deploy them with any rapidity to small island outposts could easily present a significant challenge to other potential opponents, such as China or North Korea. These weapons would have the range to engage targets in North Korea from distributed sites in South Korea and Japan or various Chinese outposts in the South China Sea from territory belonging to allied or partner nations, such as The Philippines or Vietnam. If they were capable of firing hypersonic projectiles, the weapons in those positions would be even more effective, able to take on time-sensitive targets or otherwise launch strikes with little advance warning.

This “an anti-access, area-denial capability all of our own to make potential adversaries think twice,” Brigadier General Maranian explained. They would “be deterred before making a decision of whether cost is worth the benefit of being provocative.”

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Click to expand...

Might use even more exotic propellant scheme, like some sort of gas combustion, a coilgun, electrical thermal chemical (sp) or a hybrid of those.

And wasn't there some Chinese patent for a railgun that drew its electricity from the propellant charge of its ammunition (would be good for mobile land artillery, though it probably creates more tradeoffs on something with a guaranteed power supply, like a warship)?
 
S

Skywatcher

Captain
If a ramjet 155mm shell like that NAMMO proposal can reach out to 100 km, then a 280 mm ramjet shell could have a range of 500-600 km.
 
D

Deleted member 13312

Guest
Skywatcher said:
If a ramjet 155mm shell like that NAMMO proposal can reach out to 100 km, then a 280 mm ramjet shell could have a range of 500-600 km.
Click to expand...
That may be true, but you are also increasing the diameter and weight of the shell in question. Which would lead to a slower rate of fire and less ammo carried. Plus the gun barrel needed to fire a shell of such a caliber would have to be enormous in portions to support the blast pressure of the initial firing.
What that really matters would be the amount of propellant used in the shell, a 155mm shell with more propellant can reach longer ranges than a traditional 155mm shell.
 
S

Skywatcher

Captain
Viktor Jav said:
That may be true, but you are also increasing the diameter and weight of the shell in question. Which would lead to a slower rate of fire and less ammo carried. Plus the gun barrel needed to fire a shell of such a caliber would have to be enormous in portions to support the blast pressure of the initial firing.
What that really matters would be the amount of propellant used in the shell, a 155mm shell with more propellant can reach longer ranges than a traditional 155mm shell.
Click to expand...
Yes, but with a large ramjet cannon, you'd be looking at something like Atomic Annie, which was pretty darn mobile.

A vertical gun could be fired at a decent rate ( come to think of it, if a 127mm vertical gun with unpowered shells could achieve a range of 180 km, a 203mm ramjet shell could probably do 400-600 km).
 
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