PRC/PLAN Laser and Rail Gun Development Thread

[taxiya]

I have no idea how people are becoming SO sure that this barrel is rectangular. The jury is definitely still out on this IMO. The way the tarp drapes over the barrel so loosely prevents its cross-sectional shape from being identified with any degree of certainty at this juncture.

It is from this photo that exposes the barrel. Marked by the red line, the front half is not circular.

 

[taxiya]

I'm not a fanboy, just someone who likes to dig into the maths.

My argument was that the volume of the fuel needed to be turned into kinetic energy for the rail gun is less than the conventional propellant charge, thus rail gun space savings for the propellant.

I am not sure of this assumption.

1. If the same amount of kinetic energy is needed, it will need same amount of fuel minus the conversion waste, it can not need less.
2. The conventional warhead carries explosives which is also energy that will create damage. For a EM shell (without explosives for the moment) to create the same damage, it must possess extra amount of KE (equal to the explosive energy in the explosive shell). Put this extra demand, the equivalent EM shell will need to possess far higher KE than conventional shell.
3. The waste of the energy through the systems include, friction of the shells when traveling through the rails, barrels and air. While EM shell is small, it is much faster (air friction grows on the order of speed^2?), its waste is not necessarily less than conventional shells, probably higher (Mach 7 vs Mach 2).

The total energy consumption of EM shell may not be any less than a conventional shell for the same distance and same damage on the same target. This is law of conservation of energy.

 

[kurutoga]

I am not sure of this assumption.

1. If the same amount of kinetic energy is needed, it will need same amount of fuel minus the conversion waste, it can not need less.
2. The conventional warhead carries explosives which is also energy that will create damage. For a EM shell (without explosives for the moment) to create the same damage, it must possess extra amount of KE (equal to the explosive energy in the explosive shell). Put this extra demand, the equivalent EM shell will need to possess far higher KE than conventional shell.
3. The waste of the energy through the systems include, friction of the shells when traveling through the rails, barrels and air. While EM shell is small, it is much faster (air friction grows on the order of speed^2?), its waste is not necessarily less than conventional shells, probably higher (Mach 7 vs Mach 2).

The total energy consumption of EM shell may not be any less than a conventional shell for the same distance and same damage on the same target. This is law of conservation of energy.

• His estimate is pretty good, when you consider the volume needed for an AGS shell, you need to consider the cartridge too. The volume will be something like a cylinder with r=10cm, length=100cm, do a pi * r * r * length you will reach the same number.
• Some recent documents showed the EMRG projectile can be highly sophisticated, including but not limited to:
  • steel slug, for mindless bombardment
  • solid metal slug made from some sort of reactive metal materials, anti-material mindless bombardment
  • artillery shell-like, with explosives inside, mindless bombardment with chemical energy
  • guided shell (including explosives, GPS and/or laser guidance), stationary targets
  • rocket propelled guided shell w/ missile like guidance heads, moving targets
• He was pretty generous with the wasted energy in the EM process

 

[taxiya]

his estimate is pretty good, when you consider the volume needed for an AGS shell, you need to consider the cartridge too. The volume will be something like a cylinder with r=10cm, length=100cm, do a pi * r * r * length you will reach the same number.

I have taken the propellant energy in the cartridge into the consideration. I will read his post again though. However, any saving of EM is the work on eliminating the wasted energy, energy itself does not disappear or come out of nowhere, it remains constant.

Edit: after reading his post in details, here are something that should not have been excluded in that post 384.

BAE 32 MJ uses 12L of fuel per shot (electricity converted from turbine engine)while a conventional AGS artillery has a propellant charge that takes up 32 L of volume. Making the rail gun more space efficient, this is independent of the warhead, just the propellant equivalent volume. In addition the fuel consumed would amount $12 per shot where as the conventional gun's propellants would cost hundreds of dollars per shot.

1. The explosive charges in conventional shell which transferred to damage on the target. This part of energy is in the form of KE in EM shell which takes up volume of fuel.
2. Although EM gun eliminated cartridge, it adds storage system which is a commercial container size in both the Chinese and US implementation. This is no smaller than a magazine of conventional gun.

We can not make the calculation favoring our own preference by ignoring their shortcomings.

 

[kurutoga]

I have taken the propellant energy in the cartridge into the consideration. I will read his post again though. However, any saving of EM is the work on eliminating the wasted energy, energy itself does not disappear or come out of nowhere, it remains constant.

Edit: after reading his post in details, here are something that should not have been excluded in that post.

1. The explosive charges in conventional shell which transferred to damage on the target. This part of energy is in the form of KE in EM shell which takes up volume of fuel.
2. Although EM gun eliminated cartridge, it adds storage system which is a commercial container size in both the Chinese and US implementation. This is no smaller than a magazine of conventional gun.

We can not make the calculation favoring our own preference by ignoring their shortcomings.

The analysis is based on comparison of volume.

 

[taxiya]

The analysis is based on comparison of volume.

therefor the volume of the storage system needs to be taken in, which takes the place of cartridge. My point is that calculation excluding some critical factors is misleading and meaningless.

To make myself clear, I am not criticizing @SilentObserver for his effort. He did a very god detailed calculation. But IMO, the calculation missed or excluded something that can not be excluded.

 

[kurutoga]

therefor the volume of the storage system needs to be taken in, which takes the place of cartridge. My point is that calculation excluding some critical factors is misleading and meaningless.

I am at a loss what you are trying to say. If by storage you are referring to the EMRG hardware, say, the capacitor bank/flywheel and the generators, then to do the comparison we need good idea of the size/weight of the traditional naval gun (such as AGS) too.

You assume the EMRG gun system takes more space? That is certainly not correct. It varies from ship to ship, from implementation to implementation. On DDG-1000, for example, the ship contains full IEP as well as the power distribution and control system, plus maybe some sort of energy storage solution. An EMRG gun would be a smaller add-on while an AGS gun will cause extra penalties. On a ship without IEP, adding an EMRG gun will require dedicated generators, and take extra penalties.

Unless someone put in the effort to make a comprehensive examination of the cost/effectiveness at system level of a (1) 2030 IEP+EMRG+Laser warship (2) 1980s AB (3) WW2 era battleship, of course more meaningful results can be obtained. That is a Ph.D thesis, not a quick discussion

 

[taxiya]

I am at a loss what you are trying to say. If by storage you are referring to the EMRG hardware, say, the capacitor bank/flywheel and the generators, then to do the comparison we need good idea of the size/weight of the traditional naval gun (such as AGS) too.

You assume the EMRG gun system takes more space? That is certainly not correct. It varies from ship to ship, from implementation to implementation. On DDG-1000, for example, the ship contains full IEP as well as the power distribution and control system, plus maybe some sort of energy storage solution. An EMRG gun would be a smaller add-on while an AGS gun will cause extra penalties. On a ship without IEP, adding an EMRG gun will require additional generators, and take extra penalties.

Unless someone put in the effort to make a comprehensive examination of the cost/effectiveness at system level of a (1) 2030 IEP+EMRG+Laser warship (2) 1980s AB (3) WW2 era battleship, of course more meaningful results can be obtained. That is a Ph.D thesis, not a quick discussion

By storage I meant the capacitor banks dedicated to the gun system excluding the generators. The generators are part of the overall IEPS which will take up the space with or without the EM gun, although adding EM gun will likely demand extra power (the constant charging) output which leads the generators bigger.

No, I did not necessarily assume the EM gun takes more space. But only disagree with the assumption that it takes less space..

Indeed, the overall analysis will be beyond our knowledge, therefor I was trying to remind everyone not to rash to the conclusion of EM gun being always the better choice.

And more importantly, only that comprehensive study is meaningful for the application of EM gun.

 

[Jura The idiot]

this part:

Just a note on muzzle energy, what matters isn’t kinetic energy of the projectile when exiting the muzzle but the kinetic energy of the projectile when hitting the target. If the projectile bleeds energy as it travels the kinetic energy hitting the target is going to be less than the muzzle energy. I don’t know this as fact but I’m going to guess that a railgun projectile might bleed less energy than a round from a Mark 7 battleship gun.

somehow addressed
Thursday at 10:02 AM

in the example Today at 7:30 AM
a striking velocity of 514 m/s is for a muzzle velocity of 762 m/s (the link is

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)
so 1225 kg weighing AP Mk8 shell would loose
(0.5*1225*762^2-0.5*1225*514^2)/(0.5*1225*762^2)
about 55%, but still had the energy (of 162 MJ) several times higher then the current (32 MJ) US railgun they were considering to ax anyway Dec 7, 2017
LOL but maybe the Pentagon will now start pumping money into railguns

now this part:

If the projectile is delivering an explosive payload then the muzzle energy is trivial relative to the actual kinetic energy of the payload itself.

an AP Mk8 shell from that example had 1.5% of Explosive D (according to Campbell's Naval Weapons of WW2),
and I didn't find its TNT equivalent, so assuming there were 18 kg "of TNT" inside, it'd mean about 75 MJ released (

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);
so the kinetic energy of said shell hitting as in that example, about 162 MJ, would be actually higher than of the burster

(LOL I don't try to spin anything, of course I know high-capacity 16" shells had bigger bursting charges, just wanted to finish here using the example originally from Aug 26, 2017)

the point? I'm still wondering

what extent AND type of the damage do you expect to be inflicted upon a modern (=unarmored) warship by a single hit off a 32 OR 64 MJ railgun (presumably shooting around-5"-caliber metal rods)?

I now checked the kinetic energy of a hit by Mk 7 16" at its max. range had been

0.5*1225*514^2 (don't nitpick if I didn't read out at navweaps.com the striking speed correctly, if it's incorrectly quoted there, or anything)

which is about 162 MJ; I don't try to mix apples with oranges: the main point of hitting by a 16" shell of course wasn't its kinetic energy, but the main point was to deliver several tens of pounds of an explosive under the deck of an enemy ship, and blow up said explosive there (actually if the fuze wasn't set off, the damage made by a large-caliber shells wasn't much worse than just holes in the bottom, as it had been happening in the action of the Yamato against the Gambier Bay, an unarmored escort carrier)

 

[Figaro]

2011 December, a satellite photo showed 2 large guns, placed horizontal in a desert near Baotou in China. In front of the guns were square target blocks which are just tens of metres away from the gun. So it is possible these are the land based rail gun tests that was carried out 6 or 7 years ago?


Credits to @Icloo on PDF